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| 11-13-2013 | On September 14, 2013 at 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />, indications exceeding ASME Section III acceptance criteria were discovered in the embedded flaw repair weld of Control Rod Drive Mechanism (CREW) Penetration 69. A total of 22 recordable indications located within the embedded flaw repair weld were documented, with 13 rounded indications exceeding the acceptance criteria ( ASME Section III 1971 Edition through the Summer 1973 Addenda) of dimensions greater than 3/16. The indications in Penetration 69 were removed/reduced to acceptable size or reduced and weld repaired to restore the embedded flaw repair as approved by the NRC in Braidwood Relief Request 13R-09. This LER is being submitted in follow-up to ENS 49343 that was made at 0447 hours0.00517 days <br />0.124 hours <br />7.390873e-4 weeks <br />1.700835e-4 months <br /> on September 14, 2013.
Based on industry experience, the cause of this event was determined to be mechanical discontinuities/minor subsurface voids opening up to the weld surface due to thermal and/or pressure stresses during plant operation.
Corrective actions to prevent recurrence include consideration of a long term Alloy 600 mitigation plan and other potential alternatives for the remaining acceptable but unrepaired penetrations on the Braidwood Units 1 and 2 RPV closure heads. This corrective action plan is under development and will also evaluate peening of the remaining acceptable but unrepaired CRDM penetrations. |
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A. Plant Operating Conditions Before the Event:
Event Date: September 14, 2013 Unit: 1 MODE: 6 Reactor Power: 000 percent Unit 1 Reactor Coolant System [A]]: Shutdown for refueling outage, no fuel movement in progress No structures, systems or components were inoperable at the start of this event that contributed to the event.
B. Description of Event:
On September 14, 2013 at 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />, indications exceeding ASME Section III acceptance criteria were discovered in the embedded flaw repair weld of Control Rod Drive Mechanism (CRDM) Penetration 69. The Al R17 examination of the embedded flaw repair in Penetration 69 was performed in accordance with Braidwood Third Interval Relief Request