Nuclear waste treatment by vitrification

• Transformation of highly radioactive liquid waste into solid waste• An atomic scale incorporation of radionucleides (RN)• Production of glass canisters at La Hague reprocessing plant• Laboratory scale R&D at CEA Marcoule• Ceramics for specific wastes still under research

Multi-scale glass characterization methodology :

• XRD, SEM images for glass homogeneity• Thermal analysis, viscosity, oxygen pressure, thermal and electrical conductivity• Alteration rate by water

Context

Glass structure determination

Ceramic structure determination

Goal :

• Determining the structure of simplified glass• Growing the complexity of the glass • Looking at structure deviation when crystallizations occur• Modelization of the structure

Facilities :

• X’Pert MPD Pro with Mo tube reflection geometry• TsiganX software analysis

Atomic conditioning of RN into glass structure

Pair function distribution of BaCa(CO3)2 barytocalcite

For 14C conditioning

Nicolas Massoni, Olivier Bouty

CEA Marcoule, DEN/DTCD/SECM, BP 17171, 30207 Bagnols sur cèze Cedex

Total scattering analyses of glass and ceramics in the context of nuclear waste containment

In France, spent nuclear fuel is reprocessed to separate final wastes from uranium and plutonium oxide. Fission products are extracted and conditioned into glass recognized for its good long term behavior. Iodine 129I or carbon 14C are also long-lived radionucleides coming from spent fuel reprocessing but they are not contained in the nuclear glass. At present, research is performed for iodine and carbon which could be immobilized into ceramics, respectively apatite [1] or barytocalcite [2]. These ceramics and simplified glass were synthesized by modification of the usual precursors. They show a slight deviation from the pristine materials requiring a deeper understanding of their structures. Thus total scattering analysis has been successfully employed with a lab diffractometer equipped with a Mo source. About ceramics, a modified apatite using a new precursor has been synthesized and the PDF determined using PedfGetX2 [3]. The comparison of the PDF between pristine and modified apatite clearly shows a modification of the interatomic distances. Modelling of the structure was performed with PDFgui [4]. A barytocalcite sample has been also analyzed. It allows us to check that no local deviation from average density was present but also successful modelling allows us to get more precise atomic coordinates. Concerning glass, two simplified glass ‘SiLiO’ and ‘SiBaO’ have been synthesized and the PDF determined using TsiganX [5]. It shows well-known silicate pairs and also new pairs which should be attributed by literature values or adequate modelling.

Abstract

[1] - C. Guy et al., CR. Phys. 3, 827, (2002).

[2] - A. Grandjean et al., J. of Nuc. Mat. 345, 11, (2005).

[3] - Qiu, X. and Thompson, J. W. and Billinge, S. J. L. J. Appl. Crystal. 37, 678, (2004).

[4] - C. L. Farrow, P. Juhás, J. W. Liu, D. Bryndin, E. S. Božin, J. Bloch, Th. Proffen and S. J. L. Billinge, J. Phys.: Condens. Matter, 19, 335219, (2007).

[5] - http://www-tsiganx.cea.fr/

Goal :

• Looking at structure deviation when substitution occur• Modelization of the structure

Facilities :

• X’Pert MPD Pro with Mo tube reflection geometry• PDFGetX2 and PDFgui softwares

BAR11-24 P21/m

-4

-3

-2

-1

0

1

2

3

4

5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

r (Å)

G(r

)

Exp

Calc

Diff-3

-2

-1

0

1

2

3

4

5

1 1,25 1,5 1,75 2 2,25 2,5 2,75 3 3,25 3,5 3,75 4 4,25 4,5 4,75 5

Distance interatomique (Å)

Apatite HA-Ca

Apatite HA-CaI

P-O 1,55 ÅP-O 1,60 Å

1,28 Å ?

Ca-O 2,46 Å

2,84 ÅO-O (Iodate)

Pair function distribution of two apatites:Ca10(PO4)6I2 apatite “Ha-Ca”

Ca10(PO4)6(IO3)2 apatite “HA-CaI”For 129C conditioning

r

→ No deviation at short distances

→ New peak at 1.28Å appears for IO3-apatite

Outlook :

• Modelization of the structure• Proposal for high energy WAXS at ESRF

Me10(XO4)6Y2 apatite structure

Na

O

SiAl

B

Zr

→ Importance of the glass structure

Glass elaboration facilities

Simplified glass « CJ1 » : (SiO2)0,67 (Na2O)0,14 (B2O3)0,18

www-tsiganx.cea.fr

Outlook :

• Modelization of the structure for pairs matching• 4 and more oxides incorporation

Gaussian functions superposition

SiO2, B2O3, X2O with X= Li, Na, K, CsSiO2, B2O3, Na2O, Eu2O3

SiO2, B2O3, Na2O, Al2O3, CaOSiO2, Li2O (+MoO3)SiO2, BaO (+La2O3)SiO2, Na2O (+CaO)

Glass analyzed

Oven

Nuclear glass

PDF of other glass

Atomic pair density function of CJ1