Countermeasures against the primary coolant leakage accident at No. 2 reactor in Takahama Nuclear Power Station of Kansai Electric Power Co. Incorporated

The accident of the Takahama No. 2 reactor (PWR, electrical output 826 MW) occurred on November 3, 1979. The cause was the deterioration of strength of the plug for the spare seat to mount the detector for measuring primary coolant temperature and resulted in breakage, due to the use of brass despite stainless steel should be employed as the plug material. The Minister of International Trade and Industry requested closer study of the cause of accident, confirmation of propriety of the modification and repair performed during the latest regular inspection, and overall checking-up for the quality assurance of the nuclear power station, to the Kansai Electric Power Co., and received the report on these points. In this report, the detailed follow-up of the cause is described and the propriety of works in the regular inspection is recognized. Since it is made clear that quality assurance activity was insufficient in the management of parts and the works for repair, the measures for improvement are proposed. The countermeasures directly connected to the accident include consolidation and completion of work planning documents and the check sheets for works and inspection. Also improvements in the systems for grasping circumstances, the investigation of causes, discussions for countermeasures, and the systems for communicating those informations in the company and to the organization outside the company when an accident or other anomaly occurs, are described. The flow charts of works proposed are attached. (J.P.N.)