UPDATE AS OF 8:30 A.M. EDT, TUESDAY, APRIL 12:
Japan’s nuclear safety agency has raised the crisis level of the Fukushima Daiichi accident from 5 to 7 on the seven-level International Nuclear and Radiological Event Scale. The new rating puts the Japanese incident on the same level as the 1986 Chernobyl accident—even though Japanese authorities estimate that radiation released at Fukushima is only 10 percent of the amount released from the Ukrainian plant.
The new level designates Fukushima as a “major accident,” up from an “accident with wider consequences.” Level 7, the highest on the scale, describes an event with “a major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures," according to the International Atomic Energy Agency, which sponsors the ratings.
For the new rating, the Japan Nuclear and Industrial Safety Agency combined the accidents at reactors 1, 2 and 3 as a single event. Previously, separate level 5 ratings had been applied to each reactor. The earlier level 3 rating (“serious incident”) still applies to reactor 4.
Japanese authorities may revise the INES rating at the power plant as more information becomes available.