Tokyo, Japan - Japan's nuclear and industrial safety agency on Friday raised the level for the crisis at the Fukushima Daiichi nuclear plant from a 4 to 5 -- putting it on par with the 1979 incident at Pennsylvania's Three Mile Island.
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According to the International Nuclear Events Scale, a level 5 equates to the likelihood of a release of radioactive material, several deaths from radiation and severe damage to a reactor core.
Chernobyl, for example, rated a 7 on the scale, while Japan's other nuclear crisis -- a 1999 accident at Tokaimura in which workers died after being exposed to radiation -- was a 4.
In Pennsylvania, a partial meltdown of a reactor core was deemed the worst nuclear accident in U.S. history.