The New York Times The New York Times National September 8, 2003
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Safety Problem at Nuclear Plants Is Cited

By MATTHEW L. WALD

WASHINGTON, Sept. 7 The emergency cooling systems that are meant to protect nuclear reactors from melting down in case of a ruptured water pipe could fail after a few minutes of use at most reactors, according to a nuclear watchdog group that is citing a government study to argue that the problem makes a catastrophe at one power plant in New York 100 times more likely.

The group, the Union of Concerned Scientists, and a New York environmental organization, Riverkeeper, plan to petition the Nuclear Regulatory Commission this week to ask that the two Indian Point reactors in Buchanan, N.Y., on the east bank of the Hudson River, should be shut until corrections are made. The problem, they argue, is that leaking water or steam would scour off pipe insulation, paint and other materials, forming debris that would clog the coolant pumps.

The Nuclear Regulatory Commission recognized the possibility years ago, and in September 1996 classified it as a serious problem, but does not anticipate that corrective action will be completed until early 2007. A commission official said, however, that the problem is complicated to solve and need not be fixed immediately because the accident that would require use of the safety system was unlikely in the first place.

David Lochbaum, a nuclear engineer with the Union of Concerned Scientists, contended that the emergency core cooling system "is virtually certain to fail at some plants."

"Right now you're relying on a pipe not breaking," he said.

According to Mr. Lochbaum and to data from the Nuclear Regulatory Commission, the problem involves 69 plants of a design called pressurized water reactors, in which the water that is used to carry off the useful heat, and to keep the fuel from over-heating, is kept at a pressure of about 2,200 pounds per square inch. If a pipe breaks and the pressure is released, the water would boil into steam because it is heated to more than 500 degrees. The steam could not cool the fuel, and the fuel would melt.

So the plants are equipped with an automatic emergency core cooling system. Drawing water from a tank outside the reactor dome, the system can dump thousands of gallons a minute into the reactor, making up for even a large leak.

In this design, water from a broken pipe would flow into the reactor basement. The outdoor tank typically holds 125,000 to 300,000 gallons, and when it was nearly empty, the system would start drawing water from the basement instead. The problem is that if the water picks up debris along the way, that debris could clog the screens over the pipes that lead back to the emergency pumps.

At the request of the commission, the Los Alamos National Laboratory studied the 69 plants, and found that for some, the risk of core damage was multiplied 100 times because of the debris problem. It ranked the plants but did not name them; Mr. Lochbaum's group used various detailed characteristics included in the report to determine which plant was which, and discovered that the Indian Point reactors were both in the worst five.

The plants' owner, Entergy, told the N.R.C. in August, in response to a letter sent by the commission to all plants, that it had analyzed the material available to become debris, including "failed paints," and would train its operators in ways to manage the problem, including pumping water in more slowly.

A spokesman for Indian Point, Jim Steets, said that he had not seen the petition, but that "the N.R.C. has attached some level of urgency, which we're complying with."

At the N.R.C., Sunil Weerakkody, the section chief for fire protection and special studies, said that in decades of nuclear plant operation, the emergency core cooling system had been used only eight times, and that no accident had reached the stages at which pumping from the basement was required.

"Our best knowledge says we won't even need that function," Mr. Weerakkody said.

The commission recognized the problem at Davis-Besse, the reactor near Toledo, Ohio, where operators discovered that the vessel head had been eaten away by acid, nearly all the way through. Had the vessel ruptured, said Mr. Lochbaum and others, it would have blown insulation off the head and into the basement and the screens. The commission required the plant's owners to fix the problem before it would consider giving permission to restart.

In an interview, Mr. Lochbaum pointed to that example, and to a reactor in Michigan that was ordered to shut a few years ago because it was found to have an unusually high potential for debris, as precedents for the order he is seeking.

Studies for the N.R.C. found that Indian Point 2 could exhaust the water in the external tank in less than 23 minutes, and unit 3 in less than 14, he said; Davis-Besse, in contrast, would have taken 35 minutes, and was more likely to survive the debris problem in many kinds of pipe breaks, according to government data.

But Mr. Weerakkody said the Los Alamos study was only a quick cut at the problem, to determine whether more work was needed, and had used various "conservative" assumptions that might be too pessimistic.

"When you remove some of those conservatisms, the risk number drops drastically," he said.




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