Thermochemical effect of fission products on sodium - MOX fuel reaction: The case of niobium

The influence of niobium on the sodium MOX fuel chemical interaction was studied by different heat treatments of airtight capsules containing fresh MOX, sodium and a niobium strip. The characterisation results evidenced a two-step process with first MOX oxidation and then MOX reduction. This result was interpreted by considering the formation of sodium niobiate that captures oxygen from the MOX. This interpretation is used to discuss the influence of niobium as fission product on the sodium -irradiated MOX fuel reaction.