Japan’s Tohoku Electric Power said on 27 November that it has received regulatory approval to restart unit 2 at its Onagawa nuclear plant in Miyagi Prefecture, subject to a public consultation period.
Onagawa was the closest nuclear plants to the epicenter of the March 2011 earthquake, which triggered a tsunami that destroyed the Fukushima Daiichi nuclear plant. An international mission to the station in August 2012 found it was remarkably undamaged by the event.
Although Onagawa 2 was flooded by the tsunami, losing up to 70% of its earthquake-resistance strength, its cooling system remained intact. The earthquake destroyed four of the plant’s five external power lines, but the remaining line provided sufficient power to bring all three boiling water reactors to a cold shutdown. Onagawa 1 briefly suffered a fire in the non-nuclear turbine building. Onagawa was largely unaffected by the tsunami as it sits on an elevated embankment some 14m above sea level, but the basement floors of unit 2 were flooded.
Further approvals will be required before the reactor can restart, along with the consent of local authorities, which is not guaranteed. Tohoku Electric expects to spend JPY340 billion ($3.1 billion) on safety upgrades at Onagawa, including for a wall stretching 800m in length and standing up to 29m above sea level to protect it from tsunamis. Work is expected to be completed by March 2021.
Following the Fukushima disaster Japan closed all 54 of its reactors. Nine have been restarted so far, all of them pressurised water reactors. Restarting Onagawa 2 will save JPY35 billion a year in fuel costs.
Tohuko applied to the Nuclear Regulation Authority (NRA) in 2013 for a safety assessment to verify countermeasures taken at the plant met new safety standards introduced in January 2013. Tohoku intends to decommission Onagawa 1, but has yet to decide on whether to apply for the restart of Onagawa 3.
Photo: Onagawa Nuclear Power Plan taken by Nekosuki600(talk / Contributions) in November 16th 2003 and uploaded by Nekosuki600(talk / Contributions) to Japanese Wikipedia in September 25th 2005