Photo/Illutration Japan Atomic Power Co.’s Tokai No. 2 nuclear power plant in Tokai, Ibaraki Prefecture (Hiroki Endo)

MITO--The Mito District Court on March 18 ordered the suspension of the aging Tokai No. 2 nuclear power plant, delivering a victory to a group of 224 plaintiffs who sought the injunction.

The court said preparedness to deal with a disaster is exceedingly inadequate, acknowledging a lack of well-conceived evacuation plans and a system to implement them. 

Lawyers representing the plaintiffs called the ruling "epoch-making."

The plaintiffs, who are residents of Ibaraki Prefecture and the Tokyo metropolitan area, filed a lawsuit in 2012 against Japan Atomic Power Co., which operates the single-reactor plant in Tokai, Ibaraki Prefecture.

One of the key contentions in the court battle was the appropriateness of the Japan Atomic Power’s basis seismic ground motion figure for the area around the plant.

The basis ground motion means earthquake ground motions having an intensity of the maximum scale among those possible at the site.

A nuclear power plant is constructed on the basis of this figure, which is also used to examine the safety of the plant.

After the 2011 Fukushima nuclear disaster, the government’s regulations on nuclear reactors were tightened in 2013 to oblige plant operators to factor in intensity higher than previously estimated when they set the basis seismic ground motion figure.

Japan Atomic Power calculated the figure based on data on past earthquakes that have occurred around the site.

In calculating the figure, the Nuclear Regulation Authority, the government’s nuclear watchdog, also calls on operators to consider higher potential force fluctuations.

The NRA says the basis earthquake ground motion determined by the existing calculation method is an “average” of figures made available from past data.

Japan Atomic Power defended its basis seismic ground motion figure as 50 percent higher than the average.

But plaintiffs countered that the figure should be four times as high as the current figure to ensure the safety of the plant.

Another point of contention was if Japan Atomic Power’s method of identifying a seismic fault likely to cause an earthquake was appropriate when it calculated the basis ground motion.

Japan Atomic Power said the method was created on the basis of accumulated data.

But the plaintiffs disputed that the method cannot re-enact the severe tremors caused by the magnitude-9.0 Great East Japan Earthquake in March 2011.

The court also heard whether the reactor that began operations in 1978 was fit enough to continue in service.

The NRA approved a 20-year extension of the 40-year legal lifespan of the Tokai No. 2 nuclear plant in November 2018.

But the plaintiffs said measures to safeguard cables and quake resistance of equipment and pipes were inadequate.

The Tokai No 2 plant has been offline after being damaged in the tsunami that followed the Great East Japan Earthquake. 

The operator is building a seawall against tsunami and other safeguards for the plant, a project expected to be completed in December 2022.

The Tokai No. 2 nuclear plant is the only commercial reactor situated in the Tokyo metropolitan area. Some 940,000 people reside within a 30-kilometer radius of the plant, the most of any nuclear power station in the nation.