The nuclear accident in Japan is now in the same category as the Chernobyl disaster in the Soviet Union.The move was based on new data on the amount of radiation released in the early days of the crisis, not on any recent change in the plant's status. The Japanese government emphasizes that the Fukushima Dai-ichi plant has released only one tenth the amount of radiation released at Chernobyl, meaning the lasting effects on human health in Japan are expected to be far less severe.
http://www.npr.org/2011/04/12/135324541/cleaning-up-fukushima-a-challenge-to-the-core
http://www.npr.org/2011/04/12/135324541/cleaning-up-fukushima-a-challenge-to-the-core