Results of the 3rd regular inspection of Unit 4 in Fukushima No. 1 Nuclear Power Station

The 3rd regular inspection of Unit 4 in the Fukushima No.1 Nuclear Power Station in fiscal 1981 was carried out from September 22, 1981, to January 13, 1982. Inspection was made on the reactor proper, reactor cooling system, instrumentation-control system, waste management, reactor containment, etc. By visual, disassembling, leakage, functional, performance and other inspections, the results were as follows. (1) Pitting corrosion was detected on the weld line of the main shell in a liquid waste concentrator. (2) Leakage was suspected in one fuel assembly. Radiation exposure dose during the inspection was all below the permissible level. During the regular inspection, the following improvement works and others were done: new installation of radiation monitors in the reactor containment vessel, and the repair of the liquid waste concentrator. (Mori, K.)