A Japanese court found that Japan’s nuclear regulator’s decision to allow the Oi nuclear plant to restart was unreasonable and illegal. The issue involved the earthquake ground motion data for the nuclear plant.
The NRA had only considered Kansai Electric’s “average” estimates for ground motion in approving the restart of the company’s units 3 & 4 reactors at the Oi nuclear plant. The potential maximum ground movement was not part of the review and approval process. NRA’s own rules call for considering the “data dispersion” not just the average when considering earthquake resistance of a nuclear reactor.
This ruling has called into question all of the nuclear reactors in Japan that have received permission to restart. There are now questions about NRA’s entire review process that allowed this glaring flaw to proceed through their safety reviews. After the 2011 nuclear disaster Japan’s nuclear regulator, NISA, was disbanded over concerns the agency was too beholden to the industry they were supposed to regulate. NRA, the answer to the problems with NISA now seems to be plagued by the same sort of problems.
In 2014 NRA allowed the Sendai nuclear plant to continue to operate and store spent fuel in pools on site, ignoring the risks of a nearby active volcano.
Part of the post Fukushima safety upgrades required by NRA included the installation of “bunker buildings” at each nuclear plant. These buildings provide a fortified building for workers, with air handling and radiation shielding. In the case of the Fukushima disaster, the bunker building at Daiichi provided a safe refuge that allowed workers to stay on site to deal with the reactors. Without this building, workers would have abandoned Fukushima Daiichi due to deadly radiation levels at the height of the meltdowns. The outcome would have been much worse.
In 2014 the NRA allowed multiple nuclear plants to restart without these required bunker buildings. A deferral until 2016 was given after nuclear utility companies complained about the price tag. In 2019 these buildings had not been added to restarted nuclear power plants in Japan. A “deadline” of 2020 was announced by the NRA. In response, the three nuclear power utilities that have restarted reactors said they would need another 3-5 years to add bunker buildings to their nuclear plants.
The nuclear plant at the center of the lawsuit, the Oi aka: Ohi nuclear plant has had a controversial history. It was initially allowed to restart in 2012 then given full approval to continue operating units 3 and 4 at the plant in 2017. The 2012 restart resulted in a large protest at the remote nuclear plant site. Protesters blocked the narrow mountain road to the front gate of the plant. Workers were eventually brought in by boat to restart the reactors.
Oi has had plenty of technical controversy. In addition to the question of earthquake faults under the plant, our 2012 review found extensive problems with the design and siting of this nuclear plant that makes it a high risk for a serious accident. Our report on Oi can be found here.
Japan’s NRA was intended to restore public confidence in the “safety” of nuclear power. Any illusion of that has gradually eroded as NRA has proven rather toothless. The court ruling will likely be appealed to higher courts so it could potentially be overturned. If the ruling stands, all of the nuclear plants in Japan that have restarted or are preparing to do so, may be required to start over on their earthquake resistance reviews. This also has the potential to shut down any plants who fail a more stringent review.
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