For more than two and a half hours, the federal oversight team subjected details of a seven-part plan submitted by the energy company to "a plethora of intrusive questions," as NRC official Jack Grobe described. A crowd at the Oak Harbor High School auditorium heard sometimes-frank discussions on what went wrong at the plant, and what must be done before it can reopen.

Boric acid devoured a half-foot-deep hole in the Davis-Besse reactor head -- to a degree, in fact, unseen at any other United States nuclear power plant. FirstEnergy is in the early stages of an internal personnel study on the "root cause" of why the corrosion escaped detection.

"This event does not point to a single individual," FirstEnergy official David Eshelman said. "This event does not point to a single department, individual or team."

The root cause report should be finished by month's end, Eshelman said. In a prepared statement, the energy firm told the NRC and the audience that the corrosion resulted from human performance lapses:

"Management ineffectively implemented processes, and thus failed to detect and address plant problems as opportunities arose."

FirstEnergy chief operating officer Lew Myers said Davis-Besse's successful track record might have led managers to become complacent. "That's a major problem you always have to be on guard against," he said.

Grobe said the NRC remains in "the very early stages" of gaining confidence in FirstEnergy's plans to improve operations and re-open Davis-Besse.

"Hardware is easy. Hardware is easy to fix," Grobe said. "(Labor) is the hard part."

Another key area of NRC concern was the "boric acid atmosphere" present inside the reactor containment building. Plant Manager Randy Fast said boric acid also corroded electrical panels and metal duct panels near the personnel airlock, plus three air coolers.

"It's certainly not acceptable to me or my team, and I have personally taken managers into containment to see those areas," Fast said of the acid damage.

Grobe and others asked FirstEnergy officials if boric acid had also damaged gaskets, coatings and other surfaces inside the containment building.

Fast said two dozen engineers are now inspecting the building's interior. NRC panel members questioned the engineers' experience levels and FirstEnergy's inspection requirements.

FirstEnergy's strategy to re-open Davis-Besse includes seven sub-plans. Each is headed by a high-ranking administrator, and topics include reactor head replacement, management evaluation, equipment assessment, and inspection and operational reviews.

Ottawa County Administrator Jere Witt is part of an independent review panel that will also watch FirstEnergy's start-up efforts.

"Obviously, there are some problems that need to be addressed. But they're doable," Witt said. "I think they've got a tough road ahead of them, but that's OK because we need to find out what happened."

Contact staff writer Rick Neale at 419-734-7506 or rneale@fremont.gannett.com.