05000346/FIN-2008004-01
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Finding | |
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| Title | Inoperability of Component Cooling Water Train 1 Ventilation |
| Description | The inspectors determined that an unresolved item (URI) existed concerning the past operability of component cooling water (CCW) train 1 due to issues with the ventilation fan, MC75-1, provided for that equipment train. On September 10, 2008, during a maintenance planning walkdown for future work, licensee personnel observed that the ventilation fan MC75-1 was running in the reverse direction. This would cause the fan to deliver, when required, less than the design ventilation flow rate and would also cause the ventilation supply to be from a source that could be hotter than the design source. This condition apparently existed since a maintenance activity in March 2006 and was not discovered until the maintenance planning walkdown. Description: The plant has two trains of component cooling water with one pump and heat exchanger dedicated to each train. The plant additionally has a third pump and heat exchanger that can be aligned for use in either train thus permitting the dedicated equipment to be made available for maintenance. The pumps and the heat exchangers are located in one room. That room has a ventilation system for maintaining temperatures within a band that would not cause inoperability of the pumps or heat exchangers or associated valves within the room. That ventilation system was composed of Train 1 ventilation components and Train 2 components. Each train has its own fan and associated ventilation dampers. Each ventilation fan, when running, draws outside air into the room and then can either fully or partially discharge the heated air into the heater bay of the turbine building. The ventilation dampers were setup to permit recirculation of part of the fan discharge. With the fan running in the reverse direction, less than design flow will be produced and air from the heater bay of the turbine building can be drawn into the room. The heater bay air temperature can be higher than the maximum temperature of the outside air assumed in the system design. Licensees procedure DB-OP-6513, Auxiliary Building Non-Radioactive Areas Ventilation, stated that the CCW room ventilation systems are required support systems for their respective CCW trains. It further stated that if a train of CCW room ventilation becomes inoperable the respective CCW train shall also be declared inoperable. Licensee personnel, during a walkdown for planning upcoming maintenance activities, found that air from CCW Train 1 ventilation dampers was flowing in the wrong direction. Once it was determined that the Train 1 fan was running in the reverse direction, the licensee declared Train 1 CCW ventilation and CCW Train 1 inoperable. Operability was restored as documented in Section 4OA3 of this report. The licensee determined that the condition with the Train 1 CCW ventilation most likely existed since March 2006. The condition existed longer than the inoperability time permitted by the licensees Component Cooling Water Technical Specifications for modes the plant operated in since 2006. The licensee had several existing calculations that potentially indicated that the reverse flow was sufficient for cooling of the CCW system under design accident conditions. The licensee developed a calculation that specifically looked at the ability of the Train 1 ventilation system, with reverse flow, to cool CCW Train 1 under accident conditions. That calculation was provided to the inspectors after the end of the inspection period. Therefore, this issue is considered an unresolved item (URI 05000346/2008004-01) pending completion of inspector review of the past operability evaluation and determination of risk significance |
| Site: | Davis Besse  |
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| Report | IR 05000346/2008004 Section 1R15 |
| Date counted | Sep 30, 2008 (2008Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.15 |
| Inspectors (proximate) | M Wilk J Jacobson T Bilik G Wright J Rutkowski A Wilson T Go C Acosta Acevedoj Cameronc Zoiad Mcneil R Winter J Jacobson M Garza J Rutkowski A Wilson T Go J Cameron R Murray |
| INPO aspect | |
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Finding - Davis Besse - IR 05000346/2008004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Davis Besse) @ 2008Q3
Self-Identified List (Davis Besse)
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