ENS 45585

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v t e ENS Event
05:13 Nov 22, 2009
Title	Unexpected Automatic Start of the 2-1 Emergency Diesel Generator (Edg)
Event Description	This notification is being made in accordance with 10 CFR 50.73(a)(i), which states, in part; 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 November 21, 2009, at 2113 PST, EDG 2-1 automatically started, but did not load, due to an attempted replacement of an indicating light that caused a control circuit electrical short and opening the power supply fuse. EDG 2-2 and EDG 2-3 were unaffected by this event. Plant operators entered TS 3.8.1, AC Sources - Operating, due to the loss of the Startup Feeder indication circuit. No actual condition requiring the start of EDG 2-1 existed. The EDG 2-1 4kV Bus Start up Transfer Feeder Undervoltage Relay was placed in bypass (knife switch #10 for relay 27 HGU opened), the EDG was shutdown at 2147 PST and placed in standby operation at 2148 PST. This inadvertent start relay input is not a required safety function, but provides an anticipatory start of the EDG. The actuated relay input is not required for operability, thus the EDG was operable at 2148 PST. Electrical Maintenance replaced the affected sensing relay circuit fuse (52HG14 "UA" fuses), tightened the indicating light socket for SUT 2 2 Potential C A Phase, and reset 27HGU (Startup Feeder UV for 4kV Bus G). On November 22, 2009, at 0729 PST, TS 3.8.1 was exited. The consequences of this event were limited to the unplanned start of EDG 2-1. The EDG started and functioned in accordance with its design. Since no valid signal which required the EDG to start, and since the start occurred inadvertently as the result of a known maintenance action (resulting in a single component failure, a protective fuse opening), this event has been classified as an invalid actuation. The licensee has notified the NRC Resident Inspector.

ENS 45585 +/-
Where
Diablo Canyon California (NRC Region 4)
Reporting

10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation
Time - Person (Reporting Time:+726.02 h30.251 days <br />4.322 weeks <br />0.995 months <br />)
Opened:	Murrell Evans 11:14 Dec 22, 2009
NRC Officer:	Pete Snyder
Last Updated:	Dec 22, 2009
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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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