ORNL maintains a very broad portfolio of experimental research related to nuclear materials that includes a complementary modeling and simulation component. The MAMBA code provides surface chemistry modeling of crud on the surface of nuclear fuel rods. ORNL has built extensive experience using the BISON fuel performance code for a wide range of nuclear fuel performance assessments in commercial and research reactor fuels. This experience includes development and validation of material models, user support for simplification of modeling for standard LWR fuel, analysis of fuels for advanced reactors, including metallic fuels and TRISO coated particle fuel, and integration of fuel performance codes with reactor physics software.
Additionally, studies are being conducted at the mesoscale level to build an accurate and physically based fission gas release model for application in integrated fuel performance codes, as the fission gas models in standard fuel performance codes are a primary source of code uncertainty. Furthermore, the model development will be informed by results from massive atomistic and mesoscale simulations of the three stages of fission gas release: (1) diffusion and intra-granular bubble formation, (2) bubble growth and coalescence on grain faces, and (3) transport of gas through interconnected grain edge tunnels to free surfaces. The simulation tools will also undergo rigorous uncertainty quantification and validation against existing experimental data.
Another objective is the advanced use of integrated fuel performance codes to help design advanced reactors and their associated fuel systems for both DOE and private companies that want to partner with ORNL, to support and plan irradiation testing needed to qualify advanced fuels, and to support regulatory assessment of advanced fuels.