Japan's nuclear crisis deepens as third reactor loses cooling capacity

By Steven Mufson
Monday, March 14, 2011; 11:18 PM

Japan wrestled to regain control of ultra-hot fuel rods in three nuclear reactors as water pumps failed and the third explosion in four days rocked the seaside Fukushima Daiichi nuclear power complex early Tuesday.

Officials from Tokyo Electric Power, the plant owner, said the 6:14 a.m. explosion took place in the unit 2 reactor at or near the suppression pool, which collects water and radioactive elements from the containment vessel.

Experts said that, unlike the two previous explosions that destroyed outer buildings, this one might have damaged valves and drain pipes, possibly creating a path for radioactive materials to escape.

The explosion - more serious than the earlier blasts - was followed by a brief drop in pressure in the vessel and a spike in radioactivity outside the reactor to levels more than eight times what people ordinarily receive in a year, the company said. Tokyo Electric, which over the weekend said it had 1,400 people working at the complex, said it was evacuating all nonessential personnel, leaving about 50 people there.

Prime Minister Naoto Kan told the nation Tuesday morning that radiation had spread from the reactors and there was a very high risk of further radioactive material escaping. He urged people within 19 miles of the plant to remain indoors. He urged calm.

But Kan also said a fire had broken out at a fourth reactor unit.

The new setbacks came on the heels of a difficult Monday at Fukushima Daiichi unit 2. Utility officials there reported that four out of five water pumps being used to flood the reactor had failed and that the other pump had briefly stopped working. As a result, the company said, the fuel rods, normally covered by water, were completely exposed for 140 minutes, hastening the partial meltdown of them that most experts think is underway.

According to a report by the Kyodo news agency, the fifth pump was later restarted, and seawater mixed with boron was again injected in a desperate bid to cool the reactor, but the fuel rods remained partially exposed and ultra-hot. On Tuesday morning, Tokyo Electric said that 2.7 meters of the rods were still exposed.

The other four pumps were thought to have been damaged by a blast Monday that destroyed a building at the nearby unit 3 reactor, Kyodo reported. That blast, like one on Saturday at unit 1, was caused by a buildup in hydrogen generated by a reaction that took place when the zirconium alloy wrapped around the fuel rods was exposed to steam at 2,200 degrees Fahrenheit.

The International Atomic Energy Agency reported that injections of seawater into units 1 and 3 had been interrupted because of a low level in a seawater supply reservoir, but the seawater injections were later restored.

A commercial satellite photo of the complex showed piles of debris on top of units 1 and 3, which raised new fears about the condition of the pools where spent fuel is stored, especially at unit 1, where a design by General Electric placed the pool on top of the reactor but below the outer structure, which was destroyed. But the ability of workers to assess the damage was hindered by fears that another explosion might occur.

Last March, 1,760 tons of spent fuel were stored in the six pools, 84 percent of capacity, according to Tokyo Electric.

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