ENS 57091
ENS Event | |
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01:56 Mar 25, 2024 | |
Title | Invalid Actuation of Automatic Turbine Driven Auxiliary Feedwater Pump |
Event Description | The following information was provided by the licensee via phone and email:
This report is being made in accordance with 10 CFR 50.73(a)(2)(iv)(A), under the provision of 10 CFR 50.73(a)(1), detailing the event in which an unplanned actuation of the turbine driven auxiliary feedwater pump (TDAFP) at the Callaway plant occurred in response to an invalid actuation signal. The actuation occurred at 2056 [CDT] on 3/21/2024 during restoration from maintenance on the NN12 inverter. The actuation signal was received while closing breaker NK0211 (for connecting the inverter to its associated 125-VDC bus). In response to the TDAFP actuation, operators closed the flow control valves and reduced turbine load by approximately 10 MW electrical. Initial investigation showed that a spurious manual actuation signal had been received and cleared 5 seconds later. The direct cause of the event was due to a voltage transient generated on the NK02 125-VDC bus during closure of the NK0211 breaker. The actuation occurred due to degradation of a 48-VDC power supply (PS1) within engineered safety features actuation system (ESFAS) logic cabinet SA036C. The power supply exhibited elevated ripple during testing as part of troubleshooting efforts, which was indicative of degradation of the regulation circuitry within the supply. This degradation prevented the power supply from sufficiently filtering the transient that occurred on the 125-VDC bus associated with the NN12 inverter. The power supply was replaced. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The licensee originally submitted this event under 10 CFR 50.72(b)(3)(iv)(A) in EN 57043. The licensee has retracted EN 57043. |
Where | |
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Callaway Missouri (NRC Region 4) | |
Reporting | |
10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
Time - Person (Reporting Time:+755.7 h31.488 days <br />4.498 weeks <br />1.035 months <br />) | |
Opened: | Greg Cizin 13:38 Apr 25, 2024 |
NRC Officer: | Ernest West |
Last Updated: | Apr 25, 2024 |
57091 - NRC Website
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Unit 1 | |
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Reactor critical | Critical |
Scram | No |
Before | Power Operation (100 %) |
After | Power Operation (100 %) |
WEEKMONTHYEARENS 570912024-03-25T01:56:00025 March 2024 01:56:00
[Table view]10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of Automatic Turbine Driven Auxiliary Feedwater Pump ENS 559722022-05-02T04:05:0002 May 2022 04:05:00 Other Unspec Reqmnt, 10 CFR 50.73(a)(1), Submit an LER Invalid Specified System Actuation ENS 491412013-04-24T09:04:00024 April 2013 09:04:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephone Notification for an Invalid Specified System Actuation ENS 491032013-04-11T06:28:00011 April 2013 06:28:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephone Notification for an Invalid Specified System Actuation 2024-03-25T01:56:00 | |