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 Entered dateSiteRegionScramReactor typeEvent description
ENS 5229512 October 2016 15:17:00ByronNRC Region 3Manual ScramWestinghouse PWR 4-LoopAt 1338 CDT, a spurious electrical fault on a unit substation motor control center caused a spurious feedwater isolation and required a manual reactor trip on Unit 2 Byron Station due to lowering steam generator level. Auxiliary feedwater automatically actuated to supply feedwater flow and is maintaining steam generator level within procedurally required levels. The motor control center fault resulted in feedwater isolations on two of four steam generators. All rods inserted during the trip. Decay heat is being removed via the steam dumps to condenser. Plant response to the trip was uncomplicated. Unit 2 is in a normal shutdown electrical lineup with power available from offsite. The grid is stable. Byron Station Unit 1 is at 95% power and stable and was unaffected by the transient on Unit 2. The cause of the motor control center fault is under investigation. The licensee has notified the NRC Resident Inspector and will be issuing a press release concerning the manual reactor trip.
ENS 508593 March 2015 14:21:00ByronNRC Region 3Automatic ScramWestinghouse PWR 4-LoopIn accordance with 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A), this notification reports an automatic reactor trip on Byron Unit 1. The trip occurred following a trip of the Byron Unit 1 East Main Power Transformer (MPT). Initial indications appear that the MPT trip was caused by a large (~ 5 foot) section of ice that fell from a bus bar over the 1E MPT. This ice shorted out a MPT bushing, resulting in the unit trip. Reactor operators performed a manual start of the Auxiliary Feedwater System in response to the unit trip. All other safety systems responded as expected. The plant trip occurred at 1101 CST on March 03, 2015. Unit 1 is presently in Mode 3 and stable. Unit 2, the opposite unit, is operating at 100% power and stable. This condition was entered into the Byron CAP Program. An investigation is in progress to determine the extent of required repairs, if any, required prior to unit restart. This event resulted in the actuation of the Reactor Protection System with a subsequent Reactor Trip and therefore, requires notification to the NRC within 4 hours of discovery in accordance with 10 CFR 50.72(b)(2)(iv)(B). This event resulted in the manual actuation of the Auxiliary Feedwater System and therefore, requires notification to the NRC within 8 hours of discovery in accordance with 10 CFR 50.72(b)(3)(iv)(A). This ENS call will be followed up with a Licensee Event Report (LER) within 60 days. All rods inserted during reactor trip, offsite power and emergency power sources are currently available and decay heat is being removed via the startup feedwater systems. No safety relief valves lifted as a result of the transient. The NRC Resident Inspector and the State of Illinois were notified.
ENS 4883820 March 2013 22:41:00ByronNRC Region 3Manual ScramWestinghouse PWR 4-LoopAt 1951 CDT on March 20, 2013, Byron Unit 2 Reactor was manually tripped due to the loss of all Generator Stator Cooling Water. 2BEP-0, 'Reactor Trip or Safety Injection Unit 2' was entered and a transition was made to 2BEPES 0.1, 'Reactor Trip Response Unit 2.' The auxiliary feedwater pumps automatically actuated upon the expected low steam generator level. Upon the trip, it was noted that a Digital Rod Position Indication System Urgent Failure occurred with a General Warning on Control Rod position M12. Indication for the Train 'B' Reactor Trip breaker was lost. All Control Rods inserted upon Reactor trip and the Train 'B' Reactor trip breaker was locally verified open. The plant is in its normal shutdown electrical lineup. No safeties or reliefs lifted during the event. There was no impact on unit-1. The licensee notified the NRC Resident Inspector.
ENS 476446 February 2012 20:40:00ByronNRC Region 3Manual Scram
Automatic Scram
Westinghouse PWR 4-LoopUnit 2 had been connected to the grid at 1431 CST today following a recent forced outage and was in the process of power ascension in accordance with plant procedures. At approximately 25% reactor power (approximately 240 MWe), the operators were transferring main feed flow to the steam generator lower nozzle through the feedwater isolation valves, (i.e. 2FW009A, B, C, D). 2FW009C was the first valve to be opened due to previously experienced problems with this valve being stuck in the seat. No issues were experienced during the opening of 2FW009C. Upon opening of 2FW009C, the 2C steam generator level began to rise as expected. The operators throttled back feedwater flow to control steam generator level. However, the 2C steam generator level increased to the High-High level setpoint of 80.8% (p-14). Since the reactor was below 30% (P-8), no automatic reactor trip signal was generated. However, the turbine automatically tripped, a feedwater isolation signal was initiated, and 2C Main Feedwater pump trip occurred as designed. With no main feedwater flow available, the operators manually tripped the reactor and entry into procedure 2BEP 0, Reactor Trip or Safety Injection Unit 2 was entered. The operators then manually started the 2A and 2B Auxiliary Feedwater pumps to supply water to the steam generators prior to reaching the Low-Low steam generator level setpoint of 36.3%. Transition from 2BEP 0 to 2BEP ES-0.1, Reactor Trip Response, was completed and the emergency procedures were exited. Unit 2 is being maintained in a stable condition in Mode 3. The NRC Resident Inspector has been informed.
ENS 4206319 October 2005 02:39:00ByronNRC Region 3Automatic ScramWestinghouse PWR 4-LoopUnit 2 reactor trip on low 2 S/G level. 2A CD/CB (condensate and condensate booster pump set is driven by a single motor) tripped while 2D CD/CB was out of service. The auto turbine runback was unsuccessful and turbine was runbacked manually. ESF actuations: AF (Auxiliary Feedwater) activation and FWI (Feedwater Isolation)." Only indication on the condensate and condensate booster pump trip was an over current flag. All rods fully inserted into the core. Both the motor driven and the diesel driven auxiliary feedwater pumps are operating. All Emergency Core Cooling systems and the Emergency Diesel Generators are fully operable if needed. The NRC Resident Inspector was paged by the licensee.