05000338/FIN-2009008-02
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Finding | |
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| Title | Failure to Adequately Address the Potential for CO2 Over-Pressurization Within the Unit 2 Cable Vault & Tunnel |
| Description | The inspectors identified a Green non-cited violation (NCV) of North Anna Nuclear Station Operating License Condition 2. (D), Fire Protection, in that the licensee failed to adequately address the potential for carbon dioxide (CO2) overpressurization within Fire Area (FA) 3-2, the Unit 2 Cable Vault & Tunnel (CV&T).The team determined that adequate CO2 venting did not exist, resulting in the potential failure of the CO2 gas boundary. This condition had the effect of allowing gas migration from the CV&T (Zone 2-2) into the CV&T electrical penetration room(Zone 2-4) due to the failure of the door between the two areas to remain closed. The licensee entered and tracked this issue in the corrective action program via Condition Report (CR) 019539, and Apparent Cause Evaluation, ACE000693.This finding is a performance deficiency because the licensee did not consider the potential for CO2 over-pressurization within the Unit 2 CV&T (FA 3-2) according to the applicable industry code of record for the facility. The finding is more than minor because the CO2 system is required to provide primary suppression coverage for the Cable/Tunnel area of Fire Area 3-2, and the finding is associated with the reactor safety, mitigating systems, cornerstone attribute of protection against external factors, (i.e. fire), and it substantially affects the objective of ensuring reliability and capability of systems that respond to initiating events. The inspectors assessed the finding using Inspection Manual Chapter (IMC) 0609, Appendix F, Fire Protection Significance Determination Process. The finding was assigned a low degradation rating since the issue screened as very low in the SDP Phase 2 evaluation. This was the case because the only creditable ignition sources in the CV&T are transients which are administratively controlled. Also, the safe shutdown analysis (SSD) already assumes that all cables in the CV&T are damaged; therefore a gas boundary failure within the fire area would affect the fire suppression component of defense-in depth only and not the capability to safely shutdown. In addition, the CO2 system was backed up by a manual sprinkler system and a manual deluge system. The inspectors reviewed guidance contained in IMC 0305 to determine if any crosscutting aspects existed. The inspectors concluded that because the licensees failure to address the potential for CO2 over-pressurization in the Unit 2 CV&T (FA 3-2) resulted from lack of original CO2 test data and occurred during initial plant startup, it did not reflect current licensee performance and no cross-cutting aspect was identified. (Section 1R05.03 |
| Site: | North Anna  |
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| Report | IR 05000338/2009008 Section 1R05 |
| Date counted | Dec 31, 2009 (2009Q4) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.05 |
| Inspectors (proximate) | N Merriweather R Rodriguez G Wiseman R Fanner R Nease J Montgomery P Braxton L Castelli |
| INPO aspect | |
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Finding - North Anna - IR 05000338/2009008 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (North Anna) @ 2009Q4
Self-Identified List (North Anna)
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