ENS 42652
ENS Event | |
|---|---|
04:19 Jun 19, 2006 | |
| Title | Radiation Monitor Spiked Three Times |
| Event Description | At 2319 on 06/18/2006, the 'A' Plenum Radiation Monitor spiked high which resulted in the closure of the Drywell CAM (Continuous Air Monitor) and the Oxygen Analyzer Primary Containment Isolation Valves. The spike's (3) of approx. 30 Mr/HR occurred during this event. The valves isolated once, the Reactor Building Ventilation trip was reset once and re-isolation occurred several minutes later from another spike on the Rad Monitor. Trip setpoint is 26 Mr/hr. The Plenum high Rad signal also resulted in Reactor Building isolation (twice), start of 'A' Standby Gas Treatment, and transfer of the Control Room Ventilation to the high Rad Mode. The 'B' Plenum Rad Monitor remained constant at 1.3 Mr/hr. The Reactor Building Ventilation and Control Room Ventilation have been reset and Standby Gas Treatment has been secured. The 'A' Plenum Radiation Monitor has been declared inoperable.
Instrument & Control Technicians are currently troubleshooting the problem associated with the 'A' Plenum Radiation Monitor. The NRC Resident Inspector's have been left messages by the licensee.
This report is being reclassified by the licensee from a 50.72(b)(3)(iv)(A) [valid system actuation] to 50.73(a)(2)(iv)(A) [invalid system actuation]. Based on further investigation, Monticello has determined that the actuation signal was due to a failed microswitch and therefore was not a valid signal. Because the actuation signal was not valid, Monticello is retracting the initial event report and instead reporting this event as an unplanned system actuation under 50.73(a)(2)(iv)(A). This report will be made in lieu of reporting the event as an LER. In accordance with 50.73(a)(2)(iv)(A): This report is not considered an LER and the report is being made under 50.73(a)(2)(iv)(A). The original event report (ENS #42652) detailed the systems affected, whether the actuation was complete or partial and whether each affected system started and functioned successfully. The cause of the invalid signal was the failure of the trip check pushbutton [micro]switch due to age related degradation. The switch has been replaced and the 'A' Plenum Radiation Monitor was returned to service. The licensee notified the NRC Resident Inspector. Notified the R3DO (O'Brien). |
| Where | |
|---|---|
Monticello  Minnesota (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+-0.22 h-0.00917 days <br />-0.00131 weeks <br />-3.01356e-4 months <br />) | |
| Opened: | Ryan Richards 04:06 Jun 19, 2006 |
| NRC Officer: | John Mackinnon |
| Last Updated: | Aug 3, 2006 |
| 42652 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 565842023-04-28T09:02:00028 April 2023 09:02:00
[Table view]10 CFR 50.73(a)(1), Submit an LER 60 Day Notification for an Invalid Actuation of Primary Containment Isolation Logic ENS 557082021-11-29T17:28:00029 November 2021 17:28:00 10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of Secondary Containment Relays ENS 524512016-10-24T23:45:00024 October 2016 23:45:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephonic Notification of Invalid Specified System Actuation ENS 448992009-01-20T16:10:00020 January 2009 16:10:00 10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of Secondary Containment ENS 442112008-04-03T11:25:0003 April 2008 11:25:00 10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of a Sbgt During Annunciator Test ENS 427882006-08-19T23:49:00019 August 2006 23:49:00 10 CFR 50.73(a)(1), Submit an LER Radiation Monitor Electrical Spike Causes Secondary Containment Isolation ENS 427402006-07-30T22:30:00030 July 2006 22:30:00 10 CFR 50.73(a)(1), Submit an LER Secondary Containment Isolation Due to 'B' Spent Fuel Rad Monitor Failure ENS 426522006-06-19T04:19:00019 June 2006 04:19:00 10 CFR 50.73(a)(1), Submit an LER Radiation Monitor Spiked Three Times 2023-04-28T09:02:00 | |