ENS 42740
ENS Event | |
|---|---|
22:30 Jul 30, 2006 | |
| Title | Secondary Containment Isolation Due to 'B' Spent Fuel Rad Monitor Failure |
| Event Description | At 1730 on 7/30/06 the 'B' Spent Fuel Pool Radiation Monitor spiked high, which resulted in the closure of the DW CAM (Continuous Air Monitor) and the Oxygen analyzer primary containment isolation valves. The spikes (2) of approximately 50 Mr/hour occurred during this event. Only 1 automatic isolation occurred. The Spent Fuel Pool Radiation Monitor High Rad signal also resulted in a Reactor Bldg Isolation (Secondary Containment), start of 'A' Standby Gas Treatment, and transfer of the Control Room Ventilation to the High Rad Mode. The 'A' Spent Fuel Pool Monitor remained constant at its background radiation level. No activities were in progress on the Refuel Floor at the time of the trips. Rad Protection Tech surveyed the area with no abnormal readings noted. The 'B' Spent Fuel Pool Radiation Monitor was declared inoperable. All automatic isolation valves have been reset, Rx Bldg Ventilation, Control Room Ventilation have been reset and SBGT (Standby Gas Treatment) has been secured. Normal trip setpoint is 50 Mr/ hour.
The licensee has taken the actions of LCO 3.2.E The licensee notified the NRC Resident Inspector.
This report is being reclassified 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 micro switch and therefore was not a valid signal. Because the actuation signal was not valid, Monticello is reclassifying the initial event report 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 (EN#42740) [see above] 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 'B' Spent Fuel Pool Radiation Monitor was returned to service. The licensee has notified the NRC Resident Inspector. Notified R3DO T. Kozak. |
| Where | |
|---|---|
Monticello  Minnesota (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1.68 h0.07 days <br />0.01 weeks <br />0.0023 months <br />) | |
| Opened: | Chet Demarais 00:11 Jul 31, 2006 |
| NRC Officer: | Jason Kozal |
| Last Updated: | Aug 8, 2006 |
| 42740 - 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 | |