JOIN USThe radioactive leak at the troubled plant is thus the severest nuclear crisis, Xinhua reported quoting Japan's Nuclear and Industrial Safety Agency
Agency officials said the radioactive severity at No.1, No.2 and No.3 reactors was rated at level five while that at No.4 was rated at level three. On Sunday the agency rated the incident at the No.1 reactor at level four after radioactive substances were detected there.
The upgrade has made Japan's nuclear leak severity rise to the same level as the Three Mile Island accident in the US in 1979. The Fukushima nuclear plant facility was damaged after Japan's northeastern part was rattled by last week's magnitude-9 earthquake and ensuing tsunami in which more than 6,000 people have been confirmed dead so far.