Publications Details

Postclosure Transient Criticality Analysis for a Dual-Purpose Canister

Salazar, Alex

The postclosure criticality safety assessment for the direct disposal of dual-purpose canisters (DPCs) in a geologic repository includes considerations of transient criticality phenomena. The power pulse from a hypothetical transient criticality event in an unsaturated alluvial repository is evaluated for a DPC containing 37 spent pressurized water reactor (PWR) assemblies. The scenario assumes that the conditions for baseline criticality are achieved through flooding with groundwater and progressive failure of neutron absorbing media. A preliminary series of steady-state criticality calculations is conducted to characterize reactivity feedback due to absorber degradation, Doppler broadening, and thermal expansion. These feedback coefficients are used in an analysis with a reactor kinetics code to characterize the transient pulse given a positive reactivity insertion for a given length of time. The time-integrated behavior of the pulse can be used to model effects on the DPC and surrounding barriers in future studies and determine if transient criticality effects are consequential.