Plant management and personnel were at fault in failing to discover, until it was almost too late, a leak and significant corrosion in a reactor vessel head at the Davis-Besse nuclear power plant, at Oak Harbor, OH, according to a report submitted to the Nuclear Regulatory Commission (NRC) by plant owner FirstEnergy Nuclear Operating Co. (FENOC) last Thursday.

The Root Cause Analysis Report addresses management and organizational issues that contributed to the corrosion problem that was discovered last February when it had eaten through six inches of carbon steel on the top of a reactor pressure vessel. Less than half an inch of the reactor vessel’s stainless steel liner remained, separating the reactor’s highly radioactive and pressurized internal environment (2,500 psi) from blasting into the reactor containment building, damaging safety equipment and possibly setting into motion a core melt accident (see Power Market Today, March 14; April 1; April 12).

After the problem was discovered at Davis-Besse, the NRC ordered all operators of similar pressurized water reactors (PWR) to submit a schedule for special inspections of their equipment. Last week the agency said that additional discoveries of cracked and leaking vessel head penetration nozzles at several PWRs had raised concerns about the adequacy of current inspection programs that primarily rely on visual examinations to identify nozzle cracking, boric acid leakage and corrosion. The NRC has put the nation’s 69 PWR licensees on notice that they may have to conduct supplemental inspections (see Power Market Today, Aug. 12).

Initial investigations into the Davis Besse incident estimated the corrosion could have been building up for as much as four years, meaning it had been missed in routine maintenance inspections.

The report submitted to the NRC Thursday was authored by a team of nuclear experts commissioned by FENOC management. It focuses on nuclear safety and human performance issues, as part of the plant’s program to improve performance and earn approval of the NRC for restarting operations. Recommendations from the team include adhering strictly to industry performance standards, improving program implementation, increasing effectiveness in making corrective actions, and enhancing management oversight.

“Addressing the management and human performance issues identified in this root cause report is as important as the actual restoration of the reactor head,” said Lew W. Myers, FENOC COO, who was reviewing the report’s findings in an NRC public meeting Thursday.

Human performance factors cited in the report included missed opportunities for earlier detection and prevention of the problem. The report states, among other things, that plant management and personnel:

Other observations by the team include improving training for those conducting boric acid inspections, increasing management involvement and oversight of field activities, and realigning the incentive pay program to increase emphasis on safety.

Extensive changes in the officers, directors and managers responsible for the plant already have been made.

Team members who prepared the report include three outside experts in root cause analysis — two from Conger & Elsea and one from ENERCON — as well as two experienced nuclear professionals from the Beaver Valley Nuclear Power Station, two from the Perry Nuclear Power Plant and several from Davis-Besse.

“The team operated independently in fulfilling their mission — to give us a frank and objective perspective on what led to this problem and solid recommendations for improving our performance,” Myers said.

FENOC is in the process of installing a substitute reactor head, which it bought from CMS Corp. The reactor had been part of Consumers Energy’s Midland Nuclear Plant, which was never completed. The unit is expected to be restarted sometime in the fourth quarter.

The bulletin issued by the NRC Aug. 12 provides suggested inspection schedules and examples of acceptable supplemental inspection techniques, including the use of ultrasound, electric currents and liquid dyes to check for cracking and corrosion in metal structures. The bulletin asks that within 30 days licensees provide written responses, describing their plans for future inspections.

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