The top U.S. nuclear regulator, Gregory Jaczko, gave a dire assessment of Japan's nuclear crisis yesterday, saying that lethal radiation from uncovered spent fuel above one of the reactors could force emergency workers to abandon their fight to prevent meltdowns of damaged reactor cores at the Fukushima Daiichi plant.
Jaczko, chairman of the Nuclear Regulatory Commission, said his staff in Tokyo had been told by Japanese utility officials that cooling water that normally covers spent fuel was nearly or totally gone from an uncovered concrete pool above reactor Unit 4. Based upon that assessment, the U.S. Embassy in Tokyo advised Americans living within about 50 miles of the plant on Japan's northeast coast to evacuate farther away. Japan has called for an evacuation within about 12 miles of the plant.
His comments to a House committee were disputed but not explicitly denied by Japanese authorities, exposing an apparently major communications issue between the United States and Japan. If Jaczko's information was correct, the plant's owner, Tokyo Electric Power Co. (TEPCO) may have withheld information about the gravity of the crisis. If not, then a senior U.S. official may have wrongly inflamed fears in a country wracked by tragedy following last Friday's earthquake and tsunami.
"We can't get inside to check, but we've been carefully watching the building's environs, and there has not been any particular problem," Hajime Motojuku, a spokesman for Tokyo Electric, said Thursday morning in Japan, The New York Times reported.
Later Thursday, a spokesman for Japan's Nuclear and Industrial Safety Agency, Yoshitaka Nagayama, said, "Because we have been unable to go the scene, we cannot confirm whether there is water left or not in the spent fuel pool at Reactor No. 4."
Informed of Japanese reaction after his testimony yesterday, Jaczko told reporters, "I understand there is a conflict." He said the conclusions he and the NRC staff reached were based on the best information they had, and that they had chosen "to err on the side of caution." The possibility that fuel in the reactor pools could ignite led to the recommendation on evacuation, he said.
"The problem is that nobody knows," said Thomas Neff, a reactor safety expert affiliated with the Massachusetts Institute of Technology. "If you don't know and you're TEPCO, you probably underplay it. If you're the regulator, you probably see it in a worse light."
"The odds are pretty good that no one has good information," said Peter Bradford, a NRC commissioner at the time of the Three Mile Island accident in 1979. "We sure didn't during the first five days" then.
Japan's Self-Defense Forces dumped water from a helicopter on reactor No. 3 and prepared to repeat the operation on unit No. 4, Japanese news services reported. Water cannons would also be used. Jaczko said the water cover in the spent fuel storage pool at No. 3 may soon be gone too, boiled away or evaporated by the heat from the spent-- but still radioactive-- fuel rods.
The condition of the spent fuel pools has been a source of rising anxiety and confusion since the crisis began. The earthquake and tsunami knocked out outside power to the reactor complex and the tidal wave also disabled backup diesel generators, whose fuel tanks were swept away. When auxiliary batteries were exhausted, the plant was without power to continue cooling reactor cores and spent fuel pools. Japanese crews have been trying to flood reactors with seawater and restore outside power to the plant.
"There is an enormous amount of radioactivity left in those pools," Edwin Lyman of the Union of Concerned Scientists said. "[I]t's unclear how long workers can stay in that environment without risking grave bodily injury. If they must be permanently evacuated, it's unclear how the extent of the damage that's now occurred can be contained."