Sixteen months after crippled nuclear reactors poisoned a swath of Fukushima prefecture for decades to come and forced 160,000 residents to evacuate, independent investigators can’t agree on just what went wrong.
They do agree more study is needed into the meltdowns at Tokyo Electric Power Co. reactors after the magnitude-9 earthquake and tsunami of March 11, 2011. They differ on how the twin natural disasters combined to cause the worst nuclear accident since Chernobyl in 1986.
University of Tokyo engineering professor Yotaro Hatamura’s team reported today that the quake didn’t cause enough damage to rupture containment vessels at the Dai-Ichi nuclear plant. Findings by a group under Kiyoshi Kurokawa, professor emeritus of the same school, say “man-made” failures led to the disaster and it can’t be ruled out the quake did more damage to the plant than believed before it was swamped by the tsunami.
“The government shouldn’t close its accident investigation into Fukushima with the end of probes by our committee and the parliamentary commission,” led by Kurokawa, Hatamura’s panel reported. “When radiation levels fall, detailed on-site examination inside reactor buildings, including examination of quake effects, must be carried out.”
Hatamura, who specializes in studies of industrial accidents caused by design flaws and human error, was appointed by the government in May last year to lead an investigation that led to 1,479 hours of hearings with 772 people including former Prime Minister Naoto Kan.
The commission’s 448-page final report echoes criticism of Tokyo Electric by others. Besides a failure of disaster management and risk analysis, the utility lacks “sufficient enthusiasm to fully investigate the Fukushima disaster and learn lessons to prevent recurrence even more than one year after the accident,” it said.
Tepco’s own research showed the plant might be subject to a tsunami of more than 10 meters. Its executives knew of that data, the utility said last August, contradicting earlier claims by former President Masataka Shimizu and other officials that such a disaster was unforeseeable.
Seismologists warned of tsunami risk along the coasts of Fukushima and Ibaraki prefectures at government meetings between 2003 and 2006, the Hatamura commission said. Those warnings weren’t incorporated into disaster planning, instead being dismissed by bureaucrats who demanded more studies, the commission said.
“As scientific knowledge about earthquakes is still insufficient, we must keep incorporating new findings into disaster prevention measures,” according to Hatamura’s report. The government shouldn’t ignore warnings by even a small number of seismologists, it said.
Tokyo Electric, known as Tepco, has a history of covering up operation problems at its nuclear plants.
In 2002, Tepco admitted it had falsified repair reports at nuclear plants for more than two decades. Chairman Hiroshi Araki and President Nobuya Minami resigned after it was revealed the company had submitted false data to the regulator on hundreds of occasions.
Then in 2007, the utility said it had concealed at least six emergency stoppages at its Fukushima station and a “critical” reaction at the plant’s No. 3 reactor that lasted for seven hours.
Over the weekend, a Tepco affiliate Tokyo Energy & Systems Inc. said it had contracted out work at Fukushima to a company known as Build-Up, according to Tokyo Energy’s website and a company official, who declined to be named.
Build-Up then sent workers into the plant with lead plates to mask radiation meters, which would allow them to work for longer periods in potentially dangerous areas contaminated by radioactivity.
Five workers covered their dosimeters with lead plates in December after a supervisor at Build-Up ordered it, Tokyo Energy & Systems said in a statement today, citing its own investigation.
Tokyo Energy & Systems shares fell as much as 9.2 percent to 334 yen, the lowest since Oct 2011, on the midday break today on the Tokyo Stock Exchange. Tepco shares declined 0.8 percent to 129 yen.
Additionally, the Nuclear and Industrial Safety Agency has ordered Japan Atomic Power Co., Kansai Electric Power Co. and Hokuriku Electric Power Co. to run additional seismic investigations at their Tsuruga, Ohi and Shika nuclear plants this year after scientists said they may be atop active earthquake faults.
Kansai Electric restarted two reactors this month at its Ohi plant in Fukui prefecture, about 90 kilometers (56 miles) northeast of Osaka. They are the only operating nuclear units in Japan after the government approved their restart in the face of anti-nuclear rallies and protest marches by tens of thousands of people.