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Reactor Core May Be Breached at Damaged Fukushima Plant

Nuclear Crew Returns to Reactor
A Tokyo Electric Power Co. employee records reactor data in a control room, lit only by flashlights due to a power outage, for the No. 1 and No. 2 reactors at the Fukushima Dai-Ichi Nuclear Power Station on March 23, 2011. Photo: Japan's Nuclear and Industrial Safety Agency via Kyodo

Japan’s nuclear regulator said one reactor core at the quake-damaged Fukushima Dai-Ichi power plant may be cracked and leaking radiation.

“It’s very possible that there has been some kind of leak at the No. 3 reactor,” Hidehiko Nishiyama, a spokesman at the Japan Nuclear and Industrial Safety Agency, said in Tokyo today. While radioactive water at the unit most likely escaped from the reactor core, it also could have originated from spent fuel pools stored atop the reactor, he said.

Repair work at the site of the worst nuclear disaster since Chernobyl has been plagued by explosions, fires and leaks of toxic material. Prime Minister Naoto Kan told a press conference that efforts to bring the reactor under control haven’t yet reached a stage where the government can let down its guard.

“Even if there has been encouraging news such as getting some power back to the site, the installation remains in an extremely precarious and very serious situation that has not yet been stabilized,” Thomas Houdre, head of reactors at France’s nuclear safety agency, told reporters in Paris.

Workers using fire engines have streamed 4,000 tons of water on the No. 3 reactor, five times more than any of the other five units, according to the government.

Radiation Burns

Two plant workers were hospitalized yesterday with radiation burns after stepping in the water, which was found to have radiation levels 10,000 times higher than water used in reactor cooling, Nishiyama said earlier today.

Tokyo Electric Power Co., the plant operator, said it found eight different radioactive materials in the water of the turbine building basement, where the men were attempting to connect a power cable. The materials are made through a process of fission, and include cobalt and molybdenum-99, a spokesman for the power utility said.

Tokyo Electric plans to drain radioactive water from the turbine building of the No. 3 unit where the accident occurred, spokesman Osamu Yokokura said. It has yet to determine how and when to do this, he said.

“The water that is coming out of that area is much higher in terms of radiation and this is obviously complicating the clean up,” said Tony Roulstone, an atomic engineer who directs the University of Cambridge’s master’s program in nuclear energy. “If it’s leaking out then they have to figure out some way to contain this water.”

The March 11 quake, Japan’s biggest ever, left the plant without power needed to cool nuclear fuel rods. Japan today advised more people living close to the nuclear plant to evacuate because basic goods are in short supply, while assuring them that radiation levels haven’t risen.

Evacuation Zone

The recommendation applies to residents living between 20 kilometers (12 miles) and 30 kilometers from the Fukushima Dai-Ichi facility, which was damaged by the March 11 earthquake and tsunami. The government previously evacuated everyone living closer to the plant.

“It’s becoming difficult for people to live a normal life and we can’t rule out the possibility of broadening the mandatory evacuation if radiation levels rise,” Chief Cabinet Secretary Yukio Edano told reporters in Tokyo today. “We will make maximum efforts to ensure a smooth, voluntary withdrawal by providing transportation and shelter.”

The death toll from the quake and tsunami climbed to 10,066 as of 3 p.m. with 17,443 people missing, according to the National Police Agency in Tokyo.

The spread of radiation to food and water supplies prompted bulk-buying of bottled drinks even as the government said the health threat remained minimal.

Exceed Limits

Radioactive cesium above the government limit was found on komatsuna, a leafy vegetable known as Japanese mustard spinach, harvested in Tokyo’s Edogawa ward, authorities said yesterday. That indicates radioactive elements have spread 220 kilometers (135 miles) south of the Fukushima plant.

A sample collected on March 20 from an open field contained 890 becquerels per kilogram of radioactive cesium, Japan’s Health Ministry said on its web site. The safety limit is 500 becquerels. Consuming 1 kilogram of komatsuna would yield a radiation exposure of 0.01 millisieverts, or a third of exposure to cosmic rays on a flight from New York to Los Angeles.

Cancer Risk

Exposure to radiation from cesium-137 increases the risk of cancer, and high doses can cause serious burns and death, according to the U.S. Environmental Protection Agency.

Tokyo authorities already were handing out bottled water after determining that tap water may be unsafe for babies. Radioactive iodine in tap water was above the government limit for infants today in Utsunomiya, a city about 80 miles southwest of the plant, Kyodo News reported.

Changing weather systems will drive radiation from the Fukushima plant over the Pacific Ocean today, Austria’s Meteorological and Geophysics Center reported, citing data from the United Nations nuclear-test ban treaty organization

Wind will carry the radionuclides for a “short while” inland, the center said on its website. Reactors at Fukushima may have released as much as 20 percent of the radioactive iodine and up to 60 percent of the radioactive cesium that resulted from the Chernobyl meltdown in 1986, according to the report yesterday.

The maximum radiation reading reported so far at the nuclear plant is 500 millisieverts per hour, meaning a worker in the vicinity would receive the maximum-allowed dose in 30 minutes. Tokyo Electric said 17 workers had received more than 100 millisieverts of radiation since the crisis started.

U.S. Navy ships carrying out Japan relief efforts have been ordered to stay outside a 100-nautical-mile radius of the Fukushima plant. Tokyo is 135 miles south of Dai-Ichi. The nuclear-powered aircraft carrier USS George Washington this week left port at Yokosuka, 175 miles south from the plant, to avoid getting residual traces of radiation on the vessel, which could trigger alarms and require extensive cleanup.

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