Simulation of Fission Gas in Uranium Oxide Nuclear Fuel

Co-PI: Michael Tonks

Sponsor: Department of Energy

Start Date: September 15, 2017

End Date: September 14, 2022

Amount: $644,000

Abstract

This is the first jointly funded project by the DOE Office of Nuclear Energy and the DOE Scientific Discovery through Advanced Computing program. The objective is to significantly advance the mechanistic understanding of fission gas behavior and release in UO2 nuclear fuel by developing a mesoscale simulator that takes advantage of leadership class computers. An important aspect of our approach is to use the mesoscale insight gained via this tool 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, 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 free surfaces. The simulation tools will also undergo rigorous uncertainty quantification and validation against existing experimental data.

The UF portion of this project is focused on developing the massively parallel advanced simulator that consistently models the intra- and intergranular fission gas bubble evolution ultimately leading to fission gas release, in close collaboration with UTK. This will be accomplished by coupling the MARMOT tool (the Nuclear Energy Advanced Modeling and Simulation Programs mesoscale fuel performance tool, originally created by Tonks) to Xolotl (a spatially resolved cluster dynamics tool for modeling radiation and fission induced defects developed at UTK). The final tool will be used to carry out first of their kind, massive 3D simulations that capture all critical elements of fission gas release in 3D uranium dioxide polycrystals.