05000346/FIN-2012004-04
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Finding | |
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| Title | Licensee-Identified Violation |
| Description | Inadequate Design Control Results in Reactor Coolant System Pressure Boundary Leakage From Reactor Coolant Pump Seal Piping Socket Weld Appendix B to 10 CFR Part 50, Criterion III, Design Control, requires, in part, that the licensee establish measures for the selection and review for suitability of application of materials, parts, equipment, and processes that are essential to the safety-related functions of SSCs. Criterion III further requires that design changes, including field changes, shall be subject to design control measures commensurate with those applied to the original design. As discussed in Section 4OA3.2 of this report, contrary to this requirement, licensee personnel failed to properly review the suitability of a modification that was performed to their RCP seal cavity vent lines to accommodate a new style of RCP seal package in 1990. Specifically, the RCP seal cavity vent lines were lengthened by approximately five inches, and the licensees engineering design personnel failed to consider what the impact of changing the small bore (i.e., 34 inch diameter) piping length would have on the piping resonance frequencies and the piping socket welded connections. Industry operating experience has shown that minor changes to small bore piping can result in higher amplitude vibrations, potentially resulting in high-cycle fatigue failure. A licensee causal evaluation team concluded that a pinhole leak through a socket weld on the RCP 1-2 first stage seal cavity vent line that occurred on June 6, 2012, was most probably this kind of high-cycle fatigue failure. The objective of the Barrier Integrity Cornerstone of Reactor Safety is to provide reasonable assurance that physical design barriers (fuel cladding, RCS, and containment) protect the public from radionuclide releases caused by accidents or events. Key attributes of this objective are design control, and specifically plant modifications, and RCS equipment and barrier performance. In accordance with NRC IMC 0612, Power Reactor Inspection Reports, Appendix B, Issue Screening, the inspectors determined that the violation was of more than minor significance in that it had a direct impact on this cornerstone objective. The licensees failure to consider what the impact of changing the small bore piping length would have on the piping resonance frequencies and the piping socket welded connections resulted in a pinhole failure of the RCS pressure boundary, and compromised the RCS barrier performance. The inspectors also determined that since the licensees performance deficiency had occurred in 1990, the licensee-identified violation constituted an Old Design Issue, as defined by the NRC Enforcement Policy, which was not indicative of current licensee performance. As discussed in Section 4OA3.2 of this report, the licensee had entered this issue into their CAP as CR 2012-09381. Immediate corrective actions taken by the licensee included repair of the leak on the RCP 1-2 first stage seal cavity vent line, as well as inspections of all similar RCP seal cavity vent lines for any signs of leakage. The licensee has plans to replace all of the current RCP seal cavity vent lines with flex hose connections during the next refuel outage in 2014. |
| Site: | Davis Besse  |
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| Report | IR 05000346/2012004 Section 4OA7 |
| Date counted | Sep 30, 2012 (2012Q3) |
| Type: | NCV: Green |
| cornerstone | Barrier Integrity |
| Identified by: | Licensee-identified |
| Inspection Procedure: | |
| Inspectors (proximate) | J Neurauter A Wilson D Kimble J Bozga J Cameron T Briley |
| INPO aspect | |
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Finding - Davis Besse - IR 05000346/2012004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Davis Besse) @ 2012Q3
Self-Identified List (Davis Besse)
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