ENS 42252
ENS Event | |
|---|---|
20:48 Jan 11, 2006 | |
| Title | Shutdown Cooling Inoperability Due to Small Discharge Header Leak |
| Event Description | On Wednesday, January 11, 2006, at approximately 1248 PST, with San Onofre Unit 2 in Mode 5 (loops not filled), Southern California Edison (SCE) declared both trains of the Shutdown Cooling (SDC) System inoperable. This action was taken following discovery and evaluation of an approximate 1.5 inch crack and minor leak (about 10 drops per minute) in a line located at the Low Pressure Safety Injection (LPSI) common discharge header (the LPSI pumps are also used as the SDC system pumps). Although both trains of the SDC system remain functional and one train is in service, SCE declared both SDC trains inoperable because the affected pipe might not be ASME Code qualified as a result of this crack.
SCE is conservatively reporting this event in accordance with 10CFR50.72(b)(3)(v)(B) as a condition that could prevent the remove residual heat. SCE is continuing to evaluate this condition. SCE is following the actions required by Technical Specifications 3.4.8, and will repair the pipe crack during the current refueling outage, after the reactor core has been off-loaded to the spent fuel pool. SCE expects to place the plant in Mode 6 tomorrow. At the time of this report, Unit 2 is in Mode 5 and Unit 3 is in Mode 1 at 100% power. The NRC Senior Resident Inspector, NRC Region IV, and the Nuclear Reactor Regulation Project Manager have been briefed of this event and will be provided with a copy of this report. Shutdown cooling has been running for approximately one week and the leak was initially discovered sometime on 01/10/06 during an inspection in which Boric acid accumulation was discovered . A work request was written to perform a more thorough inspection that was performed on 01/11/06. The crack is on an 8 inch line that returns to RCS Loop 2A which is normally isolated during high pressure shutdown conditions and reactor power operation.
On January 11, 2006, Southern California Edison (SCE) reported to the NRC that both trains of Shutdown Cooling System (SDC) were inoperable at San Onofre Unit 2 due to a through-wall crack in a pipe in the common discharge header. That occurrence was reported to the NRC in accordance with 10CFR50.72(b)(3)(v)(B) for a condition that could prevent the removal of residual heat. SCE has since analyzed the pipe integrity at the design basis conditions and determined the pipe would have remained intact and that system leakage through the crack would have remained below the allowable system leak rate. Based on these results, SCE concluded that the pipe was capable of performing its safety functions under design basis conditions. Because the system was always capable of performing its safety function, SCE is retracting the January 11, 2006 report. Nevertheless, SCE plans to submit a voluntary licensee event report to document this event and inform the NRC of the corrective actions taken. At the time of this phone call, Unit 2 was in the middle of the Cycle 14 refueling outage and Unit 3 was at about 100 percent power. SCE has notified the NRC resident inspectors about this retraction and will provide them with a copy of this report. Notified R4DO (J. Whitten) |
| Where | |
|---|---|
San Onofre  California (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat | |
| LER: | 05000361/LER-2006-001 |
| Time - Person (Reporting Time:+-0.08 h-0.00333 days <br />-4.761905e-4 weeks <br />-1.09584e-4 months <br />) | |
| Opened: | Julie Holt 20:43 Jan 11, 2006 |
| NRC Officer: | Jeff Rotton |
| Last Updated: | Mar 3, 2006 |
| 42252 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |
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 | |