Microscopic amounts of radioactive fuel particles were found on four people who worked inside FirstEnergy's Davis-Besse nuclear plant in March, leading Nuclear Regulatory Commission officials yesterday to say the agency is concerned by the discovery but doesn't believe there is a public safety threat.

The NRC this week dispatched three inspectors to Davis-Besse, along the Lake Erie shorefront in Northwest Ohio, to determine where the radioactive particles came from. The 13 particles that were found emitted radiation at nearly undetectable levels -- far, far less than a person would get from a typical chest X-ray, an NRC official said.

Even so, the particles never should have left the confines of the power plant if that's where they originated, the official said.

``It is unusual in our eyes,'' said Kenneth Riemer, branch chief in the division of reactor safety at NRC's Chicago regional office. ``You would normally not expect to see these particles outside the plant. It caught our attention. It definitely piqued our interest enough to send out inspectors.''

FirstEnergy said it has since added to its screening procedures at Davis-Besse to better ensure that anyone contaminated with radioactive particles is detected before they leave the premises.

The contamination is not related to the damaged Davis-Besse reactor vessel head, where acid created two cavities on top of the 150-ton steel dome safety device, officials said. The plant was shut down in mid-February for refueling, and has stayed closed after the vessel head damage was discovered in March.

It's possible that the particles did not originate within Davis-Besse, FirstEnergy and the NRC said, though one nuclear power critic thought that to be unlikely. The workers, who were hired under contract for Davis-Besse's refueling outage, arrived at the Oak Harbor site from three different nuclear plants and another company.

The discovery of the radiation originated with Duke Energy's Oconee Unit 1 nuclear plant in South Carolina. Monitors there on March 22 detected radiation on the sleeve of one man who had left Davis-Besse to work at Oconee Unit 1. The plant then notified FirstEnergy and the NRC about the radiation, a Duke spokesman said.

FirstEnergy's investigation subsequently found more radioactive particles on the workers, in their vehicles and where they stayed in hotels near Davis-Besse in Port Clinton, and in Texas, Virginia and South Carolina, the NRC said. Two of the particles were found at Davis-Besse.

The four workers had all been working on the Davis-Besse steam generator, which transfers heat from the radioactive fuel core to a secondary steam system that in turn drives a turbine to make electricity. The area is highly radioactive -- the workers can stay there for no more than two minutes.

The amount of radiation from the particles amounts to .002 millirems per hour, FirstEnergy spokesman Todd Schneider said. That extremely low level of radioactivity does not need to be reported to the NRC, he said.

``If you put all (13) of those on the tip of a pen, you couldn't see them. They are nothing to be alarmed about,'' he said. ``There's no health impact.''

FirstEnergy's investigation found one particle in each of the workers' temporary living quarters, Schneider said. FirstEnergy used monitoring equipment that went over a 2-inch-square area at a time, he said. The radioactive particles were removed using a piece of tape, which was then brought back inside Davis-Besse, he said.

Preliminary findings show that the four workers should suffer no health problems from being exposed to the particles, the NRC said.

The particles probably came from small leaks of reactor coolant at the steam generator, said NRC spokesman Victor Dricks. The particles can become electrically charged and then stick to the clothing of anyone working nearby, he said.

Schneider said Davis-Besse monitors detected similar small amounts of radioactive particles on two other contracted workers when they initially checked in at the plant for the current refueling. The workers had arrived from another plant, he said. Davis-Besse notified the other plant -- Schneider said he didn't know which plant -- of the radiation.

Shari Weir of Ohio Citizen Action said Ohio residents need to be concerned about the incident.

``It appears there was a breakdown of radiation protection,'' she said. ``The bottom line is, public safety is at risk and worker safety is at risk. I would hope this is unusual. The community at large was being exposed.''

David Lochbaum, nuclear power expert for the Union of Concerned Scientists, said it appeared that FirstEnergy and the NRC were doing the right thing in investigating how the radiation got out and sharing their findings with the industry.

``It's not the first time and it probably won't be the last'' for this type of incident, he said. ``Nobody's happy when it happens.''

FirstEnergy stock closed down 8 cents to $32.91.

FirstEnergy finishes damage report

FirstEnergy may have its final report ready today for federal regulators showing how boric acid damaged a key safety component in its Davis-Besse nuclear power plant.

In addition, the Akron utility may submit its final repair plans to the Nuclear Regulatory Commission at the end of next week, FirstEnergy spokesman Todd Schneider said yesterday. Either report could be pushed back to other dates, he said.

FirstEnergy has given the NRC a preliminary report showing how it believes boric acid leaked on the reactor vessel head and created two cavities on top of the steel structure. It also met with the NRC last week when it presented its initial repair plans. The company estimates repairs will cost at least $16 million and take as long as four weeks to complete.