ENS 48341
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ENS Event | |
|---|---|
15:44 Sep 25, 2012 | |
| Title | Automatic Reactor Scram During Maintenance on 4160V Bus 12 Ammeter |
| Event Description | During maintenance on 4160V Bus 12 ammeter, a Bus 12 lockout occurred. The station power was from 1R Reserve transformer for work on the 2R Auxiliary transformer. Net effect was Bus 12 locked out, removing power from 12 Reactor Feed Pump and 12 Reactor Recirculation pump. Reactor level lowered to +23 inches then began to rise. With both Main Feed Reg Valves in AUTO, the level transient reached +48 inches, the Reactor Water Level Hi Hi setpoint. The Main Turbine and 11 Reactor Feed Pump tripped as designed, and a Reactor SCRAM occurred. Reactor water level began to drop, and C.4.A Abnormal Procedure for SCRAM was used to restart 11 Reactor Feed Pump and recover water level. Minimum water level reached was -26 inches. Reactor Low Level SCRAM signal and Group 2 Primary Containment isolation occurred at +9 inches as designed, No Safety Relief valves lifted during this transient. High Pressure Coolant Injection (HPCI) and Reactor Core Isolation Cooling (RCIC) did not receive an initiation signal due to not reaching their setpoints. There were no Emergency Core Cooling Systems initiation setpoints reached. Prior to the event, both divisions of Standby Liquid Control were inoperable as part of planned maintenance.
All control rods fully inserted. Decay heat is being removed through the turbine bypass to the main condenser. The plant is in a normal shutdown electrical lineup and stable in Mode 3. The licensee has notified the NRC Resident Inspector and will notify the State and local governments. |
| Where | |
|---|---|
Monticello  Minnesota (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(iv)(B), RPS Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+-0.55 h-0.0229 days <br />-0.00327 weeks <br />-7.5339e-4 months <br />) | |
| Opened: | Ben Cook 15:11 Sep 25, 2012 |
| NRC Officer: | Dong Park |
| Last Updated: | Sep 25, 2012 |
| 48341 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (100 %) |
| After | Hot Shutdown (0 %) |
Monticello with 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
WEEKMONTHYEARENS 569952024-02-28T14:39:00028 February 2024 14:39:00
[Table view]10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Scram ENS 567592023-09-27T15:41:00027 September 2023 15:41:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Actuation of Reactor Protection and Containment Isolation Systems ENS 526822017-04-15T09:41:00015 April 2017 09:41:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Reactor Protection System and Partial Primary Containment Isolation System Actuations on Low Water Level ENS 515602015-11-23T16:40:00023 November 2015 16:40:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Scram Due to a Reactor Recirculation Pump Lockout ENS 491132013-06-13T19:30:00013 June 2013 19:30:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(iv)(A), System Actuation, 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Emergency Diesel Generators Start ENS 490662013-05-24T08:34:00024 May 2013 08:34:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Start of Emergency Diesel Generator Due to Bus Undervoltage ENS 485032012-11-12T21:51:00012 November 2012 21:51:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Building Isolation with Standby Gas Treatment System Actuation During Radioactive Material Move ENS 483412012-09-25T15:44:00025 September 2012 15:44:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Scram During Maintenance on 4160V Bus 12 Ammeter ENS 474602011-11-20T05:12:00020 November 2011 05:12:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Scram While Performing Turbine Bypass Valve Testing ENS 473642011-10-21T17:50:00021 October 2011 17:50:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Scram Due to Lockout of Auxiliary Power Transformer ENS 464962010-12-20T09:57:00020 December 2010 09:57:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Fuel Pool/Reactor Building Exhaust Plenum Primary Power Supply Failed ENS 445082008-09-21T02:35:00021 September 2008 02:35:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unplanned Loss of Shutdown Cooling Due to Containment Isolation ENS 444982008-09-17T15:17:00017 September 2008 15:17:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unusual Event Due to Loss of Shutdown Cooling ENS 444842008-09-12T03:47:00012 September 2008 03:47:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Scram and Isolation Due to Transformer Lockout ENS 432462007-03-18T04:46:00018 March 2007 04:46:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Rps Trip Signal and Containment Isolations Received During Maintenance ENS 430882007-01-10T21:28:00010 January 2007 21:28:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Scram with Stuck Open Main Turbine Control Valves ENS 414412005-02-25T03:11:00025 February 2005 03:11:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Esf Actuation Following Trip of Reactor Protection Motor-Generator Set ENS 414362005-02-23T18:00:00023 February 2005 18:00:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Potential Vulnerability with Alternate Shutdown System (Asds) Isolation Design. 2024-02-28T14:39:00 | |
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