Material Performance Metrics for Accident Tolerant Fuel Cladding in Pressurised Water Reactors

Research at Khalifa University in the U.A.E. is conducted to ultimately develop a selection methodology for accident tolerant fuel (ATF) claddings in pressurised water reactors. It is expected that such systematic approach would lead to the most suitable ATF cladding candidates that promote the longest possible coping times during severe accidents whilst also promote minimum penalties on the fuel cycles, operations, and economics of a nuclear power plant. The aim is to establish evaluation metrics on the cladding material performance under accident conditions to serve as selection criteria. This requires the identification and quantification of the cladding material properties that have a measurable effect on coping times. Thus, the paper reports the extent of influence individual thermophysical and thermochemical cladding properties have on plant responses in an unmitigated large break loss of coolant accident. A sensitivity study in Modular Severe Accident Analysis code was performed using hypothetical cladding materials. A lower bound cladding was created as a baseline for relative comparisons. Grounded on that, one thermophysical or thermochemical property was improved at a time to dissect the combinatory effect presented by existing materials. One result was that a cladding material with higher specific heat capacity (or enthalpy) absorbed a given amount of heat from the surrounding faster. It also stored this heat for longer before it was used to increase the cladding temperature. The rate at which the cladding temperature increased was also observed to be slower and therefore delayed the cladding melting. The work concludes that such numerical analysis presents a viable method to determine the degree of correlation between a cladding material property and coping time for the generation of appropriate evaluation metrics.