Fuel performance analysis of uranium silicide fuel for LWRs during cladding failure

Uranium silicide (U3Si2) has been proposed as an alternative to uranium dioxide (UO2) for use as light water reactor fuel, based on enhanced performance under normal operating conditions. U3Si2 possesses 17% greater heavy metal loading than UO2, enabling the fuel to reach longer refueling intervals using an equivalent fuel enrichment. It also possesses greater thermal conductivity, which reduces the radial temperature gradient across the fuel, potentially preventing the extensive thermally-induced cracking behavior observed in UO2 fuel. Upon cladding breach, however, the uranium silicide fuel can interact with the coolant, forming UO2, U3Si2H2 and H2 gas. This exoergic reaction causes a large increase in the fuel volume while also releasing additional reaction energy in the form of heat and producing hydrogen gas. This analysis uses the finite-element fuel performance code BISON to perform thermal-mechanical analysis of the U3Si2 fuel - Zircaloy cladding system under normal LWR operating conditions to assess the impact of cladding breach on fuel thermal and mechanical performance. This includes evaluating the stress development in the cladding and enthalpy release of the fuel during the fuel-coolant reaction.