Radiation levels that can prove fatal were detected outside reactor buildings at Japan’s Fukushima Dai-Ichi plant, signaling a partial fuel meltdown and complicating efforts to contain the worst nuclear disaster since Chernobyl.
Water in a tunnel outside the No. 2 reactor had radiation levels exceeding 1 sievert an hour, a spokesman for plant operator Tokyo Electric Power Co. told reporters yesterday. Exposure to that dose for 30 minutes would trigger nausea and four hours might lead to death within two months, according to the U.S. Environmental Protection Agency.
A partial meltdown of fuel rods in the No. 2 reactor probably caused a jump in the readings, Japan Chief Cabinet Secretary Yukio Edano said. Preventing the contaminated water from leaking into the ground or air is key to containing the spread of radiation beyond the plant.
“There’s not much good news right now,” said Gennady Pshakin, a former official with the International Atomic Energy Agency. Questions of how much fuel will leak, what isotopes will be carried and how quickly they will settle mean “it’s becoming less predictable.”
Rubber-lined tunnels outside reactor buildings 1, 2 and 3 are almost full of water, a Tokyo Electric official said in a webcast briefing today. The trenches, which aren’t connected to the sea, range in depth from 16 meters (52 feet) to almost 22 meters, he said.
A magnitude-9 earthquake and ensuing tsunami on March 11 knocked out power at the plant, forcing Tokyo Electric to dump thousands of tons of seawater on the complex as a stopgap cooling measure.
The number of dead and missing from the earthquake and tsunami had reached 28,343 as of 9 p.m. yesterday. About 200,000 households in northeast Japan remain without power and more than 350,000 have no gas, the government said. There are 242,882 refugees living in 2,045 shelters, the National Police Agency said.
Residents evacuated from a 20-kilometer (12-mile) radius of the plant shouldn’t return home yet, Edano said.
Elevated radiation levels have been detected in crops grown near the stricken plant as well as the water supply in Tokyo, 220 kilometers to the south, and other regions.
Plutonium-239, a byproduct of fission used in nuclear weapons, was found in soil samples taken on the plant site March 21 and March 22, Tokyo Electric said in a statement today. Two of the five samples contained more plutonium than known to have been deposited by atmospheric nuclear-bomb fallout and probably came from the damaged plant, according to the statement.
The amount found shouldn’t be enough to affect human health, Sakae Muto, a Tokyo Electric vice president, said at a press conference yesterday.
“The high radiation levels seem to have come from fuel rods that partially melted down and came into contact with water used to cool the reactor,” Edano said at a briefing in Tokyo, citing a draft report from Japan’s Nuclear Safety Commission. “We’re trying to contain the whole situation while preventing the health impact from spreading.”
Ever-higher radiation emissions at Dai-Ichi and evidence water has leaked out of the No. 2 reactor’s containment vessel comes after success last week in restoring power to control rooms and injecting fresh water into the reactor pressure vessels to keep temperatures from rising.
Tokyo Electric slumped 18 percent to 696 yen on the Tokyo Stock Exchange yesterday, the lowest close since February 1977. The Japanese government is considering nationalizing the company, buying a majority of its shares so it can pay damages from the accident, Yomiuri newspaper reported, citing multiple anonymous government officials.
Plutonium was part of the fuel mix in reactor No. 3. Used fuel rods from other reactors may also have been a source of the material, Edwin Lyman, a radiological specialist for the watchdog group Union of Concerned Scientists, said on a conference call with reporters. Plutonium inhalation causes lung, liver and bone cancer, according to the U.S. National Institutes of Health.
Tokyo Electric needs to drain water in four reactor turbine buildings to determine where the radiation came from and assess damage to the fuel rods, a company official told reporters yesterday.
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