19 April 2002 – FirstEnergy Nuclear Operating Company (FENOC) announced today that it has submitted its Root Cause Analysis Report to the Nuclear Regulatory Commission (NRC) regarding the cause of the corrosion problem on the reactor pressure vessel head at the Davis-Besse Nuclear Power Station.
The Report’s conclusions are consistent with the Probable Cause Summary Report provided to the NRC on March 22, 2002, and the findings of the NRC Augmented Inspection Team presented on April 5, 2002. The Report indicates that the damage resulted from boric acid seeping through cracks in two of the Control Rod Drive Mechanism nozzles and corroding carbon steel in the reactor pressure vessel head. Also, the cracks in the stainless steel nozzles probably occurred over a period of four years, or more.
The Report also cites a number of contributing factors to the corrosion, including missed opportunities for earlier detection of the problem. For example, buildup of boron deposits on top of the head probably masked the existence of the cracked nozzle problem for several years; installation of modifications to the service structure on the reactor head would have enabled better inspection and maintenance of the reactor pressure vessel head and related equipment; and proper implementation of the plant’s Boric Acid Corrosion Control Program might have prevented the corrosion damage and ensured early detection and removal of the boric acid deposits.
The Report also lists a number of corrective actions, some of which already have been implemented. For example, the Report recommends modifying the service structure on the head to facilitate inspection and maintenance of this equipment — a project that has been completed.
A comprehensive inspection of all the Reactor Coolant System equipment to ensure there is no other corrosion damage currently is under way. Also, engineering personnel are conducting a comprehensive review of about 40 plant systems to identify and resolve any possible long-term equipment concerns. Additionally, the Boric Acid Corrosion Control Program is being enhanced to require more specific and stringent standards and more rigorous implementation. And, management oversight of these programs and activities will occur at a much higher level within the FENOC organization.
While the Root Cause Analysis Report is under review by the NRC, Davis- Besse personnel and industry experts continue to finalize a plan to safely repair the corrosion damage.
Davis-Besse is owned by Akron, Ohio-based FirstEnergy Corp. (NYSE: FE – news), and operated by its subsidiary FirstEnergy Nuclear Operating Company. FirstEnergy is a registered public utility holding company.