On 9/18/2015 at 20:00 [CDT], during the Byron Station Unit 1 refueling outage, it was determined that the results of a planned
Liquid Penetrant (
PT) examination performed on a previous overlay repair of the reactor vessel head did not meet applicable acceptance criteria. The
penetration requires repairs prior to returning the vessel head to service. These indications are not in the
reactor coolant pressure boundary; however they are very near the previously repaired J-groove
weld. The examination was being performed to meet the requirements of
10 CFR 50.55a(g)(6)(ii)(D) and
ASME Code Case N-729-1, to ensure the structural integrity of the reactor vessel head pressure boundary. No ultrasonic indications have been identified at this time. Repairs are currently being planned in accordance with the
ASME Code of Record. The repairs will be completed prior to returning the vessel head to service.
This event is being reported under 10 CFR 50.72(b)(3)(ii)(A) for 'Any event or condition that results in the condition of the nuclear power plant, including its principal safety barriers, being seriously degraded.'
The licensee has notified the NRC Resident Inspector.
Per regulatory commitment, Exelon Generation Company, LLC (EGC) is notifying NRC staff of the Division of Component Integrity or its successor, of changes in indication(s) or findings of new indication(s) in the penetration nozzle or J-groove weld beneath a seal weld repair, or new linear indications in the seal weld repair, prior to commencing repair activities.
The original indications that led to the overlay repairs were discovered during ultrasonic testing and were reported to the NRC and assigned
EN46686 and
EN48311.
