Abstract

ABSTRACT Additive MOX pellets are fabricated by mechanically blending the additive material powder and MOX powder. Nd2O3 and Sm2O3 are chosen as the additive materials to simulate the corresponding soluble fission products dispersed in MOX. Shrinkage curves of the MOX pellets are obtained by dilatometry, which reveal that the sintering temperature is shifted toward a value higher than that of the respective regular MOX. The additives, however, promote grain growth and densification, which can be explained by the effect of oxidized uranium cations to a pentavalent state. Ceramography reveals large agglomerates after sintering, and Electron Probe Micro-Analysis confirms that inhomogeneous elemental distribution, whereas XRD reveals a single face-centered cubic phase except for Sm-doped specimens indicating a small peak of Sm2O3. Finally, by grinding and re-sintering the Nd2O3-doped MOX, the cation distribution homogeneity is significantly improved, which can simulate spent nuclear fuels with soluble fission products.

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