10/02/02

Two workers who repaired a steam generator in the heart of the Davis-Besse nuclear power plant last February inhaled or ingested highly radioactive particles from the reactor's damaged fuel rods, say federal regulators who have expanded their investigation into the incident.

The Nuclear Regulatory Commission yesterday dispatched a five-member team of radiation specialists to the Toledo-area power station to examine Davis-Besse's radiation detection equipment and review the procedures the plant management is supposed to enforce when workers enter radioactive areas.

The agency, which expanded the investigation because it disagrees with Davis-Besse officials about the potential threat to the men, also ordered additional tests on them.

"We are not looking at an immediately life-threatening situation," stressed Jan Strasma, the NRC's spokesman for the Midwest region.

"The [laboratory] results so far are far below the point where it would be any immediate health concern," he said. "We are looking at doses that have to be calculated over years. The extra lab tests are to better quantify what the doses would be."

The calculations are based on the half-life, or decay rate, of the specific radioactive elements the men ingested and on the rate at which the human body typically excretes them, Strasma said.

The elements, called "transuranics," are products of atom splitting, or fission, that goes on in the reactor, he said. Reactors produce a number of transuranics, including plutonium and americium, the element in household smoke detectors. But the NRC said it did not know which transuranics the workers ingested. Transuranics decay very slowly.

The two workers were among five people who did maintenance work on the plant's steam generators. They are employees of Framatome ANP, a nuclear service company under contract to Davis-Besse.

In April, FirstEnergy Corp., which operates Davis-Besse, announced that the five had gotten out of the plant wearing clothing contaminated with microscopic radioactive particles. FirstEnergy inspection teams located 13 particles at sites in five states to which the workers had traveled.

The NRC later determined the plant's radiation monitors were not correctly calibrated to detect the fuel rod particles, which are present only if the rods are damaged.

Fuel rod damage can occur in the normal operation of a reactor, said Strasma, and is typically limited to a pinhole, which allows some of the radioactive fuel to escape into the reactor's coolant. The coolant can deposit the particles in the steam generator, where they can become airborne after the reactor is shut down and the steam generator dries.

The two contaminated workers did not use respirators when they entered the massive steam generators, said Todd Schneider, spokesman for Davis-Besse. He said they decided the respirators would slow them down, exposing them to higher radiation doses.

Strasma said there is no NRC regulation mandating respirators in all situations. But there are rules about making a judgment in each case.

"The requirements are that an evaluation be done to determine the appropriate protective gear to be worn for the job," he said. "Obviously, one of the things we are going to be looking at is what precautions were taken."

FirstEnergy and the NRC disagree about the total dosage of radiation the workers are likely to receive, Schneider said, based on laboratory analysis of fecal and urine samples. The last such "bioassay" was done over the weekend, he said, but results will not be available for about three weeks.

Davis-Besse has recalibrated its equipment since the incident, said Schneider, revamped its work programs and bought new whole-body radiation detectors. "The bottom line is that we continue to believe that there was no over-exposure," he said.

The investigation could further delay the restart of Davis-Besse, said Strasma, depending on what the radiation specialists turn up. The reactor has been out of service since Feb. 16. After inspectors found a large rust hole in the reactor's lid in March, the NRC ordered the plant shut down until it is repaired and safe to operate.

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