EVALUATION OF ACCIDENT INITIATED BY REACTIVITY INSERTION IN PWR

Abstract

Reactivity Initiated Accident (RIA) induced by control rod ejection is a design basis accident for Pressurized Water Reactors and the regulatory authority requires that the accident should be analyzed for nuclear reactors. The safety performance of The Westinghouse GenIII+ reactor AP1000 is investigated at steady state and during RIA using different fuels. In the study, two alternative core loading patterns is proposed in which 30% of the UO2 fuel assemblies is replaced with (U-Pu)O2 fuel in one of the patterns and (Th-Pu)O2 fuel in the other. The steady state analysis illustrate that UO2/MOX and UO2/(Th-Pu)O2 core loading patterns can be utilized as the safety criteria mentioned in Design Control Document are met. RIA analysis show that no fuel failure occurs under transient. The overall performance of UO2/MOX and UO2/(Th-Pu)O2 core loading patterns have proved to be similar to that of UO2 core loading. The safety limits are not violated for the control rod ejection accident which points the safety of AP1000 in the case of the transient.