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31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
1
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
2
TUESDAY 10th SEPTEMBER
08:00 Sunrise Session - Fundamentals, David Grills and Matt Bird
09:00
09:35
10:00
10:35
Fundamentals-I Session (pulsed) Chair - David Grills
I1: “Time-Resolved Resonance Raman Studies of Pulse Radiolytic Reactions”
Ireneusz Janik
I2: “Partial Molar Volume of the Hydrated Electron and a Comment on Its
Vertical Detachment Energy” Dave Bartels
P1: “Chemical Dosimetry of Femtosecond Electron Bunches Provided by Laser-
Plasma Acceleration” Gerald Baldacchino
P2: “Femtosecond Resolution for Picosecond Radiolysis Using Electron Pump-
Repump-Probe Spectroscopy” Sergey Denisov
11:00 Coffee
11:20
11:55
12:30
12:55
Fundamentals-II Session (other) Chair - Jim Wishart
I3: “Simulation of Radiation Damage Processes” Andrey Solov’yov
I4: “Mimicking Oxidative Stress by Radiation Biochemistry. Addition of Free
Radicals to a Free Radical Producer: NADPH Oxidase” Chantal Houée-Levin
P3: “Molecular Simulations of the Oxidative Radiolysis of two Inverse Peptides:
Methionine Valine and Valine Methionine” Pierre Archirel
P4: “Comprehensive Model for X-Ray Induced Damage in Protein
Crystallography” David Close
13:20 Free Time
16:30
16:45
17:00
17:15
17:30
17.45
Pre-Poster Talks Session, Chairs Fred Currell and Mats Jonsson
PP1: “Impact of Doping and Functionalisation of Graphene Support on the
Radiolytic Synthesis of Palladium Nanoparticles for Electrocatalysis” Kun Guo
PP2: “Role of Electronic Energy Loss of the Ion Beam in the Modification of
Graphene Oxide Film” Chetna Tyagi
PP3: “Radiation Induced Polymerization of Nanostructured Conducting
Polymers” Teseer Bahry
PP4: “Effect of Surface Deformation on Stress Corrosion Crack Initiation in
Austenitic Stainless Steels in PWR Primary Water” Litao Chang
PP5: “Method of Assessing the Radiation Tolerance of Commercial Strippable
Coatings” Alex Jenkins
PP6: “Studying Nascent Proton-Driven Radiation Chemistry in H2O in Real Time
Using Laser-Based Sources” Mark Coughlan
18:00 Poster Session 1 (even numbers)
19:00 Coaches for Cockermouth
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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I1: Time-Resolved Resonance Raman Studies of Pulse Radiolytic Reactions
I. Janik
Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA
Time resolved Resonance Raman spectroscopy is a powerful structure-sensitive technique for
detection, identification and determination of bond-properties and reactive behavior of short-
lived chemical species in solution. The Notre Dame Radiation Laboratory has been the leading
laboratory worldwide in the application of this novel vibrational spectroscopic technique to the
reaction intermediates produced on pulse radiolysis. The recent innovations in our
experimental setup have been to reduce the overall volume of the solutions on which the
transient Raman studies can be performed, and the improvement on the collection optics that
increased the detection sensitivity by orders of magnitude. These improvements have
facilitated the Raman observation of weakly absorbing reaction intermediates with low
resonance Raman enhancement. Vibrational signatures of a number of key intermediates
absorbing in the range from deep ultraviolet (UV) to visible range have been characterized for
the first time. Measurements of the Raman frequencies, their shifts from the gas-phase to
aqueous solution, and the Raman bandwidths provide an insight into the bond properties of the
radicals and the radical water interactions. Determination of harmonic frequencies and
anharmonicity constants have allowed us to estimate the bond dissociation energies in several
pseudo-diatomic systems. The structural determinations in a few instances have been used to
develop a molecular perspective on the thermochemistry in an aqueous environment for the
first time. In the case of a few negatively charged intermediates vibrational footprint of their
interaction with the hydration cage have been also detected for the first time. Vibrational
studies of a few representative class of reactive intermediates will be presented. In particular,
the UV absorbing species like O2- and CO2
- 1,2 , and the hemi-bonded species, e.g., (SCN)2-,3,4
and also a few OH adducts5 will be discussed in some detail.
References
1. Janik, I. and Tripathi, GNR. (2013) The Nature of the Superoxide Radical Anion in Water, J. Chem.
Phys 139, 014302
2. Janik I., and Tripathi G.N.R. (2016) The nature of CO2- radical anion in water, J. Chem. Phys. 144,
154307
3. Janik, I., Carmichael, I., Tripathi, G.N.R., (2017) Transient Raman spectra, structure and
thermochemistry of the thiocyanate dimer radical anion in water, J. Chem. Phys., 146, 214305
4. Janik, I., and Tripathi, G.N.R., (2019) The selenocyanate dimer radical anion in water: Transient
Raman spectra, structure, and reaction dynamics, J. Chem. Phys., 150, 094304
5. Janik, I., and Tripathi, G.N.R., (2013) The early events in the OH radical oxidation of dimethyl sulfide in water, J. Chem. Phys. 138, 25.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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I2: Partial Molar Volume of the Hydrated Electron and a Comment on Its
Vertical Detachment Energy
Ireneusz Janik, Alexandra Lisovskaya and David M. Bartels
Notre Dame Radiation Laboratory, Notre Dame University, Notre Dame, Indiana, USA.
The partial molar volume of the hydrated electron was investigated with pulse radiolysis and
transient absorption2 by measuring pressure-dependence of the equilibrium constant for e-aq +
NH4+ H + NH3 . At 2 kbar pressure the equilibrium constant decreases relative to 1 bar
by only 6%. Using tabulated molar volumes for ammonia and ammonium, we have the result
V(e-aq) – V(H) = 11.3 cm3/mol at 25oC, confirming that V(e-aq) is positive and even larger than
the hydrophobic H atom. Assuming the molar volume of H atom is somewhat less than that of
H2, we estimate V(e-aq ) = 26±6 cm3/mol. The positive molar volume is consistent with an
electron that exists largely in a small solvent void, ruling out a recent controversial model of
Larsen, Glover and Schwartz3 (LGS) that suggests a non-cavity structure with negative molar
volume. It is suggested that no one-electron pseudopotential model of the hydrated electron is
likely to capture all of the dynamical properties of this species that depend on details of the
wavefunction. A full ab initio MD approach may be necessary.
A recent paper of Luckhaus, et al1 has presented
photoelectron data and analysis of eleven liquid
microjet experiments with various excitation
wavelengths from 3.6 to 5.8 eV to extract a
“genuine” distribution of vertical electron
binding energies for the hydrated electron (Figure
1). The analysis involves correction of the
individual photoelectron energy distributions at
each wavelength for scattering losses in the liquid
before escape into the vacuum. Surprisingly the
distribution reported is bimodal, resembling two
overlapping Gaussians with centers at 3.5 and 4.5
eV. We find the bimodal distribution highly
implausible, as it represents a gross violation of
linear response for the hydrated electron ground
state energy. Rather, we identify a flaw in the
calculation of scattering losses that leads to the
bimodal distribution. The “bottom of the
conduction band” in liquid water has been taken
to be Vo = -1.0 eV relative to the vacuum. In the
scattering model used, electrons with kinetic
energies below 1.0 eV never escape from the
liquid microjet. This assumption is shown to be inconsistent with the data being fitted, and a
more likely number is Vo = -0.1 ± 0.1 eV.
References
1. Luckhaus, D.; Yamamoto, Y. I.; Suzuki, T.; Signorell, R. Genuine Binding Energy of the Hydrated
Electron. Science Advances 2017, 3 (4).
2. Janik, I.; Lisovskaya, A.; Bartels, D. M. Partial Molar Volume of the Hydrated Electron. Journal of Physical Chemistry Letters 2019, 10 (9), 2220-2226.
3. Larsen, R. E.; Glover, W. J.; Schwartz, B. J. Does the Hydrated Electron Occupy a Cavity? Science
2010, 329 (5987), 65-69.
Figure 1. “Genuine” electron Binding
Energy (eBE(g)) distribution reported by
Luckhaus, et al.1 The bimodal
distribution (asterisks) with average of
3.7eV can be decomposed into a pair of
Gaussian functions centered at ca. 3.5
and 4.5 eV.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
5
P1: Chemical Dosimetry of Femtosecond Electron Bunches Provided by
Laser-Plasma Acceleration
Gérard Baldacchino, Houda Kacem, Pierre Forestier-Colleoni, Jean Daniel Ahui, Tiberio
Ceccotti, Sandrine Dobosz Dufrénoy
LIDYL, UMR9222 CEA CNRS, Université Paris-Saclay, 91191 Gif-sur-Yvette, France.
The radiobiological effects of the recent protocol in radiotherapy named FLASH seem to be in
relation with the dose rate effect of µs electron pulses. Actually, it spares healthy tissues and
damages tumor cells in a radiotherapy utilization, which improves the treatment prognostic
compared to conventional radiotherapy [1]. This effect could be enhanced by using a higher
dose rate provided by femtosecond electron pulses generated by laser-plasma accelerator. In
this framework, we have studied the chemical effect associated to electron pulses as short as a
few femtoseconds which are provided by high intensity laser (1018 W/cm2) in interaction with
a gas mixture of 99%H2+1%N2.. In these conditions, we expect to produce ultimate dose rates
of electrons in the range of the TGy/s (ie: 1012 Gy.s-1). Their energy belongs to the range 20-
100 MeV. In order to evaluate the dose rate effect in liquid water by chemical fashion, the
determination of radiolytic yields (G-values) of radicals and molecules such as hydrated
electron, hydroxyl radical and hydrogen
peroxide is mandatory. As G-value is the limit
value at dose = 0 of C/d, we first determined
the doses d by simulation using GEANT4
program and electron counting at every shot.
Then, we have used fluorescence spectroscopy
for measuring sensitively the concentrations C
of the above-mentioned species. Then the
scavenging method using Resazurin and
Ampliflu Red as described in ref [2] gives G-
values determination as depicted in figure 1.
The comparison with G-values obtained under
-rays were performed. We will show that
electrons bunches provided by the UHI100
installation at Saclay [3] have produced a small
dose rate effect because hydrated electron and hydroxyl radical have G-values 0.026 and 0.023
µmol.J-1 respectively. H2O2 one seems increased. It will be discussed as well. As these yields
account for the species escaped from recombination in the spurs, molecules could be then
favored because they are the result of radical-radical reactions.
References
1. Favaudon, V., Fouillade, C., Vozenin, M.C. (2015) Ultra-high dose-rate, "flash" irradiation
minimizes the side effects of radiotherapy. Cancer Radiothérapie. 19, 526-531.
2. Baldacchino, G., Brun, E., Denden, I., Bouhadoun, S., Roux, R., Khodja, H., Sicard-Roselli, C.
(2019) Importance of radiolytic reactions during high‑LET irradiation modalities: LET effect, role of
O2 and radiosensitization by nanoparticles. 10, 1-21.
3. Maitrallain, A., Audet, T.L., Dobosz Dufrénoy, S., Chancé, A., Maynard, G., Lee, P., Mosnier, A.,
Schwindling, J., Delferrière, O., Delerue N, Specka, A., Monot, P., Cros, B. (2018) Transport and
analysis of electron beams from a laser wakefield accelerator in the 100 MeV energy range with a
dedicated magnetic line NIMA: Accelerators, Spectrometers, Detectors and Associated Equipment.
908,159-166.
Figure 1. Resorufin (RN) concentration as a
function of the dose delivered by electron bunches
@ UHI100 installation. Slope at d=0 gives the G-
value of OH, here under N2O bubbling.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
6
P2: Femtosecond Resolution for Picosecond Radiolysis Using Electron
Pump-Repump-Probe Spectroscopy
S.A. Denisov and M. Mostafavi
Laboratory of chemical physics UMR8000/CNRS, Université Paris-Saclay, Orsay, France
For decades electron picosecond radiolysis
set-ups remain workhorses of fast time-
resolved radical chemistry despite presence
of subpicosecond electron accelerators.
The list of systems where later could be
applicable is rather short despite high
efficient doses, due to the effect of the
group velocity mismatch of the electron
and the light in the sample what limits
samples length to sub-mm paths [1].
Meanwhile the concentration (manifested
in optical density) of produced radicals is a
crucial issue for radiolysis studies in sub-
and picosecond regimes.
In our work, the newly implemented
technique of 3 pulse electron pump (5 ps) –
optical repump by laser (110 fs) and probe by
with light (150 fs) on the ELYSE platform
(Université Paris-Saclay, Orsay) will be
discussed in details. This technique
reinforces existing platform by opening new
research fields earlier inaccessible due to
time-resolution issues of electron
accelerator.
The electron solvation mechanism in water and other solvents will be revisited. Along with
that, perspective experiments accessible to three pulse spectroscopy will be discussed,
revealing research fields, e.g., dissociative electron attachment in liquids previously directly
unreachable for existing time-resolved radiolysis experimental set-ups limitations [2-3].
Reference(s) 1. Yang, J.; Kan, K.; Kondoh, T.; Yoshida, Y.; Tanimura, K. and Urakawa, J. Femtosecond pulse
radiolysis and femtosecond electron diffraction. Nucl Inst Methods Phys Res A 2011, 637, 24–33
2. Ma, J.; Wang, F.; Denisov. S.A.; Adhikary, A. and Mostafavi, M. Reactivity of prehydrated
electrons toward nucleobases and nucleotides in aqueous solution. Sci Adv 2017, 3, e1701669
3. Ma, J.; Kumar, A.; Muroya, Y.; Yamashita, S.; Sakurai, T.; Denisov, S.A.; Sevilla, M.D.;
Adhikary, A.; Seki, S. and Mostafavi, M. Observation of dissociative quasi-free electron attachment
to nucleoside via excited anion radical in solution. Nat Commun. 2019, 10, 102.
Figure 1. Optical density evolution of
solvated electron signal @620 nm,
@1200 nm excited by repump (780 nm) pulse
after passage of 5 ps electron pulse.
Relaxation of the transient signals occurs after
less than 270 fs, corresponding to the
transition from p state to the s-like state.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
7
I3: Simulation of Radiation Damage Processes
A.V. Solov’yov
MBN Research Center, Altenhöferallee 3, 60438 Frankfurt am Main, Germany
The multiscale modeling of complex molecular systems is a hot topic of the modern theoretical
and computational research. Radiation damage is one of the exemplar topics in which the
multiscale approach is required for the understanding of the whole cascade of physico-
chemical, and sometimes even biological processes, that are behind the damages caused by
radiation in various targets [1, 2, 3]. To fully understand the dynamics of irradiated molecular
systems and exploit this knowledge in different technological applications, such as X-rays and
hadron therapy, radioprotection, surface deposition and nanofabrication technologies,
construction of novel light and energy sources, and others, one needs to consult many
disciplines ranging from physics and chemistry to materials and life sciences, software
engineering and high performance computing.
The recent advances in this research area have been achieved due to understanding of the
physical and chemical effects that involve different temporal and spatial scales. Illustrative
examples of such effects concern the ion-induced shock waves [4,5], radiation chemistry in the
vicinity of ion tracks [6], creation of complex irreversible damages in materials and biological
systems [1-3]. Molecular level understanding of these and many other processes can be
achieved by means of irradiation driven molecular dynamics (IDMD) [7], a powerful novel
multiscale computational technique implemented in professional software packages MBN
Explorer [1,8] and MBN Studio [1,9] enabling efficient computational studies of a broad range
of collision and irradiation driven processes involving numerous MesoBioNano systems.
The talk will give an overview of recent advances in the field of radiation damage which are
based on the multiscale approach. It will highlight a number of recent case studies that have
been performed by means of IDMD, MBN Explorer and MBN Studio.
References
[1] I.A. Solov’yov, A.V. Korol, A.V. Solov'yov, Multiscale Modeling of Complex Molecular Structure
and Dynamics with MBN Explorer, Springer International Publishing AG (2017), Cham, Switzerland,
451 pp.
[2] A.V. Solov’yov (ed.), Nanoscale Insights into Ion-Beam Cancer Therapy, Springer International
Publishing, Cham, Switzerland (2017), 498 pp.; E. Surdutovich, A.V. Solov'yov, Colloquium Paper,
Eur. Phys. J. D 68, 353 (2014)
[3] A. Verkhovtsev, E. Surdutovich, A.V. Solov'yov, Cancer Nanotechnology 10, 4 (2019)
[4] E. Surdutovich, A.V. Solov’yov, Phys. Rev. E 82, 051915 (2010)
[5] P. de Vera, E. Surdutovich, A.V. Solov'yov, Cancer Nanotechnology 10, 5 (2019)
[6 ] P. de Vera, E. Surdutovich, N.J. Mason, F.J. Currell, A.V. Solov'yov, Eur. Phys. J. D 72, 147 (2018)
[7] G.B. Sushko, I.A. Solov'yov, A.V. Solov'yov, Eur. Phys. J. D 70, 217 (2016)
[8] I.A. Solov’yov, A.V. Yakubovich, P.V. Nikolaev, I. Volkovets, A.V. Solov’yov, J. Comput. Chem.
33, 2412 (2012); www.mbnresearch.com; wikipedia.org/wiki/MBN_Explorer
[9] G.B.Sushko, I.A. Solov'yov, A.V. Solov'yov, J. Mol. Graph. Model., 88, 247 (2019)
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
8
I4: Mimicking Oxidative Stress by Radiation Biochemistry. Addition of
Free Radicals to a Free Radical Producer: NADPH Oxidase Stephenson Boayke Owusu, Laura Baciou, Tania Bizouarn, Chantal Houée Levin
Laboratoire de Chimie Physique. Univ. Paris Sud, Univ. Paris Saclay, CNRS UMR8000, 91405 Orsay France
Radiation biochemistry is a useful tool to mimic oxidative stress involved in the evolution of
all diseases with the advantage of being quantitative. One can study the free radical induced
processes of biomolecules. Moreover, one may enlighten new processes important for the
development of diseases.
Oxygen free radicals (reactive oxygen species, ROS) are also produced in vivo independently
of radiations. We are currently investigating the regulation of their production in neutrophils,
i.e. polynuclear white blood cells. They are capital for the destruction of pathogens, but also
noxious. Their production is due to a ubiquitous enzyme, NADPH oxidase, that delivers
superoxide anions in cells. In phagocytes, it is constituted by the assembly of at least four
cytosolic and two membrane proteins. This enzyme needs activation to produce superoxide
free radicals. In vitro, it is done by addition of arachidonic acid.
Our present interest is the regulation by free radicals themselves, that modify proteins and
hence their biological roles. We used gamma and pulse radiolysis to produce O2•- and •OH
radicals. In a cell-free system, we showed previously that during its assembly, the system
passes through sub-states of different sensitivities1. The regulatory activity of each protein
varies with their oxidation state and some of the important modifications were identified.
When human neutrophils are irradiated, very different processes take place. The NADPH
oxidase retains a basal activity after irradiation even in the absence of activator. The amount of
enzyme per cell increases slightly with the dose, like that of the total membrane proteins. In
addition, some cytosolic proteins are found at the membrane. Taken together these facts would
indicate a very low activation by free radicals.
1. Ostuni, M. A.; Gelinotte, M.; Bizouarn, T.; Baciou, L.; Houee-Levin, C., Targeting NADPH-
oxidase by reactive oxygen species reveals an initial sensitive step in the assembly process. Free
Radic Biol Med 2010, 49 (5), 900-7.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
9
P3: Molecular Simulations of the Oxidative Radiolysis of two Inverse
Peptides: Methionine Valine and Valine Methionine
P. Archirel, Ch. Houée-Lévin and J. L. Marignier
Laboratoire de Chimie Physique, Université Paris-Sud, 91405 Orsay, France
Oxidative radiolysis of the peptides has been performed at the Elyse facility of the LCP. The
two peptides undergo very different processes, as can be seen on the absorption spectra
recorded at different times and concentrations. We have also performed molecular simulations,
in order to interpret these spectra. Our method associates Monte-Carlo sampling of the nuclear
configurations, DFT and TDDFT calculations of the electronic structure and PCM simulation
of the solvent [1,2]. The results enable a fine understanding of the two species:
1. Met-Val displays a main band at 390 nm and no concentration effect. This is due to the
H atom uptake leaving a neutral radical Met-Val (-H) stabilized by a (2c-3e) SN bond.
This species is very stable and undergoes no bimolecular reaction with neutrals.
2. Val-Met displays a complex spectrum with at least three species, see figure 1, left, and
a striking concentration effect. The three species are plausibly a Val-Met (-H) radical
at high energy (285 nm), the Val-Met+ cation, stabilized by a (2c-3e) SO bond at middle
energy (367 nm) and a (Val-Met)2+ dimer cation, stabilized by a (2c-3e) SS bond, at
lower energy (540 nm), see figure 1, right. This last species can be formed either by
direct oxidation of neutral dimers present in solution, and by bimolecular dimerization
of cation monomers. This last species has not been simulated, but can be inferred from
simulations of the Met2+ cation [3].
Figure 1 Oxidative radiolysis of Val-Met: measured (left) and simulated spectra (right) of a
neutral radical (black curve), the cation (red curve) and the dimer (green curve)
References
1. Gaussian 09 RevD01 Gaussian Inc. Wallingford CT, 2013
2. Wang, F. Horne, G. Pernot, P. Archirel, P. and Mostafavi, M. J. Phys. Chem. B 122 (2018), 7134-
7142
3. Archirel, P. Bergès J. and Houée-Lévin, Ch. J. Phys. Chem. B 120 (2016), 9875-9886
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
10
P4: Comprehensive Model for X-Ray Induced Damage in Protein
Crystallography
D. Close, W. Bernhard
Acquisition of X-ray crystallographic data is always accompanied by structural degradation
due to the absorption of energy. The application of high fluency X-ray sources to large
biomolecules has increased the importance of finding ways to curtail the onset of X-ray induced
damage. A significant effort has been underway with the aim of identifying strategies for
protecting protein structure. A comprehensive model is presented that has the potential of
explaining, both qualitatively and quantitatively, structural changes induced in crystalline
protein at ~100 K. The first step is to consider the qualitative question, what are the radiation
induced intermediates and expected end products? The aim of this presentation is to assist in
optimizing these strategies through a fundamental understanding of radiation physics and
chemistry with additional insight provided by theoretical calculations performed on the many
schemes presented.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
11
PP1: Impact of Doping and Functionalisation of Graphene Support on the
Radiolytic Synthesis of Palladium Nanoparticles for Electrocatalysis
Kun Guo1,2 and Aliaksandr Baidak1,2
1School of Chemistry, The University of Manchester, Manchester M13 9PL, UK; 2Dalton Cumbrian Facility, The University of Manchester, Moor Row CA24 3HA, UK.
Gamma radiolysis of common solvents, including ethylene glycol, is known to generate strong
reducing species such as solvated electron, hydrogen atom and carbon-centred radicals. This
mechanism provides a green and facile route to synthesize colloidal metal nanoparticles (NPs)
immobilized on graphene-based supports. However, controlling the NP size and size
distribution remain challenging. Hereby we investigate the impact of heteroatom doping and
functionalisation of graphene-based supports on tackling such challenges. Four types of
graphene materials, namely graphene oxide (GO), reduced graphene oxide (rGO), graphene
(G), and nitrogen-doped graphene (N-G), are utilised to immobilize palladium (Pd) NPs, which
are obtained by γ-radiation-induced reduction in ethylene glycol. The as-prepared composites
are then evaluated in the electrocatalytic hydrogen evolution reaction (HER).
For the same Pd NP loading, N-G is found to be the best support to achieve the smallest
overpotential (difference between the applied and theoretical potentials) and the highest
catalytic activity, as shown in Figure 1a. The overpotential at a current density of 10 mA
cm−2 (η10) on Pd/N-G is 160 mV smaller than that on Pd/rGO. Tafel analysis derived from the
polarizaiton curves shows that Pd/N-G has a Tafel slope of 101 mV decade−1, indicating the
rate determining step of HER on Pd/N-G is the Volmer step (H3O++e−+ * ⇄H*+H2O, where
* denotes the active site). The activity difference of four composites should be ascribed to the
NP size and size distribution of Pd NPs anchored onto these supports. NP size is well-
documented to strongly affect the catalytic activity/selectivity because more surface active
sites are exposed as size decreases. N-G is thus
reasoned to gain the smallest Pd NP size and best
size distribution during the radiolytic synthesis,
which should be correlated to the positive role of
doped N atoms in stabilising the formed NPs.
Given the positive role of doped N atoms, we
further prepare N-G supported with four loadings
of Pd NPs to explore the potential threshold in
maintaining the Pd NP size. Figure 1b presents the
polarization curves of N-G loaded with 1.3~5.2 wt.
% Pd NPs and the benchmark Pt/C catalyst. The
best performance of Pt/C accords well with the
literature. In contrast, the η10 and Tafel slope are
found to be the smallest for 2.6 wt. % Pd/N-G,
indicating its highest HER catalytic activity. The
decreased activity of 3.9 and 5.2 wt. % Pd/N-G
should be attributed to the severe aggregation of
Pd NPs, leading to lower atom efficiency.
Therefore, in order to achieve a desirable NP size
and size distribution, the NP loading shall be
carefully controlled.
Figure 1. Polarization curves of Pd NPs
supported on four graphene-based supports
(a) and Pd NPs supported on N-G with four
loadings (b) in 0.5 M H2SO4.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
12
PP2: Role of Electronic Energy Loss of the Ion Beam in the Modification of
Graphene Oxide Film
Chetna Tyagi1,2, A. Tripathi2 and D. K. Avasthi3
1Dalton Cumbrian Facility, The University of Manchester, Cumbria, UK, 2Inter-University Accelerator Centre, New Delhi, India,
3Amity Institute of Nanotechnology, Amity University, Noida, India.
Ion beam irradiation is a clean method to produce desired modifications in materials in a
controlled manner [1]. The present work shows the modifications induced in graphene oxide
film under swift heavy ion irradiation with different electronic energy loss. Graphene oxide
films were irradiated with Gold ion beam having energy 120 MeV with fluences varying from
3×1010 ions/cm2 to 1×1013 ions/cm2. X-ray diffraction and spectroscopic techniques indicated
some annealing effect induced by ion beam at lower fluences of irradiation while signature of
carbyne could be seen in Raman spectroscopy at higher fluence (Figure 1). Similarly, Carbon
beam of energy 80 MeV with relatively low electronic energy loss was used to irradiate the
graphene oxide films with different fluences. Different characterization techniques showed the
creation of defects by ion beam in the films. Theoretical simulations showed the local lattice
temperature raised in the films when irradiated with ion beams having different energy loss. It
could be seen that ion beam having high electronic energy loss could raise the temperature of
the film above its annealing and melting temperature, resulting in two competing phenomena:
annealing and amorphization. Also, the estimated radius of the ion track (core and halo region)
formed by Gold ions irradiation was calculated experimentally and compared with the
theoretical values obtained by simulation.
(a) (b)
Figure 1. (a) Plot showing the intensity of in-situ X-ray diffraction peak of pristine and
irradiated sample and (b) Raman spectra of irradiated sample with different fluence. Magnified
part is showing the origin of carbyne peak at high fluences.
Reference
1. GK Mehta, (1997) Swift heavy ions in Materials Science – emerging possibilities, Vacuum, 48, 957-
959.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
13
PP3: Radiation Induced Polymerization of Nanostructured Conducting
Polymers
T. Bahry1 and S. Remita2
1Laboratoire de Chimie Physique, LCP, UMR 8000, CNRS, Université Paris-Sud 11, Bât. 349, Campus d’Orsay, 15 Avenue Jean Perrin, Orsay Cedex 91405, France
2Département Chimie Vivant Santé, Conservatoire National des Arts et Métiers, CNAM, 292 rue Saint-Martin, Paris Cedex 75141, France.
Conducting polymers (CPs) have gained vast attraction due to their unique optical and
electrical properties [1]. Thanks to these prominent and extraordinary properties, CPs have
been used in several fields and integrated in many applications [2]. Tremendous efforts have
been made to develop and upgrade the synthesis methodologies of CPs [3]. Apart from
traditional methods of polymers synthesis, ionizing radiation induced polymerization by -rays
without using oxidizing agents appears to be alternative and easy way to produce conducting
polymers. Indeed, our group has developed a new methodology based on radiation chemistry
to polymerize some of those conducting polymers (CPs) in aqueous solutions [4, 5]. Recently,
we extended this methodology to the synthesis of CPs in organic solvent [6]. In this context,
we succeeded in the oxidative polymerization of different classes of thiophene derivatives
monomers dissolved in dichloromethane by means of gamma-radiolysis (Figure 1). The
spectroscopic analysis and microscopic observations manifest that the radio-synthesized
polymers in dichloromethane are characterized by interesting optical and electrical.
Reference(s)
1. A. J. Heeger, J. Phys. Chem. 2001, 105 (36), 8476-8491.
2. R. Balint, et al., Acta Biomater. 2014, 10(6), 2341-53.
3. X. T. Zhang, et al., J. Phys. Chem. 2006, (110), 1158−1165.
4. Y. Lattach, et al., Radiat. Phys. Chem. 2013, (82), 44-53.
5. Z. P. Cui, et al., Langmuir. 2014, (30), 14086−14094.
6. T. Bahry et al., New J. Chem. 2018, 42 (11), 8704-8716.1.
Figure 1. PEDOT, P3HT and P3TAA synthesized by gamma radiolysis in
dichloromethane
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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PP4: Effect of Surface Deformation on Stress Corrosion Crack Initiation in
Austenitic Stainless Steels in PWR Primary Water
Litao Chang, M. Grace Burke, Fabio Scenini
Materials Performance Center, The University of Manchester, Manchester, UK M13 9PL
Austenitic stainless steels are widely used in the nuclear power plants due to their good general
corrosion resistance to the high temperature aqueous environment. However, they can suffer
from environmentally-assisted degradation problems, such as stress corrosion cracking (SCC),
during the long-term exposure to the environment. Numerous researches indicate that cold-
work, induced either intentionally or incidentally, is necessary for SCC in austenitic stainless
steels in PWR primary water. In the present study, the effect of the machining-induced surface
deformation on SCC initiation of austenitic stainless steels in PWR primary water has been
investigated through accelerated slow strain rate tensile tests and microstructural
characterization. The results showed that machining always introduced a deformation layer to
the steels. This layer is characterized by an ultrafine-grained outer layer and a highly deformed
inner layer consisted of twins and dislocations. SSRT test results showed that machining
significantly reduced the SCC initiation susceptibility of the cold-worked material as a reduced
number of cracks were identified in the machined surface compared to the polished surface.
The results also indicated that a low temperature heat treatment could further increase the SCC
initiation resistance of the machined surface because of the recovery which happened with the
ultrafine-grain. The associated mechanisms and possible implications of the results have been
discussed.
Reference(s)
1. Chang et al., Stress corrosion crack initiation in machined type 316L austenitic stainless steel in
simulated pressurized water reactor primary water, Corr. Sci. (2018) 138, 54-65
2. Chang et al., Effect of machining on stress corrosion crack initiation in warm-forged type 304L
stainless steel in high temperature water, Acta Mater. (2019)165, 203-214
3. Chang et al., Understanding the effect of surface finish on stress corrosion crack initiation in warm-
forged stainless steel 304L in high-temperature water, Scripta Mater. (2019) 164, 1-5
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
15
PP5: Method of Assessing the Radiation Tolerance of Commercial
Strippable Coatings
A. Jenkins1, L. Ostle1, T. Donoclift2, R. Edge2, T. Unsworth2, K. Warren2
1 Sellafield Ltd., Seascale, Cumbria. UK
2Dalton Cumbrian Facility, The University of Manchester, Westlakes Science Park, Moor Row,
Cumbria. UK
There are a plethora of commercially available strippable coating products, designed for
contamination control and decontamination purposes. Sellafield Ltd. has sought for a number
of these to be subjected to a predefined series of analyses pre and post irradiation to observe
any degradation of the product. Irradiation of the coatings to doses of 500kGy was separately
carried out by cobalt-60 and ion-beam to mimic plutonium alpha particles by Dalton Cumbrian
Facility. This dose threshold was deemed sufficient to allow for wastes to be packaged and
reach the respective disposal point.
A series of analyses were carried out and comparisons made of the pre and post irradiation.
The analyses included; direct observations for physical colour changes and deformities,
scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR),
Raman spectroscopy, Gas Chromatography – Mass Spectroscopy (GC-MS) and energy-
dispersive X-ray spectroscopy (EDS).
An illustration of how these coating systems degrade will be given alongside more anecdotal
perspective of how more easily obtained gamma irradiation can be used to infer alpha
degradation of organic species.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
16
PP6: Studying Nascent Proton-Driven Radiation Chemistry in H2O in Real
Time Using Laser-Based Sources
M. Coughlan1*, N. Breslin1, M. Yeung1
, H. Donnelly1, C. Arthur1, L.Senje2, M. Taylor1, G.
Nersisyan1, D. Jung1, M. Zepf2 and B. Dromey1
1Department of Physics and Astronomy, Queen’s University Belfast, Belfast, United Kingdom 2Helmholtz-Institut Jena, D-07743 Jena, Germany
Understanding the effects of ion interactions in condensed matter has been a focus of research
for decades. While many of these studies focus on the longer term effects such as cell death or
material integrity, typically this is performed using relatively long (>100 ps) proton pulses from
radiofrequency accelerators in conjunction with chemical scavenging techniques [1].
As protons traverse a material, they generate tracks of ionisation that evolve rapidly on
femtosecond timescales. Recently, measurements of few-picosecond pulses of laser driven
protons have been performed via observation of transient opacity induced in SiO2 with sub-
picosecond resolution [2]. Here we present results showing a dramatic difference in the
solvation of electrons generated due to the interaction of relativistic electrons/X-rays and
protons in liquid water. The role of ionisation tracks and subsequent formation of nanoscale
cavities in water on the extended recovery time is discussed.
References
[1] G. Baldacchino, Radiation Physics and Chemistry, 77, 1218-1223 (2008). [2] B.Dromey, et al. Nature Communications, 7, 10642
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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WEDNESDAY 11th SEPTEMBER
08:00 Sunrise Session - Heterogeneous, Simon Pimblott
09:00
09:35
10:10
10:35
Heterogeneous–I Session, Chair - Simon Pimblott
I5: “H2 and H2O Production from Water and Alumina” Jay LaVerne
I6: “Radiolytic Formation of H2O: The Elucidation of the H2/O2 Recombination
Mechanism” Darryl Messer
P5: “Electron Irradiation Treatment of Nanodiamonds” Christian Laube
P6: “Hydrogen Production by Steel Anoxic Corrosion under Gamma Irradiation”
Lina Giannakandropoulou
11:00 Coffee
11:20
11:55
12:30
Heterogeneous–II Session, Chair - Jay LaVerne
I7: “Radiolytic Hydrogen Production in Oxide and Hydroxide Sludges” Mel
O’Leary
I8: “Radiation-Induced Chemistry on Polymer-Liquid Interfaces and Diffusive
Behaviour of H2” Aliaksandr Baidak
P7:“Radiolytic Degradation of an Extractant for Actinides, HONTA — a
Comparative Study of Direct and Indirect Radiolysis Processes” Yuta Kumagai
13:00 Free Time
16:00 Poster Session 2 (odd numbers)
17:00
17:45
18:30
Industrial Hot Topics Session, Chair - Fred Currell
H1: “Research in Radiation Chemistry to Support the Safe Storage of Plutonium
on the Sellafield Site” Helen Steele
H2: “The Radiation Chemistry of Spent Nuclear Fuel Systems” Steve Walters
Panel discussion: Panel - Steve Walters, Helen Steele, Mats Jonsson, Robin Orr
19:00 Coaches for Cockermouth
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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I5: H2 and H2O Production from Water and Alumina
J. A. LaVerne
Radiation Laboratory and Department of Physics, University of Notre Dame, Notre Dame,
Indiana, USA 46556
The main stable products in the radiolysis of water are H2 and H2O2. Both of these compounds
have transient precursors that can be affected by the presence of a heterogeneous interface.
Energy, mass or charge transfer between the interface and the nearby water can lead to variation
in the yields of H2 and H2O2 from what is observed in the radiolysis of neat bulk water. While
H2 is relatively stable in most circumstances, H2O2 is well known to react with surfaces.
This presentation will discuss the radiolytic formation of H2 and H2O2 including some of our
most recent water radiolysis models. Heterogeneous interactions will focus on water – alumina
interfaces, with the latter chosen because of its importance in the nuclear power industry.
Comparisons of the production of H2 with alumina will be made with the many other water –
solid ceramic oxides that have been examined. The production of H2 from adsorbed water on
alumina and from water – alumina slurries will be presented. Both the changes in the water
chemistry and in the alumina surface will be shown to gain information on processes occurring
at the interface. H2O2 is much more tenuous to examine because of its often fast reactivity with
solid surfaces. Fortunately, the reaction of H2O2 with alumina is relatively slow with respect to
the time scale of the radiation experiments. Mechanisms for the production of H2O2 under
different radiolytic conditions in bulk water and with added alumina will be presented.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
19
I6: Radiolytic Formation of H2O: The Elucidation of the H2/O2
Recombination Mechanism
D. Messer1, R. Orr2, Sven Koehler3, Andrew Horn4, Simon Pimblott5
1-Dalton Cumbrian Facility, Westlakes Science Park, Moor Row, Cumbria, CA24 3HA, UK;
2-National Nuclear Laboratory, Sellafield, Seascale, Cumbria, CA20 1PG, UK 3-School of Science & the Environment, Manchester Metropolitan University, Chester St, Manchester,
M1 5GD, UK. 4-The University of Manchester, Chemistry Department, Manchester. M13 9PL, UK
5-Idaho National Laboratory, Idaho Falls, ID 83415, USA.
Currently, the majority of the UK’s PuO2 stockpile produced by the reprocessing of spent
nuclear fuel is stored at the Sellafield site. The production of H2 and O2 by radiolysis of H2O
adsorbed to the surface of PuO2 is a safety concern for the UK nuclear industry by means of
storage vessel pressurisation and the potential formation of flammable gas mixtures. Lack of
observation of storage canister pressurisation in industry suggests recombination between H2
and O2 occurring simultaneously to H2O radiolysis. Here, we have developed a kinetic model
for the 1-1-98 vol% H2-O2-Ar system which, alongside coinciding experimental studies, has
been used to elucidate a reaction mechanism of such recombination reactions.
The model shows close agreement to
experimental results, depicted in
Figure 1. We elucidate a two-step
process for H2/O2 recombination: a
primary pathway initiated by
excitation/ionisation of Ar;
following by a secondary, H2O-
catalysed pathway. This secondary
pathway forms reactive
intermediates by water-catalysed
reactions with H2, which then
proceed to produce further H2O. The
OH∙ radical is involved in all H2O
forming termination steps, and each
pathway initiates via the
excitation/ionisation of Ar.
Figure 2 - Comparison of experimental and computational
results for H2 consumption for the 1-1-98 %vol H2-O2-Ar -
irradiated system. Black = experimental results, Red = model
results
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
20
P5: Electron Irradiation Treatment of Nanodiamonds
C. Laube1, J.Zhou2, A.Kahnt1, W. Knolle1, Bernd Abel1
1Leibniz Institut of Surface Engineering, Leipzig, Germany, 2Helmholtz Centre of Environmental Research UFZ, Leipzig, Germany
Nanodiamonds (NDs) offer great potential on multiple fields of research such as medical and
sensory application. Herein, the tailoring of the ND surface functionalities and color center
formation inside the diamond lattice can be regarded as key factors for the suitability of the
NDs for these applications. Especially the efficient formation of NV color centers lies within
the focus of modern application. In this work, we demonstrated the application of electron
irradiation as a powerful tool for tailoring these properties. In particular we demonstrated the
efficient surface modification of NDs based on a pulse radiolysis approach of ND suspension.
As a test model we established the efficient surface chlorination of NDs by electron irradiation
of ND suspension in halogenated solvents.1 Furthermore, electron irradiation was applied for
the effective formation of lattice vacancies, in order to enhance the formation of NV centers.
Within a comprehensive study we demonstrated that the formation and the resulting properties
of NV centers can be controlled via irradiation treatments, parameters and the surface
functionalities.2
Reference(s)
1. J. Zhou, C. Laube, W. Knolle, S. Naumov, A. Prager, F.-D. Kopinke and B. Abel, Diamond
and Related Materials, 2018, 82, 150-159.
2. C. Laube, T. Oeckinghaus, J. Lehnert, J. Griebel, W. Knolle, A. Denisenko, A. Kahnt, J.
Meijer, J. Wrachtrup and B. Abel, Nanoscale, 2019, 11, 1770-1783.
Figure 3 Shematic illustration of the preparation approaches
for the nanodiamond surface chlorination (above)
and NV center formation (below).
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
21
P6: Hydrogen Production by Steel Anoxic Corrosion under Gamma
Irradiation
Lina Giannakandropoulou1, Benoît Marcillaud1, Stéphane Poirier1, Hortense Desjonqueres1,
Charles Wittebroodt2, Gérard Baldacchino3
1Institute for Radiological Protection and Nuclear Safety (IRSN), PSN-RES/SCA/LECEV, BP68, Gif-sur-Yvette, France;
2Institute for Radiological Protection and Nuclear Safety (IRSN), PSE-ENV/SEDRE/LETIS, BP17,
Fontenay-aux-Roses; 3LIDYL, Université Paris-Saclay, Atomic Energy and Alternative Energy Commission (CEA), Gif-sur-
Yvette, France.
In the framework of the storage of High Level nuclear Wastes (HLW), ANDRA (National
Radioactive Waste Management Agency in France) is planning their isolation in deep
geological disposals. Such a disposal repository concept is based on a multi-barrier system
including large amount of metallic elements such as stainless steel primary canister or carbon
steel casing for HLW disposal gallery. After a period of several decades, anoxic corrosion of
these metal elements will cause a release of hydrogen gas [1]. Simultaneously, the radiation
emitted by radioactive wastes would lead to the radiolysis of the water present in the
geological formation. This process may lead to a production of additional hydrogen gas and
other redox species likely to modify the redox conditions of the aqueous medium as well as the
corrosion processes of the steel and therefore, the hydrogen production [2].
This study aims at assessing the influence of
-irradiation on H2-production rate through the
anoxic corrosion of carbon steel process. Two
experimental stainless steel cells are placed in an
irradiation chamber IRMA (IRSN facility)
where they are exposed to -radiation of 60Co
(50 Gy/h) for twelve days. The first cell contains
carbon steel coupons (15 gr) immerged in pure
deaerated water (100 mL) and the second cell
contains only pure deaerated water. An He-gas
flows through these cells to a gas chromatograph
for measuring the evolution of H2-production
before, during and after irradiation. Post-mortem analysis are then performed on liquid and
solid phases. Metallic samples is structurally characterized for the identification of the formed
corrosion products upon their surfaces with XRD, μRaman spectroscopy and SEM-EDS
microscopy. The loss of mass of the coupons is measured in order to estimate the carbon steel
corrosion rate. Liquid samples are analysed for their Eh and pH values. In parallel, UV-Vis
spectroscopy is used to determine the concentration of both dissolved Fe2+ and Fe3+ ions. A
fluorescence method is used to assess the hydrogen peroxide (H2O2) concentration. Finally,
kinetics are compared with those obtained by simulations using Chemsimul software. First
results on H2-production show that our experiment allows us to distinguish in time the
contributions of the solid phase (corrosion) and the radiolytic processes in the bulk of the liquid
phase. These results are also supported by simulation in the homogeneous liquid phase but
needs an heterogeneous approach modelling the interface processes.
References
1. Smart, N.R., Rance, A.P., Werme, L.O., 2008.The effect of radiation on the anaerobic corrosion of steel. Journal of Nuclear Materials 379, 97-104.
2. Pimblott, S. M. and LaVerne J. A., 1992. Molecular product formation in the electron radiolysis of
water. Radiation Research 129(3): 265-271.
Figure 1 : µRaman spectra indicates the
presence of magnetite at 675 nm.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
22
I7: On Radiolytic Hydrogen Production in Oxide and Hydroxide Sludges
M. O’Leary1, I. P. Dolbnya2, A. Baidak1, C. Emerson3, C. Figueira3, O.J.L. Fox2, A.K.
Kleppe2, A. McCulloch3, D. Messer1, and F. Currell1
1Dalton Cumbrian Facility (The University of Manchester), Cumbria, UK; 2Diamond Light Source, Oxfordshire, UK; 3Queen’s University Belfast, Antrim, UK.
The radiolytic hydrogen yield and hydrogen diffusivity was measured in a number of oxides
(ZrO2, TiO2, ZnO, Al2O3, CeO2) and hydroxides (Mg(OH)2 ). These yields where determined
with a previously presented method [1] involving electrochemical hydrogen probes from
Unisense A/S [2]. The hydrogen concentration was measured with a probe a millimetre above
the irradiated region in the sludge. The lower limit to these diffusivities is described by a simple
model, blue curve on graph in figure 1. These results indicate that the hydrogen is not holding
up on the surface of the nano-particles of these oxides. The radiolytic yield of hydrogen in all
sludges are significantly increased over the expected yield for water alone, which would be 0.5
µmol/J.
Some of these sludges where irradiated with the full x-ray spectrum of the synchrotron, called
white beam irradiation. These sludges where imaged during these irradiations. These images
show the formation of micro bubbles in these sludges, as seen in figure 2. These bubble
formation dynamics further illuminate the behaviour of hydrogen in these sludges.
Reference(s)
1. O’Leary, M. et al. (2017) Method for the determination of Effective Diffusivity and G-value of
Hydrogen in Magnox Sludge Mimics. 30th Miller Conf.
2. Online: https://www.unisense.com/H2/ (retrieved 20/6/19)
3. Zhou, Tunhe, et al. (2018) Development of an X-ray imaging system to prevent scintillator
degradation for white synchrotron radiation. Journal of synchrotron radiation.
Figure 1 The relationship between
nanoparticle concentration and hydrogen
diffusivity in sludges.
Figure 2 Three x-ray images taken with a
PCO edge camera [3] of a magnesium
hydroxide sludge undergoing irradiation by
white beam at the Diamond Light Source.
The first at the irradiation start. The second
image taken at 20 seconds into irradiation,
shows earliest signs of bubble formation.
Third image shows a definite spherical
bubble which appears 27 seconds into
irradiation. The red circle surrounds the
bubble in the third image and the same
region in the other images.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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I8: Radiation-Induced Chemistry on Polymer-Liquid Interfaces and
Diffusive Behaviour of H2
Aliaksandr Baidak,1,2 Imene Boughhattas,1,2 Gemma Draper, 1,2 Darryl Messer, 1,2 Mel
O’Leary 1,2
1 Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
2 Dalton Cumbrian Facility, University of Manchester, Westlakes Science Park, Moor Row, Cumbria,
CA24 3HA, United Kingdom
Radioactive sludges made of organic materials and water are commonly encountered in nuclear
industry. Radiolytic processes in such systems often pose a serious safety hazard during the
long-term storage of these materials due to the release of flammable gases or production of
corrosive water-soluble products. In particular, polystyrene-based (PS) ion exchange resins
(IERs) are commonly used for radioisotope separation process, nuclear waste treatment and
reactor coolant demineralisation. [1] After their use, IERs with accumulated radionuclides
become hazardous materials; at this point they are handled as low or intermediate level nuclear
waste. [2] In the context of the long-term storage of nuclear waste it is important to discriminate
the effects of the high vs. low Linear Energy Transfer (LET) radiation on the IERs since both
alpha and gamma emitting radioisotopes might be present in spent ion exchange resins.We
report the radiation chemical yields for the degradation of several IERs materials obtained
through 20 keV synchrotron X-ray, Co-60 gamma and 5.5 MeV He2+ ion irradiations.
We have determined the absolute yields (G-values) as well as diffusion behaviour of H2 from
several nuclear grade ion exchange resins. For the IER-containing slurries we also measured
the yields of pH active leachates (H2SO4 or (H3C)3N) to evaluate their effect on the H2
formation.
Obtained results reveal that the radiation hardness of the studied resins largely depends on the
type of a functional group they possess. The polystyrene and the sulphonated cation exchange
resin produce relatively low yields of H2, whereas the mixed bed and especially the anion
exchange resin form appreciable amounts of molecular hydrogen. [4] All studied polymers
show an increase in molecular hydrogen yield with increasing LET as it follows from
comparison of the helium ion vs. gamma radiolysis. Such increase in net molecular hydrogen
yield at a higher LET might be explained by the second-order reactions competing efficiently
with self-scavenging reactions of H atoms by the aromatic moieties of PS. Furthermore, our
experiments show that the G(H2) is strongly dependent upon the relative amount of water
associated with the resin. Using X-ray tomography, we have successfully visualised the in situ
H2 bubble formation in resin-water slurries. The initial shape of bubbles, and their subsequent
growth and escape is found to be dependent on an average particle size of the resin. This finding
might be important while considering the diffusion of H2 in a resin-water slurry; it provides
further valuable insight into the hydrogen transport in organic nuclear waste.
In summary, the comprehensive radiation chemistry study of IERs presented here provides
helpful guidelines for a safe management of the organic nuclear waste.
References:
1. J.J. Wolff. Purolite Ion Exchange Resins, Bala Cynwyd, USA, (2012).
2. K.K.S Pillay. J. Radioanal. Nucl. Chem., 97, 135 (1986)
3. C. Rebufa et al. Rad. Phys. Chem., 106, 223 (2015)
4. A. Baidak, J. A. Laverne. J. Nucl. Mat., 407, 211 (2010).
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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P7: Radiolytic Degradation of an Extractant for Actinides, HONTA — a
Comparative Study of Direct and Indirect Radiolysis Processes
Y. Kumagai1, T. Toigawa1, S. Yamashita2, T. Matsumura1
1Japan Atomic Energy Agency, Ibaraki, Japan; 2The University of Tokyo, Ibaraki Japan.
Ionizing radiation induces degradation of organic molecules. This action of ionizing radiation
needs to be incorporated in designing and safety evaluation of solvent extraction processes for
separation of radioactive elements [1]. A reliable estimation of the effect of radiolysis requires
understanding of the degradation mechanism as well as basic data regarding the extractant
degradation and its radiolytic products. This study focuses on a promising extractant for
separation of actinides from lanthanides, hexaoctyl- nitrilotriacetamide (HONTA) [2]. We have
investigated the radiolysis of HONTA by LC-MS/MS analysis of radiolytic products of
HONTA and by UV-visible spectroscopy of its radical transient using pulse radiolysis
technique. In these experiments, radiolysis of neat HONTA and that of HONTA in dodecane
solvent are compared in order to understand the degradation mechanism.
The samples for the product analysis were irradiated by 60Co γ-ray (60Co irradiation facility,
QST Takasaki) and were analysed by an LC-MS/MS system (Shimadzu, LCMS-8300). The
mass-chromatograms for the irradiated neat HONTA and 10 mM HONTA in dodecane are
shown in Figure 1. We found 43 products, in total, of HONTA degradation. Among them, 14
products were commonly observed in the radiolysis of neat
HONTA and the dodecane solution, 20 products were only
found in the neat HONTA, and 9 products are characteristic
for the dodecane solution. Indeed, 14 out of 43 products are
common in these two, although the initial radiolysis
processes in these samples must be different, i.e. direct
ionization and excitation of HONTA occur under neat
condition, whereas the degradation of HONTA is due to
reactions of radicals from dodecane radiolysis in the
solution. This result suggests that the direct and the indirect
processes have a common reaction pathway. Therefore, we
measured absorption spectra of transient species by using a
nano-second pulse radiolysis system. (LINAC facility,
Univ. Tokyo) in order to investigate the reaction pathways.
The measured spectra had similar shapes in this time
domain regardless of the HONTA concentrations. This
indicates that there is a common transient both in the
radiolysis of neat HONTA and of dodecane solution of
HONTA. Consistently with the product analysis, the result
of the pulse radiolysis experiment indicates a common
reaction pathway between the direct and the indirect
radiolysis. Acknowledgment: This work was supported by JSPS KAKENHI Grant Numbers JP18K05001.
References
1. Mincher, B.J., Modolo, G., and Mezyk, S.P. (2009) Review Article: The effects of radiation
chemistry on solvent extraction 3: A review of actinide and lanthanide extraction. Solvent Extr. Ion
Exch., 27, 579-606
2. Sasaki, Y., Tsubata, Y., Kitatsuji, Y., and Morita, Y. (2013) Novel Soft-Hard Donor Ligand,
NTAamid, for Mutual Separation of Trivalent Actinoids and Lnthanoids, Chem. Lett., 42, 91-92.
Figure 1 Mass chromatograms of the irradiated samples (130 kGy); (a) neat HONTA, (b) 10mM HONTA in n-dodecane.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
25
H1: Research in Radiation Chemistry to Support the Safe Storage of
Plutonium on the Sellafield Site
H. Steele and J. Hobbs
Sellafield Ltd. Seascale Cumbria CA20 1PG UK.
The UKs plutonium inventory has been safely stored on the Sellafield site for over 40 years.
The majority of the plutonium is stored in its oxide form, in gas-tight packages that were sealed
following heat treatment and conditioning. However, the radioactive decay of plutonium results
in the generation of heat, alpha particles and gamma radiation which can perturb conditions
within the packages. In order to ensure onward safe storage, including the necessity for
transportation, and package inspection it is essential to understand how the emitted radiation
interacts with residual adsorbed materials, packaging and the range of internal head-gases.
Radiation plays a dual role within PuO2 containing packages, that of the foe in decomposing
contaminants and materials and a friend in catalysing recombination reactions. To understand
the totality, Sellafield Ltd has undertaken a number of research activities of what is a complex
field and experimentally very challenging.
Figure 4 Recombination of H2 and O2 due to adsorbed dose. L Jones DCF
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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H2: The Radiation Chemistry of Spent Nuclear Fuel Systems
W S Walters
National Nuclear Laboratory, Building D5, Culham Science Centre, Abingdon, Oxfordshire, UK;
Radiation chemistry is a major factor in the “features, events and processes” which describe
the technology attending the safe management of spent nuclear fuel. The radiation chemistry
involves interactions between the ionising radiation emitted from the fuel and absorbing
medium (be that water in a pond, or a gas in a dry store arrangement).
The radiolysis of water has been well studied down the years. The principal products are
molecular hydrogen, hydrogen peroxide, and oxygen, along with steady state concentrations of
various radicals and ionic species. The mechanism, yields and reaction kinetics of the radiolytic
reactions are well known 1. However, the possibility of hydrogen and oxygen accumulating in
any gas space present serves to raise safety concerns for nuclear plant; an understanding of
rates of gas production and yields are of key importance in underpinning any safety case.
Computer modelling of such radiolytic systems has long been used to predict the development
of gas mixtures in operational plant. However the effects of solutes or pH adjustments to the
pond water may have the effect of altering gas production rates from those associated with pure
water. This presentation will include consideration of the basics, the modelling approaches,
with chemistry effects and their impact in real plant situations.
The radiation chemistry is also influenced by interactions with surfaces. Some of the energetic,
short lived radical species which reach steady state in an irradiated aqueous solution (together
with oxygen and hydrogen peroxide) may be capable of oxidising metal surfaces in ways that
water would normally not. Because spent nuclear fuel systems usually contain a number of
different metals (the container, the fuel cladding, any dissimilar metal components which are
part of the container, the fuel, or pond facility, have the possibility of removing oxidising
species from the radiolytic system and producing a metal oxide (or hydroxide) along with a
nett reducing radiolytic environment, which in turn influences further radiolysis 2. These effects
will be described.
Dry storage of nuclear fuel has many equivalent features – i.e. radiolysis of the principal cover
gas (but also including any minor impurities in the gas). Depending on the availability of such
impurities, some molecular products are possible which represent acidic or alkaline species and
these in turn are capable of interacting with metallic materials in the fuel containment system.
The transfer of energy from “inert” gases to impurity products also affects the rate of
production of chemically active species. Examples will be presented of how gaseous systems
may interact with stored fuel, particularly in a UK context.
Reference(s)
1. Elliot, A.J. and Bartells, D.M. (2009) “The Reaction Set, Rate Constants and g-Values for the
Simulation of the Radiolysis of Light Water over the Range 20° to 350°C Based on Information
Available in 2008” AECL report 153-1 271 60-450-001.
2. LeCaer, S. Water Radiolysis: “Influence of Oxide Surfaces on H2 Production under Ionizing
Radiation”. Water 2011, 3, p 235-253.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
27
THURSDAY 12th SEPTEMBER
08:00 Sunrise Session - Health, Fred Currell and Joao Alberto Osso Junior
09:00
09:35
10:10
10:35
Health–I Session, Chair - Joao Alberto Osso Junior
I9: “Monte Carlo Track-Structure Simulations for Boron-Neutron Capture
Therapy” Jose Ramos-Mendez
I10: “Nanoagents to Improve Radiotherapy and Hadrontherapy Performances:
Green Synthesis and Impact on Blood Proteins” Sandrine Lacombe
P8: “Study on the Dose Enhancement in Water by Activation of Clusters of
Nanoparticles of High-Z Materials with a 6 MeV True Varian Linac” Balder
Villagomez-Bernabe
P9: “New Explanation for Radiosensitization by Gold Nanoparticles: Chemical
Effect” Viacheslav Scherbakov
11:00 Coffee
11:30
12:05
12:30
Health–II Session - Chair TBC
I11: “Oxygen Effects on Antioxidant Protection of Lymphoid Cells against Free
Radicals by a Range of Dietary Carotenoids” Ruth Edge
P10: “Effects of Additives on Radiation-Induced DNA Damage: From the
Viewpoints of Free Radical Scavenging and Chemical Repair” Hao Yu
P11: “Solvation Effects on Dissociative Electron Attachment to Thymine” Bin Gu
12:55 Coaches to DCF
13:30 Lunch and Tours of DCF (Trustees Business Meeting using DCF meeting room)
16:30 Coach to Cockermouth (free time until 18:30 then coach to Energus)
19:00 Conference Dinner, return coaches at 23:00
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
28
I9: Monte Carlo Track-Structure Simulations for Boron-Neutron Capture
Therapy
J. Ramos-Méndez1, N. Domínguez-Kondo2, E. Moreno-Barbosa2 and B. Faddegon1
1Department of Radiation Oncology, University of California San Francisco, California, USA; 2Facultad de Ciencias Físico-Matemáticas, Benemérita Universidad Autónoma de Puebla, Puebla,
MEX.
Boron neutron-capture therapy (BNCT) promises much reduced damage to healthy
tissue, with the dose distribution conforming precisely to the target when boron is preferentially
delivered to the tumour. After a thermal neutron is captured by boron, two ion recoils with very
short range (<10 μm) are released: a 0.84 MeV lithium-ion and a 1.47 MeV alpha particle.
Characterization of the track-structure of these combined ions is important to the understanding
of radiobiological effectiveness of BNCT. The open source Geant4-DNA Monte Carlo track
structure code is a good candidate to perform this task, due to its flexibility and accuracy.
However, Geant4-DNA physical cross-sections for ions heavier than alphas are unavailable
below 1 MeV/u. The aim of this work was to extend the inelastic cross-sections for lithium
ions of Geant4-DNA to low enough energies to characterize the track-structure of BNCT and
the subsequent radiolysis process.
The Barkas’ effective charge factor [1] was used to
extend, down to 100 eV/u, the inelastic cross sections of ions
from those of protons and hydrogen ions available in
Geant4-DNA. A phenomenological two-factor correction to
account for the differences in the cross-sections observed in
carbon-ion data from the literatue was applied. To verify the
calculated cross-sections, the stopping power of carbon and
lithium ions in water was calculated and compared with data
from ICRU [2] and Montenegro et al [3]. In addition, G-
values (species per 100 eV of energy deposited) from an
alpha-lithium source interacting in neutral water were
calculated with the Independent Reaction Times method.
Satisfactory agreement was found between
calculated ion stopping power and published data for low
energies (1 keV/u - 1 MeV/u) with an overall convergence
at higher energies (Figure 1). Calculated G values from
alpha-lithium source will be presented.
A set of lithium cross-sections suitable for BNCT
track-structure studies have been made available in Geant4-
DNA.
Reference(s)
1. Schmitt, E., Friedland, W., Kundrát, P., Dingfelder, M. and Ottolenghi A. (2015) Cross-section
scaling for track structure simulations of low-energy ions in liquid water Radiat. Prot. Dosimetry 166
15–8.
2. International Commission on Radiation Units and Measurements. (2005) Stopping of ions heavier
than helium. ICRU Report 73.
3. Montenegro, E.C., Shah, M.B., Luna, H., Scully, S.W.J., de Barros, A. L.F., Wyer, J.A. and
Lecointre, J. (2007) Water fragmentation and energy loss by carbon ions at the distal region of the
Bragg peak. Phys. Rev. Lett. 99, 21320.
Figure 1. In-water stopping
power for carbon (black) and
lithium (blue) ions. Data
from the literature is shown
with markers.
0
100
200
300
400
500
600
700
800
900
1000
100
101
102
103
Carbon-ion
Lithium-ion
Sto
ppin
g p
ow
er
(keV
/mm
)
Energy (keV/u)
Geant4-DNA
ICRU
Montenegro
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
29
I10: Nanoagents to Improve Radiotherapy and Hadrontherapy
Performances: Green Synthesis and Impact on Blood Proteins
S. Lacombe
ISMO UMR, Université Paris Saclay, Université Paris Sud, CNRS, Orsay cedex, France
Radiotherapy and chemotherapy are the gold standards to treat cancer. Recently, it was
shown that metal-based nanoparticles could improve the performance of radiotherapy. 1
Currently, the production of radio-enhancing nanodevices (e.g. gold nanoparticles, hafnium
dioxide nanodevices etc..) is processed via chemical synthesis, which often involves the
utilization of toxic solvents. Hence, multiple steps of cleaning are used to obtain
biocompatible and sterile solutions, which degrades the production and increases
environmental hazard. The group optimized a new solvent-free, “green” and highly
reproducible method to produce small, non-toxic and stable radio-enhancers diluted in sterile
solutions, with 100% rate.
In parallel, a synchrotron radiation circular dichroism experiment has been optimized to
characterize their impact (toxicity) on blood proteins.
In summary, the development of alternative approaches to design and test novel radio-
enhancers is a new era, which should lead to a dramatic improvement of cancer treatments.
Reference 1 Kuncic, Z.; Lacombe, S. Nanoparticle radio-enhancement: Principles, progress and application to
cancer treatment. Phys. Med. Biol. 2018, 63, 02TR01.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
30
P8: Study on the Dose Enhancement in Water by Activation of Clusters of
Nanoparticles of High-Z Materials with a 6 MeV True Varian Linac
B. Villagomez-Bernabe1,2 and F. Currell1,2
1Chemistry Department, The University of Manchester, Manchester, UK; 2Dalton Cumbrian Facility, Cumbria, UK.
During the last decade, different nanomaterials have been implemented for biomedical
applications in Nanomedicine, such as imaging agents [1] and drug delivery agents [2].
Furthermore, different types of nanoparticles are being studied as radiosensitizers in cancer
treatment [3,4]. This work aims to calculate through Monte Carlo simulations the dose
enhancement in water for three different nanoparticles composition such as gold, silver and
gadolinium in order to compare their effectiveness based only on the physical interactions
between gamma irradiation and the nanoparticles, i.e. without taking into account the influence
of the radicals formed by each type of nanoparticles. Nevertheless, as far as the authors are
aware, such a computational study involving clustering of nanoparticles has not been published
to date.
The present work is divided into two stages, during the first
stage, the random positions of the nanoparticles inside a
water sphere were calculated using Wolfram Mathematica.
This mimics the sub-cellular distribution of nanoparticles
commonly observed using microscopy. Those coordinates
were used to create a parameter file in TOPAS [5] with the
information of the position, material and size of the
nanoparticles. The geometry set-up created with the
parameter file is shown in Fig. 1, where a cluster of
nanoparticles was loaded into TOPAS for posterior
irradiation with a 6 MeV True Varian Linac obtained from
the International Atomic Energy Agency website. Then, a
phase space file placed around the cluster of the
nanoparticles was used to record all electrons going out from the cluster. The final stage
involves the releasing of all particles from the space phase file previously recorded during stage
1 into a water phantom in order to measure the dose deposited in radial bins around the cluster.
The Geant4-DNA physics list was used to track low energy electrons down to 10 eV. The radial
dose distribution for each type of nanoparticle were compared against each other and plotted
for better visualization.
Reference(s)
1. Rippel R.A. and Seifalian A.M. (2011) Gold Revolution -Gold nanoparticles for modern medicine
and surgery. Journal of Nanoscience Nanotechnology, 11, 7340-48.
2. Ghosh P., Hang G., De M., Chae K.K. and Rotello V.M. (2008) Gold nanoparticles in delivery
applications. Advanced Drugs Delivery Reviews, 60, 1307-15.
3. McMahon S.J. et al (2011) Nanodosimetric effects of gold nanoparticles in megavoltage radiation
therapy. Radiotherapy Oncology, 100, 412-416.
4. Taupin F. et al. (2015) Gadolinium nanoparticles and contrast agents as radiation sensitizers.
Physics in Medicine and Biology, 60, 4449-64.
5. Perl, J. et al. (2012) TOPAS: an innovative proton Monte Carlo platform for research and clinical
applications. Med Phys., 39, 6818-37.
Fig. 1. cluster of
nanoparticles randomly
distributed.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
31
P9: New Explanation for Radiosensitization by Gold Nanoparticles:
Chemical Effect
V. Shcherbakov, N. Chen, S.A. Denisov and M. Mostafavi
Laboratory of chemical physics/CNRS_Université Paris-Saclay, Orsay, France
Gold nanoparticles (AuNPs) are presented to be an efficient radiosensitizer for cancer
radiotherapy [1]. During the last decades, many important works were performed to show the
radiosensitization by different particles for different tumors. But still, there is no explanation
for AuNPs radiosensitizating effect. Physical explanation based on Compton, photoelectric and
Auger effects cannot explain the radiosensitizing effect in solutions, because the nanomolar
concentration of AuNPs does not change dose deposition in the solution. Therefore, other ideas
were proposed such as overproduction of ∙OH radicals [2] due to special properties of
interfacial water around nanoparticles and
scavenging of excess electrons [3, 4] what
increases the concentration of ∙OH radicals
around the nanoparticles.
In the present work, we show by pulse radiolysis
that AuNPs react neither with reducing radicals:
pre-solvated electron, solvated electron (e-s), ∙H
nor oxidizing one ∙OH, what is manifested in the
same e-s formation yields (5 ps) in the presence
and absence of AuNPs; and the same decay of e-
s in microsecond time range [5]. In addition,
unchanged e-s decay in the presence of AuNPs
showed that overproduction of OH radicals is not
occurring. In the present work we perform a new
approach to show the effect of AuNPs in
radiosensitization.
As biological systems are complex, therefore here we used simple organic models to conclude
on the mechanism of the radiosensitizing effect of AuNPs. By gamma radiolysis, we show that
in an irradiated solution of 2-propanol in the presence of AuNPs the radiolytic yield of acetone
– the product of oxidation of alcohol, is higher than in the absence of nanoparticles (Figure 1).
Such studies were carried out for other organic compounds in order to confirm the effect of
gold nanoparticles on this radiolytic enhancement. In our work we will propose the detailed
mechanism and discuss how it can explain radiosentisization by AuNPs.
References:
1. Wang, H., Mu, X., He, H., & Zhang, X. D. (2018). Cancer radiosensitizers. Trends in pharmacological sciences, 39(1), 24-48.
2. Gilles, M., Brun, E., & Sicard-Roselli, C. (2018). Quantification of hydroxyl radicals and solvated
electrons produced by irradiated gold nanoparticles suggests a crucial role of interfacial water.
Journal of colloid and interface science, 525, 31-38.
3. Ghandi, K., Wang, F., Landry, C., & Mostafavi, M. (2018). Naked Gold Nanoparticles and hot
Electrons in Water. Scientific reports, 8(1), 7258.
4. Ghandi, K., Findlater, A. D., Mahimwalla, Z., MacNeil, C. S., Awoonor-Williams, E., Zahariev, F.,
& Gordon, M. S. (2015). Ultra-fast electron capture by electrosterically-stabilized gold nanoparticles.
Nanoscale, 7(27), 11545-11551.
5. Shcherbakov, V., Denisov, S.A., Ghandi, K., Mostafavi, M., Pulse radiolysis study of AuNPs
solutions. (to be published)
Figure 1. The dose dependent of acetone
formation in 2-propanol solution in the
presence and absence of AuNPs.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
32
I11: Oxygen Effects on Antioxidant Protection of Lymphoid Cells against
Free Radicals by a Range of Dietary Carotenoids
R. Edge1, F. Boehm2 and T.G. Truscott3
1Dalton Cumbrian Facility, The University of Manchester, Westlakes Science Park, Moor Row, Cumbria, UK;
2Photobiology Research, IHZ, Berlin, Germany; 3School of Physical Science (Chemistry), Keele University, Staffordshire, UK.
Carotenoids are natural pigments, being constituents of a wide variety of fruits and vegetables,
though chlorophyll often masks their presence. Believed to act as dietary antioxidants, having
been shown to quench both singlet oxygen and a range of free radicals, carotenoids are of
interest for their health benefits. While carotenoids are consumed in significant quantities from
normal diets, in recent years, they are also consumed in large quantities via food supplements.
This may well be based on claims that they offer major health benefits but there are also
counter-claims that they can be damaging to human health.
We have shown previously that dietary lycopene, the red carotenoid pigment in tomatoes,
protects against human lymphoid cell membrane damage from free radicals produced by γ-
radiation and that this protection is dramatically reduced when the oxygen concentration is
increased [1].
In this work we study a wider range of dietary carotenoids, showing protection of human
lymphoid cells from membrane damage caused by free radicals produced by γ-radiation. Blood
was taken from volunteers who had supplemented their diet with large doses of a specific
carotenoid for 2 weeks or had minimized carotenoid-rich fruit and vegetables in their diet.
Radical-induced cell membrane destruction was shown by cell staining with eosin.
All carotenoids studied imparted protective effects and the carotenoid protective effect was
reduced as oxygen concentration increased, as previously seen for lycopene. In fact, the oxygen
effect was observed to be most pronounced for lycopene, where there was almost no protection
under 100% oxygen, down from 5-fold protection at 21% oxygen and, an extremely high, 50-
fold, protection in the absence of oxygen. Studies with β-carotene and the xanthophylls,
astaxanthin, zeaxanthin and lutein, have shown a reduced, but still significant, oxygen effect.
Gamma radiation cellular studies have also been undertaken with the addition of superoxide
dismutase, showing that the effect is not due to reactions of the superoxide radical.
Additionally, a series of non-cellular gamma radiolysis studies in simple solutions, as well as
cell protection studies against nitrogen dioxide radical, generated photolytically, have also been
carried out to help elucidate the molecular mechanisms for the observed oxygen effect.
The remarkable reduction in protection by carotenoids, particularly lycopene, against gamma
radiation at high oxygen concentrations could, perhaps, be exploited to enhance radiation
procedures for therapy.
References
1. Boehm, F., Edge, R., Truscott, T.G. and Witt, C. (2016) A dramatic effect of oxygen on protection
of human cells against γ-radiation by lycopene. FEBS Lett., 590, 1086-1093.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
33
P10: Effects of Additives on Radiation-Induced DNA Damage: From the
Viewpoints of Free Radical Scavenging and Chemical Repair
H. Yu1, K. Fujii2, A. Yokoya2 and S. Yamashita1
1The University of Tokyo, Tokyo, JAPAN; 2Natinal Institutes for Quantum and Radiological Science and Technology (QST), Chiba, JAPAN.
1. INTRODUCTION
Radiation-induced DNA damage can be reduced by small amount of additives like
antioxidants. Such additives can repair unstable oxidative damage intermediately produced in
DNA by reductive reaction (chemical repair) as well as remove oxidizing radicals such as •OH
produced as a result of water radiolysis (radical scavenging). Low concentration of additives
cannot remove all of the oxidizing radicals, therefore, the chemical repair process must be more
important. We investigated the effect of additives against radiation damage to DNA. For this
purpose, pulse radiolysis experiments were conducted to observe the additive’s reactions not
only with radicals produced by water radiolysis but also with a tentatively oxidized DNA model
compound. In this study, dGMP (deoxyguanosine monophosphate, purchased from Thermo
Fisher Scientific) was used as model compound of DNA moiety. In addition, a gel
electrophoresis was conducted to evaluate the yield of stable DNA damage.
2. EXPERIMENT
Pulse radiolysis was conducted at the LINAC facility of the University of Tokyo. Details of
the apparatus are described in elsewhere[1].
Plasmid DNA, pUC18, was extracted from cultured Escherichia coli (JM109) and purified
by dialysis to remove organic impurities. Dilute aqueous solutions and films of the plasmid
DNA were irradiated with X-rays and stable DNA damage were detected and quantified by an
agarose gel electrophoresis method[2].
As additives, we used Tris-EDTA (TE), which are the solutes of pH buffer often used for
DNA storage, and typical antioxidants such as ascorbic acid (purchased from Fujifilm Wako)
and flavonoid rutin (received from Toyo Sugar or purchased from Fujifilm Wako).
3. RESULTS & DISCUSSION
Transient absorption spectra of the scavenging reaction of rutin toward •OH had at least three
peaks, which were attributed to the products of OH adduct, hydrogen atom subtraction, and
electron subtraction. The ratio of the peak intensities was not constant, indicating an
intramolecular transformaton following the scavenging reaction. On the other hand, the reacion
of rutin toward tentatively oxidized dGMP radical showed a clear peak in the spectra, which
was the same as the peak corresponding to hydrogen abstraction observed for the scavenging
reaction as described above.
Purification by dialysis resulted in higher yields of stable DNA damage induction, indicating
that non-negligible impurities could protect the DNA from radiation damage. The damage
yields in dilute aqueous solutions were much higher than those in hydrated plasmid DNA films.
This suggests that additional damage is produced due to the indireact actions of radicals
produced by watar radiolysis.
References
[1] K. Hata, et al., J. Radiat. Res., 52, 15 (2011).
[2] A. Yokoya et. Al., J. Am. Chem. Soc. 124, 8859 (2002).
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
34
P11: Solvation Effects on Dissociative Electron Attachment to Thymine
Jorge Kohanoff 1 and Bin Gu1,2
1Atomistic Simulation Centre, Queen’s University Belfast, Belfast BT7 1NN, U.K.; 2Department of Physics, Nanjing University of Information Science and Technology, Nanjing 210044,
China.
Ionizing radiation can excite the cellular medium to produce secondary electrons that can
subsequently cause damage to DNA. The damage is believed to occur via dissociative electron
attachment (DEA). In DEA, the electron is captured by a molecule in a resonant antibonding
state and a transient negative ion is formed. If this ion survives against electron
autodetachment, then bonds within the molecule may dissociate as energy is transferred from
the electronic degrees of freedom into vibrational modes of the molecule.
We present a model for studying the effect that transferring kinetic energy into the vibrational
modes of a molecule has on a DNA nucleobase. To simulate the effect of the additional energy
that would be introduced due to a DEA event, we vertically attached an excess electron to the
system and introduced additional vibrational energy to the N−H bond. We can tune the
vibrational energy of a molecular bond by increasing the velocities and hence the kinetic
energies of the constituent atoms.
We found that the breaking of an N−H bond and releasing a hydrogen atom, which in the gas
phase requires 1.67 eV, is strongly affected by the aqueous environment. When there is a
hydrogen bond between the N−H of the nucleobase and a surrounding water molecule, there is
no guarantee that the bond breaks even when up to 5 eV of additional energy is inserted into
the bond. The reason for this is that this hydrogen bond rapidly channels the kinetic energy
away from the N−H, into the surrounding water molecules, and back into the nucleobase.
Fig. 1 The reaction channels of the (Transient negative ion) TNI of thymine with low energy
dissociative electron attachment (DEA) in aqueous solvent, with the relevant potential energy surface
(PES) shown as functions of the N-H distance.
Reference
McAllister, M., Kazemigazestane, N., Henry, L. T., Gu, B., Fabrikant, I., Tribello, G. A., & Kohanoff,
J. (2019). Solvation Effects on Dissociative Electron Attachment to Thymine. The Journal of Physical
Chemistry B, 123(7), 1537–1544.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
35
FRIDAY 13th SEPTEMBER
08:00 Sunrise Session - Energy, Chaired by Robin Orr and Dan Whittaker
09:00
09:35
10:10
10:35
Energy–I Session, Chair - Robin Orr
I12: “Rapid Capture of Holes in Organic Solvents Studied by Picosecond Pulse-
Radiolysis” Andrew Cook
I13: “Radiation Energy Transfer Simulation toward Extraction Solvent in Minor
Actinide Separation Process” Tomohiro Toigawa
P12: “Effect of Supports on Metal-Nanoparticle Catalysts: The Radiolytic H2
Evolution Reaction” Tomer Zidki
P13: “Radiation-Induced Redox Chemistry of Californium-249” David Meeker
11:00 Coffee
11:30
12:05
12:40
Energy–II Session, Chair - Dan Whittaker
I14: “Capturing Sunlight with Molecular Systems – A Pulse Radiolysis
Investigation into Charge Recombination and Escape for Solar Energy
Conversion” Matthew Bird
I15: “Drastic Changes in the Surface Reactivity of UO2-Based Spent Nuclear Fuel
upon Exposure to Radiolytic Oxidants – How Will This Influence the Safety
Assessment of Deep Geological Repositories for Spent Nuclear Fuel?” Mats
Jonsson
P14: “Reduction of Cobaoxime-Based Complexes: Mechanisms, Products and
Implications” Axel Kahnt
13:05 Lunch
14:00 Educational Session – Materials, Laura Leay and Clelia Dispenza
15:00
15:35
16:10
16:35
Materials-I Session – Chair, Clelia Dispenza
I16: “Heterogeneous Alteration of a Mimas MOX Fuel under Oxidizing
Conditions Revealed by Raman Spectroscopy” Lola Sarrasin
I17: “Heavy Ion-Induced Defect Production in Single-, Few-Layer and Bulk
Crystals of MoS2” Liam Isherwood
P15: “γ-Radiolysis of Thermal Transition Phases in Boehmite” Patricia Huestis
P16: “Key Role of the Oxidized Citrate Free Radical in the Nucleation
Mechanism of the Metal Nanoparticles Turkevich Synthesis” Sarah Al Gharib
17:00 Coffee
17:30
18:05
18:30
Materials-II Session, Chair Laura Leay
I18: “The Effects of Gamma Radiation on the Accelerated Carbonation of Fly-
Ash Blended Cement” Alex Potts
P17: “The Radiation Chemistry of Aqueous PVP Solutions Exposed to Pulsed E-
beam Irradiation: Experiments and Numerical Simulations” Clelia Dispenza
P18: “Internal Structure and Composition of Fukushima-Derived Particulate
Revealed through Combined Synchrotron and Mass-Spectrometry Techniques”
Peter Martin
18:55 Conference Closing Remarks
19:00 Coaches to Cockermouth
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
36
I12: Rapid Capture of Holes in Organic Solvents Studied by Picosecond
Pulse-Radiolysis
Andrew R. Cook and John R. Miller
Brookhaven National Laboratory, Upton NY, USA.
In comparison to water, little is known about the diverse radiation chemistry presented
by organic solvents. We are particularly interested in the early-time (sub-ns to ns) chemistry
of holes (radical cations) formed by radiolysis: What is their nature, what can they oxidize, and
how fast? How do these processes shape long-time chemistry? Holes in organic liquids are
known to fragment, rapidly in some cases. Can we learn to control or block this chemistry?
The work that I will describe focuses on understanding ways to oxidize of solutes after
radiolysis very rapidly, to enable picosecond observation of processes like charge transfer and
transport. Holes produced by radiolysis have typically been considered as molecular ions that
move by diffusion, a slow process. While electrons in some liquids are known to be captured
at rates exceeding 1013 M-1s-1, as well as prior to solvation under certain circumstances, such
mechanisms are not generally known for holes. This work challenges the long-held perception
of the nature of holes at early times in organic liquids and finds substantial sub-15 ps capture.
I will show examples in 3 different classes of organic solvents: those known to form
solute radical cations only (chloroform), those where they are normally not formed (THF), and
those known to form both solute anions and cations (alkanes). The common finding in all 3
media is that there are solute radical cations formed within our ~10-15 ps time resolution at the
Laser Electron Accelerator Facility (LEAF, BNL).
The figure shows an example in n-pentane. The
sudden or “step” increase in transient absorption at
t~0 is due to the < 15 ps production of solute radical
cations and is followed by an additional growth due
to normal diffusion. This “step capture” produces
solute+● much faster than diffusion, with substantial
yields. We would like to understand the mechanism
by which it occurs, and whether it might play a
fundamental role in radiolysis. Data have been
successfully modeled using formalisms previously
used for the capture of pre-solvated electrons,
suggesting that there may be parallel mechanisms
for holes. I find that the efficiency of this process
rivals that for pre-solvated electrons in chloroform
and alkanes, and the models give average capture distances across multiple solvent molecules
in these solvents, while in THF is limited to capture from nearest neighbors.
Work thus far suggest that the process may be best described as capture of the precursor
to solvent radical cations, likely a form of pre-solvated holes. As such, it likely is important in
a wider variety of media, particularly when solute concentration is large. I will show some
examples of how this has manifested in our work in charge transport projects, and how it might
be used to produce desired solute radical cations in media like ethers and possibly block
fragmentation of holes.
Ref: Cook, A. R.; Bird, M. J.; Asaoka, S.; Miller, J. R. J. Phys. Chem. A 2013, 117, 7712-7720.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
37
I13: Radiation Energy Transfer Simulation toward Extraction Solvent in
Minor Actinide Separation Process
T. Toigawa, Y. Tsubata, T. Kai, T. Furuta, Y. Kumagai, T. Matsumura
Japan Atomic Energy Agency, Ibaraki, Japan.
The long-term radioactive toxicity of high-level liquid waste (HLLW) mainly depends on
minor actinides (MAs: Am and Cm). For the reduction of the toxicity, Japan Atomic Energy
Agency developed a highly effective extraction ligand, N,N,N’,N’-tetraoctyl diglycolamide
(TODGA), which can extract MAs and lanthanides from nitric acid media [1]. The radiation
stability of TODGA has also been studied in terms of the radiation chemical information such
as the degradation yield of TODGA or the changes of the extraction ability for MAs. However,
the radiation dose absorbed by the extraction solvent containing TODGA is still unclear in a
real MA separation process because of the experimental difficulty of the dosimetry. Therefore,
it is necessary to estimate the absorbed dose supposing actual conditions of the process. In the
extraction process, the extraction solvent is vigorously stirred with HLLW containing various
radionuclides and forms inhomogeneous oil-water mixture. This mixed state is expected to
affect the absorbed dose distribution because the scale of the mixed state may be comparable
with the ranges of α-rays and low-energy electrons. A reliable estimation should take into
consideration this effect as well as the concentrations of radioactive nuclides in the HLLW and
their decay modes. In this study, we focused on
this radiation permeability effects on the
separation process. A radiation energy transfer
simulation in the inhomogeneous structures was
performed with the aid of the Monte Carlo
radiation transport code, PHITS [3].
The extraction solvent and the HLLW were
assumed as 0.1 M TODGA-dodecane solution
and 3 M nitric acid aqueous solution. The
radioactive concentrations in HLLW were 1.7 ×
1011, 1.6 × 1013 and 7.5 × 1012 Bq/L for α-, β- and
γ-ray emitters, respectively. Fig. 1 shows the
calculation result of the absorbed dose rate in the
extraction solvent as a function of the dispersed droplet size in the infinitely spread emulsion.
If the droplet size was significantly small compared to the radiation travel distance, the ratio of
energy deposition to the extraction solvent and the HLLW seems to be homogeneous. Because
TODGA extracted almost all the α-emitters and the strong β-emitters such as 90Y, and 144Pr,
the absorbed dose for α- and β-ray increased with the droplet size after extraction. On the other
hand, the absorbed dose for γ-ray decreased with the droplet size because the γ-emitters were
not extracted by TODGA. The absorbed dose for γ-ray was mainly due to the contribution of
the γ-emitters remaining in the HLLW. A significant contribution of low LET radiation for the
extraction solvent was pointed out in terms of the absorbed dose.
References
1. Sasaki, Y. et al. (2007) Extraction of Various Metal Ions from Nitric Acid to n-dodecanen by
Diglycolamide (DGA) Compounds, J. Nucl. Sci. Tech., 44, 405-09
2. Sugo, Y. et al. (2009) Radiolysis study of actinide complexing agent by irradiation with helium ion
beam, Radiat. Phys. Chem., 78, 1140-114
3. Sato, T. et al. (2018) Features of Particle and Heavy Ion Transport code System (PHITS) version
3.02, J. Nucl. Sci. Technol., 55, 684-690
Figure 1 absorbed dose rate in the extraction solvent mixed with the HLLW.
3000
2000
1000
0
Ab
so
rbe
d d
ose
in
org
an
ic p
ha
se
/ G
y h
-1
1 µm 10 µm 100 µm 1 mm 10 mm 100 mm 1 m
Droplet diameter
Alpha
Beta Gamma
before extraction
after extraction
after extraction
before extraction
after extraction
before extraction
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
38
P12: Effect of Supports on Metal-Nanoparticle Catalysts: The Radiolytic
H2 Evolution Reaction
Gifty Sara Rolly,1 Ronen Bar-Ziv 2 and Tomer Zidki 1
1Department of Chemical Sciences, Ariel University, Ariel, Israel; 2Department of Chemistry, Nuclear Research Centre Negev, Beer-Sheva, Israel.
The performance of the silica-supported M0 nanoparticles as catalysts for water reduction was
studied using the strongly-reducing ·C(CH3)2OH radicals at acidic and alkaline media. It was
found that supporting metal nanoparticles (M0-NPs, M = Pt, Au, Ag) on an "inert" support such
as SiO2 alters the catalytic properties of the metals. This effect depends both on the nature of
M and on the concentration of the composite nanoparticles. At low nanocomposite
concentration: for M = Au nearly no effect is observed; for M = Ag the support decreases the
catalytic reduction of water, and for M = Pt the support initiates the catalytic process. At high
nanocomposite concentration: for M = Au the reactivity is considerably lower, and for M = Ag
or Pt, no catalysis is observed. Furthermore, for M = Ag or Pt H2 reduces the ·C(CH3)2OH
radicals. Changing the medium from alkaline to acidic pH did not affect these trends.
Therefore, we conclude that the metal oxide support affects the M0-NPs redox properties.
Below is the proposed mechanism pathways for the production of H2 and the deactivation of
H2 evolution.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
39
P13: Radiation-Induced Redox Chemistry of Californium-249
David S. Meeker1,2, Gregory P. Horne1, Travis S. Grimes1, Peter R. Zalupski1, James F. Wishart3,
Stephen P. Mezyk4, and Thomas E. Albrecht-Schmitt2
1 Idaho National Laboratory, Center for Radiation Chemistry Research, Idaho Falls, ID, P.O. Box
1625, 83415, USA 2 Florida State University, Department of Chemistry and Biochemistry, Tallahassee, FL, 32306-4390,
USA. 3 Brookhaven National Laboratory, Department of Chemistry, Upton, New York, 11973, USA.
4`California State University Long Beach, Department of Chemistry and Biochemistry, Long Beach,
CA 90804, USA.
A complete understanding of californium chemistry necessitates knowledge of its
radiation-induced redox behavior, owing to its inherent nuclear instability propagating self-
radiolysis. Only a handful of studies have investigated californium radiation chemistry, due to
lack of element availability and difficulty associated with handling highly radioactive material.
To date, reaction rate coefficients (k) have only been experimentally determined for the
reduction of Cf(III) by the hydrated electron (e¯aq, k > 3 × 109 M–1 s–1) from water radiolysis,
and subsequent decay of the corresponding transient Cf(II) (k = (7 ± 1) × 105 s–1)[1]. However,
there are a number of other important transient radiolysis products radiolytically generated in
solutions pertinent to californium manipulations, e.g., the hydrogen atom (H•, Eo = 2.31 V),
hydroxyl radical (•OH, Eo = –2.73 V), and nitrate radical (•NO3, Eo = –2.3 – –2.6 V). These
species are more than capable of influencing the redox behavior of californium, and have been
shown to do so with a number of actinides, e.g., neptunium and americium.[1,1,1] Here we
present the results from the first time-resolved picosecond pulsed electron radiolysis
measurements for californium-249. The reaction rate coefficients were determined by direct
decay of the observed species or via competition kinetics. For the reductive reactions of Cf(III)
with the e¯aq and H• transients, the reaction rate coefficients were measured to be (7.11 ± 0.18)
× 1010 and (2.61 ± 0.54) × 108 M−1 s−1, respectively, while studies for the oxidation of Cf(III)
by the •NO3 and •OH species yielded (2.0 ± 0.5) × 108 and (7.2 ± 0.6) × 108 M−1 s−1, respectively
References
1. Sullivan, J.; Morss, L.; Schmidt, K.; Mulac, W.; Gordon, S. Pulse Radiolysis Studies of
Californium (III) in Aqueous Perchlorate Solution. Evidence for the Preparation of Californium
(II). Inorg. Chem., 1983, 22, 2339.
2. Horne, G. P.; Grimes, T. S.; Mincher, B. J.; Mezyk, S. P. Re-evaluation of Neptunium-Nitric
Acid Chemistry by Multi-Scale Modelling. Journal of Physical Chemistry B, 2016, 120 (49),
12643–12649.
3. Grimes, T. S.; Horne, G. P.; Dares, C. J.; Pimblott, S. M.; Mezyk, S. P.; Mincher, B. J. Kinetics
of the Autoreduction of Hexavalent Americium in Aqueous Nitric Acid. Inorganic Chemistry,
2017, 56 (14), 8295-8301.
4. Horne, G. P.; Grimes, T. S.; Bauer, W. F.; Dares, C. J.; Pimblott, S. M.; Mezyk, S. P.; Mincher,
B. J., Effect of Ionizing Radiation on the Redox Chemistry of Penta- and Hexavalent
Americium. Inorganic Chemistry, submitted 28th March 2019.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
40
I14: Capturing Sunlight with Molecular Systems – A Pulse Radiolysis
Investigation into Charge Recombination and Escape for Solar Energy
Conversion
M. Jilek1, J. Keiper2, J. Burke3 and M. Bird4
1University of Colorado Boulder, CO 80309-0215 Boulder, CO, USA. 2Penn State University, University Park, PA 16802, USA.
3University of Illinois at Urbana–Champaign, 505 South Mathews Avenue
Urbana, IL 61801, USA. 4Brookhaven National Laboratory, Upton, NY 11973, USA.
Solar cells based on thin films of donor (D) and
acceptor (A) molecules (organic photovoltaics) have
recently reached power conversion efficiencies as high
16.5 % [1]. This remarkable performance occurs
despite the fact that photogenerated charge pairs, in a
nonpolar film, should have difficulty escaping their
mutual coulombic attraction to reach the electrodes.
These materials are typically highly conjugated,
allowing for significant charge delocalization. While
some general material design rules have been
established, there is still a lack of basic understanding
about the exact role of delocalization, spin, and local
excited states in non-radiative charge recombination;
the main source of energy loss in these devices.
Information about charge recombination and escape
can obtained from photoinduced absorption (PIA) of
DA films but this has limitations inherent to the
disordered nature of films. Pulse radiolysis offers a
complementary technique where fundamental steps
can be isolated and studied in the similar environment
of nonpolar solvents.
Pulse radiolysis enables a known concentration of charges and/or excited states to be rapidly
created in the solvent, regardless of what the solute is. With transient absorption spectroscopy
(TAS) in the UVvis/nearIR/microwave, the rate of transfer of energy and/or charge to the solute
and between solutes can be studied.
We have used pulse radiolysis to learn about the thermodynamics and kinetics of charge pair
formation and recombination. We have investigated the role of spin in charge recombination
be looking at recombination of charge pairs with energy above and below local triplet excited
states (green and red respectively in figure 1). We have found some surprisingly long lifetimes
of microseconds for some radical cation and anion pairs.
We complement these pulse radiolysis techniques with ground state charge transfer
experiments to study the electrostatic interaction between delocalized charges in conjugated
polymers. We have also determined the thermodynamics of electron transfer and escape when
one of the charges is highly delocalized in conjugated polymer “nanowire” aggregates.[2]
Reference(s)
1. https://www.nrel.gov/pv/assets/pdfs/best-research-cell-efficiencies.20190802.pdf
2. J. H. Burke, M. J. Bird, Adv. Mater. 2019, 1806863
Figure 1. Transient absorption of
fluorene (F1) cations as they
recombine with benzoquinone (BQ)
or tetracyanoethylene (TCNE) anions
following pulse radiolysis.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
41
I15: Drastic Changes in the Surface Reactivity of UO2-Based Spent Nuclear
Fuel upon Exposure to Radiolytic Oxidants – How Will This Influence the
Safety Assessment of Deep Geological Repositories for Spent Nuclear Fuel?
A. C. Maier and M. Jonsson*
Department of Chemistry, KTH Royal Institute of Technology, Stockholm, Sweden
Several countries plan to store their spent nuclear fuel in deep geological repositories for
extremely long time periods (>100000 years). This calls for rather extreme safety assessments
accounting for a multitude of possible scenarios. A commonly used scenario is groundwater
intrusion into a fuel canister after 1000 years. Since UO2 (the matrix of the most commonly
occurring spent nuclear fuel) has very low solubility in the reducing groundwater expected to
be found at the depth of a typical repository, the main process driving the fuel matrix
dissolution and the subsequent release of fission products and heavier actinides is radiolysis of
groundwater. The oxidants produced upon radiolysis of groundwater are capable of oxidizing
U(IV) to the considerably more soluble U(VI) and thereby solubilize the fuel matrix. Previous
studies have shown that the most important oxidant in these systems is H2O2. To assess the
long-term leaching behavior of UO2, the oxidative dissolution of UO2 pellets was studied at
high H2O2 exposures (expressed as amount of oxidant consumed per surface area) ranging from
0.3 mol m-2 to 1.4 mol m-2. The results indicate that the dissolution yield (amount of dissolved
uranium per consumed H2O2) at high H2O2 exposures is significantly lower compared to
previous studies of both pellets and powders and decreases for each H2O2 addition for a given
pellet. This implies a change in redox reactivity by a factor of three to four, which is attributed
to irreversible alteration of the pellet surface. Surface characterization after the exposure to
H2O2, by SEM, XRD and Raman spectroscopy show, that the surface of all pellets is
significantly oxidized.
The same type of study was also performed on Gd-doped UO2 (Gd is used as a burnable neutron
absorber in commercial nuclear fuel) revealing similar trends at different doping levels. The
results of the studies performed on pure UO2-pellets and Gd-doped UO2-pellets are discussed
in combination with relatively recent findings on the reactivity of UO2-powder (exposed to
H2O2 as well as ionizing radiation) as a function of stoichiometry. Finally, the overall impact
of these findings on the safety assessment for deep geological repositories for spent nuclear
fuel is discussed.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
42
P14: Reduction of Cobaoxime-Based Complexes: Mechanisms, Products
and Implications
A. Kahnt1, E. Hofmeister2, T. Ullrich3, K. Hanus1 and M. von Delius2
1Leibniz Institute of Surface Engineering (IOM), Leipzig, Germany. 2Institute of Organic Chemistry and Advanced Materials, University of Ulm, Ulm, Germany.
3Chair of Physical Chemistry I, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
Cobaltoxime based complexes have attracted strong interest in the past and present. Decades
ago the focus was set on alkyl and alkenyl cobaloximes as vitamin B12 model system1. Later,
new interest arose regarding this class of compounds owing to the fact that Co(dmgBF2)2
catalyses the reduction of protons in acidic solutions.2 In this regard, cobaloxime complexes
are considered as candidates for the “Holy Grail” in the field of renewable energy - that is the
formation of renewable fuel from solar energy, to potentially meet the future energy demands
without the use of fossil fuel. Several cobaltoxime based systems containing organic and/or
inorganic chromophores3 for light harvesting have been coordinated to the cobalt centre of
cobaloxime complexes and have been successfully tested for the photocatalytic reduction of
water.
But, plenty of this systems prompt to a up to hours lasting induction period for the
photocatalytic reduction of water.4 Surprisingly, the reasons for such a phenomenon remain
largely unknown4 and comes hardly in line with the usual
proposed reaction mechanisms postulating a reduction
from a CoIII to a CoI species. Our past work5,6 related to
photocatalytic water reduction triggered our interest in the
understanding of this mechanism. In line with the latter,
we conducted a full fledge spectroscopic and kinetic
investigation of the reduction of mono-nuclear Co-
complexes by pulse radiolysis assays, however, we found
solid evidence that a final product of the reduction process
was a dinuclear complex.6 From this finding we derived
the implication that for an efficient induction period free
photo-catalysts least two Co-centres like in the CoIII double salt presented in figure 1 are
required. For these new and very efficient class of proton reduction photo-catalysts detailed
investigations of the reduction mechanism by pulse radiolysis were conducted in order to
establish the mechanism behind the found quite efficient proton reduction.7
Reference(s) 1. Prince R.H., Segal, M.G. (1974) Nature, 249, 246-247.
2. Connolly P., Espensson J.H. (1986) Inorg. Chem., 25, 2684-2688.
3. Artero V., Fontecave M. (2013) Chem. Soc. Rev., 42, 2338-2356.
4. Du P., Eisenberg R. (2012) Energy Environ. Sci., 5, 6012-6021.
5. Peuntinger K., Lazarides T., Daphnomili D., Charalambidis G., Landrou G., Kahnt A., Sabatini R.,
McCamant D., Gryko D.T., Coutsolelos A., Guldi D. M. (2013) J. Phys. Chem. C, 117, 1647-1655.
6. Kahnt A., Peuntinger K., Dammann C., Drewello T., Hermann R., Naumov S., Abel B., Guldi D.
M. (2014) J. Phys. Chem. A, 118, 4382-4391.
7. Hofmeister, E., Ullrich, T., Petermann L., Hanus, K., Rau, S., Kahnt, A., von Delius, M. (2019)
Angew. Chem. Int. Ed., under preparation.
Figure1. New generation of
Co-double salts as core
structure for novel proton
reduction photo-catalysts [7].
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
43
I16: Heterogeneous Alteration of a Mimas MOX Fuel under Oxidizing
Conditions Revealed by Raman Spectroscopy
L. Sarrasin, S. Miro, C. Jégou, V. Broudic, C. Marques, M. Tribet, S. Peuget
Commissariat à l’Énergie Atomique (CEA), Marcoule Research Center, BP 17171, F-30207 Bagnols-sur-Cèze Cedex, France
In view of interim wet storage of MOX fuel assemblies for several decades the prospect of a
through-wall cladding defect must be considered. In the event of a failed fuel rod, the main
objective is to determine the potential impact of the formation of secondary phases or an
oxidized layer on the mechanical properties of the cladding. The irradiation conditions
expected in a fuel storage pool (high dose rate in the fuel assembly and contact with aerated
water) will be favorable to the recombination kinetics in favor of the molecular species like
hydrogen peroxide liable to enhance oxidizing dissolution of the fuel matrix near the defect.
Un-irradiated heterogeneous MOX07 pellets (MIMAS MOX 7% Pu/(U+Pu)) were leached in
aerated water under a gamma source (60Co) in a hot cell in order to reproduce as closely as
possible the radiation field inside a fuel assembly. The initial microstructure observed on this
type of MOX fuel revealed the presence of different zones with different Pu contents arising
from the fabrication process. The leachate was regularly sampled for elemental and
radiochemical analysis, the pH and redox potential were measured and hydrogen peroxide, a
molecular product generated by water radiolysis, was analyzed. The MOX samples were
analysed using Raman spectroscopy over time during the 3 months of the leaching experiments.
Localized and punctual spectra as well as mappings of the samples were acquired in order to
follow the surface’s evolution and link it to the local heterogeneities of the MOX
microstructure. This experiment was followed by a second one performed under the same
experimental conditions but with an enriched water at 97% in 18O. The Raman spectroscopy
being sensitive to mass variations, the 18O of this experiment acts as a marker for the oxidation
and/or phase formation at the sample’s surface.
We have demonstrated thanks to Raman mappings the heterogeneity of the alteration through
a preferential corrosion of the UO2 grains and through the local formation of secondary phases.
The uranium-rich zones are dissolved prior to Pu-rich aggregates, which creates holes at the
surface of the samples. These holes are preferential sites for the precipitation of studtite that
covers the whole surface in the long term. To better understand the mechanisms of studtite
formation and oxidation, marked water was used. The first results are presented and discussed.
Figure 1: Heterogeneous precipitation of studtite on U-rich zones of a MOX07 sample after 20
days of leaching; a) optical image b) Raman mapping and c) Raman spectra of the surface
200 400 600 800 1000 1200 1400 1600
Inte
nsi
ty (
a.u
.)
Wavenumbers (cm-1)
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
44
I17: Heavy Ion-Induced Defect Production in Single-, Few-Layer and Bulk
Crystals of MoS2
Liam H. Isherwood,1,2 Cinzia Casiraghi1 and Aliaksandr Baidak1,2
1 Chemistry Department, School of Natural Sciences, University of Manchester, Manchester, M13 9PL, United Kingdom
2 Dalton Cumbrian Facility, University of Manchester, Westlakes Science Park, Cumbria, CA24 3HA,
United Kingdom
Two-dimensional (2D) MoS2 has attracted
a great deal of research interest on account of its
1.9 eV direct bandgap and catalytically active
edge sites which make it a promising candidate
for flexible and transparent (opto)electronic
devices [1] as well as catalytic applications [2].
Ion beam-mediated defect engineering is a
powerful tool to tailor the properties of 2D
MoS2 [3] on account of its unique spatial
resolution and the plethora of ion types and
energies available. In order to fully realise the
potential of this technique, a holistic
understanding of ion-induced defect production
in MoS2 is required.
This presentation will evaluate defect production in monolayer MoS2 fabricated by both
micromechanical exfoliation (MME) and chemical vapour deposition (CVD) as well as MoS2
crystals of various thicknesses. Raman spectroscopy, x-ray photoelectron spectroscopy and
electron diffraction are used to characterise the radiation-induced changes in MoS2 crystals
under 225 keV Xe+ ion irradiation.
All three techniques show that the rate of defect production is inversely proportional the
thickness of the crystal whilst Raman spectroscopy shows that the rate is comparable for
monolayer MoS2 produced by either MME or CVD. Both monolayer and bulk MoS2 become
p-doped after irradiation and the out-of-plane vibrational properties of defective MoS2 are
progressively dominated by interlayer interactions in thicker crystals. Specifically, the
frequency of the out-of-plane 𝐴1𝑔 mode blueshifts in monolayer MoS2 due to phonon
confinement effects whilst a redshift is observed in bulk MoS2 and is attributed to attenuation
of the effective restoring forces acting on S atoms due to reduced interlayer interactions (Fig.
1). Moreover, the phonon lifetime of this mode is increased in irradiated few-layer MoS2 and
is tentatively attributed radiation-induced decoupling of the individual monolayers.
Our results further support the use of ion beams for defect engineering of MoS2 and offer
valuable insights into how the dimensionality of layered crystals influences the evolution of
their electronic, vibrational and structural properties under heavy ion irradiation.
References:
1. De Fazio, D., Goykhman, I., Yoon, D., Bruna, M., Eiden, A., Milana, S., Sassi, U., Barbone, M.,
Dumcenco, D., Marinov. K., Kis, A. and Ferrari, A.C., (2016), ACS Nano, 10, pp. 8252-8262
2. Xie, J., Zhang, H., Li, S., Wang, R., Sun, X., Zhou, M., Zhou, J., Wen, X., Lou, D. and Xie, Y.,
(2013), Adv. Mater., 25, pp. 5807-5813 3. He, Z., Zhao, R., Chen, X., Chen, H., Zhu, Y., Su., H., Huang, S., Xue, J., Dai, J., Cheng, S., Liu, M.,
Wang, X. and Chen, Y., (2018), ACS Appl. Mater. Interfaces, 10, pp. 42524-42533
Figure 5: The relative frequency shift (∆𝜈) of the out-
of-plane 𝐴1𝑔 mode of monolayer MoS2 (2D MoS2) and
bulk MoS2 (3D MoS2) crystals, produced by
micromechanical exfoliation, as a function of radiation
exposure.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
45
P15: γ-Radiolysis of Thermal Transition Phases in Boehmite
Patricia L. Huestis1 and Jay A. LaVerne1
1Department of Physics and Notre Dame Radiation Laboratory, University of Notre Dame, Notre
Dame, IN, USA.
Over 200 million liters of high level waste (HLW) reside in the Hanford Waste Tanks. These
tanks contain legacy waste from the Cold War era and are chemically complex due to high
nitrate concentrations, high pH, and large radiation fields. Boehmite (γ-AlOOH) is a large
component of the solid waste located within the tanks and is especially problematic due to its
longer than predicted dissolution times. Boehmite has a layered structure which consists of an
Al-O lattice hydrogen bonded together via bridging OH groups. The mechanism responsible
for hydrogen production in boehmite is still not well understood.
Boehmite was heated to various temperatures along its dehydration pathway to assess the
structural differences and their effect on the radiolysis of boehmite. Structural changes were
investigated using powder X-Ray Diffraction (pXRD), Raman spectroscopy, nitrogen
adsoption, and Scanning Electron Microscopy (SEM). Radiolytic effects were assessed using
Gas Chromatography (GC) and Electron Paramagnetic Resonance (EPR). Different sizes of
materials were used to investigate the size dependence on the thermal degradation and its effect
on the creation of radiolytic products by gamma rays.
The yield of H2 with respect to energy deposited into the material/water system is nearly
constant for both sizes of material heated below 300°C with the smaller material having a
slightly higher yield. The larger material, when preheated further to 400°C, shows a dramatic
increase in H2 production. Larger material preheated to 550°C as well as smaller material
preheated to both 400°C and 550°C shows a yield consistent with alumina, indicating complete
or near complete dehydration. Initial production of trapped hydrogen radicals within the larger
material in conjunction with the yield for the sample preheated to 400°C suggest that the
hydrogen production mechanism is likely an abstraction reaction by H atoms with surface water
as opposed to a bimolecular combination reaction.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
46
P16: Key Role of the Oxidized Citrate Free Radical in the Nucleation
Mechanism of the Metal Nanoparticles Turkevich Synthesis
Sarah Al Gharib,1,2, Jean-Louis Marignier,1 Adnan Naja,2 Abdel Karim El Omar,2 Sophie Le
Caer,3 Mehran Mostafavi,1 and Jacqueline Belloni1.
1 Laboratoire de Chimie-Physique/ELYSE, UMR 8000 CNRS/UPS, Université Paris Sud, Université Paris-Saclay, Bât. 349, F-91405 Orsay Cedex, France.
2 Laboratoire Physique et Modélisation, Université Libanaise, Tripoli, Lebanon. 3 Laboratoire LIONS, DSM/IRAMIS/NIMBE UMR 3685 CNRS/CEA/Saclay, Université Paris-Saclay,
Bât. 546, F-91191 Gif-sur-Yvette, Cedex, France.
The step-by-step mechanism of the citrate oxidation, of the silver ion reduction [1] [2] into
atoms, and of the nucleation of nanoparticles by the Turkevich method [3] are deduced from
the gamma- and pulse radiolysis yields of dicarboxy acetone (DCA), H2 and CO2 and of silver
ion reduction. Our results demonstrate that the stronger reductant is not citrate (Cit) but the
oxidized radical Cit(-H)•. The formation yields of DCA and CO2 confirm the decarboxylation
process during the Cit(-H)• oxidation. In pulse radiolysis of solutions of sodium citrate and
silver perchlorate, the transient spectra [4] and the kinetics are observed from 20 ps to 800 ms.
In particular, the successive H abstraction from citrate by OH• radicals, then the one-electron
transfer from the citrate radicals Cit(-H)• to silver ions initiating the simultaneous nucleation
and growth of the reduced silver oligomers are observed. The knowledge of the nuclearity-
dependent kinetics and thermodynamics of silver atoms, oligomers and nanoparticles in
solution is used to bracket the standard reduction potentials of the first (≥ 0.4 VNHE) [2] and the
second one-electron transfers from citrate (≤ - 1.2 VNHE) [2]. During the Turkevich synthesis,
the Cit(-H)• radical was shown to be released in the bulk solution from the citrate oxidation by
Ag+ adsorbed on the walls (Figure 1), or directly by the trivalent AuIII ions present in the bulk,
respectively. Then the strong Cit(-H)• reductant alone is able, as in radiolysis, to overcome the
thermodynamic barrier of the very negative potential for the reduction of the free monovalent
ions into atoms that is required to initiate the nucleation and growth (Figure1). The reduction
potentials values of citrate and Cit(-H)• also explain part of the antioxidant properties of citrate.
Reference(s)
1. Marignier, J.L;. Belloni, J. ; Delcourt, M.O. ; Chevalier, J.P Nature, 1985, 317, 344-345.
2. Belloni J., Mostafavi, M., Radiation Chemistry of Clusters and nanocolloids. In Studies in
physical and theoretical chemistry, Radiation Chemistry:, Jonah, C.D. ; Rao, M. (eds), Elsevier,
2001, 87, 411-452.
3. Turkevich, J.; Stevenson, P.C.; Hillier, J. Disc. Faraday Soc. 1951, 55-75.
4. Simic, M.; Neta, P.; Hayon, E. J. Phys. Chem. 1969, 73, 4214-4219.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
47
I18: The Effects of Gamma Radiation on the Accelerated Carbonation of
Fly-Ash Blended Cement
A. Potts1, E. Butcher2, G. Cann2, L. Leay1
1 Dalton Cumbrian Facility, The University of Manchester
2 National Nuclear Laboratory
Both gamma irradiation and carbonation are known to induce long term aging effects occurring
within concrete structures in nuclear facilities. Previous studies have shown that the coupling
of these two mechanisms leads not only to an increase in the carbonation depth [1-2] but also
a change in the primary carbonation product formed [3]. In this talk, we present the
experimental results addressing this coupling effect.
Carbonation occurs as CO2 diffuses into the cement pore water, reacting with calcium-
containing phases such as calcium hydroxide to form calcium carbonate:
Ca(OH)2 + CO2 → CaCO3 + H2O
This process involves the dissolution of calcium cations from the crystalline phase and
carbonate anions into the alkaline pore water. Calcium carbonate exists as polymorphs: calcite
(most thermodynamically stable), aragonite and vaterite (least thermodynamically stable).
Our experiment was conducted sequentially: 1.2 MGy gamma irradiation under atmospheric
conditions and 50 °C followed by carbonation in a 5% CO2 atmosphere at room temperature.
A heat treated unirradiated sample was also analysed for comparison. The XRD heatmaps
below show that both the irradiated and heat-treated samples exhibit an increased depth of
carbonation compared to the control, as well as a switch in carbonation phase from vaterite to
calcite. Our results suggest that both heat and irradiation cause a long-lasting change in the
cement leading to an alternative carbonation pathway.
Irradiated then carbonated Heated then carbonated Control (carbonated only)
P= Portlandite (calcium hydroxide), Q = quartz, V= Vaterite, A = Aragonite, C = Calcite
and C-S-H is calcium-silicate-hydrate
Currently, other researchers hypothesise that advanced dehydration is the mechanism for
irradiation accelerated carbonation. A radical chemistry route leading to calcium hydroxide
formation has also been discussed. Our data implies that there are subtle differences in the
irradiated and heat treated samples. Further analysis involves SEM-EDS characterisation to
gain an insight into the morphology of the carbonate phases as well as pore water chemical
analysis.
Reference(s)
1. Vodák, F, Vydra V, Trtík, K, and Kapicková O. (2011) Effect of Gamma Irradiation on Properties
of Hardened Cement Paste Materials and Structures 44 (1): 101–7.
2. Bar-Nes, G, Katz, Peled, Y and Zeiri, Y (2008) The combined effect of radiation and carbonation
on the immobilization of Sr and Cs in cementitious pastes Materials and Structures 41: 1563-
1570
3. Maruyama, I, Shunsuke I, Junichi Y, Shohei S, and Ryo K. (2018) Impact of Gamma-Ray
Irradiation on Hardened White Portland Cement Pastes Exposed to Atmosphere Cement and Concrete Research 108 (June 2017): 59–71.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
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P17: The Radiation Chemistry of Aqueous PVP Solutions Exposed to
Pulsed E-beam Irradiation: Experiments and Numerical Simulations
C. Dispenza1, M. A. Sabatino1, B. Dahlgren2, M. Jonsson2
1Department of Engineering, University of Palermo, Italy. 2Department of Chemistry, KTH Royal Institute of Technology, Sweden.
Nanogels have recently raised considerable interest in the biomedical field, due to their diverse
applications in tissue engineering, regenerative medicine and drug delivery.
One-pot radiation-induced synthesis of nanogels from dilute aqueous polymer solutions is one
example of a process that has been successfully carried out using electron accelerators equipped
with scanning horn and a conveyor belt. In dilute aqueous systems the radiation energy is
mainly absorbed by water. Upon exposure to ionizing radiation, water is decomposed into OH,
H, eaq-, H2, H2O2 and H3O+. Polymer radicals are formed upon hydrogen abstraction from the
polymer by OH and H. By saturating the aqueous solution with N2O, the strongly reducing
hydrated electron can be converted into a hydroxyl radical.
In the radiation synthesis of nanogels from polymer aqueous solutions, conditions that favor
intramolecular radical-radical reactions are generally employed. Interestingly, these are also
the conditions when scavenging of the primary radicals formed in the radiolysis of water is no
longer quantitative. Under these conditions, a fraction of the hydroxyl radicals can recombine
and produce hydrogen peroxide. This can have a significant influence on the further reactions
in the system. In systems exposed to a sequence of pulses, the formation of H2O2 will eventually
lead to the production of O2. It is therefore desirable to be able to perform both experiments
and numerical simulations on these systems both in order to confirm mechanistic and kinetic
data and to be used as a predictive tool for process optimization.
The obvious first step in the development of the modelling tool is the simulation of single pulse
irradiations to explore the effects of dose per pulse, concentration of polymer and polymer
molecular weight on the kinetics of polymer radical decay. The next step is to model more
complex pulse sequences that resemble conditions used to irradiate large volumes of aqueous
polymer solutions and produce nanogels.
The numerical simulation is based on a deterministic approach encompassing the conventional
homogeneous radiation chemistry of water as well as chemical reactions involving polymer
chains and polymer radicals. As benchmarking, results from a series of experiments on pulsed
irradiation of aqueous PVP-solutions have been used. The simulations qualitatively reproduce
the experimentally observed impact of initial gas saturation (air and N2O) and polymer
concentration on the molecular chain length upon irradiation. The formation of double bonds
as a function of dose as well as the impact of effective dose rate on the final chain length are
also qualitatively reproduced in the simulations and suggests different possible options for
irradiation conditions to tailor the molecular weight and functionality of the synthetized
nanogels to meet application requirements.
Acknowledgements
BD acknowledges the Royal Institute of Technology for financial support.
CD acknowledges the Institute of Nuclear Chemistry and Technology in Warsaw (Poland) for
performing the ebeam irradiations and IAEA CRP F22064.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
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P18: Internal Structure and Composition of Fukushima-Derived
Particulate Revealed through Combined Synchrotron and Mass-
Spectrometry Techniques
P.G. Martin1, S. Cipiccia2, D.J. Batey2, Y. Satou3 and T.B. Scott1
1School of Physics, University of Bristol, HH Wills Physics Laboratory, Tyndall Avenue, Bristol, BS8
1TL 2Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE
3Japan Atomic Energy Agency (JAEA) - CLADS, Tomioka, Futaba-gun, Fukushima Prefecture, Japan
Despite the events at the Fukushima Daiichi Nuclear Power Plant (FDNPP) having passed
their eighth anniversary, a considerable amount of work is still ongoing to evaluate
the nature and environmental legacy of the radioactive particulate species [1,2].
Through the application of both laboratory and synchrotron radiation (SR) x-ray tomography
(XRT), the internal structure of a representative sub-mm particle was shown to be highly-
porous – with 24% of the internal volume constituted by void space (Figure 1). Compositional
(elemental) analysis of the particulate material through SR x-ray fluorescence (XRF) detailed
the peripheral enrichment of several elements (including Sr, Pb and Zr). The component of
fissionogenic Cs (134 + 135 + 137Cs) was determined to account for most of the elemental
abundance within the particle with limited contribution from natural 133Cs.
SR x-ray absorption near edge structure (XANES) analysis on several high atomic density
particles located within the bulk particle confirmed them to be U in composition, existing in
the U(IV) oxidation-state, as UO2. The complementary isotopic analysis of this micron scale
uranium material enclosed just below the surface of the particle was subsequently determined
using secondary ion mass spectrometry (SIMS), having spatially referenced their co-ordinate
positions between the different techniques. SIMS mapping revealed the U-rich particle to be
~1 μm in maximum dimension, consisting of enriched U with 3.54 wt% 235U – analogous to
that used in the reactor Unit 1 fuel assemblies [3].
References
[1] Imoto et al., (2017). Scientific Reports, 7 (5409) pp. 12.
[2] Furuki et al., (2017). Scientific Reports, 7 (42731) pp. 10. [3] Fukushima Daiichi NPS - Information Portal. TEPCO (2013).
Figure 1. SR-XRT reconstruction of the representative particle showing the 24% void volume.
Regions of both stainless-steel (orange) and cement (green) composition are shown (as identified
through SR-XRF), as are locations where voids are observed to interact.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
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31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
51
TUESDAY 10TH SEPTEMBER 18:00-19:00
POSTER SESSION 1
(EVEN NUMBERS)
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
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Poster 2: Impact of Doping and Functionalisation of Graphene Support on
the Radiolytic Synthesis of Palladium Nanoparticles for Electrocatalysis
Kun Guo1,2 and Aliaksandr Baidak1,2
1School of Chemistry, The University of Manchester, Manchester M13 9PL, UK;
2Dalton Cumbrian Facility, The University of Manchester, Moor Row CA24 3HA, UK.
Gamma radiolysis of common solvents, including ethylene glycol, is known to generate strong
reducing species such as solvated electron, hydrogen atom and carbon-centred radicals. This
mechanism provides a green and facile route to synthesize colloidal metal nanoparticles (NPs)
immobilized on graphene-based supports. However, controlling the NP size and size
distribution remain challenging. Hereby we investigate the impact of heteroatom doping and
functionalisation of graphene-based supports on tackling such challenges. Four types of
graphene materials, namely graphene oxide (GO), reduced graphene oxide (rGO), graphene
(G), and nitrogen-doped graphene (N-G), are utilised to immobilize palladium (Pd) NPs, which
are obtained by γ-radiation-induced reduction in ethylene glycol. The as-prepared composites
are then evaluated in the electrocatalytic hydrogen evolution reaction (HER).
For the same Pd NP loading, N-G is found to be the best support to achieve the smallest
overpotential (difference between the applied and theoretical potentials) and the highest
catalytic activity, as shown in Figure 1a. The overpotential at a current density of 10 mA cm−2
(η10) on Pd/N-G is 160 mV smaller than that on Pd/rGO. Tafel analysis derived from the
polarizaiton curves shows that Pd/N-G has a Tafel slope of 101 mV decade−1, indicating the
rate determining step of HER on Pd/N-G is the Volmer step (H3O++e−+ * ⇄H*+H2O, where
* denotes the active site). The activity difference of four composites should be ascribed to the
NP size and size distribution of Pd NPs anchored onto these supports. NP size is well-
documented to strongly affect the catalytic activity/selectivity because more surface active sites
are exposed as size decreases. N-G is thus reasoned
to gain the smallest Pd NP size and best size
distribution during the radiolytic synthesis, which
should be correlated to the positive role of doped N
atoms in stabilising the formed NPs.
Given the positive role of doped N atoms, we
further prepare N-G supported with four loadings of
Pd NPs to explore the potential threshold in
maintaining the Pd NP size. Figure 1b presents the
polarization curves of N-G loaded with 1.3~5.2 wt.
% Pd NPs and the benchmark Pt/C catalyst. The
best performance of Pt/C accords well with the
literature. In contrast, the η10 and Tafel slope are
found to be the smallest for 2.6 wt. % Pd/N-G,
indicating its highest HER catalytic activity. The
decreased activity of 3.9 and 5.2 wt. % Pd/N-G
should be attributed to the severe aggregation of Pd
NPs, leading to lower atom efficiency. Therefore, in
order to achieve a desirable NP size and size
distribution, the NP loading shall be carefully
controlled.
Figure 1. Polarization curves of Pd NPs
supported on four graphene-based supports
(a) and Pd NPs supported on N-G with four
loadings (b) in 0.5 M H2SO4.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
53
Poster 4: Role of Electronic Energy Loss of the Ion Beam in the
Modification of Graphene Oxide Film
Chetna Tyagi1,2, A. Tripathi2 and D. K. Avasthi3
1Dalton Cumbrian Facility, The University of Manchester, Cumbria, UK, 2Inter-University Accelerator Centre, New Delhi, India,
3Amity Institute of Nanotechnology, Amity University, Noida, India.
Ion beam irradiation is a clean method to produce desired modifications in materials in a
controlled manner [1]. The present work shows the modifications induced in graphene oxide
film under swift heavy ion irradiation with different electronic energy loss. Graphene oxide
films were irradiated with Gold ion beam having energy 120 MeV with fluences varying from
3×1010 ions/cm2 to 1×1013 ions/cm2. X-ray diffraction and spectroscopic techniques indicated
some annealing effect induced by ion beam at lower fluences of irradiation while signature of
carbyne could be seen in Raman spectroscopy at higher fluence (Figure 1). Similarly, Carbon
beam of energy 80 MeV with relatively low electronic energy loss was used to irradiate the
graphene oxide films with different fluences. Different characterization techniques showed the
creation of defects by ion beam in the films. Theoretical simulations showed the local lattice
temperature raised in the films when irradiated with ion beams having different energy loss. It
could be seen that ion beam having high electronic energy loss could raise the temperature of
the film above its annealing and melting temperature, resulting in two competing phenomena:
annealing and amorphization. Also, the estimated radius of the ion track (core and halo region)
formed by Gold ions irradiation was calculated experimentally and compared with the
theoretical values obtained by simulation.
(a) (b)
Figure 1. (a) Plot showing the intensity of in-situ X-ray diffraction peak of pristine and
irradiated sample and (b) Raman spectra of irradiated sample with different fluence. Magnified
part is showing the origin of carbyne peak at high fluences.
Reference
1. GK Mehta, (1997) Swift heavy ions in Materials Science – emerging possibilities, Vacuum, 48, 957-
959.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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Poster 6: Radiation Induced Polymerization of Nanostructured Conducting
Polymers
T. Bahry1 and S. Remita2
1Laboratoire de Chimie Physique, LCP, UMR 8000, CNRS, Université Paris-Sud 11, Bât. 349, Campus d’Orsay, 15 Avenue Jean Perrin, Orsay Cedex 91405, France
2Département Chimie Vivant Santé, Conservatoire National des Arts et Métiers, CNAM, 292 rue Saint-Martin, Paris Cedex 75141, France.
Conducting polymers (CPs) have gained vast attraction due to their unique optical and
electrical properties [1]. Thanks to these prominent and extraordinary properties, CPs have
been used in several fields and integrated in many applications [2]. Tremendous efforts have
been made to develop and upgrade the synthesis methodologies of CPs [3]. Apart from
traditional methods of polymers synthesis, ionizing radiation induced polymerization by -rays
without using oxidizing agents appears to be alternative and easy way to produce conducting
polymers. Indeed, our group has developed a new methodology based on radiation chemistry
to polymerize some of those conducting polymers (CPs) in aqueous solutions [4, 5]. Recently,
we extended this methodology to the synthesis of CPs in organic solvent [6]. In this context,
we succeeded in the oxidative polymerization of different classes of thiophene derivatives
monomers dissolved in dichloromethane by means of gamma-radiolysis (Figure 1). The
spectroscopic analysis and microscopic observations manifest that the radio-synthesized
polymers in dichloromethane are characterized by interesting optical and electrical.
Reference(s)
1. A. J. Heeger, J. Phys. Chem. 2001, 105 (36), 8476-8491.
2. R. Balint, et al., Acta Biomater. 2014, 10(6), 2341-53.
3. X. T. Zhang, et al., J. Phys. Chem. 2006, (110), 1158−1165.
4. Y. Lattach, et al., Radiat. Phys. Chem. 2013, (82), 44-53.
5. Z. P. Cui, et al., Langmuir. 2014, (30), 14086−14094.
6. T. Bahry et al., New J. Chem. 2018, 42 (11), 8704-8716.1.
Figure 6. PEDOT, P3HT and P3TAA synthesized by gamma radiolysis in
dichloromethane
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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Poster 8: Effect of Surface Deformation on Stress Corrosion Crack
Initiation in Austenitic Stainless Steels in PWR Primary Water
Litao Chang, M. Grace Burke, Fabio Scenini
Materials Performance Center, The University of Manchester, Manchester, UK M13 9PL
Austenitic stainless steels are widely used in the nuclear power plants due to their good general
corrosion resistance to the high temperature aqueous environment. However, they can suffer
from environmentally-assisted degradation problems, such as stress corrosion cracking (SCC),
during the long-term exposure to the environment. Numerous researches indicate that cold-
work, induced either intentionally or incidentally, is necessary for SCC in austenitic stainless
steels in PWR primary water. In the present study, the effect of the machining-induced surface
deformation on SCC initiation of austenitic stainless steels in PWR primary water has been
investigated through accelerated slow strain rate tensile tests and microstructural
characterization. The results showed that machining always introduced a deformation layer to
the steels. This layer is characterized by an ultrafine-grained outer layer and a highly deformed
inner layer consisted of twins and dislocations. SSRT test results showed that machining
significantly reduced the SCC initiation susceptibility of the cold-worked material as a reduced
number of cracks were identified in the machined surface compared to the polished surface.
The results also indicated that a low temperature heat treatment could further increase the SCC
initiation resistance of the machined surface because of the recovery which happened with the
ultrafine-grain. The associated mechanisms and possible implications of the results have been
discussed.
Reference(s)
1. Chang et al., Stress corrosion crack initiation in machined type 316L austenitic stainless steel in
simulated pressurized water reactor primary water, Corr. Sci. (2018) 138, 54-65
2. Chang et al., Effect of machining on stress corrosion crack initiation in warm-forged type 304L
stainless steel in high temperature water, Acta Mater. (2019)165, 203-214
3. Chang et al., Understanding the effect of surface finish on stress corrosion crack initiation in warm-
forged stainless steel 304L in high-temperature water, Scripta Mater. (2019) 164, 1-5
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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Poster 10: Method of Assessing the Radiation Tolerance of Commercial
Strippable Coatings
A. Jenkins1, L. Ostle1, T. Donoclift2, R. Edge2, T. Unsworth2, K. Warren2
1 Sellafield Ltd., Seascale, Cumbria. UK
2Dalton Cumbrian Facility, University of Manchester, Moor Row, Whitehaven, Cumbria. UK
There are a plethora of commercially available strippable coating products, designed for
contamination control and decontamination purposes. Sellafield Ltd. has sought for a number
of these to be subjected to a predefined series of analyses pre and post irradiation to observe
any degradation of the product. Irradiation of the coatings to doses of 500kGy was separately
carried out by cobalt-60 and ion-beam to mimic plutonium alpha particles by Dalton Cumbrian
Facility. This dose threshold was deemed sufficient to allow for wastes to be packaged and
reach the respective disposal point.
A series of analyses were carried out and comparisons made of the pre and post irradiation.
The analyses included; direct observations for physical colour changes and deformities,
scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR),
Raman spectroscopy, Gas Chromatography – Mass Spectroscopy (GC-MS) and energy-
dispersive X-ray spectroscopy (EDS).
An illustration of how these coating systems degrade will be given alongside more anecdotal
perspective of how more easily obtained gamma irradiation can be used to infer alpha
degradation of organic species.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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Poster 12: The Degradation of Lithium Acetate under Gamma Irradiation
in Degassed and Hydrogenated Conditions
C. McBride1, A. Baidak1, S. Heath2 and R. Wain3
1Dalton Cumbrian Facility, The University of Manchester, Westlakes Science Park, Moor Row, Cumbria, CA24 3HA;
2Dalton Nuclear Institute, The University of Manchester, Pariser Building, Sackville Street, Manchester, M13 9PL;
3Rolls Royce PLC, Jubilee House, 4 St Christopher’s Way, Pride Park, Derby, DE24 8JY.
Zinc injection is a commonly practised technique in the nuclear industry for the mitigation of
primary water stress corrosion cracking and the reduction of adsorbed radiation doses. Zinc,
most commonly in the form of zinc acetate, is injected into the primary cooling loop of the
PWR to undergo substitution mechanisms in the metal that makes up the primary cooling loop,
and while the mechanism of the zinc cation under the harsh conditions of the PWR is well
understood, the fate of the acetate counter ion is not documented in literature.
Concerns have been raised about the effect of products formed from the radiolysis of acetate
on the life time of ion exchange columns in the PWR and the effect of acetate on the partitioning
of carbon-14. In this poster the radiolytic degradation of the acetate ion in both degassed and
hydrogenated conditions is analysed and discussed in order to better understand its fate under
PWR conditions.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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Poster 14: Understanding the Effect of Microstructure Strain and Cold
Work on Intergranular Corrosion of AGR Fuel Cladding
S. Thornley1, D. Engelberg1, S. Walters2
1The University of Manchester, School of Materials, Sackville Street Campus, Manchester, M13 9PL; 2NNL Building D5, Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB.
Fuel pins in Advanced Gas Cooled Reactors (AGRs) are made form 20%Cr/25%Ni-Nb
stabilised austenitic stainless steel. Due to elevated temperatures and neutron irradiation a small
proportion of the fuel pins may become sensitised whilst in service. These materials can then
be susceptible to Intergranular Corrosion (IGC) during interim pond storage. The spent fuel
remains active for the duration of interim storage. Water exposed to gamma radiation can
undergo radiolysis producing a range of reactive species, which can promote corrosion in steel
components. The aim of this project is to understand the role that Cold Work (CW) and
microstructure strain play in promoting IGC during interim storage in water-cooled ponds.
Double Loop – Electrochemical Petentiokinetic Reactivation (DL-EPR) is an
electrochemically technique, which was used in this work to assess the Degree of Sensitisation
(DOS). Solution annealing (1150 °C for 0.5 hrs) followed by sensitisation treatments (600 °C
for 168/336 hours) was used to produced sensitised microstructures. The samples, prior to
thermal treatments, were in two conditions: As Received (AR) and Cold rolled to ~30 % CW.
Gamma irradiation exposure, using a 60Co planar irradiator, was used to test the IGC
susceptibility of AR sensitised samples. Further corrosion test took place using c-ring samples,
without irradiation, exposed to chloride environments. The tests were: submersion in 10 wt %
FeCl3 for 5 days at room temperature (test 1). Atmospheric Corrosion tests with droplets of 1
M/ 4 M MgCl2 at 60 °C for 7 days (tests 2/3).
DL-EPR testing revealed that the DOS increased with introduction of CW and when the
sensitisation time was increased from 168 to 336 hours. The susceptibility of the sensitised
microstructure to IGC was also confirmed on the gamma irradiated samples where significant
corrosion, surrounding the grain boundaries, was observed. In test 1 and 2 corrosion product
was observed to have formed during testing however no localised corrosion was observed.
However, test 3 showed a significant amount of pitting but no cracking.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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Poster 16: Gamma Irradiation and Hydrogen Production of Potassium
Activated Metakaolin Geopolymers
T.A. Mubasher1,2, A. Potts1 and L. Leay1
1 The University of Manchester, Dalton Cumbrian Facility, Westlakes Science Park, Whitehaven, Cumbria. CA24 3HA.
2 Centre for Innovative Nuclear Decommissioning (CINDe) – National Nuclear Laboratory (NNL), Workington, Cumbria, CA14 3YQ.
Geopolymers are cementitious materials produced through the condensation reaction between
a precursor (aluminosilicate) and alkali activator solution. Once this condensation reaction is
complete these materials exhibit a complex interconnected pore structure which contains water.
This study aims to investigate the effect of curing time on radiolytic hydrogen production from
potential formulations being explored by the nuclear industry for intermediate level waste
(ILW) immobilisation.
Potassium based metakaolin
geopolymers were mixed and cured for
1 year. The samples were crushed and
powdered to 300 – 500 μm, Sub samples
were dried overnight at 40 °C and
120 °C under vacuum. The samples
were dried at 40 °C and 120 °C before
being irradiated, to observe the effect of
loosely and tightly bound water. For
hydrogen analysis, the powdered
samples (1 g each) were placed in crimp
cap vials, degassed under argon and then
gamma irradiated. The head space was
then analysed using gas chromatography.
Hydrogen analysis of geopolymer samples
cured for 1 year (Figure 1), indicate that samples dried at 40 °C produces a larger quantity of
hydrogen on irradiation compared with samples dried at 120 °C or non-dried samples. The
typical primary yield G (H2) value for water is 0.45 x10-7 mol/J (Eliot & Bartels, 2009),
whereas the samples investigated in this study achieved values from 0.13 to 1.16 x10-7 mol/J
(Table 1). Oxygen depletion was observed in the head space of dried samples, by gas
chromatogram. Additional work is underway to assess how the concentration of dissolved
species we expect to find in the pore water affects radiolytic hydrogen production. Initial results
from experiments using simulants of the pore water indicate that more concentrated simulant
results in greater hydrogen production.
Table 1: G values of F13 1 year cured samples calculated using the mass of the whole system
and not just the water.
System G(H2) Value (x10-7) mol/J
Not Dried 0.31
Dried at 40 °C 1.16
Dried at 120 °C 0.13
Figure 7: Hydrogen analysis of a 1 year cured
geopolymer
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
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Poster 18: Poly(Acrylic Acid) Radicals Recombination in Aqueous
Solutions
M. Matusiak, S. Kadlubowski, P. Ulanski
Institute of Applied Radiation Chemistry, Lodz University of Technology, Lodz, Poland
Polyelectrolytes constitute a broad class of polymers including the most important biopolymers
(nucleic acids, proteins, many polysaccharides), as well as synthetic polymers. Presence of
charge along the chain makes many aspects of physical chemistry of polyelectrolytes more
complex than for neutral macromolecules [1,2]. This is also true for reaction kinetics. This
work is intended as a step forward in exploration of radical reactions in weak polyelectrolyte
solutions. The main model is poly(acrylic acid) - PAA. Poly(acrylic acid) plays a key role in
discussion of the properties and behaviour of water-soluble synthetic polymers because it is
the simplest common synthetic polycarboxylic acid. Previous studies on PAA radical reactions
have focused on identification of radicals and indication of their transformation mechanisms
[3,4], overall radical lifetimes [5,6] and on the application of intramolecular crosslinking for
synthesizing PAA nanogels [4,6]. The kinetics of radical recombination has not been studied
in detail so far. In the presented preliminary research we have focused on the strong effect of
charge density on the lifetime of PAA radicals and at radical recombination at pH 2.
Recombination of poly(acrylic acid) radicals is strongly influenced by its dissociation degree
and thus by pH. At pH 2 recombination is fast, in an more alkaline environment, reactions are
much slower. Kinetics and mechanism of the recombination depend on the average number of
radicals generated on each chain. A transition in kinetics is observed between intermolecular
and intramolecular recombination.
The results, beside providing basic information about polymer radicals, their lifetime, kinetics
both in intra- and intermolecular reaction modes in aqueous polymer solutions, may also be
relevant to some extent for radical reactions in biopolymers, most of them being
polyelectrolytes. Moreover, it provides information about PAA which can be later used to
design radiation-synthesized polymer nanoparticles used for controlled drug-, gene- and
radioisotope delivery systems.
This work has been supported by the National Science Centre, Poland, project no.
2017/27/N/ST4/02536.
References
1. Görlich, W., & Schnabel, W. (1973) Untersuchungen über den einfluß der ladungsdichte auf die
gegenseitige desaktivierung von polyion‑makroradikalen Makromol.Chem. 164, 225-235.
2. Behar, D., & Rabani, J. (1988) Pulsed radiolysis of poly (styrenesulfonate) in aqueous solutions J.
Phys. Chem., 92, 5288-5292.
3. Ulanski, P., Bothe, E., Hildenbrand, K., Rosiak, J. M., & von Sonntag, C. (1995) Radiolysis of
poly (acrylic acid) in aqueous solution Radiat. Phys. Chem., 46, 909-912.
4. Matusiak, M., Kadlubowski, S., & Ulanski, P. (2018) Radiation-induced synthesis of poly (acrylic
acid) nanogels. Radiat. Phys. Chem., 142, 125-129.
5. Ulanski, P., Rosiak, J. M., Bothe, E., Hildenbrand, K., & von Sonntag, C. (1997) The influence of
repulsive electrostatic forces on the lifetimes of poly (acrylic acid) radicals in aqueous solution
Nukleonika, 42, 425-436.
6. Kadlubowski, S., Grobelny, J., Olejniczak, W., Cichomski, M., & Ulanski, P. (2003) Pulses of fast
electrons as a tool to synthesize poly (acrylic acid) nanogels. Intramolecular cross-linking of linear
polymer chains in additive-free aqueous solution Macromolecules, 36, 2484-2492.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
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Poster 20: Preventing the Development of Antibiotic Resistance in
Wastewater Matrices by High Energy Irradiation
R. Homlok1, L. Szabó1, K. Kovács1, T. Tóth1, E. Takács1, Cs. Mohácsi-Farkas2, L.
Wojnárovits1
1Institute for Energy Security and Environmental Safety, Centre for Energy Research, Hungarian Academy of Sciences, Konkoly-Thege Miklós út 29-33, H-1121 Budapest, Hungary;
2Department of Microbiology and Biotechnology, Faculty of Food Science, Szent István University,
Somlói út 14-16, H-1118 Budapest, Hungary.
Nowadays, one of the most important challenges of environmental protection is preservation
and improvement of water quality. A wide range of pollutants are released into our natural
waters all over the world. Among several pharmaceutical contaminants, antibiotics in particular
have a very harmful effect on the environmental microbiota. As a result, antibiotic residues
may concentrate in plants and animals; integrate into the living organisms and contribute to the
spread of antibiotic resistance, which represents a serious issue worldwide [1].
During development of antibiotic resistance, several genetic processes occur in bacteria that
can confer the microbes different protecting mechanisms to overcome their previous sensitivity
against the antibiotic. As a result, resistant or even multi-resistant microorganisms have been
created. Microbes are able to pass these resistant genes to related or even non-related species
by horizontal gene-transfer that permits the rapid spread of resistance involving also pathogen
microorganisms [2]. This is a major threat to public health.
In our laboratory, we have studied the applicability of electron beam irradiation in eliminating
the antimicrobial activity of several groups of antibiotics [3-5]. We have also placed special
emphasis to find out whether any effect can be observed on the population dynamics of a mixed
resistant and sensitive microbial population during advanced oxidation of antibiotics at the sub-
inhibitory level [5]. It appeared from these studies that the technology needs to be carefully
optimized and there is still much to be done in this field. As a continuation of our previous
studies, we take further steps to understand more complex systems by applying microbiological
assays on model wastewater matrices. The presentation will give an insight into our recent
advances.
Reference(s)
[1] Baquero, F., Martínez, J.L., Cantón, R. (2008) Antibiotics and antibiotic resistance in water
environments. Current Opinion in Biotechnology 19, 260-265.
[2] Wright, G.D. (2010) Antibiotic resistance in the environment: a link to the clinic?, Current Opinion
in Microbiology 13 589–594.
[3] Szabó, L., Szabó, J., Illés, E., Kovács, A., Belák, Á., Mohácsi-Farkas, Cs., Takács, E., Wojnárovits, L. (2017) Electron beam treatment for tackling the escalating problems of antibiotic resistance:
eliminating the antimicrobial activity of wastewater matrices originating from erythromycin. Chemical
Engineering Journal 321, 314-324.
[4] Sági, Gy., Bezsenyi, A., Kovács, K., Klátyik, Sz., Darvas, B., Székács, A., Mohácsi-Farkas, Cs.,
Takács, E., Wojnárovits, L. (2018) Radiolysis of sulfonamide antibiotics in aqueous solution:
Degradation efficiency and assessment of antibacterial activity, toxicity and biodegradability of
products. Science of the Total Environment 622-623, 1009-1015.
[5] Szabó, L., Steinhardt, M., Homlok, R., Kovács, K., Illés, E., Kiskó, G., Belák, Á., Mohácsi-Farkas,
Cs., Takács, E., Wojnárovits, L. A microbiological assay for assessing the applicability of advanced
oxidation processes for eliminating the sublethal effects of antibiotics on selection of resistant bacteria.
Environmental Science and Technology Letters 4, 251-255.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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Poster 22: Kinetic Studies on Dextran and Dextran Methacrylate in
Aqueous Solutions
K. J. Szafulera, R. A. Wach and P. Ulanski
Institute of Applied Radiation Chemistry, Lodz University of Technology
High interest in the use of ionizing radiation for the processing of polymers is mainly because this
technique is a very efficient and clean tool, especially for modification of polysaccharides.
These polymers, due to their natural origin, non-toxic and biodegradable character, are constantly
finding new applications in various important fields, including medicine [1]. Dextran helps in curing
vascular thrombosis, reduces inflammatory response and promotes vascularization, hence it is
a promising candidate for soft tissue regeneration [2]. Our main goal is to synthesize a dextran
derivative, dextran methacrylate (Dex-MA), having substituents capable of covalent crosslinking and
subsequently further development of conditions suitable for the formation of macroscopic hydrogels by
radiation technique, which is an attractive approach to produce new class of wound dressing
in the future [3]. For better understanding of crosslinking or/and degradation processes occurring upon
irradiation of aqueous solutions of Dex-MA and the role of particular products of water radiolysis
in these processes, pulse radiolysis study of dextran and Dex-MA was performed.
A series of Dex-MA has been synthesized, yielding dextran methacrylate of moderate degree
of substitution (DS), up to 0.65, allowing the product to retain its solubility in water. A wide range
of initial dextran’s molecular weight (Mw) was employed (6, 25, 70 and 500 kDa). Pulse radiolysis
studies of dextrans and Dex-MA in aqueous solutions indicate that radicals on this polymer are formed
by reactions of both hydroxyl radicals and hydrated electrons. In order to study the reactivity of ·OH
and 𝑒𝑎𝑞− with respect to the -MA substituent, methacrylic acid (MAA) was also employed as a model
compound. To determine the rate constants of ·OH attack, competitive kinetics with SCN- scavenger
was used. It can be concluded that the reactions of the ·OH with dextran and Dex-MA are fast, their rate
constants are high, in the order of 108 [dm3/mol∙s] for all studied DS and Mw. A slight increase in the
rate of this reaction was observed along with an increase in DS, which indicates that the methacrylic
group reacts with the ·OH faster than with the basic sugar unit. The rate constant of MAA with ·OH is
2.2∙1010 [dm3/mol∙s], which confirmed this conclusion. In order to determine the rate constant of 𝑒𝑎𝑞− a
direct absorbance measurement of decay at 720 nm was used. As expected, the reaction rate constant
of 𝑒𝑎𝑞− with dextran is low, 106 [dm3/mol∙s]. Introduction of the methacrylic substituent into dextran
structure causes the increase of this constant by two orders of magnitude. The increase in the rate
constant is due to the high reactivity of the hydrated electron in relation to the double bonds and the
carbonyl group present in methacrylic moieties (MAA reacts with 𝑒𝑎𝑞− with rate constant of 5.6∙109
[dm3/mol∙s]). Therefore, the obtained results show that the formation of radicals on the main chain of
dextran corresponds primarily to the reaction of hydroxyl radical, while the formation of radicals on
the methacrylic substituent is due to both ·OH and 𝑒𝑎𝑞− .
References
1. The Radiation of Chemistry of Polysaccharides, International Atomic Energy Agency, IAEA, Vienna (2016)
2. S. Dumitriu, Polysaccharides: structural diversity and functional versatility, CRC Press, Boca Raton FL
(2005)
3. K. Szafulera et al., Radiat. Phys. Chem. (2018), 142, 115–120
Acknowledgments
Authors acknowledge the National Science Centre, Poland (2017/25/N/ST4/01814) for financial support.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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Poster 24: Phosphate Buffer Influence on Tyrosyl Radicals Formation
Sebastian Sowinski, Slawomir Kadlubowski, Piotr Ulanski
Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology
Exposition of biomolecules to oxidative stress (i.e. by reaction with water radiolysis products)
can lead to changes in their structure that impair their functionality. On the other hand,
introduced changes may possibly involve formation of protein-protein crosslinks, that can be
utilized in synthesis of nanoparticles with wide range of biomedical uses. Radiation-induced
crosslinking with formation of nanostructures has been demonstrated for globular proteins such
as papain [1] and bovine serum albumin [2]. Postulated mechanism of this process involves
formation of phenoxyl-type tyrosyl radicals (TyrO•) which after isomerization and subsequent
recombination form covalent bonds, but some aspects, such as influence of the buffer on the
process remain unclear. Better understanding of the radiation chemistry in this system is
therefore important to introduce changes in protein structure in more controlled way.
Low-molecular-weight model (tripeptide H-Gly-Tyr-Gly-OH) was used to partially simulate
behavior of tyrosine in more complex protein systems. Pulse radiolysis with
spectrophotometric detection was used to determine kinetic aspects of TyrO• formation in
phosphate buffer solutions. Influence of phosphate buffer on the reaction rate constants
involved in phenoxyl radicals formation, as well as possible reaction with phosphate derived
radicals were investigated. Experimentally obtained reaction rate constants were double-
checked using simple probabilistic simulations in Kinetiscope software package.
References
1. Varca G.H.C., Perossi G.G., Grasselli M., Lugão A.B. (2014) Radiat Phys Chem, 105, 48-52.
2. Queiroz R.G., Varca G.H.C., Kadłubowski S., Ulański P., Lugão A.B. (2016) Int J Biol Macromol.,
85, 82-91.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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Poster 26: Partial Molar Volume of the Hydrated Electron and a Comment
on Its Vertical Detachment Energy
Ireneusz Janik, Alexandra Lisovskaya and David M. Bartels
Notre Dame Radiation Laboratory, Notre Dame University, Notre Dame, Indiana, USA.
The partial molar volume of the hydrated electron was investigated with pulse radiolysis and
transient absorption2 by measuring pressure-dependence of the equilibrium constant for e-aq + NH4+
H + NH3 . At 2 kbar pressure the equilibrium constant decreases relative to 1 bar by only
6%. Using tabulated molar volumes for ammonia and ammonium, we have the result V(e-aq) –
V(H) = 11.3 cm3/mol at 25oC, confirming that V(e-aq) is positive and even larger than the
hydrophobic H atom. Assuming the molar volume of H atom is somewhat less than that of H2, we
estimate V(e-aq ) = 26±6 cm3/mol. The positive molar volume is consistent with an electron that
exists largely in a small solvent void, ruling out a recent controversial model of Larsen, Glover and
Schwartz3 (LGS) that suggests a non-cavity structure with negative molar volume. It is suggested
that no one-electron pseudopotential model of the hydrated electron is likely to capture all of the
dynamical properties of this species that depend on details of the wavefunction. A full ab initio MD
approach may be necessary.
A recent paper of Luckhaus, et al1 has presented
photoelectron data and analysis of eleven liquid microjet experiments with various excitation
wavelengths from 3.6 to 5.8 eV to extract a
“genuine” distribution of vertical electron binding
energies for the hydrated electron (Figure 1). The
analysis involves correction of the individual
photoelectron energy distributions at each
wavelength for scattering losses in the liquid before
escape into the vacuum. Surprisingly the
distribution reported is bimodal, resembling two overlapping Gaussians with centers at 3.5 and 4.5
eV. We find the bimodal distribution highly
implausible, as it represents a gross violation of
linear response for the hydrated electron ground
state energy. Rather, we identify a flaw in the
calculation of scattering losses that leads to the
bimodal distribution. The “bottom of the
conduction band” in liquid water has been taken to
be Vo = -1.0 eV relative to the vacuum. In the
scattering model used, electrons with kinetic energies below 1.0 eV never escape from the liquid
microjet. This assumption is shown to be
inconsistent with the data being fitted, and a more likely number is Vo = -0.1 ± 0.1 eV.
References
1. Luckhaus, D.; Yamamoto, Y. I.; Suzuki, T.; Signorell, R. Genuine Binding Energy of the
Hydrated Electron. Science Advances 2017, 3 (4).
2. Janik, I.; Lisovskaya, A.; Bartels, D. M. Partial Molar Volume of the Hydrated Electron.
Journal of Physical Chemistry Letters 2019, 10 (9), 2220-2226.
3. Larsen, R. E.; Glover, W. J.; Schwartz, B. J. Does the Hydrated Electron Occupy a Cavity?
Science 2010, 329 (5987), 65-69.
Figure 1. “Genuine” electron Binding
Energy (eBE(g)) distribution reported by
Luckhaus, et al.1 The bimodal
distribution (asterisks) with average of
3.7eV can be decomposed into a pair of
Gaussian functions centered at ca. 3.5
and 4.5 eV.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
65
Poster 28: Oxygen Effects on Antioxidant Protection of Lymphoid Cells
against Free Radicals by a Range of Dietary Carotenoids
R. Edge1, F. Boehm2 and T.G. Truscott3
1Dalton Cumbrian Facility, The University of Manchester, Westlakes Science Park, Moor Row, Cumbria, UK;
2Photobiology Research, IHZ, Berlin, Germany; 3School of Physical Science (Chemistry), Keele University, Staffordshire, UK.
Carotenoids are natural pigments, being constituents of a wide variety of fruits and vegetables,
though chlorophyll often masks their presence. Believed to act as dietary antioxidants, having
been shown to quench both singlet oxygen and a range of free radicals, carotenoids are of
interest for their health benefits. While carotenoids are consumed in significant quantities from
normal diets, in recent years, they are also consumed in large quantities via food supplements.
This may well be based on claims that they offer major health benefits but there are also
counter-claims that they can be damaging to human health.
We have shown previously that dietary lycopene, the red carotenoid pigment in tomatoes,
protects against human lymphoid cell membrane damage from free radicals produced by γ-
radiation and that this protection is dramatically reduced when the oxygen concentration is
increased [1].
In this work we study a wider range of dietary carotenoids, showing protection of human
lymphoid cells from membrane damage caused by free radicals produced by γ-radiation. Blood
was taken from volunteers who had supplemented their diet with large doses of a specific
carotenoid for 2 weeks or had minimized carotenoid-rich fruit and vegetables in their diet.
Radical-induced cell membrane destruction was shown by cell staining with eosin.
All carotenoids studied imparted protective effects and the carotenoid protective effect was
reduced as oxygen concentration increased, as previously seen for lycopene. In fact, the oxygen
effect was observed to be most pronounced for lycopene, where there was almost no protection
under 100% oxygen, down from 5-fold protection at 21% oxygen and, an extremely high, 50-
fold, protection in the absence of oxygen. Studies with β-carotene and the xanthophylls,
astaxanthin, zeaxanthin and lutein, have shown a reduced, but still significant, oxygen effect.
Gamma radiation cellular studies have also been undertaken with the addition of superoxide
dismutase, showing that the effect is not due to reactions of the superoxide radical.
Additionally, a series of non-cellular gamma radiolysis studies in simple solutions, as well as
cell protection studies against nitrogen dioxide radical, generated photolytically, have also been
carried out to help elucidate the molecular mechanisms for the observed oxygen effect.
The remarkable reduction in protection by carotenoids, particularly lycopene, against gamma
radiation at high oxygen concentrations could, perhaps, be exploited to enhance radiation
procedures for therapy.
References
2. Boehm, F., Edge, R., Truscott, T.G. and Witt, C. (2016) A dramatic effect of oxygen on protection
of human cells against γ-radiation by lycopene. FEBS Lett., 590, 1086-1093.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
66
Poster 30: Drastic Changes in the Surface Reactivity of UO2-Based Spent
Nuclear Fuel upon Exposure to Radiolytic Oxidants – How Will This
Influence the Safety Assessment of Deep Geological Repositories for Spent
Nuclear Fuel?
A. C. Maier and M. Jonsson*
Department of Chemistry, KTH Royal Institute of Technology, Stockholm, Sweden
Several countries plan to store their spent nuclear fuel in deep geological repositories for
extremely long time periods (>100000 years). This calls for rather extreme safety assessments
accounting for a multitude of possible scenarios. A commonly used scenario is groundwater
intrusion into a fuel canister after 1000 years. Since UO2 (the matrix of the most commonly
occurring spent nuclear fuel) has very low solubility in the reducing groundwater expected to
be found at the depth of a typical repository, the main process driving the fuel matrix
dissolution and the subsequent release of fission products and heavier actinides is radiolysis of
groundwater. The oxidants produced upon radiolysis of groundwater are capable of oxidizing
U(IV) to the considerably more soluble U(VI) and thereby solubilize the fuel matrix. Previous
studies have shown that the most important oxidant in these systems is H2O2. To assess the
long-term leaching behavior of UO2, the oxidative dissolution of UO2 pellets was studied at
high H2O2 exposures (expressed as amount of oxidant consumed per surface area) ranging from
0.3 mol m-2 to 1.4 mol m-2. The results indicate that the dissolution yield (amount of dissolved
uranium per consumed H2O2) at high H2O2 exposures is significantly lower compared to
previous studies of both pellets and powders and decreases for each H2O2 addition for a given
pellet. This implies a change in redox reactivity by a factor of three to four, which is attributed
to irreversible alteration of the pellet surface. Surface characterization after the exposure to
H2O2, by SEM, XRD and Raman spectroscopy show, that the surface of all pellets is
significantly oxidized.
The same type of study was also performed on Gd-doped UO2 (Gd is used as a burnable neutron
absorber in commercial nuclear fuel) revealing similar trends at different doping levels. The
results of the studies performed on pure UO2-pellets and Gd-doped UO2-pellets are discussed
in combination with relatively recent findings on the reactivity of UO2-powder (exposed to
H2O2 as well as ionizing radiation) as a function of stoichiometry. Finally, the overall impact
of these findings on the safety assessment for deep geological repositories for spent nuclear
fuel is discussed.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
67
Poster 32: Chemical Dosimetry of Femtosecond Electron Bunches Provided
by Laser-Plasma Acceleration
Gérard Baldacchino1, Houda Kacem1, Pierre Forestier-Colleoni1, Jean Daniel Ahui1, Tiberio
Ceccotti1, Sandrine Dobosz Dufrénoy1
1LIDYL, UMR9222 CEA CNRS, Université Paris-Saclay, 91191 Gif-sur-Yvette, France.
The radiobiological effects of the recent protocol in radiotherapy named FLASH seem to be in
relation with the dose rate effect of µs electron pulses. Actually, it spares healthy tissues and
damages tumor cells in a radiotherapy utilization, which improves the treatment prognostic
compared to conventional radiotherapy [1]. This effect could be enhanced by using a higher
dose rate provided by femtosecond electron pulses generated by laser-plasma accelerator. In
this framework, we have studied the chemical effect associated to electron pulses as short as a
few femtoseconds which are provided by high intensity laser (1018 W/cm2) in interaction with
a gas mixture of 99%H2+1%N2.. In these conditions, we expect to produce ultimate dose rates
of electrons in the range of the TGy/s (ie: 1012 Gy.s-1). Their energy belongs to the range 20-
100 MeV. In order to evaluate the dose rate effect in liquid water by chemical fashion, the
determination of radiolytic yields (G-values) of radicals and molecules such as hydrated
electron, hydroxyl radical and hydrogen
peroxide is mandatory. As G-value is the limit
value at dose = 0 of C/d, we first determined
the doses d by simulation using GEANT4
program and electron counting at every shot.
Then, we have used fluorescence spectroscopy
for measuring sensitively the concentrations C
of the above-mentioned species. Then the
scavenging method using Resazurin and
Ampliflu Red as described in ref [2] gives G-
values determination as depicted in figure 1.
The comparison with G-values obtained under
-rays were performed. We will show that
electrons bunches provided by the UHI100
installation at Saclay [3] have produced a small
dose rate effect because hydrated electron and hydroxyl radical have G-values 0.026 and 0.023
µmol.J-1 respectively. H2O2 one seems increased. It will be discussed as well. As these yields
account for the species escaped from recombination in the spurs, molecules could be then
favored because they are the result of radical-radical reactions.
References
1. Favaudon, V., Fouillade, C., Vozenin, M.C. (2015) Ultra-high dose-rate, "flash" irradiation
minimizes the side effects of radiotherapy. Cancer Radiothérapie. 19, 526-531.
2. Baldacchino, G., Brun, E., Denden, I., Bouhadoun, S., Roux, R., Khodja, H., Sicard-Roselli, C.
(2019) Importance of radiolytic reactions during high‑LET irradiation modalities: LET effect, role of
O2 and radiosensitization by nanoparticles. 10, 1-21.
3. Maitrallain, A., Audet, T.L., Dobosz Dufrénoy, S., Chancé, A., Maynard, G., Lee, P., Mosnier, A.,
Schwindling, J., Delferrière, O., Delerue N, Specka, A., Monot, P., Cros, B. (2018) Transport and
analysis of electron beams from a laser wakefield accelerator in the 100 MeV energy range with a
dedicated magnetic line NIMA: Accelerators, Spectrometers, Detectors and Associated Equipment.
908,159-166.
Figure 1. Resorufin (RN) concentration as a
function of the dose delivered by electron bunches
@ UHI100 installation. Slope at d=0 gives the G-
value of OH, here under N2O bubbling.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
68
Poster 34: Studying Nascent Proton-Driven Radiation Chemistry in H2O in
Real Time Using Laser-Based Sources
M. Coughlan1*, N. Breslin1, M. Yeung1
, H. Donnelly1, C. Arthur1, L.Senje2, M. Taylor1, G.
Nersisyan1, D. Jung1, M. Zepf2 and B. Dromey1
1Department of Physics and Astronomy, Queen’s University Belfast, Belfast, United Kingdom 2Helmholtz-Institut Jena, D-07743 Jena, Germany
Understanding the effects of ion interactions in condensed matter has been a focus of research
for decades. While many of these studies focus on the longer term effects such as cell death or
material integrity, typically this is performed using relatively long (>100 ps) proton pulses from
radiofrequency accelerators in conjunction with chemical scavenging techniques [1].
As protons traverse a material, they generate tracks of ionisation that evolve rapidly on
femtosecond timescales. Recently, measurements of few-picosecond pulses of laser driven
protons have been performed via observation of transient opacity induced in SiO2 with sub-
picosecond resolution [2]. Here we present results showing a dramatic difference in the
solvation of electrons generated due to the interaction of relativistic electrons/X-rays and
protons in liquid water. The role of ionisation tracks and subsequent formation of nanoscale
cavities in water on the extended recovery time is discussed.
References
[1] G. Baldacchino, Radiation Physics and Chemistry, 77, 1218-1223 (2008). [2] B.Dromey, et al. Nature Communications, 7, 10642
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
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WEDNESDAY 11TH SEPTEMBER 16:00-17:00
POSTER SESSION 2
(ODD NUMBERS)
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
70
Poster 1: Femtosecond Resolution for Picosecond Radiolysis Using Electron
Pump-Repump-Probe Spectroscopy
S.A. Denisov and M. Mostafavi
Laboratory of chemical physics UMR8000/CNRS, Université Paris-Saclay, Orsay, France
For decades electron picosecond radiolysis
set-ups remain workhorses of fast time-
resolved radical chemistry despite presence
of subpicosecond electron accelerators.
The list of systems where later could be
applicable is rather short despite high
efficient doses, due to the effect of the
group velocity mismatch of the electron
and the light in the sample what limits
samples length to sub-mm paths [1].
Meanwhile the concentration (manifested
in optical density) of produced radicals is a
crucial issue for radiolysis studies in sub-
and picosecond regimes.
In our work, the newly implemented
technique of 3 pulse electron pump (5 ps) –
optical repump by laser (110 fs) and probe by
with light (150 fs) on the ELYSE platform
(Université Paris-Saclay, Orsay) will be
discussed in details. This technique
reinforces existing platform by opening new
research fields earlier inaccessible due to
time-resolution issues of electron
accelerator.
The electron solvation mechanism in water and other solvents will be revisited. Along with
that, perspective experiments accessible to three pulse spectroscopy will be discussed,
revealing research fields, e.g., dissociative electron attachment in liquids previously directly
unreachable for existing time-resolved radiolysis experimental set-ups limitations [2-3].
Reference(s) 1. Yang, J.; Kan, K.; Kondoh, T.; Yoshida, Y.; Tanimura, K. and Urakawa, J. Femtosecond pulse
radiolysis and femtosecond electron diffraction. Nucl Inst Methods Phys Res A 2011, 637, 24–33
2. Ma, J.; Wang, F.; Denisov. S.A.; Adhikary, A. and Mostafavi, M. Reactivity of prehydrated
electrons toward nucleobases and nucleotides in aqueous solution. Sci Adv 2017, 3, e1701669
3. Ma, J.; Kumar, A.; Muroya, Y.; Yamashita, S.; Sakurai, T.; Denisov, S.A.; Sevilla, M.D.;
Adhikary, A.; Seki, S. and Mostafavi, M. Observation of dissociative quasi-free electron attachment
to nucleoside via excited anion radical in solution. Nat Commun. 2019, 10, 102.
Figure 1. Optical density evolution of
solvated electron signal @620 nm,
@1200 nm excited by repump (780 nm) pulse
after passage of 5 ps electron pulse.
Relaxation of the transient signals occurs after
less than 270 fs, corresponding to the
transition from p state to the s-like state.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
71
Poster 3: Molecular Simulations of the Oxidative Radiolysis of two Inverse
Peptides: Methionine Valine and Valine Methionine
P. Archirel1, Ch. Houée-Lévin1 and J. L. Marignier1
1Laboratoire de Chimie Physique, Université Paris-Sud, 91405 Orsay, France
Oxidative radiolysis of the peptides has been performed at the Elyse facility of the LCP. The
two peptides undergo very different processes, as can be seen on the absorption spectra
recorded at different times and concentrations. We have also performed molecular simulations,
in order to interpret these spectra. Our method associates Monte-Carlo sampling of the nuclear
configurations, DFT and TDDFT calculations of the electronic structure and PCM simulation
of the solvent [1,2]. The results enable a fine understanding of the two species:
1. Met-Val displays a main band at 390 nm and no concentration effect. This is due to the
H atom uptake leaving a neutral radical Met-Val (-H) stabilized by a (2c-3e) SN bond.
This species is very stable and undergoes no bimolecular reaction with neutrals.
2. Val-Met displays a complex spectrum with at least three species, see figure 1, left, and
a striking concentration effect. The three species are plausibly a Val-Met (-H) radical
at high energy (285 nm), the Val-Met+ cation, stabilized by a (2c-3e) SO bond at middle
energy (367 nm) and a (Val-Met)2+ dimer cation, stabilized by a (2c-3e) SS bond, at
lower energy (540 nm), see figure 1, right. This last species can be formed either by
direct oxidation of neutral dimers present in solution, and by bimolecular dimerization
of cation monomers. This last species has not been simulated, but can be inferred from
simulations of the Met2+ cation [3].
Figure 1 Oxidative radiolysis of Val-Met: measured (left) and simulated spectra (right) of a
neutral radical (black curve), the cation (red curve) and the dimer (green curve)
References
1. Gaussian 09 RevD01 Gaussian Inc. Wallingford CT, 2013
2. Wang, F. Horne, G. Pernot, P. Archirel, P. and Mostafavi, M. J. Phys. Chem. B 122 (2018), 7134-
7142
3. Archirel, P. Bergès J. and Houée-Lévin, Ch. J. Phys. Chem. B 120 (2016), 9875-9886
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
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Poster 5: Comprehensive Model for X-ray Induced Damage in Protein
Crystallography
D. Close, W. Bernhard
Acquisition of X-ray crystallographic data is always accompanied by structural degradation
due to the absorption of energy. The application of high fluency X-ray sources to large
biomolecules has increased the importance of finding ways to curtail the onset of X-ray induced
damage. A significant effort has been underway with the aim of identifying strategies for
protecting protein structure. A comprehensive model is presented that has the potential of
explaining, both qualitatively and quantitatively, structural changes induced in crystalline
protein at ~100 K. The first step is to consider the qualitative question, what are the radiation
induced intermediates and expected end products? The aim of this presentation is to assist in
optimizing these strategies through a fundamental understanding of radiation physics and
chemistry with additional insight provided by theoretical calculations performed on the many
schemes presented.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
73
Poster 7: Electron Irradiation Treatment of Nanodiamonds
C. Laube1, J.Zhou2, A.Kahnt1, W. Knolle1, Bernd Abel1
1Leibniz Institut of Surface Engineering, Leipzig, Germany, 2Helmholtz Centre of Environmental Research UFZ, Leipzig, Germany
Nanodiamonds (NDs) offer great potential on multiple fields of research such as medical and
sensory application. Herein, the tailoring of the ND surface functionalities and color center
formation inside the diamond lattice can be regarded as key factors for the suitability of the
NDs for these applications. Especially the efficient formation of NV color centers lies within
the focus of modern application. In this work, we demonstrated the application of electron
irradiation as a powerful tool for tailoring these properties. In particular we demonstrated the
efficient surface modification of NDs based on a pulse radiolysis approach of ND suspension.
As a test model we established the efficient surface chlorination of NDs by electron irradiation
of ND suspension in halogenated solvents.1 Furthermore, electron irradiation was applied for
the effective formation of lattice vacancies, in order to enhance the formation of NV centers.
Within a comprehensive study we demonstrated that the formation and the resulting properties
of NV centers can be controlled via irradiation treatments, parameters and the surface
functionalities.2
Reference(s)
1. J. Zhou, C. Laube, W. Knolle, S. Naumov, A. Prager, F.-D. Kopinke and B. Abel, Diamond
and Related Materials, 2018, 82, 150-159.
2. C. Laube, T. Oeckinghaus, J. Lehnert, J. Griebel, W. Knolle, A. Denisenko, A. Kahnt, J.
Meijer, J. Wrachtrup and B. Abel, Nanoscale, 2019, 11, 1770-1783.
Figure 8 Shematic illustration of the preparation approaches
for the nanodiamond surface chlorination (above)
and NV center formation (below).
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
74
Poster 9: Hydrogen Production by Steel Anoxic Corrosion under Gamma
Irradiation
Lina Giannakandropoulou1, Benoît Marcillaud1, Stéphane Poirier1, Hortense Desjonqueres1,
Charles Wittebroodt2, Gérard Baldacchino3
1Institute for Radiological Protection and Nuclear Safety (IRSN), PSN-RES/SCA/LECEV, BP68, Gif-sur-Yvette, France;
2Institute for Radiological Protection and Nuclear Safety (IRSN), PSE-ENV/SEDRE/LETIS, BP17,
Fontenay-aux-Roses; 3LIDYL, Université Paris-Saclay, Atomic Energy and Alternative Energy Commission (CEA), Gif-sur-
Yvette, France.
In the framework of the storage of High Level nuclear Wastes (HLW), ANDRA (National
Radioactive Waste Management Agency in France) is planning their isolation in deep
geological disposals. Such a disposal repository concept is based on a multi-barrier system
including large amount of metallic elements such as stainless steel primary canister or carbon
steel casing for HLW disposal gallery. After a period of several decades, anoxic corrosion of
these metal elements will cause a release of hydrogen gas [1]. Simultaneously, the radiation
emitted by radioactive wastes would lead to the radiolysis of the water present in the
geological formation. This process may lead to a production of additional hydrogen gas and
other redox species likely to modify the redox conditions of the aqueous medium as well as the
corrosion processes of the steel and therefore, the hydrogen production [2].
This study aims at assessing the influence of
-irradiation on H2-production rate through the
anoxic corrosion of carbon steel process. Two
experimental stainless steel cells are placed in an
irradiation chamber IRMA (IRSN facility)
where they are exposed to -radiation of 60Co
(50 Gy/h) for twelve days. The first cell contains
carbon steel coupons (15 gr) immerged in pure
deaerated water (100 mL) and the second cell
contains only pure deaerated water. An He-gas
flows through these cells to a gas chromatograph
for measuring the evolution of H2-production
before, during and after irradiation. Post-mortem analysis are then performed on liquid and
solid phases. Metallic samples is structurally characterized for the identification of the formed
corrosion products upon their surfaces with XRD, μRaman spectroscopy and SEM-EDS
microscopy. The loss of mass of the coupons is measured in order to estimate the carbon steel
corrosion rate. Liquid samples are analysed for their Eh and pH values. In parallel, UV-Vis
spectroscopy is used to determine the concentration of both dissolved Fe2+ and Fe3+ ions. A
fluorescence method is used to assess the hydrogen peroxide (H2O2) concentration. Finally,
kinetics are compared with those obtained by simulations using Chemsimul software. First
results on H2-production show that our experiment allows us to distinguish in time the
contributions of the solid phase (corrosion) and the radiolytic processes in the bulk of the liquid
phase. These results are also supported by simulation in the homogeneous liquid phase but
needs an heterogeneous approach modelling the interface processes.
References
1. Smart, N.R., Rance, A.P., Werme, L.O., 2008.The effect of radiation on the anaerobic corrosion of steel. Journal of Nuclear Materials 379, 97-104.
2. Pimblott, S. M. and LaVerne J. A., 1992. Molecular product formation in the electron radiolysis of
water. Radiation Research 129(3): 265-271.
Figure 1 : µRaman spectra indicates the presence of
magnetite at 675 nm.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
75
Poster 11: Radiolytic Degradation of an Extractant for Actinides, HONTA
— a Comparative Study of Direct and Indirect Radiolysis Processes
Y. Kumagai1, T. Toigawa1, S. Yamashita2, T. Matsumura1
1Japan Atomic Energy Agency, Ibaraki, Japan; 2The University of Tokyo, Ibaraki Japan.
Ionizing radiation induces degradation of organic molecules. This action of ionizing radiation
needs to be incorporated in designing and safety evaluation of solvent extraction processes for
separation of radioactive elements [1]. A reliable estimation of the effect of radiolysis requires
understanding of the degradation mechanism as well as basic data regarding the extractant
degradation and its radiolytic products. This study focuses on a promising extractant for
separation of actinides from lanthanides, hexaoctyl- nitrilotriacetamide (HONTA) [2]. We have
investigated the radiolysis of HONTA by LC-MS/MS analysis of radiolytic products of
HONTA and by UV-visible spectroscopy of its radical transient using pulse radiolysis
technique. In these experiments, radiolysis of neat HONTA and that of HONTA in dodecane
solvent are compared in order to understand the degradation mechanism.
The samples for the product analysis were irradiated by 60Co γ-ray (60Co irradiation facility,
QST Takasaki) and were analysed by an LC-MS/MS system (Shimadzu, LCMS-8300). The
mass-chromatograms for the irradiated neat HONTA and 10 mM HONTA in dodecane are
shown in Figure 1. We found 43 products, in total, of HONTA degradation. Among them, 14
products were commonly observed in the radiolysis of neat
HONTA and the dodecane solution, 20 products were only
found in the neat HONTA, and 9 products are characteristic
for the dodecane solution. Indeed, 14 out of 43 products are
common in these two, although the initial radiolysis
processes in these samples must be different, i.e. direct
ionization and excitation of HONTA occur under neat
condition, whereas the degradation of HONTA is due to
reactions of radicals from dodecane radiolysis in the
solution. This result suggests that the direct and the indirect
processes have a common reaction pathway. Therefore, we
measured absorption spectra of transient species by using a
nano-second pulse radiolysis system. (LINAC facility, Univ.
Tokyo) in order to investigate the reaction pathways. The
measured spectra had similar shapes in this time domain
regardless of the HONTA concentrations. This indicates that
there is a common transient both in the radiolysis of neat
HONTA and of dodecane solution of HONTA. Consistently
with the product analysis, the result of the pulse radiolysis
experiment indicates a common reaction pathway between
the direct and the indirect radiolysis.
Acknowledgment: This work was supported by JSPS KAKENHI Grant Numbers JP18K05001.
References
3. Mincher, B.J., Modolo, G., and Mezyk, S.P. (2009) Review Article: The effects of radiation
chemistry on solvent extraction 3: A review of actinide and lanthanide extraction. Solvent Extr. Ion
Exch., 27, 579-606
4. Sasaki, Y., Tsubata, Y., Kitatsuji, Y., and Morita, Y. (2013) Novel Soft-Hard Donor Ligand,
NTAamid, for Mutual Separation of Trivalent Actinoids and Lnthanoids, Chem. Lett., 42, 91-92.
Figure 1 Mass chromatograms of the irradiated samples (130 kGy); (a) neat HONTA, (b) 10mM HONTA in n-dodecane.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
76
Poster 13: New Explanation for Radiosensitization by Gold Nanoparticles:
Chemical Effect
V. Shcherbakov, N. Chen, S.A. Denisov and M. Mostafavi
Laboratory of chemical physics/CNRS_Université Paris-Saclay, Orsay, France
Gold nanoparticles (AuNPs) are presented to be an efficient radiosensitizer for cancer
radiotherapy [1]. During the last decades, many important works were performed to show the
radiosensitization by different particles for different tumors. But still, there is no explanation
for AuNPs radiosensitizating effect. Physical explanation based on Compton, photoelectric and
Auger effects cannot explain the radiosensitizing effect in solutions, because the nanomolar
concentration of AuNPs does not change dose deposition in the solution. Therefore, other ideas
were proposed such as overproduction of ∙OH radicals [2] due to special properties of
interfacial water around nanoparticles and
scavenging of excess electrons [3, 4] what
increases the concentration of ∙OH radicals
around the nanoparticles.
In the present work, we show by pulse radiolysis
that AuNPs react neither with reducing radicals:
pre-solvated electron, solvated electron (e-s), ∙H
nor oxidizing one ∙OH, what is manifested in the
same e-s formation yields (5 ps) in the presence
and absence of AuNPs; and the same decay of e-
s in microsecond time range [5]. In addition,
unchanged e-s decay in the presence of AuNPs
showed that overproduction of OH radicals is not
occurring. In the present work we perform a new
approach to show the effect of AuNPs in
radiosensitization.
As biological systems are complex, therefore here we used simple organic models to conclude
on the mechanism of the radiosensitizing effect of AuNPs. By gamma radiolysis, we show that
in an irradiated solution of 2-propanol in the presence of AuNPs the radiolytic yield of acetone
– the product of oxidation of alcohol, is higher than in the absence of nanoparticles (Figure 1).
Such studies were carried out for other organic compounds in order to confirm the effect of
gold nanoparticles on this radiolytic enhancement. In our work we will propose the detailed
mechanism and discuss how it can explain radiosentisization by AuNPs.
References:
1. Wang, H., Mu, X., He, H., & Zhang, X. D. (2018). Cancer radiosensitizers. Trends in pharmacological sciences, 39(1), 24-48.
2. Gilles, M., Brun, E., & Sicard-Roselli, C. (2018). Quantification of hydroxyl radicals and solvated
electrons produced by irradiated gold nanoparticles suggests a crucial role of interfacial water.
Journal of colloid and interface science, 525, 31-38.
3. Ghandi, K., Wang, F., Landry, C., & Mostafavi, M. (2018). Naked Gold Nanoparticles and hot
Electrons in Water. Scientific reports, 8(1), 7258.
4. Ghandi, K., Findlater, A. D., Mahimwalla, Z., MacNeil, C. S., Awoonor-Williams, E., Zahariev, F.,
& Gordon, M. S. (2015). Ultra-fast electron capture by electrosterically-stabilized gold nanoparticles.
Nanoscale, 7(27), 11545-11551.
5. Shcherbakov, V., Denisov, S.A., Ghandi, K., Mostafavi, M., Pulse radiolysis study of AuNPs
solutions. (to be published)
Figure 1. The dose dependent of acetone
formation in 2-propanol solution in the
presence and absence of AuNPs.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
77
Poster 15: Study on the Dose Enhancement in Water by Activation of
Clusters of Nanoparticles of High-Z Materials with a 6 MeV True Varian
Linac
B. Villagomez-Bernabe1,2 and F. Currell1,2
1Chemistry Department, The University of Manchester, Manchester, UK; 2Dalton Cumbrian Facility, Cumbria, UK.
During the last decade, different nanomaterials have been implemented for biomedical
applications in Nanomedicine, such as imaging agents [1] and drug delivery agents [2].
Furthermore, different types of nanoparticles are being studied as radiosensitizers in cancer
treatment [3,4]. This work aims to calculate through Monte Carlo simulations the dose
enhancement in water for three different nanoparticles composition such as gold, silver and
gadolinium in order to compare their effectiveness based only on the physical interactions
between gamma irradiation and the nanoparticles, i.e. without taking into account the influence
of the radicals formed by each type of nanoparticles. Nevertheless, as far as the authors are
aware, such a computational study involving clustering of nanoparticles has not been published
to date.
The present work is divided into two stages, during the first
stage, the random positions of the nanoparticles inside a
water sphere were calculated using Wolfram Mathematica.
This mimics the sub-cellular distribution of nanoparticles
commonly observed using microscopy. Those coordinates
were used to create a parameter file in TOPAS [5] with the
information of the position, material and size of the
nanoparticles. The geometry set-up created with the
parameter file is shown in Fig. 1, where a cluster of
nanoparticles was loaded into TOPAS for posterior
irradiation with a 6 MeV True Varian Linac obtained from
the International Atomic Energy Agency website. Then, a
phase space file placed around the cluster of the
nanoparticles was used to record all electrons going out from the cluster. The final stage
involves the releasing of all particles from the space phase file previously recorded during stage
1 into a water phantom in order to measure the dose deposited in radial bins around the cluster.
The Geant4-DNA physics list was used to track low energy electrons down to 10 eV. The radial
dose distribution for each type of nanoparticle were compared against each other and plotted
for better visualization.
Reference(s)
1. Rippel R.A. and Seifalian A.M. (2011) Gold Revolution -Gold nanoparticles for modern medicine
and surgery. Journal of Nanoscience Nanotechnology, 11, 7340-48.
2. Ghosh P., Hang G., De M., Chae K.K. and Rotello V.M. (2008) Gold nanoparticles in delivery
applications. Advanced Drugs Delivery Reviews, 60, 1307-15.
3. McMahon S.J. et al (2011) Nanodosimetric effects of gold nanoparticles in megavoltage radiation
therapy. Radiotherapy Oncology, 100, 412-416.
4. Taupin F. et al. (2015) Gadolinium nanoparticles and contrast agents as radiation sensitizers.
Physics in Medicine and Biology, 60, 4449-64.
5. Perl, J. et al. (2012) TOPAS: an innovative proton Monte Carlo platform for research and clinical
applications. Med Phys., 39, 6818-37.
Fig. 1. cluster of
nanoparticles randomly
distributed.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
78
Poster 17: Effects of Additives on Radiation-Induced DNA Damage: From
the Viewpoints of Free Radical Scavenging and Chemical Repair
H. Yu1, K. Fujii2, A. Yokoya2 and S. Yamashita1
1The University of Tokyo, Tokyo, JAPAN; 2Natinal Institutes for Quantum and Radiological Science and Technology (QST), Chiba, JAPAN.
1. INTRODUCTION
Radiation-induced DNA damage can be reduced by small amount of additives like
antioxidants. Such additives can repair unstable oxidative damage intermediately produced in
DNA by reductive reaction (chemical repair) as well as remove oxidizing radicals such as •OH
produced as a result of water radiolysis (radical scavenging). Low concentration of additives
cannot remove all of the oxidizing radicals, therefore, the chemical repair process must be more
important. We investigated the effect of additives against radiation damage to DNA. For this
purpose, pulse radiolysis experiments were conducted to observe the additive’s reactions not
only with radicals produced by water radiolysis but also with a tentatively oxidized DNA model
compound. In this study, dGMP (deoxyguanosine monophosphate, purchased from Thermo
Fisher Scientific) was used as model compound of DNA moiety. In addition, a gel
electrophoresis was conducted to evaluate the yield of stable DNA damage.
2. EXPERIMENT
Pulse radiolysis was conducted at the LINAC facility of the University of Tokyo. Details of
the apparatus are described in elsewhere[1].
Plasmid DNA, pUC18, was extracted from cultured Escherichia coli (JM109) and purified
by dialysis to remove organic impurities. Dilute aqueous solutions and films of the plasmid
DNA were irradiated with X-rays and stable DNA damage were detected and quantified by an
agarose gel electrophoresis method[2].
As additives, we used Tris-EDTA (TE), which are the solutes of pH buffer often used for
DNA storage, and typical antioxidants such as ascorbic acid (purchased from Fujifilm Wako)
and flavonoid rutin (received from Toyo Sugar or purchased from Fujifilm Wako).
3. RESULTS & DISCUSSION
Transient absorption spectra of the scavenging reaction of rutin toward •OH had at least three
peaks, which were attributed to the products of OH adduct, hydrogen atom subtraction, and
electron subtraction. The ratio of the peak intensities was not constant, indicating an
intramolecular transformaton following the scavenging reaction. On the other hand, the reacion
of rutin toward tentatively oxidized dGMP radical showed a clear peak in the spectra, which
was the same as the peak corresponding to hydrogen abstraction observed for the scavenging
reaction as described above.
Purification by dialysis resulted in higher yields of stable DNA damage induction, indicating
that non-negligible impurities could protect the DNA from radiation damage. The damage
yields in dilute aqueous solutions were much higher than those in hydrated plasmid DNA films.
This suggests that additional damage is produced due to the indireact actions of radicals
produced by watar radiolysis.
References
[1] K. Hata, et al., J. Radiat. Res., 52, 15 (2011).
[2] A. Yokoya et. Al., J. Am. Chem. Soc. 124, 8859 (2002).
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
79
Poster 19: Solvation Effects on Dissociative Electron Attachment to
Thymine
Jorge Kohanoff 1 and Bin Gu1,2
1Atomistic Simulation Centre, Queen’s University Belfast, Belfast BT7 1NN, U.K.; 2Department of Physics, Nanjing University of Information Science and Technology, Nanjing 210044,
China.
Ionizing radiation can excite the cellular medium to produce secondary electrons that can
subsequently cause damage to DNA. The damage is believed to occur via dissociative electron
attachment (DEA). In DEA, the electron is captured by a molecule in a resonant antibonding
state and a transient negative ion is formed. If this ion survives against electron
autodetachment, then bonds within the molecule may dissociate as energy is transferred from
the electronic degrees of freedom into vibrational modes of the molecule.
We present a model for studying the effect that transferring kinetic energy into the vibrational
modes of a molecule has on a DNA nucleobase. To simulate the effect of the additional energy
that would be introduced due to a DEA event, we vertically attached an excess electron to the
system and introduced additional vibrational energy to the N−H bond. We can tune the
vibrational energy of a molecular bond by increasing the velocities and hence the kinetic
energies of the constituent atoms.
We found that the breaking of an N−H bond and releasing a hydrogen atom, which in the gas
phase requires 1.67 eV, is strongly affected by the aqueous environment. When there is a
hydrogen bond between the N−H of the nucleobase and a surrounding water molecule, there is
no guarantee that the bond breaks even when up to 5 eV of additional energy is inserted into
the bond. The reason for this is that this hydrogen bond rapidly channels the kinetic energy
away from the N−H, into the surrounding water molecules, and back into the nucleobase.
Fig. 2 The reaction channels of the (Transient negative ion)TNI of thymine with low energy
dissociative electron attachment (DEA) in aqueous solvent, with the relevant potential energy surface
(PES) shown as functions of the N-H distance. Reference
McAllister, M., Kazemigazestane, N., Henry, L. T., Gu, B., Fabrikant, I., Tribello, G. A., & Kohanoff,
J. (2019). Solvation Effects on Dissociative Electron Attachment to Thymine. The Journal of Physical
Chemistry B, 123(7), 1537–1544.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
80
Poster 21: Effect of Supports on Metal-Nanoparticle Catalysts: The
Radiolytic H2 Evolution Reaction
Gifty Sara Rolly,1 Ronen Bar-Ziv 2 and Tomer Zidki 1
1Department of Chemical Sciences, Ariel University, Ariel, Israel; 2Department of Chemistry, Nuclear Research Centre Negev, Beer-Sheva, Israel.
The performance of the silica-supported M0 nanoparticles as catalysts for water reduction was
studied using the strongly-reducing ·C(CH3)2OH radicals at acidic and alkaline media. It was
found that supporting metal nanoparticles (M0-NPs, M = Pt, Au, Ag) on an "inert" support such
as SiO2 alters the catalytic properties of the metals. This effect depends both on the nature of
M and on the concentration of the composite nanoparticles. At low nanocomposite
concentration: for M = Au nearly no effect is observed; for M = Ag the support decreases the
catalytic reduction of water, and for M = Pt the support initiates the catalytic process. At high
nanocomposite concentration: for M = Au the reactivity is considerably lower, and for M = Ag
or Pt, no catalysis is observed. Furthermore, for M = Ag or Pt H2 reduces the ·C(CH3)2OH
radicals. Changing the medium from alkaline to acidic pH did not affect these trends.
Therefore, we conclude that the metal oxide support affects the M0-NPs redox properties.
Below is the proposed mechanism pathways for the production of H2 and the deactivation of
H2 evolution.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
81
Poster 23: Radiation-Induced Redox Chemistry of Californium-249
David S. Meeker1,2, Gregory P. Horne1, Travis S. Grimes1, Peter R. Zalupski1, James F.
Wishart3, Stephen P. Mezyk4, and Thomas E. Albrecht-Schmitt2
1 Idaho National Laboratory, Center for Radiation Chemistry Research, Idaho Falls, ID, P.O. Box
1625, 83415, USA 2 Florida State University, Department of Chemistry and Biochemistry, Tallahassee, FL, 32306-4390,
USA. 3 Brookhaven National Laboratory, Department of Chemistry, Upton, New York, 11973, USA.
4`California State University Long Beach, Department of Chemistry and Biochemistry, Long Beach,
CA 90804, USA.
A complete understanding of californium chemistry necessitates knowledge of its
radiation-induced redox behavior, owing to its inherent nuclear instability propagating self-
radiolysis. Only a handful of studies have investigated californium radiation chemistry, due to
lack of element availability and difficulty associated with handling highly radioactive material.
To date, reaction rate coefficients (k) have only been experimentally determined for the
reduction of Cf(III) by the hydrated electron (e¯aq, k > 3 × 109 M–1 s–1) from water radiolysis,
and subsequent decay of the corresponding transient Cf(II) (k = (7 ± 1) × 105 s–1)[1]. However,
there are a number of other important transient radiolysis products radiolytically generated in
solutions pertinent to californium manipulations, e.g., the hydrogen atom (H•, Eo = 2.31 V),
hydroxyl radical (•OH, Eo = –2.73 V), and nitrate radical (•NO3, Eo = –2.3 – –2.6 V). These
species are more than capable of influencing the redox behavior of californium, and have been
shown to do so with a number of actinides, e.g., neptunium and americium.[1,1,1] Here we
present the results from the first time-resolved picosecond pulsed electron radiolysis
measurements for californium-249. The reaction rate coefficients were determined by direct
decay of the observed species or via competition kinetics. For the reductive reactions of Cf(III)
with the e¯aq and H• transients, the reaction rate coefficients were measured to be (7.11 ± 0.18)
× 1010 and (2.61 ± 0.54) × 108 M−1 s−1, respectively, while studies for the oxidation of Cf(III)
by the •NO3 and •OH species yielded (2.0 ± 0.5) × 108 and (7.2 ± 0.6) × 108 M−1 s−1, respectively
References
1. Sullivan, J.; Morss, L.; Schmidt, K.; Mulac, W.; Gordon, S. Pulse Radiolysis Studies of
Californium (III) in Aqueous Perchlorate Solution. Evidence for the Preparation of Californium
(II). Inorg. Chem., 1983, 22, 2339.
2. Horne, G. P.; Grimes, T. S.; Mincher, B. J.; Mezyk, S. P. Re-evaluation of Neptunium-Nitric
Acid Chemistry by Multi-Scale Modelling. Journal of Physical Chemistry B, 2016, 120 (49), 12643–12649.
3. Grimes, T. S.; Horne, G. P.; Dares, C. J.; Pimblott, S. M.; Mezyk, S. P.; Mincher, B. J. Kinetics
of the Autoreduction of Hexavalent Americium in Aqueous Nitric Acid. Inorganic Chemistry,
2017, 56 (14), 8295-8301.
4. Horne, G. P.; Grimes, T. S.; Bauer, W. F.; Dares, C. J.; Pimblott, S. M.; Mezyk, S. P.; Mincher,
B. J., Effect of Ionizing Radiation on the Redox Chemistry of Penta- and Hexavalent
Americium. Inorganic Chemistry, submitted 28th March 2019.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
82
Poster 25: Reduction of Cobaoxime-Based Complexes: Mechanisms,
Products and Implications
A. Kahnt1, E. Hofmeister2, T. Ullrich3, K. Hanus1 and M. von Delius2
1Leibniz Institute of Surface Engineering (IOM), Leipzig, Germany. 2Institute of Organic Chemistry and Advanced Materials, University of Ulm, Ulm, Germany.
3Chair of Physical Chemistry I, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
Cobaltoxime based complexes have attracted strong interest in the past and present. Decades
ago the focus was set on alkyl and alkenyl cobaloximes as vitamin B12 model system1. Later,
new interest arose regarding this class of compounds owing to the fact that Co(dmgBF2)2
catalyses the reduction of protons in acidic solutions.2 In this regard, cobaloxime complexes
are considered as candidates for the “Holy Grail” in the field of renewable energy - that is the
formation of renewable fuel from solar energy, to potentially meet the future energy demands
without the use of fossil fuel. Several cobaltoxime based systems containing organic and/or
inorganic chromophores3 for light harvesting have been coordinated to the cobalt centre of
cobaloxime complexes and have been successfully tested for the photocatalytic reduction of
water.
But, plenty of this systems prompt to a up to hours lasting induction period for the
photocatalytic reduction of water.4 Surprisingly, the reasons for such a phenomenon remain
largely unknown4 and comes hardly in line with the usual
proposed reaction mechanisms postulating a reduction
from a CoIII to a CoI species. Our past work5,6 related to
photocatalytic water reduction triggered our interest in the
understanding of this mechanism. In line with the latter,
we conducted a full fledge spectroscopic and kinetic
investigation of the reduction of mono-nuclear Co-
complexes by pulse radiolysis assays, however, we found
solid evidence that a final product of the reduction process
was a dinuclear complex.6 From this finding we derived
the implication that for an efficient induction period free
photo-catalysts least two Co-centres like in the CoIII double salt presented in figure 1 are
required. For these new and very efficient class of proton reduction photo-catalysts detailed
investigations of the reduction mechanism by pulse radiolysis were conducted in order to
establish the mechanism behind the found quite efficient proton reduction.7
Reference(s)
1. Prince R.H., Segal, M.G. (1974) Nature, 249, 246-247.
2. Connolly P., Espensson J.H. (1986) Inorg. Chem., 25, 2684-2688.
3. Artero V., Fontecave M. (2013) Chem. Soc. Rev., 42, 2338-2356.
4. Du P., Eisenberg R. (2012) Energy Environ. Sci., 5, 6012-6021.
5. Peuntinger K., Lazarides T., Daphnomili D., Charalambidis G., Landrou G., Kahnt A., Sabatini R.,
McCamant D., Gryko D.T., Coutsolelos A., Guldi D. M. (2013) J. Phys. Chem. C, 117, 1647-1655.
6. Kahnt A., Peuntinger K., Dammann C., Drewello T., Hermann R., Naumov S., Abel B., Guldi D.
M. (2014) J. Phys. Chem. A, 118, 4382-4391.
7. Hofmeister, E., Ullrich, T., Petermann L., Hanus, K., Rau, S., Kahnt, A., von Delius, M. (2019) Angew. Chem. Int. Ed., under preparation.
Figure1. New generation of
Co-double salts as core
structure for novel proton
reduction photo-catalysts [7].
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
83
Poster 27: γ-Radiolysis of Thermal Transition Phases in Boehmite
Patricia L. Huestis1 and Jay A. LaVerne1
1Department of Physics and Notre Dame Radiation Laboratory, University of Notre Dame, Notre
Dame, IN, USA.
Over 200 million liters of high level waste (HLW) reside in the Hanford Waste Tanks. These
tanks contain legacy waste from the Cold War era and are chemically complex due to high
nitrate concentrations, high pH, and large radiation fields. Boehmite (γ-AlOOH) is a large
component of the solid waste located within the tanks and is especially problematic due to its
longer than predicted dissolution times. Boehmite has a layered structure which consists of an
Al-O lattice hydrogen bonded together via bridging OH groups. The mechanism responsible
for hydrogen production in boehmite is still not well understood.
Boehmite was heated to various temperatures along its dehydration pathway to assess the
structural differences and their effect on the radiolysis of boehmite. Structural changes were
investigated using powder X-Ray Diffraction (pXRD), Raman spectroscopy, nitrogen
adsoption, and Scanning Electron Microscopy (SEM). Radiolytic effects were assessed using
Gas Chromatography (GC) and Electron Paramagnetic Resonance (EPR). Different sizes of
materials were used to investigate the size dependence on the thermal degradation and its effect
on the creation of radiolytic products by gamma rays.
The yield of H2 with respect to energy deposited into the material/water system is nearly
constant for both sizes of material heated below 300°C with the smaller material having a
slightly higher yield. The larger material, when preheated further to 400°C, shows a dramatic
increase in H2 production. Larger material preheated to 550°C as well as smaller material
preheated to both 400°C and 550°C shows a yield consistent with alumina, indicating complete
or near complete dehydration. Initial production of trapped hydrogen radicals within the larger
material in conjunction with the yield for the sample preheated to 400°C suggest that the
hydrogen production mechanism is likely an abstraction reaction by H atoms with surface water
as opposed to a bimolecular combination reaction.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
84
Poster 29: Key Role of the Oxidized Citrate Free Radical in the Nucleation
Mechanism of the Metal Nanoparticles Turkevich Synthesis
Sarah Al Gharib,1,2, Jean-Louis Marignier,1 Adnan Naja,2 Abdel Karim El Omar,2 Sophie Le
Caer,3 Mehran Mostafavi,1 and Jacqueline Belloni1.
1 Laboratoire de Chimie-Physique/ELYSE, UMR 8000 CNRS/UPS, Université Paris Sud, Université Paris-Saclay, Bât. 349, F-91405 Orsay Cedex, France.
2 Laboratoire Physique et Modélisation, Université Libanaise, Tripoli, Lebanon. 3 Laboratoire LIONS, DSM/IRAMIS/NIMBE UMR 3685 CNRS/CEA/Saclay, Université Paris-Saclay,
Bât. 546, F-91191 Gif-sur-Yvette, Cedex, France.
The step-by-step mechanism of the citrate oxidation, of the silver ion reduction [1] [2] into
atoms, and of the nucleation of nanoparticles by the Turkevich method [3] are deduced from
the gamma- and pulse radiolysis yields of dicarboxy acetone (DCA), H2 and CO2 and of silver
ion reduction. Our results demonstrate that the stronger reductant is not citrate (Cit) but the
oxidized radical Cit(-H)•. The formation yields of DCA and CO2 confirm the decarboxylation
process during the Cit(-H)• oxidation. In pulse radiolysis of solutions of sodium citrate and
silver perchlorate, the transient spectra [4] and the kinetics are observed from 20 ps to 800 ms.
In particular, the successive H abstraction from citrate by OH• radicals, then the one-electron
transfer from the citrate radicals Cit(-H)• to silver ions initiating the simultaneous nucleation
and growth of the reduced silver oligomers are observed. The knowledge of the nuclearity-
dependent kinetics and thermodynamics of silver atoms, oligomers and nanoparticles in
solution is used to bracket the standard reduction potentials of the first (≥ 0.4 VNHE) [2] and the
second one-electron transfers from citrate (≤ - 1.2 VNHE) [2]. During the Turkevich synthesis,
the Cit(-H)• radical was shown to be released in the bulk solution from the citrate oxidation by
Ag+ adsorbed on the walls (Figure 1), or directly by the trivalent AuIII ions present in the bulk,
respectively. Then the strong Cit(-H)• reductant alone is able, as in radiolysis, to overcome the
thermodynamic barrier of the very negative potential for the reduction of the free monovalent
ions into atoms that is required to initiate the nucleation and growth (Figure1). The reduction
potentials values of citrate and Cit(-H)• also explain part of the antioxidant properties of citrate.
Reference(s)
1. Marignier, J.L;. Belloni, J. ; Delcourt, M.O. ; Chevalier, J.P Nature, 1985, 317, 344-345.
2. Belloni J., Mostafavi, M., Radiation Chemistry of Clusters and nanocolloids. In Studies in
physical and theoretical chemistry, Radiation Chemistry:, Jonah, C.D. ; Rao, M. (eds), Elsevier,
2001, 87, 411-452.
3. Turkevich, J.; Stevenson, P.C.; Hillier, J. Disc. Faraday Soc. 1951, 55-75.
4. Simic, M.; Neta, P.; Hayon, E. J. Phys. Chem. 1969, 73, 4214-4219.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
85
Poster 31: The Radiation Chemistry of Aqueous PVP Solutions Exposed to
Pulsed E-beam Irradiation: Experiments and Numerical Simulations
C. Dispenza1, M. A. Sabatino1, B. Dahlgren2, M. Jonsson2
1Department of Engineering, University of Palermo, Italy. 2Department of Chemistry, KTH Royal Institute of Technology, Sweden.
Nanogels have recently raised considerable interest in the biomedical field, due to their diverse
applications in tissue engineering, regenerative medicine and drug delivery.
One-pot radiation-induced synthesis of nanogels from dilute aqueous polymer solutions is one
example of a process that has been successfully carried out using electron accelerators equipped
with scanning horn and a conveyor belt. In dilute aqueous systems the radiation energy is
mainly absorbed by water. Upon exposure to ionizing radiation, water is decomposed into OH,
H, eaq-, H2, H2O2 and H3O+. Polymer radicals are formed upon hydrogen abstraction from the
polymer by OH and H. By saturating the aqueous solution with N2O, the strongly reducing
hydrated electron can be converted into a hydroxyl radical.
In the radiation synthesis of nanogels from polymer aqueous solutions, conditions that favor
intramolecular radical-radical reactions are generally employed. Interestingly, these are also
the conditions when scavenging of the primary radicals formed in the radiolysis of water is no
longer quantitative. Under these conditions, a fraction of the hydroxyl radicals can recombine
and produce hydrogen peroxide. This can have a significant influence on the further reactions
in the system. In systems exposed to a sequence of pulses, the formation of H2O2 will eventually
lead to the production of O2. It is therefore desirable to be able to perform both experiments
and numerical simulations on these systems both in order to confirm mechanistic and kinetic
data and to be used as a predictive tool for process optimization.
The obvious first step in the development of the modelling tool is the simulation of single pulse
irradiations to explore the effects of dose per pulse, concentration of polymer and polymer
molecular weight on the kinetics of polymer radical decay. The next step is to model more
complex pulse sequences that resemble conditions used to irradiate large volumes of aqueous
polymer solutions and produce nanogels.
The numerical simulation is based on a deterministic approach encompassing the conventional
homogeneous radiation chemistry of water as well as chemical reactions involving polymer
chains and polymer radicals. As benchmarking, results from a series of experiments on pulsed
irradiation of aqueous PVP-solutions have been used. The simulations qualitatively reproduce
the experimentally observed impact of initial gas saturation (air and N2O) and polymer
concentration on the molecular chain length upon irradiation. The formation of double bonds
as a function of dose as well as the impact of effective dose rate on the final chain length are
also qualitatively reproduced in the simulations and suggests different possible options for
irradiation conditions to tailor the molecular weight and functionality of the synthetized
nanogels to meet application requirements.
Acknowledgements
BD acknowledges the Royal Institute of Technology for financial support.
CD acknowledges the Institute of Nuclear Chemistry and Technology in Warsaw (Poland) for
performing the ebeam irradiations and IAEA CRP F22064.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
86
Poster 33: Internal Structure and Composition of Fukushima-Derived
Particulate Revealed Through Combined Synchrotron and Mass-
Spectrometry Techniques
P.G. Martin1, S. Cipiccia2, D.J. Batey2, Y. Satou3 and T.B. Scott1
1School of Physics, University of Bristol, HH Wills Physics Laboratory, Tyndall Avenue, Bristol, BS8
1TL 2Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE
3Japan Atomic Energy Agency (JAEA) - CLADS, Tomioka, Futaba-gun, Fukushima Prefecture, Japan
Despite the events at the Fukushima Daiichi Nuclear Power Plant (FDNPP) having passed
their eighth anniversary, a considerable amount of work is still ongoing to evaluate
the nature and environmental legacy of the radioactive particulate species [1,2].
Through the application of both laboratory and synchrotron radiation (SR) x-ray tomography
(XRT), the internal structure of a representative sub-mm particle was shown to be highly-
porous – with 24% of the internal volume constituted by void space (Figure 1). Compositional
(elemental) analysis of the particulate material through SR x-ray fluorescence (XRF) detailed
the peripheral enrichment of several elements (including Sr, Pb and Zr). The component of
fissionogenic Cs (134 + 135 + 137Cs) was determined to account for most of the elemental
abundance within the particle with limited contribution from natural 133Cs.
SR x-ray absorption near edge structure (XANES) analysis on several high atomic density
particles located within the bulk particle confirmed them to be U in composition, existing in
the U(IV) oxidation-state, as UO2. The complementary isotopic analysis of this micron scale
uranium material enclosed just below the surface of the particle was subsequently determined
using secondary ion mass spectrometry (SIMS), having spatially referenced their co-ordinate
positions between the different techniques. SIMS mapping revealed the U-rich particle to be
~1 μm in maximum dimension, consisting of enriched U with 3.54 wt% 235U – analogous to
that used in the reactor Unit 1 fuel assemblies [3].
References
[1] Imoto et al., (2017). Scientific Reports, 7 (5409) pp. 12.
[2] Furuki et al., (2017). Scientific Reports, 7 (42731) pp. 10. [3] Fukushima Daiichi NPS - Information Portal. TEPCO (2013).
Figure 1. SR-XRT reconstruction of the representative particle showing the 24% void volume.
Regions of both stainless-steel (orange) and cement (green) composition are shown (as identified
through SR-XRF), as are locations where voids are observed to interact.
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
87
31st MILLER CONFERENCE ON RADIATION CHEMISTRY
September 9-14, 2019, Energus, Workington
88