Semantic search

Jump to: navigation, search
Search

Edit query Show embed code

The query [[Category:ENS Notification]] [[Site::Oconee]] [[Scram::+]] was answered by the SMWSQLStore3 in 0.3872 seconds.


Results 1 – 10    (Previous 50 | Next 50)   (20 | 50 | 100 | 250 | 500)   (JSON | CSV | RSS | RDF)
 Entered dateSiteRegionScramReactor typeEvent description
ENS 5367720 October 2018 01:13:00OconeeNRC Region 2Automatic Scram
Manual Scram
On 10/19/18 at 2202 EDT, at 19 (percent) Reactor power, a malfunction of (the) Turbine Steam Seal Header pressure control caused a loss of Condenser vacuum, resulting in an automatic trip of the Main Turbine and a manual reactor trip (RPS Actuation). Just prior to the reactor trip, Emergency Feedwater was manually initiated to mitigate the potential loss of Main Feedwater. Condenser vacuum was recovered after the reactor trip and Main Feedwater remained in operation. Due to the RPS actuation while critical, this event is being reported as a 4-hour non-emergency per 10CFR50.72(b)(2). Also, due to the manual initiation of Emergency Feedwater, this event is also being reported as an 8-hour non-emergency per 10CFR50.72(b)(3). Following the reactor trip, all systems responded as expected with no complications. Emergency feedwater was secured at 2300. Unit 1 is in Mode 3 and stable, continuing to cooldown for a refueling outage. The NRC Resident Inspector has been notified.
ENS 5332913 April 2018 06:07:00OconeeNRC Region 2Manual ScramB&W-L-LPOn 4/13/2018 at 0227 (EDT), the Oconee Unit 1 Reactor was manually tripped from 24 percent power due to the inability to control main feedwater flow through the Main Feedwater Control Valves using the Integrated Control System. Due to the RPS actuation while critical, this event is being reported as a 4-hour Non-Emergency per 10 CFR 50.72(b)(2)(iv)(B). Following the reactor trip, multiple Main Steam Relief Valves failed to reseat at the expected pressure. Using procedure guidance, Main Steam Pressure was lowered by 115 psig, resulting in the closing of all Main Steam Relief Valves. All other post-trip conditions are normal and all other systems performed as expected. Unit 1 is currently in Mode 3 and stable. Decay heat is being removed by the steam generators discharging steam to the main condenser using the turbine bypass valves. Units 2 and 3 are not affected by the Unit 1 reactor trip. The licensee notified the NRC Resident Inspector.
ENS 5287024 July 2017 19:25:00OconeeNRC Region 2Automatic ScramB&W-L-LPAt 1638 (EDT) on 7/24/2017, Oconee Unit 3 experienced an automatic reactor trip due to a load rejection when the generator output breakers both tripped open unexpectedly while 525kV switchyard maintenance was being performed. The trip was uncomplicated with all systems responding normally post-trip. Due to the RPS (Reactor Protection System) actuation while critical, this event is being reported as a 4-hour non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). The plant responded normally to the reactor trip, and there was no impact on the health and safety of the public or plant personnel. Operations responded using the Emergency Operating Procedure and stabilized Unit 3 in MODE 3. The NRC Senior Resident Inspector has been notified. Decay heat is removed by discharging steam to the main condenser using the turbine bypass valves. Unit 1 and 2 are not affected.
ENS 5078131 January 2015 18:00:00OconeeNRC Region 2Automatic Scram
Manual Scram
B&W-L-LPAt 1431 EST on 1/31/15, Oconee Unit 3 was manually tripped due to oscillations in the feedwater system in anticipation of an automatic trip. At 1427 EST, Unit 3 began experiencing small feedwater oscillations. Specifically, 3FDW-32, the 3A main feedwater control valve, appeared to be oscillating with corresponding feedwater flow oscillation. Feedwater oscillations continued to grow in magnitude and at 1431 EST a manual trip was directed by the Unit 3 control room supervisor. The shutdown was orderly and the unit is currently stable and in Mode 3 (Hot Standby). Units 1 and 2 were unaffected by the trip and are currently 100% power (Mode 1). Due to the RPS actuation while critical, this event is being reported as a 4-hour non-emergency per 10CFR50.72(b)(2)(iv)(B). Following the reactor trip, a main steam relief valve (MSRV) failed to reseat as expected. Emergency Operating procedure guidance was utilized to reduce main steam system pressure by approximately 80 psig to reseat the valve (valve reseated at 1506 EST). All of the main steam relief valves are now seated. In addition, the 3B condensate booster pump experienced a mechanical seal leak (approximately 4-5 gpm). The pump was subsequently secured at 1447 EST. All other post trip conditions were normal and all other systems performed as expected. Unit 3 is currently in Mode 3 and stable. All rods fully inserted. Main Feedwater is feeding the steam generators and decay heat is being removed to the Main Condenser. The cause of the trip is under investigation. There is no known primary to secondary leakage. The NRC Resident Inspector has been informed.
ENS 4947124 October 2013 09:45:00OconeeNRC Region 2Manual Scram
Automatic Scram
B&W-L-LP

At 0553 EDT on 10/24/2013, Oconee Unit 3 was manually tripped due to oscillations in the feedwater system in anticipation of an automatic reactor trip. At 0549 EDT, Unit 3 began experiencing small feedwater oscillations. The feedwater control system was placed in manual in an attempt to stabilize feedwater flows. Feedwater oscillations continued to grow in magnitude and at 0553 EDT, a manual trip was directed to prevent an automatic reactor trip. Due to an RPS actuation, this event is being reported as a 4 and 8 hour Non-Emergency per 10 CFR 50.72 (b)(2)(iv)(B) and 10 CFR 50.72 (b)(3) Following the reactor trip, four main steam relief valves failed to reseat. Procedure guidance was utilized to reduce main steam system pressure by approximately 30 psig to reseat the main steam relief valves. All main stream relief valves are now reseated. All other post trip conditions were normal and all other systems performed as expected. Unit 3 is currently in Mode 3 and stable. Operations have been stabilized on Unit 3. A post-trip investigation is in progress, per site procedures and directives. The licensee has notified the NRC Resident Inspector.

  • * * UPDATE FROM BOB MEIXELL TO DONALD NORWOOD AT 1439 ON 9/10/14 * * *

Duke Energy reviewed NRC Event Number 49471 against NUREG 1022, Rev 3, section 3.2.6, "System Actuation" and determined this event should have been reported only per 10 CFR 50.72 (b)(2)(iv)(B), RPS Actuation (while critical). Thus, Duke Energy is revising NRC Event Number 49471 to remove the 8-hour report criteria 10 CFR 50.72 (b)(2)(iv)(A). The NRC Resident Inspector was notified of this revised report. This update has no effect on safety significance. Notified R2DO (Shaeffer).

ENS 461597 August 2010 18:47:00OconeeNRC Region 2Manual ScramB&W-L-LPAt 1451 on 8/7/2010, Oconee Unit 1 initiated a manual reactor trip from approximately 17% power due to indicated vibrations on 1A1 and 1A2 reactor coolant pumps (RCP) reaching the high vibration trip criteria. All systems responded normally following the reactor trip. Unit 1 is currently stable in MODE 3. An investigation is in progress to determine the cause of the elevated reactor coolant pump vibrations. All control rods fully inserted on the trip. Decay heat is being removed via the turbine bypass valves to the main condenser. Steam generator water level is being maintained with main feedwater. There is no evidence that the PORVs or safety valves lifted. The plant is in its normal shutdown electrical lineup. There were no indications on the loose parts monitor except for the RCP high vibration. There was no affect on units 2 or 3. The licensee notified the NRC Resident Inspector.
ENS 446387 November 2008 12:05:00OconeeNRC Region 2Automatic ScramB&W-L-LPAt 0834 on 11-7-08, Oconee Nuclear Station (ONS) Unit 3 experienced an automatic reactor trip due to a reactor protective systems (RPS) actuation. ONS Unit 3 post trip parameters are normal. Main Feedwater remained in service following the event and Emergency Feedwater was not required and remained available. Electrical power automatically transferred to the Startup power source from the switchyard and emergency AC power sources were not required and remained available. The cause of the RPS actuation and automatic reactor trip are under investigation. ONS Unit 1 remained at 100% power with no issues following the ONS Unit 3 reactor trip. ONS Unit 2 remained in No-Mode. No other safety systems have actuated or exhibited abnormal behavior. Therefore, the safety significance of this condition is low. All control rods fully inserted during this event. The unit is removing decay heat to the main condenser. No primary relief valves lifted and Main Steam relief valves cycled following the trip. There are no Steam Generator tube leaks. The licensee notified the NRC Resident Inspector.
ENS 4410931 March 2008 17:11:00OconeeNRC Region 2Automatic ScramB&W-L-LP

Event: At 1352 hours, Unit 2 experienced a Reactor Trip due to a turbine trip. The indicated cause was low condenser vacuum. The exact cause is still under investigation but is believed to be related to a maintenance procedure in progress on the condenser vacuum instrumentation. Post-trip response was normal. Auxiliary power transferred to the start-up source (switchyard) as expected. Main Feedwater was not affected so there was no demand for Emergency Feedwater. A second High Pressure Injection pump was manually started per procedure to maintain Pressurizer level indication on scale. This is a routine action to compensate for post-trip RCS temperature and volume changes. In an apparently unrelated event, Keowee Hydro Units (KHU) 1 and 2 were shutdown from commercial operation at approximately 1425 hours. During the shutdown, the KHU 1 output breaker failed to open as expected and KHU 1 was manually locked out. The lockout removed both the Overhead and Underground Power Paths from service, making on-site emergency power unavailable to all three Oconee units. Per Tech Specs, a gas turbine unit at Lee Steam Station was started and used to energize the Oconee Standby Bus at 1518 hours. Initial Safety Significance: There is little or no safety significance to the Unit trip. The subsequent KHU 1 lockout removed both the Overhead and Underground Power Paths from service, making on-site emergency power unavailable until the Lee gas turbine was aligned. There was no demand for the Keowee emergency power function during either event. Corrective Action(s): Investigations are in progress as to the cause of the Reactor Trip and the KHU 1 lock out. Alignment of KHU 2 to the underground is currently on hold, pending evaluation of the problem which led to the KHU 1 lockout. All control rods fully inserted with decay heat being removed via the turbine bypass valves. The licensee notified the NRC Resident Inspector.

  • * * UPDATE AT 1055 EDT ON 04/02/08 FROM COREY GRAY TO HOWIE CROUCH * * *

The licensee is retracting a portion of the original report identified under 10CFR50.72(b)(3)(v)(D) based on the following: Event: UPDATE: At 1352 hours, Unit 2 experienced a Reactor Trip due to a turbine trip. The indicated cause was low condenser vacuum. The exact cause is still under investigation but is believed to be related to a maintenance procedure in progress on the condenser vacuum instrumentation. Post-trip response was normal. Auxiliary power transferred to the start-up source (switchyard) as expected. Main Feedwater was not affected so there was no demand for Emergency Feedwater. A second High Pressure Injection pump was manually started per procedure to maintain Pressurizer level indication on scale. This is a routine action to compensate for post-trip RCS temperature and volume changes. In an unrelated event, Keowee Hydro Units (KHU) 1 and 2 were shutdown from commercial operation at approximately 1425 hours. During the shutdown, the KHU 1 output breaker, ACB-1, failed to open as expected and KHU 1 was manually locked out. The lockout removed KHU 1 and the Overhead Power Path from service due to the failed ACB. Because KHU 1 was the unit aligned to the Underground Power Path, Operations declared that path inoperable also. This condition was initially reported as making on-site emergency power unavailable to all three Oconee units. Per Tech Specs, a gas turbine unit at Lee Steam Station was started and used to energize the Oconee Standby Bus at 1518 hours. In this alignment, the Lee gas turbine provides the on-site emergency power function. A design feature allows a KHU to automatically align to the Underground Path when the unit originally aligned to that path has been locked out, the overhead path is locked out and an emergency start signal exists. Keowee Operations confirmed that during the lockout event the required lockout signals were present on KHU 1 such that KHU 2 would have aligned to the Underground Power Path if an emergency start demand had occurred. As a result, the Underground Power Path remained available during this event and there was no loss of safety function. Therefore the portion of the event related to 10CFR50.72(b)(3)(v)(D) is RETRACTED. The Underground Power Path was administratively inoperable because a surveillance (SR 3.8.1.3) to verify operability of KHU 2 to the underground path, required per TS 3.8.1 Condition C.1, could not be performed. The surveillance procedure utilizes a normal start signal, which was inhibited by the lockout on the overhead path. The surveillance procedure does not include provisions for using an emergency start signal. At 1906 hours, after the overhead lockout had been reset, KHU 2 successfully completed an Operability test aligned to the Underground Power Path. Investigation determined that the failure of ACB-1, the output breaker for KHU 1, was due to a terminal strip sliding link in the trip circuit being in an intermediate position. It was damaged during repair so the entire sliding link block was replaced. The unit was successfully tested connected to each power path and was declared Operable on 4-1-08 at approximately 0600 hours. At 0930 hours on 4-1-08 the standby bus was disconnected from Lee. Initial Safety Significance: There is little or no safety significance to the Unit trip. The subsequent KHU 1 lockout removed the Overhead Power Path from service. The Lee gas turbine was aligned to energize the standby bus. Operations and Engineering subsequently confirmed that on-site emergency power remained available via KHU 2 and the Underground Power Path. There was no demand for the Keowee emergency power function during either event. Corrective Action(s): Investigation as to the cause of the Reactor Trip continues. Unit 2 is now on-line at low power and is in the process of returning to full power. ACB-1, the output breaker for KHU 1, terminal strip sliding link has been repaired/replaced; both KHUs have been tested and declared operable; the Lee gas turbine has been secured. The licensee informed the NRC Resident Inspector. Notified R2DO (Evans).

ENS 4249312 April 2006 14:48:00OconeeNRC Region 2Automatic ScramB&W-L-LPAt 1335 EDT the Unit 2 Reactor tripped from 100% power on a Flux/Flow/Imbalance on two (2) RPS Channels "A" and "D." The initiating event was the trip of the "2B2" Reactor Coolant Pump (RCP) for unknown reasons. I & E Techs were working in the RCP Monitoring Cabinets at the time. Immediately following the RCP trip, Unit 2 commenced a runback as expected for approximately six (6) seconds before the RPS actuation occurred. All rods fully inserted with an anomaly noted for CRD (Control Rod Drive) Group 3 Rod 7 API (Absolute Position Indication) indicating approximately 21%, however, the PI (Position Indicating) Panel light was on. The licensee suspects that the problem is related to a reed switch for the API indication and not the actual rod position. Shutdown Margin has confirmed that the Reactor is subcritical. The Pressurizer Code Safeties and PORV did not lift during the transient. Unit 2 is currently stable in Mode 3 discharging steam to the Main Condenser via the Turbine Bypass Valves using Main Feedwater for steam generator level control. Offsite power is available and stable. This event did not impact Units 1 or 3. RCP "2B2" will remain secured until the cause of the trip is identified and corrected. There is no known primary to secondary leakage for Unit 2. The licensee has completed EOP (Emergency Operating Procedure) subsequent actions. The licensee informed the NRC Resident Inspector.
ENS 4196631 August 2005 17:38:00OconeeNRC Region 2Automatic ScramB&W-L-LP

Event: At 1428 hours on 8/31/2005, Oconee Unit 3 tripped. A routine test of the alternate power source for the Control Rod Drive System was in progress when power to the Control Rod Drive system was interrupted, which resulted in a reactor trip. AC power transferred to the Start-up source (switchyard). Normally the Main Steam Header pressure control setpoint is automatically increased for post-trip RCS temperature control. This did not occur. As a result the RCS cooled down to approximately 536F (versus a normal post-trip temperature of approximately 555F), reducing RCS pressure to the actuation setpoint for Engineered Safeguards Channels 1 and 2. This started the High Pressure Injection pumps in ECCS mode, caused partial containment isolation and initiated start-up of both Keowee Hydro Units (emergency power). Because Start-up power was available, Keowee did not supply power but remained in stand-by. At 1133 hours Operators terminated ECCS injection. Initial Safety Significance: Because RCS pressure decreased below normal post-trip levels which resulted in an ECCS actuation, this is considered an abnormal transient. Unit 3 has been stabilized and at this time the actual event is considered to have low safety significance. The exact cause of the loss of power to the Control Rod Drive system is unknown, but is under investigation. It is suspected that that loss also resulted in the failure of the Main Steam Header Pressure to shift to the post-trip Main Steam pressure control setpoint. Corrective Action(s): Operations stabilized Unit 3. A post-trip investigation is in progress, per site procedures and directives. All control rods fully inserted as a result of the reactor trip. No primary or secondary reliefs or PORVs lifted. Pressurizer level decreased off-scale low and was recovered prior to securing the High Pressure Injection pumps (the licensee estimates approximately 3000 gallons was injected). Current RCS temp is 542F (Tave) with RCS pressure in the normal post-trip band. Decay heat is being removed by the Steam Generators to Condenser through the Turbine Bypass Valves. Main Feedwater remained in service during the transient. The licensee informed the NRC Resident Inspector and does not plan a press release at this time.

  • * *UPDATE FROM LICENSEE (NIX) TO NRC (HUFFMAN) @ 2156 EDT ON 8/31/05 * * *

During this event, the Engineering Safeguards (ES) System was manually bypassed at 14:33 on 8-31-05 to restore both High Pressure Injection (HPI) System trains to a normal lineup following an ES-initiated safety injection. Manually bypassing ES for both trains of HPI required entry into Tech Spec 3.0.3 at 15:33 on 8-31-05. Tech Spec 3.0.3 requires shutdown of Unit 3 to Mode 3 by 03:33 on 9-1-05 and to Mode 4 by 09:33 on 9-1-05. This condition was discovered to apply at 21:15 on 8-31-05. Initial Safety Significance: Units 1 and 2 remain at 100% power with no issues following the Unit 3 ES Actuation and Keowee Hydro Unit emergency start. Unit 3 remains in Mode 3. No other safety systems have actuated or exhibited abnormal behavior. Therefore, the safety significance of this condition is LOW. Corrective Action(s): Restore ES System to Automatic for the HPI System. The licensee reported this under 10 CFR 50.72(b)(2) (i), Technical Specification Shutdown. The licensee will notify the NRC Resident Inspector. R2DO (Lesser) notified.