05000361/FIN-2011004-02
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Finding | |
|---|---|
| Title | Failure to Provide Adequate Flood Protection for the Auxiliary Feedwater Steam Supply Piping |
| Description | The inspectors identified a noncited violation of 10 CFR Part 50, Appendix B, Criterion III, Design Control, for failure to translate applicable regulatory requirements and the design basis into specifications, drawings, procedures, and instructions. The Updated Final Safety Analysis Report, states, in part that, In the extreme event that the thunderstorm PMP occurs, no safety-related equipment will be impacted by flooding, since, Drainage water in the structures which entered from other areas (e.g. from roofs, open areas) will not reach safety-related equipment. Specifically, from original construction until adequate compensatory measure were implemented on May 5, 2011, the steam supply piping to the auxiliary feedwater pump turbine was not adequately protected from all postulated flood levels and conditions, such that, in the extreme event that the thunderstorm probable maximum precipitation occurs, water could have reached the steam supply pipe resulting in steam condensation inside the pipe which could impact auxiliary feedwater pump operability. The compensatory measures will remain in place until the design nonconformance is resolved. This issue was entered into the licenseei12s 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. Using NRC Inspection Manual 0609, Attachment 4, Phase 1 i12 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. No crosscutting aspect was identified because this issue is not reflective of current performance, since this condition has existed since construction |
| Site: | San Onofre  |
|---|---|
| Report | IR 05000361/2011004 Section 1R15 |
| Date counted | Sep 30, 2011 (2011Q3) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.15 |
| Inspectors (proximate) | R Lantz J Reynoso G Warnick E Ruesch S Achen |
| INPO aspect | |
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Finding - San Onofre - IR 05000361/2011004 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (San Onofre) @ 2011Q3
Self-Identified List (San Onofre)
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