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 Entered dateSiteScramRegionReactor typeEvent description
ENS 531921 February 2018 14:23:00River BendManual ScramNRC Region 4GE-6

At 1057 CST on February 1, 2018 with the unit in Mode 1 at approximately 27% power, a manual actuation of the Reactor Protection System (RPS) was initiated due to an unexpected trip of the B Recirc Pump with A Recirc Pump in fast speed. B Recirc Pump tripped during transfer from slow to fast speed resulting in single loop operation. Operators were unable to reconcile differing indications of core flow. This resulted in a conservative decision to initiate a manual scram. The cause of the B Recirc Pump trip and the apparent issues with core flow indication are under investigation. The plant is currently stable in Mode 3. The plant response to the scram was as expected. All control rods (fully) inserted as expected; the feedwater system is maintaining reactor vessel water level in the normal control band and reactor pressure is being maintained with steam line drains and main turbine bypass valves. The NRC Senior Resident (Inspector) has been notified.

  • * * RETRACTION AT 1015 EDT ON 03/22/2018 FROM DAVID DABADIE TO OSSY FONT * * *

This event was initially reported under 10 CFR 72(b)(2)(iv)(B) as a manual actuation of the RPS due to an unexpected trip of the B Reactor Recirculation Pump with the A Reactor Recirculation Pump running in fast speed (Single Loop Operations). Operations was unable to reconcile differing indications of core flow and made the conservative decision to perform a planned shutdown in accordance with normal operating procedures. Therefore, this event 'resulted from and was part of a pre-planned sequence during testing or reactor operation' as specified in 10 CFR 50.72(b)(2)(iv)(B), 10 CFR 50.73(a)(2)(iv)(A) and NUREG-1022 Section 3.2.6. Consequently, this event is not reportable as an actuation of RPS. The NRC Resident Inspector has been notified. R4DO (Groom) has been notified.

ENS 5318830 January 2018 21:56:00Grand GulfManual ScramNRC Region 4GE-6On 1/30/2018 at 1750 (CST), the Reactor Pressure Control Malfunctions ONEP (Off Normal Event Procedure) was entered due to main turbine load oscillations of approximately 30 MWe peak to peak. At 1822 (CST), a manual reactor scram was inserted by placing the Reactor Mode Switch in Shutdown due to continued main turbine load oscillations. Reactor SCRAM ONEP, Turbine Trip ONEP, and EP-2 were entered. Reactor water level was stabilized at 36 inches narrow range on startup level and reactor pressure stabilized at 933 psig using main turbine bypass valves. Reactor Water Level 3 (11.4 inches) was reached which is the setpoint for Group 2 (RHR to Radwaste Isolation) and Group 3 (Shutdown Cooling Isolation). No valve isolated in these systems due to all isolation valves in these groups being in their normally closed position. The lowest Reactor Water level reached was -36 inches wide range. No other safety system actuations occurred and all systems performed as designed. That event is being reported under 10CFR 50.72(b)(2)(iv)(B) as any event or condition that results in actuation of the Reactor Protection System (RPS), when the reactor is critical and also reported under 10CFR 50.72(b)(3)(iv)(A), as any event or condition that results in actuation of RPS. The MSIVs are open with decay heat being removed via steam to the main condenser using the bypass valves. Off site power is stable, and the plant is in a normal shutdown electrical lineup. RCIC (Reactor Core Isolation Cooling) was out of service for maintenance, and the reactor water level did not reach the system activation level. The cause of the main turbine load oscillations being investigated. The licensee notified the NRC Resident Inspector.
ENS 531109 December 2017 18:42:00ClintonManual ScramNRC Region 3GE-6

At approximately 1347 (CST) on 12/09/17, the Main Control Room received annunciators that indicated a trip of the 4160 V 1A1 breaker 1AP07EJ, 480V XFMR 1A and A1 breaker. Numerous Division 1 components lost power (powered from unit subs 1A and A1). The Division 1 containment Instrument Air isolation valves had failed closed by design due to the loss of power. Due to the loss of containment instrument air, several control rods began to drift into the core as expected and, by procedure, the reactor mode switch was placed in the shutdown position at 1353 (CST). All control rods fully inserted. Also due to the loss of power, the Fuel Building ventilation dampers failed closed by design. With the normal ventilation system secured, secondary containment differential pressure rose to slightly greater than 0 inches water gauge which exceeded the Technical Specification requirement of greater than 0.25 inches vacuum water gauge at 1348 (CST). The Control Room entered EOP-8, Secondary Containment Control. Secondary Containment differential pressure was restored within Technical Specification requirements at 1351 (CST) by starting the Division 2 Standby Gas Treatment system. This event is being reported as a manual actuation of the Reactor Protection System (RPS) and as a Condition that Could Have Prevented Fulfillment of a Safety Function.

The cause is currently under investigation. The NRC Resident has been notified. The licensee informed the NRC Resident Inspector.

  • * * UPDATE FROM DALE SHELTON TO VINCE KLCO AT 1658 EST ON 12/10/2017 * * *

During a review of plant logs it was identified that the primary to secondary containment differential pressure was identified to be outside of Technical Specification 3.6.1.4 limits of 0 plus or minus 0.25 psid at 2009 on 12/9/17 due to the primary containment ventilation system dampers closing as a result of the loss of power. This parameter is an initial safety analysis assumption to ensure that primary containment pressures remain within the design values during a Loss of Coolant Accident (LOCA). As a result, this condition is reportable as an unanalyzed condition that significantly degrades plant safety. The NRC Senior Resident Inspector has been notified. Notified the R3DO (Stone).

  • * * UPDATE FROM MICHAEL ANTONELLI TO VINCE KLCO ON 12/11/17 AT 1805 EST * * *

During the post transient review of the trip of the 4160 V 1A1 breaker 1AP07EJ, 480V XFMR 1A and A1, it was identified that the unplanned INOPERABILITY of the Low Pressure Core Spray (LPCS) system due to the loss of power to the injection valve constitutes an event or condition that could have prevented fulfillment of a safety function and is reportable under 10CFR50.72(b)(3)(v)(D) for Accident Mitigation. The High Pressure Core Spray (HPCS) remained available to perform the core spray function, if necessary, during a design basis Loss of Coolant Accident (LOCA), however HPCS and LPCS are each considered single train safety systems. The NRC Senior Resident Inspector has been notified. Notified the R3DO (Stone).

ENS 5309025 November 2017 06:02:00Grand GulfManual ScramNRC Region 4GE-6

At 0238 (CST) a manual reactor scram was inserted by placing the Reactor Mode Switch in Shutdown. At 0149 (CST), with reactor power just above the point of adding heat, IRM (Intermediate Range Monitor) channels A, C, and D received a spurious upscale trip signal which immediately cleared. Upon investigation, operability of RPS (Reactor Protection System) scram function for Intermediate Range Detectors was placed in question. This event is being reported under 10 CFR 50.72(b)(2)(iv)(B), as any event or condition that results in actuation of the Reactor Protection System (RPS), when the reactor is critical. The licensee notified the NRC Resident Inspector.

  • * * UPDATE ON NOVEMBER 26, 2017, AT 1850 FROM GRAND GULF TO MICHAEL BLOODGOOD * * *

At 0238 (CST) a manual reactor scram was inserted by placing the Reactor Mode Switch in Shutdown. At 0149 (CST), with reactor power just above the point of adding heat, Intermediate Range Monitor neutron flux detector (IRM) channels A, C, and D received a spurious Upscale Trip signal which immediately cleared. Upon investigation, IRM channels A, C, and D were declared Inoperable. IRM G was already Inoperable for another reason. RPS scram function from IRM channels B, E, F, and H was always Operable and available. That event is being reported under 10CFR 50.72(b)(2)(iv)(B), as any event or condition that results in actuation of the Reactor Protection System (RPS), when the reactor is critical. This Revised Statement to Event Notification # 53090 is being made to make it clear that only four IRM channels (A, C, D, G) were Inoperable and that the IRM RPS SCRAM function was still available from the four remaining Operable IRM channels (B, E, F, and H). The licensee notified the NRC Resident Inspector. Notified R4DO (O'Keefe)

  • * * RETRACTION ON 01/16/2018 AT 1629 EST FROM JASON COMFORT TO DAVID AIRD * * *

On 11/25/17, at 0149 (CST), with reactor power just above the point of adding heat, Intermediate Range Monitor neutron flux detector (IRM) channels A, C, and D received a spurious Upscale Trip signal which immediately cleared. Upon investigation, IRM channels A, C, and D were declared Inoperable. IRM G was already Inoperable for another reason. At 0238 (CST) a manual reactor scram was inserted by placing the Reactor Mode Switch in Shutdown. RPS scram function from IRM channels B, E, F, and H was always Operable and available. That event was initially being reported under 10 CFR 50.72(b)(2)(iv)(B), as any event or condition that results in actuation of the Reactor Protection System (RPS), when the reactor is critical. After the trip alarms were received, the Operators spent approximately twenty minutes investigating possible causes and implications, and consulted with Reactor Engineering and the Shift Technical Advisor. The investigation showed that the plant was stable and the upscale IRM alarms were spurious. A review of plant technical specifications by the operators determined that a plant shutdown was not required. After further discussions, Operations concluded that a shutdown to allow further investigation of the issue was the prudent course of action. Prior to shutting down, Operations spent approximately twenty minutes reviewing procedures, notifying personnel to exit containment, and conducting a brief. The shutdown was then conducted by inserting a manual reactor scram by placing the reactor mode switch in SHUTDOWN. This was initially reported under 10 CFR 50.72(b)(2)(iv)(B) as an actuation of the RPS. Based on the sequence of events, and Operator actions in conducting the shutdown, the event is considered 'part of a pre-planned sequence during testing or reactor operation' as specified in 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.73(a)(2)(iv)(A). In accordance with NUREG-1022, Section 3.2.6, the event is not reportable as an actuation of RPS. The licensee notified the NRC Resident Inspector. Notified R4DO (Taylor).

ENS 5291518 August 2017 23:41:00River BendAutomatic ScramNRC Region 4GE-6At 2055 CDT on August 18, 2017, an automatic actuation of the reactor protection system occurred while the plant was operating at 100 percent power. No plant parameters requiring the actuation of the emergency diesel generators or the emergency core cooling system were exceeded. The main feedwater system remained in service following the scram to maintain reactor water level, and the main condenser remained available as the normal heat sink. The scram occurred after a planned swap of the main feedwater master controller channels in preparation for scheduled surveillance testing. When the channel swap was actuated, the feedwater regulating valves moved to the fully open position. The scram signal originated in the high-flux detection function of the average power range monitors, apparently from the rapid increase in feedwater flow. The cause of the apparent feedwater controller malfunction is under investigation. The NRC Resident Inspector has been notified. No safety relief valves opened. Decay heat is being removed via steam to the main condenser using the bypass valves and steam drains. The licensee intends to go to Cold Shutdown to investigate the malfunction.
ENS 5282523 June 2017 23:58:00River BendAutomatic ScramNRC Region 4GE-6While performing a scheduled generator voltage regulator test, River Bend Station experienced an automatic scram when the main generator tripped. It is unknown at this time why the main generator tripped. There were no equipment issues that materially impacted post scram operator response. The intention at this time is to go to cold shutdown while the cause of the trip is investigated. All rods inserted during the scram. Reactor water level is being maintained via normal feedwater with decay heat being removed via turbine bypass valves to the main condenser. The electrical grid is stable and supplying plant loads via the normal shutdown electrical lineup. The licensee has notified the NRC Resident Inspector.
ENS 5280011 June 2017 01:00:00ClintonManual ScramNRC Region 3GE-6At 2256 CDT on 6/10/17, Clinton operators manually scrammed the reactor from 99 percent power due to a loss of feedwater heating. The scram was uncomplicated and the plant is stable and in mode 3. All rods inserted and decay heat is being removed by the condenser. All offsite power is available. The cause of the loss of feedwater heating is under investigation. The NRC Resident Inspector and the State of Illinois have been notified.
ENS 527273 May 2017 12:59:00PerryManual ScramNRC Region 3GE-6On April 30, 2017, at 1818 (EDT), the main turbine steam bypass valve #1 partially opened. Power was incrementally lowered. While lowering power the bypass valve would shut and then reopen and power would again be lowered. When power was lowered to approximately 74 percent the bypass valve remained closed. During the transient the reactor protection system (RPS) Turbine Stop Valve Closure and Control Valve Fast Closure trip functions were declared inoperable due to the opening of the bypass valve which affects the bypass setpoint for those RPS trip functions. With the loss of these RPS trip functions a loss of safety function existed intermittently for approximately 37 minutes. The manual reactor trip function and other RPS functions remained operable. Both channels of the rod withdrawal limiter (RWL) and the end of cycle reactor recirculation pump trip (EOC-RPT) function were also declared inoperable. These functions are credited in accident analysis, this also resulted in a loss of safety function. Currently the bypass valve is closed and the RWL, EOC-RPT and RPS function are operable. Troubleshooting continues to determine the issue with the main turbine that caused the bypass valve to open. NRC Resident Inspector has been notified.
ENS 526634 April 2017 06:57:00Grand GulfManual ScramNRC Region 4GE-6At 0010 (CDT), 04/04/2017, the reactor was manually scrammed from approximately 75 (percent) core thermal power due Condensate Storage tank level lowering to 24 feet. All control rods fully inserted and all systems actuated and operated as designed. No safety relief valves actuated. Reactor level and pressure are currently being controlled within normal bands. RCIC (reactor core isolation cooling) was manually initiated for level control. This event is reportable under 10CFR50.72(b)(2)(iv)(B) for the reactor trip and 50.72(b)(3)(iv)(A) for the manual start of the reactor core isolation cooling system. The cause of lowering level was a condensate pipe leak. Decay heat is being removed via steam dumps to the condenser. The electrical grid is stable and supplying plant loads. The licensee has notified the NRC Resident Inspector.
ENS 5260210 March 2017 11:41:00River BendManual ScramNRC Region 4GE-6At 0714 CST on March 10, 2017, with the unit in Mode 1 at approximately 17% power, a manual actuation of the reactor protection system (RPS) was initiated due to rising reactor pressure caused by the closure of the Main Turbine Control Valves (MTCV's). The cause of the closure of the MTCV's is under investigation. The unit is currently stable in Mode 3. All control rods inserted as expected; water level control is stable in the normal control band and reactor pressure is being maintained with steam line drains (aligned to the main condenser). The NRC Senior Resident Inspector has been notified.
ENS 5204425 June 2016 18:30:00Grand GulfAutomatic ScramNRC Region 4GE-6At 1407 (CDT), during power ascension to 100 percent, turbine control valves closed unexpectedly causing reactor protection trip signals that in turn caused a reactor scram. Reactor scram, turbine trip ONEPs (Off Normal Event Procedure), and EP2 (Emergency Procedure for Level Control) were entered. Reactor water level was stabilized at 36 inches narrow range on startup level and reactor pressure stabilized at 935 psig using bypass valves. No other safety system actuations occurred and all systems performed as designed. All control rods inserted. Reactor level is maintained by feedwater. Normal electrical shutdown configuration is through offsite electrical power sources. The Safety Relief Valves lifted, then closed. The plant is stable at normal level and pressure and remains in Mode 3. The event is under licensee investigation. The licensee notified the NRC Resident Inspector.
ENS 5201217 June 2016 06:21:00Grand GulfAutomatic ScramNRC Region 4GE-6During planned stop and control valve testing, two main turbine high pressure stop valves closed instead of the expected one (stop valve 'B'). This caused the main turbine control valves, power, reactor pressure to swing and a division 2 half SCRAM. Control rods were inserted to reduce power and the power swings. At 0257 (CDT) the reactor automatically SCRAMMED. Reactor SCRAM, Turbine Trip (procedures) ONEPs and EP-2 were entered. Reactor water level was stabilized at 34 inches narrow range on startup level control and reactor pressure stabilized at 884 psig using main turbine bypass valves. No other safety related systems actuated and all systems performed as expected. The plant is in its normal shutdown electrical lineup using normal feedwater and turbine bypass valves for decay heat removal. Reactor pressure is slowly trending down. The licensee is investigating the cause of the second stop valve shutting. The licensee notified the NRC Resident Inspector.
ENS 517168 February 2016 17:50:00PerryManual ScramNRC Region 3GE-6At 1500 EST on February 8, 2016, two safety relief valves (SRV) opened upon a spurious Division 2 initiation signal. This caused suppression pool temperature to increase. At 1503 EST, plant operators took action to manually SCRAM the reactor at 95 degrees Fahrenheit in the suppression pool per plant procedures. The SRVs closed immediately following the scram at 1503 EST. The cause of the SRVs opening is currently under investigation. During the scram, all rods fully inserted into the core. Reactor Pressure is stable with decay heat being removed via turbine bypass valves to the main condenser. Reactor level control is currently being maintained via feedwater. Main Steam Isolation Valves are open. Cool down and depressurization to Mode 4 to follow. The plant is in a normal post SCRAM electrical line-up. The licensee notified the NRC Resident Inspector.
ENS 5168124 January 2016 11:23:00PerryManual ScramNRC Region 3GE-6At 0357 hours (EST) on January 24, 2016, during a shut down required by plant Technical Specifications (see EN#51679), the 3A Feedwater heater isolated while performing a Reactor Recirculation Pump downshift. A consequence of this Feedwater heater isolation was that all 8 of the Average Power Range Monitors (APRM) became inoperable due to a calibration set point being out of tolerance. The APRM's are relied upon for the reactors high neutron flux trips. The inoperable APRM's resulted in a loss of RPS Trip Capability and a loss of safety function. The manual reactor trip function and other RPS functions remained available. RPS Trip capability for the APRM's was restored at 0445 hours on January 24, 2016. This notification is being made under (10 CFR) 50.72(b)(3)(v)(A) for an event or condition that could have prevented the fulfillment of a safety function affecting the ability to shut down the reactor. The licensee has notified the NRC Resident Inspector.
ENS 516449 January 2016 07:04:00River BendAutomatic ScramNRC Region 4GE-6On 1/9/16 at 0237 (CST), River Bend Station sustained a reactor scram during a lightning storm. An electrical transient occurred resulting in a full main steam isolation (MSIV) (Group 6) and a Division II Balance of Plant isolation signal. During the scram, level 8 occurred immediately which tripped the feed pumps. A level 3 signal occurred also during the scram. Subsequent level 3 was received three times due to isolated vessel level control. The plant was stabilized and all spurious isolation signals reset, then the MSIVs were restored. The plant is now stable in Mode 3 and plant walkdowns are occurring to assess the transient. During the scram, all rods inserted into the core. The plant was initially cooled down using safety relief valves. Offsite power is available and the plant is in its normal shutdown electrical lineup. The licensee has notified the NRC Resident Inspector.
ENS 5156827 November 2015 09:23:00River BendAutomatic ScramNRC Region 4GE-6At 0431 CST on November 27, 2015, an automatic reactor scram occurred following the trip of the main generator. The generator trip was apparently caused by a partial loss of offsite power, which resulted from a differential ground on the north bus of the local 230 kV switchyard. The ground signal caused the reserve station service line no. 1 to de-energize, which tripped the Division 1 offsite power source to station, as well as the main generator. The plant responded as designed as follows: The Division 1 emergency diesel generator started and tied to the bus restoring Division 1 emergency power. The Division 3 emergency diesel generator started and tied to the bus, restoring power on the Division 3 switchgear. The reactor protection system tripped as designed. Reactor water level was controlled normally with condensate and feed water. A level 3 reactor water level scram signal occurred as expected, and RPV (Reactor Pressure Vessel) water level was restored to normal level band. Reactor pressure was controlled by the bypass valve system, and a normal cool down was initiated. The reactor is being taken to cold shutdown pending an investigation of the event. The loss of power also resulted in a partial loss of normal service water cooling to the plant, and emergency service water cooling automatically initiated per design. At the time of event, the reactor protection system was aligned to the backup power supply, which was momentarily lost. This resulted in multiple system isolations including reactor water clean up, and outboard balance of plant isolations. These isolations were initiated due to loss of offsite power, and all responded as designed. The isolation resulted in a loss of the running decay heat removal pump for the spent fuel pool. The standby pump is available for service and being aligned for service. The plant is currently stable in hot shutdown. Transmission and distribution personnel are currently investigating the ground in the 230 kV switchyard. All control rods inserted. The licensee has notified the NRC Resident Inspector.
ENS 511122 June 2015 02:00:00River BendAutomatic ScramNRC Region 4GE-6

At 2111 (CDT) River Bend Nuclear Station sustained an Automatic Reactor Scram due to low Reactor Water Level (Level 3). The plant is currently stable, with level being maintained in a normal band of 10 - 51 inches with Condensate and Feedwater. Reactor Pressure is in the prescribed band of 500-1090 psig. The plant is in Mode 3, Hot Shutdown, and will remain in Mode 3 until investigation of the scram is complete. The transient began with a trip of Reactor Feed Pump 'A', followed by a Reactor Scram and a trip of Reactor Feed Pump 'C'. Reactor water level was recovered with Reactor Feed Pump 'B' to a normal post scram level band. There was a problem noted with the Reactor Feedwater Master Level Controller; this was mitigated by the Operator placing the controller to manual. There was no subsequent Level transient. Reactor Pressure was stabilized in normal pressure band with Turbine bypass valves. During the transient, a Reactor Recirculating Flow Control Valve Runback was not received as expected. Reactor Recirculating Pump 'A' responded as expected to transient (switching to low pump speed), Reactor Recirculating Pump 'B' tripped during transient. A Level 3 isolation signal was received, all expected isolations occurred. The cause of the transient is currently under investigation. The reactor is stable in Mode 3 with decay heat being removed via turbine bypass valves, and a normal electrical line up. The NRC Resident Inspector has been notified.

  • * * UPDATE FROM JACK MCCOY TO HOWIE CROUCH AT 0712 EDT ON 6/2/15 * * *

At 2231 on 6/1/15, Reactor Water Cleanup System isolated on High Reactor Water Cleanup System Heat Exchanger room temperature due to loss of Turbine Building chill water during the initial transient. All Reactor Water Cleanup System Valves isolated as expected. Reactor Water Cleanup was the only system affected by this isolation signal. The licensee has notified the NRC Resident Inspector. Notified R4DO (Whitten).

ENS 5100322 April 2015 14:18:00River BendAutomatic ScramNRC Region 4GE-6On February 24, 2015, at approximately 1702 CDT, while the plant was in cold shutdown, power was lost on the Division 1 reactor protection system (RPS) bus. This event resulted in the automatic closure of the Division 1 primary containment isolation valves in the residual heat removal (RHR) and reactor water cleanup systems. Additionally, the primary containment atmospheric monitoring system automatically actuated, and ventilation systems in the fuel building, auxiliary building, and control building shifted to emergency mode. The closure of the isolation valves in the residual heat removal system caused an automatic trip of the 'A' RHR pump, which had been in the shutdown cooling alignment. The equipment response to the isolation signal was as expected. This event is being reported in accordance with 10 CFR 50.73(a)(1) as an invalid actuation of the Division 1 primary containment isolation system. The isolation was promptly diagnosed as having resulted from a trip of the output breaker of the RPS motor generator (MG) set 'A,' and not from a valid signal. Operators implemented the appropriate response procedures to align power to the bus via the alternate source, and began restoring the affected systems. The 'A' RHR pump was re-started within twelve minutes, during which time coolant temperature increased approximately seven degrees to a maximum of approximately 100F. Other affected systems were restored over the next few hours. The causal analysis concluded that the MG set output breaker tripped due to an overly conservative setpoint on the overvoltage trip relay. The low trip setpoint was a latent condition that had existed since the output voltage was raised in 1988 at the recommendation of the vendor, but at which time the trip setpoint was not changed. To correct this condition, the MG overvoltage trip setpoint was raised to restore adequate operating margin to the normal MG output voltage. At the time of the event, the plant was in MODE 5 with the reactor cavity flooded to greater than 23 feet above the vessel flange. The shutdown cooling system was promptly restored to service. This event was of minimal safety significance to the health and safety of employees and the public. The licensee has notified the NRC Resident Inspector.
ENS 506017 November 2014 11:13:00PerryAutomatic ScramNRC Region 3GE-6The Perry Nuclear Power Plant experienced an automatic reactor scram due to a loss of feedwater, which resulted in receiving valid reactor vessel water Level 3 and Level 2 initiation signals. The High Pressure Core Spray system and the Reactor Core Isolation Cooling system started and injected. Reactor water level and pressure have been stabilized in the required bands. The motor feed pump automatically started and is being used to control reactor vessel water level. The High Pressure Core Spray and Reactor Core Isolation Cooling systems have been returned to the standby mode. As a result of receiving a reactor vessel water Level 2 signal a Balance of Plant containment isolation signal was received. All systems isolated as required and the plant is restoring isolated systems in accordance with plant procedures. During the scram, all rods fully inserted into the core. Decay heat is being removed via turbine bypass valves to the main condenser. The electrical grid is stable and is supplying plant loads. An emergency diesel generator (Division 3 High Pressure Core Spray) started, as designed, as a result of the reactor vessel water Level 2 signal. No safety relief valves lifted as a result of the transient. The plant is stable with cooldown and depressurization to Mode 4 in progress. The cause of the loss of feedwater is under investigation. The NRC Resident Inspector has been notified. The State of Ohio and local officials will be notified.
ENS 5055120 October 2014 03:55:00PerryAutomatic ScramNRC Region 3GE-6

The Perry Power Plant experienced a reactor scram during a shift of non-essential vital power supply to the alternate source. Feedwater was lost resulting in receiving a valid level 3 and level 2 signal. High Pressure Core Spray and Reactor Core Isolation Cooling started and injected. Reactor level and pressure have been stabilized to required bands. The motor feed pump has been started and is controlling level. High Pressure Core Spray and Reactor Core Isolation Cooling have been returned to standby. During the scram, all rods fully inserted into the core. Decay heat is being removed via the steam dumps to the condenser. The electrical grid is stable and supplying plant loads. An emergency diesel generator started, as designed, as a result of the level 2 signal but did not load. No safety valves lifted as a result of the transient. The cause of the loss of feedwater is under investigation. The licensee will be notifying the State of Ohio and Perry Township and has notified the NRC Resident Inspector.

  • * * UPDATE FROM DOUG SHORTER TO HOWIE CROUCH AT 0933 EDT ON 10/20/14 * * *

The plant is currently in Mode 3, stable with cooldown and depressurization to Mode 4 in progress. Level control is being provided by the motor feedwater pump. Troubleshooting of the cause of the scram and loss of feed water is on-going. The initial notification identified 10CFR50.72(b)(3)(iv)(A), 'Specified System Actuation', as a reporting criteria. The specific system that actuated was not provided. As a result of receiving a reactor vessel water level 2 signal a containment/BOP isolation signal was received. All systems isolated as required and the plant is restoring isolated systems in accordance with procedure. The licensee will be notifying the State of Ohio and Perry Township and has notified the NRC Resident Inspector. Notified R3DO (Pelke).

ENS 5054617 October 2014 07:46:00River BendAutomatic ScramNRC Region 4GE-6

At 0303 (CDT), River Bend Nuclear Station sustained a reactor scram due to high Average Power Range Monitor (APRM) flux, suspected due to a malfunction of the Electrohydraulic Control System. Reactor recirculation pump 'B' tripped, reactor recirculation pump 'A' responded appropriately. All other systems responded appropriately except for loss of feed water due to low suction pressure trip from isolating the condensate demineralizers. Reactor water level did not get out of level band. Condensate demineralizers and feedwater were restored to service. Level 3 (isolation) was initiated due to scram. (One) system, Suppression Pool Cooling isolated accordingly due to level 3 signal. Currently the plant is in mode 3, hot shutdown. Plant will remain in mode 3 until investigation of scram is complete. During the scram, all rods inserted into the core. No relief valves lifted as a result of the transient. All safety equipment is available although reactor core isolation cooling is functional but inoperable due to an earlier issue discovered during a surveillance test. The reactor is at normal pressure and temperature for Mode 3. The cause of the high APRM flux and the identified anomalies are under investigation. The licensee has notified the NRC Resident Inspector.

  • * * UPDATE FROM DANIEL PIPKIN TO DANIEL MILLS AT 1043 EDT ON 10/17/2014 * * *

The licensee is updating the notification to include an 8 hour notification for a specified system actuation due to the Level 3 isolation signal. Licensee is proceeding to cold shutdown to troubleshoot the EHC system. The licensee will notify the NRC Resident Inspector. Notified R4DO (Haire).

ENS 4997229 March 2014 14:09:00Grand GulfAutomatic ScramNRC Region 4GE-6Actuation of RPS with reactor critical. Reactor Scram occurred at 1008 (CDT) on 03/29/2014 from 87% CTP (core thermal power). The cause of the Scram appears to be a Turbine Generator Trip. 05-S-01-EP-2 RPV Control, 05-1-02-I-1 Reactor Scram ONEP and 05-1-02-l-2 Turbine Generator Trip ONEP were entered to mitigate the transient with all systems responding as designed. No loss of offsite or ESF (engineered safety feature) power occurred. No ECCS (emergency core cooling systems) initiation signals were reached and no ESF or Diesel Generator initiations occurred. All control rods are fully inserted. MSIVs (main steam isolation valve) remained open and no SRVs (safety relief valves) lifted. Currently, reactor water level is being maintained by the Condensate and Feedwater system in normal band and reactor pressure is being controlled via Main Turbine Bypass Valves to the main condenser. There are no challenges to Primary or Secondary Containment at this time. The licensee has notified the NRC Resident Inspector.
ENS 4995825 March 2014 22:44:00ClintonManual ScramNRC Region 3GE-6The plant was stable at 85 percent power when off-gas flow started lowering. The operating crew entered the loss of vacuum off-normal procedure and commenced an emergency power reduction to attempt to slow/halt the loss of vacuum while attempting various prescribed actions in the off-normal procedure. When vacuum reached 24 in. Hg, a rapid plant shutdown was performed as prescribed in the off-normal procedure. Power was at 46 percent when a rapid plant shutdown was commenced with the mode switch placed in shutdown at 1942 CDT. All control rods fully inserted on the scram, no emergency core cooling system injected or was required, no safety/relief valve(s) lifted and all systems responded as expected on the scram. The plant will remain in mode 3 with normal makeup from the feedwater system and pressure control on the turbine bypass valves with the main condenser available as a heat sink. All vital and non-vital electrical busses are powered from reserve off-site sources and no emergency diesel generators started on the scram. The cause of the loss of vacuum is under investigation. The licensee notified the NRC Resident Inspector.
ENS 4992017 March 2014 09:25:00Grand GulfManual ScramNRC Region 4GE-6On 3/17/2014 at 0514 (CDT) the reactor was manually scrammed from approximately 41% core thermal power due to a steam leak in the turbine building. All control rods fully inserted and all systems actuated and operated as designed. All Main Steam Isolation Valves were manually shut. The Reactor Core Isolation Cooling System was manually initiated to assist in level control and pressure control. No safety relief valves actuated automatically. Manual cycling of safety relief valves and Reactor Core Isolation Cooling are being used to maintain reactor water level and pressure within normal bands. Group 2 and 3 RHR isolation signals were received; however no valve movement occurred since the affected valves are normally closed. This event is reportable under 10CFR50.72(b)(2)(iv)(B) for the reactor trip and 50.72(b)(3)(iv)(A) for the manual start of the reactor core isolation cooling system. The licensee informed the NRC Resident Inspector.
ENS 4963213 December 2013 20:07:00ClintonManual Scram
Scram
NRC Region 3GE-6During a feed pump shift from the motor driven reactor feed pump to the 'A' turbine driven reactor feed pump during power ascension, reactor pressure vessel (RPV) water level was approaching the Reactor Protective System (RPS) automatic scram set point when a manual reactor scram was inserted. All control rods fully inserted. RPV water level is being maintained by the normal condensate booster / feedwater systems. RPV pressure is being maintained via normal main steam system. There were no actuations of any Emergency Core Cooling System and no Safety Relief Valves actuations. All systems responded as expected. The licensee notified the NRC Resident Inspector.
ENS 496179 December 2013 01:15:00ClintonManual ScramNRC Region 3GE-6While operating at rated electrical power, the station experienced a transformer fault which resulted in a loss of Division 1 480 VAC power. This resulted in the operators inserting a Manual Scram due to loss of Instrument Air to Containment and the scram air header. On the scram, all control rods fully inserted and no safety relief valves lifted. Reactor vessel level is being maintained by normal feedwater and decay heat is being removed via steam to the main condenser through the steam bypass valves. The plant is currently in Mode 3 and proceeding to Mode 4 to comply with Technical Specification requirements. The plant is in a normal shutdown electrical lineup with the exception of the loss of Division 1 480 VAC power. Reporting in accordance with 10CFR50.72(b)(3)(v)(C) due to loss of normal ventilation to secondary containment which resulted in a positive secondary containment pressure for approximately 15 minutes. Secondary Containment required pressure was restored at 2043 CST. Reporting in accordance with 10CFR50.72(b)(3)(v)(D) due to loss of Division 1 480 VAC power resulting in loss of a single train of Low Pressure Core Spray. The licensee has notified the NRC Resident Inspector.
ENS 4897426 April 2013 12:55:00ClintonManual ScramNRC Region 3GE-6On 4/26/13 at about 0855 CDT while operating at rated electrical power, operators initiated a manual reactor scram due to rapidly decreasing level in the main Electro Hydraulic Control (EHC) oil reservoir. All systems responded as expected with no complications. The cause of the main EHC decrease in level is under investigation. The plant is stable in mode 3. The NRC Resident Inspector has been notified. The licensee reports that bypass valves remain available via a separate EHC system and decay heat is being routed to the condenser.
ENS 488127 March 2013 11:52:00ClintonAutomatic ScramNRC Region 3GE-6While operating at rated electrical power, a main generator trip and subsequent turbine trip resulted in a reactor scram. The cause of the generator trip is under investigation. All systems operated as expected with no complications. The plant is stable in Mode 3. The licensee notified the NRC Resident Inspector and the State of Illinois.
ENS 4867314 January 2013 22:04:00Grand GulfAutomatic ScramNRC Region 4GE-6Actuation of RPS (Reactor Protection System) with reactor critical. The Reactor Scram occurred at 1805 (CST) 01/14/13 from 100% CTP (Core Thermal Power). The cause of scram appears to be a Turbine Generator Trip. 05-S-01-EP-2 RPV Control, Reactor Scram ONEP (Off Normal Event Procedure) 05-1-02-I-1, and Turbine and Generator Trips ONEP 05-1-02-1-2 were entered to mitigate the transient with all systems responding as designed. No loss of offsite or ESF power occurred. No ECCS initiation signals were reached and no ECCS or Diesel Generator initiation occurred. All control rods are fully inserted. MSIVs remained open and SRVs lifted and reseated as designed. Currently, reactor water level is being maintained by the Condensate and Feedwater system in the normal band and reactor pressure is being controlled via Main Turbine Bypass valves to the main condenser. There are no challenges to Primary or Secondary Containment at this time. The licensee notified the NRC Resident Inspector.
ENS 486525 January 2013 03:09:00Grand GulfAutomatic ScramNRC Region 4GE-6Actuation of RPS with reactor critical. Reactor Scram occurred at 2337 CST 01/04/13 from 94% CTP (Core Thermal Power). The cause of the scram appears to be a Generator/Turbine trip. Appropriate off normal event procedures were entered to mitigate the transient with all systems responding as designed. No loss of offsite or ESF power occurred. No ECCS initiation signals were reached and no ECCS or Diesel Generator initiation occurred. MSIVs remained open and SRVs lifted and reseated as designed. Currently, reactor water level is being maintained by the Condensate and Feedwater system in normal band and reactor pressure is being controlled via bypass valves to the condenser. The NRC Resident Inspector has been informed. See similar EN #48637.
ENS 4863729 December 2012 05:05:00Grand GulfAutomatic ScramNRC Region 4GE-6Actuation of RPS (Reactor Protection System) with reactor critical. Reactor Scram occurred at 0018 (CST), 12/29/12, from 100% CTP (Core Thermal Power). The cause of scram appears to be a Generator/Turbine trip. Appropriate off normal event procedures were entered to mitigate the transient with all systems responding as designed. No loss of offsite or ESF (engineered safety feature) power occurred. No ECCS initiation signals were reached and no ECCS or Diesel Generator initiation occurred. MSIVs (Main Steam Isolation Valves) remained open and SRVs (Safety Relief Valves) lifted. Currently, reactor water level is being maintained by the condensate and feedwater system in normal band and reactor pressure is being controlled to limit cooldown. All control rods inserted. The plant is in hot shutdown with decay heat removal to the condenser and the electrical line-up is in a normal configuration. The cause of the turbine/generator trip is under investigation. The licensee notified the NRC Resident Inspector.
ENS 4796024 May 2012 18:04:00River BendManual ScramNRC Region 4GE-6At 1348 CDT on 5/24/12 with the Reactor at 33% power, River Bend Station operators inserted a manual reactor scram based on loss of high pressure feed to the reactor following a loss of a 13.8 Kv switchgear. The Control Room team observed an electrical transient in the Control Room concurrent with the start of Reactor Feed Pump "B". The crew identified that no high pressure feed was aligned to the reactor and inserted a manual scram. Based on the configuration of the electrical plant during startup, all circulating water and Normal Service Water (NSW) was supplied from NPS-SWG1B. MSIVs were closed based on loss of circulating water and Standby Service Water (SSW) initiated automatically based on loss of NSW. EOP-0001, 'RPV Control' was entered on reactor high pressure and reactor low water level. EOP-0002, 'Primary Containment Control' was entered based on primary containment pressure high and suppression pool level high. EOP-0003, 'Secondary Containment Control', was entered on annulus pressure high. Reactor water level control is being maintained with Reactor Core Isolation Cooling (RCIC). High pressure core spray was manually started but was not required and was subsequently shut down. Pressure control is via RCIC and Safety Relief Valves (SRVs). Safety related busses are aligned to offsite power as normal. They were not affected by the electrical transient. Immediately after the scram at 1350, a report from the Turbine Building indicated smoke was seen around the Reactor Feed Pump 'B' termination cabinet. The Fire Brigade was activated. At 1358, the Fire Brigade reported that there was no fire. A review of the Emergency Action Levels (EALs) was performed. No emergency declaration was required. Initial investigation shows damage to cabling and circuit boards associated with Reactor Feedpump 'B' in the Turbine Building, but no fire was ever observed. In addition, the Technical Support Center (TSC) and Operations Support Center (OSC) lost power. At the time, both facilities continued to be in a state of readiness and emergency functions could be performed. At 1526, power was restored to both facilities, including the ventilation systems. All rods inserted into the core. The unit is stable at 230 psi and 391 degrees F. Reactor pressure is maintained by RCIC and decay heat removal via safety relief valves to the suppression pool. The unit is in a technical specification for suppression pool high level. There were no safety system failures. There is one non safety related 13.8 switchgear out of service due to this event and NNS-Switchgear 2A out of service from an event three days ago. Offsite assistance was not required. The NRC Resident Inspector has been notified.
ENS 4794021 May 2012 18:35:00River BendAutomatic ScramNRC Region 4GE-6At 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 477101 March 2012 05:51:00PerryManual ScramNRC Region 3GE-6On March 1,2012, at approximately 0224 (EST), a manual Reactor Protection System (RPS) actuation was initiated due to 3 turbine bypass valves going open as a result of an automatic turbine runback signal. At the time of the event, the plant was in Mode 1 at 100% power. All control rods are inserted into the core and the plant is currently stable in Mode 3 (Hot Shutdown) with reactor pressure at approximately 930 psig. No Emergency Core Cooling Systems were required or utilized to respond to the event and there were no other reportable actuations. Reactor coolant level is being maintained in its normal band by the feedwater system and decay heat is being removed by the condenser. The plant is in a normal electrical line-up with all three Emergency Diesel Generators operable and available if needed. The cause of the automatic turbine runback has not been determined and is being investigated. During the transient, Reactor Water Cleanup System (RWCU) tripped. No automatic isolation signal was received. At the time of the event, restoration of a Stator Water Cooling pressure gauge was being performed (following maintenance). The NRC Resident Inspector has been notified.
ENS 4767919 February 2012 22:00:00Grand GulfManual ScramNRC Region 4GE-6On 2/19/2012 at 1904 hrs (CST) the reactor was manually scrammed from approximately 23% core thermal power due to lowering reactor water level. All control rods fully inserted and all systems actuated and operated as designed. The Reactor Core Isolation Cooling System was manually initiated to assist in level control. No safety relief valves actuated. Reactor level and pressure are currently being controlled within normal bands. Group 2 and 3 RHR Isolation signals were received, however no valve movement occurred since the affected valves are normally closed. This event is reportable under 10CFR50.72(b)(2)(iv)(B) for the reactor trip and 50.72(b)(iv)(A) for the manual start of the core isolation cooling system. The lowest Reactor Vessel Water Level (RVWL) observed was -38 inches WR (Wide Range). RVWL was restored by placing the "A" Reactor Feed Pump (RFP) in service. The "B" RFP which had been operating was secured for troubleshooting. The Unit was in the process of shutting down for its scheduled Refueling Outage #18. The NRC Resident Inspector was in the control room at the time of the transient.
ENS 4754923 December 2011 10:10:00River BendAutomatic ScramNRC Region 4GE-6At 0610 CST on 12/23/2011 with the reactor at 100% power, River Bend Station experienced an (automatic) reactor scram resulting from a RPS actuation. Following the scram, reactor water level briefly lowered below level 3, resulting in the automatic closure of containment isolation valves in the suppression pool cooling system. This isolation was confirmed to have occurred as designed. The reactor is stable with pressure and temperature being controlled by the feed water system and main steam bypass valves, respectively. The cause of the scram was due to a turbine trip. Initial indications are that the turbine tripped due to a loss speed sensor. All control rods inserted and Reactor Core Isolation Cooling was manually operated for approximately 1 minute and secured, 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. This event is being reported in accordance with 10CFR50.72(b)(iv)(B) as an automatic RPS actuation with the reactor critical. The safety relief valves momentarily lifted immediately following the scram. The plant electrical distribution system is in a normal shutdown configuration. The scram was uncomplicated. The licensee notified the NRC Resident Inspector.
ENS 4753318 December 2011 18:08:00ClintonAutomatic ScramNRC Region 3GE-6On 12/18/11 at approximately 0930 CST, with the plant in Mode 4, while Operations was lowering reactor water level as part of restoration activities following the Reactor Pressure Vessel hydrostatic test, an automatic reactor scram and Residual Heat Removal (RHR) 'A' pump trip occurred due to a valid Reactor Water Level Low (Level 3) signal. The cause of the low level appears to be due a significant disparity between the Upset and Shutdown Range level instrumentation and the Level 3 RPS (Reactor Protection System) instrumentation. No rod motion occurred during the reactor scram as all control rods were fully inserted at the time of the event. Operations immediately entered the station off-normal procedures for Loss of Shutdown Cooling and Reactor Scram. The 'A' RHR pump was restored at 0956 CST. Reactor coolant temperature increased from approximately 128.7 deg F to 131.7 deg F during the event. At 1112 CST, the scram was reset and at 1216 CST, the off-normal procedures were exited. Following the event as part of trouble shooting, maintenance personnel performed a fill and vent of reactor water level transmitter, 1B21N027. At the completion of this fill and vent, indicated water level changed from 195" to 86" on Shutdown Range and from off-scale high (>180") to 103"on Upset Range. No change in other reactor water level indication was observed. This event is reportable under 10 CFR 50.72 (b)(3)(v)(B), as an event or condition that could have prevented the fulfillment of a safety function needed to remove residual heat, and 10 CFR 50.72 (b)(3)(iv)(A), event or condition that results in a valid actuation of the reactor protection system (RPS). The licensee has notified the NRC Resident Inspector.
ENS 4748929 November 2011 21:47:00ClintonAutomatic ScramNRC Region 3GE-6During a planned shutdown in preparation for refueling outage C1R13, shortly after tripping the main turbine, an automatic reactor scram occurred due to high reactor steam dome pressure. Preliminarily, per the plant process computer, the reactor pressure was observed to reach approximately 1074 psig approximately 26 seconds after main steam bypass valves unexpectedly closed. An investigation will be conducted to determine the cause of the bypass valve closure and reactor scram. No safety relief valves lifted as a result of the pressure increase. This event is being reported under 10 CFR 50.72(b)(2)(iv)(B) as an event or condition that results in actuation of the reactor protection system when the reactor was critical. The licensee is manually controlling the steam bypass valves to remove decay heat via the main condenser. All control rods fully inserted. The Unit is in a normal shutdown electrical lineup. The licensee informed the NRC Resident Inspector.
ENS 4591812 May 2010 03:12:00PerryManual ScramNRC Region 3GE-6On May 11, 2010, at approximately 2318 hours, a manual Reactor Protection System (RPS) actuation was initiated as required by Technical Specification (TS) Limiting Condition for Operation (LCO) 3.1.5 'Control Rod Scram Accumulators.' Control Rod Drive (CRD) charging water header pressure was less than 1520 psig (i.e., no CRD pumps operating) and there were multiple accumulator faults on withdrawn control rods. At the time of the event, the plant was in Mode 1 at 100% power. All control rods are inserted into the core and the plant is currently stable, in Mode 3 (Hot Shutdown) with reactor pressure at approximately 930 psig. No Emergency Core Cooling Systems were required or utilized to respond to the event and there were no other 10 CFR 50.72 reportable actuations. Reactor coolant level is being maintained in its normal band by the feedwater system and decay heat is being removed by the condenser. The plant is in a normal electrical line-up with all three Emergency Diesel Generators operable and available if needed. The cause of the event initiator, an invalid Division 2 Loss of Coolant Accident (LOCA), i.e., High Drywell Pressure/Low Reactor Vessel Water Level, signal, is currently under investigation. Prior to the manual RPS Actuation, the invalid LOCA signal resulted in invalid actuations of Division 2 equipment and systems including, the Division 2 Emergency Diesel Generator (EDG), (which started but did not load onto the bus), Low Pressure Coolant Injection B and C subsystems (which started the pumps but did not inject into the vessel), discharge of the Suppression Pool Makeup subsystem B into the suppression pool, startup of the Control Room Emergency Recirculation subsystem B, and isolation of Group 2B Containment isolation valves which included the Nuclear Closed Cooling System Containment Return Isolation valve that was not already closed. The affected equipment is being restored in accordance with plant procedure. The NRC Resident Inspector has been notified. The licensee experienced an instrumentation rack loss of power which appears to have resulted in the inadvertent Division 2 initiation. The initiator of this event also and led to a loss of power to both control rod drive charging water header pumps resulting in charging water header pressure less than required and related accumulator faults which placed the licensee in a technical specification required shutdown condition. The action statement allows only 20 minutes to restore the condition which was insufficient time for the licensee to correct the condition so a manual scram was initiated from 100% power. The scram was characterized as an uncomplicated scram and all system responses (not related to the initial instrument fault) functioned as required.
ENS 457538 March 2010 19:47:00Grand GulfAutomatic ScramNRC Region 4GE-6An 'A' reactor feed pump trip occurred and initiated a recirculation pump flow control valve runback. During the flow control valve runback, the 'A' recirculation hydraulic power unit tripped causing an incomplete runback. Reactor water level 3 (11.4 inches) was reached which is an RPS scram setpoint and also a setpoint for Group 2 (RHR to Radwaste) and Group 3 (Shutdown Cooling Isolation). No valves isolated in these systems due to (the valves) being in their normally closed position. The lowest reactor water level reached was -28 inches wide range. Appropriate off normal event procedures were entered to mitigate the transient with all systems responding as designed. No loss of offsite or ESF power occurred. No ECCS initiation signals were reached, and no ECCS or Diesel Generator initiation occurred. All safety systems performed as expected. MSIVs remained open and no SRVs lifted. Main condenser and pressure control systems remained in service. Currently, reactor water level is being maintained by the condensate and feedwater system in the normal level band and reactor pressure is being controlled to limit cooldown. During the scram, all rods inserted into the core. The plant is in its normal shutdown electrical lineup. Decay heat removal is via the steam bypass valves to the condenser. The licensee has notified the NRC Resident Inspector.
ENS 4544016 October 2009 01:48:00PerryManual ScramNRC Region 3GE-6On October 16, 2009 at 0048 a manual reactor scram was inserted at the Perry Nuclear Plant. The plant was conducting a planned shutdown due to the Division 2 Emergency Service Water inoperability. While shifting reactor recirculation pumps to slow speed the 'A' pump failed to transfer and tripped off. Following stabilization from this event a manual reactor scram was inserted from approximately 30% power. This was different from the initial planned shutdown sequence. Following the scram all systems operated as expected. The plant is stable in Mode 3. The plant will transition to Mode 4 in accordance with Technical Specification 3.7.1 (Emergency Service Water Inoperability) required actions. All control rods fully inserted and the plant electrical power is in a normal line-up. The licensee notified the NRC Resident Inspector.
ENS 4543315 October 2009 09:06:00ClintonManual Scram
Automatic Scram
NRC Region 3GE-6At 0537 hours on October 15, 2009, the 'B' Reactor Recirculation pump tripped. The reactor mode switch was placed in shutdown due to rising reactor water level (approx. 49 inches) prior to the Level 8 automatic scram setpoint (52 inches). All controls rods inserted as a result of the manual scram. All systems performed as expected. Reactor water level is being controlled by the motor driven feedwater pump. Main steam isolation valves were manually closed and decay heat was initially controlled through the main steam line drains to the main condenser via the main turbine bypass valves. Reactor Core Isolation Cooling (RCIC) was manually placed into service (tank-to-tank) to assist in RPV pressure control. RCIC is currently being used for decay heat removal. Investigation is underway to determine the cause of the Reactor Recirculation pump trip. The licensee will be contacting the state, and issuing a press release. The NRC Senior Resident Inspector has been notified.
ENS 4536920 September 2009 21:32:00River BendManual ScramNRC Region 4GE-6At 1747 hours on September 20, 2009, at River Bend Station, during plant shut down for a planned outage, an unplanned manual reactor scram was initiated by plant operators. As part of the planned shutdown, the reactor recirculation pumps were being transferred from fast to slow speed. This transfer did not occur as expected. Instead, the pumps tripped to off. After this occurred, the operators entered the manual reactor scram. Power level was approximately 23 percent at the time of the scram. All other plant equipment and systems performed as expected. Plant personnel are investigating the cause of the pump trip. The plant is proceeding with planned outage activities. All rods fully inserted. Decay heat is being removed via main steam drains and bypass valves to the condenser. Reactor pressure is at 200 psig. The electrical lineup is normal and all safety related equipment is available if required. No safety or relief valves lifted during the manual scram. The licensee has notified the NRC Resident Inspector.
ENS 4514721 June 2009 20:58:00PerryAutomatic ScramNRC Region 3GE-6On June 21, 2009, at approximately 1750 hours, an automatic Reactor Protection System (RPS) actuation occurred at the Perry Nuclear Power Plant, Unit 1. At the time of the event, the plant was in Mode 1 at 100% power. All control rods are inserted into the core and the plant is currently stable, in Mode 3 (Hot Shutdown) with reactor pressure at approximately 930 psig. No Emergency Core Cooling Systems were required or utilized to respond to the event and there were no other reportable actuations. Reactor coolant level is being maintained in its normal band by the feedwater system and decay heat is being removed by the condenser. The plant is in a normal electrical line-up with all three Emergency Diesel Generators operable and available if needed. The cause of the reactor scram is currently under investigation. Preliminary indications are that the cause of the RPS actuation is related to a main turbine trip. The NRC Resident Inspector has been notified. No safety relief valves lifted during the event and a reactor cooldown is in progress.
ENS 4460126 October 2008 15:40:00Grand GulfAutomatic ScramNRC Region 4GE-6Actuation of RPS with reactor critical. Reactor Scram occurred at 11:25, 10/26/08 from approximately 50% CTP (core thermal power). A turbine/generator trip and automatic RPS reactor scram on TCV (turbine control valve) fast closure occurred. Exact cause of turbine/generator trip is not known at this time. All withdrawn control rods fully inserted to position 00. Reactor Water Level 3 (11.4") was reached which is an RPS Scram Setpoint and also a setpoint for Group 2 (RHR to Radwaste) and Group 3 (Shutdown Cooling Isolation). No valves isolated in these systems due to their being in their normally closed position. Lowest reactor water level reached was -3" Wide Range. Appropriate off normal event procedures were entered to mitigate the transient with all systems responding as designed. No loss of offsite or ESF power occurred. No ECCS initiation signals were reached, and no ECCS or DG initiation occurred. All safety systems performed as expected. MSIVs remained open and no SRV's lifted. Main Condenser and pressure control system remained in service. Currently, reactor water level is being maintained by the condensate system in normal level band and reactor pressure is being controlled to limit cooldown. The licensee notified the NRC Resident Inspector.
ENS 4459523 October 2008 11:44:00Grand GulfAutomatic ScramNRC Region 4GE-6'A' Reactor Feed Pump speed decreased to zero with no trip signal evident in the Control Room for the 'A' Reactor Feed Pump. The reactor scrammed due to loss of feedwater flow on a Level 3 (11.4") RPS scram signal as designed. Operators implemented appropriate off normal event procedures to mitigate the transient with all systems responding as designed. Lowest reactor water level observed was -35" wide range. All withdrawn control rods fully inserted to position '00'. The Reactor Core Isolation Cooling System was manually initiated and was used to restore water level to within the normal band. No ECCS initiations were received and all systems responded as designed. Additionally, no SRVs lifted as a result of this event. Level 3 is also a setpoint for Group 2 (RHR to Radwaste) and Group 3 (Shutdown Cooling Isolation) automatic isolation. No valves isolated in these systems due to them being in their normally CLOSED position prior to the event. Currently, reactor water level is being maintained by the condensate system in normal level band and reactor pressure is being controlled to limit cool down. The licensee has notified the NRC Resident Inspector.
ENS 444571 September 2008 23:33:00River BendManual ScramNRC Region 4GE-6Voluntary Report of Planned Manual Plant Shutdown. At 1802 on September 1, 2008, River Bend Station (RBS) completed a planned manual shutdown of the unit. This shutdown was determined to be necessary based on the conditions of the grid due to Hurricane Gustav. Evaluation of grid conditions determined that removing the unit from power operation would improve the reliability of the grid and thus the decision was made to shutdown. Offsite power was declared inoperable at 1520 on September 1 based on notification of grid status by the grid operator. It is expected that offsite power will be restored to an operable status within the 24 hour LCO Required Action Completion Time. In addition, damage to turbine building siding was reported. Assessment of this condition is being conducted. RBS had previously activated the Outage Control Center prior to the arrival of Hurricane Gustav. Additional resources are available on site to respond to plant conditions. A comprehensive assessment of the condition of the plant and other site facilities will be completed prior to restart. At this time, a schedule for restart has not been established. The licensee contacted the NRC Resident Inspector.
ENS 4434716 July 2008 09:49:00River BendAutomatic ScramNRC Region 4GE-6On June 2, 2008 at 6:24 a.m. CDT power was lost on the reactor protection system (RPS) bus 'A'. The plant was operating at 100 percent power at the time. The loss of RPS bus 'A' interrupted power to containment isolation actuation circuitry. This caused the Division 1 containment isolation valves in various balance of plant systems to automatically close, as designed. Plant operators implemented recovery procedures to shift RPS 'A' to its alternate power supply, and restore the systems affected by the isolation. The containment isolation valves were confirmed to have actuated as required. Plant capacity was not interrupted by the containment isolation signal. As their primary power source, each RPS bus is supplied by its own motor generator set. The investigation of this event found that two resistors on a circuit card in the voltage regulator on the 'A' RPS motor-generator set failed. This had the effect of causing the generator voltage to fluctuate significantly, resulting in a automatic trip of the generator output breaker and a loss of power on the bus. This event is being reported in accordance with 10CFR50.73(a)(2)(iv)(A) as an invalid actuation of the Division I containment isolation actuation system." The licensee informed the NRC Resident Inspector.
ENS 4408621 March 2008 17:59:00Grand GulfAutomatic ScramNRC Region 4GE-6Actuation of an RPS signal while the reactor was critical. At 1525 a generator trip signal on the main transformers initiated a reactor scram due to Turbine Stop and Control Valve fast closure. Safety relief valves operated initially to lower reactor pressure. Turbine bypass valves operated initially to lower reactor pressure. Turbine bypass valves are maintaining pressure control currently. Reactor recirc pumps A and B transferred to slow speed operation as expected. No ECCS initiations were received. Reactor level is being controlled with normal systems condensate and feedwater. Lowest level indicated was approximately -6" wide range. Level 3 initiations occurred to group 3 isolation valves. No valves operated, they are normally closed. The site is investigating the cause of the trip. A probable cause is the "C" phase differential trip which was received from the main transformer. All control rods fully inserted during the scram. The plant is on its normal shutdown electrical lineup. The licensee notified the NRC Resident Inspector.
ENS 440345 March 2008 17:44:00River BendAutomatic ScramNRC Region 4GE-6At 2:43 p.m. CST, an unplanned automatic reactor scram occurred. The initial investigation determined that the event resulted from an apparent malfunction in the main turbine control system. This had the effect of causing reactor steam pressure to exceed the trip set point for the reactor protection system, initiating the reactor scram signal. All reactor control rods inserted, and the main feedwater system remained in service. Reactor safety-relief valves initially lifted as a result of the pressure transient. Reactor pressure is now being controlled by steam line drains with turbine bypass valves as a backup. There was no condition requiring the actuation of emergency diesel generators or emergency core cooling systems. NRC Resident Inspector has been notified.