Loss of Offsite Power Recovery Modeling in United States Nuclear Power Plants

Abstract

ABSTRACTLoss of offsite power (LOOP) can have a major, adverse impact on a nuclear power plant's (NPP) ability to achieve and maintain safe shutdown conditions. The time required for subsequent restoration of offsite power after a LOOP event occurred and the probabilities of LOOP events exceeding various durations (or LOOP non‐recovery probabilities) are important inputs to NPP probabilistic risk assessments (PRA). This paper reviews the analysis of LOOP events at United States commercial NPPs conducted by Idaho National Laboratory (INL) for the US Nuclear Regulatory Commission (NRC). This paper presents the current LOOP recovery modeling that estimates probabilities of LOOP events exceeding various durations (or LOOP non‐recovery probabilities) based on operating experience. NPPs use these LOOP results in PRA models for various risk‐informed activities. Finally, this paper provides the LOOP non‐recovery probability results for the four LOOP categories: plant‐centered, switchyard‐centered, grid‐related, and weather‐related with LOOP recovery data from 1988 to 2018.