05000461/FIN-2005006-01
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Finding | |
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| Title | Evaluation of Fire Induced Circuit Failures in HPCS System Control Logic |
| Description | The team identified an Unresolved Item (URI) associated with potential fire-induced electrical circuit failures in the HPCS system. The team postulated a fire in the Division III switchgear room, located in Fire Zone CB-5a, which could result in fire-induced electrical circuit faults in the control cables and control logic of the HPCS pump and discharge valve. Such faults could potentially impair the capability to shut off the pump and stop it from continually injecting into the core. The team reviewed the methodology used by the licensee during the performance of Clintons post-fire safe shutdown circuit analysis to determine if it was consistent with NRC Regulatory Issue Summary (RIS) 2004-003, Revision 1, Risk- Informed Approach for Post-Fire Safe-Shutdown Circuit Inspections, issued on December 29, 2004. The team attempted to determine, based on available safe shutdown circuit analysis documentation (calculations, design drawings) used to perform the circuit analyses, if the licensee considered in their analysis circuit configuration failure scenarios such as multiple concurrent spurious component actuations due to fire induced cable shorts. The licensee stated that the fire induced cable failure mechanism was considered within the CPS Appendix R analysis, and therefore exceeded the RIS cable failure considerations. The team performed a sample review of post-fire safe shutdown circuit analysis, using the guidance and criteria provided in the RIS. The licensee documented in calculation IP-0532, 10 CFR Part 50, Appendix R, Compliance Assessment, that any and all spurious operations or failures shall be evaluated and that the spurious actuations or failures are not required at the time to be evaluated simultaneously except for high/low pressure interface components. However, the licensee stated that they did consider the potential for concurrent/simultaneous spurious actuations or failures in the Appendix R analysis for the ECCS system automatic initiation instrumentation logic network as well as the high/low pressure interface components. The team noted that no documentation was available for review to demonstrate that the licensee had evaluated the potential fire induced electrical circuit failures scenarios, postulated by the team, in the HPCS logic control system. The team evaluated fire induced circuit failures in the HPCS system that could potentially impact safe shutdown. The team selected HPCS pump 1E22-C001 and pump discharge valve 1E22-F004 logic circuitry and associated control cables for evaluation. The team reviewed licensing and design basis documents and related operating, emergency and shutdown procedures. The team performed a circuit analysis and evaluation using the following design drawings to determine CPSs compliance with their licensing basis and the approved fire protection program: E02-1HP99, Sheet 110, Schematic Diagram, High Pressure Core Spray (HP) HPCS Power Supply System (1E22-1070), Revision H; E02-1HP99, Sheet 501, Schematic Diagram, High Pressure Core Spray (HP) HPCS Suction Valve (1E22-F001) and HPCS Suct. Disc. Valve 1E22-F004, Revision J; E02-1AP03, Electrical Loading Diagram, Revision AA; M05-1074, P&ID High Pressure Core Spray (HP), Revision AG; CPS-SSD-LOG-217, Sheet 1, Division 3 Diesel Generator & Electrical Distribution Safe Shutdown Logic Diagram, Revision 2; and CPS-SSD-LOG-101, Sheet 1, High Pressure Core Spray Safe Shutdown Logic Diagram, Revision 2. The team conducted an evaluation of the impact of fire induced faults on HPCS system operation. The team postulated the following fire induced electrical faults, using guidance provided in the RIS, which could result in the HPCS discharge valve opening and the HPCS pump continually running and injecting water into the Reactor: HPCS Discharge Valve 1E22-F004 (Control Cable 1HP11C (12/c)): One hot short in the opening control logic circuitry of the valve, and one short to ground in the closing control logic circuitry of the valve. HPCS Pump 1E22-C001 (Control Cable 1HP08C (15/c)): One hot short in the breaker closing control logic circuitry of the HPCS pump which will close the pump breaker and start the pump, and two shorts to ground in the tripping circuitry of the pump control logic which will result in a blown fuse, and prevent tripping of the pump breaker. (Note that if the hot short stays in for 20 minutes then there is no need to postulate the faults in the tripping circuitry). The team determined that no documented evidence was available to indicate that the licensee considered the potential hot shorts, shorts to ground and open circuits, postulated by the team, in the multi-conductor control cables used in the control system of HPCS pump 1E22-C001 (15/c) and pump discharge valve 1E22-F004 (12/c). On June 8, 2005, the licensee, RIII, and NRR fire protection staff members conducted a conference call to further discuss the concerns raised by the team. The NRC requested that the licensee evaluate the postulated scenarios provided by the team and determine if CPS can achieve and maintain safe shutdown in Fire-Zone CB-5a if HPCS injection cannot be stopped and if CPS is within their licensing basis considering the electrical faults and fire induced actuations of HPCS components. The licensee provided their response to the NRC on June 20, 2005. The licensee entered this issue in their corrective action program under CR 00343489, dated June 13, 2005. This issue is considered an unresolved item (URI) pending NRC review of the licensees response to the issues raised by the team |
| Site: | Clinton  |
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| Report | IR 05000461/2005006 Section 4OA5 |
| Date counted | Jun 30, 2005 (2005Q2) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | |
| Inspectors (proximate) | Z Falevits A Klett J Robbins B Jose J Larab Kemkerc Brown D Lords D Szwarc J Bozga J Cassidy M Ring R Orlikowski S Bell S Mischke |
| INPO aspect | |
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Finding - Clinton - IR 05000461/2005006 | |||||||||
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Finding List (Clinton) @ 2005Q2
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