Japan Atomic Power Company (JAPC) has applied to the Japanese regulator for pre-use inspections of unit 2 at its Tokai nuclear power plant in Ibaraki prefecture. These inspections mark the final regulatory stage in the restart procedure for the country's reactors.

Unit 2 of the Tokai plant (Image: NRA)

Under Japan's reactor restart process, plant operators are required to apply to the Nuclear Regulation Authority (NRA) for: permission to make changes to the reactor installation; approval of its construction plan to strengthen the plant; and, final safety inspections to ensure the unit meets new safety requirements. Operators are required to add certain safety-enhancing equipment within five years of receiving the NRA's approval of a reactor engineering work programme.

JAPC applied to the NRA in May 2014 to restart Tokai 2. The 1060 MWe boiling water reactor automatically shut down and lost external power during the 11 March 2011 earthquake that led to the accident at the Fukushima Daiichi plant. One of Tokai 2's three emergency generators was damaged by a 5.4 meter tsunami, but the plant was still able to safely enter cold shutdown. The reactor has remained idle since then. The NRA approved the restart of Tokai 2 in September 2018 after concluding that safety measures submitted by JAPC passed revised safety standards.

The utility announced on 17 April it had applied for pre-service inspections of the unit. These inspections are to confirm that the safety countermeasure equipment complies with the approved construction plan at the plant. JAPC expects all these inspections to be completed by December 2022, after which the reactor can resume commercial operation.

Construction work on safety countermeasures - including a 1.7km-long sea wall to protect the plant from a potential tsunami as high as 17.1 meters - was scheduled to be completed in March 2021. However, in January JAPC announced that construction was taking longer than originally expected and completion has been rescheduled for December 2022.

JAPC applied to the NRA in November 2017 to extend the operation of the unit, which started commercial operation in 1978, by 20 years. The utility received regulatory approval a year later. Under Japan's revised regulations, reactors have a nominal lifespan of 40 years. However, extensions can be granted once only and limited to a maximum of 20 years, contingent on exacting safety requirements.

After completing all construction work related to the extended operation of the unit, JAPC will still need the approval of local municipalities in Ibaraki prefecture prior to the resumption of operation of Tokai 2.

JAPC has been decommissioning Tokai unit 1 since December 2001. The 166 MWe gas-cooled reactor - which operated between 1966 and 1998 - was Japan's first commercial power reactor.

Researched and written by World Nuclear News