05000280/FIN-2010006-01
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Finding | |
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| Title | Failure to Identify and Correct Degraded Unit 1 Nuclear Instrument RC Filters |
| Description | An NRC identified non-cited violation of 10 CFR 50, Appendix B, Criteria XVI, Corrective Action, was identified for the licensees failure to identify and correct degraded RC filters associated with Unit 1 Nuclear Instrument (NI) cabinets for N-42 and N-44 based on a similar degraded condition identified on Unit 2 NI cabinet N-43 in November 2009. The issue was entered into the licensees corrective action program as condition report CR383881. All the RC filters in the Surry Unit 1 and 2 NI cabinets have been replaced with new RC filters. The finding was determined to be of more than minor significance because it is associated with the equipment performance attribute of the Initiating Events cornerstone. It adversely affected the cornerstone objective of protection against external events, i.e., fire. The performance deficiency was screened using phase 1 of the Significance Determination Process (SDP) and was determined to be a fire initiator contributor and to have impact on post fire safe shutdown, therefore a phase 2 analysis utilizing Inspection Manual chapter 0609 Appendix F was required. Since the finding involved MCR fire scenarios, a phase 3 analysis was required. A phase 3 risk analysis was performed by a regional SRA in accordance with IMC 0609 Appendix F, NUREG/CR6850, and utilizing the latest Surry SPAR probabilistic risk analysis model. The fire scenarios were determined to impact MCR operator actions but would not credibly require MCR evacuation for either habitability or safe shutdown functional requirements. The dominant sequence was a fire induced reactor trip transient initiator, with failures of auxiliary feedwater, main feedwater and failure to implement feed and bleed leading to core damage. Factors which mitigated the risk of the fire were the minimal fire growth potential and the potential for NI cabinet fires to damage SSD equipment. The risk evaluation result was an increase of <1E-6 for core damage frequency, a finding of very low risk significance (Green). This finding involved the cross cutting area of problem identification and resolution, the component of operating experience (OE), and the aspect of evaluating internal OE (P.2.a), because the licensee did not effectively evaluate the internal operating experience gained from the November 2009 RC filter failure prior to the failure of the RC filters on June 8, 2010. |
| Site: | Surry  |
|---|---|
| Report | IR 05000280/2010006 Section 4OA5 |
| Date counted | Sep 30, 2010 (2010Q3) |
| Type: | NCV: Green |
| cornerstone | Initiating Events |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 93812 |
| Inspectors (proximate) | S Walker A Hutto R Clagg L Wert |
| Violation of: | 10 CFR 50 Appendix B 10 CFR 50 Appendix B Criterion XVI |
| CCA | P.5, Operating Experience |
| INPO aspect | CL.1 |
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Finding - Surry - IR 05000280/2010006 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Surry) @ 2010Q3
Self-Identified List (Surry)
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