The four stricken reactors at the quake-hit Fukushima nuclear plant in northern Japan are to be decommissioned and scrapped.
The plant's operator, Tokyo Electric Power (Tepco) made the announcement on Wednesday three weeks after failing to bring reactors 1 - 4 under control. Reactors 5 and 6 have already been shut down safely.
The move follows reports that seawater near the reactors has a much higher level of radioactive iodine than previously thought, the BBC reports.
Water seeping from the No 1 reactor contains radioactive iodine at 3355 times the legal limit, a government agency says. That's more than 3000 times the legal limit for waste water around a nuclear power plant.
Earlier, samples had been put at 1850 times the legal limit.
The deputy director-general of Japan's nuclear safety agency, Hidehiko Nishiyama, says the iodine would have deteriorated considerably by the time it reached people.
Meanwhile, workers at the plant - damaged in the earthquake and tsunami on 11 March - are trying to prevent more radioactive water from seeping into the sea.
Small amounts of plutonium have also been detected in soil at the plant - suggesting that one of the reactors suffered a partial meltdown.
Prime Minister Naoto Kan says his government is on maximum alert, and the situation remains "unpredictable".
Meanwhile, the head of Tepco is in hospital because of high blood pressure, amid concerns that the company may collapse under the strain of paying for the disaster.
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