Apr 12, 2011 9:32 AM by CBS/AP
TOKYO - Japan raised the severity level of the crisis at its crippled nuclear plant Tuesday to rank it on par with the 1986 Chernobyl disaster, citing cumulative radiation leaks that have contaminated the air, tap water, vegetables and seawater.
Japanese nuclear regulators said the rating was being raised from 5 to 7 - the highest level on an international scale overseen by the International Atomic Energy Agency - after new assessments of radiation leaks from the Fukushima Dai-ichi plant since it was disabled by the March 11 tsunami.
The new ranking signifies a "major accident" that includes widespread effects on the environment and health, according to the Vienna-based IAEA.
While Japanese officials have played down any health effects so far, the revision came a day after the government added five communities to a list of places people should leave to avoid long-term radiation exposure. A 12-mile radius already had been cleared around the plant.
Japanese officials have said the leaks from the Fukushima plant so far amount to a tenth of the radiation emitted in the Chernobyl disaster, while acknowledging they eventually could exceed Chernobyl's emissions if the crisis continues.
"This reconfirms that this is an extremely major disaster. We are very sorry to the public, people living near the nuclear complex and the international community for causing such a serious accident," said Chief Cabinet Secretary Yukio Edano.
But Edano told reporters there was no "direct health damage" so far from the crisis. "The accident itself is really serious, but we have set our priority so as not to cause health damage."
To quell anxiety, the government has launched statewide radiation screenings of citizens and property at thousands of checkpoints, but the government's assurances have provided little comfort to the residents of Fukushima, reports CBS News correspondent Lucy Craft.
Hironobu Unesaki, a nuclear physicist at Kyoto University Research Reactor Institute, said the revision was not a cause for worry, that it had to do with the overall release of radiation and was not directly linked to health dangers. He said most of the radiation was released early in the crisis and that the reactors still have mostly intact containment vessels surrounding their nuclear cores.
The change was "not directly connected to the environmental and health effects," Unesaki said. "Judging from all the measurement data, it is quite under control. It doesn't mean that a significant amount of release is now continuing."
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Continued aftershocks following the 9.0-magnitude megaquake on March 11 have impeded work in stabilizing the Fukushima plant - the latest a 6.3-magnitude one Tuesday that prompted plant operator Tokyo Electric Power Co., or TEPCO, to temporarily pull back workers.
Officials from Japan's Nuclear and Industrial Safety Agency said that the cumulative amount of radioactive particles released into the atmosphere since the incident had reached levels that apply to a Level 7 incident. Other factors included damage to the plant's buildings and accumulated radiation levels for its workers.
The revision was based on cross-checking and assessments of data on leaks of radioactive iodine-131 and cesium-137, NISA spokesman Hidehiko Nishiyama said.
"We have refrained from making announcements until we have reliable data," Nishiyama said. "The announcement is being made now because it became possible to look at and check the accumulated data assessed in two different ways," he said, referring to measurements from NISA and Japan's Nuclear Security Council.