05000338/FIN-2012012-01
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Finding | |
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| Title | Loss of Service Water for a Postulated Fire in Unit 1 ESWGR |
| Description | The SSD methodology described in the NAPS Appendix R Report for a postulated fire in FA 6-1 credited alternative shutdown capability by using Unit 2 charging pumps (via a manual cross-tie between Unit 1 and Unit 2) and the Unit 2 SW pumps to achieve post-fire SSD for the fire-affected Unit 1 and the unaffected Unit 2. The NAPS SW system is shared between Units 1 and 2 and has a combined total of four SW pumps. The inspectors reviewed cable routing information for the SW pumps, and noted that control cables for all four SW pumps were routed through FA 6-1. During further review of the SW pump circuits and discussions with licensee personnel, it was determined that a postulated fire in the Unit 1 ESWGR could potentially affect the SW pumps control circuits in Unit 2. A fire in the Unit 1 ESWGR could create a hot short in the control circuit cables located in the fire affected Unit 1 ESWGR that could energize the trip coil for the SW pumps of the unaffected Unit 2. The hot short could potentially shut down the running SW pumps and prevent the other SW pumps from starting. This could prevent the unaffected Unit 2 SW pumps from providing SW flow for both the fire affected Unit 1 and the unaffected Unit 2. The inspectors determined that, by not ensuring the credited SW pumps remained free of fire damage, the licensee failed to ensure that alternative shutdown capability would be maintained for a postulated fire scenario in FA 6-1. This condition may not be in compliance with 10 CFR 50, Appendix R, Sections III.G.3 and III.L.1. This issue was discussed with licensee personnel who initiated CR 500152 to assess this service water pumps control circuit vulnerability. The licensee determined that this condition was only possible during a postulated fire in either units ESWGR. Subsequent to the onsite inspection, the licensee documented its Reasonable Assurance of Safety (RAS) for this issue in CR 500152-RAS 219. The licensee indicated in RAS 219 that it was unlikely that one fire would adversely affect the emergency busses on the fire affected Unit 1 as well as the conduit for the unaffected Unit 2 SW pumps such that a loss of all four SW pumps would occur. The licensee implemented hourly roving fire watches in each units ESWGR while this issue was being evaluated. This issue is unresolved pending further NRC review of the licensees information and assessment to determine if a credible fire scenario could result in the loss of all four service water pumps due to a single fire in the Unit 1 ESWGR. This issue is identified as URI 05000338, 339/2012012-01, Loss of Service Water for a Postulated Fire in Unit 1 ESWGR. |
| Site: | North Anna  |
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| Report | IR 05000338/2012012 Section 1R05 |
| Date counted | Dec 31, 2012 (2012Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.05 |
| Inspectors (proximate) | M Thomas R Carrion G Mccoy G Macdonald R Clagg R Temps G Kolcum A Sengupta B Tripathim Kingm Thomas G Wiseman J Montgomery D Mas |
| INPO aspect | |
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Finding - North Anna - IR 05000338/2012012 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (North Anna) @ 2012Q4
Self-Identified List (North Anna)
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