Event Notification Report for April 02, 2026

EN Revision Imported Date: 4/1/2026

EN Revision Text: UNUSUAL EVENT DECLARED FOR RCS LEAKAGE FOR GREATER THAN 15 MINUTES

The following is a summary of information provided by the licensee via phone:

At 0819 MST on 3/19/2026, with Palo Verde Unit 2 at 95 percent power, the site declared an Unusual Event under emergency action level 'SU5.1' due to identified reactor coolant system leakage for greater than 15 minutes. The leak was isolated by securing letdown. A manual reactor trip was inserted, and Unit 2 is currently shutdown in mode 3. Palo Verde Units 1 and 3 were unaffected.

State and local authorities were notified.

The NRC Senior Resident Inspector has been notified.

Notified DHS SWO, FEMA Ops Center, FEMA NWC, CISA Central, CWMD Watch Desk, DHS Nuclear SSA (email), and DHS NRCC THD Desk (email).


* * * UPDATE ON 03/19/2026 AT 1535 EDT FROM PEDRO REGUERA TO BETHANY CECERE * * *

The following update was provided by the licensee via phone:

This update is a 10 CFR 50.72(b)(2)(iv)(B) required report of a valid RPS actuation while critical due to operators tripping Palo Verde Unit 2 at 0841 MST.

Notified R4DO (Dixon), NRR EO (Feliz Adorno), IR MOC (Whited), R4RA (Monninger), NRR (Groom), R4 PAO (Smith), and NSIR (Williams).


* * * UPDATE ON 03/19/2026 AT 1717 EDT FROM COLLIN MILLER TO JOSUE RAMIREZ * * *

The following information was provided by the licensee via phone:

Palo Verde Unit 2 terminated the notice of unusual event 'SU5.1' at 1410 MST. The leak was isolated, the plant is stable, and there was no release.

State and local authorities were notified.

The NRC Senior Resident Inspector has been notified.

Internal notifications: R4DO (Dixon), NRR EO (Feliz Adorno), IR MOC (Whited), R4RA (Monninger), NRR (Groom), R4 PAO (Smith), and NSIR (Williams).

External notifications: DHS SWO, FEMA Ops Center, FEMA NWC, CISA Central, CWMD Watch Desk, DHS Nuclear SSA (email), and DHS NRCC THD Desk (email).

* * * UPDATE ON 03/31/2026 AT 1920 EDT FROM SHAUN BERNAT TO IAN HOWARD * * *

"This notification constitutes a retraction of the 1-hour immediate notification (EN 58211) of the unusual event made to the NRC by Palo Verde Nuclear Generating Station [PVNGS] on March 19, 2026.

"Palo Verde is [partially] retracting this event notification in accordance with the guidance provided in NUREG 1022, Revision 3, `Event Reporting Guidelines 10 CFR 50.72 and 50.73,' specifically Section 2.8, `Retraction and Cancellation of Event Reporting,' and Section 4.2.3, `ENS Notification Retraction.'

"The leakage reported on March 19, 2026, was subsequently determined to have originated from a failed O-ring on a seal injection filter housing. The leakage was isolated by closing installed isolation valves on the seal injection filter housing. Following evaluation, this condition was determined not to meet the criteria for reactor coolant system (RCS) identified leakage as defined in SU5.1 of the PVNGS emergency plan.

"Clarification: Leakage was not isolated by securing letdown, as originally reported in the ENS notification submitted on March 19, 2026. This update applies solely to the retraction of the unusual event declaration."

The NRC Resident Inspector has been notified.

Notified R4DO (Deese).

AGREEMENT STATE REPORT - LOST SOURCE

The following information was provided by the Iowa Department of Health and Human Services (the Department) via phone and email:

"On March 25, 2026, the licensee informed the Department of a possible reportable event. It is reportable as per 10 CFR 20.2201(a)(1)(i) (greater than 1,000 times the quantity specified in Part 20 Appendix C; Co-60 = 1 microcurie).

"The service provider (Berthold) came on site to retrieve the third Co-60 source from inside the dip tube that had come detached from the rod and cable. Upon surveying the tube, no source was detected. Upon sending a camera into the tube, no source was detected.

"At the time of the notification to the Department, the investigation is still ongoing.

"The Department will be discussing next steps on Thursday, March 26.

"Source: Co-60
"Serial number: 80115
"Calculated activity based off activity at installation: 27.6 mCi (27600 microcuries)"

Iowa event report ID number: IA260002

THIS MATERIAL EVENT CONTAINS A 'Less than Cat 3' LEVEL OF RADIOACTIVE MATERIAL

Sources that are "Less than IAEA Category 3 sources," are either sources that are very unlikely to cause permanent injury to individuals or contain a very small amount of radioactive material that would not cause any permanent injury. Some of these sources, such as moisture density gauges or thickness gauges that are Category 4, the amount of unshielded radioactive material, if not safely managed or securely protected, could possibly - although it is unlikely - temporarily injure someone who handled it or were otherwise in contact with it, or who were close to it for a period of many weeks. For additional information go to http://www-pub.iaea.org/MTCD/publications/PDF/Pub1227_web.pdf

LOSS OF SEISMIC MONITORING

The following information was provided by the licensee via phone and email:

"At 0750 EDT on March 31, 2026, the Vogtle 1 and 2 seismic monitoring panel was discovered [to be] nonfunctional while performing operator rounds in the control room. Compensatory measures for seismic event classification have been implemented in accordance with Vogtle procedures.

"This is an eight-hour, non-emergency notification for a loss of emergency assessment capability. This event is reportable in accordance with 10 CFR 50.72(b)(3)(xiii) because the seismic monitoring panel is the method for evaluating that an operational basis earthquake (OBE) threshold has been exceeded following a seismic event. This is in accordance with initiating condition `seismic event greater than OBE levels' and emergency action level HU2.

"There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified."

UNANALYZED CONDITION

The following information was provided by the licensee via phone and email:

"At 0924 EDT on April 1, 2026, it was determined that Unit 3 was in an unanalyzed condition because two emergency diesel generators (EDGs) were inoperable. One EDG was inoperable due to scheduled maintenance, and the second EDG was inoperable due to blocking for an emergent plant issue. This condition is not bounded by existing design and licensing documents; however, it poses no impact to the health and safety of the public or plant personnel. The second EDG was returned to service, and the condition was exited.

"This event is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(B) and 10 CFR 50.72(b)(3)(v)(D).

"The NRC Resident Inspector has been notified."

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:

Unit 2 was unaffected by this condition. No other limiting conditions exist. The second EDG was blocked due to a failed transformer, but the transformer has been repaired.