Japan's most powerful nuclear plant shut down over safety flaws

Japan's nuclear regulator on Wednesday effectively banned Tokyo Electric Power Company Holdings Inc. from restarting its largest nuclear plant due to serious safety flaws, dealing a blow to the utility's efforts to turn its business around following the 2011 Fukushima nuclear disaster.

The Nuclear Regulation Authority formally issued the order not to transport nuclear fuel stored at the Kashiwazaki-Kariwa plant in Niigata Prefecture or loading it into reactors until corrective actions are taken to address the complex's security breaches.

TEPCO President Tomoaki Kobayakawa pledged to reshape the company's corporate mindset toward the security of nuclear materials as he attended a prefectural assembly session in Niigata to explain the problems, saying, "We have grave concerns about whether we can continue to operate the nuclear power generation business."

The company has seen restarting the seven-reactor Kashiwazaki-Kariwa complex, once one of the world's largest nuclear plants by output, as the main pillar of its business restructuring plan.

The plant was found to have been vulnerable to unauthorized entry at 15 locations since March last year because of defective intruder detection systems and backups. It is the first time the regulator has issued a corrective order for a commercial nuclear reactor.

The punitive measure is expected to remain for more than a year until the authority concludes additional inspections. Although the plant's Nos. 6-7 reactors cleared safety screenings by the regulator in 2017, and all seven reactors remain idle.

TEPCO has been facing substantial compensation payments and other costs stemming from the Fukushima disaster. It is aiming to restart the Kashiwazaki-Kariwa plant to reduce its dependence on costly coal-fired power generation.