Low-temperature sintering of (U,Pu)O2 MOX in mild oxidative conditions

Abstract

We compare typical reductive sintering conditions for U, Pu mixed oxides (4 h at 1700 °C in Ar/6 % H2 + 1200 ppm H2O) with lower temperature and mildly oxidative conditions (2 h at 1200 °C in CO/CO2 = 1/9) and report on the resulting microstructures and homogeneity. We show that lower temperature and mildly oxidative conditions, without cover gas change, can give close-to stoichiometric, crack-free MOX pellets with a relative density of ∼ 95 %, and we propose ways to improve the homogenisations of PuO2 and UO2 and increase the grain size.