Tokyo Electric Power Co., in an interim report released Dec. 2, set out the line of defense it will attempt to hold against accusations of failures leading up to and during the crisis at its Fukushima No.1 nuclear power plant.
Tokyo Electric Power Co., in an interim report released Dec. 2, set out the line of defense it will attempt to hold against accusations of failures leading up to and during the crisis at its Fukushima No.1 nuclear power plant.The TEPCO investigative committee report, drawing on data from the plant’s monitoring systems and interviews with about 250 workers, stresses that the utility worked closely with the government and its nuclear agencies prior to the accident and complied with their safety standards.The authors pin the blame for the disaster on the enormity of the March 11 tsunami, which TEPCO argues was beyond anything that anyone had anticipated.The document, which will form the basis of a final report to be published in June after further scrutiny of TEPCO's decision-making and transparency, says measures such as installing multiple levels of emergency cooling equipment were carried out prior to the disaster and received the approval of central government safety inspectors. Of TEPCO’s contingency planning for serious accidents, the report says "steps were taken in close cooperation with the central government."It says the quake on March 11 was within the company’s estimates prior to that date. Although the company says there is no way to confirm the precise level of damage directly caused by the temblor itself, it asserts that no damage was likely caused to vital equipment. The tsunami triggered by the earthquake, however, greatly exceeded what had been planned for, according to the report. While various independent steps had been considered based on the most recent research, the report acknowledges that the measures actually implemented to deal with tsunami were inadequate and insufficient to prevent an accident.The report repeatedly states that the safety measures implemented were based on the views of government panels and experts.For example, concerning equipment and procedural manuals to deal with serious accidents, it says that TEPCO reported to the central government and received its approval based on a 1992 decision by the Nuclear Safety Commission. The report states that the core damage could not be prevented because the actual disaster greatly exceeded the assumptions on which safety measures were based.Some key areas of controversy are not covered by the document. A TEPCO official at the Dec. 2 news conference that coincided with the report’s release said the authors had avoided reference to issues which TEPCO officials maintain are unknown.For example, there is no explanation of the lack of measures taken to prevent a hydrogen explosion in the No. 1 reactor after radiation levels there reached extremely high levels before the actual blast.Immediately after the March 11 quake, the isolation condenser used to cool the No. 1 reactor kicked into operation, but workers at the plant decided to shut down the condenser. The report states that even if the condenser had continued to operate, it would not have prevented a worsening of the crisis because damage had already occurred in the reactor core.Tadashi Narabayashi, a professor of nuclear reactor engineering at Hokkaido University, said the report was short on answers to some of the key questions facing TEPCO."I do not see any evidence of new knowledge. What sticks out is the inclusion of only the facts without giving the cause. There were also items that will require further investigation into the cause, such as the increase in radiation levels in the No. 1 reactor building on the evening of March 11," he said.A panel of outside experts was commissioned by TEPCO to comment on the report. Panel member Genki Yagawa, professor emeritus at the University of Tokyo, said the disaster had happened because the company's mind-set was that no serious accident would ever occur."The direct cause of the accident was an unprecedented tsunami, but prior safety measures from both a hardware and software standpoint, including accident management steps, were insufficient," the outside panel said.TEPCO Executive Vice President Masao Yamazaki, who served as chairman of the company's accident investigation committee, said in response to the panel’s comments: "We have confirmed as fact that we made every effort to implement possible safety measures. We also took the necessary steps toward accident management. The cause of the latest accident was due to flooding caused by a tsunami that exceeded initial expectations."TEPCO will implement measures to prevent flooding of emergency power generators based on the report findings.