05000454/FIN-2007009-03
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Finding | |
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Title | Inadequate Design Margins for Continued Operation of Sx Riser Pipes |
Description | The team identified an apparent violation of 10 CFR Part 50, Appendix B, Criterion III, Design Control, associated with the licensees failure to verify the adequacy of the methodology and design inputs used to support licensee decisions to accept the degraded 0B, 0E and 0H essential service water system riser pipes for continued service. Specifically, the licensee failed to evaluate for compressive loads (e.g., buckling), use the applicable Code allowable stress, apply Code equations which account for thermal loads, and failed to correctly apply equations for checking the pipe functional capability. Consequently, the licensee failed to establish adequate design margins for continued service of the 0E, 0H and 0B essential service water system riser which resulted in extended plant operation with degraded SX riser pipes. The cause of this apparent violation was related to the Resources Component (Item H.2(a) of IMC 305) for the cross-cutting area of Human Performance, because the licensee failed to maintain plant safety by maintenance of design margins. Specifically, these degraded riser pipes remained in-service without establishing adequate design margins in the engineering evaluations to justify continued service. The licensee subsequently completed a plant shutdown and replaced the degraded portions of these essential service water system riser pipes. The finding associated with this apparent violation was greater than minor because the degraded essential service water piping condition resulted in an increase in the likelihood of the loss of the essential service water system due to pipe failures, which directly affected the Initiating Events Cornerstone. It was also associated with the Equipment Performance attribute of the Mitigating Systems Cornerstone and affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences (i.e., core damage). The finding associated with this apparent violation was assessed using a Phase 3 analysis in accordance with NRC Inspection Manual Chapter 0609 Appendix M, Significance Determination Process Using Qualitative Criteria, and is preliminarily determined to have low to moderate safety significance (White) |
Site: | Byron |
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Report | IR 05000454/2007009 Section 4OA3 |
Date counted | Mar 31, 2008 (2008Q1) |
Type: | Violation: White |
cornerstone | Initiating Events, Mitigating Systems |
Identified by: | NRC identified |
Inspection Procedure: | IP 71153 |
Inspectors (proximate) | C Moore D Hills J Mcghee L Kozak M Holmberg T Bilik V Meghanib Kemkerj Jacobson R Skokowskij Heckp Lougheed S West |
CCA | H.6, Design Margins |
INPO aspect | WP.2 |
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Finding - Byron - IR 05000454/2007009 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Byron) @ 2008Q1
Self-Identified List (Byron)
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