Kansai Electric Power announced that it had confirmed a hole approximately 14 mm vertically and 4 mm horizontally in outdoor piping at Mihama Nuclear Power Station Unit 3. The hole is believed to have resulted from corrosion caused by rainwater entering because of an installation error when the cover was replaced in 2010. The reactor had been shut down on the 18th, and the timing of the restart of commercial operations remains undecided.
Kansai Electric Power announced that a hole had been found in an outdoor secondary-system pipe at Mihama Nuclear Power Station Unit 3 in Mihama, Fukui Prefecture. The hole measured approximately 14 mm vertically and 4 mm horizontally, and the reactor had been shut down on the 18th. No radiation leak has been reported at present, and the outlook for a restart remains undecided. Corrosion around the cover has also been observed.
Regarding the cause and sequence of events, the cover is reported to have been installed upside down relative to its intended orientation. The cover was replaced in 2010, and rainwater is believed to have entered through a gap, accelerating corrosion and causing the hole in the pipe. Kansai Electric is continuing its investigation based on this hypothesis.
At Mihama Unit 3, a hole also developed in a metal cap on the high-pressure turbine in May this year, and the reactor was manually shut down after a steam leak was confirmed. After measures including cap replacement, preparations for restart had been under way. Inspections and countermeasures to improve reliability are continuing in connection with the current incident.