Japan’s nuclear crisis level has been regulated from level 5 to 7  by the International Atomic Energy Agency, at the top of the nuclear hazard scale and right on par with the 1986 Chernobyl incident, according to the level of radiation released in the accident. The new ranking signifies a “major accident” with “wider consequences” than the previous level, according to the Vienna-based IAEA.

“We have upgraded the severity level to 7 as the impact of radiation leaks has been widespread from the air, vegetables, tap water and the ocean,” said Minoru Oogoda of Japan’s Nuclear and Industrial Safety Agency.

The decision was made after assessments of data on leaks of radioactive iodine-131 and cesium-137 showed critical levels of radiation.

“We have refrained from making announcements until we have reliable data,” NISA spokesman Hidehiko 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 the Nuclear Security Council.

As opposed to the Chernobyl crisis, however, the Fukushima Dai-ichi plant hasn’t experienced any reactor core explosions, despite hydrogen explosions occurred during the first waves of tsunami which hit Japan after the deadly 9.0 earthquake. Actually, the amount of radiation leaking from the Fukushima Dai-ichi nuclear plant is around only 10 percent of the Chernobyl accident.

The magnitude-9.0 earthquake that caused the tsunami immediately stopped Fukushima’s three reactors, but overheated cores and a lack of cooling functions led to further damage. Engineers have been able to drop water into the damaged reactors to cool them down, but leaks have resulted in the pooling of tons of contaminated, radioactive water that has prevented workers from conducting further repairs – and if it wasn’t enough, aftershocks on Monday briefly cut power to backup pumps, halting the injection of cooling water for about 50 minutes before power was restored.

It could take weeks or months to stabilize the reactors. And containing and cleaning up the radioactive material could take at least 10 years, at a cost of more than $10 billion.

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