Derivation of analytical expressions for the network dislocation density, change in lattice parameter, and for the recrystallized grain size in nuclear fuels

At relatively high burn-up, both UO2 and U–10Mo nuclear fuels undergo irradiation-induced recrystallization wherein grains of micron size transform to grains of submicron size. Previously, expressions have been derived for the initiation, and for the progression of recrystallization as a function of fission density, fission rate, fuel temperature, and as-fabricated grain size. Here, analytical expressions are derived for the network dislocation density, change in lattice parameter, and the size of the recrystallized grains. The basic premise of the theory presented in this work is that irradiation-induced recrystallization is driven by the behavior of interstitial loops. It is demonstrated that these phenomena can be simulated in both UO2 and in U–xMo with the same theory, albeit with various property differences. Results of the calculations are compared with available data.