Tokyo Electric Power Co. (9501) said critical units of its Fukushima nuclear plant withstood shaking from the March 11 earthquake, Japan’s strongest on record, before being swamped by the tsunami that followed.
The surge knocked out cooling systems that led to meltdowns in three reactors at the Fukushima Dai-Ichi plant and the worst radiation release since Chernobyl in 1986, Tepco concluded in a report on the disaster. About 160,000 people were forced to flee the contamination and many areas near the plant may be uninhabitable for decades, government officials have said.
“This isn’t the end of the story. Tepco’s analysis needs to be reviewed by independent experts,” Tadashi Narabayashi, a former reactor safety researcher at Toshiba Corp. and now a nuclear engineering professor at Hokkaido University, said by phone before the release of the report. “The utility has often made mistakes in simulations that analyzed what happened.”
The company’s findings will be followed at the end of the month by the release of a government report on its probe into the catastrophe, which is being led by engineering professor Yotaro Hatamura.
Tepco set up an internal committee headed by Vice President Masao Yamazaki in June to investigate the nuclear accident. The 130-page interim report is accompanied by a 314-page attached book on plant data, a 69-page chronology of events and other documents. It was released today in Tokyo.
“We don’t know what the government committee will conclude in its investigation,” Yamazaki told reporters in Tokyo. “Even if it reaches a different conclusion, we will insist on the validity of our report.”
Tepco’s investigation concluded critical units of the station north of Tokyo weren’t significantly damaged by the quake because no unusual changes in the plant gauges were detected before the tsunami hit.
“The direct cause of the nuclear accident was the unprecedented tsunami,” an advisory body that reviewed the interim report said in a statement. Tepco’s lack of preparation made the crisis worse, the body led by Genki Yagawa, an honorary professor of Tokyo University, said.
A report in October from the Norwegian Institute for Air Research suggested there was “some structural damage to the reactor” during the earthquake that caused radiation to start leaking before the tsunami. The study was led by Andreas Stohl, an atmospheric scientist at the institute.
The Tepco committee probing the failures also found there was no explosion in the building of the No. 2 reactor. Three other reactor buildings were severely damaged by hydrogen explosions resulting from the melting of nuclear fuel.
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