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Ex-NRA bigwig demands recalculation of Oi nuclear plant quake estimate

A former deputy chairman of the Nuclear Regulation Authority (NRA) sent the organization a letter of protest on July 14 demanding that an earthquake estimate for Kansai Electric Power Co. (KEPCO)'s Oi Nuclear Power Plant be recalculated, on the grounds that the official NRA estimate is well below that of KEPCO.

    The former deputy chairman, Kunihiko Shimazaki, is a professor emeritus of seismology at the University of Tokyo. He had criticized the NRA's estimate of the largest possible earthquake at the Oi plant in Fukui Prefecture as possibly being too low, and the NRA recalculated the estimate in a different manner but still deemed the projected earthquake as not posing a problem to the plant's safety. In his letter of protest he wrote that he "could not accept the conclusion" of the NRA, and he called for another recalculation. He said he would hold a press conference on July 15 about the issue.

    The NRA's recalculated estimate was 644 gals, "gal" being a unit of acceleration. The estimate was below a KEPCO estimate of 856 gals. Shimazaki, in response to the figures, argues that the NRA's calculation method is different from KEPCO's and so produced a smaller number, and notes that the utility finalizes its estimate with additional calculation under stricter conditions, but the NRA has not done so. Shimazaki says that if the calculation was carried out in the same way as KEPCO has performed its estimate, the figure would come out to roughly up to 1,550 gals.

    On July 13, a representative for the NRA's secretariat acknowledged in a Mainichi Shimbun interview that the NRA's calculation method differed from KEPCO's, saying, "It's only natural that there is a difference (in the calculation results)." The representative avoided giving a clear answer about whether it was right for the NRA to green light the plant by comparing results calculated in different methods.

    Shinji Kinjo, the head of the agency's public relations department, said, "If there is a request (for a recalculation), we will consider it sincerely."

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