Investigation of the Cs2(Mo,Te)O4 solid solution and implications on the Joint-Oxyde-Gaine system in Fast Neutron Reactors

Enrica Epifano (1) , A Volfi (2) , Maas Abbink (1) , H. Nieuwland (1) , L. van Eijck (1) , G. Wallez (3) , D. Banerjee (4) , Philippe Martin (5) , P.M. Martin , Anna Smith (1)

1 TU Delft - Delft University of Technology
2 POLIMI - Politecnico di Milano [Milan]
3 ENSCP - Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL
4 Department of Chemistry [Leuven]
5 DMRC - Département de recherche sur les procédés pour la mine et le recyclage du combustible

The formation of a thin layer, the so-called Joint-Oxyde-Gaine (JOG), between the (U,Pu)O2 fuel pellets and the cladding has been observed in fast neutron reactors, due to the accumulation of volatile fission products. Cs2MoO4 is known to be one of the major components of the JOG, but other elements are also present, in particular tellurium. In this work, an investigation of the structural and thermodynamic properties of Cs2TeO4 and Cs2Mo1-xTexO4 solid solution is reported for the first time. The existence of a complete solubility between Cs2MoO4 and Cs2TeO4 is demonstrated, combining X-ray diffraction (XRD), neutron diffraction (ND) and X-ray Absorption Spectroscopy (XAS). High-temperature XRD measurements were moreover performed on Cs2TeO4, which revealed the existence of a a-b phase transition around 713 K. Thermal expansion coefficients were also obtained from these data. Finally, phase equilibra points in the Cs2MoO4-Cs2TeO4 pseudo-binary phase diagram were collected using differential scanning calorimetry, and used to develop a thermodynamic model for this system using a regular solution formalism.

Domains: Inorganic chemistry

Enrica Epifano, A Volfi, Maas Abbink, H. Nieuwland, L. van Eijck, et al.. Investigation of the Cs2(Mo,Te)O4 solid solution and implications on the Joint-Oxyde-Gaine system in Fast Neutron Reactors. Inorganic Chemistry, 2020, 59, pp.10172−10184. ⟨10.1021/acs.inorgchem.0c01307⟩. ⟨cea-03552281⟩