"We major changes not displayed from day to day," said the Chairman Gregory B. Jaczko, while added, that the risk of big additional releases will be small as every day goes by.
Long-term regular cooling of the reactors was not recovered, nor has a regular way of delivering water to the spent fuel pools, he said the Senate Environment and public works Committee. And when an aftershock hit the site and cut some offshore power supplies, he said, some pumps failed and cooling for 50 minutes ended.
The situation is "not stable" and remains so long, until "Such would be handled by situation in a predictable manner," he said.
Mr Jaczko offered a new theory about the cause of the explosions of that destroyed the secondary containment structures of several of the reactors. The prevailing theory was that hydrogen was created when it overheated reactor cores and with steam instead of water filled; Steam responds turns with the metal into a powder and then is from hydrogen.
The Tokyo electric power company, which nuclear operates plants, intended, vent excess steam, as well as the hydrogen outside the plant, but experts suspect, if try operators, broken the vents, so that the hydrogen give the secondary spot welds.
But Mr Jaczko said on Tuesday that the explosions in the created could have been caused secondary spot welds by hydrogen in the spent fuel pools within this spot welds.
If true, the introduction of hardened openings with reactors of nuclear power plants in the United States, that would mean - cited as an improvement that such an explosion happens prevent would - in the Act would make no difference.
This theory raises the possibility that it may be safer, move some of the spent fuel in dry storage, an idea that attracts a support in Congress and the pools containment structures. Spent nuclear fuel in the water for the first five years or so, but cool must remain in small steel and concrete silos without moving parts are stored.
The industry uses this "dry barrels" only if its pools are full. And so far the regulatory Commission has said, that pool and thin cut memory are as safe. Some industry executives would also tap to pay federal funds set aside for a thin permanent waste repository of nuclear waste Fund cut memory, an idea that is favoured by some environmentalists.
Mr Jaczko statement on the possible source of the hydrogen is the third large resolution in the Commission statements on the nuclear crisis on the Fukushima.
Commission officials have certainly seemed also less after indicating that the spent fuel pool in the reactor No. 4 was empty or near empty, a situation that was obviously a 50-miles evacuation for Americans in the vicinity of the plant the basis for the recommendation. Commission experts also said that radiation readings proposed that nuclear material slipped from the ship of the reactor No. 2 and a Drywell in the primary containment had entered only to retreat again about whether that was indeed the case.
Mr Jaczko also signals that the regulatory Commission from one extreme warning mode for a sustained long-term effort monitor was moved Japan's crisis. Staff in the Commission around the clock Emergency Center at the headquarters in Rockville, MD., has been reduced, he said, with many employees back to their regular duties but available if events warrant.
He drew praise from the Committee Chairman, Senator Barbara Boxer, a California Democrat, but also criticism. You looking for a particularly high degree of control for two twin reactor plants in their State, are the only ones who says the Commission in areas of high seismic activity. Mr Jaczko said that all the reactors have been evaluated.
You say neutralized that these two plants, Diablo Canyon and San Onofre, were at the highest risk. Mr Jaczko said they were not to explain that they were designed with the earthquake risk in mind and that risks to the American plants in General were low.
Woman Boxer replied that, at least until the March 11 accident had said the Japanese the same thing. "It gives me the creeps," she said. "I not enough humility of all us here sense."
A further witness, Charles G. Pardee, Chief Operating Officer, Exelon generation, the largest nuclear operator in the United States, testified also that for the worst natural disaster observed in their areas, plus a substantial safety margin in the country's nuclear power plants have been developed.
Thomas B. Cochran, a physicist at the natural resources Defense Council, gave some credit to American operators. Worldwide, he said, reactors are "The next nuclear power plant disaster is more abroad than in the United States" "do not sufficiently sure", but
But the industry to rethink its practices still must he said. "If the nuclear power industry is a long-term future have, on existing operational reactors must be respected," said Mr. Cochran. He ticked off a long list of factors, including the American reactors, which would them be Fukushima's basic design, together, using reasons for the phasing out.
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