ENS 42451
ENS Event | |
|---|---|
08:01 Mar 29, 2006 | |
| Title | Unit 3 Shutdown Due to Potential Safety Injection Tank Gasket Issue |
| Event Description | On March 27, 2006, with Unit 2 in Mode 4 while starting up from a refueling outage, [Southern California Edison (SCE)] discovered that the gasket used to seal the manway cover for Safety Injection Tank (SIT) T-008 had become partially dislodged. The gasket is a 'flexitalic' type gasket which consists of a long section of crushable wire that is coiled and compressed between the manway cover and the safety injection tank flange. For SIT T-008, the flexitalic gasket had uncoiled and extended down into the SIT and prevented SIT outlet check valve MU040 from fully sealing in the closed position. On March 28, SCE inspected the remaining three SITs (SITs # 007, 009 and 010) and found the flexitalic gaskets degraded but intact and not interfering with other components.
When this condition was discovered at Unit 2, San Onofre Unit 3 was operating at approximately 100 percent power. Similar flexitalic gaskets are also used for the manway covers on the four SITs at Unit 3. At 0001 PST on March 29, 2006, SCE conservatively declared both trains of the emergency core cooling system at Unit 3 inoperable. This placed Unit 3 in a TS 3.0.3 shutdown action statement. Plant Operators began the required Unit 3 shutdown at about 0050 on March 29, 2006. SCE is providing this phone notification to the NRC in accordance with 10 CFR 50.72(b)(2)(i) for the initiation of any nuclear plant shutdown required by the plant's Technical Specifications. The electric grid in the area is stable and Emergency Diesel Generators are available on Unit 3. There is no maintenance being performed on systems required for shutdown on Unit 3. The licensee notified the NRC Resident Inspector.
On March 29, 2006, SCE reported the initiation of the shutdown to the NRC Operations Center (Event Log No. 42451). At the time, SCE was concerned that if the gaskets were uncoiled they might have interfered with operation of the ECCS. After completing the plant shutdown, SCE inspected and found the gaskets degraded but not extending into the SIT and its discharge piping. In addition, subsequent evaluations by the SONGS NSSS vendor Combustion Engineering (now Westinghouse) determined the degraded gaskets (even if uncoiled and interfering with SIT outlet check valve from fully closing) would not have prevented the ECCS from performing its required safety function. Consequently, SCE was not required to declare Unit 3 ECCS inoperable and SCE is retracting the phone report to the NRC (Event Log No. 42451). SCE will submit a voluntary LER to document this condition. At the time of this report, Unit 2 and Unit 3 are in Mode 1 at approximately 100% power. The San Onofre Resident Inspector has been notified of this event and will be provided with a copy of this report. Notified the R4DO (Spitzberg). |
| Where | |
|---|---|
San Onofre  California (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | |
| Time - Person (Reporting Time:+-1.45 h-0.0604 days <br />-0.00863 weeks <br />-0.00199 months <br />) | |
| Opened: | Julie Holt 06:34 Mar 29, 2006 |
| NRC Officer: | Pete Snyder |
| Last Updated: | May 30, 2006 |
| 42451 - NRC Website
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Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (50 %) |
WEEKMONTHYEARENS 455642009-12-12T09:26:00012 December 2009 09:26:00
[Table view]10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Unusual Event Declared Due to Both Emergency Diesel Generators Being Inoperable ENS 444562008-09-01T17:35:0001 September 2008 17:35:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Shutdown Due to Emergency Diesel Generator Shorting Ring Cracks ENS 440922008-03-25T15:40:00025 March 2008 15:40:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Plant Shutdown Initiated Due to Degraded Battery Voltage ENS 424512006-03-29T08:01:00029 March 2006 08:01:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Unit 3 Shutdown Due to Potential Safety Injection Tank Gasket Issue ENS 414102005-02-15T05:55:00015 February 2005 05:55:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Tech Spec Required Shutdown ENS 403962003-12-17T11:15:00017 December 2003 11:15:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Technical Specification Required Shutdown Due to Loss of Both Trains of Safety Injection 2009-12-12T09:26:00 | |