ENS 42594
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ENS Event | |
|---|---|
12:01 May 22, 2006 | |
| Title | Manual Reactor Scram as a Mitigating Action Due to Lowering Service Air Pressure |
| Event Description | CNS was operating at 100% power at 06:51 CDT on May 22, 2006 when Plant Service Air pressure began lowering due to an unknown cause. Additional Service Air Compressors could not be started in time to recover Service Air pressure. A rapid power reduction was performed and at 07:01 the reactor was manually scrammed as a mitigating action due to lowering Plant Service Air pressure. All control rods fully inserted and a Group 2 Isolation occurred due to low Reactor Vessel level as expected following the manual scram. Minimum Reactor level was -20 inches Wide Range. The reactor is currently shutdown and stable with level maintained at 35 inches in the green band on the Narrow Range Indicators with the Feedwater System. Reactor pressure following the scram was stabilized at approximately 900 psig using the Main Condenser Bypass Valves and is slowly lowering.
This report is made in accordance with 10CFR50.72 as a 4 Hour Report due to a valid RPS actuation and as an 8 Hour Report due to a valid Group 2 Isolation actuation. All automatic actions functioned as expected. The plant is being maintained in Hot Shutdown while the cause of the Plant Service Air Pressure lowering is being investigated. The NRC Senior Resident inspector has been informed of the event. The scram was characterized as uncomplicated. The licensee is not in any significant tech spec LCO and all systems functioned as required. It was noted that there are 3 service air compressors available and only one of the compressors was running at the time of the event. The licensee does not yet know the cause of the service air pressure loss or why the backup compressors did not autostart. Instrument air pressure was maintained during the event. |
| Where | |
|---|---|
Cooper  Nebraska (NRC Region 4) | |
| 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:+-1.8 h-0.075 days <br />-0.0107 weeks <br />-0.00247 months <br />) | |
| Opened: | Steve Wheeler 10:13 May 22, 2006 |
| NRC Officer: | Bill Huffman |
| Last Updated: | May 22, 2006 |
| 42594 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | Yes, Manual Scram |
| Before | Power Operation (100 %) |
| After | Hot Shutdown (0 %) |
Cooper with 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
WEEKMONTHYEARENS 562782022-12-17T05:51:00017 December 2022 05:51:00
[Table view]10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Scram ENS 562202022-11-13T04:19:00013 November 2022 04:19:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Scram ENS 561742022-10-22T17:58:00022 October 2022 17:58:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation, 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge ECCS Injection While Shutdown ENS 549762020-11-01T10:34:0001 November 2020 10:34:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip Due to an Un-Isolable Leak on the Turbine High Pressure Fluid System ENS 522612016-09-25T06:03:00025 September 2016 06:03:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Actuation of Group 1 Isolation Signal ENS 454892009-11-11T23:43:00011 November 2009 23:43:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Scram After a Turbine Hydraulic Fluid Leak ENS 454822009-11-07T01:30:0007 November 2009 01:30:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Due to an Unisolable Leak on the Turbine High Pressure Fluid System ENS 444022008-08-09T07:04:0009 August 2008 07:04:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Scram Due to Failure of Reheat Stop Valve to Open During Turbine Valve Testing ENS 433752007-05-19T07:12:00019 May 2007 07:12:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Due to Control Rod Hcu Valve Bonnet Leak Into Reactor Building ENS 425942006-05-22T12:01:00022 May 2006 12:01:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Scram as a Mitigating Action Due to Lowering Service Air Pressure ENS 423752006-02-26T08:50:00026 February 2006 08:50:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Scram Due to Msr High Level ENS 420102005-09-23T05:40:00023 September 2005 05:40:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Scram Due to Degrading Main Condenser Vacuum ENS 416012005-04-15T09:36:00015 April 2005 09:36:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 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)(2)(iv)(A), System Actuation - ECCS Discharge Reactor Scram and Specified System Actuations ENS 403622003-11-29T04:02:00029 November 2003 04:02:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation, 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge Automatic Scram Due to Low Reactor Water Level 2022-12-17T05:51:00 | |
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