WASHINGTON — The nuclear power accidents at Fukushima this spring and at Chernobyl 25 years ago Tuesday show that radiation releases can endanger people and contaminate land many miles beyond evacuation zones.
The advocacy group Physicians for Nuclear Responsibility, which opposes nuclear power, said Tuesday that the U.S. 10-mile evacuation plan was inadequate and should be extended to 50 miles. One-third of the U.S. population lives within 50 miles of nuclear power plants.
In Japan, much of the radiation plume went over the Pacific Ocean in the early weeks after the March 11 earthquake and tsunami, but wind's and rain drove some of it onto land. The release of radioactive materials raises the risk of cancer, especially for children, who are more vulnerable than adults, Ira Helfand, a member of Physicians for Social Responsibility, said at a news conference.
The Chernobyl accident in 1986 in the former Soviet Union contaminated 58,000 square miles of land, stretching as far as 300 miles north of the plant, the International Atomic Energy Agency reported. Unlike the Fukushima plants or U.S. plants, Chernobyl had no concrete and steel structure to contain accidental releases.
The Fukushima accident spread fallout beyond the government's initial 12-mile evacuation zone as a result of explosions. At Fukushima and in the U.S., the pools where spent radioactive fuel is stored aren't inside the containment structure.
Measurements of soil samples as far as 30 miles from the Fukushima plant have detected cesium-137, a long-lived radioactive element that human bodies can absorb. It was measured at levels that were above the cutoff that was used to determine the permanent exclusion zone around Chernobyl, said Andrew Kanter, the president-elect of Physicians for Social Responsibility.
Other measurements, at playgrounds outside the exclusion zone, showed levels equivalent to the limit of radiation permitted for an adult nuclear-plant worker. That amount would mean that one in 200 children would get cancer as a direct result of the exposure, Helfand said.
The U.S. nuclear industry said American experts had determined that it was highly unlikely that evacuation would be necessary beyond 10 miles, even in a worst-case accident. The U.S. observes a 50-mile zone to limit exposure to contaminated water, milk and food, and local officials could expand an evacuation order if they thought it necessary, Steve Kerekes, a spokesman for the industry's Nuclear Energy Institute, said in an email.
In Japan, work is still under way to cool the reactor cores and spent-fuel pools to stop further releases of airborne radioactive materials.
"Once they decide how to put the reactors into some sort of safe storage mode, they will need to deal with the contamination in and around the plants," said Kathryn Higley, a professor of radiation health physics at Oregon State University.
When the cleanup phase begins, workers probably will use shovels to remove contaminated soil for disposal in a nuclear landfill, said Lake Barrett, a former official with the Department of Energy and the Nuclear Regulatory Commission who was involved in the cleanup of Three Mile Island in Pennsylvania after a nuclear accident there in 1979.
Some of the land that's cleaned up in Japan might end up being good enough for a factory or a parking lot, but not for a garden or a pasture, he said in an interview.
"It took 10 years for Three Mile Island," Barrett said, "and that was simple compared to what they've got."
Physicians for Social Responsibility says the risks of nuclear power to public health and of nuclear proliferation are too high.
The group reported Tuesday that it had used a computer simulation to model what would happen in the case of a complete meltdown and massive release of radiation from a power plant in a metropolitan area. It studied Braidwood, outside Chicago. The projection was that 20,000 people might get lethal doses, and thousands of doctors and firefighters would be unable to work because the radiation levels would be so high.
Scientists still debate how many deaths were due to Chernobyl's radiation releases. A U.S. National Research Council report concluded that there's no safe level of radiation and cancer risks rise with increased exposure.