ML121170395
| ML121170395 | |
| Person / Time | |
|---|---|
| Site: | Oconee, Summer, Turkey Point, Clinton, San Onofre  |
| Issue date: | 06/14/2011 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| FOIA/PA-2011-0157 | |
| Download: ML121170395 (4) | |
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NRR -@OECommunity Page 1 of 4
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-l Continual Learning Through Knowledge Sharing Search I How to Subscribe Login June 14, 2011 OE Home > Forum > All Communications Information Security Reminder Information Security Reminder: OpE COMMs contain preliminary information in the interest of timely internal communication of operating experience. OpE COMMs may be pre-decisional and may contain sensitive information.
They are not intended for distribution outside the agency.
Page: 1 Joseph Giantelli (6/23/2009 9:30:19 am)
Revised on 6/23/2009 3:17:40 pm San Onofre 3 - EDG Failed To Start During a Slow Start Sequence for Monthly Surveillance On Tuesday June 9, 2009, 3A emergency diesel generator failed to start during a "slow" start sequence. The licensee stated that the cause involves a degraded Direct Current (DC) power supply. The degraded output is apparently not stable and causes signals to be "rippled".
The residents are still reviewing this event for a performance deficiency. The licensee has restored the Unit 3 Train A emergency diesel generator after replacement of the DC annuciator power supplies. Based on previous internal OE the licensee informed the resident inspectors that they had been replacing the power supplies on a preventative maintenance interval of every 8-years, since the electrolytic capacitors were known to degrade over time.
The electrolytic capacitors are part of the power supply AC filter circuit. According to the licensee, the failed power supplies (including capacitors), were last replaced about 4 years ago, in October 2005. The Turkey Point OE suggests every 10 year replacement.
On Saturday June 13, during the extent of condition evaluation, the licensee reported "minor" periodic DC voltage spikes on Unit 2 Train A emergency diesel generator. The Unit 2 Train A power supplies were reportedly replaced in April 2007. A successful fast start of the Unit 2 diesel generator was completed to demonstrate operability.
The licensee continues their evaluation to determine the adequacy of their preventative maintenance program. Resident inspectors will continue to follow up.
The licensee stated that there has been operating experience on DC power supply ripple affecting the speed switch associated with emergency diesel generators in the past, j /,
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NRR @OECommunity Page 2 of 4 specifically at V.C. Summer, Turkey Point, and Clinton. IOEB is evaluating this ndition for generic applicability and possit.screen into the Issue For Resolution process.
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