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Friday 18 March 2011

Japan struggles to cool reactors, spent fuel at damaged plant

Tokyo (CNN) -- Japan turned helicopters, fire trucks and police water cannons on the No. 3 reactor at the quake-ravaged Fukushima Daiichi nuclear power plant and the pool housing its spent fuel Thursday in its latest attempt to stave off a nuclear disaster.

Military helicopters began dumping water on the reactor Thursday morning, with police and fire trucks opening up after 7 p.m. (6 a.m. ET). Japan's Defense Ministry said the first effort lasted 40 minutes, and the Tokyo Electric Power Company said the efforts would continue throughout the night in order to keep the reactor and its adjacent spent fuel pool from overheating.

"In order to cool the spent fuel storage pool, we have carried out water drop operations and the spraying of water from the ground," TEPCO officials said at a Thursday night news conference. "This needs to continue in several ways. Therefore, we will continue to ask for cooperation of the involved people so we can carry out continuously. The helicopter water dumping operation is something we have asked (the) government to provide us help with, and also the spraying of water."

Friday's earthquake and tsunami caused damage at four of the six reactors at the Fukushima Daiichi plant, located on the northern coast of the Japanese island of Honshu. TEPCO also was attempting to restore power to the facility, but those efforts had not been completed by nightfall Thursday, the company said. Restoring power would help get the plant's pumping systems going again, to try to get water to the pool.

Helicopters made four passes in about a 20-minute span Thursday morning, dropping 7.5 tons of seawater each time on the facility's No. 3 reactor in order to cool its overheated fuel pool. Video of the operation aired on NHK showed that only one of the loads appeared to drop directly on the building. Gusty winds dissipated much of the water carried by the other three helicopters. Experts believe that boiling steam rising from that pool, which contains at least partially exposed fuel rods, may be releasing radiation into the atmosphere.

Rebecca Johnson, founder of the London-based Acronym Institute for Disarmament Diplomacy, told CNN that Japanese engineers are "flying by the seat of their pants now." "Everything they try goes wrong. They're focusing on reactors, then spent fuel becomes damaged," Johnson said. "They've just got to get water in there, keep the water pumping."

And nuclear engineer Arnie Gundersen told CNN's "American Morning" that the effort will likely need to be sustained "for months, if not years."

"What's pushing the firemen back is the radiation that's coming from the spent fuel pool," he said. If the spent fuel rods in that pool are uncovered, "There's an awful lot of gamma rays flooding that site, forcing the workers to say further away."

Japanese Defense Minister Toshimi Kitazawa, in conjunction with Prime Minister Naoto Kan, said he decided early Thursday to address the crisis from the air and ground despite concerns about exposing workers to radiation.

"We could not delay the mission any further, therefore we decided to execute it," Kitazawa told reporters.

Radiation levels at the plant remained high Thursday evening, but had dropped sharply from the morning. At 4 p.m. (3 a.m. ET), the Japanese Nuclear and Industrial Safety Agency reported exposures of 1.6 millisieverts per hour, down from the nearly 3.8 millisieverts per hour TEPCO reported at 9:30 a.m. A typical resident of a developed country receives about 3 millisieverts per year.

"The radiation levels of individual workers are being properly managed by limiting their time in or close to the reactors," Hidehiko Nishiyama, NISA's deputy director-general, told reporters. Out of 18 workers tested Thursday morning, 17 tested normal, and the one who received a higher dose of radiation required no medical treatment, Nishiyama said.

The increased focus on the No. 3 reactor came after a stark U.S. warning about the fuel pool in the No. 4 reactor. Gregory Jaczko, the head of the U.S. Nuclear Regulatory Commission, told a congressional committee that there was "no water" in the No. 4 pool, resulting in the emission of "extremely high" levels of radiation.

But Japanese authorities disputed Jaczko's assertion, citing information gathered from a helicopter flight over the plant. A TEPCO official said Thursday that there was some water in the No. 3 spent fuel pool, "But we do not know how much water."

Nishiyama acknowledged that some data from the Daiichi plant may not be reliable as the quake knocked down power on site, rendering measurement equipment unstable. He was quick to defend how the government has handled information on the nuclear plant.

And the Japanese government came under fire Thursday with the release of a WikiLeaks cable attributed to the U.S. State Department. The document noted that a Japanese legislator, Taro Kono, had accused Japan's Ministry of Economy, Trade and Industry of "covering up nuclear accidents, and obscuring the true costs and problems associated with the nuclear industry."

A Japanese government spokesman, Noriyuki Shikata, warded off fears of an imminent meltdown, telling CNN Thursday, "We have not seen a major breach of containment" at any of the plant's troubled nuclear reactors.

A meltdown occurs when nuclear fuel rods cannot be cooled and the nuclear core melts. In the worst-case scenario, the fuel can spill out of the damaged containment unit and spread radioactivity through the air and water.

That, public health officials say, can cause both immediate and long-term health problems, including radiation poisoning and cancer.

Tests in Fukushima city, 80 kilometers (50 miles) away, found radiation measuring 12.5 microsieverts per hour -- well above the average reading of 0.04, but still well below that considered harmful to humans.

Small, and for now, harmless amounts of iodine -- a potential byproduct of a nuclear meltdown -- were found in the city's water.

Citing Fukushima Prefecture officials, Kyodo News reported Thursday that about 10,000 people were screened for radiation exposure the previous day at evacuation centers and medical offices.

About 200,000 people living within a 20-kilometer (12-mile) radius of the plant have been evacuated; those living 20 to 30 kilometers from the site have been told to remain inside. Authorities also have banned flights over the area.

Koichi Shiga described the town of Minamisoma,25 kilometers from the plant and site of the Hotel Iseya that he owns, as ghostly quiet with most all shops closed and empty streets. Electricity and water were still flowing, though evacuation efforts have been hampered by a paucity of gasoline.

"People have not evacuated, they are staying at home," Shiga told CNN. "There was a ration of 10 liters of gas, and I saw a long line of people."

Several countries, including the United States, have called for a broader range, urging their citizens in Japan to evacuate or at least stay indoors if they live within 80 kilometers of the Fukushima Daiichi plant.

One positive development is that winds have been blowing from the northwest, helping push emitted radiation off to sea. Still, at least 20 people have fallen ill due to possible radiation contamination, in addition to 19 injured and two missing at the plant, the International Atomic Energy Agency reported.

1 comment:

Prasad said...

We should learn lessons from the Japan's Nuclear Disaster.