ENS 45850
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ENS Event | |
|---|---|
23:17 Apr 16, 2010 | |
| Title | Loss of Cooling Accident Signal Due to High Drywell Pressure Signal |
| Event Description | On April 16, 2010 at 1917 hrs., Unit 1 received an ECCS [emergency core cooling system] loss of cooling accident (LOCA) signal on high drywell pressure. Based on plant data, drywell pressure reached a maximum pressure of approximately 1.25 psig, which is below the LOCA and RPS [reactor protection system] signal actuation pressure of 1.85 psig. At this time, the cause of the drywell pressure increase is under investigation. RPS logic did not initiate due to drywell pressure not reaching the actuation setpoint of 1.85 psig. Although the ECCS logic prematurely actuated, the signal is being treated as 'valid' for the ECCS actuation until further investigation is completed. All expected ECCS actions occurred as a result of the signal. The LOCA logic has been reset and all affected systems have been returned to normal or standby configuration.
As a result of the LOCA system actuations, several cooling tower fans tripped and condenser vacuum began to decrease. Reactor power was reduced to approximately 86 percent as a result of decreasing condenser vacuum. Power is being maintained at approximately 86 - 88 percent at this time. There are no other plant issues or concerns at this time. The licensee notified the NRC Resident Inspector. According to the licensee, normal drywell operating pressure is .5 to 1.2 psig. Prior to the event, drywell pressure had been steady at approximately 1.0 psig. Current drywell pressure is .6 psig. According to the licensee, ECCS systems that started (but did not inject) included: Core Spray pumps, Residual Heat Removal pumps, High Pressure Coolant Injection pump, and the Diesel Generators. An event review team is assessing this event to determine the root cause.
On April 16, 2010, Hatch Unit 1 received a LOCA ECCS initiation from a high drywell pressure signal. Based on the information available at that time, a notification was made to the NRC assuming the signal to be valid until further investigation could be completed. After further review, the determination has been made that the initiation signal originated from a faulted ATTS [Analog Transmitter Trip System] card and not from a valid high drywell pressure condition. Based on this information, this condition did not require an NRC notification in accordance with 10CFR50.72 and, as such, is being retracted through this updated response. The licensee notified the NRC Resident Inspector. Notified the R2DO (Hopper) |
| Where | |
|---|---|
Hatch  Georgia (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+2.2 h0.0917 days <br />0.0131 weeks <br />0.00301 months <br />) | |
| Opened: | Al Manning 01:29 Apr 17, 2010 |
| NRC Officer: | Donald Norwood |
| Last Updated: | Apr 17, 2010 |
| 45850 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (86 %) |
WEEKMONTHYEARENS 570212024-03-11T17:37:00011 March 2024 17:37:00
[Table view]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 Manual Reactor Trip ENS 568262023-11-01T10:48:0001 November 2023 10:48:00 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 Manual Reactor Trip Due to Trip of Reactor Feed Pump ENS 564462023-03-31T18:32:00031 March 2023 18:32:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Scram and Automatic Actuation of Containment Isolation Valves (Civs) ENS 556792021-12-29T20:52:00029 December 2021 20:52:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip and Automatic Actuation of Containment Isolation Valves ENS 553942021-08-03T14:26:0003 August 2021 14:26:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip ENS 539532019-03-24T05:59:00024 March 2019 05:59:00 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 Condenser Vacuum ENS 538932019-02-23T07:12:00023 February 2019 07:12:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Actuation of 2C Emergency Diesel Generator ENS 527002017-04-21T03:45:00021 April 2017 03:45:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Reactor Protection System Actuation While Shutdown ENS 525582017-02-16T18:20:00016 February 2017 18:20:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unexpected Autostart of an Emergency Diesel Generator ENS 519502016-05-23T14:09:00023 May 2016 14:09:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Plant Hatch Unit 2 Containment Isolation Valve Actuation ENS 487602013-02-16T08:10:00016 February 2013 08:10:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Protection System Scram Signal Due to Scram Discharge Volume High Level ENS 487382013-02-10T12:00:00010 February 2013 12:00:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Scram Inserted Due to Degrading Reactor Water Chemistry ENS 473692011-10-24T20:11:00024 October 2011 20:11:00 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 Erratic Irm Indications During Startup ENS 458502010-04-16T23:17:00016 April 2010 23:17:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Loss of Cooling Accident Signal Due to High Drywell Pressure Signal ENS 451482009-06-23T07:51:00023 June 2009 07:51:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Scram Due to High Reactor Water Level ENS 450712009-05-15T09:19:00015 May 2009 09:19:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Group 1 Isolation of All Main Steam Valves While Performing a Special Procedure ENS 450522009-05-10T14:41:00010 May 2009 14:41:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Intermediate Range Reactor Scram During Transition to Run ENS 450492009-05-08T19:15:0008 May 2009 19:15:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Inadvertant Main Steam Isolation While Performing Maintenance ENS 446792008-11-22T15:18:00022 November 2008 15:18:00 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 Manual Reactor Scram After Feed Pump Trip ENS 443372008-07-04T12:39:0004 July 2008 12:39:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Scram on Turbine Trip ENS 440462008-03-07T19:46:0007 March 2008 19:46:00 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 Reactor Scram with Hpci/Rcic Actuation Due to Loss of Condensate Feedwater ENS 435522007-08-07T19:06:0007 August 2007 19:06:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Scram on Low Reactor Water Level Following Partial Loss of Condensate Feedwater Flow ENS 420962005-10-29T17:25:00029 October 2005 17:25:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unusual Event - Main Transformer Fire ENS 417252005-05-23T21:47:00023 May 2005 21:47:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Scram Due to Condenser Hotwell Chemistry ENS 410702004-09-25T05:06:00025 September 2004 05:06:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Group 2 Containment Isolation Actuation ENS 405652004-03-03T18:45:0003 March 2004 18:45:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Swing Diesel Generator Auto Started from a Bus Undervoltage Valid Signal 2024-03-11T17:37:00 | |
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