05000461/FIN-2009004-01
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Finding | |
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| Title | Interconnecting Floor Drains Between the Residual Heat Removal A Pump Room and Radwaste Pipe Tunnel |
| Description | The inspectors identified that floor drains in the RHR A Pump Room and the Radwaste Pipe Tunnel were apparently interconnected, which would potentially result in an unanalyzed condition. This issue is considered to be an Unresolved Item pending additional review by the licensee and the inspectors. During review of plant drawings for floor drain system piping in the Emergency Core Cooling System (ECCS) and Reactor Core Isolation Cooling Pump Rooms on the 7070 elevation of the Auxiliary Building, the inspectors identified that floor drains in the RHR A Pump Room appeared to be connected via permanent 4 pipe embedded in the floor to floor drains in the Radwaste Pipe Tunnel, which is located along the western wall of the (adjacent) Control Building at the 7200 elevation. The inspectors noted that each of the separate pump rooms was supposedly designed to be isolated from other areas of the plant and not susceptible to flooding from sources external to the pump rooms. The inspectors discussed this floor drain configuration with the licensee and questioned the adequacy of the design with respect to the potential for flooding. First, if the Radwaste Pipe Tunnel were to flood, would the floodwater in the Tunnel communicate with and cause flooding in the RHR A Pump Room? This could potentially affect operability of the RHR A pump. Second, if the RHR A Pump Room were to flood because of a postulated pump suction line break, would the suppression pool flood water escape the RHR A Pump Room and flow into the radwaste system via the Radwaste Pipe Tunnel? The inspectors noted that Section 3.8.4.1.1 of the UFSAR stated that the ECCS Pump Rooms are in flood protection compartments with watertight doors. In the event of a pipe rupture, the flooding in one compartment will not result in the flooding of any other compartment, and the failure of a pump suction line will not drain the suppression pool. Section D3.6.4 of the UFSAR stated that a postulated failure of any of the non-isolable portions of the ECCS pump suction lines to the suppression pool could result in flooding of a single ECCS cubicle to the high water level in the suppression pool (7315 elevation). If the floor drain piping exists as described by plant drawings and flooding in the RHR A Pump Room (from the suppression pool) were to occur, then the potential exists that cross-flooding could occur between the RHR A Pump Room and the Radwaste Pipe Tunnel. Flooding could potentially continue until the suppression pool level was below the Control Building floor drain level (7206 elevation). This would be below the suppression pool high water level assumed in Section D3.6.4. At the end of the inspection period, the licensee had just begun investigating the inspectors questions and evaluating the condition. Inspection of the Radwaste Pipe Tunnel found that the floor drains in question were not plugged. No logbook entries were found in the Floor Drain Plug Log to indicate that the drains had been plugged at anytime in the past. The vertical piping which connects the floor drains from the Radwaste Pipe Tunnel to the RHR A Pump Room travels through the Low Pressure Core Spray Pump Room. This pipe was located as mapped on drawing A26-1000-03A at plant coordinates V-124 and the pipe was intact. No historical design change documents were posted against the plant drawings to indicate that the configuration was altered from the original plant design. Original engineering calculation (3C10-0485-001) and the 1990 Flood Analysis did not specifically discuss the potential for flood water entering (or leaving) the RHR A Pump Room via this drain line, although a statement was included which identified that flood water flow through 4 floor drain lines could be estimated at 100 gallons-per-minute (0.22 cubic feet-per-second). During review, the licensee also discovered that a similar arrangement existed with floor drains on the west side of the Auxiliary Building in that the RHR C Pump Room floor drain piping communicates with the floor drains in the Auxiliary Building Floor Drain Tank Room and Pump Room. Those rooms are located south of the RHR C Pump Room on the other side of the watertight door, at the 7120 elevation. To address the potential immediate operability concern, the licensee plugged the two floor drains in the Radwaste Pipe Tunnel to prevent communication with the floor drain system in the RHR A Pump Room per an engineering design change. This issue is considered to be an Unresolved Item (URI 05000461/2009004-01) pending additional review and resolution of open questions |
| Site: | Clinton  |
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| Report | IR 05000461/2009004 Section 1R06 |
| Date counted | Sep 30, 2009 (2009Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.06 |
| Inspectors (proximate) | M Holmberg R Jickling R Langstaff J Cassidy B Metrow B Kemker M Ring S Mischke D Lords E Coffman J Draper A Scarbeary D Sandb Kemkerd Lords D Melendez Colon E Coffman J Cassidy M Mitchell M Ring R Russell S Mischkea Scarbearyb Kemker D Lords J Bozga M Mitchell M Ring S Mischke |
| INPO aspect | |
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Finding - Clinton - IR 05000461/2009004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Clinton) @ 2009Q3
Self-Identified List (Clinton)
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