Case study to examine the adequacy of symptom-oriented guidelines for pressurized water reactor nuclear power plants subject to a severe earthquake

Abstract

Abstract Recent probabilistic risk assessment studies indicate that potential accidents initiated by large earthquakes are among the major contributors to public risk from nuclear power plants. During a severe earthquake, the symptoms presented to operators may be unreliabl and may endanger the validity of actions in Emergency Response Guidelines (ERGs). The objective of the present study is to improve the operator capability of responding to seismic damage through the use of ERGs. The methods used are to deterministically identify possible weaknesses of ERGs, given a severe earthquake, and to probabilistically evaluate these identified weaknesses. Several cases are postulated. Each of them contains system failures with or without indicator failures and leads the core to meltdown conditions if the operator follows the ERGs strictly, without any deviation. The likelihood of each case is estimated. Seven cases are examined and some possible remedies for each case are discussed. The likelihood of most cases is estimated to be non-negligible. The identified indicator failures should be considered in future refinement of the ERGs.