The Necessity of Seismic Trigger Systems for Critical Facilities

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This paper deals with the operability of a nuclear power plant under a strong earthquake condition, and also with the necessity of a seismic trigger system for a NPP in relation to human operability under such a condition. There has been discussion on the necessity of a seismic trigger system for a NPP between the U.S. and Japan since the early 1960's. The author has been studying and surveying the operability of operators under seismic conditions by using a shaking table for the last several years. The result of testing indicates that the upper bound of the peak floor acceleration to maintain normal operability is 0.6〜0.7 G. The time sequential analysis of the TMI accident clearly shows that the operator should operate the plant several steps with some judgement for the first thirteen seconds, which is shorter than the duration of average ground shakings. These two facts may lead to the conclusion for the necessity of the seismic trigger system in principle. It is necessary to consider combining the seismic trigger signal and the confirmation signal of the starting-up of the emergency power supply to avoid complete power loss for core cooling. The author considers that the probability of the loss of all power supplies for the residual heat removal system under a destructive earthquake condition is not so low if the seismic trigger system and its logic are not adequately designed.
一般社団法人日本機械学会の論文
1990-09-15