05000369/FIN-2008008-01
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Finding | |
|---|---|
| Title | Failure to Take Adequate Corrective Action for Implementation of Safety-Related RN Strainer Backwash) |
| Description | On December 31, 2007, the U.S. Nuclear Regulatory Commission (NRC) completed a quarterly integrated inspection at your McGuire Nuclear Station. The inspection findings were documented in NRC Inspection Report 05000369/2007005 and 5000370/2007005, which was issued on January 31, 2008. Section 4OA3 of that report identified Unresolved Item (URI) 05000369,370/2007005-03, which concerned a failure to take adequate corrective action related to implementation of a safetyrelated service water (RN) strainer backwash system. Subsequent to additional inspection, the performance deficiency was identified as a failure to correct a significant condition adverse to quality identified in 2002 related to macro-fouling of the RN strainers, in that the corrective action failed to ensure that the design and licensing basis required ability for manual strainer backwash could be maintained even during accident conditions. More specifically, the 2003 plant modification that was implemented to address the macro-fouling concern (i.e., upgrade and reclassification of the strainer backwash function to safety-related): (1) utilized non-safetyrelated instrument air (VI) to maintain each RN pumps strainer backwash discharge valve open, but did not provide a means to manually open (or bypass) the discharge valve to support backwash operations upon a loss of VI; and (2) did not account for the impact on timely operator response from higher strainer macro-fouling rates (whether from fish or other potential sources) and expected (nuisance) strainer delta pressure alarms (without fouling) at the onset of high RN flow events (i.e., safety injection and loss of VI). As such, between 2003 and August 7, 2007, there was a lack of reasonable assurance that the RN system would be able to perform its safety-related function upon a safety injection or loss of VI event during periods of macrofouling This finding was assessed based on the best available information, including influential assumptions, using the applicable Significance Determination Process (SDP) and was preliminarily determined to be a Greater Than Green Finding. Enclosed is a summary of the SDP Phase 3 analysis. It reflects a finding of greater than very low safety significance because, in the event of a loss of RN backwash capability, either through response to a safety injection signal or a loss of VI, that occurs during a time of high fouling potential, there was a lack of reasonable assurance that the RN system would have been capable of performing its safetyrelated function. The significance of the finding is influenced by uncertainties in the calculation for assumptions made for the initiating event frequency for the loss of VI, and for the calculated exposure time for the periods of fouling. Because of these uncertainties, the result was classified as Greater Than Green. The finding does not represent a current safety concern because temporary modifications and appropriate procedural changes have been made to address periods of potential macro-fouling. The finding is also an apparent violation (AV) of 10 CFR 50 Appendix B Criterion XVI, Corrective Action, for the failure to correct a significant condition adverse to quality related to macro-fouling of the RN strainers. This apparent violation (identified as AV 05000369,370/2008008-01, Failure to Take Adequate Corrective Action for Implementation of Safety-Related RN Strainer Backwash) is being considered for escalated enforcement action in accordance with the NRC Enforcement Policy. Accordingly, for administrative purposes, URI 05000369,370/2007005-03 is considered closed. |
| Site: | McGuire  |
|---|---|
| Report | IR 05000369/2008008 Section 4OA3 |
| Date counted | Dec 31, 2007 (2007Q4) |
| Type: | AV: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | S Rose V Mccree C Evans J Moorman J Wray R Bernhardh Gepfordj Brady J Diaz J Moorman R Eul R Hamilton R Taylor S Walker W Looc Evansr Bernhard S Rose |
| INPO aspect | |
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