Japan has more than doubled its estimate of radiation that escaped from the tsunami-hit Fukushima nuclear plant in the first week after the disaster. Japan's nuclear safety agency also said meltdowns took place in three reactors more quickly than earlier believed. Japan's Nuclear and Industrial Safety Agency now says 770,000 terabecquerels escaped into the atmosphere – more than double its earlier estimate of 370,000 terabecquerels. The assessment comes as an expert panel begins an inquiry into the crisis. The plant's operator is hoping to shut down the facility by January, although there is concern it may take longer. The plant is still leaking radiation. The 11 March earthquake and the tsunami it generated are now known to have killed more than 15,280 people, while nearly 8,500 remain unaccounted for.