TEPCO admits that the meltdown of the uranium fuel in the No. 1 reactor at Fukushima nuclear power plant has a hole in the reactor pressure vessel, leading to a leakage of radioactive water.
Reuters says the disclosure by Tokyo Electric Power Co (TEPCO) is the latest indication that the disaster was worse than previously disclosed, making it more difficult to stabilize the plant.
“It is necessary to make a reassessment of the condition of the nuclear reactor,” Chief Cabinet Secretary Yukio Edano told a news conference.
After repairing a gauge in the No. 1 reactor earlier this week, TEPCO discovered that the water level in the pressure vessel that contains its uranium fuel rods had dropped over 15 feet below the targeted level to cover the fuel under normal operating conditions.
Nearly 10,400 tonnes of water has been pumped into the reactor so far, but it is unclear where the leaked water has been going.
“There must be a large leak,” Junichi Matsumoto, a general manager at the utility 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.
Matsumoto said it was likely that the pressure vessels in the other two reactors could be leaking as well if fuel rods had collapsed and melted after the earthquake and tsunami
The high radiation levels makes it difficult for workers to check the site, Matsumoto said.
Based on the amount of water that is remaining around the partially melted and collapsed fuel, Matsumoto estimated that the Reactor 1 pressure vessel had developed a hole of several centimetres in diameter.
Matsumoto said the utility would study whether to increase the amount of water it was injecting to overcome the leak and raise the level of water covering the fuel, at the risk of allowing more radioactive water to leak out of the facility.
Arnie Gundersen, Chief Engineer at Fairewinds Associates Inc of Burlington, Vermont, said TEPCO should consider digging a trench around reactors 1-3 all the way down to the bedrock, which is about 50 feet below the surface.
He said this should be filled with zeolite, which can absorb radioactive cesium to stop more poisons from leaking into the groundwater around the plant.
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.
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