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2013年8月25日 (日)

大飯活断層調査 科学的な議論に徹するべきだ

The Yomiuri Shimbun August 25, 2013
Scientific discussions needed to handle Oi N-plant’s fault issue
大飯活断層調査 科学的な議論に徹するべきだ(8月24日付・読売社説)

A team of experts assembled by the Nuclear Regulation Authority has been discussing whether a fault that runs beneath Kansai Electric Power Co.’s Oi nuclear power plant in Fukui Prefecture—which has the nation’s only reactors currently in operation—is active and at risk of causing an earthquake. But those discussions have fallen into disarray.

The investigation being conducted by the team will be critical in deciding whether the Oi plant can continue its operations. But the team members have been at odds. One declared, with little evidence, “I believe it is highly likely that the fault under the plant is active.”

Can we call such discussions scientific? We have serious doubts.

A scientific approach requires a hypothesis to be tested objectively based on the results of experiments and measurements data. It is outrageous for an NRA inspector to make such a groundless claim.

Amid lengthy discussions among the NRA inspectors, a KEPCO official who was responsible for delivering a presentation and fielding their questions said at the nuclear watchdog’s fifth assessment session: “We have been carrying out the investigation [ordered by the NRA] day and night. We hope that you can conclude the assessment as soon as possible.” We understand why the official made this unusual request.
The team consists of five experts, including Kunihiko Shimazaki, acting NRA chairman. Since November, it has carried out three on-site inspections and five assessment meetings.

Shimazaki, who heads the team, should proceed with discussions in line with the NRA’s policy of evaluating the safety of nuclear facilities scientifically.

The fault in question is known as F-6. While KEPCO has argued that its Oi plant would not be seriously affected by an earthquake, some researchers insisted in June last year that the fault running beneath key facilities at the plant is active, prompting the government to launch an investigation.

Excessive digging

Under guidance by the NRA’s predecessor, the Nuclear and Industrial Safety Agency, KEPCO carried out excavations at locations along the F-6 fault. One resulting hole, dug at the orders of Shimazaki, is 70 meters long, 50 meters wide and 40 meters deep.

However, the work did not provide evidence determining that F-6 is active.

One expert on the team strongly criticized the move as haphazard, saying, “Was such massive excavation really necessary?”

Shimazaki defended his decision, saying in a monthly magazine, “Utilities usually try to get around such problems without conducting [physical investigations].” He added, “If we reinvestigate thoroughly, we can determine [whether the fault is active].”
It seems the NRA has exhausted all possible ways to investigate the matter.

At the NRA’s fifth assessment meeting, one expert said the discussions “will go on forever unless we arrive at a conclusion at some point.”
The NRA team should not put off reaching a conclusion without good reason.

In May, the NRA compiled an assessment report showing that a reactor at Japan Atomic Power Co.’s Tsuruga nuclear power plant sits on an active fault. But in July, the company submitted data to the NRA contradicting the regulator’s conclusion, calling on the body to conduct a reassessment. A scientific approach is likewise essential to deal with the fault issue at the Tsuruga plant.

(From The Yomiuri Shimbun, Aug. 24, 2013)
(2013年8月24日01時11分  読売新聞)


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