Analysis of FeCrAl cladding performance under loss-of-coolant accident conditions

Abstract

Modeling developments and simulations of iron-chromium-aluminum (FeCrAl) cladding behavior under loss-of-coolant accident (LOCA) conditions have been performed using the BISON fuel performance code. First, we describe the modeling capabilities in BISON relevant to LOCA conditions, with an emphasis on new models added to the code in this work. The latter include updated models for FeCrAl cladding plasticity, burst failure and high-temperature oxidation. Subsequently, we describe BISON simulations of both FeCrAl and Zircaloy cladded fuel rods under the conditions of a postulated large-break LOCA (LB-LOCA) scenario in a BWR. The results indicate that the FeCrAl cladding will experience significantly lower ballooning, oxidation, and hydrogen production rates than Zircaloy cladding under the same conditions. However, the calculated burst time and temperature were similar for the Zircaloy and FeCrAl claddings. Finally, we perform extended simulations of fuel rod behavior for the conditions of a prolonged unmitigated LB-LOCA, including consideration of energy deposition due to the exothermic cladding oxidation reaction. The results point to a significantly reduced oxide thickness and hydrogen gas production for FeCrAl cladding compared to Zircaloy cladding.