Accident tolerant fuels: A PRA comparison

Accident Tolerant Fuels (ATFs) are new nuclear fuels that have been developed in response to the accident at the Fukushima power station in March 2011. The goal of ATFs is to be able to withstand accident scenarios with better performances than the currently employed fuels (e.g., smaller hydrogen generation). This paper targets a method to evaluate and compare ATF performances from a Probabilistic Risk Assessment (PRA) perspective by employing a newly developed combination of Event-Trees and Dynamic PRA methods. Compared to Classical PRA methods (which are based on Event-Trees and Fault-Trees), Dynamic PRA can evaluate with higher resolution the safety impacts of timing/sequencing of events on the accident progression without the need to introduce overly conservative modeling assumptions and success criteria. In this paper we analyze the impact on the accident progression of three different fuel configurations for a Large Break Loss of Coolant Accident (LB-LOCA) scenario. The goal is to compare safety performances between ATF fuels (FeCrAl and Cr coated cladding) and the currently employed Zr based clad fuel. We show how Dynamic PRA methods con provide the analyst detailed and quantitative information on the safety impact of ATF from a PRA perspective.