The analysis of spent fuel pool meltdowns also states that millions of people within such a 500-mile zone might have to be evacuated for periods ranging from 30 days to one year and that people living within 10 miles of a nuclear plant might never be able to return to their homes.

It also cites the potential for "prompt fatalities" from radiation poisoning that would occur in areas close to a plant site, where many radioactive particles would be expected to fall.

The extent of possible radiation damage described in the NRC documents is far more severe than anything that federal officials have disclosed in public forums or written statements.

The agency's assessments are contained in a special report prepared by experts within the NRC and the Sandia National Laboratories in Albuquerque, in October 2000 that was designated as an official NRC planning regulation in February 2001. A copy of the report was obtained by The Journal News.

The study has been criticized by nuclear industry representatives who say it reflects a worst-case scenario based on unrealistic assumptions and ignores the effectiveness of plant safety systems.

Sandia laboratories maintains a computer simulation system that enables the NRC to predict the possible spread of radiation from any of the nation's 103 nuclear plants based on their location, geography and area population densities and the prevailing or seasonal weather patterns within hundreds of miles of the sites.

Damage assessments — including the number of prompt fatalities, long-term cancers, affected population centers and the duration of evacuations for specific areas — can then be estimated for any region of the country. Within 500 miles of Indian Point nuclear plant in Buchanan, N.Y., there are nearly 82 million people living in the United States and 11 million in Canada.

The report provides the basis for any future NRC regulations on evacuation needs, safety requirements and insurance and compares the possible damage caused by a spent fuel pool meltdown with that of a meltdown in a fully operational nuclear reactor. It was developed to show the NRC what types of problems could occur in spent fuel pools when nuclear plants are shut down, at which point no new fuel rods would be placed in the pools, and how long they might pose a danger from a meltdown and fire.

The potential spread of contamination cited in the report far exceeds the 10-mile zone the nation's nuclear plants currently utilize in developing emergency evacuation plans. NRC officials said the evacuation plans are intended to deal only with short-term radiation poisoning, which is not likely to occur outside the 10-mile zone.

The report was pulled from the NRC's public database following the Sept. 11, 2001, terrorist attacks because, agency spokesman Neil Sheehan said, "if a terrorist decided to attack any plant in the U.S., not just Indian Point, that is information about what fatalities it could cause, and the exact knowledge of that could be very advantageous to them."

The information was returned to the database in April, however, because it is an official regulation governing spent fuel pool operations and must be accessible to plant operators.

The report states that analysts did not base their findings on "events due to sabotage. No established method exists for estimating the likelihood of a sabotage event. Nor is there a method for analyzing the effect of security provisions on that likelihood." Instead, analysts examined various accident scenarios, ranging from worker mishaps to plane crashes into a spent fuel pool building. The report concluded that while the probability of such accidents is extremely low, the effects of a meltdown would be enormous.

The protection and disposition of spent fuel is a national problem. Every two years, plants replace a third of the nearly 100 tons of fuel used in their reactors with new fuel. The spent fuel at Indian Point 2 and 3 is stored in pools of water 40 feet deep. The federal government is developing a permanent repository for spent fuel under Yucca Mountain in Nevada, which is expected to open around 2010.

The uranium fuel used in reactors has a zirconium coating that permits nuclear reactions to occur but helps prevent the fuel from literally burning up and being dispersed into the atmosphere. The cooling water in the reactor and the spent fuel pools keep the temperature low enough that there is no danger of fire.

The internal heat of the nuclear fuel drops over time, and, after about five years, spent fuel rods can be removed from the pools and stored in dry casks that are air cooled. It had been thought by plant operators that there was little chance of a zirconium fire in fuel that was out of a reactor for at least five years. As a result, nuclear plant operators were not required to have emergency evacuation plans for events involving spent fuel pools, even though the pools hold hundreds of tons of radioactive material, far more than is used in the reactors. The NRC was considering industry requests to reduce insurance requirements for pools containing only older fuel.

But the report states that a zirconium fire still can occur 30 years after fuel rods are removed from a reactor, as significant an accident as a worst-case reactor-core meltdown, and that the danger of cancer-causing, radioactive contamination would not significantly decrease at least for that long.

The report assesses the effects of a fuel fire that would be triggered if water were completely or partially drained from spent fuel pools. Cesium-137, which is among the radioactive particles that could be released into the atmosphere, is the primary cause of long-term cancers, according to the NRC study. In that regard, cesium-137 is more significant than radioactive iodine.

Current evacuation plans approved by the NRC for Indian Point are based on the premise that it would take several hours or days to reach the stage where a fuel fire would release radiation into the atmosphere. The agency's 2000 report states that a zirconium fire could erupt and begin releasing radiation within two to four hours after water was completely or partially drained from a spent fuel pool.

Charles Tinkler, a senior adviser in the NRC's office of research and co-author of the report's section on meltdown consequences, said the NRC studied the effects of contamination at Chernobyl in Ukraine, which suffered a catastrophic meltdown in 1986. There is a permanent exclusion zone extending about 35 miles around the site of the former reactor.

Tom Hinton, a radiation ecologist at the University of Georgia's Savannah River Ecology Lab, said the extent of contamination from a meltdown depends on how high the contaminants are pushed into the atmosphere, local weather conditions and the type of radioactive isotopes involved.

"At Chernobyl," he said, "there was contamination spread around the world, though the majority of it was within 300 kilometers or so. Contamination depends on local weather conditions, specifically rain. If a (radiation) cloud passes over you and it is not raining, you will not get as much contamination as if it were raining. Rain scavenges contaminants out of the air and deposits them locally. That is the reason for many hot spots that occurred around Europe after the Chernobyl accident."

Some radiological isotopes, such as plutonium, will stay where they land, Hinton said, while others travel through the environment contaminating plants and waterways.

Officials in the four counties around Indian Point conducted a mock evacuation drill of the 10-mile zone on Sept. 24 under the auspices of the NRC and Federal Emergency Management Agency, which certifies emergency evacuation plans. Officials at the time said radiation leaking from the reactor would dissipate after about five miles and the evacuation plans would protect the public from any harmful radiation.

David Lochbaum, a nuclear safety analyst for the Union of Concerned Scientists in Washington, D.C., said that the argument that radiation couldn't go more than five miles or so "was never accurate."