ENS 45960
ENS Event | |
|---|---|
04:03 May 28, 2010 | |
| Title | Automatic Reactor Trip Due to Loss of Reactor Coolant Pump |
| Event Description | A Unit-2 reactor trip was initiated by a loss of the Unit-2 'B' station service bus. The loss of the 'B' station service bus caused a reactor trip due to the loss of flow on one-of-three loops due to the loss of the 'B' Reactor Coolant Pump. The Auxiliary Feed Water system actuated as expected due to the reactor trip. The plant was stabilized in Mode 3 using the appropriate emergency procedure.
During the transient, the 'B' Reserve Station Service Transformer de-energized and the Unit-2 'H' Emergency Diesel Generator was previously tagged out for planned maintenance. This resulted in the Unit-2 'H' emergency bus being de-energized. The alternate AC diesel generator has been placed in service and is providing power to the Unit-2 'H' emergency bus. The automatic tap changer for the 'C' reserve station service transformer did not work in automatic and had to be manually adjusted to control voltage. Unit-2 'C' Reactor Coolant Pump remains in service. All control rods fully inserted on the trip and no relief valves lifted or safety valves lifted in either the primary or secondary systems. The turbine drive and 'B' motor driven Auxiliary Feed Water pumps automatically started and injected into the 'A' and 'B' steam generators on a low level signal. The 'A' motor driven Auxiliary Feed Water pump failed to start due to the loss of the 'H' emergency bus. The 'C' steam generator is being controlled with main feed water though the 'C' main feed regulating valve bypass valve. Decay heat removal is via the condenser steam dumps. The licensee has notified the NRC Resident Inspector.
EN#45960 reported the RPS Actuation (50.72(b)(2)(iv)(B)) and AFW System Actuation (50.72(b)(3)(iv)(A). The event occurred at 0003 EDT on May 28, 2010. Technical Specification (TS) 3.0.3 was entered at 0004 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> on May 28, 2010, for inoperable offsite power sources with the 2H emergency diesel generator (EDG) being inoperable per TS 3.8.1. M. Update: At the time of the event, the station was experiencing a severe lightning storm. The Auxiliary Feedwater System was returned to auto standby at 0558 hours0.00646 days <br />0.155 hours <br />9.22619e-4 weeks <br />2.12319e-4 months <br />. At approximately 0942 hours0.0109 days <br />0.262 hours <br />0.00156 weeks <br />3.58431e-4 months <br />, RCS cooldown to Mode 4 was started on Unit 2. Mode 4 was entered at 1245 hours0.0144 days <br />0.346 hours <br />0.00206 weeks <br />4.737225e-4 months <br />. The 'A' and 'B' RCPs remain secured in Mode 4. Following repairs and post maintenance testing the 'C' reserve station service transformer (RSST) was declared operable at 1324 hours0.0153 days <br />0.368 hours <br />0.00219 weeks <br />5.03782e-4 months <br />. This restored two (2) qualified offsite circuits for Unit 1 and one (1) qualified offsite circuit for Unit 2. TS 3.0.3 was cleared at this time on Unit 2. The 'B' RSST remains out of service (OOS) pending repairs and testing. The Unit 2 'B' station service bus remains OOS. The 2H EDG previously reported OOS for scheduled maintenance is expected to be returned to service on Monday, May 31, 2010. The alternate AC diesel generator continues to supply power to the 2H emergency bus. Limiting action remains for one (1) offsite circuit for Unit 2 being inoperable along with the 2H EDG OOS. The licensee will be notifying the NRC Resident Inspector. Notified R2DO (Haag). |
| Where | |
|---|---|
North Anna  Virginia (NRC Region 2) | |
| 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:+-0.33 h-0.0138 days <br />-0.00196 weeks <br />-4.52034e-4 months <br />) | |
| Opened: | Brian Scott 03:43 May 28, 2010 |
| NRC Officer: | Charles Teal |
| Last Updated: | May 28, 2010 |
| 45960 - NRC Website | |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (100 %) |
| After | Hot Standby (0 %) |
North Anna with 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
WEEKMONTHYEARENS 558432022-04-14T13:28:00014 April 2022 13:28:00
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ECCS Discharge Reactor Trip and Spurious Safety Injection ENS 432172007-03-07T08:05:0007 March 2007 08:05:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Emergency Diesel Generator Autostart on Loss of "B" Reserve Station Service Transformer ENS 430722007-01-03T23:03:0003 January 2007 23:03:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Due to a Card Failure ENS 429962006-11-16T07:26:00016 November 2006 07:26:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Trip ENS 424832006-04-08T02:31:0008 April 2006 02:31:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Group Step Counter Failure During Reactor Startup ENS 418982005-08-06T02:28:0006 August 2005 02:28:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Apparently Due to Lightning Strike ENS 408042004-06-10T17:13:00010 June 2004 17:13:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip While Performing Scheduled Solid State Protection Testing ENS 407842004-05-29T06:02:00029 May 2004 06:02:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Control Rod Position Indication Failure During Hot Rod Drop Test 2022-04-14T13:28:00 | |