ENS 45025
ENS Event | |
|---|---|
21:30 Apr 27, 2009 | |
| Title | Residual Heat Removal (Rhr) Pump Tripped While in Operation for Shutdown Cooling |
| Event Description | On April 27, 2009, at approximately 1730 hours0.02 days <br />0.481 hours <br />0.00286 weeks <br />6.58265e-4 months <br />, with the plant in Mode 5 during refueling outage (RFO) 12, RHR 'A' pump tripped while operating in shutdown cooling. RHR 'A' was the primary decay heat removal shutdown cooling system. RHR 'B' was the backup decay heat removal shutdown cooling system. Preliminary investigation shows that jumper installation activities associated with plant testing resulted in a blown fuse and closure of the RHR shutdown cooling outboard common suction isolation valve (1E12F008). Closure of the 1E12F008 valve tripped the RHR 'A' pump and prevented the RHR 'B' pump from being used to initiate shutdown cooling from the control room. Operators were preparing to manually open 1E12F008 in parallel with activities to restore control from the control room.
The plant entered Technical Specification 3.9.9, 'RHR - Low Water Level', Conditions A and C due to 1E12F008 isolating causing the loss of shutdown cooling. Action A.1 calls for verification of an alternate method of decay heat removal available for each inoperable RHR shutdown cooling subsystem in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> thereafter. This was completed with the fuel pool cooling and cleanup system's two pumps and two heat exchangers cooled by NCC [Nuclear Closed Cooling System] (available due to the ability to reflood the upper pools with a hotwell pump through normal cavity reflood path) being one alternate system. A second alternate system was the utilization of the low pressure core spray to flood the vessel, returning to the suppression pool through safety relief valves, and a loop of RHR in suppression pool cooling. Actions for Condition C, to verify reactor coolant circulation by an alternate method and to monitor reactor coolant temperature were not met due to no reactor coolant flow past a valid temperature monitoring point. Approximate reactor coolant temperature was being trended using the reactor water cleanup system. The blown fuse was identified and replaced at approximately 1816 hours0.021 days <br />0.504 hours <br />0.003 weeks <br />6.90988e-4 months <br />. The RHR 'B' pump was started at approximately 1834 hours0.0212 days <br />0.509 hours <br />0.00303 weeks <br />6.97837e-4 months <br />. From the time that the RHR 'A' pump tripped (approximately 1730), until the RHR 'B' pump was started, the reactor temperature increased from 94 degrees F to 97 degrees F. Pre-determined time to boil had been calculated to be 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br />. At approximately 1835 hours0.0212 days <br />0.51 hours <br />0.00303 weeks <br />6.982175e-4 months <br />, TS 3.9.9 Condition C was exited due to the RHR 'B' shutdown cooling loop being placed in operation. This event is being reported as an event or condition that at the time of discovery could have prevented fulfillment of a safely function of structures or systems that are needed to remove residual heat under 10 CFR 50.72 (b)(3)(v)(B). The NRC Resident Inspector has been notified.
The purpose of this call is to retract Event Number 45025. On April 28, 2009, at 0055 hours6.365741e-4 days <br />0.0153 hours <br />9.093915e-5 weeks <br />2.09275e-5 months <br />, notification was made to the NRC Operations Center by the Perry Nuclear Power Plant (PNPP) reporting a condition that at the time of discovery could have prevented the fulfillment of the safety function of a system that is needed to remove residual heat [10 CFR 50.72(b)(3)(v)(B)]. Jumper installation activities associated with plant testing resulted in a blown fuse and closure of the Residual Heat Removal (RHR) shutdown cooling outboard common suction isolation valve. Closure of the valve resulted in the RHR A pump tripping, as designed. The blown fuse was replaced and the valve reopened. The RHR B subsystem was then started as the primary decay heat removal shutdown cooling system. Additionally, it was initially questioned whether Technical Specification Limiting Condition for Operation 3.9.9 Required Actions were met to verify reactor coolant circulation by an alternate method and to monitor reactor coolant temperature. Based on further evaluation, it was determined that there was not a reasonable expectation of the loss of safety function of a system needed to remove residual heat (i.e., the RHR System). The redundant RHR B subsystem was manually aligned and operated in a timely manner to continue to meet the system requirements to fulfill the safety function. Since the condition reported in Event Number 45025 would not have prevented the fulfillment of the safety function of a system that is needed to remove residual heat, the condition is not reportable, and this notification is retracted. Additionally, it was determined that verification of reactor coolant circulation by an alternate method (i.e., Reactor Water Cleanup System) was performed and that monitoring of reactor coolant temperature was appropriate. Therefore, based on not meeting any 10 CFR 50.73 reporting criteria, no Licensee Event Report is required. The evaluations (i.e., Reportability Reviews) for this condition are documented in Condition Report 09-58110 and Condition Report 09-58123. The licensee notified the NRC Resident Inspector.
The Residual Heat Removal (RHR) system common suction isolation valve 1E12-F008 received an invalid isolation signal resulting in the operating RHR A pump tripping while the system was in the shutdown cooling mode of operation. The event was reported to the NRC Operations Center on April 28, 2009 in accordance with 10 CFR 50.72(b)(3)(v)(B). The event notification was subsequently retracted on June 25, 2009. This event was reevaluated for reportability via Condition Report 10-71293 using additional guidance and enforcement history related to safety system functional failure reporting. Based on results of this evaluation, the April 27, 2009, loss of shutdown cooling event is reportable as a Licensee Event Report (LER) under 10 CFR 50.73(a)(2)(v)(B), 'Any event or condition that could have prevented the fulfillment of the safety function of structures, or systems that are needed to remove residual heat.' Perry LER 2010-001 will be submitted to report this event. The NRC Resident Inspectors have been notified. |
| Where | |
|---|---|
Perry  Ohio (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat | |
| LER: | 05000440/LER-2010-001 |
| Time - Person (Reporting Time:+3.42 h0.143 days <br />0.0204 weeks <br />0.00468 months <br />) | |
| Opened: | Thomas Morse 00:55 Apr 28, 2009 |
| NRC Officer: | Vince Klco |
| Last Updated: | Mar 10, 2010 |
| 45025 - NRC Website
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