Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 47940 | 21 May 2012 18:35:00 | At 1452 CDT on 5/21/2012 with the reactor at 100% power, River Bend Station experienced a reactor scram resulting from an RPS actuation. Following the scram, reactor water level briefly lowered below level 3. The reactor is stable with pressure and temperature being controlled by the feed water system and main steam bypass valves, respectfully. The cause of the scram was due to a turbine trip/low condenser vacuum. The low vacuum condition resulted from a loss of non-safety related 4160V switchgear that powers two of four circulating water pumps. A suspected spurious Division II isolation of Reactor Core Isolation Cooling (RCIC) was observed. Restoration of RCIC to standby is in progress. A report of a fire in a manhole was received shortly after the scram . Fire Brigade was dispatched and noted a small active fire in a cable tray. The fire was extinguished with fire extinguishers. Power cables are routed through this manhole. The plant is conducting causal investigations to fully understand the cause of the turbine trip. As information becomes available, River Bend Station will provide additional information. All rods are inserted, and the plant is in a normal shutdown electrical lineup with the exception of NNS-Switchgear 2A being deenergized. Offsite assistance was not required to extinguish the fire. The licensee notified the NRC Resident Inspector. |
| ENS 43904 | 14 January 2008 17:05:00 | At 1610 hours, on 1/14/2008, the Main Control Room annunciator system will be removed from service to support activities for a planned maintenance outage at River Bend Station. The duration of the work is expected to be completed in less than 1 hour. During this time, other Control Room indications and alternate methods will be available to implement the Emergency Plan. Since the Main Control Room annunciator System will be unavailable, this is considered a Loss of Emergency Assessment Capability and reportable under 10CFR50.72(b)(3)(xiii). A follow-up notification will be made to the NRC after the Main Control Room annunciator system is returned to service. The licensee notified the NRC Resident Inspector. No major systems in LCOs at this time and the only major ongoing activity is Fuel Handling.
Main control room annunciator system has been restored to service at 1708 CST. The licensee notified the NRC Resident Inspector. Notified R4DO (Spitzberg). |
| ENS 43901 | 13 January 2008 11:36:00 | Planned Maintenance on Safety Parameter Display System (SPDS) and Emergency Response Data System (ERDS). At 1036 CST hours, on 1/13/2008, the SPDS and ERDS system will be removed from service to support activities for a planned maintenance outage at River Bend Station. The duration of work is expected to be approximately 8 hours. During this time, Control Room indications and alternate methods will be available to implement the Emergency Plan. Since the SPDS computer system will be unavailable for greater than 2 hours, this is considered a Loss of Emergency Assessment Capability and reportable under 10CFR50.72(b)(3)(xiii). A follow-up notification will be made to the NRC after the SPDS and ERDS are returned to service. The licensee notified the NRC Resident Inspector. * * * UPDATE AT 1844 ON 1/13/08 FROM HUSTON TO SNYDER * * * The SPDS and ERDS systems have been returned to service at 1745. The licensee will notify the NRC Resident Inspector. Notified R4DO (Bywater). |
| ENS 43773 | 7 November 2007 07:58:00 | With the plant in Mode 1 at (approximately) 75% power, the Auxiliary boiler and water treatment building 480 volt switchgear (NJS-SWG1J) faulted. The fault resulted in the loss of the NPS A bus (13.8 Kv normal supply), causing condensate and feed pumps to trip. Operators in the control room immediately responded and the plant was manually scrammed at 0306. Both the high pressure core spray (HPCS) and the reactor core isolation cooling (RCIC) systems responded automatically and injected into the vessel (valid ECCS signal). Safety systems responded as expected, including level 2 isolations. The licensee believes a transformer fault may have transferred up the line and caused the loss of normal power supply. RCIC is controlling reactor water level with primary plant pressure approximately 325 psia. Decay heat is being controlled through modulating the SRV's. The licensee has all systems available to place the unit in safe shutdown and cooldown. The licensee has one inoperable EDG and is not in any technical specification action statement at this time. The licensee notified the NRC Resident Inspector.
The high pressure core spray system was returned to its standby lineup at 0318 (all times are CST). Standby service water was being placed in service at 0701 to raise service water header pressure when standby service water pump 'C' started automatically. NPS 13.8kv switchgear 'A' was restored to service at 1245. The reactor core isolation cooling system, which automatically started at the time of the event, was shutdown at 1645. The Division 3 diesel generator, which automatically started at the time of the event, was restored to its standby lineup at 1429. Shutdown cooling was placed in service with residual heat removal pump 'A', at 1626. The plant entered Mode 4 (cold shutdown) at 1942. The electrical fault that initiated the event has been isolated to a 13.8kv/480v transformer in the turbine building. An investigation is ongoing. The licensee notified the NRC Resident Inspector. Notified the R4DO (Spitzberg) and NRR (Lubinski). |
| ENS 43668 | 27 September 2007 03:48:00 | At approximately 2244 on September 26, 2007 an unplanned reactor scram occurred. An Average Power Range Monitor (APRM) surveillance was being performed at the time. This surveillance should not have caused a full scram and the cause of the scram is under investigation. The plant responded to the scram as expected, all control rods fully inserted, and there is no need for emergency injection system operation. Critical parameters are being maintained within prescribed bands and the plant has been stabilized. A level 3 signal was received during this scram which would have caused an isolation but all affected valves were already in the closed position. This event is being reported in accordance with 10CFR50.72(b)(2)(iv)(B) as an event that results in activation of the reactor protection system with the reactor critical. All emergency systems are available and in standby mode. The licensee notified the NRC Resident Inspector. |
| ENS 41252 | 10 December 2004 17:34:00 | At 1317 (hrs CST) on December 10, 2004, an automatic actuation of the reactor protection system (RPS) occurred resulting in a reactor scram. The apparent cause of the event was loss of a vital instrument bus due to a fault in a nonsafety related vital inverter. This inverter provides power to selected control room instrumentation and controls. This resulted in the loss of feed water level control. Reactor level is being maintained by the High Pressure Core Spray System. The feed water system is not available. Reactor pressure is being controlled through the main turbine steam bypass system to the condenser. The condenser is available and being used as the heat sink. The residual heat removal system was operated in suppression pool cooling mode to provide a means of rejecting water from the suppression pool (water input from High Pressure Core Spray System minimum flow line). The plant is currently stable, and being maintained in hot shutdown. Systems responded as expected based on the initiating event. Reactor Core Isolation Cooling is not being used pending evaluation of a system alarm that is currently being investigated. Investigation of the initiating fault is being pursued in order to recover the vital bus and feed water level control. It has been preliminarily determined that the loss of instrument power resulted in the Main Feedwater regulating valve failing as-is and the "B" Reactor Recirculation Pump shifting down in speed. The reduction in reactor power with constant feed flow resulted in a high reactor vessel water level, producing a direct reactor scram signal at the High Level 8 setpoint. The licensee has notified the NRC Resident Inspector.
At 1657 CST (on 12/10/04), reactor level control was restored to the normal Feedwater and Condensate Systems. The High Pressure Core Spray System was restored to the normal standby lineup. Investigation into the cause of the reported RPS actuation continues. Investigation into the Reactor Core Isolation Cooling System alarms has resulted in declaring this system inoperable. The licensee will notify the NRC Resident Inspector. Notified R4 DO (L. Smith), NRR EO (M. Tschiltz) and IRD Manager (S. Frant)
The final determination of the cause of the scram was determined to be due to the B recirc pump downshift and subsequent power to flow scram on APRM flux. The licensee will notify the NRC Resident Inspector. Notified R4DO (L Smith)
The Reactor Core Cooling System was returned to available status at 0343 on 12/11/2004 and was restored to operable status at 2200 on 12/11/2004." The licensee notified the NRC Resident Inspector. Notified R4DO (Kriss Kennedy). |