The New York Times reports that the chairman of the United States Nuclear Regulatory Commission (NRC) "gave a significantly bleaker appraisal" of the danger posed by Japan's nuclear crisis than previously delivered by either Japan's government or TEPCO, the operator of the damaged nuclear plants.
Today, the NRC chairman says the damage at one of the reactors is far more serious than officials in Japan have acknowledged. Based on information from the NRC, the American Embassy has told US citizens who are in Japan to evacuate within 50 miles around the plant, a significantly higher radius than the 12.4 miles advised by the Japanese government.
The NRC chief also said he now believes the water in the Fukushima No. 4 spent fuel pool has completely boiled dry, an assertion which Japanese officials deny.
Gregory Jaczko, the chairman of the commission, said in Congressional testimony that the commission believed that all the water in the spent fuel pool at the No. 4 reactor of the Fukushima Daiichi Nuclear Power Station had boiled dry, leaving fuel rods stored there completely exposed. As a result, he said, "We believe that radiation levels are extremely high, which could possibly impact the ability to take corrective measures."
If his analysis is accurate and Japanese workers have been unable to keep the spent fuel at that inoperative reactor properly cooled — covered with water at all times — radiation could make it difficult not only to fix the problem at reactor No. 4, but to keep workers at the Daiichi complex from servicing any of the other crippled reactors at the plant.
Mr. Jaczko said radiation levels may make it impossible to continue what he called the "backup backup" cooling functions that have so far prevented full nuclear meltdowns at the other reactors. Those efforts consist of dumping water on overheated fuel and then letting the radioactive steam vent into the atmosphere.
The emergency measures are all that has prevented the disaster at Daiichi from becoming a full blow meltdown.
Related: The chief of the U.N. nuclear agency, the IAEA, referred to the situation in Japan today as "very serious." Yukiya Amano said he planned to leave for Tokyo within a day.
Asked if events were out of control, he answered: "It is difficult to say."
His announcement in part appeared prompted by growing unease among the agency's 35 board member nations who have complained that information coming from Japan on the rapidly evolving nuclear disaster is too slow and lacking in detail.
Amano himself displayed some frustration with the information reaching his emergency operations team at IAEA headquarters in Vienna.
"There's a constant flow of information, but there are certainly grounds for improvement," he told reporters. He said that he planned to brief board members on what he learned as soon as possible after his return.