Self-radiation damage in plutonium and uranium mixed dioxide

In plutonium compounds, self-radiation induces expansion of the lattice parameter as a function of time. The expansion of the lattice parameter and thermal recovery of radiation damage in plutonium and uranium mixed dioxide (MOX) were studied in this paper. The MOX powder had been kept in an ambient atmosphere for about two years. The lattice parameter of the powder saturated after an increase of about 0.23%. The change in the lattice parameter was formulated as a function of the self-radiation amount. Three thermal recovery stages of radiation damage were observed in temperature ranges below 400degC, 400-800degC and above 800degC. The recovery rate of the three stages in total lattice expansion was about 25%, 55% and 20%, respectively, and activation energy in each recovery was estimated to be 0.14 eV, 0.54 eV and 1.1 eV. (author)