Tue, Mar 22, 2011 - Page 9 News List

Nuclear power’s future depends on the ‘Fukushima 50’

A team of about 300 workers, known as the ‘Fukushima 50’ because they work in shifts of 50-strong groups, have captured the hearts of the Japanese as they toil inside the wrecked Fukushima Dai-ichi nuclear power plant

By Robin McKie  /  The Observer, LONDON

Illustration: Yusha

Exhausted engineers attached a power cable to the outside of Japan’s tsunami-crippled nuclear plant on Saturday. The operation raised hopes that it may be possible to restart the pumping of water into the plant’s stricken reactors and cool down its overheated fuel rods before there are more fires and explosions.

“We have connected the external transmission line with the receiving point of the plant and confirmed that electricity can be supplied,” a spokesman for the plant’s operator, Tokyo Electric Power Co, said in a statement.

However, officials said further cabling would have to be completed before they made an attempt to restart the water pumps at the Fukushima Dai-ichi nuclear power plant.

It was also reported that health workers had detected radiation levels above safety limits in milk and spinach from farms in Fukushima and in neighboring Ibaraki Prefecture, although it was claimed they represented no risk to human health. Officials have asked people living near the plant to follow basic safety advice when going outside — drive, don’t walk; wear a mask; wear long sleeves; don’t go out in the rain.

Radiation levels in Tokyo were also said to be within safe limits. Nevertheless, the city has seen an exodus of tourists, expatriates and many Japanese, who fear a blast of radioactive material from Fukushima.

At the nuclear plant on Saturday, firefighters continued to spray water to cool the dangerously overheated fuel rods in order to keep cores in its reactors from overheating and melting.

The UN’s atomic agency said conditions at the plant remained grave, but not deteriorating badly, following Japan’s decision on Friday to raise the severity rating of the nuclear crisis from level four to level five on the seven-level international scale. It put the Fukushima fires on a par with the Three Mile Island accident in Pennsylvania in the US in 1979.

The explosion at Chernobyl in 1986 — which sent a plume of radioactive material into the skies 25 years ago — is the only incident to have reached level seven.

Fires and explosions occurred at four of the six reactors at Fukushima last week after the magnitude 9.0 earthquake and the ensuing tsunami that hit Japan on March 11. The earthquake triggered an automatic shutdown of the three reactors that were in operation. The tsunami then damaged diesel generators that were providing back-up power for the pumps driving coolant through the reactors.

As a result, heat could no longer be pumped away and temperatures inside the reactors’ cores began to rise, eventually setting off a series of chemical fires.

“Hollow rods made of zirconium hold each reactor’s uranium fuel pellets in place,” said Andrew Sherry, director of the Dalton Nuclear Institute in Manchester, England. “When temperatures rise too much, that zirconium starts to react with the reactor’s water. This chemical reaction raises temperatures even further. Hydrogen is also produced. When this hydrogen exploded, it destroyed the buildings that act as each reactor’s outer protective shell.”

The explosions also damaged two storage tanks in which fuel rods — still hot because of the radioactive material inside them — were being stored in water. Water levels dropped, exposing fuel rods and triggering further chemical reactions between zirconium fuel cladding and the steam that had begun to build up. These set off fires in storage tanks at reactors three and four.

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