ENS 46971
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ENS Event | |
|---|---|
15:52 Jun 20, 2011 | |
| Title | Unit 2 Reactor Trip Following the Loss of the "B" Main Feedwater (Mfw) Pump |
| Event Description | At 1152 EDT on 6/20/11 while operating at 60% power, the "B" MFW Pump tripped for reasons unknown. There was no maintenance or I&C work on-going at the time involving this pump. Operators initiated a manual reactor trip, however, [they] are not certain whether the automatic reactor trip setpoint of 49.5% Steam Generator Water Level Narrow Range (SGWL NR) was reached first. SGWL decreased to the Auxiliary Feedwater (AFW) setpoint of 26.8% NR causing the initiation of both motor-driven AFW Pumps. All Control Rods fully inserted.
Unit 2 is currently stable in Mode 3, Hot Standby, removing decay heat via the Main Steam line to the Condenser. Operators secured AFW and will initiate feed to the Steam Generators using the "A" MFW Pump. Unit 2 is in a normal post-trip electrical lineup with all sources of offsite power available. The licensee has the cause of the "B" MFW Pump trip under investigation. The licensee informed both state/local (Waterford Dispatch) and the NRC Resident Inspector |
| Where | |
|---|---|
Millstone  Connecticut (NRC Region 1) | |
| 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:+-2.85 h-0.119 days <br />-0.017 weeks <br />-0.0039 months <br />) | |
| Opened: | Fred Perkins 13:01 Jun 20, 2011 |
| NRC Officer: | Steve Sandin |
| Last Updated: | Jun 20, 2011 |
| 46971 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (60 %) |
| After | Hot Standby (0 %) |
Millstone with 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
WEEKMONTHYEARENS 576942025-05-07T01:08:0007 May 2025 01:08:00
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Circulating Water Pumps ENS 416072005-04-17T12:42:00017 April 2005 12:42:00 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, 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge Alert Declared Due to Unit 3 Main Steam Relief Valves Not Reseating After Actuation ENS 405912004-03-16T01:20:00016 March 2004 01:20:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip at Millstone 2 Due to Spurious Loss of One Main Feed Pump ENS 405702004-03-06T05:50:0006 March 2004 05:50:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip at Millstone 2 Due to Spurious Trip of the "B" Feed Pump ENS 403612003-11-29T03:05:00029 November 2003 03:05:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip from 11% Power Due to Turbine Vibration ENS 403582003-11-27T11:29:00027 November 2003 11:29:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Plant Had a Manual Reactor Trip from 23% Power Due to Turbine Vibration 2025-05-07T01:08:00 | |
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