BISON for Metallic Fuels Modelling

The fuel performance code BISON has recently been extended to simulate U-Zr and U-Pu-Zr metallic fuel rods irradiated in the US sodium cooled fast reactor EBR-II. By introducing fuel and clad specific material models, the backbone provided by the MOOSE/BISON software architecture has allowed rapid development of metallic fuel capabilities. Zirconium based fuels present unique challenges due to the different phases that exist at irradiation temperatures. Each phase possess differing thermo-mechanical properties, necessitating explicit tracking of the relative concentration of phases throughout the fuel rod in order to capture the integral behavior. In addition, the transition locations between phases change over the course of irradiation due to zirconium diffusion in the fuel, necessitating coupling of the thermo-mechanical simulation to the Fickian and Soret diffusion of Zr. Along with a robust U-Zr and U-Pu-Zr zirconium redistribution model, coupling of zirconium concentration to local power deposition allows for several coupled thermo-diffusion simulations to be compared based on different fabrication and operating conditions. Through the inclusion of flexible models into the BISON framework, core designers can utilize fuel performance simulations as an additional tool to support irradiation experiments and push for novel fuel designs. (author)