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Tsunami could overtake Fukushima Daiichi’s seawall

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April 21, 2020

An estimate by a Japanese government panel suggests that tsunami could overwhelm a new seawall at the Fukushima Daiichi nuclear power plant, if a mega-quake occurs in a deep-sea trench off northeastern Japan.

The panel of experts on Tuesday released its projection of the scale of tsunami that could be triggered by a massive quake along the Japan Trench.

The panel expects that waves as high as 13.7 meters could hit Futaba Town, Fukushima Prefecture, where the plant is located.

That is higher than the 11-meter-high seawall being built on the ocean side of the compound. The wall is one of the anti-tsunami measures taken by Tokyo Electric Power Company as it decommissions the plant.

Other measures include blocking the openings of the reactor buildings and deploying power supply vehicles on higher ground to continue cooling spent nuclear fuel.

TEPCO says it will examine the estimate and consider what measures to take.

Nearly 1,000 tanks of radioactive wastewater are stored in the compound. The operator says the projected tsunami won’t reach the higher ground where they are located.

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April 24, 2020 Posted by | Fukushima 2020 | , , | Leave a comment

New tsunami estimates for megaquakes off Japan

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April 21, 2020

A Japanese government panel says tsunami waves measuring more than 20 meters high could hit northern Japan if a megaquake of magnitude 9 or stronger occurs in one of two deep-sea trenches.

The government panel has been studying the possible scale of an earthquake, and tsunami waves it could trigger, in either a part of the Chishima Trench or the Japan Trench. The targeted area of the Chishima Trench extends from the Kuril Islands to Hokkaido while the area of the Japan Trench extends from Hokkaido to Iwate Prefecture. The study began after the 2011 disaster in northeastern Japan.

The panel’s latest estimate says a quake along the Chishima Trench would have a magnitude of 9.3.

Parts of eastern Hokkaido would be hit by tremors with an intensity of six-plus to seven on the Japanese scale of zero to seven.

A wide area of eastern Hokkaido would see tsunami more than 20 meters high. Waves could reach 27.9 meters in the town of Erimo.

A quake along the Japan Trench would have a magnitude of 9.1. Parts of Aomori and Iwate prefectures could have tremors with an intensity of six-plus.

Tsunami waves would top ten meters in northeastern Japan. Hachinohe City in Aomori Prefectures would be hit by tsunami as high as 26.1 meters, and Miyako City in Iwate Prefecture as high as 29.7 meters. Some areas could be hit by waves higher than those that struck in 2011.

As these areas have had powerful earthquakes in the past, the panel says massive tsunami can strike at any time.

The Cabinet Office plans to estimate the extent of damage and draw up disaster control measures based on these new figures by the end of March next year.

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April 24, 2020 Posted by | Japan | , , | Leave a comment

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

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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.
 

March 2, 2018 Posted by | Fukushima 2018 | , , , | Leave a comment

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.

July 27, 2016 Posted by | Fukushima 2016 | , , , | Leave a comment