View source for PNO-III-23-002B, Prairie Island Update to PNO-III-23-002 Declaration of an Unusual Event Following a Turbine Generator and Reactor Trip Due to Fault on Unit 2 Generator Main Transformer

{{Adams
| number = ML23159A226
| issue date = 06/08/2023
| title = PNO-III-23-002B Prairie Island Update to PNO-III-23-002 Declaration of an Unusual Event Following a Turbine Generator and Reactor Trip Due to Fault on Unit 2 Generator Main Transformer
| author name = Peterson H
| author affiliation = NRC/RGN-III/DNMS
| addressee name = 
| addressee affiliation = 
| docket = 05000306
| license number = 
| contact person = 
| document report number = PNO-III-23-002B
| document type = NRC Preliminary Notification of Event/Occurrence
| page count = 2
}}
{{#Wiki_filter:PRELIMINARY NOTIFICATION - REGION III June 8, 2023 UPDATE TO PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE -
PNO-III-23-002B This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. Some of the information may not yet be fully verified or evaluated by the Region III staff.
Facility                                            Licensee Emergency Classification Xcel Energy                                           X Notification of Unusual Event Prairie Island Nuclear Generating Plant                  Alert Welch, MN                                                Site Area Emergency Docket: 05000306                                         General Emergency
__ Not Applicable

==SUBJECT:==
UPDATE TO PNO-III-23-002 DECLARATION OF AN UNUSUAL EVENT FOLLOWING A TURBINE GENERATOR AND REACTOR TRIP DUE TO FAULT ON UNIT 2 GENERATOR MAIN TRANSFORMER This is an update to the May 27 reactor trip and subsequent Notification of Unusual Event (NOUE) at the Prairie Island Nuclear Generating Plan per Preliminary Notification PNO-III 002 issued on June 1, 2023.
The NOUE was due to indications of a potential fire in the containment building subsequent to the Unit 2 turbine and reactor automatic trip due to a fault on the Unit 2 generator main transformer. The NOUE was terminated shortly after operators were able to confirm that no fire existed. The licensee determined that the fire alarms were caused by the electrical transient which occurred due to the fault on the Unit 2 main transformer.
Following the May 27 trip, the licensee maintained the plant in a safe and stable condition and initiated repairs to the main generator transformer.
The NRC Resident Inspectors continued to monitor the licensees repair efforts following the identification of the cause of the transformer failure. All repairs were completed, and the licensee commenced restart of the Unit 2 reactor.
On June 2, the licensee restarted the reactor and reached approximately 49 percent power.
During the restart, the licensee identified a main feed pump malfunction and initiated troubleshooting activities. On June 5, the licensee determined that a reactor shutdown was necessary to make necessary repairs to the main feed water pump. The licensee shutdown the Unit 2 reactor on June 7 at 3:33 AM CDT. The resident inspectors observed and monitored reactor shutdown and continue to follow licensee activities to implement repairs.
The State of Minnesota was initially notified of the original event by the licensee on May 27.
Region III Government Liaison Officer established communications with the States of Minnesota and Wisconsin to inform them of the latest situation and answer questions.
OFFICIAL RECORD COPY

NRC Region III, located in Lisle, IL, received notification of initial event occurrence by telephone call at 7:28 PM CDT via official event notification of the NOUE on Saturday May 27, 2023, with updates being provided daily. The subsequent plant restart and post maintenance issues were received by the resident inspectors on June 3. Repairs to the main feed pump and restart the unit are being closely monitored by the resident inspectors. The information presented herein has been discussed with the licensee and is current as of 10:50 AM CDT on June 7, 2023.
ADAMS Accession Number: ML23159A226 Contacts:      Hironori Peterson (630) 829-9707 Hironori.Peterson@nrc.gov OFFICIAL RECORD COPY}}

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