Unit 2 of Tohoku Electric Power Company’s Onagawa NPP in Japan’s Miyagi Prefecture has been shut down due to equipment problems less than a week since it restarted. The 825 MWe boiling water reactor (BWR) had been offline since November 2010. It was Japan’s 13th reactor and first BWR to be restarted since all NPPs were closed down in the wake of the 2011 Fukushima Daiichi accident.
Tohoku Electric said the radiation situation at the plant located in Onagawa town and Ishinomaki city remained normal. According to the company, equipment was inserted into the reactor that to check if a detector that measures neutrons was operating normally. However, the inserted equipment stopped working in the middle of the process and was manually pulled out and recovered.
Tohoku Electric said it will postpone power generation until the cause of the problem is determined. Tohoku had initially planned to start power generation on 7 November but since inspections and other processes went smoothly, the schedule had been moved to 3 November. Commercial operation had been expected to begin in late December. Tohoku has yet to announce a revised date.
The Onagawa plant was the closest NPP to the epicentre of the earthquake and tsunami in March 2011 but avoided the core meltdowns that occurred at Fukushima. Although earthquake destroyed four of the plant’s five external power lines, the remaining line provided sufficient power for the three BWRs to be brought to cold shutdown. The plant was relatively unaffected by the tsunami as it is built on an elevated embankment more than 14 metres above sea level. However, the basement floors of unit 2 were flooded. Tohoku Electric has since decided to decommission unit 1 and is now in the process of seeking clearance to restart unit 3.
