05000250/FIN-2007006-01
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Finding | |
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| Title | Halon Concentration in Fire Zones 108A and 108B May Not Be Adequate |
| Description | The team identified an unresolved item (URI) because the licensee had not determined with sufficient certainty, by calculation or test, the leakage rate of Halon from FZs 108A or 108B. Therefore, there was uncertainty as to whether the required 5 percent concentration could be held for 10 minutes throughout the protected volume. The Turkey Point Fire Protection Program Report states that the Halon system for the inverter rooms (FZ-108A & FZ-108B) is capable of maintaining a concentration above 5 percent, by volume, for 10 minutes even with continued operation of the HVAC systems. This criteria is consistent with NFPA 12A requirements for suppressing a surface fire. The licensee could not produce a calculation or test results which demonstrated that this requirement could be met. Cognizant licensee engineers stated that the initial design accounted for leakage by assuming an opening in the room envelope equal to 1 percent of the envelope surface area. Applying formula 2-5.2 from NFPA 12A and using the original design basis value for weight of Halon in the storage tanks, the team calculated that the initial concentrations of Halon in FZs 108A and 108B would be 6.6 percent and 6.5 percent, respectively. Leakage could not be estimated with sufficient accuracy during the time frame of the inspection since it involved leakage past closed fire dampers driven by fans. After the inspection, the licensee developed and transmitted to the team calculation PTN-BFSM-07-001, Halon Reconstitution for Concentration in Fire Zones 108A & 108B, dated March 5, 2007. This calculation was aimed at reconstituting the type of calculation that would have been performed by the system vendor in 1985. It used calculation methods contained in NFPA 12A-1980. The calculation determined the initial concentration necessary to account for density driven leakage through openings with the assumption of efficient air/Halon mixing, i.e. in leakage of fresh air does not accumulate in the upper portions of the room. It concluded that approximately 0.5 percent concentration would be lost due to density driven leakage which means that 5.5 percent initial concentration would be sufficient to meet system requirements. The calculation further concluded that because the initial concentration was about 6.5 percent, there was a 1 percent margin with regard to initial concentration. This margin would compensate for fan driven leakage past nominally closed dampers. However, fan driven leakage into and out of the room was not quantified in the PTNBFSM- 07-001 calculation. The PTN-BFSM-07-001 calculation was not accepted by the team as resolving the issue for two reasons. First, the assumption of efficient air/Halon mixing does not appear to be valid because efficient mixing requires fans be installed for that purpose which the room does not have; and second, it is not obvious that fan driven leakage would be insignificant. Calculations by the team, based on estimated values, indicate that both fan driven leakage and stratification of concentrations (or lack of efficient mixing) need to be addressed in a quantified fashion. For these reasons, the team could not make a conclusion as to whether maintaining 5 percent concentration for 10 minutes was achievable in Fire Zones 108A and 108B. Therefore, the matter is identified as URI 05000250, 251/2007006-01, Halon Concentration in FZs 108A and 108B May Not Be Adequate. |
| Site: | Turkey Point  |
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| Report | IR 05000250/2007006 Section 1R05 |
| Date counted | Mar 31, 2007 (2007Q1) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.05 |
| Inspectors (proximate) | D Payne J Quinones L Bradford M Thomas P Fillion B Mellyp Fillionm Barillas J Stewart M Sykes A Vargas-Mendez |
| INPO aspect | |
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Finding - Turkey Point - IR 05000250/2007006 | |||||||||||||
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Finding List (Turkey Point) @ 2007Q1
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