BY TODD B. BATES AND NICHOLAS CLUNN GANNETT - NEW JERSEY

If there were a major reactor accident at the Oyster Creek nuclear plant, chances are its most critical radiation barrier would fail.

That means radiation could spread into the environment, schools and thousands of homes.

This is not speculation from an anti-nuclear group or a disgruntled employee.

The chilling possibility comes from a detailed evaluation of Oyster Creek by its owner and operator.

Oyster Creek's steel and concrete radiation containment system has a 74 percent chance of failing if the reactor core melts or fuel is seriously damaged from an accident, according to a risk analysis by AmerGen Energy Co., which runs the plant. The details are in the plant's 2,400-page relicensing application.

Despite this known risk, Oyster Creek's owner wants to run the plant for 20 more years beyond the end of its current 40-year license in 2009.

Such a high probability of containment failure is common among the 103 nuclear reactors in the United States, according to documents and studies from the U.S. Nuclear Regulatory Commission. The possible failure rate ranged from 1 percent to 99 percent, according to a nuclear engineer who has seen an NRC database that is no longer publicly available.

Although getting to the point of core damage at Oyster Creek has astronomically low odds — about 1 chance in 95,000 per year — once that threshold is crossed, the final barrier will be little match for the heat, steam and radiation produced during a catastrophic accident.

"The good news is that a lot of effort is undertaken to reduce the likelihood of an accident," said David Lochbaum, director of the Nuclear Safety Project for the Union of Concerned Scientists, a nonprofit alliance of citizens and scientists.

"The bad news is that if that date arrives," the containment system, whose sole function is to protect the public, is "not likely to work," he said.

If you were to slice the plant from top to bottom, Oyster Creek's containment system would look like an enormous upside-down light bulb balanced on a doughnut.

The principle is similar to that of a thermos bottle: If the inside lining of the container breaks, the liquid would remain trapped within the bottle's steel outer shell.

Oyster Creek's containment system, which surrounds the reactor and its 105 tons of nuclear fuel, is designed to condense steam and cool the reactor in an emergency.

But if the reactor core is damaged, the 74 percent chance of failure means that at least some radiation would escape within hours or days of the accident, according to Oyster Creek's application for relicensing, a plant spokesman and NRC officials.

"I'm horrified because the mantra of Oyster Creek and the nuclear industry is that they're safe," said Jeffrey Brown, a 63-year-old Brick resident and a member of Grandmothers, Mothers and More for Energy Safety, an Oyster Creek opposition group. "At what point do people say that Oyster Creek is not worth the risk?"

Engineers not affiliated with the NRC or the plant should be allowed inside Oyster Creek to evaluate the drywell, said Thomas Cervasio, chairman of EnviroWatch, a Berkeley-based environmental watchdog. The drywell is a steel pressure vessel surrounded by reinforced concrete. Both surround the reactor.

"We would feel an awful lot better if we could get an independent study," he said. How much radiation, and how deadly the plume is, would be determined by the severity of any accident and the timing of a release, according to the plant's risk assessment.

The likelihood of a deadly release — which would usually occur in the first six hours of reactor damage — is about 1 in 1.7 million per year, according to plant and NRC officials. A massive radiation release would be the most deadly in the early hours because up to 244,000 residents and visitors may not have enough time to evacuate from the area around the plant.

The plant's 74 percent chance of containment system failure would apply only "in the highly unlikely event that there is a (reactor) core damage event," said Peter C. Resler, manager of nuclear communications for Exelon, which owns plant operator AmerGen.

Core damage includes melting of the highly radioactive fuel in the reactor. Fuel could melt, for example, if a large pipe breaks, and water used to keep the core at a safe temperature is lost.

Oyster Creek's weak containment system is not unique among the 102 other nuclear reactors in the United States.

The integrity of nuclear plant containment systems varies widely, with their chances of failing ranging from 1 percent to 99 percent, according to Lochbaum, of the Union of Concerned Scientists. He cited information from an NRC database that is no longer available.

An expert with the nuclear industry's policy group said that the chances of containment failure have vastly decreased since plants first studied severe accident risks 15 years ago.

The chance of a containment system failing is now generally 10 percent to much less than 1 percent, said Tony Pietrangelo, senior director of risk regulation for the Nuclear Energy Institute, a Washington-based nuclear industry group.

But he could not point to any studies to support his conclusion.

Oyster Creek has a General Electric Mark I containment system, and all plants with such a system installed additional venting systems, according to Pietrangelo. Industry guidelines were developed to preserve containment integrity, among other improvements.

NRC spokesman Neil A. Sheehan said the NRC knows of no new reports on the risks of containment failure at plants.

Following the Sept. 11, 2001, terrorist attacks, the 1997 NRC reports detailing the chance of containment failure were removed from the NRC's Web site.

The NRC removed the documents from the Web because "there was not a desire to point up risks associated with various aspects of nuclear power plant operation," Sheehan said.

The reports, though, are still for sale. Copies of the three-volume report — without the database that details the containment ratings of individual plants — are available for purchase from the U.S. Department of Commerce for $55.85.

Since a commercial nuclear plant has never released a fatal plume of radiation in this country, the probability of such an accident is based on mathematical models.

The likelihood of an accidental radiation leak — be it small or large — is about 1 in 128,000 per year at Oyster Creek, according to AmerGen estimates.

For comparison, the odds of dying from poisoning are 1 in 86,313 a year, according to National Safety Council estimates. The chance of dying from medical and surgical care complications is 1 in 101,281 a year.

The ultimate effects of an early radiation leak would obviously be borne primarily by people living near the plant.

It would take between 7 and 9 1/2 hours to evacuate a 10-mile ring around Oyster Creek known as an emergency planning zone, according to New Jersey's Radiological Emergency Response Plan.

Oyster Creek's containment "would work in minimizing releases of radioactivity early on, which allows time for emergency measures to be put into place," Sheehan said.

Oyster Creek was built in the 1960s with a relatively small General Electric Mark I containment system.

Different systems were built in later years, such as the GE Mark II containments for the Susquehanna 1 and 2 reactors in Pennsylvania. A plant study showed that its containments would have a 1 percent chance of failure, according to data provided by Lochbaum.

"GE wanted to make (the Mark I) smaller and more efficient," said Roger F. Reedy, a California-based nuclear engineering consultant who did the detailed design work for Oyster Creek's reactor and containment vessels based on GE specifications.

The Mark I, and the subsequent GE Mark II and III designs installed at some other nuclear plants, met the American Society of Mechanical Engineers code "that tells you how to build these to be safe," Reedy said. He once chaired the ASME committee that writes the rules for nuclear reactor and containment vessels, he said.

"That code is around the world now because it has a reputation for being safe," he said.

Twenty other boiling water reactors in the United States have GE Mark I containments, according to Hans Ashar, a senior structural engineer for the NRC in Rockville, Md.

This is how a Mark I containment system would work:

During an accident, excess steam and gases would be trapped in the steel shell called the drywell. Connected to the bottom of the drywell is the torus, which is shaped like a doughnut and partially filled with about 1 million gallons of water.

"If you have a discharge of steam (from the reactor vessel during an accident), the hot steam is shoved down into the water in the bottom of the torus," Reedy said. "That cools the steam down immediately, which reduces the pressures."

It is the nuclear equivalent of a child using a straw to cool his hot breath by blowing bubbles into a glass of cold water.

The torus water condenses the steam and also would be pumped into the reactor to help prevent the fuel from melting. Sprayers at the top of the drywell would be used to cool the reactor vessel. In theory, a meltdown would be averted, radiation contained in the drywell and torus, and the public saved from a disaster.

The drywell is rated to withstand 44 pounds of pressure per square inch but can withstand twice that rate, according to Ashar, AmerGen and NRC documents.

Oyster Creek's isolation condenser tubes — which were repaired years ago and help quickly turn steam into water — make the Mark I "a particularly good design, even though it's an older design," said Dennis Zannoni, supervising nuclear engineer in the state Department of Environmental Protection's Nuclear Engineering Section.

"If there's an accident, the steam will be dumped to the isolation condensers, which will condense the steam into water and recirculate it back," Zannoni said. "They're just tubes in a big container, and they're very, very important, and they work well."

Kent Tosch, manager of the DEP Bureau of Nuclear Engineering, said if there were a "high probability of failure" at Oyster Creek overall, "the plant wouldn't operate."

Much of the information that has emerged since the Three Mile Island nuclear plant accident in 1979 suggests that a lot of the radioactive materials in an accident will stay in and around the reactor, significantly reducing "early fatalities," Tosch said.

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