Further development of the fission gas swelling model for U-10Mo fuels

Abstract

The irradiation swelling of U-10Mo fuels is one of the critical factors to affect the in-pile structural integrity and dimensional stability of fuel plates. In this study, a mechanistic model of fission gas swelling for U-10Mo fuels is newly developed with a new evolution model of bubble density, considering the fission gas diffusion behavior and the grain recrystallization. The developed theoretical frame is validated by comparing the predictions in this study with diverse experimental data quantitatively and qualitatively, including the fission gas swelling, total irradiation swelling, the evolution rules of the bubble density and the bubble size, together with the thickness increments of fuel foil in a monolithic U-10Mo/Al fuel plates. The correlation of the irradiation creep with the fission-gas-swelling induced porosity for U-10Mo fuels is firstly considered in the simulation of irradiation-induced thermal-mechanical behaviors in Al-cladded monolithic fuel plates, and a new creep coefficient of dense U-10Mo fuels is identified as 180 × 10−22 mm3/MPa. The research results indicate that the developed fission gas swelling model has a satisfactory prediction ability, especially for higher burnup cases, and can describe the dominant dependences of external pressure and temperature found in the related experiments. In addition, parametric studies have been carried out to investigate the influences of temperature, external pressure and grain-boundary diffusion enhancement factor on the related fission gas behaviors.