This project will advance the mechanistic understanding of fission gas behavior in UO2 nuclear fuel by developing a mesoscale fission gas simulator that takes advantage of leadership class computers. This will enable an accurate and physically based fission gas release model for application in integrated fuel performance codes. The model will be informed by results from large-scale atomistic and mesoscale simulations of the three stages of fission gas release, including diffusion and intra-granular bubble formation, bubble growth and coalescence on grain faces, and the transport of gas through interconnected grain edge tunnels to the fuel rod plenum. In order to address this complex problem, existing atomistic and mesoscale simulation tools will be further developed to take advantage of DOE high performance computing capabilities. The simulation tools will undergo rigorous uncertainty quantification and validation. In addition to gas release and retention, the integrated tool will predict their impact on performance parameters such as fuel swelling and thermal conductivity.
