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Japan Regulator Delays Decision on Fault Under Ohi Plant

Japan delayed a decision on the future of the Ohi nuclear plant as seismologists under the Nuclear Regulation Authority conflicted over whether an earthquake fault line under the station is active or not.

Two reactors at the plant are the only ones running in the country. The other 48 are offline for safety checks following last year’s Fukushima nuclear disaster. Street protests this year in Tokyo have attracted tens of thousands of people calling for all the reactors to be shut.

The team of five studying the fault line met yesterday and will meet again on Nov. 7 to further discuss with plant operator Kansai Electric Power Co., said Kunihiko Shimazaki, a commissioner on the NRA, Japan’s newly formed nuclear regulator. At least one of the seismologists said the plant should be shut.

“My conclusion is an active fault exists under one of most important facilities of the Ohi nuclear plant,” said Mitsuhisa Watanabe, a tectonic geomorphology professor at Toyo University. The fault was overlooked due to Kansai Electric’s “irrelevant investigations” and the government’s “sloppy review,” Watanabe said.

Kansai Electric shares fell as much as 4.1 percent to 592 yen, heading for the biggest decline since Oct. 23 on the Tokyo Stock Exchange today. The stock has lost more than 70 percent of its value since March 10 last year, the day before the Fukushima disaster.

Rock Samples

Kansai Electric, which lost 117 billion yen ($1.5 billion) in the six months ended September due to rising fuel costs to make up for lost nuclear power generation, may have to shut and decommission all four reactors at the Ohi plant if the fault is active.

Three other members of the study group, including Atsumasa Okada, a Ritsumeikan University professor who specializes in active earthquake faults, said more investigation is needed to draw a conclusion. Watanabe responded that the Ohi reactors should be idled immediately for an exhaustive survey if the NRA team recommends additional investigation.

Shimazaki and the four seismologists visited the Ohi plant on Nov. 2 to examine soil and rock samples from boring, trenches and other geological work done by Kansai Electric. The geology of the area indicates existence of fault lines and when they were last active.

130,000 Years

Under Japan’s guidelines for nuclear plants, active faults are defined as those that have moved in the past 120,000 to 130,000 years, the NRA said Oct. 23 in a statement.

The fault line in question runs 900 meters from north to south between the No. 2 and No. 3 reactors of the Ohi plant. It may move together with active faults near the Ohi station and damage a water-intake channel, which is used to receive seawater to cool down reactors in the event of an emergency, Watanabe said in June.

“Unless we find definite evidence that shows it’s not an active fault by our on-site investigation, we cannot deny the possibility that it’s active,” Watanabe said in a statement submitted to the NRA before the team visited Ohi.

The Nuclear and Industrial Safety Agency, the NRA’s predecessor, ordered Kansai Electric to run additional checks on the fault line on June 18 after its advisory body said more data is needed to draw a conclusion.

Kansai Electric put out a report on Oct. 31, saying it has found no evidence to show the fault is active. The utility plans to submit its final report to the regulator by the end of December, it said.

Power Shortage

The NRA will approach the investigation of Ohi in black and white terms and the two Ohi reactors will be idled if the investigation team find it “black or even gray,” Chairman Shunichi Tanaka said Sept. 26.

Prime Minister Noda on Nov. 2 said the government will respect the decision to be made by the NRA on the Ohi plant, Kyodo News reported, citing an interview with the premier.

If Kansai Electric’s two 1,180-megawatt reactors are shut, electricity demand from companies and households supplied by the utility may exceed capacity by 9.1 percent this winter, Japan’s Chief Cabinet Secretary Osamu Fujimura said Nov. 2.

The utility supplies power to Osaka, Japan’s second-largest metropolitan region, as well as the cities of Kobe and Kyoto.

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