Onagawa 2 restart expected in September

20 February 2024

Tohoku Electric Power Company now expects to reconnect unit 2 of its Onagawa nuclear power plant in Japan's northeastern Miyagi Prefecture to the grid in September. In January, the utility said additional safety construction works had delayed the previously planned restart in May.

Tokohu's Onagawa plant (Image: Kurihalant Co Ltd)

Tohoku said in January that work to fireproof electric cables at the unit was taking longer than planned and it anticipated a delay of several months regarding the completion date of the safety measures.

"As a result of the completion of a thorough investigation including securing the necessary materials and equipment and workers for the construction work, as well as workability on site, the completion date of the safety measures work at Onagawa Nuclear Power Station Unit 2 has been changed from the previous date of February 2024 to June 2024," Tohoku has now said.

"In addition, the timing of 'restarting', when the generators will be connected in parallel to start generating power, is expected to be around September 2024." It added: "Our company will continue to make every effort to complete the construction work, with safety as our top priority."

Tohoku applied to the Nuclear Regulation Authority (NRA) in December 2013 for a safety assessment of Onagawa 2 - a 796 MWe boiling water reactor (BWR) - to verify countermeasures applied at the plant meet new safety standards. In late November 2019, the NRA approved a draft screening document that concluded the upgraded plant will meet revised safety standards, introduced in January 2013. In February 2020, the NRA approved the final screening report, clearing the way for the unit to resume operation. Tohoku is required to complete the countermeasure upgrades and obtain the approval of local authorities before it will be able to restart Onagawa 2.

The Onagawa plant was the closest nuclear power plant to the epicentre of the earthquake and tsunami of 11 March 2011, but sustained far less damage than expected. The earthquake knocked out four of the plant's five external power lines, but the remaining line provided sufficient power for its three BWRs to be brought to cold shutdown. Onagawa 1 briefly suffered a fire in the non-nuclear turbine building. The plant was largely unaffected by the tsunami as it sits on an elevated embankment more than 14 metres above sea level, but the basement floors of unit 2 were flooded.

Researched and written by World Nuclear News