ENS 56584
ENS Event | |
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09:02 Apr 28, 2023 | |
Title | 60 Day Notification for an Invalid Actuation of Primary Containment Isolation Logic |
Event Description | 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. |
Where | |
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Monticello Minnesota (NRC Region 3) | |
Reporting | |
10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
Time - Person (Reporting Time:+1320.7 h55.029 days <br />7.861 weeks <br />1.809 months <br />) | |
Opened: | Quinten Kovanen 09:44 Jun 22, 2023 |
NRC Officer: | Brian P. Smith |
Last Updated: | Jun 22, 2023 |
56584 - NRC Website
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WEEKMONTHYEARENS 565842023-04-28T09:02:00028 April 2023 09:02:00
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