05000482/FIN-2010005-04
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Finding | |
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| Title | Failure to Evaluate Corrosion Mechanism in Accordance with Code Case N513 |
| Description | On September 15, 2010, the inspectors identified a Green noncited violation of 10 CFR 50.55a(b)(5) for failing to implement the requirements of Code Case N513-2, Section 2.0(e). On June 29, 2010, Wolf Creek discovered a through-wall leak of a 30 inch essential service water pipe. The flaw was evaluated using ASME Code Case N513-2. Code Case N513, Section 2.0(e) required the flaw be re-examined every 30 days unless a flaw growth evaluation is prepared to justify re-examination every 90 days. The evaluation is required to include corrosion rate and corrosion mechanism. The inspectors reviewed the engineering disposition for the flaw and did not find a discussion of the corrosion mechanism or a justification of the corrosion rate. The inspectors reviewed independent laboratory analyses of removed Wolf Creek piping samples that stated that microbiologically influenced corrosion was likely and that the corrosion likely progressed through-wall at a high rate. On September 30, 2010, an engineering disposition was created in response to Condition Report 28077 which included a corrosion evaluation and established a much higher corrosion rate. Key in that corrosion evaluation was the use of empirical data from testing of known flaws which showed a corrosion rate between -4 mils per year to 29 mils per year. The flaw was reexamined after 90 days and minimal growth was found. The failure to comply with the requirements of ASME Code Case N513-2, Section 2.0(e) was considered a performance deficiency. The finding is greater than minor because the failure to perform timely and adequate evaluations of degraded, nonconforming, and unanalyzed conditions for operability, if left uncorrected, would have the potential to lead to a more significant safety concern. The finding is associated with the equipment performance attribute of the Mitigating Systems Cornerstone and affects the associated cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. The inspectors evaluated the significance of this finding using Phase 1 of Inspection Manual Chapter 0609.04, and determined that the finding was of very low safety significance (Green) because the issue did not result in a loss of operability or functionality, and did not screen as potentially risk significant due to a seismic, flooding, or severe weather initiating event. This finding has a crosscutting aspect in the area of problem identification and resolution associated with corrective action program component because operations and engineering personnel failed to thoroughly evaluate problems such that the resolutions addressed the cause and extent of condition. |
| Site: | Wolf Creek  |
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| Report | IR 05000482/2010005 Section 1R15 |
| Date counted | Dec 31, 2010 (2010Q4) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.15 |
| Inspectors (proximate) | G Apger J Groom B Correll N Greene T Farina W Strickland K Clayton D Stearns L Carson D Allen J Adams C Long C Peabody |
| CCA | P.2, Evaluation |
| INPO aspect | PI.2 |
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Finding - Wolf Creek - IR 05000482/2010005 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Wolf Creek) @ 2010Q4
Self-Identified List (Wolf Creek)
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