Estimation of coping time in pressurized water reactors for near term accident tolerant fuel claddings

Abstract

Abstract The Fukushima Nuclear Power Plant (NPP) accident in Japan has motivated improving the safety of current light water reactors (LWRs). Accident tolerant fuels (ATF) are being developed to enhance the safety of LWRs by tolerating loss of active cooling in the core for a longer duration compared to standard UO2 and Zirconium-based cladding. In this work, the performances of the FeCrAl and Cr-coated ATF claddings under beyond design basis accidents (BDBAs) are modeled with thermal-hydraulics design basis code TRACE. Two models are used for high-temperature oxidation of FeCrAl: a model based on the experimental results of this work, and a model based on experimental results of ORNL’s work. A 3-loop Pressurized Water Reactor model is created and the following BDBAs are simulated for this study: large break loss of coolant accident without safety injection systems, short-term and long term station blackout (SBO) without any mitigation actions. In this work, we define coping time as the initiation time that assumed mitigation actions keep the clad temperature below its melting point. The results showed that ATF claddings increase the coping time and produce significantly less hydrogen compared to Zircaloy cladding under the considered BDBAs scenarios. However, the gains in coping times were found to be marginal.