Tokyo Electric Power Co. (TEPCO) asked a subsidiary in 2008 to underestimate the scale of tsunami that could hit the Fukushima No. 1 Nuclear Power Plant before tsunami devastated the facility in March 2011, a subsidiary employee told a court.
The worker at Tokyo Electric Power Services Co. (TEPSCO) appeared as a witness at the hearing of three former TEPCO executives under indictment on charges of professional negligence resulting in death and injury at the Tokyo District Court on Feb. 28.
The man played a key role in TEPSCO's estimate of the scale of possible tsunami, which could hit the premises of the plant, between 2007 and 2008.
Based on a long-term evaluation by the government's Headquarters for Earthquake Research Promotion, the employee estimated that tsunami up to 15.7 meters high could hit the atomic power station. In its evaluation, the quake research headquarters had warned that a massive tsunami could occur off the Sanriku region including Fukushima Prefecture. The area was later devastated by a massive tsunami triggered by the March 11, 2011 Great East Japan Earthquake, causing the Fukushima nuclear crisis.
In his testimony, the employee told the court that he briefed TEPCO headquarters of the outcome of TEPSCO's estimate of possible tsunami in March 2008. An employee at TEPCO headquarters subsequently asked the witness whether the estimated scale of possible tsunami could be lowered by changing the calculation method.
In response, the employee recalculated the possible tsunami based on different movements of tsunami waves he assumed, but he obtained an all but identical figure, the employee told the court hearing. He added that in the end, the prediction was not accepted as the utility's estimate of possible tsunami hitting the power plant.
The man testified that his estimation of up to 15.7-meter-high tsunami hitting the power plant was "within the scope of his assumption because the calculation was based on the 1896 Sanriku earthquake that triggered over 30-meter-high tsunami."
During the hearing, court-appointed lawyers, acting as prosecutors to indict the three former TEPCO executives, said that TEPCO headquarters considered measures to protect the Fukushima No. 1 nuclear complex from tsunami after being briefed of the outcome of TEPSCO's tsunami estimate.
Nevertheless, the lawyers asserted that those who were on the company's board at the time postponed drawing up tsunami countermeasures by deciding to commission the Japan Society of Civil Engineers to look into the matter, eventually opening the door to the nuclear crisis.
Public prosecutors had decided not to indict the three former TEPCO executives. However, under the Act on Committee for Inquest of Prosecution, court-appointed lawyers prosecuted them after a prosecution inquest panel comprising members selected from among the public concluded twice that the three deserved indictment.