In the days following the disaster at Fukushima, experts believed that getting the situation under control would be a simple matter. The reactor vessels were containing the nuclear fuel, and all that was needed was to pump water into the reactors until power could be restored and the plant’s cooling systems restarted. But it has proven much harder to control the situation than expected. Now, TEPCO, the utility in charge of the plant, says that fuel rods in at least one of the reactors melted and made a hole in the reactor vessel. It could take years to construct a containment wall to make up for the hole.
“There must be a large leak,” Junichi Matsumoto, a general manager at the utility [TEPCO] told a news conference.
“The fuel pellets likely melted and fell, and in the process may have damaged…the pressure vessel itself and created a hole,” he added… .
The finding makes it likely that at one point in the immediate wake of the disaster the 4-meter-high stack of uranium-rich rods at the core of the reactor had been entirely exposed to the air, he said. Boiling water reactors like those at Fukushima rely on water as both a coolant and a barrier to radiation.
U.S. nuclear experts said that the company may have to build a concrete wall around the unit because of the breach, and that this could now take years.
A summary of events at the plant through May 3 can be found here. The International Atomic Energy Agency says that the situation at the plant “remains very serious.”
In the United States, meanwhile, a review of nuclear power plants suggest they aren’t as safe as regulators had thought. The review, by the Nuclear Regulatory Commission, found problems with equipment installed after the 9/11 attacks to help keep reactors stable in the event of a terrorist attack or a disaster on the scale of the one at Fukushima.
From the New York Times:
Marty Virgilio, the deputy executive director of the agency, told the five commissioners that inspectors checked a sample of equipment at all 104 reactors and found problems at less than a third of them. The problems included pumps that would not start or, if they did, did not put out the required amount of water; equipment that was supposed to be set aside for emergencies but was being used in other parts of the plants; emergency equipment that would be needed in case of flood stored in places that could be flooded; and insufficient diesel on hand to run backup systems …
Another problem, staff members acknowledged, is that they have never paid much attention to the issues posed by handling an emergency when there is widespread damage to surrounding roads, power systems and communications links. In the past, the commission has explicitly rejected the notion that it should consider such combined events when reviewing a plant’s safety preparations.
And finally… a blue ribbon commission appointed to recommend what should be done with nuclear waste in the United States is meeting today, and is likely to recommend that spent fuel be stored above ground at centralized facilities for decades until a permanent storage facility is built. Spent fuel at the Fukushima plant contributed to radiation leaks there.