I MMOBILIZATION OF RADIOACTIVE IODINE IN PHOSPHATE GLASS T. Lemesle 1,2, F.O. Méar 1, L. Campayo 2, O. Pinet 2, L. Montagne 1 1 Unité de Catalyse et Chimie du Solide - UMR-CNRS Université Lille Nord de France, F Villeneuve d’Ascq, France 2 DEN/DTCD/SECM/LDMC, CEA Marcoule, BP 17171, Bagnols sur Cèze, France Tg variation as a function of the formulation Unité de Catalyse et de Chimie du Solide - UMR CNRS 8181 USTL - Bâtiment C Villeneuve d’Ascq Cedex - France -  +33 (0) Many thanks to all the following organizations for their kind contribution to this work References : [1] CAMPAYO ET AL., PROJET MATINEX[4] KAWAMURA ET AL., SOLID STATE IONICS, 2002 [2] DARAB ET AL., MRS, 1999[5] VAN WÜLLEN ET AL., SOLID STATE SCIENCES, 2005 [3] MINAMI ET AL., J. ELECTROCHEM. SOC., 1977 Glass system: Ag 2 O – (1-x) P 2 O 5 - Al 2 O 3 – x B 2 O 3 – AgI  Variations :  Ag/P rate  O/P rate  Iodine rate  Substitutions :  Al 2 O 3 for P 2 O 5 and Ag 2 O  B 2 O 3 for P 2 O 5 Density variation as a function of the formulation Structural variations as a function of the formulation  A linear increase in density is observed.  Addition of AgI increases density whatever the glasses; however, the increase is more important in phosphate glasses than in boro- phosphate glasses.  An increase in the AgI amount leads to a decrease of T g.  For AgI-bearing glasses, impact on the T g is more important for glasses with boron substituted for a small amount of phosphate and having a low Ag/P ratio.  No more T g variations are observed even with modified Ag/P ratios at nearly 1% of iodine content by volume.  Addition of Al 2 O 3 moves the chemical shift to the left with a higher fraction of Q n-1 units (shorter phosphate chain than Q n ).  Even with Al 2 O 3, addition of AgI moves the spectra to the right. Al(PO 3 ) 3 [A]AlPO 4  T g increases with the addition of alumina  Addition of Al 2 O 3 in AgI glasses having high Ag/P ratios is found to be more efficient  Substitution of P 2 O 5 by B 2 O 3 and then addition of Al 2 O 3 cause a high increase of T g  Increase in Ag/P decreases T g  Al 2 O 3 substitution for P 2 O 5 has no significant effect on T g  High density for silver phosphate glasses  Al 2 O 3 substituted for P 2 O 5 has more effect on the density than B 2 O 3 substituted for P 2 O 5.  An increase in the Ag/P ratio increases glass density.  Impact on density with the addition of Al 2 O 3 is crucial on glasses having a high Ag/P.  With the incorporation of higher AgI amounts, broad peaks become narrower. Broad peaks correspond to different sites for silver cations [4].  The addition of Al 2 O 3 changes the chemical shift values. It is explained by the increase in bond length of Ag-O [5]. Al(PO 3 ) 3 [A]  Lower tendencies to the crystallisation by addition of AgI in silver aluminophosphate glasses with substitution of B 2 O 3 for P 2 O 5  With AgI, aluminum changes from Al(6) to Al(5) plus Al(6) Al 2 O 3 Ag 2 O P 2 O 5 AgPO 3 + x Al 2 O 3 Ag 5 P 3 O 10 + x Al 2 O 3 Ag 4 P 2 O 7 + x Al 2 O 3 Ag 3 PO 4 7% :Al 2 O 3 incorporationlimit Conclusion In this study, B 2 O 3 and Al 2 O 3 were added and/or substituted for phosphate in iodine-bearing glasses. This was done to find a phosphate glass having a high iodine content, an intermediate Tg (> 180 °C) and no crystallisations. The results suggest that to meet the above-mentioned criteria, the glass has to have less than 5% of Al 2 O 3 and a low Ag/P ratio. The formulation can even be improved by substituting B 2 O 3 for P 2 O 5. Finally, the finding suggest that the thermal and structural properties of glasses are highly influenced by the incorporation of AgI and this change will be deeply studied in further investigations. Variation of T g as a function of iodine content Variation of Tg as a function of the O/P ratio in the glass system Ag 2 O – (1-x) P 2 O 5 - Al 2 O 3 – x B 2 O 3 – AgI ° Variation of density as a function of the O/P ratio in the glass system Ag 2 O – (1-x) P 2 O 5 - Al 2 O 3 – x B 2 O 3 – AgI ° Variation of density as a function of iodine Influence of the incorporation of AgI on the structure as a function of Ag/P by 31 P NMR  Addition of AgI for different ratios of Ag/P changes the chemical shift. The chemical shift is shifted towards the highest Q n. Influence of the incorporation of Al 2 O 3 and AgI on the structure by 31 P and 27 Al NMR Al(PO 3 ) 3 [A]AlPO 4  Without AgI, aluminum is in an octahedral form, Al(6), except for Ag/P < 2.  With addition of AgI, for Ag/P >1, aluminium exhibits two environments: Al(5) and Al(6), respectively.  Crystallisation of aluminum occurs in AgI-AgPO3-5Al: narrow peaks for Al(PO 3 ) 3 and AlPO 4. Influence of the incorporation of AgI and substitution in silver metaphosphate glasses by 109 Ag, 31 P and 27 Al NMR  Substitution of B 2 O 3 for P 2 O 5 has an effect (chemical shift moved to the left) even with 5%mol Al(PO 3 ) 3 [A] P-O-Al zone P-O-B zone Analysis of incorporation of AgI and Al 2 O 3 by 109 Ag NMR Analysis of substitution of B 2 O 3 for P 2 O 5 by 31 P and 27 Al NMR ratio amount Iodine-129, extracted during the reprocessing of spent nuclear fuel, is considered as a long-lived isotope (half-life: 15.7 million years). It is characterized by a high mobility in geologic environment as well as by its strong tendency to volatilization. Its management within the framework of a safe disposal in a deep geological repository requires the definition of a conditioning matrix. Two main types of conditioning matrices, mentioned in the available literature, seem particularly interesting: the ceramic matrices belonging to the system of lead-bearing vanadates [1 ] and the glassy matrices like borosilicate glasses [2] or phosphate glasses [3]. It is on the latter system that this PhD work is focused ( 127 I is used as an analogue for 129 I).