05000387/FIN-2015003-06
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Finding | |
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| Title | Degraded Condition Due to Reactor Coolant Pressure Boundary Leakage Caused by Vibration and Stiff Pipe Connection |
| Description | On April 11, 2015, during the initial drywell walk down following shutdown for the spring 2015 Unit 2 refueling outage, Susquehanna staff identified a small leak on the Unit 2 "A" RRP seal piping at a seal flange weld associated with the pressure and vent piping to the upper seal chamber (Connection #2). Water was observed spraying out of the top of the pipe in a fan pattern. Susquehanna staff determined that this leakage constituted a violation of the Unit 2 TS, Section 3.4.4, titled "RCS" that requires RCS leakage be limited to no pressure boundary leakage. Based on the unidentified leakage rate of 0.25 gpm measured during plant operation and visual inspection of the leak area, the leak most likely existed during plant operation. Susquehanna staff removed the seal flange and piping assembly containing the leak area and provided that material for metallurgical investigation. A qualified replacement assembly was installed with a modified pipe routing to provide for increased pipe flexibility and was inspected prior to and during startup from the Unit 2 refuel outage. The inspector reviewed LER 2015-004, CR-2015-09907, the apparent cause evaluation completed for this leak, the metallurgical and structural analysis inputs, and CR-2015-009953 regarding the extent of condition evaluation scope. The leakage cause was attributed to the short rigid piping span between the pump and H5005 support with atypical vibration between the two. Using a modified pipe routing to increase pipe flexibility, the seal flange with pipe assembly was replaced. The modified pipe configuration was instrumented and hammer tested to confirm its vibrational frequency characteristics. LER 2015-004 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 2 start-up in 2013 and plant shutdown on April 10, 2015. 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 loss-of-coolant accident 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-15-189). 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  |
|---|---|
| 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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