Japan’s crisis put at level of Chernobyl’s
Agency says high levels of radiation leaked after quake
TOKYO — Japan has decided to raise its assessment of the accident at the crippled Fukushima Daiichi nuclear power plant from 5 to the worst rating of 7 on an international scale, putting the disaster on par with the 1986 Chernobyl meltdown, the Japanese nuclear regulatory agency said today.
According to the International Nuclear Event Scale, a level 7 nuclear accident involves “widespread health and environmental effects’’ and the “external release of a significant fraction of the reactor core inventory.’’
Japan’s previous assessment of the accident put it at level 5 on the scale, the same level as the Three Mile Island accident in the United States in 1979. The level 7 assessment had been applied only to the disaster at Chernobyl in the former Soviet Union.
The scale, which was developed by the International Atomic Energy Agency and countries that use nuclear energy, requires that the nuclear agency of the country where the accident occurs calculate a rating based on complicated criteria.
Japan’s Nuclear and Industrial Safety Agency said at a news conference this morning that the rating resulted from new estimates by the Nuclear Safety Commission that suggest some 10,000 terabecquerels of radiation per hour were released from the plant into the environment for several hours in the aftermath of the March 11 earthquake and tsunami. (The measurement refers to how much radioactive material was emitted, not the dose absorbed by living things.)
The scale of the radiation leak has since dropped to under 1 terabecquerel per hour, the Kyodo News agency said, citing the commission. Commission officials in Tokyo said they could not immediately comment.
Michael Friedlander, a former senior nuclear power plant operator for 13 years in the United States, said that the biggest surprise in the Japanese reassessment was that it took a month for public confirmation that so much radiation had been released.
Some in the nuclear industry have been saying for weeks that the nuclear accident released large amounts of radiation, but Japanese officials had consistently played down this possibility.
The announcement came as Japan is preparing to urge more residents around a crippled nuclear power plant to evacuate, because of concerns over long-term exposure to radiation.
Also yesterday, tens of thousands of people bowed their heads in silence at 2:46 p.m., exactly one month since the 9.0-magnitude earthquake and ensuing tsunami brought widespread destruction to Japan’s northeast coast.
The mourning was punctuated by another strong aftershock near Japan’s Pacific coast, which briefly set off a tsunami warning, killed at least one person, and knocked out cooling at the severely damaged Fukushima Daiichi Nuclear Power Station for almost an hour, underscoring the vulnerability of the plant’s reactors to continuing seismic activity.
This morning, there was another strong aftershock, which shook Tokyo.
The authorities have already ordered people living within a 12-mile radius of the plant to evacuate, and recommended that people remain indoors or avoid an area within a radius of 18 miles.
The government’s decision to expand the zone came in response to high readings of radiation in certain communities beyond those areas, underscoring how difficult it has been to predict the ways radiation spreads from the damaged plant.
Unlike the previous definitions of the areas to be evacuated, this time the government designated specific communities that should be evacuated, instead of a radius expressed in miles.
The radiation has not spread evenly from the reactors, but instead has been directed to some areas and not others by weather patterns and the terrain. Iitate, one of the communities told yesterday to prepare for evacuation, lies well beyond the 18-mile radius, but the winds over the last month have tended to blow northwest from the Fukushima plant toward Iitate, which may explain why high readings were detected there.
Yukio Edano, the government’s chief cabinet secretary, said that the government would order Iitate and four other towns and villages to prepare to evacuate.
Officials are concerned that people in these communities are being exposed to radiation equivalent to at least 20 millisieverts a year, he said, which could be harmful to human health over the long term.
Evacuation orders will come within a month for Katsurao, Namie, Iitate and parts of Minamisoma and Kawamata, Edano said.