Energia i regulacje · 15/08/2002

Reactor Pressure Vessel Head and Vessel Head Penetration Nozzle Inspection Programs; Issue

The Nuclear Regulatory Commission (NRC) has issued Bulletin (BL) 2002-02 to all holders of operating licenses for pressurized-water reactors (PWRs), except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor vessel, and all holders of operating licenses for boiling-water reactors for information. It concerns the recent discoveries of cracked and leaking Alloy 600 vessel head penetration (VHP) nozzles at several PWRs and the reactor pressure vessel (RPV) head degradation at Davis- Besse Nuclear Power Station. These discoveries have raised concerns about the adequacy of current inspection programs that rely on visual examinations as the primary inspection method to ensure RPV head and VHP structural integrity. Specifically, the staff is concerned that the inspection methods and frequencies (i.e., inspection intervals) of current inspection programs may not be sufficient. Based on experience and information currently available, it may be necessary for inspection programs that rely on visual examinations to be supplemented with additional measures (e.g., volumetric and surface examinations) to demonstrate compliance wi