Tsunami Protections « nuclear-news

TEPCO asked subsidiary to underestimate tsunami threat at Fukushima nuke plant: worker

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.

https://mainichi.jp/english/articles/20180301/p2a/00m/0na/003000c

Fukushima Daiichi Urged To Prepare For Future Tsunamis; No Sarcophagus For Meltdowns

TEPCO urged to cut risk of radioactive water leak
Japan’s nuclear regulator has urged the operator of the crippled Fukushima Daiichi nuclear power plant to reduce the risk of leaking of highly radioactive water from the facility into the sea, in case of another tsunami.
About 60,000 tons of such water is believed to have pooled in reactor buildings at the plant. The operator, Tokyo Electric Power Company, or TEPCO, is injecting water into the buildings to cool melted nuclear fuel, and groundwater is flowing into their basements.
The Nuclear Regulation Authority instructed TEPCO at a meeting on Tuesday to urgently study measures to lower the amount and radiation levels of the water.
The authority proposed 2 measures to TEPCO. One is building more tanks to store the water, even though the plant has about one thousand tanks. The other is treating the water using a system designed to filter out radioactive material, and circulating the water in a cooling system.
NRA member Toyoshi Fuketa said the utility cannot keep the water in the buildings forever. He said TEPCO should handle the water problem either along with that of other radioactive water or first of all.
Following the NRA’s instruction, TEPCO is to report the results of its study at a meeting next month or later.

State minister rules out sarcophagus option
Japan’s state minister for industry has ruled out the option of sealing off disabled reactors at the Fukushima Daiichi nuclear plant with a Chernobyl-style sarcophagus.