Event Notification Report for April 28, 2023
U.S. Nuclear Regulatory Commission
Operations Center
EVENT REPORTS FOR
04/27/2023 - 04/28/2023
EVENT NUMBERS
56584
56584
Power Reactor
Event Number: 56584
Facility: Monticello
Region: 3 State: MN
Unit: [1] [] []
RX Type: [1] GE-3
NRC Notified By: Quinten Kovanen
HQ OPS Officer: Brian P. Smith
Region: 3 State: MN
Unit: [1] [] []
RX Type: [1] GE-3
NRC Notified By: Quinten Kovanen
HQ OPS Officer: Brian P. Smith
Notification Date: 06/22/2023
Notification Time: 09:44 [ET]
Event Date: 04/28/2023
Event Time: 04:02 [CDT]
Last Update Date: 06/22/2023
Notification Time: 09:44 [ET]
Event Date: 04/28/2023
Event Time: 04:02 [CDT]
Last Update Date: 06/22/2023
Emergency Class: Non Emergency
10 CFR Section:
50.73(a)(1) - Invalid Specif System Actuation
10 CFR Section:
50.73(a)(1) - Invalid Specif System Actuation
Person (Organization):
Orlikowski, Robert (R3DO)
Orlikowski, Robert (R3DO)
| Unit | SCRAM Code | RX Crit | Initial PWR | Initial RX Mode | Current PWR | Current RX Mode |
|---|---|---|---|---|---|---|
| 1 | N | N | 0 | Refueling | 0 | Refueling |
60 DAY NOTIFICATION FOR AN INVALID ACTUATION OF PRIMARY CONTAINMENT ISOLATION LOGIC
The following information was provided by the licensee email:
"This telephone notification is provided in accordance with 10 CFR 50.73(a)(1) and 10 CFR 50.73(a)(2)(iv)(A) to report an invalid actuation of Division 2 Primary Containment Isolation logic at the Monticello Nuclear Generating Plant (MNGP) that occurred while in a refueling outage.
"At approximately 0402 Central Daylight Time (CDT) on April 28, 2023 and at approximately 1611 and 2143 CDT on May 4, 2023, momentary losses of 'Y80 Division 2 Uninterruptible 120VAC Class 1E Distribution Panel', which provides power to Division 2 Primary Containment Isolation logic, resulted in a partial Primary Containment Group 2 Isolation (gas systems), initiation of the Standby Gas Treatment system, and the shift of Control Room ventilation to the high radiation mode. The momentary losses of 'Y80' were due to an intermittent, age-related degradation issue with the 'Uninterruptible Power Supply Y81, Division 2 120VAC Class 1E Inverter', which resulted in a temporary loss of output plus a lack of static switch transfer from the inverter supply to the alternate source as designed.
"The actuations were not initiated in response to actual plant conditions, these were not intentional manual initiations, and there were no parameters satisfying the requirements for initiation. Therefore, these events have been determined to be invalid actuations that were attributed to the same cause.
"All systems responded as designed to the actuation signal. Operations reset the partial Primary Containment Group 2 Isolation signal, shutdown the Standby Gas Treatment system, and restored Control Room ventilation per the procedure. There was no impact on the health and safety of the public or plant personnel.
"The NRC Resident Inspector has been notified."
The following information was provided by the licensee email:
"This telephone notification is provided in accordance with 10 CFR 50.73(a)(1) and 10 CFR 50.73(a)(2)(iv)(A) to report an invalid actuation of Division 2 Primary Containment Isolation logic at the Monticello Nuclear Generating Plant (MNGP) that occurred while in a refueling outage.
"At approximately 0402 Central Daylight Time (CDT) on April 28, 2023 and at approximately 1611 and 2143 CDT on May 4, 2023, momentary losses of 'Y80 Division 2 Uninterruptible 120VAC Class 1E Distribution Panel', which provides power to Division 2 Primary Containment Isolation logic, resulted in a partial Primary Containment Group 2 Isolation (gas systems), initiation of the Standby Gas Treatment system, and the shift of Control Room ventilation to the high radiation mode. The momentary losses of 'Y80' were due to an intermittent, age-related degradation issue with the 'Uninterruptible Power Supply Y81, Division 2 120VAC Class 1E Inverter', which resulted in a temporary loss of output plus a lack of static switch transfer from the inverter supply to the alternate source as designed.
"The actuations were not initiated in response to actual plant conditions, these were not intentional manual initiations, and there were no parameters satisfying the requirements for initiation. Therefore, these events have been determined to be invalid actuations that were attributed to the same cause.
"All systems responded as designed to the actuation signal. Operations reset the partial Primary Containment Group 2 Isolation signal, shutdown the Standby Gas Treatment system, and restored Control Room ventilation per the procedure. There was no impact on the health and safety of the public or plant personnel.
"The NRC Resident Inspector has been notified."