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| Entered date | Event description | |
|---|---|---|
| ENS 46346 | 19 October 2010 20:09:00 | On October 19, 2010, at about 1515 PDT, SONGS Unit 3 RPS channels 'B' and 'D' were tested for maintenance. During this testing, both channels were powered off, which brought in LPD/DNBR (local power density/departure from nucleate boiling) trips on both channels. There are no applicable Technical Specifications required for these RPS channels in Mode 5. Southern California Edison(SCE) is reporting this occurrence as a valid actuation of RPS in accordance with 10 CFR 50.72(b)(3)(iv)(a). SCE has taken actions to restore both channels 'B' and 'D' of RPS and cleared the RPS trip signal. At the time of this occurrence, Unit 2 was at approximately 100% power and Unit 3 was in a Steam Generator Replacement Outage, Mode 5, shutdown and cooldown with the RCS open, proceeding to Mode 6." The NRC Resident Inspector has been notified. * * * RETRACTION FROM DENNIS MORRIS TO PETE SNYDER AT 0045 EDT ON 10/21/10 * * * On October 19, 2010, SCE reported (Event No. 46346) a valid actuation of the Reactor Protection System (RPS) in accordance with 10 CFR 50.72(b)(3)(iv)(A). Upon further review, SCE determined the actuation was invalid and is retracting the notification. Maintenance and surveillance testing was being conducted by Computer Technicians on the Core Protection Calculator (CPC) Channels 'A' and 'D', respectively, following station procedures. De-energizing the CPC channels was expected to bring in an RPS trip signal. The process to disable the control room RPS alarms had not as yet, been completed by the Instrument and Controls group when the CPCs were de-energized by procedure, actuating the RPS logic and causing the control room alarms. The actuation is considered invalid, as the equipment that would have been actuated by the trip safety function was previously de-energized and removed from service for the refueling outage. The Unit 3 reactor was in Mode 5, with the reactor trip breakers open, and control rods inserted. Unit 2 reactor remains at 100% power. The licensee notified the NRC Resident Inspector. Notified R4DO (V.Campbell). |