The working group of the government’s Nuclear Safety Commission (NSC) instructed power utilities to “write a composition” in 1992 on why there would be no need for the nuclear watchdog to consider a long-term power loss at nuclear power plants in its review of the country’s safety guidelines for nuclear reactor designs, it has been learned.

The views expressed by the power industry were eventually incorporated into the report prepared by the working group, and as a result of this, NSC decided not to revise the country’s nuclear safety guidelines. It was revealed in archive documents released by NSC on June 4 in line with a request filed by the Diet’s committee tasked with investigating the crisis at the Fukushima No. 1 Nuclear Power Plant. The loss of power sources was a major factor behind the Fukushima nuclear disaster.

The nine-member working group was comprised of nuclear experts and employees of utility companies. Following a complete power loss at a nuclear power plant in the United States as a result of losing both external and emergency power sources, the working group had been studying from 1991 to 1993 whether to revise the country’s safety guidelines, which stipulated that “it is not necessary to consider a long-term power loss.”

According to NSC, the power industry had stood against an attempt to revise the safety guidelines in those days, saying things like: “It is proper to conclude that we expect the power companies to make efforts in the future,” and “the risk (of a long-term power loss) is rather low, and therefore it is too much to reflect it in the guidelines.”

In response to this, the Nuclear Safety Investigation Section under the then Science and Technology Agency, acting as the secretariat of the working group, instructed the utilities in writing to “write a composition on reasons why there is no need to consider a medium- and long-term power loss.” After receiving a reply from Tokyo Electric Power Co. (TEPCO) which said, among other things, “Safety can be fully secured if proper operations are conducted,” the working group reflected the text written by TEPCO almost entirely in its report.

NSC Chairman Haruki Madarame apologized for what happened some 20 years ago, saying. “It was clearly inappropriate to have utility firms take their share of writing a draft report. I am very sorry.” Although NSC was aware of the internal documents in question in June last year, it did not release them. The secretariat said, “We had been proceeding with preparations to release them, but we were busy with other work.”