ENS 41798
ENS Event | |
|---|---|
11:17 Jun 26, 2005 | |
| Title | Edg Inoperable Due To Loose Electrical Connection |
| Event Description | On June 25, 2005, at about 1335 PDT, during a test of Unit 3 Emergency Diesel Generator (EDG) 3G003, Emergency Supply Fan 3A276 did not start. SCE's investigation found a loose electrical connection at the thermal overload auxiliary switch contact for that fan. A similar condition was found on Emergency Supply Fan 3A277. SCE declared 3G003 inoperable and initiated a common cause investigation required by the EDG Technical Specifications. SCE tightened the affected electrical connections and after successfully start testing 3G003, declared 3G003 operable at 0406 PDT on June 26, 2005.
On June 26, 2005, at about 0417 PDT, SCE found similar loose connections for EDG 3G002. Components affected were the EDG radiator fan and an EDG Emergency Supply Fan. Because SCE could not conclusively determine if the loose connections would have caused 3G002 to be inoperable, SCE conservatively declared 3G002 inoperable. (SCE currently plans to start test the Unit 2 EDGs today to confirm the Unit 2 EDGs remain operable.) Because it appears that both Unit 3 EDGs could have been inoperable at the same time, SCE is reporting this occurrence in accordance with 10CFR50.72(b)(3)(v)(D) as an event or condition that could have prevented fulfillment of a safety function. At the time of this occurrence, Unit 2 was operating at about 99 percent power and Unit 3 was at about 100 percent power. SCE has notified the NRC Resident Inspectors about this occurrence and will provide them with a copy of this report.
On June 26, 2005, SCE reported to the NRC that both Unit 3 emergency Diesel Generators (EDGs) were conservatively declared inoperable at the same time. SCE reported that occurrence to the NRC in accordance with 10CFR50.72(b)(3)(v)(D) for the loss of a safety function. SCE has since determined that both EDGs were operable in the as found condition and that a report to the NRC was not required and SCE is retracting that report. For EDG 3G003, even though one of two emergency supply fans did not function, SCE confirmed by calculation that the remaining emergency supply fan was sufficient. That is, 3G003 was capable of performing its specified safety function with only one emergency supply fan operating. For EDG 3G002, the electrical connections that were reported to be 'loose' did not prevent circuit continuity and did not degrade the operability of the EDG. 3G002, therefore remained operable. Because the EDGs were operable, no report was required. SCE is retracting the June 26, 2005 report. SCE will, however, 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 operating at about 99 percent power 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. R4DO (Smith) was notified. |
| Where | |
|---|---|
San Onofre  California (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+3.58 h0.149 days <br />0.0213 weeks <br />0.0049 months <br />) | |
| Opened: | Clay Williams 14:52 Jun 26, 2005 |
| NRC Officer: | Bill Gott |
| Last Updated: | Aug 23, 2005 |
| 41798 - NRC Website
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Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
San Onofre with 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
WEEKMONTHYEARENS 456282010-01-13T19:25:00013 January 2010 19:25:00
[Table view]10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Wrong Train of Emergency Core Cooling System Removed from Service ENS 442472008-05-29T18:36:00029 May 2008 18:36:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Offsite Power Below 59.7 Hz ENS 442272008-05-20T20:10:00020 May 2008 20:10:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Offsite Power Grid Disturbance ENS 423102006-02-04T02:15:0004 February 2006 02:15:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Offsite Power Not within Specifications ENS 417982005-06-26T11:17:00026 June 2005 11:17:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Edg Inoperable Due to Loose Electrical Connection ENS 408182004-06-14T14:41:00014 June 2004 14:41:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Licensee Declared Offsite Power Inoperable Due to Dip in Grid Frequency 2010-01-13T19:25:00 | |