Areas as far as 170 km away from the Fukushima nuclear plant faced the potential risk of being declared permanent evacuation zones, according to a worst-case scenario drawn up at the height of the crisis by the chief of the Japan Atomic Energy Commission.
The report, compiled March 25 at the request of then Prime Minister Naoto Kan, also said areas 250 km away — including central Tokyo — could have been tainted by radiation and require the government to assist those electing to voluntarily “migrate” away from the area.
The alarming 20-page report was written up by commission Chairman Shunsuke Kondo. The Japan Times obtained a copy of the report, the outline of which was first reported last month by the Mainichi Shimbun, from the Cabinet Office using the information disclosure law.
The report uses the same evacuation protocols adopted during the 1986 Chernobyl accident. Areas contaminated with 1,480 kilobecquerels of cesium 137 per sq. meter, for example, would have been designated as unlivable, or “forced migration,” zones, while those with 555 kilobecquerels per sq. meter would be declared “voluntary migration” zones, with the government offering to assist residents who elect to get out.
The areas 170 km away included parts of Fukushima, Miyagi, Tochigi and Ibaraki prefectures.
Kondo drafted the report after Kan asked him for a “worst-case situation,” Kondo told The Japan Times on Thursday.
Kondo’s scenario is based on the assumption that another hydrogen explosion would have further damaged reactor 1, releasing more radioactive fallout into the environment and forcing the entire plant to evacuate.
With no workers to control the situation, the cooling systems at reactors 1, 2 and 3 would be unrepairable and the spent-fuel pool in reactor 4 would collapse as the rods melted through its concrete walls, the report said.
Kondo emphasized that the scenario was based on extremes and not very realistic. The report assumed winds would continue at a certain strength and direction and did not consider local geography. As a result, the calculations were very rough and didn’t show how large the contaminated areas would in fact turn out to be, Kondo said.
“It’s not anything like SPEEDI,” said Kondo, referring to the System for the Prediction of Environmental Emergency Dose Information supercomputer simulation developed by the government to predict nuclear fallout in a crisis. SPEEDI’s results were initially withheld from the public.
The main aim of the report, Kondo said, was to show how the crisis might escalate and to offer technical recommendations on how to defuse the situation, not to give a detailed prediction of worst-case consequences, Kondo said.
In media interviews, Kan said he was particularly scared in the first week of the crisis because he had to entertain the possibility of evacuating the capital, without elaborating further.