ENS 49641
ENS Event | |
|---|---|
09:19 Oct 21, 2013 | |
| Title | 60 Optional Report - Invalid Partial Reactor Protection System Actuation |
| Event Description | Invalid partial Reactor Protection System (RPS) actuation results in; Closure of Containment Isolation Valves (CIVs) in multiple systems, including isolation of the Reactor Water Clean-Up (RWCU) System.
On October 21, 2013, at 0419 EST, Unit 2 received a Reactor Auto SCRAM System 'B' trip signal in the main control room. Initial investigations at the local RPS Motor-Generator (MG) set room discovered breaker 52-3D tripped in cabinet 2C71-P003D. This resulted in a half-scram and the closure of CIVs in multiple systems, including closure of the RWCU system outboard isolation valve, 2G31-F004. These trips are normal responses to the loss of the 'B' RPS. The operating crew entered abnormal operating procedures, including those for loss of RPS and for loss of the RWCU system, and confirmed that all isolations and trips occurred as expected. Additionally, the crew restored the 'B' RPS bus from its alternate source, reset the half scram, returned the CIVs to their normal positions, and placed RWCU in service. Upon investigation, the determination was made that the trip and reset setpoints for under-voltage relay 2C71 -K752D had drifted. Consequently, once the drift reached the trip setpoints during the event, breaker 52-3D tripped, resulting in the loss of the 'B' RPS bus. Because a malfunctioning subcomponent caused the partial RPS trip rather than a valid CIV actuation signal, the resulting isolation is considered an invalid actuation. Further evaluation into the cause of the drift revealed solder joint cracks in the relay circuit board and an inadequate previous refurbishment of the subject relay. The drifting relay was removed and a refurbished relay was installed in location 2C71-K752D. Plans are to replace both units' RPS Power Monitoring relays with a different design. Until that design change is implemented, the frequency of calibration for these relays is being increased from every 182 days to every 91 days. The licensee has notified the NRC Resident Inspector. |
| Where | |
|---|---|
Hatch  Georgia (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1370.8 h57.117 days <br />8.16 weeks <br />1.878 months <br />) | |
| Opened: | J D Sellers 13:07 Dec 17, 2013 |
| NRC Officer: | John Shoemaker |
| Last Updated: | Dec 17, 2013 |
| 49641 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 568972023-11-02T01:11:0002 November 2023 01:11:00
[Table view]10 CFR 50.73(a)(1), Submit an LER 60 Day Notification for an Invalid Specified System Actuation ENS 551882021-02-18T03:20:00018 February 2021 03:20:00 10 CFR 50.73(a)(1), Submit an LER Automatic Actuation of Group 2 Containment Isolation Logic ENS 551872021-02-13T03:23:00013 February 2021 03:23:00 10 CFR 50.73(a)(1), Submit an LER Automatic Actuation of Group I Containment Isolation Logic ENS 538172018-11-12T05:00:00012 November 2018 05:00:00 10 CFR 50.73(a)(1), Submit an LER Invalid Specified System Actuation ENS 528182017-04-27T04:29:00027 April 2017 04:29:00 10 CFR 50.73(a)(1), Submit an LER Invalid Specified System Actuation Due to Failed Relay ENS 528032017-04-17T15:20:00017 April 2017 15:20:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephonic Notification of Invalid Specified System Actuation ENS 526852017-02-17T15:21:00017 February 2017 15:21:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephonic Notification of Invalid Specified System Actuation ENS 496412013-10-21T09:19:00021 October 2013 09:19:00 10 CFR 50.73(a)(1), Submit an LER 60 Optional Report - Invalid Partial Reactor Protection System Actuation ENS 490552013-03-24T14:09:00024 March 2013 14:09:00 10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of Hpci Suction Valves ENS 487212012-12-08T06:16:0008 December 2012 06:16:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephone Notification of Invalid System Actuation ENS 485652012-10-08T22:09:0008 October 2012 22:09:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephonic Notification of Invalid System Actuation ENS 483702012-08-06T01:25:0006 August 2012 01:25:00 10 CFR 50.73(a)(1), Submit an LER Rps Sub-Component Failure Caused Half Scram with Group 2 Pciv Actuation ENS 478592012-02-25T05:38:00025 February 2012 05:38:00 10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of Standby Gas Treatment Secondary Containment Isolation Valves (Scivs) ENS 473372011-08-12T09:03:00012 August 2011 09:03:00 10 CFR 50.73(a)(1), Submit an LER 60 Day Optional Telephone Notification for an Invalid Specified System Actuation ENS 461152010-05-29T12:49:00029 May 2010 12:49:00 10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of Primary Containment Isolation Valves Due to a Faulty Transistor ENS 459812010-04-16T23:15:00016 April 2010 23:15:00 10 CFR 50.73(a)(1), Submit an LER Invalid Specified System Actuation ENS 458352010-02-23T14:50:00023 February 2010 14:50:00 10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of Standby Gas Treatment System ENS 432762007-02-25T08:58:00025 February 2007 08:58:00 10 CFR 50.73(a)(1), Submit an LER Invalid Secondary Containment Isolation ENS 424922006-02-28T06:50:00028 February 2006 06:50:00 10 CFR 50.73(a)(1), Submit an LER Invalid System Actuation Due to Work Instruction Error ENS 421102005-10-07T15:37:0007 October 2005 15:37:00 10 CFR 50.73(a)(1), Submit an LER Invalid System Actuation ENS 415902005-02-19T10:50:00019 February 2005 10:50:00 10 CFR 50.73(a)(1), Submit an LER 60 Day Invalid Actuation of System Report. 2023-11-02T01:11:00 | |