CX-019265: Fuel Oxidation and Gas Release

The outer portion of high burnup nuclear fuel, i.e., fuel with an average rod burnup of >60 giga-watt-days/ton of uranium, can fragment into a powder during loss of coolant accident scenarios and can relocate or disperse throughout and out of the cladding. The mechanism of fragmentation needs to be understood and is thought to be a combination of pressurized fission gas on the grain boundaries and thermal stress release. The proposed action characterizes the retention of fission gas on the grain boundaries to improve the understanding of fuel fragmentation, relocation, and dispersal phenomena and allow improved accident modeling required by the Nuclear Regulatory Commission.