Nuclear decay prompts scrutiny

WASHINGTON -- A nuclear reactor in Ohio has a large hole nobody thought possible, burned almost through its 6-inch steel cover. Cracks of a type never seen before are discovered in a South Carolina reactor, triggering widespread inspections.

Both surprised industry leaders and government regulators, and they are fueling new questions about aging nuclear power plants and plant inspection programs.

Some Nuclear Regulatory Commission officials see the discoveries at the Davis-Besse plant in Ohio and Oconee Unit 3 reactor in South Carolina as the most significant safety issue facing the industry since the Three Mile Island accident 23 years ago.

The cracks found last year at Oconee, similar to those discovered at Florida Power's Crystal River plant, and the hole discovered in March in the steel reactor lid at Davis-Besse were in areas thought largely impervious to such problems.

The 25-year-old Davis-Besse reactor has been shut down since February, waiting for the hole to be patched.

The steel reactor vessel, which encloses the reactor's core, has always been viewed as "a sacred component" that will not be breached, said the NRC's Brian Sheron. "This really challenges that assumption."

An inspection of most of the 68 other plants with similar designs and conditions reported no corrosion. But regulators ordered special inspections at 14 reactors thought to be vulnerable to nozzle cracking because of age.

One of those was Crystal River. During an October refueling, inspectors found a circular crack partway around one of the nozzles that penetrate the 80-ton reactor lid.

The crack allowed an unknown amount of water with boric acid, used to control the level of nuclear reaction, to leak. Left undetected, the acid would have posed a serious threat; in the Ohio plant, it nearly ate through the reactor lid.

"We found no evidence whatsoever of any metal damage like that found at Davis-Besse," Florida Power spokesman Mac Harris said Monday.

Still, in a report to the NRC not long after the Davis-Besse problem surfaced, Florida Power said it plans to replace the 25-year-old vessel lid in fall 2003.

The utility said the decision is precautionary because the metal is susceptible to problems. A new lid would presumably aid Florida Power's efforts to get a 20-year life extension of the plant, which is licensed through 2016.

The problems in Ohio and South Carolina were discovered before they posed an immediate safety risk. A break through the reactor cover would have caused thousands of gallons of radioactive water to spew into the containment building, raising the risks of the core overheating and a meltdown and release of radiation.

Only a thin noncorrosive stainless steel membrane kept the hole at the Ohio reactor from bursting. The cracks at Duke Power's Oconee plant were less urgent. But had the crack expanded, it could have caused the nozzle to separate, causing a loss of cooling water inside the reactor, experts said.

Industry spokesmen said backup systems would have averted more serious problems by pumping more water into the reactor than was being allowed to escape, keeping the nuclear fuel safe until the reactor could be shut down.

But that's true if everything worked perfectly, said David Lochbaum, a nuclear engineer and industry watchdog for the Union of Concerned Scientists. And that might not be the case if emergency pumping systems became clogged, if other equipment is damaged or if a gauge is misread by plant operators struggling to make sure the reactor core is covered with water, he said.

NRC officials said inspections of other reactors have found no buildup of boron contamination. The NRC reports 62 nozzle cracks have been found at a dozen reactors, and all but 16 had been repaired as of last month. Two more reactors are being closely watched because of age and other characteristics, the agency said.

NRC officials said inspections of other reactors have found no buildup of boron contamination. Nozzle cracks have been found at 34 reactors, including Crystal River, and are being fixed.

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