05000387/FIN-2015003-05
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Finding | |
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| Title | Degraded Condition Due to Reactor Coolant Pressure Boundary Leakage Caused by an Inadequate Weld |
| Description | On December 13, 2014, after operators shutdown Unit 1 for a planned forced outage due to increased unidentified leakage, Susquehanna staff identified a small leak by observation on the Unit 1 "B" RRP Lower Seal Cavity Vent 34 piping, a location that Susquehanna determined was part of the reactor coolant pressure boundary. Susquehanna determined that this leakage constituted a violation of the Unit 1 TS, Section 3.4.4 titled "Reactor Coolant System (RCS)" that requires RCS leakage to be limited to no pressure boundary leakage. Susquehanna staff performed a progressive non-destructive examination of the leak site to further characterize the flaw in the socket weld. The evaluation concluded the flaw was a linear defect approximately 0.74 in length through the center of the socket weld and that the apparent cause was a weld defect created during the vendors original manufacturing process. The defective area was removed by progressive grinding with confirmatory liquid penetrant test examinations to confirm the defect length. The weld was repaired and inspected satisfactorily prior to plant startup from the Unit 1 forced outage. The inspector reviewed LER 2014-011 and CR-2014-37848, Revision 1 that documented the related apparent cause evaluation and failure modes analysis for this condition. The inspector also reviewed weld repair work package No. 140469 and the final nondestructive examination reports of the repair area. The inspector determined Susquehanna staffs leak review and analysis process concluded that the leakage, located in the center of the vendor supplied fillet weld was most likely the result of an original weld flaw. The leak area was removed by grinding and the area was repaired by welding to the required 2 to 1 dimensional fillet weld configuration. Although this leak did not appear to be fatigue or system vibration driven, the inspector noted Susquehanna staffs implementation of mitigation methods to reduce socket weld fatigue susceptibilities, including a 2 to 1 fillet weld configuration and instrumented hammer testing of the completed pipe assembly to confirm the absence of resonant frequency vibration modes, were applied. LER 2014-011 documents the licensees violation of TS 3.4.4, limiting reactor pressure boundary leakage during plant operations to zero. This TS violation occurred sometime between unit start-up in July 2014 and plant shutdown on December 13, 2014. The inspector determined that this violation of TS 3.4.4 was more than minor, but not the result of a performance deficiency. In accordance with the NRC Enforcement Policy guidance and IMC 0612, this violation is being treated under the traditional enforcement process and best characterized as a Severity Level IV (very low safety significance) violation, similar to example d.1 in NRC Enforcement Policy, Section 6.1, Reactor Operations. In addition, using IMC 0609, Significance Determination Process, Appendix A, Exhibit 1, Initiating Events Screening Questions, this TS violation screens to Green (very low safety significance) because the boundary leakage did not exceed the capacity of the control rod drive system or TS unidentified leakage (less than 5 gpm) and actual leakage did not adversely impact any LOCA mitigating systems or components. Because this issue is of very low safety significance and it has been determined that it was not reasonable for Susquehanna staff to be able to foresee and prevent this leakage, and as such no performance deficiency exists, the NRC has decided to exercise enforcement discretion in accordance with Sections 2.2.4 and 3.5 of the NRC Enforcement Policy and refrain from issuing enforcement action for the violation of TS (EA-15-149). Further, because Susquehanna's actions did not contribute to this violation, it will not be considered in the assessment process or the NRC's Action Matrix. The inspectors did not identify any new issues during the review of the LER. This LER is closed. |
| Site: | Susquehanna  |
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| Report | IR 05000387/2015003 Section 4OA3 |
| Date counted | Sep 30, 2015 (2015Q3) |
| Type: | Violation: Severity level Enforcement Discretion |
| cornerstone | Barrier Integrity |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | B Smith C Graves E Gray F Bower J Grieves N Graneto T Daun |
| Violation of: | Technical Specification |
| INPO aspect | |
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Finding - Susquehanna - IR 05000387/2015003 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Susquehanna) @ 2015Q3
Self-Identified List (Susquehanna)
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