Comparative sintering behaviour of MOX powders synthesized through the freeze granulation or dry-cogrinding routes

Abstract

Two MOX powders containing 11 mol% Pu/(U+Pu) have been synthesized using the freeze granulation or dry-cogrinding routes. The sintering behaviour of green compacts has been investigated up to 1700 °C in an Ar/4.3 vol% H2 humidified with 1200 vpm H2O. The evolution of the sintering trajectory (grain size as a function of relative density) is identical up to approximately 94% relative density. Above this value, grain growth becomes significant in compacts made with the powder obtained by freeze granulation and densification becomes more modest. As for it, the sintering trajectory relating to the compacts shaped from the co-grinded powder continues up to approximately 97.5% relative density, without remarkable grain growth. Beyond this value, grain growth occurs and densification slows down. It has also been shown that the plutonium distribution is more homogeneous in the case of a sample sintered from the powder obtained by freeze-granulation (relative density around 97–99%).