Tohoku Electric Power Company has begun loading fuel assemblies into the reactor at unit 2 at its Onagawa NPP in Japan’s Miyagi Prefecture. The reactor has been offline since November 2010 and will become Japan’s 13th reactor and first boiling water reactor (BWR) to be restarted since all NPPs were closed down in the wake of the 2011 Fukushima Daiichi accident.
Tohoku applied to the Nuclear Regulation Authority (NRA) in December 2013 for a safety assessment of the 796 MWe Onagawa 2 to ensure the reactor complied with the more stringent safety standards introduced after Fukushima. In November 2019, NRA approved a draft screening document stating that the plant would meet the revised safety standards following upgrades. In February 2020, NRA approved the final screening report, clearing the way for the unit to restart after more than a decade of construction work to secure safety.
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 earthquake caused the ground to sink by a metre and the basement floors of unit 2 were flooded. The reactor coolant pumps were broken and more than 1,000 cracks were found in the unit 2 reactor building.
To meet NRA safety standards, Tohoku Electric increased the size of the sea wall at the plant to at least 29 metres in height and 800 metres in length. It also reinforced the plant to ensure it could withstand major earthquakes. The total estimated cost of the safety measures, including planned anti-terrorism facilities for the plant, is JPY710bn ($4.5bn).
Tohoku started fuel loading at Onagawa 2 on 3 September. “We will continue to prioritise safety and thoroughly address each and every process, while also carefully communicating our efforts to local residents, as we work hard to restart operations,” the company said. In July, Tohoku revised the timing of fuel loading from July to September and now expects to begin operation in November.
