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Focus turns to avoiding blasts at Japan plant

April 6, 2011 12:00:00 AM PDT
After workers at the crippled Japanese nuclear plant stopped a leak pouring radioactive water into the Pacific, the focus has turned to injecting nitrogen to prevent more hydrogen explosions.

Another 11,000 tons of tainted water will have to be dumped at sea so plant repairs can continue.

However, a new confidential assessment by the Nuclear Regulatory Commission obtained by the New York Times suggests that the damaged Fukushima Daiichi plant is far from stable.

Nuclear officials said there was no immediate threat of explosions like the three that rocked the plant not long after a massive tsunami hit last month, but their plans are a reminder of how much work remains to stabilize the complex.

Until now, workers flooded the damaged reactors with water as a cooling method, but the latest assessment raises concerns that the water may have introduced a new set of dangerous complications. U.S. engineers now worry that the enormous amount of water is actually weakening the containment vessels, making them more vulnerable to possible ruptures.

Superheated fuel rods can pull explosive hydrogen from cooling water, so now that more water is going into the reactors to cool them down, the concern is that hydrogen levels are rising.

Technicians were expected to start pumping nitrogen into an area around one of the plant's six reactors early Thursday to counteract the hydrogen. They want to prevent hydrogen explosions at all costs because they could spew radiation and damage the reactors.

Stopping the leak by injecting several chemicals into the area around it seemed to help cut down on radiation. By afternoon, radiation at a point 360 yards (330 meters) off the coast was 280 times the legal limit, down from a high of more than 4,000, though officials said plant operator Tokyo Electric Power Co. was still watching closely.

As many as 25,000 people were killed by the tsunami.

The Associated Press contributed to this story