Effect of molybdenum on the behaviour of caesium in uranium dioxide at high temperature

This study aims to evaluate the influence of a metallic fission product, molybdenum, on the behaviour of caesium in UO 2 at high temperature (1600 °C) under reducing atmosphere. Both elements were suc- cessively introduced by ion implantation (firstly Mo, then Cs) at room temperature at a fluence of 10 16 ions/cm ². We show that in these co-implanted samples, the defects created by the Mo implantation ren- der possible the nucleation of nanometric size bubbles during Cs implantation at room temperature. SIMS and TEM techniques were coupled in order to characterize the migration of both elements, as well as the UO 2 microstructure evolution after annealing at 1600 °C. We found that Mo is more mobile in presence of Cs, which may be related to an increase of available vacancies in the material produced by Cs im- plantation. On the contrary, the concentration profiles of Cs remain quite similar than when it is solely implanted, and its release percentage remain the same both in absence and presence of Mo. After an- nealing, both elements are found to be associated as Mo metallic precipitates and Cs bubbles distributed over the same depth (~150 nm). Comparing with the Cs bubbles distribution in absence of Mo, it is clear that the formation of Mo metallic precipitates hinders the Cs bubble migration. Our study highlights the role of dislocations on the nucleation of bubbles and metallic precipitates.

PANETIER Clementine;  SARRASIN Lola;  GAILLARD Clothilde;  PIPON Yves;  WISS Thierry;  BENEDETTI Alessandro;  DIESTE BLANCO Oliver;  MANGIN Denis;  DUCHER Roland;  DUBOURG Roland;  MONCOFFRE Nathalie; 

2021-01-15

ELSEVIER SCIENCE BV

JRC120941

0022-3115 (online),   

https://www.sciencedirect.com/science/article/pii/S0022311520312101?via%3Dihub,    https://publications.jrc.ec.europa.eu/repository/handle/JRC120941,   

10.1016/j.jnucmat.2020.152602 (online),