ENS 55926
ENS Event | |
|---|---|
03:45 Apr 12, 2022 | |
| Title | Invalid System Actuation |
| Event Description | The following information was provided by the licensee via email:
The following event description is based on information currently available. If, through subsequent reviews of this event, additional information is identified that is pertinent to this event or alters the information being provided at this time, a follow-up notification will be made via the ENS or under the reporting requirements of 10 CFR 50.73. This telephone notification is being made pursuant to the reporting requirements of 10 CFR 50.73(a)(1) and 10 CFR 50.73(a)(2)(iv)(A) to describe invalid actuations of the Palo Verde Nuclear Generating Station (PVNGS) Unit 1 B Train Auxiliary Feedwater (AF) system and Essential Spray Pond (ESP) system that occurred while in a refueling outage. On April 11, 2022, at approximately 2045 Mountain Standard Time, an automatic start of the Unit 1 B Train AF and ESP systems occurred during restoration from a surveillance test. The station was conducting a surveillance test during a Unit 1 refueling outage to verify the proper responses of the Engineered Safety Features Actuation Systems to simulated design basis events. The test portion was completed satisfactorily; however, during the restoration portion, the load sequencer inadvertently cycled between Mode 0 and Mode 1 three times in immediate succession. At the time of the system actuations, one of the actuation signals associated with this portion of the test had been reset per procedure. Another actuation signal was still in while restoration steps were ongoing, but the sequencer was not expected to cycle between Modes. The system actuations did not occur as a result of actual plant conditions or parameters and are therefore invalid. The Unit 1 B Train AF and ESP system actuations were complete and the systems started and functioned successfully. For the systems that did not actuate, the reasons are clearly understood as those systems were in an overridden condition due to test configuration. The spurious actuation was not able to be replicated and a direct cause was not identified. There were no adverse impacts to public health and safety nor to plant employees. The NRC Resident Inspectors have been informed. |
| Where | |
|---|---|
Palo Verde  Arizona (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1264.78 h52.699 days <br />7.528 weeks <br />1.732 months <br />) | |
| Opened: | Yolanda Good 20:32 Jun 3, 2022 |
| NRC Officer: | Ossy Font |
| Last Updated: | Jun 3, 2022 |
| 55926 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |
WEEKMONTHYEARENS 559262022-04-12T03:45:00012 April 2022 03:45:00
[Table view]10 CFR 50.73(a)(1), Submit an LER Invalid System Actuation ENS 550322020-12-11T07:00:00011 December 2020 07:00:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Option Telephonic Notification of an Invalid Specified System Actuation ENS 547012020-03-14T19:44:00014 March 2020 19:44:00 10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of Spray Pond Pump System - 60 Day Reports ENS 524132016-10-17T22:19:00017 October 2016 22:19:00 10 CFR 50.73(a)(1), Submit an LER Invalid Engineered Safety Features Actuation System (Esfas) Signal ENS 522282016-07-12T12:50:00012 July 2016 12:50:00 10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of Both Trains Essential Spray Pond System ENS 498072013-12-12T03:11:00012 December 2013 03:11:00 10 CFR 50.73(a)(1), Submit an LER 60 Day Report for an Invalid Main Steam Line Actuation ENS 486152012-10-26T04:08:00026 October 2012 04:08:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephonic Notification for an Invalid Actuation of the Essential Spray Pond System ENS 468982011-04-03T21:44:0003 April 2011 21:44:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Notification of Invalid Start of the 'A' Emergency Diesel Generator ENS 427342006-06-06T01:44:0006 June 2006 01:44:00 10 CFR 50.73(a)(1), Submit an LER Invalid Emergency Diesel Generator Start ENS 418042005-04-29T07:43:00029 April 2005 07:43:00 10 CFR 50.73(a)(1), Submit an LER Invalid System Actuation 2022-04-12T03:45:00 | |