ANALYSIS OF LOSS OF OFFSITE POWER EVENTS 1987-2017

摘要

Loss of offsite power (LOOP) can have a major impacton a nuclear power plant’s ability to achieve andmaintain safe shutdown conditions. LOOP eventfrequencies and times required for subsequent restorationof offsite power are important inputs to plant probabilisticrisk assessments. This paper provides an overview of theU.S. Nuclear Regulatory Commission’s analysis of LOOPevents at U.S. commercial nuclear power plants, thenpresents the updated statistical and engineering analysisperformed by Idaho National Laboratory based on theoperating experience during calendar years 1987 through2017. Plant-level industry-average LOOP frequency anddurations were estimated for four LOOP categories:plant-centered, switchyard-centered, grid-related, andweather-related. Trending analysis conducted for themost recent decade (2008–2017) found no statisticallysignificant trends for critical operation LOOP frequency.However, statistically significant increasing trends inLOOP durations were identified for switchyard-centered,grid-related, and overall LOOPs. The paper provides areview of the multi-unit LOOP events and the potentialdependency issue. The paper presents engineeringanalysis of data to classify LOOP events by variouscauses such as equipment, human error, and weather inorder to provide additional qualitative insights.