05000361/FIN-2011003-01
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Finding | |
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| Title | Inadequate Compensatory Measures for a Design Nonconformance |
| Description | The inspectors identified a noncited violation of 10 CFR Part 50, Appendix B, Criterion V, for the failure of operations personnel to establish adequate compensatory measures to restore or maintain operability as required by Procedure SO123-XV-52, Operability Determination and Functionality Assessments, Revision 18. Specifically, on November 12, 2010, although engineering identified measures were required to maintain water level below the steam line in the auxiliary feedwater trenches, no measures had been taken to stage pumps or limit flows into the trenches. On May 5, 2011, as a result of the inspectors questions, the licensee established additional compensatory measures including blocking storm drains that flow into the trench and staging sump pumps. This issue was entered into the licensees corrective action program as Nuclear Notification NN 201448584. The performance deficiency is more than minor, and therefore a finding, because it is associated with the protection against external events attribute of the Mitigating Systems Cornerstone and affects the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. During a design basis flooding from a probable maximum precipitation event, the auxiliary feedwater pump could be rendered inoperable. Using NRC Inspection Manual 0609, Attachment 4, Phase 1 Initial Screening and Characterization of Findings, the finding screened to a Phase 2 significance determination because it involved a potential loss of safety function. A Phase 2 was not appropriate for this external event. The senior reactor analyst determined that the finding had very low significance. This was based on information received from the licensee indicating that the precipitation intensity required to render the turbine-driven auxiliary feedwater pump non-functional had a return frequency well below 1.0E-6/yr. In the case of clogged drains, less intense rain could affect the function of the pump, but would likely not cause a transient. A bounding risk estimate indicated that the delta core damage frequency of this scenario was less than 1.0E-7/yr. The finding was determined to have a cross-cutting aspect in the area of human performance associated with the decision-making component because operations personnel failed to verify the validity of underlying assumptions for operability decision-making. |
| Site: | San Onofre  |
|---|---|
| Report | IR 05000361/2011003 Section 1R01 |
| Date counted | Jun 30, 2011 (2011Q2) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.01 |
| Inspectors (proximate) | G Warnick J Reynoso J Tapp R Lantz Z Hollcraftc Alldredgec Osterholtz E Uribe G Guerra G Warnick J Reynoso J Tapp J Watkins N Greene P Elkmann R Lantz S Achen S Hedger Z Hollcraft |
| CCA | H.14, Conservative Bias |
| INPO aspect | DM.2 |
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Finding - San Onofre - IR 05000361/2011003 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (San Onofre) @ 2011Q2
Self-Identified List (San Onofre)
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