ENS 43677

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v t e ENS Event
02:58 Oct 1, 2007
Title	Unexpected Automatic Start of the 2-1 Emergency Diesel Generator (Edg)
Event Description	A problem with voltage sensing circuit for 4 KV Bus G Startup power supply caused Diesel Generator 2-1 to automatically start. Loss of Startup voltage to a vital bus is an automatic start signal for the associated diesel generator. Startup power has been declared inoperable to 4 KV Bus G. All indications for Startup power to the other 2 vital busses remain normal. All systems functioned correctly in response to the sensed undervoltage condition. Unit 2 is in a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> shutdown action statement per T. S. 3.8.1. An automatic start of a Diesel Generator is reportable per 10CFR50.72(B)(1)(iv)(A). The Diesel Generator has been shutdown per the annunciator response procedure and remains operable. One of the four undervoltage relay starting power fuses for EDG 2-1 was found blown. The NRC Resident Inspector was notified of this event by the licensee. * * UPDATE ON 10/2/07 AT 1947 FROM KEN JOHNSTON TO MARK ABRAMOVITZ * * * This update is changing the reporting criteria from a valid system actuation 8-hour report to a invalid specified system actuation 60-day report. This 60-day notification is being made in accordance with 10 CFR 50.73(a)(i), which states that in case of an invalid actuation reported under 10 CFR 50.73(a)(2)(iv)(A), other than the actuation of the Reactor Protection System when the reactor is critical, the licensee may provide a telephone notification to the NRC within 60 days after discovery of the event instead of submitting a written Licensee Event Report. On September 30, 2007, at 19:58 PDT, EDG 2-1 automatically started, but did not load, due to a failed power supply fuse to an undervoltage sensing relay. EDG 2-1 was shutdown and placed in standby with the undervoltage sensing relay isolated from service. No actual undervoltage condition existed. EDG 2-2 and 2-3 were unaffected by this event. The affected sensing relay circuit was successfully completed. On October 1, 2007, at 18:09 PDT, TS 3.8.1 was exited. The consequences of this event are limited to the unplanned start of EDG 2-1. The EDG started and functioned in accordance with its design. Since no actual vital bus undervoltage condition existed which required the EDG to start, and since the start occurred inadvertently as a result a single component failure, this event has been classified as an invalid actuation. The original 8-hour notification made under 50.72(b)(3)(iv)(A) is therefore retracted and replaced by this 60-day telephone notification. The licensee notified the NRC Resident Inspector. Notified the R4DO (Nease).

ENS 43677 +/-
Where
Diablo Canyon California (NRC Region 4)
Reporting

10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation
Time - Person (Reporting Time:+-2.02 h-0.0842 days <br />-0.012 weeks <br />-0.00277 months <br />)
Opened:	Jan Nimick 00:57 Oct 1, 2007
NRC Officer:	John Mackinnon
Last Updated:	Oct 2, 2007
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v • d • e

v t e Emergency Notification System
Diablo Canyon with 10 CFR 50.73(a)(1), Submit an LER
WEEKMONTHYEAR2023-08-08T18:07:00 [Table view]
[ENS list for Diablo Canyon]

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