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The following information was provided by the licensee via email: On 10/19/2023, at approximately 1110 (CST), with Unit 1 in mode 1 at 100 percent power, the reactor automatically tripped. All control rods fully inserted into the core following the trip. All safety functions operated as designed. The cause of the trip is being investigated. Operations responded and stabilized the plant. Auxiliary feedwater actuated as expected. Decay heat is being removed by the steam generator through the steam generator power operated relief valve. The trip was complex as non-safety related power was lost to both Unit 1 and Unit 2. Unit 1 is currently in mode 3 and on natural recirculation as both reactor coolant pumps are without power. Unit 2 is currently in a refueling outage with all fuel in the spent fuel pool (SFP). SFP cooling was lost for approximately 70 minutes. No impacts to the SFP temperature were observed. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). Due to the actuation of the auxiliary feedwater system following the reactor trip, this event is being reported as a specified system actuation in accordance with the reporting criteria of 10 CFR 50.72(b)(3)(iv)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.

• * * UPDATE ON 10/19/2023 AT 1646 EDT FROM MARTIN CABIRO TO ERNEST WEST * * *

The second paragraph of the original report is amended as follows to correct information regarding the spent fuel pool for Unit 2: Unit 2 is currently in a refueling outage with all fuel in the spent fuel pool (SFP). SFP cooling was maintained at all times with one train of SFP cooling. The second train lost power and was restarted approximately 70 minutes (after power was lost). No impacts to the SFP temperature were observed. Notified R3DO (Orth) and IR MOC (Crouch) and NRR EO (Felts) via email

The following information was provided by the licensee via email: Notification of Unusual Event, HU4.1 declared based on multiple fire alarms in the containment building not verified within 15 minutes. Turbine trip causing reactor trip due to fault on 2GT transformer. At 1845 CDT, verification of no fire in the containment building. Notified DHS Senior Watch Officer, FEMA Operations Center, CISA Central watch officer, DOE Operations Center (email), HHS Operations Center (email), EPA Emergency Operations Center (email), USDA Operations Center (email), FDA EOC (email), FEMA NWC (email) and DHS Nuclear SSA (email), FEMA NRCC (email) and CWMD watch desk (email).

• * * UPDATE AT 0148 EDT ON 5/28/23 FROM CHRIS BAARTMAN TO BILL GOTT * * *

The following information was provided by the licensee via email: This update is being made to report the actuation of the auxiliary feedwater system following the reactor trip at 1819 CDT. This event is being reported as a specified system actuation in accordance with the reporting criteria of 10 CFR 50.72(b)(3)(iv)(A). This update is also being made for the termination of the notification of unusual event at 2304 CDT on 5/27/2023. The basis for the termination was that there was no indication of a fire. Upon lockout of 2GT transformer, main to reserve power transfer did not occur on 3 of 4 non-safeguards buses. Subsequently, operator action successfully restored power to all non-safeguards buses at 1925 CDT. There was no impact to the health and safety of the public or plant personnel. The NRC resident inspector has been notified of the update. Notified R3DO (Benjam¡n), NRR EO (Walker), IRMOC (Grant), DHS Senior Watch Officer, FEMA Operations Center, CISA Central watch officer, DOE Operations Center (email), HHS Operations Center (email), EPA Emergency Operations Center (email), USDA Operations Center (email), FDA EOC (email), FEMA NWC (email) and DHS Nuclear SSA (email), FEMA NRCC (email) and CWMD watch desk (email).

The following information was provided by the licensee via email: On 12/8/2022, Prairie Island Nuclear Generating Plant initiated a notification to the State of Minnesota due to a HVAC coolant leak reaching waters of the state. The estimated quantity is 5 gallons of NALCO LCS-60. The leak was due to a failed heat exchanger coil and has been isolated. This notification is being made solely as a four-hour, non-emergency notification for a Notification of Other Government Agency. This event is reportable in accordance with 10 CFR 50.72(b)(2)(xi). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.

• * * RETRACTION ON 12/21/2022 AT 1115 EST FROM RAYMOND YORK TO JEFF WHITED * * *

The following information was provided by the licensee via email: At 0019 EST on 12/9/2022, the Prairie Island Nuclear Generating Plant (PINGP) made Event Notification 56266 notifying the NRC of an environmental report to the State of Minnesota due to an estimated 5 gallons of NALCO LCS-60 that leaked from a failed heat exchanger coil and reached the waters of the state. This event notification was made in accordance with 10 CFR 50.72(b)(2)(xi). During further review of NRC reporting guidance, PINGP has concluded that the reported quantity of NALCO LCS-60 that leaked during this event was below the reporting threshold outlined in NUREG 1022, Revision 3. The NRC Resident Inspector has been notified. Notified R3DO (Kozak)

At 1930 CDT on 10/17/2021, it was discovered both of the Unit 2 Emergency Diesel Generators were simultaneously INOPERABLE with a requirement to have one OPERABLE train; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10CFR 50.72(b)(3)(v). Offsite power was OPERABLE during this event. There was no impact on the health and safety of the public or plant personnel. The NRC Senior Resident Inspector has been notified. The cause was corrected and both Emergency Diesel Generators are currently operable.

• * * RETRACTION ON 12/13/2021 AT 1607 EST FROM CARLOS PARADA TO LLOYD DESOTELL * * *
• The following information was provided by the licensee via email:

This is a retraction of Event Notification EN55529 in accordance with 10 CFR 50.72(b)(3)(v)(D) made by the Prairie Island Nuclear Generating Plant on October 18, 2021. The original notification stemmed from a loss of power to the non-safety related Unit 2 Emergency Diesel Generator (EDG) starting air compressors. The resulting pressure decay in the EDG starting air receivers led to a decision to declare both EDGs inoperable. A subsequent engineering evaluation has provided reasonable assurance that the Unit 2 EDGs were operable and capable of performing their safety function during the time power was lost. The NRC Resident Inspector has been notified. The HOO notified R3DO (Skokowski).

At 0737 CDT on 10/9/17, Point Beach declared an Unusual Event with Emergency Action Level HU 3.1 due to report of toxic gas from a spill in a service building within the protected area. The spill is contained and cleanup operations are in progress. The spill was not in a contaminated area or vital area. The janitorial worker injured while mixing cleaning chemicals in a closet was taken to the hospital. The licensee notified the NRC Resident Inspector. Notified DHS SWO, FEMA Operations Center, DHS NICC, FEMA NWC (email), DHS Nuclear SSA (email), and FEMA NRCC SASC (email).

• * * UPDATE ON 10/9/17 AT 1111 EDT FROM DENNY SMITH TO BETHANY CECERE * * *

Point Beach has terminated the Unusual Event at 0944 (CDT) on 10/9/2017. The Unusual Event condition is no longer warranted. The NRC Resident Inspector has been notified. Notified R3DO (Hills), NRR EO (King), IRD (Stapleton), DHS SWO, FEMA Operations Center, DHS NICC, FEMA NWC (email), DHS Nuclear SSA (email), and FEMA NRCC SASC (email).

On February 3, 2017, Prairie Island staff performed maintenance on the transom above Battery Room Door 225. This activity resulted in the transom being unlatched for approximately five minutes. On February 6, 2017, a question from the NRC Resident Inspector resulted in an evaluation of this condition for past operability. On March 20, 2017, the past operability evaluation of Door 225 concluded that, in the event of a postulated HELB (High Energy Line Break), the transom being unlatched during the five minute maintenance period resulted in the inoperability of multiple systems in the Unit 1 and Unit 2 battery, auxiliary feedwater, and Unit 1 safeguards bus rooms that would be required to mitigate the postulated HELB. The loss of safety functions required to mitigate the postulated HELB make the condition reportable under 50.72(b)(3)(ii) for an unanalyzed condition that significantly degrades plant safety. Unlatching the transom above the Battery Room Door creates an opening not accounted for in design bases documents. This occurred due to an improperly prepared work permit. Corrective actions are in place to preclude recurrence. The licensee informed the NRC Resident Inspector.

• * * RETRACTION FROM MARK LOOSBROCK TO JEFF ROTTON AT 1559 EDT ON 04/10/2017 * * *

Further analysis determined that an unlatched transom would result in a relative humidity of 100 percent in 11 Battery Room for about 10 minutes following a postulated HELB. Since the equipment in the Battery Rooms is not qualified for a harsh environment, the components in 11 Battery Room would have been inoperable. Temperature and relative humidity in the other Battery Rooms, Auxiliary Feedwater Rooms, and the Unit 1 Safeguards Bus Rooms would have remained within the allowable limits. Therefore, for the five minutes the strike was removed from the transom, only equipment in 11 Battery Room and supported A Train components would have been inoperable. This event was not an Unanalyzed Condition that significantly degraded plant safety, under 10 CFR 50.72(b)(3)(ii), as no safety function would have been lost. The licensee notified the NRC Resident Inspector. Notified R3DO (Skokowski).

At 1620 (CDT), an unusual event was declared due to a smoke detector alarm in Unit 1 containment. (There were) no indications of any other detector alarms, no abnormal equipment indications, and containment parameters are normal (temperature, humidity). At 1631 (CDT), visual inspection (of the) 66 ft. hatch indicated no smoke or abnormal smell. At 1640 (CDT), local inspection of Unit 1 containment verified no fire or hot spots. The licensee has notified the NRC Resident Inspector. Notified DHS SWO, FEMA Ops Center, DHS NICC. Notified FEMA National Watch and Nuclear SSA via E-mail.

• * * UPDATE FROM RYAN RODE TO DONG PARK AT 2208 EDT ON 3/20/2017 * * *

Event transmitted under ENS # 52627 is terminated at 2022 (CDT on) 3/20/17." The NRC Resident Inspector has been notified. Notified R3DO (Orlikowski), NRR EO (Miller), and IRD (Stapleton). Notified DHS SWO, FEMA Ops Center, DHS NICC. Notified FEMA National Watch and Nuclear SSA via E-mail.

Prairie Island Unit 1 declared an Unusual Event at 2359 CDT on 8/13/2016 based on Reactor Coolant System (RCS) identified leakage being greater than 25 gpm. The RCS leakage was 40 gpm for three (3) minutes. The RCS leakage was stopped when letdown flow was isolated. Minimum charging flow has been established and Excess Letdown was placed in service. Prairie Island Unit 1 is currently stable and continues to operate at 100 percent power. There was no impact on Prairie Island Unit 2. CV-31339 (Letdown Line Containment Isolation Valve) failed closed. VC-26-1 (Regenerative Heat Exchanger Letdown Line Outlet Relief to Pressurizer Relief Tank (PRT)) lifted with 40 gallons per minute to the PRT for three (3) Minutes. Operators entered procedure 1C12.1 AOP3, Loss of Letdown Flow to VCT. Letdown was isolated per 1C12.1 AOP3, relief valve VC-26-1 reseated and leakage to the PRT stopped. Charging flow was reduced to one (1) charging pump at minimum speed (16 GPM). Excess letdown was placed in service to maintain pressurizer level between 32 - 34 percent. The cause for CV-31339 closing has not yet been determined. The NRC Resident Inspector has been notified. Notified DHS SWO, FEMA Ops Center, DHS NICC. Notified FEMA National Watch and Nuclear SSA via E-mail.

• * * UPDATE FROM PAUL FINHOLM TO DONALD NORWOOD AT 0525 EDT ON 8/14/2016 * * *

At 0329 CDT the Notice of Unusual Event was terminated based on confirmation that conditions meet all termination criteria. RCS conditions are stable. RCS leakage is less than Technical Specification limits. The current value (of RCS identified leakage) is 0.038 gpm. No classification criteria is currently met. The NRC Resident Inspector has been notified. Notified R3DO (Kozak), NRR EO (Miller), and IRD (Stapleton). Notified DHS SWO, FEMA Ops Center, DHS NICC. Notified FEMA National Watch and Nuclear SSA via E-mail.