OAK HARBOR - Federal officials Wednesday heaped more blame on FirstEnergy for its safety procedures at the Davis-Besse nuclear plant, this time for a series of events that allowed 16 radioactive particles to leave the plant on workers' clothing.

The amount and type of radiation that escaped the plant does not pose a public health threat, the Nuclear Regulatory Commission said. And while the radiation probably exceeds levels allowed by the NRC, it is also unlikely to be a health threat to the contaminated workers.

At least two workers ingested microscopic radioactive particles. Test results from four independent laboratories won't be available for about three weeks, NRC officials said.

The NRC announced the findings Wednesday morning at the Akron utility's damaged Davis-Besse plant.

The NRC found that First-Energy:

• Failed to identify adequately how much radiation was in the steam generator, despite numerous opportunities to do so.

• Failed to do timely and suitable measurements of radiation in work areas and of radiation excreted from the workers.

• Failed to survey adequately workers for radioactive contamination before they left the plant.

• Did not consider the impact of small fuel leaks over the years, and ignored indications that the latest fuel leaks were worse than in previous years.

• Did not reassess the implications of an increase in radiation levels in the steam generator nine hours before work was to start there.

All of that increased the potential for workers to be exposed to radioactive particles in excess of NRC limits, the NRC said.

Davis-Besse has remained shut down since a safety inspection in March found two unprecedented boric acid-created cavities on top of the reactor's former vessel head, a large steel dome that covers the radioactive fuel core. FirstEnergy has pushed back its hoped-for restart date from December to early next year, though the NRC will have to give its approval first.

The accidental release of the radioactive particles, which is not directly related to the vessel head problem, was discovered March 22 when one of the workers arrived at the Oconee nuclear power plant in South Carolina, setting off monitors there. Other particles were subsequently found in Ohio, South Carolina, Virginia and Texas.

The six workers were contaminated while working in the plant's steam generator, a massive device that typically contains high levels of radiation. The workers, while wearing protective clothing, did not wear devices that would have prevented them from breathing in any radioactive particles. Davis-Besse personnel thought putting on additional apparatus would slow their work and actually increase their exposure to radiation, but didn't adequately measure the amount of radiation in the generator before they started work, the NRC said.

An employee also misread the amount of allowable radiation for part of the generator work, the NRC report said.

And while the workers went through decontamination procedures several times, some articles of clothing and shoes worn inside the steam generator weren't screened, the NRC said. A technician also assumed that radiation monitors were picking up evidence of ingested radioactive particles, not particles on clothing, the NRC said. .

The significance of the NRC's findings hasn't been determined. Each finding might violate NRC requirements, the agency's report said.

``There are expected to be no consequences to the public,'' said Tom Kozak, the NRC official who headed the investigations into the release of the particles. Clothing and skin are enough to prevent any radiation from the particles -- invisible to the naked eye -- getting inside a person, he said.

But a breathed-in particle could end up lodged deep inside a lung, with potential health consequences depending on the size and type of radioactive particle, said John House, an NRC official who led one of the inspections. On the other hand, a radioactive particle that was ingested would likely pass through a person very quickly, he said.

FirstEnergy has put in place corrective measures, Kozak said.

Lew Myers, chief operating officer for FirstEnergy's nuclear operating company that runs Davis-Besse, said the company had no conflicts with the NRC's findings.

``We thought your investigation was very accurate,'' he said.