Thermal Analysis of Metallic Fuel for Future FBRs

Aconceptual design of metallic fuelfor future Fast Breeder Reactors (FBRs) has been studied. The fuel consists of U-Pu binary alloy cladded in T91 alloy with Zr layer between the fuel slug and cladding material and helium gas in semicircular groove region. Temperature distribution of this fuel has been evaluated for different Linear Heat Rate (LHR) for two types of geometrywith the help of Finite Element Method (FEM). Contact element has been considered between fuel and clad. Contact pressure due to differential thermal expansion between fuel and clad has been evaluated by FEM. Input data required for gap conductance was obtained from various models available for gaseous and solid to solid conductance. Effect of contact pressure and thermal conductivity of gas on gap conduction has been studied. Based on detailed temperature distribution it was found that Limiting value of LHR is first reached by clad eutectic temperature between T91 and U-Pu than fuel centerline temperature based on solidus temperature of fuel.