ENS 42738
ENS Event | |
|---|---|
19:50 Jul 29, 2006 | |
| Title | |
| Event Description | {{#Wiki_filter:At 15:50 EDT on 7/29/06, a Level 3 reactor scram occurred due to a loss of feedwater. The loss of feedwater was caused by a loss of Division 1 electrical power. All control rods fully inserted into the core. The lowest reactor vessel water level reached was 110 inches. HPCI and RCIC auto initiated on Level 2 and injected into the reactor pressure vessel. The Division 1 Emergency Diesel Generators auto initiated and supplied the Division 1 ESF buses. Level 3 and Level 2 isolations occurred as expected. Reactor water level is now being controlled in the normal water level band using Standby Feedwater. No SRVs lifted and RPV pressure is being controlled by the Turbine Pressure Regulator with the main condenser available as the heat sink.
At the time of the scram, work was being performed on the 120kV mat which resulted in a loss of Bus 101. Group 13 (Drywell Sumps) isolated on Reactor Water Level 3. Group 10 (Reactor Water Cleanup Inboard), Group 11 (Reactor Water Cleanup Outboard), Group 12 (Torus Water Management System), Group 17 ( Reactor Recirc Pump Seals and Primary Containment Radiation Monitoring), and Group 18 (Primary Containment Pneumatic Supply) isolated on Reactor Water Level 2. The licensee notified the NRC Resident Inspector. The licensee stated that HPCI injected for 2 minutes and was then secured as Standby Feedwater was started. At the time of the notification, Bus 101 had been re-energized, and preparations were being made to restore normal power to the Division 1 buses and return the Emergency Diesel Generators to standby. The licensee is investigating the exact cause of the loss of power.
The purpose of this report is to update the information provided at 19:19 ET on 7/29/2006. This event was originally reported under reporting criteria 50.72(b)(2)(iv)(A) as an ECCS injection. It has subsequently been determined that both the HPCI and RCIC systems auto-started in response to a reactor low water level 2 (Level 2) injection signal, however, only the RCIC system injected into the vessel. The Level 2 signal was only present for about 2.7 seconds until reactor water level recovered above Level 2. The HPCI injection logic is such that the Level 2 signal must be present until HPCI startup has completed. This includes time for the hydraulic pressure from the HPCI Auxiliary Oil Pump to develop enough pressure to open the HPCI turbine steam isolation valve (E4100F067) and time to stroke open the motor operated HPCI turbine steam isolation valve (E4100F001). It took about 12 seconds before steam was admitted to the HPCI turbine. Thus, the HPCI main pump outlet valve (E4150F006) did not open due to the short duration of the Level 2 signal. This is consistent with the HPCI system design. Therefore the event was not reportable as an event that resulted in or should have resulted in an ECCS injection into the reactor vessel. The event remains reportable under criteria 50.72(b)(2)(iv)(B) and 50.72(b)(3)(iv)(A). Additional clarification of the cause of the scram is also provided. The loss of bus 101 resulted in the loss of power to the operating south reactor feed pump (SRFP) turbine lube oil pump resulting in a loss of feedwater flow from the SRFP. The north reactor feed pump continued to operate. The plant is designed with an automatic runback of the recirculation system to allow continued operation following the loss of a single feed pump. However, the loss of bus 101 also resulted in the locking of the reactor recirculation pump speeds (scoop tube lock), disabling the runback feature. This led to a reactor scram on reactor low water level 3 (Level 3) since a single feed pump is not able to maintain reactor water level at 100% power operation. When south reactor feed pump lubrication pressure recovered, feedwater flow from the SRFP recovered. Recovering feedwater injection from the SRFP following the scram caused a rapid increase in reactor water level and a high reactor water level 8 (Level 8) shutdown of the HPCI, RCIC and reactor feedwater pumps. The standby feedwater system was subsequently started and used to maintain reactor level. The plant is restarting, and is in Mode 2 with reactor temperature at approximately 508�F and reactor pressure at approximately 817 psi at the time of this report. Based on this update, ECCS injection was removed from CFR Section of the report. The licensee notified the NRC Resident Inspector. Notified R3 DO (K. O'Brien) }} |
| Where | |
|---|---|
Fermi  Michigan (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(iv)(B), RPS Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| LER: | 05000341/LER-2006-003 |
| Time - Person (Reporting Time:+-0.52 h-0.0217 days <br />-0.0031 weeks <br />-7.12296e-4 months <br />) | |
| Opened: | Jim Konrad 19:19 Jul 29, 2006 |
| NRC Officer: | Mike Ripley |
| Last Updated: | Jul 31, 2006 |
| 42738 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (100 %) |
| After | Hot Shutdown (0 %) |
Fermi with 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
WEEKMONTHYEARENS 570462024-03-23T04:04:00023 March 2024 04:04:00
[Table view]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 Automatic Reactor Trip ENS 559642022-06-25T03:38:00025 June 2022 03:38:00 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 Main Turbine Trip ENS 557322022-02-04T22:00:0004 February 2022 22:00:00 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 547612020-07-02T03:05:0002 July 2020 03:05:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Loss of Offsite Power - Auto Initiation of Emergency Diesel Generator ENS 533362018-04-14T14:40:00014 April 2018 14:40:00 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 Automatic Reactor Scram and Emergency Core Cooling System Injection ENS 513912015-09-14T03:05:00014 September 2015 03:05:00 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)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Manual Scram Due to Loss of Turbine Building Closed Cooling Water ENS 509032015-03-19T11:02:00019 March 2015 11:02:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Scram Due to an Oscillation Power Range Monitor Upscale Actuation ENS 484872012-11-07T14:21:0007 November 2012 14:21:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Shutdown Due to Hydrogen In-Leakage to Stator Water Cooling System ENS 483092012-09-14T20:03:00014 September 2012 20:03:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge Automatic Reactor Scram Due to the Loss of the 120 Kv Switchyard ENS 480472012-06-25T17:30:00025 June 2012 17:30:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Reactor Feed Pump Trip Results in Manual Reactor Scram ENS 478682012-04-26T14:12:00026 April 2012 14:12:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Actuation of the Reactor Protection System During Testing ENS 463592010-10-24T20:41:00024 October 2010 20:41:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Scram Due to a Turbine Trip Resulting from a Low Condenser Vacuum ENS 459792010-06-06T06:38:0006 June 2010 06:38:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Automatic Reactor Scram Due to Partial Loss of Offsite Power ENS 457892010-03-25T20:27:00025 March 2010 20:27:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Shutdown Due to Main Turbine Trip ENS 453942009-09-30T15:09:00030 September 2009 15:09:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Shutdown Due to Hydrogen In-Leakage to Stator Water Cooling System ENS 449422009-03-28T05:46:00028 March 2009 05:46:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Reactor Scram Due to Mode Switch Being Placed in Shutdown Following High Vibration on Main Turbine #1 Bearing ENS 439482008-01-31T20:44:00031 January 2008 20:44:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Scram in Response to Trip of Both Reactor Recirc Pumps ENS 437842007-11-15T08:13:00015 November 2007 08:13:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Reactor Scram - Initiation of Ari Caused by Level 2 Signal ENS 427382006-07-29T19:50:00029 July 2006 19:50:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Scram and Eccs Injection Due to Loss of Feedwater ENS 426432006-06-15T14:53:00015 June 2006 14:53:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Scram Due to Turbine Trip ENS 413542005-01-24T21:10:00024 January 2005 21:10:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Due to Unidentified Leakage Greater than 10 Gpm ENS 412432004-12-04T09:17:0004 December 2004 09:17:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Scram Due to an Auto Voltage Regulator Trip ENS 410172004-09-04T03:45:0004 September 2004 03:45:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Rps Actuation 2024-03-23T04:04:00 | |