ENS 42788
ENS Event | |
|---|---|
23:49 Aug 19, 2006 | |
| Title | Radiation Monitor Electrical Spike Causes Secondary Containment Isolation |
| Event Description | The 'B' fuel pool radiation monitor spiked high causing an actuation of the secondary containment relays. 'A' SBGTS [Standby Gas Treatment System] train started, reactor building, turbine building, and rad waste building ventilation isolated. The Drywell Continuous Air Monitor (DW CAM) and O2 analyzer containment valves isolated. The control room ventilation system transferred to the high radiation mode.
At the time of the occurrence the 'A' Fuel Pool radiation monitor was reading normal (0.5 mr/hr). The 'B' Fuel Pool radiation monitor was reading 80 mr/hr. The 'B Fuel Pool radiation monitor, soon after lowered to 30-40 mr/hr and then back to normal (10 mr/hr). The trip setpoint is 50 mr/hr. The trip was reset. The secondary containment isolation and all ventilation trips were restored to normal. The DW CAM and control room ventilation were restored to normal. A local survey was performed on the refuel floor, readings obtained were < 5 mr/hr at the detector and < 2 mr/hr in surrounding areas. The 'B' fuel pool radiation monitor high level trips were placed in the trip/bypass position. The 'B' fuel pool radiation monitor was placed in downscale trip condition to comply with Technical Specification Table 3.2.4. A team is being established to investigate the cause of the trip. 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 an invalid spurious signal since other radiation monitors in the area did not indicate any change in value. The cause of the spurious signal was determined to be inducted noise through an unshielded cable which resulted in an increased output current to the instrument. 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 (ENS #42788) detailed the system affected, whether the actuation was complete or partial, and whether each affected system started and functioned successfully. The licensee has notified the NRC Resident Inspector.' NRC R3DO (Julio Lara) notified. |
| Where | |
|---|---|
Monticello  Minnesota (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+-0.65 h-0.0271 days <br />-0.00387 weeks <br />-8.9037e-4 months <br />) | |
| Opened: | Bart Blakesley 23:10 Aug 19, 2006 |
| NRC Officer: | Mark Abramovitz |
| Last Updated: | Sep 22, 2006 |
| 42788 - 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 | |