Tokai 2 passes safety screening

04 July 2018

Unit 2 of Japan Atomic Power Company's (JAPC's) Tokai nuclear power plant has moved a step closer to restarting after the country's nuclear regulator said the unit meets revised safety standards. Having started commercial operation in 1978, it is one of the oldest of Japan's reactors to have applied for restart.

Tokai 2 - 400 (NRA)
Tokai 2 (Image: NRA)

JAPC applied to the Nuclear Regulation Authority (NRA) in May 2014 to restart the 1060 MWe boiling water reactor in Japan's Ibaraki prefecture. The unit 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 assessment by the NRA that the reactor, and the plant as a whole, is safe for operation represents by far the major part of the licensing process.

Under Japan's reactor restart process, plant operators are required to apply to the 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.

Court rejects suspension of Ohi units

The Kanazawa Branch of the Nagoya High Court has overturned a May 2014 ruling by the Fukui District Court that Kansai should suspend operation of units 3 and 4 of its Ohi plant.

The Fukui District Court had ruled in favour of a lawsuit filed by a group of almost 200 local residents who claimed that the Ohi plant is sited near several active seismic faults and is not adequately protected against earthquakes. Kansai, they claimed, underestimated the maximum magnitude of earthquake that the units could face. The court issued an injunction against Kansai restarting Ohi units 3 and 4. However, the units resumed operation in March and May, respectively after the NRA approved their restart.

Under the 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. So far, three pressurised water reactors have been approved for extended operation under the revised regulations. These are Takahama units 1 and 2 and Mihama 3, all owned and operated by Kansai Electric Power Company.

To extend the operating life of Tokai 2, JAPC must receive NRA approval by November - the mandatory deadline - on three outstanding issues: safety measures, detailed designs and extension of operations. The company applied to the NRA in November 2017 to extend the operation of the reactor by 20 years.

JAPC predicts a potential tsunami as high as 17.1 metres at the Tokai 2 site, according to the Kyodo news agency. The company expects investment of about JPY180 billion (USD1.6 billion) is needed to put additional safety measures in place at the plant.

The plant is unlikely to be restarted before March 2021 when construction work to bolster safety measures is scheduled to be completed. The approval of local municipalities is also required prior to its resumption of operation.

JAPC has already decided to decommission Tokai unit 1 and unit 1 of its Tsuruga plant in Fukui prefecture. Meanwhile, the restart of Tsuruga 2 has been thrown into doubt after the NRA accepted a report compiled by a panel of experts that concluded the unit sits upon an active fault line. However, JAPC has said it still plans to apply for safety checks in order to restart it.

So far, nine of Japan's 39 operable reactors have cleared inspections confirming they meet the new regulatory safety standards and have resumed operation. These are: Kyushu's Sendai units 1 and 2 and Genkai units 3 and 4; Shikoku's Ikata unit 3; and Kansai's Takahama units 3 and 4 and Ohi units 3 and 4. Another 16 reactors have applied to restart.

Researched and written
by World Nuclear News