Chairman of the Nuclear Regulatory Commission Gregory Jaczko, said that no water remains in a deep pool used to cool spent fuel at the plant and that radiation levels there are thought to be “extremely high.” The Associate Press reported that Japanese officials denied that the water is gone from the spent-fuel pool.
Jaczko, testifying before the House Energy and Commerce Committee on what his agency has been told about the crisis, said the plant’s unit 4 reactor appeared to have suffered a hydrogen explosion.
The reactor at unit 4 was shut down at the time of the earthquake last Friday, meaning that crews had transferred all of the radioactive fuel from the reactor’s core to the pool. The building housing the pool was damaged when two nearby reactor buildings exploded Saturday and Monday.
“It’s unprecedented,” said David Helwig, a retired nuclear engineer who spent 40 years working on boiling water nuclear reactors of the same design as those at Fukushima Daiichi. “That’s never happened before.”
Left exposed to the air, the fuel rods will start to decay and release radioactivity into the air.
Severe structural damage is the only way the fuel pool could be emptied, Helwig said. The 50-foot-deep pools have no outlets at the bottom, thus preventing them from draining in case of an accident.
The spent-fuel pool at another reactor, unit 3, also appeared compromised, Jaczko said.
The increasingly desperate picture of the struggle at the stricken nuclear plant emerged after Japanese helicopter crews abandoned an attempt to dump water on the pools of uranium fuel after detecting dangerous radiation above the plant.
Also Wednesday, the director general of the International Atomic Energy Agency confirmed damage to three of the facility’s six nuclear reactors, which contain radioactive fuel that is hotter, and more radioactive, than the fuel stored in the damaged pools.
In another sign of the worsening crisis, the U.S. ambassador to Japan warned Americans to stay at least 50 miles from the plant — more than four times the distance recommended in the Japanese government’s evacuation plan. Japanese authorities confirmed that crews at the plant had to temporarily abandon their posts as radiation readings spiked.
Jaczko’s testimony suggested that damage to the plant is worse than the Japanese government and the plant’s operator, Tokyo Electric Power Co., has acknowledged. On Tuesday, the company said water levels in the three of the site’s seven fuel pools were dropping, but did not say that the fuel rods themselves had been exposed.
Such exposure has been a huge concern among some longtime critics of the standard practice at nuclear facilities of storing used, or “spent,” fuel in structures that lack the heavy concrete-and-steel shields surrounding the reactor cores themselves.
A report on the Japanese crisis this week by Barclays Capital said, “Never, never, never allow the water level in a nuclear reactor to fall below the level of the fuel. This is the mantra pounded into the minds of nuclear power plant operators all over the world.” The report added, “It is hard to overemphasize the importance of the ‘keep the fuel covered’ training and design of these plants.” One of the report’s authors formerly provided such training at a U.S. commercial nuclear plant.
The only solution sounds simple but has apparently proved impossible for the Japanese crews: spray water by any means possible. “Just get a firehose up there if you can,” said Arnie Gundersen, a nuclear engineer.
The lack of water in at least one spent-fuel pool sparked fears of a worst-case scenario: the fuel could combust.
“If there’s no water in there, the spent fuel can star a fire,” said Eric Moore, a consultant to the Nuclear Regulatory Commission on nuclear plant design and safety issues. “Once you have that fire, there’s a high risk of radiation getting out, spewed by the fire.”
In Japan, authorities scrambled Wednesday to find ways to cool the overheated elements at the nuclear plant and prevent them from emitting potentially lethal radiation.
As radiation levels in the air above the plant spiked dangerously for the second consecutive day, U.S. Ambassador John V. Roos issued a recommendation based on a review of “the deteriorating situation” at the Fukushima Daiichi nuclear power plant by experts from the NRC and Energy Department.
“Consistent with the NRC guidelines that apply to such a situation in the United States, we are recommending, as a precaution, that American citizens who live within 50 miles (80 kilometers) of the Fukushima Nuclear Power Plant evacuate the area or to take shelter indoors if safe evacuation is not practical,” Roos said in a statement.
Japan has asked people living within 12 miles of the plant to evacuate and urged those living between 12 and 18 miles away to stay indoors. The Fukushima Daiichi plant, about 150 miles north of Tokyo, is one of Japan’s largest nuclear facilities and is normally capable of producing more than 4,500 megawatts of electricity.
The conflicting evacuation recommendations prompted a barrage of questions at Wednesday’s White House and State Department news briefings about the adequacy of the information Japan is providing to its citizens.