Fully Coupled Multiphysics Modeling of Burnup Dependent (U1-y, Puy)O2-x Fast Reactor Fuels Performance under Normal Operation and Reactor Transients

Description

Recycling of plutonium and minor actinides into a fast reactor has been found to be an effective way to manage the disposition of transuranic isotopes, such as plutonium, americium and neptunium, in the spent nuclear fuels. Plutonium and minor actinides have long half-lives and dominate the longterm radiotoxicity associated with releases from nuclear waste. Sodium-cooled fast reactor has become the leading candidate of three Generation IV fast reactor types, which meet the technological goals: sustainability, economics, safety, reliability and proliferation-resistance, to reduce the total radiotoxicity of nuclear waste, and dramatically reduce the waste's lifetime.The oxide fuel has been widely used in light water reactors and fast reactors due to its maturity and ease of fabrication. (U1-y, Puy)O2-x oxide fuels then become a very attractive candidate for Generation IV sodium-cooled fast reactors to transmute long life minor actinides, and to establish a fast breeder reactor (FBR) cycle with high potential of non-proliferation. Understanding the fast reactor fuels performance is a critical step in the fast reactor optimization. Fully coupled multiphysics modeling will provide a valuable tool for the design and optimization of sodium-cooled fast reactors.This proposed project of sodium cooled fast reactor (U1-y, Puy)O2-x oxide fuels performance modeling and simulation is to predict three dimensional (3D) dynamic burnup dependent behavior and failure modes of the fuel, cladding, and assembly structural components under normal operation and reactor transients, and perform sensitivity and uncertainty quantification to identify important macroscopic parameters of interest to modeling and simulation and improve the models of material properties and physical phenomena. The proposed project will conduct multiphysics modeling and simulations for (U1-y, Puy)O2-x mixed oxide fuels’ properties and performance under irradiation in sodium cooled fast reactor applications using self-defined PDEs based on the framework of COMSOL Multiphysics. Multiple time and length scale modeling and simulation will be conducted with physical phenomena fully coupled under steady state and transient conditions for fast reactor applications. Materials properties will include thermal physical, mechanical, chemical and phase diagrams for fuels, cladding and coolant, and multiphysics fuel performance includes thermal, mechanical, chemistry and restructuring, fission gas generation, diffusion, release and fuel swelling, grain growth, Fuel-Clad Mechanical Interaction (FCMI), fuel-Clad Chemical Interaction (FCCI) and creep fracture. Both the materials properties and physical phenomenon models will be dynamic burnup dependent to account for the burnup history and evolution. This proposed research also aims to determine material properties, for example, thermal expansion, specific heat, thermal conductivity and species diffusion coefficient, and key physical phenomena under atomic or molecular level, for example, fuel chemistry and restructuring, using molecular dynamics, in order to improve the models of material properties and physical phenomena. The MD-calculated fuel material properties and phenomenal results will be compared with the experimental data and empirical correlations available, and then used as an input for the multiphysics fuel performance code to predict the fuel performance in a fast reactor in order to increase the lifetime of the fuel, enhance the reactor efficiency, and reduce the amount of nuclear waste.The project involves advanced models and detailed analytical study of fuel material properties and fuel performance under normal operation and reactor transients. The project will not only benefit (U1- y, Puy)O2-x mixed oxide fuels performance prediction and understand multiple challenging physical phenomena under the radiation, corrosion and extreme high temperature environments, but also benefit other nuclear energy research, for example, advanced next generation nuclear reactor research and nuclear energy advanced modeling and simulation. The proposed research also impacts new fuel materials development and nuclear reactor design.