Fukushima meltdown risk 'kept secret for months'

Four hours after a tsunami swept into the Fukushima nuclear power plant a year ago today, Japan's leaders knew the damage was so severe that the reactors could melt down, but they kept their knowledge secret for months. Five days into the crisis, the then prime minister, Naoto Kan, voiced his fears that it could turn worse than Chernobyl.

The revelations were in documents released on Friday. The minutes of the government's crisis management meetings from 11 March – the day the earthquake and tsunami struck – until late December were not recorded and had to be reconstructed retrospectively. They illustrate the confusion, lack of information, delayed response and miscommunication among government, affected towns and plant officials, as some ministers expressed the sense that nobody was in charge when the plant conditions quickly deteriorated.

Apparently the government tried to play down the severity of the damage. A spokesman for the Nuclear and Industrial Safety Agency was replaced after he slipped out a possibility of meltdown during a news conference on 12 March. The plant operator, Tokyo Electric Power Co, acknowledged a partial meltdown much later, in May.

It was nearly 10 days before one of the prime minister's top nuclear advisers produced a worst-case scenario at his request. The 25 March report warned that a disaster of that scale would require evacuating 30 million people from the greater Tokyo area. Fearing panic, the government kept the report a secret, but the Associated Press obtained it in January.

The failure to record the minutes of the meetings has added to public criticism of how the crisis was handled.