ENS Event | |
|---|---|
18:14 Dec 23, 2009 | |
| Title | Loss of Rhr Cooling Capability Due to Isolation of the Spent Fuel Pool Cooling Heat Sink |
| Event Description | This is a late eight hour report submitted under 10CFR50.72(b)(3)(v), 'Loss of Safety Function to (B) Remove Residual Heat'
On December 23, 2009 at about 0957 PST, with SONGS Unit 2 defueled for the Cycle 16 refueling outage, a decrease in salt water cooling flow to the Train A Component Cooling Water Heat Exchanger indicated debris was entering the system. The loss of flow appears to have been caused by debris entering the system through a failed pump suction screen. At 1014 PST operators removed the heat exchanger from service for approximately one hour to reverse the salt water cooling flow though the heat exchanger and clear the debris. The Train B cooling system had previously been removed from service for scheduled maintenance, relying on the single Train A heat exchanger to supply cooling to the Spent Fuel Pool cooling system. Salt water cooling flow was fully restored at approximately 1118 PST. Operators conservatively declared the Spent Fuel Pool Cooling System inoperable and maintained compliance with the conditions of Licensee Controlled Specification 3.7.106. Time to exceed the 160 degree Fahrenheit allowable pool temperature was estimated at over twenty three hours. It has been determined that the temporary isolation of the heat sink from the spent fuel pool constituted a loss of safety function for residual heat removal. Therefore SCE is reporting this occurrence as a loss of safety function in accordance with 10 CFR 50.72(b)(3)(v). The safety significance of this event was minimal. Flow reversal to clear ocean debris from the heat exchangers is a routine procedurally controlled evolution and bounded by design calculations which consider post-accident heat loads with a full core offload in the spent fuel pool. These actions are within the limits of both the Technical Specifications and Licensee Controlled Specifications. The licensee will inform the NRC Resident Inspector. |
| Where | |
|---|---|
San Onofre  California (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat | |
| Time - Person (Reporting Time:+384.02 h16.001 days <br />2.286 weeks <br />0.526 months <br />) | |
| Opened: | Leon Rafner 18:15 Jan 8, 2010 |
| NRC Officer: | Steve Sandin |
| Last Updated: | Jan 8, 2010 |
| 45616 - NRC Website
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WEEKMONTHYEARENS 456162009-12-23T18:14:00023 December 2009 18:14:00
[Table view]10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Loss of Rhr Cooling Capability Due to Isolation of the Spent Fuel Pool Cooling Heat Sink ENS 422522006-01-11T20:48:00011 January 2006 20:48:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Shutdown Cooling Inoperability Due to Small Discharge Header Leak 2009-12-23T18:14:00 | |