The 1356 MWe Advanced Boiling Water Reactor (ABWR), which has been offline for almost 14 years, was restarted at 14:00 (local time) on Monday, Tokyo Electric Power Company (Tepco) said. Criticality – a state in which nuclear fission reactions occur continuously – was confirmed at 15:20.
Tepco said it plans to raise the pressure inside the reactor gradually after restarting it, and resume power generation and transmission on 16 February. It will then halt the reactor temporarily on 20 February or later to check for abnormalities, before conducting a final inspection and confirmation from the Nuclear Regulation Authority. The unit is scheduled to return to commercial operation on 18 March.
“We will continue to confirm the integrity of the plant equipment while actually using steam, and will respond diligently to the inspection by the Nuclear Regulation Authority,” Tepco said. “As this will be the first operation in approximately 14 years, we will carefully check the integrity of each piece of plant equipment, take appropriate action if we notice anything, and provide thorough information on the status of each startup process.”
The reactor was restarted in the evening of 21 January. However, shortly after midnight on 22 January, “an alarm was triggered in the control rod operation monitoring system for one control rod during the control rod withdrawal operation, causing the withdrawal operation to be suspended”. The unit’s restart was subsequently suspended while an investigation into the cause of the alarm was carried out.
Once the reactor re-enters commercial operation, it will be the first unit owned by Tepco to resume operation since the accident at its Fukushima Daiichi plant.
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Kashiwazaki-Kariwa (Image: Tepco)
The seven-unit Kashiwazaki-Kariwa plant was unaffected by the March 2011 earthquake and tsunami that damaged Tepco’s Fukushima Daiichi plant, although the plant’s reactors were previously all offline for up 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. All units have remained offline since the Fukushima Daiichi accident.
Although it has worked on the other units at the Kashiwazaki-Kariwa site, Tepco is concentrating its resources on units 6 and 7 while it deals with the clean-up at Fukushima Daiichi. These 1356 MWe ABWRs began commercial operation in 1996 and 1997, respectively, and were the first Japanese boiling water reactors to be put forward for restart. Tepco received permission from the Nuclear Regulation Authority to restart units 6 and 7 in December 2017. Restarting those two Kashiwazaki-Kariwa 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 (USD633 million) per year.
The governor of Japan’s Niigata Prefecture, Hideyo Hanazumi, gave his approval for the restart of Kashiwazaki-Kariwa units 6 and 7 in November last year, with the Prefectural Assembly backing his decision in December.
Tepco is prioritising restarting Kashiwazaki-Kariwa unit 6, where fuel loading was completed in June last year. The company has until September 2029 to implement anti-terrorism safety measures at unit 6. Kashiwazaki-Kariwa 6 would become the first reactor owned by Tepco to restart following the Fukushima Daiichi accident.
Prior to the March 2011 accident at the Fukushima Daiichi plant, Japan’s 54 reactors had provided around 30% of the country’s electricity. However, within 14 months of the accident, the country’s nuclear generation had been brought to a standstill pending regulatory change. Since then, 14 reactors have gradually resumed operation.
