UPDATE 2-Fukushima reactor has a hole, leading to leakage

From Reuters:

One of the reactors at Japan's crippled Fukushima nuclear power plant has a hole in its main vessel following a meltdown of fuel rods, leading to a leakage of radioactive water, its operator said on Thursday.

The disclosure by Tokyo Electric Power Co (TEPCO) (9501.T: Quote, Profile, Research, Stock Buzz) is the latest indication that the disaster was worse than previously disclosed, making it more difficult to stabilize the plant.

The discovery of the leak provides new insight into the sequence of events that triggered a partial meltdown of the uranium fuel in the No. 1 reactor at Fukushima after the plant was struck by a massive earthquake and tsunami on March 11, officials said.

The battle to bring Fukushima under control has been complicated by repeated leaks of radioactive water, threatening both the Pacific Ocean and nearby groundwater.

Workers at the Fukushima Daiichi nuclear plant have been pumping water into at least three of the six reactors on the site to bring their nuclear fuel rods to a "cold shutdown" state by January.

But 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 about 5 metres (16 ft) below the targeted level to cover the fuel under normal operating conditions.

"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.

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