On March 18, 2006, with the Davis-Besse Nuclear Power Station in Mode 6 (Refueling), an axial indication was discovered on the
Reactor Coolant Pump 1-1 Cold Leg Drain Line Nozzle to Elbow
Weld. At the
time of discovery, the indication was determined to be at least 0.25 inches in length, but the through-wall depth of this indication could not be determined.
Further evaluation of this indication is in progress by an offsite engineering organization. Based upon preliminary evaluation, it has been determined that this indication cannot be found acceptable under ASME Section XI.
10CFR50.72(b)(3)(ii)(A) requires reporting of any event or condition that results in the condition of the nuclear power plant, including its principal safety barriers, being seriously degraded. NUREG-1022, 'Event Reporting Guidelines - 10CFR50.72 and 10CFR50.73' lists as an example of such degradation 'Welding or material defects in the primary coolant system which cannot be found acceptable under ASME Section XI, IWB-3600, 'Analytical Evaluation of Flaws' or ASME Section XI, Table IWB-3410-1, 'Acceptance Standards.'
Based upon the preliminary evaluation by the offsite engineering organization, the axial indication is being conservatively reported per 10CFR50.72(b)(3)(ii)(A) as a serious degradation of a principle safety barrier. The plant is currently defueled, and plans are underway to determine the necessary repair [to] this indication.
The licensee will notify the NRC Resident Inspector.
