Modelling of short-lived fission product release behaviour during annealing conditions

Abstract An analytical model has been developed to calculate the post-irradiation release of short-lived fission gases during high-temperature reactor accident conditions. The generalized treatment accounts for a time-dependent diffusivity, and is shown to reduce to the standard Booth diffusion model when the isotopic half-life is much longer than the anneal period. The present formalism is further extended to include the case where a steady-state fission product distribution has developed for the radioactive species in the fuel grain during an irradiation prior to the anneal. More tractable analytic formulas for analysis are also provided as short and long-time approximate solutions.