Japan's Nuclear Regulatory Authority (NRA) today approved the operational safety programme submitted by Tokyo Electric Power Company (Tepco) for its seven-unit Kashiwazaki-Kariwa nuclear power plant. Tepco is working towards restarting units 6 and 7 at the site in Niigata prefecture. 

Tepco filed for safety assessments of Kashiwazaki-Kariwa units 6 and 7 in September 2013. It submitted information on safety upgrades - including its operational safety programme - across the site, and at those two reactor units. Kashiwazaki-Kariwa 6 and 7 - 1356 MWe Advanced Boiling Water Reactor units built in the late 1990s - were the first Japanese BWRs to be put forward for restart.

The NRA carries out reviews in parallel with checking the conformity of nuclear facilities with new regulatory requirements, changes in reactor installation, plan for construction works, and operational safety programmes.

Pre-service inspections are carried out at nuclear facilities after the approval, or the receipt of notification from the utilities, of their "plan for construction works".

Operational safety inspections check that nuclear facilities comply with the operational safety programme after its approval. These inspect the maintenance of reactor facilities, operation of power reactors and prevention of accidents involving nuclear fuel material, material contaminated by nuclear fuel material, or damaged power reactors.

Periodic operational safety inspections (four times per year) are then carried out to assess whether safety activities by nuclear operators are appropriate.

In October 2017, the NRA approved a draft report that concluded units 6 and 7 met the country's new safety standards. The document mandated a number of safety measures to be taken at the site. These include seismic reinforcements and construction of a seawall. It also lists measures to be taken to prevent a serious accident in the event of the loss of on-site power. Under the new safety requirements, BWRs must be equipped with filtered venting systems.

Earlier this month, the NRA approved Tepco's plan for implementing these additional safety upgrades at Kashiwazaki-Kariwa unit 7. It plans to complete work to reinforce the safety of the unit in December.

Kashiwazaki-Kariwa was unaffected by the March 2011 earthquake and tsunami, which damaged Tepco's Fukushima Daiichi plant, although the plant's reactors were previously all offline for two to three years following the 2007 Niigata-Chuetsu earthquake, which caused damage to the site but did not damage the reactors themselves. While the units were offline, work was carried out to improve the plant's earthquake resistance.

Although it has completed work at the other idled units at Kashiwazaki-Kariwa, Tepco is concentrating its resources on units 6 and 7 while it deals with the clean-up at Fukushima Daiichi. Restarting those two units - which have been offline for periodic inspections since March 2012 and August 2011, respectively - would increase the company's earnings by an estimated JPY100 billion (USD950 million) per year.

"We will continue to strive to further improve safety and reliability based on the lessons learned from the accident at the Fukushima Daiichi Nuclear Power Station," Tepco said today.

Researched and written by World Nuclear News