SCOPING ANALYSIS OF LWR SHUTDOWN ACCIDENTS INITIATED BY EARTHQUAKES AND INTERNAL FIRES

THERE HAS RECENTLY BEEN HEIGHTENED CONCERN FOR THE POSSIBILITY THAT NUCLEAR POWER-PLANT ACCIDENTS DURING SHUTDOWNS COULD BE IMPORTANT CONTRIBUTORS TO THE OVERALL RISK PROFILE OF THESE PLANTS. THE 1986 SOVIET ACCIDENT AT CHERNOBYL WAS THE PRINCIPAL EVENT THAT LED TO THIS HEIGHTENED CONCERN, BUT A FEW RECENT EVENTS AT U.S. PLANTS HAVE ALSO CONTRIBUTED. TODAY, IT IS WIDELY UNDERSTOOD THAT THE RISK OF ACCIDENTS STARTING DURING SHUTDOWN CONDITIONS CANNOT BE IGNORED. TO ADDRESS THIS CONCERN, THE U.S. NUCLEAR REGULATORY COMMISSION WILL BE ACTIVELY STUDYING A VARIETY OF ISSUES IN THE NEXT FEW YEARS. THIS PROPOSED PROJECT, TO EXAMINE SHUTDOWN ACCIDENTS ARISING DUE TO EARTHQUAKES AND INTERNAL FIRES AS INITIATORS, WILL ADDRESS ONE PIECE OF THE OVERALL SHUTDOWN-ACCIDENT PICTURE. THE PROPOSED PROJECT, WHICH WILL USE TWO EXISTING NUCLEAR PLANTSAS CASE-STUDY EXAMPLES, WILL STUDY TECHNICAL SPECIFICATIONS,RELEVANT LICENSEE EVENT REPORTS, SHUTDOWN-CONFIGURATION STUDIES, THE FIRE INITIATOR DATA BASE DURING SHUTDOWNS, INFORMATION ABOUT AND WHICH EQUIPMENT MIGHT BE COMPRISED BYEARTHQUAKES DURING SHUTDOWN. THE PROJECT WILL PERFORM AN INTEGRATED EVALUATION OF THE INFORMATION ASSEMBLED, TO DEVELOP INSIGHTS INTO WHICH ASPECTS OF NUCLEAR POWER PLANT OPERATIONS COULD BE MOST SUSCEPTIBLE TO RISK-SIGNIFICANT ACCIDENTS FROM EARTHQUAKES AND INTERNAL FIRES. IF THE PROPOSED PROJECT IS SUCCESSFUL, SAFETY DECISION-MAKERS WILL HAVE MUCH BETTER INSIGHTS ABOUT SHUTDOWN-ACCIDENT RISKS ARISING FROM EARTHQUAKES AND INTERNAL FIRES. BECAUSE THE BROAD ISSUE OF SHUTDOWN- ACCIDENT RISK IS JUST NOW RECEIVING THE INCREASED ATTENTION THAT IT DESERVES, THE UNDERSTANDING OF RISKS FROM THESE TWO MAJOR "EXTERNAL INITIATORS" WILL ASSIST NRC AND INDUSTRY DECISION-MAKERS TO INVEST EFFORT MORE WISELY ON THE INTERLOCKING SET OF SAFETY ISSUES DURING SHUTDOWN. THIS COULD BE OF MAJOR IMPORTANCE IN THE COMING TWO OR THREE YEARS.