The New York Times says it was a pump that ran out of fuel: http://www.nytimes.com/2011/03/15/world/asia/15nuclear.html?hp
“The pump ran out of fuel,” [Cabinet Secretary] Mr. Edano said, “and the process of inserting water took longer than expected, so the fuel rods were exposed from the water for a while.” The Times says the problems at the Onagawa plant, 75 miles away, were not caused by that plant: Late Sunday night, the International Atomic Energy Agency announced that Japan had added a third plant, Onagawa, to the list of those under a state of emergency because a low level of radioactive materials had been detected outside its walls. But on Monday morning, it quoted Japanese authorities as saying that the radioactivity levels at the Onagawa plant had returned to normal levels and that there appeared to be no leak there. “The increased level may have been due to a release of radioactive material from the Fukushima Daiichi nuclear power plant,” the agency said. The Onagawa and Daiichi plants are 75 miles apart. The operator of the Onagawa plant, Tohoku Electric Power, said that levels of radiation there were twice the allowed level, but that they did not pose health risks. Read that slowly. It is appalling. The radiation levels 75 miles away from Fukushima are at twice the allowed level, and officials say the radioactive material "may have" came from Fukushima, not the Onagawa plant. So if it is twice the legal limit 75 miles away, how high is it right there at the plant? The stuff spreads out considerably over 75 miles, for crying out loud! - Jed
