Measurement of the 241Am(n,2n) reaction cross section using the activation method

G. Perdikakis1,2, C. T. Papadopoulos1, R. Vlastou1, A. Lagoyannis2, A. Spyrou2, M. Kokkoris1, S. Galanopoulos1, N. Patronis1, D. Karamanis3, Ch. Zarkadas2, G. Kalyva2,

and S. Kossionides2

1 Department of Physics, National Technical University of Athens, Athens, Greece

2Institute of Nuclear Physics, NCSR “Demokritos”, Athens, Greece

3 Department of Physics, University of Ioannina, Ioannina, Greece

n_TOF Collaboration

G. Perdikakis

•Motivation

•Experimental

•Analysis

•Results for 241Am(n,2n)

•Theoretical Calculations (in

progress)

•Other reactions studied – Future

Plans

Outline of the talk

G. Perdikakis

Transmutation of MAs - Important Reaction Channels

Neutron emission channels σ(n,xn)

Fission Channels σ(n,xnf)

Not enough experimental data !

Theoretical Predictions

Experimental Investigation of Theoretical Model Parametres required

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Existing Data

241Am: One of the most abundant isotopes in nuclear waste and one of the most radiotoxic elements

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241Am(n,2n)240Am

Energy Range of Interest:

8-12 MeV

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~ 105

n/cm2s

~ 106

n/cm2s

~ 105

n/cm2s

Monoenergetic Neutron Beams @ INP “Demokritos”

p+ or d+ beam

2H(d,n)3He

3H(d,n)4He

5.5MV Tandem VdG

5 – 12 MeV

16 – 20 MeV

7Li(p,n)7

Be150 – 650 keV

Shielding

wall

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The Activation Target

27 Al foil

3mm

Pb shield

37 GBq 241 Am target

Stainless Steel

n Beam

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Irradiation Setup

241Am Target

d+

D filled Gas Cell

BF3 Neutron Counter

n Beam

HPGe

Pb

9cm

ΔΕn: < 100 keV

Parafin

G. Perdikakis

2 m

242Am

2n+240Am

240Pu

n+241Am

n+241Am

3n+239Am

T1/2=50.8h

Outline of the Reaction 241Am(n,2n)240Am

n

γ

FissionE,J,π

5 days of irradiation

for each beam

energy !

987.8 keV (I=73%)

888.8 keV (I=25%)

Most Intense γ-rays:

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@ 10.6 MeV

HPGe spectrum

1014.7 keV 241Am

987.8 keV 240Am

984.5 keV 238Np +154Eu

955.7 keV 241Am

154Eu

ΦN

N=σ

τ

p 1

εFI

NtN

γ

γBp

'''γ

'γ

τ εFI

NN

εF

εF

N

I

I

N

N

N ''

'γ

'γ

γ

γ

τ

p

Reaction Cross

Section

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Results

Results

G. Perdikakis et al. , Phys. Rev. C - In press

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242Am

2n+240Am

240Pu

n+241Am

n+241Am

3n+239Am

T1/2=50.8h

Outline of the Reaction 241Am(n,2n)240Am

n

γ

FissionE,J,π

Hauser Feshbach:

Preequilibrium contribution : Exciton Model

c c

ba

TTT

G. Perdikakis STAPRE/F

dπJ,ε,ρε+UU

ω

2πexp+=UΤ BA,

'BA,

BA,

'JπBA,

1

1

The double-humped fission barrier

Fission

n+X

Saddle A states

Saddle B states

Deformation, β

scission

βΝ

n

Normal states

βΑβΒ

UA UB

ħωΑ

ħωΒ

ρΑ ρΒρΝ

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Main parametres of the calculation

Fission Barrier Parametre UA,UB,ħωΑ,ħωΒ

Level Density, ρ(U,J), at the saddles and at normal deformation

Deduced from experimental data

(V. M. Maslov. RIPL-1 Handbook. TEXDOC-000, IAEA, Vienna, 1998, Ch. 5.)

Transmission Coefficients

for neutrons,Τn

Coupled Channels OMP for actinides

(Ignatyuk et. al. Sov. J. Nucl. Phys. 51, (5), 1990)

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Generalized Superfluid Model of the nucleus

Shell, Superfluid pairing and Collective effects, important for the calculation

Ignatyuk et al, Sov. J. Nucl. Phys 29, (4), 1979

JfJ),(U')Κ(U'Κ)ρ(U'J),ρ(U' rotvibr

a=ã[1+δw·f(U-Econd)]

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Results 241Am(n,F)

Preliminary !!!

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241Am(n,2n)

• 232Th(n,2n) D. Karamanis et al. NIM A 505, 381, (2003)

• n-induced reactions on Ge, Hf and Ir isotopes In progress

• 237Np(n,2n) To be done

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Conclusions

Measurement of the 241Am(n,2n) reaction @ En = 8.8 – 11.4 MeV

Theoretical calculations in progress 241Am(n,2n)

241Am(n,F)

Other measurements

THE END

Results

241Am(n,2n)

Preliminary !!!

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Conclusions and Future Perspectives

Systematic Experimental Investigation of 241Am(n,2n) Reaction Cross Section,

for the first time

Consistent Theoretical Description of 241Am(n,2n) Reaction, in Reasonable

Agreement with Experimental Data.

Experimental Investigation to be Continued at Lower Energies

Improvement of Theoretical Description over the whole energy range

241Am(n,2n)240Am

Results

241Am(n,2n)240Am

241Am(n,f)

Energy Production and Nuclear Waste Transmutation in ADS Systems

Higher Fission/Captu

re ratio

More effective

Transmutation

S. Taczanowski et. al. Applied Energy 75, 97, (2003)

Sub-critical Systems

Transmutation of

Nuclear Waste

Neutrons produced

by Spallation Reaction

in Accelerator

Main Characteristics

Neutron Flux in Reactor Core affected by n-induced reactions

HPGe

Pb shielding

241Am Target

Off Line

Irradiation Setup

241Am Target

d+

D filled Gas Cell

BF3 Neutron Counter

n Beam

Parafin

0 100000 200000 300000 400000

0

1000000

2000000

3000000

4000000

5000000

Neu

tron

Flu

x(c

ou

nts

)

Irradiation Time (sec)

En= 10.6 MeV

Neutron Flux vs Time

5 days of Irradiation

Mapping the Neutron beam fluctuations

0 100000 200000 300000 400000

0

1000000

2000000

3000000

4000000

5000000

Neu

tron

Flu

x

(cou

nts

)

Irradiation Time (sec)

En = 10.6 MeV

Neutron Flux vs Time

5 days of Irradiation

HPGe

Pb

Experimental DifficultiesHighly radioactive target,

Relatively long half life of 240Am (50.8 h)

Measurement of the 241Am(n,2n) cross section by

the activation method