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sábado, 26 de março de 2011

Japan struggles to cool nuclear reactors



Efforts to stabilise stricken Fukushima nuclear plant are being hampered by leaking radioactive water.
Last Modified: 26 Mar 2011 06:44


Engineers struggle to pump out puddles of radioactive water as radiation levels soar to 10,000 times above safety limit

Battle to stabilise Japan''s stricken Fukushima Daiichi nuclear plant are being hampered by radioactive water that is apparently leaking from the reactors, delaying efforts to cool reactors to safe levels.

Engineers have been frantically attempting to pump out puddles of radioactive water at the earthquake-crippled complex on Saturday, which exposed three workers wading through the water to so much radioactivity that they had to be hospitalised for radiation burns.

Al Jazeera''s Wayne Hay, reporting from the capital Tokyo, said efforts to cool "hot" fuel rods are facing problems.

"Officials are now concerned that the salt from the sea water may be encrusting on the fuel rods themselves, therefore rendering the cooling situation useless. So they are now changing their tactics and pumping fresh water into those reactors," he said.

US naval barges loaded with fresh water are being rushed toward the overheated nuclear plant.

Yoshimi Kitazawa, Japan's defense minister, said the US was sending the load to the nearby Onahama Bay and would begin water injections early next week.

Death toll crosses 10,000

The escalation in the nuclear plant crisis came as the death toll from the quake and tsunami passed 10,000, with 17,000 still reported missing.

Across the battered northeast coast, hundreds of thousands of people whose homes were destroyed still have no power, no hot meals and, in many cases, no showers for two weeks.

"Some positive trends are continuing but there remain areas of uncertainty that are of serious concern"

Graham Andrew,
IAEA official

More than a quarter of a million people are in shelters. Exhausted rescuers are still sifting through the wreckage of towns and villages, retrieving bodies.

Despite such a shocking toll, much attention since the disaster has been on the possibility of a catastrophic meltdown at Fukushima.

Radioactive water has been found in buildings of three of the six reactors at the power complex 240km north of Tokyo. On Thursday, three workers sustained burns at reactor No. 3 after being exposed to radiation levels 10,000 times higher than usually found in a reactor.

"Bailing out accumulated water from the turbine housing units before radiation levels rise further is becoming very important," Hidehiko Nishiyama, a senior official from Japan''s Nuclear and Industrial Safety Agency, said.

"We are working out ways of safely bailing out the water so that it does not get out into the environment, and we are making preparations," Nishiyama said.

He initially said the high radiation reading meant there could be damage to the reactor, but he later said it could be from venting operations to release pressure or water leakage from pipes or valves.

"There is no data suggesting a crack," he said.

Nuclear watchdog the International Atomic Energy Agency (IAEA) said on Friday there had not been much change in the crisis over the previous 24 hours.

"Some positive trends are continuing but there remain areas of uncertainty that are of serious concern," Graham Andrew, an agency official, said in Vienna, adding the high radiation could be coming from steam.

''Irresponsible instruction''

More than 700 engineers have been working in shifts to stabilise the plant and work has been advancing to restart water pumps to cool their fuel rods.

Two of the plant''s reactors are now seen as safe but the other four are volatile, occasionally emitting steam and smoke. However, the nuclear safety agency said on Saturday that temperature and pressure in all reactors had stabilised.

Impact on Japan''s food industry

Vegetable and milk shipments from near the stricken plant have been stopped, and Tokyo''s residents were told this week not to give tap water to babies after contamination from rain put radiation at twice the safety level.
South Korea, Taiwan, Singapore, Australia, the United States and Hong Kong are restricting food and milk imports from the zone.
Other nations are screening Japanese food, and German shipping lines are simply avoiding the country.

When Tokyo Electric Power (Tepco) restored power to the plant late last week, some thought the crisis would soon be over. But two weeks after the earthquake, lingering high levels of radiation from the damaged reactors has kept hampering workers'' progress.

Naoto Kan, the Japanese prime minister, said on Friday the situation at Fukushima was "nowhere near" being resolved.

"We are making efforts to prevent it from getting worse, but I feel we cannot become complacent," Kan said. "We must continue to be on our guard."

In Tokyo, a metropolis of 13 million people, a Reuters reading on Saturday morning showed ambient radiation of 0.22 microsieverts per hour, about six times normal for the city.

However, this was well within the global average of naturally occurring background radiation of 0.17-0.39 microsieverts per hour, a range given by the World Nuclear Association.

Meanwhile, the Japanese government has prodded tens of thousands of people living in a 20km-30km zone beyond the stricken complex to leave, but insisted it was not widening a 20km evacuation zone.

Opposition politicians and local officials were severly critical of the move, especially since it came after the government advised residents there to stay indoors.

"So far they have only given the irresponsible instruction to stay inside; the decision-making is slow," conservative Sankei newspaper quoted Toshikazu Ide, the mayor of a village inside the 20-30 km area, as saying.

Yukio Edano, the chief cabinet secretary, has said the residents should move because it was difficult to get supplies to the area, and not because of elevated radiation.

An official at the science ministry however confirmed that daily radiation levels in an area 30km northwest of the plant had exceeded the annual limit.







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