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The query [[Category:ENS Notification]] [[Site::Arkansas Nuclear]] [[Scram::+]] was answered by the SMWSQLStore3 in 0.4449 seconds.


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 Entered dateSiteRegionScramReactor typeEvent description
ENS 5409126 May 2019 09:25:00Arkansas NuclearNRC Region 4Automatic ScramThis is a 4-hour Non-Emergency 10 CFR 50.72(b)(2)(iv)(B) notification due to a Plant Protection System (PPS) actuation. Arkansas Nuclear One, Unit 2, automatically tripped from 100 percent power at 0512 CDT. The reactor automatically tripped due to 2P-32B Reactor Coolant Pump tripping as a result of grounding. No additional equipment issues were noted. All control rods fully inserted. Emergency Feedwater (EFW) actuated and was utilized to maintain Steam Generator (SG) levels. The EFW actuation meets the 8-hour Non-Emergency Immediate Notification Criteria of 10 CFR 50.72(b)(3)(iv)(A). No Primary safety valves lifted. Main Steam Safety Valves (MSSVs) did lift initially after the trip. The NRC Resident Inspector has been notified. Decay heat is being removed via the steam dump valves to the main condenser. Unit 2 is in a normal shutdown electrical lineup. Unit 1 was not affected by the transient on Unit 2. The licensee notified the State of Arkansas."
ENS 5379318 December 2018 15:40:00Arkansas NuclearNRC Region 4Automatic ScramOn December 18, 2018 at 1126 CST, Arkansas Nuclear One, Unit 1 (ANO-1) reactor automatically tripped due to a loss of the A-1, non-vital 4160V bus. All control rods fully inserted. Loss of the A-1 bus resulted in de-energizing A-3 vital 4160V bus. Emergency Diesel Generator #1, K-4A, started automatically and is currently powering A-3 vital bus. Non-vital buses A-2, H-1, and H-2 and vital bus A-4 transferred power automatically to the Startup Transformer #1. Off-site power remains energized and available for ANO-1. The reason for loss of A-1 bus is unknown at this time. Currently, ANO-1 has stabilized in Mode 3, Hot Standby. Decay heat is being removed by the main condenser using the turbine bypass valves. The loss of the A-1, non-vital bus, is under investigation. The licensee has notified the NRC Resident Inspector and the state.
ENS 5345916 June 2018 15:56:00Arkansas NuclearNRC Region 4Manual ScramAt 1121 CDT on June 16, 2018, Arkansas Nuclear One, Unit 1 (ANO-1) performed a manual reactor trip due to a Turbine Bypass valve failing open on reactor startup. At the time, ANO-1 was in Mode 2 at approximately 2 percent power. The failed Turbine Bypass valve resulted in an overcooling event and the Overcooling Emergency Operating Procedure (EOP) was entered. Main Steam Line Isolation (MSLI) automatic actuation occurred on 2 of the 4 channels of Emergency Feedwater Initiation and Control during the overcooling event in the 'B' Steam Generator. The remaining channels of MSLI were manually actuated by the control room staff from the control room. Overcooling was terminated after the closure of the Main Steam Isolation Valve (MSIV) and reactor coolant parameters were stabilized as directed by the Overcooling EOP. Additionally, Gland Sealing Steam was lost to the main turbine due to the closure of the 'B' Steam Generator MSIV and Loss of Condenser Vacuum Abnormal Operating Procedure was entered. This is a 4-hour non-emergency 10 CFR 50.72 (b)(2)(iv)(B) notification due to a Reactor Protection System actuation (scram) and an 8-hour non-emergency 10 CFR 50.72 (b)(3)(iv)(A) notification for safety system actuation." All control rods fully inserted into the core during the trip. Heat removal is via the Atmospheric Dump Control valves to atmosphere. The NRC Resident Inspector has been notified. The licensee also notified the State of Arkansas.
ENS 5271026 April 2017 14:49:00Arkansas NuclearNRC Region 4Automatic ScramB&W-L-LP
CE
At 1004 CDT, Arkansas Nuclear One, Unit 1 (ANO-1) reactor automatically tripped due to the partial loss of offsite power. At the time of the trip, the site was in a Tornado Warning and a Severe Thunderstorm Warning. The Emergency Feedwater (EFW) system auto-actuated due to the loss of main feedwater pumps and the loss of the Reactor Coolant pumps. Both Emergency Diesel Generators started as expected with only one loading as expected. All control rods fully inserted. Currently, ANO-1 has stabilized in Hot Standby via natural circulation. ANO-1 also lost Spent Fuel Pool cooling for approximately 69 minutes. The temperature of the spent fuel pool at the beginning of the event was approximately 102 (degrees) F. The spent fuel pool saw a heatup of 1 (degree) F during the loss of spent fuel pool cooling. The Spent Fuel Pool cooling has been restored. ANO-2 is currently in a refueling outage with all fuel in the spent fuel pool. ANO-2 completed a full core off load to the spent fuel pool and this was completed on April 12, 2017. Spent Fuel Pool cooling was lost for approximately 10 minutes. The Spent Fuel Pool temperature was 91 (degrees) F prior to the event. No heat up of the pool was identified during the event. Cooling has subsequently been restored. The #1 Emergency Diesel Generator auto-started as designed but did not supply the safety bus due to availability of offsite power. No radiological releases have occurred from either unit due to this event. The licensee has notified the NRC Resident Inspector.
ENS 5160715 December 2015 10:24:00Arkansas NuclearNRC Region 4Manual ScramB&W-L-LPThis is a 4-hour Non-Emergency 10 CFR 50.72(b)(2)(iv)(B) notification due to a Reactor Protection System (RPS) actuation. Arkansas Nuclear One, Unit 1, was manually tripped from 43 percent power at 0544 CST. The reactor was manually tripped due to operator judgement during control issues with the Integrated Control System (ICS) during a planned downpower for Electro-Hydraulic Control (EHC) system maintenance. CV-2672 B, low load control valve, failed to close. Subsequently, CV-2674 B, low load block valve, began to close and caused a loss of feed to E-24B Steam Generator. No additional equipment issues were noted. All control rods fully inserted. Emergency Feedwater (EFW) actuated and was utilized to maintain Steam Generator (SG) levels. This (EFW actuation) meets the 8 hour Non-Emergency Immediate Notification Criteria ((10CFR50.72(b)(3)(iv)(A)). No Primary safety valves lifted. Main Steam Safety Valves (MSSVs) did lift initially after the trip. The NRC Resident (Inspector) has been notified. Decay heat is being removed via the steam dump valves to the main condenser. Unit 1 is in a normal shutdown electrical lineup. Unit 2 was not affected by the transient on Unit 1. The licensee notified the State of Arkansas.
ENS 5006327 April 2014 23:57:00Arkansas NuclearNRC Region 4Automatic ScramCEAt approximately 1932 (CDT) on 4/27/2014, the System Operations Center (SOC - Dispatcher) informed Unit 2 of a system wide grid emergency and ordered both Unit 1 and Unit 2 to come off line as soon as possible. At approximately 2012 (CDT), Unit 2 automatically tripped from 51% power due to an Auxiliary Trip on CPCs (Core Protection Calculator) due to Axial Shape Index (ASI) trip. All Control Element Assemblies inserted into the core. Both vital and non-vital 4160V and 6900V buses remain powered from Startup #3 Transformer. All Systems responded as designed. At 1932 (CDT), Unit 1 commenced a Rapid Plant Shutdown at a rate 5-7% per min with the intention to take the turbine offline and leave the reactor critical at 10-12% power on the Turbine Bypass Valves. When the Unit 2 reactor tripped, Unit 1 stopped the power reduction and stabilized the plant at approximately 19% Reactor Power and 125 Generated Megawatts. With SOC concurrence, Unit 1 stabilized power and was told to limit site output to <200 MWe. At 1932 CDT, Unit 1 began a down power from 100% power and Unit 2 began a down power from 95% power. On Unit 2, decay heat is being removed by the main condenser using the turbine bypass valves. Unit 2 is stable in Mode 3 with stable offsite power. The system wide grid emergency is believed to be caused by tornados in the region. The licensee has notified the NRC Resident Inspector and the State.
ENS 481698 August 2012 13:15:00Arkansas NuclearNRC Region 4Automatic ScramCEAt 0823 hours on August 8, 2012, Arkansas Nuclear One, Unit 2 (ANO-2) experienced an automatic reactor trip. The reactor automatically tripped due to High Reactor Coolant System Pressurizer Pressure that was caused by a Main Turbine trip due to high condenser back pressure from a degraded vacuum condition. The Reactor Protection System (RPS) performed as designed in response to the High Reactor Coolant System Pressurizer Pressure condition resulting in automatic shutdown of the reactor from approximately 100 percent power. All Control Element Assemblies (CEAs) fully inserted on the trip. The Emergency Feedwater Actuation System (EFAS) actuated for the 'A' Steam Generator only due to level trending slightly below the setpoint. The plant has transitioned to supplying the steam generators using the Auxiliary Feedwater (AFW) system. The unit is currently in Mode 3 and implementing the transient response process. The investigation into the cause of the trip is ongoing and the local NRC Resident Inspectors have been notified. The unit is in a normal electrical lineup, and the decay heat is being removed by the main condenser via the turbine bypass valves. The State Department of Health was notified and ANO-2 will be issuing a press release.
ENS 4587226 April 2010 01:35:00Arkansas NuclearNRC Region 4Automatic ScramB&W-L-LPThis is a 4 hour Non-Emergency 10CFR 50.72(b)(2)(iv)(B) notification due to an Automatic Reactor Protection System (RPS) actuation (scram). At 2126 hours (CDT) on April 25, 2010, Unit 1 Reactor automatically tripped due to 2 of 4 Reactor Protection System (RPS) Channels tripped. At the time of the trip, reactor power, as indicated by heat balance, was ~20%, while excore Nuclear Instrumentation (NI) indicated ~30%. The RPS high reactor power trip setpoint was 50% power. An NI calibration initiated an automatic withdrawal command to the control rod drive system. The rod withdrawal, resulted in one RPS channel tripping on high reactor power and another RPS channel tripping on high reactor coolant system pressure. All control rods fully inserted into the core and no safety systems, other than RPS, actuated. Emergency feedwater did not actuate and was not needed. No primary safety valves lifted. Seven secondary safety valves lifted and subsequently reseated. The plant is currently stable in Mode 3. The NRC resident has been notified. The licensee also informed the State of Arkansas and does not plan a press release. The Unit 1 reactor trip was uncomplicated. Current means of decay heat removal is normal feedwater to the Steam Generators with steam discharge to the Main Condenser through Main Steam Bypass. The Main Generator was online at the time of the trip and the plant is currently in a normal post trip electrical line up. There is no indication of primary-secondary tube leakage. All systems functioned as required.
ENS 4585418 April 2010 18:04:00Arkansas NuclearNRC Region 4Manual ScramB&W-L-LPThis is a 4-hour Non-Emergency, 10CFR 50.72(b)(2)(iv)(B) notification due to an RPS actuation (scram). Arkansas Nuclear One Unit 1 was manually tripped from 11% power at 1357 hrs. CDT. The cause of the trip was operator judgment due to a small fire reported in the high pressure turbine enclosure at governor valve number 3 by a fire watch stationed at that location and an unrelated failure of P-32C Reactor Coolant Pump 3rd stage seal (upper seal) occurring earlier that afternoon. No additional equipment issues were noted. An extinguishing agent (CO2) was applied within approximately 30 seconds. All control rods fully inserted. No primary safeties lifted. No secondary safeties lifted. Emergency feedwater did not actuate and was not needed. No safety systems actuated. The plant will be cooled down to repair the P-32C Reactor Coolant Pump Seal. The NRC Resident has been notified. There was no effect on Unit 2. The grid is stable with Unit 1 in a normal shutdown electrical lineup. Decay heat is being removed via the steam dumps to condenser using normal feed to the steam generators. The licensee will be notifying the Arkansas Department of Health.
ENS 455498 December 2009 12:19:00Arkansas NuclearNRC Region 4Manual ScramCEArkansas Nuclear One - Unit 2 experienced a high temperature on the 'A' Main Feedwater Pump thrust bearing which required the pump to be manually tripped . Steam Generator levels lowered as a result of the Main Feedwater Pump trip to the point that operators initiated a manual reactor trip. The Emergency Feedwater System automatically actuated on low Steam Generator level as a result of the Steam Generator level transient. The manual reactor trip requires 4-Hr non-emergency notification IAW 10CFR 50.72(b)(2)(iv)(B). The automatic actuation of Emergency Feedwater requires 8-Hr non-emergency notification IAW 10CFR 50.72(b)(3)(iv)(A). All rods fully inserted. After the trip, decay heat was being removed using steam dumps to the condenser. Steam generator level was being maintained with the emergency feedwater pumps. The licensee will notify the NRC Resident Inspector.
ENS 4490614 March 2009 02:03:00Arkansas NuclearNRC Region 4Automatic Scram
Manual Scram
CEAt 2151 CDT on 3/13/2009 with plant power at 84% following securing of the 2P-1A Main Feedwater Pump at 1934 due to bearing degradation, Unit 2 experienced a failure of the 'B' Main Feedwater Regulating Valve 2CV-0740 which caused 2E-24B Steam Generator level to lower. At 2151, with 2E-24B Steam Generator level at approximately 25% control room staff manually tripped the reactor anticipating an automatic trip at 22% steam generator level. Emergency Feedwater Actuation System automatically actuated at 22% steam generator level and responded to restore level to the normal post-trip levels. All Control Element Assemblies (rods) Inserted on the reactor trip. No safeties or relief valves opened after the trip. The plant is in its normal shutdown electrical line-up. Steam generator level is being maintained with emergency feedwater and decay heat is being dumped to the main condenser. The licensee notified the State of Arkansas and the NRC Resident Inspector.
ENS 448377 February 2009 12:18:00Arkansas NuclearNRC Region 4Manual ScramB&W-L-LP

Arkansas Nuclear One Unit 1 declared an Unusual Event per EAL 7.5 at 1059 CST based on a fire onsite. The fire occurred on the 354 foot elevation iso-phase bus deck of the turbine building. The fire was attributed to a failed bonnet on a manual valve which had unthreaded during operation releasing hydrogen in the vicinity of the hydrogen add station. The licensee extinguished the fire using water and posted a reflash watch. There were no reported personnel injuries. Offsite assistance was requested from the London Fire Department which arrived onsite after the fire had been extinguished. The reactor was manually tripped with all control rods fully inserting. The plant is currently stable with decay heat removal via the steam dumps to the main condenser. The licensee informed state/local agencies and the NRC Resident Inspector.

  • * * UPDATE AT 1338 EST ON 2/7/09 FROM JACKSON TO SANDIN * * *

The Unusual Event was terminated at 1338 CST after confirmation that the fire was extinguished and a review of the exit criteria as defined in plant procedures. The licensee is performing a damage assessment at this time. The licensee was in the process of informing state/local agencies and will inform the NRC Resident Inspector. Notified R4DO (Clark), NRR(Hiland), IRD (Grant), DHS (Banner) and FEMA (Canupp).

  • * * UPDATE AT 1508 EST ON 2/10/09 FROM SCHEIDE TO HUFFMAN * * *

The subject event notification erroneously reported that all control rods fully inserted following the manual reactor trip initiated in response to a fire on site. In actuality, the rod bottom light for Rod 6 in Rod Group 7 on the CRD Position Indication Panel did not illuminate following the reactor trip and it was verified by plant computer to have inserted to 2.3 percent withdrawn. The control board operator identified this condition quickly and reported it to the Control Room Supervisor in his immediate action response. This condition did not necessitate any additional operator actions and shutdown margin requirements were maintained. The licensee has informed the NRC Resident Inspector. R4DO (Miller) notified.

ENS 448315 February 2009 19:20:00Arkansas NuclearNRC Region 4Manual ScramB&W-L-LPArkansas Nuclear One Unit 1 was manually tripped from 61% power due to Control Rod Drive motor (CRD) high temperatures due to a loss of cooling water flow from Non-Nuclear Intermediate Cooling Water (ICW). No significant equipment issues were observed. No primary safeties lifted. Secondary safeties lifted for ~18 seconds. Emergency feedwater did not actuate and was not needed. Post trip response was normal and the plant is stable in mode 3. Post transient review is in progress. All control rods fully inserted into the core. There is no known primary-secondary steam generator tube leakage. The offsite electrical grid is stable. The loss of ICW flow is attributed to the mechanical failure of service air compressor C-3A. Decay heat removal is via main feedwater to the steam generator and steam to the main condenser. The licensee informed state, other government agencies and the NRC Resident Inspector and will inform local government agencies. No press release is planned.
ENS 4477514 January 2009 16:46:00Arkansas NuclearNRC Region 4Manual ScramCEUnit 2 performed a controlled shutdown from 60% power to make repairs to a low pressure feedwater heater. The unit was taken off line at 1148 today. The unit is stable in Mode 3, Hot Standby. A press release was made at 1430 today. The licensee notified the NRC Resident Inspector.
ENS 4473620 December 2008 14:23:00Arkansas NuclearNRC Region 4Manual ScramB&W-L-LPArkansas Nuclear one Unit 1 manually tripped from 100% power due to control rod mechanism group 7 unexpectedly dropping from 90% to 70%. No Primary safeties lifted. Secondary safeties lifted for approximately 1 minute. Emergency feedwater did not actuate and was not needed. Post trip response was normal and the plant is stable in mode 3. Post transient review is in progress. All control rods fully inserted on the trip. The plant is in its normal shutdown electrical lineup. Steam generator level is being maintained using aux feed and steam is being dumped to the main condenser through the turbine bypass valves. There is no primary to secondary leakage. The licensee notified the NRC Resident Inspector, the State of Arkansas, and the Arkansas Department of Health. See similar event number 44716.
ENS 4471612 December 2008 11:48:00Arkansas NuclearNRC Region 4Manual ScramB&W-L-LPFollowing startup from refueling outage 1R21, Arkansas Nuclear One Unit 1 was holding stable at 32% reactor power in order to perform Nuclear Instrumentation (NI) calibration. Control Rod Drive Mechanism (CRDM) control was in automatic with the controlling group (Group 7) at approximately 75% withdrawn. Control room operators received an asymmetric rod alarm and noted abnormal rod pattern on Group 7 with reactor power lowering. At this point, operations manually scrammed the reactor. Post trip response was normal and the plant is stable in Mode 3. Reactor Coolant System pressure is approximately 2155 psig and temperature is approximately 550 degree F. Post Transient Review is in progress. Unit 1 is in a normal post trip electrical lineup. No primary or secondary reliefs lifted during the transient. Auxiliary feedwater was placed in service to supply the Steam Generators for decay heat removal via the Main Condenser. The licensee informed both the State and NRC Resident Inspector.
ENS 4312125 January 2007 20:11:00Arkansas NuclearNRC Region 4Manual ScramCENotification of shutdown required by the Technical Specifications per 10CFR50.72(b)(2)(i). Arkansas Nuclear One Unit 2 is shut down in Mode 3 (Hot Standby) due to Control Element Assembly misalignment as required by Technical Specification 3.1.3.1.d (All CEAs shall be OPERABLE with each CEA of a given group positioned within 7 inches, indicated position, of all other CEAs in its group). CEA #35 dropped to the bottom of the core due to power supply breaker trip during maintenance and was unable to be recovered within the allowed time. All rods were verified to trip normally as part of the controlled shutdown." The reactor was manually tripped from approx. 20% power. The reactor trip was preplanned. The NRC Resident Inspector and the county were notified of this event by the licensee. Licensee will also notify the State of this event.
ENS 4222926 December 2005 15:35:00Arkansas NuclearNRC Region 4Automatic ScramB&W-L-LPA reactor trip occurred due to a Reactor Protective System (RPS) actuation from probable Main Turbine problems. The Emergency Feedwater Initiation and Control System (EFIC) actuated on the 'A' Steam Generator only due to a momentary level spike post trip. The RPS and EFIC performed as designed. Unit 1 will remain in mode 3 for troubleshooting efforts. No significant equipment issues observed. This report is being made in compliance with the 4 hour and 8 hour non-emergency notifications required by 10CFR50.72(b)(2)(iv)(B) and 10CFR50.72(b)(3)(iv)(A), respectively. The licensee notified the NRC Resident Inspector and State authorities. All rods fully inserted. The trip was characterized as uncomplicated and all systems functioned as required. Electrical conditions are stable. The reactor is currently at no load temperature and pressure with decay heat being removed via the turbine bypass valves and cooling to the steam generators from the non-safety related auxiliary feedwater system. The trip had no impact on Unit 2. The licensee was in no significant LCO at the time of the trip. The licensee noted that one of the main steam code safeties did stick open for a short period of time but closed after secondary pressure was reduced without any overcooling. The cause of the turbine trip is under investigation.
ENS 4011929 August 2003 21:59:00Arkansas NuclearNRC Region 4Automatic ScramB&W-L-LP

Unit 1 experienced an automatic reactor trip at approximately 14:28 CDT as a result of a turbine trip. Initial indications are that the trip was associated with a lightning strike on site. Plant is stable in Mode 3. All control rods fully inserted and there are no offsite radiation releases. Anomalies noted are 'C' Main Phase Transformer Sudden Pressure Trip Alarm, Main Generator Output Breakers failed to automatically open and were subsequently manually opened, and 'B' Once Through Steam Generator (OTSG) main feedwater block valve failed to indicate closed which resulted in a low level condition on 'B' OTSG and subsequent automatic actuation of Emergency Feedwater (EFW). EFW is controlling both OTSG levels at low level limits. A normal fast transfer to the Startup Transformer occurred following the trip and offsite power remains available. All EDGs are in standby, if needed. There is no safety related equipment out of service at this time. Decay heat is currently being removed via the steam dumps to the main condenser. The licensee will conduct an investigation into the equipment failures and determine if any plant equipment was damaged by the lightning strike. The licensee informed the NRC Resident Inspector.

  • * * UPDATE AT 0144 EDT FROM HOGUE TO CROUCH * * *

This message is intended to provide clarifying information for Event Notification #40119. Unit 1 experienced an automatic reactor trip at approximately 14:28 CDT as a result of a turbine trip. Initial indications are that the trip was associated with a lightning strike on site. Plant is stable in Mode 3. All control rods fully inserted and there are no offsite radiation releases. The following anomalies were noted in conjunction with plant trip. A 'C' Main Phase Transformer Sudden Pressure Trip Alarm occurred as a result of an indication problem only. The Main Generator Output Breakers failed to automatically open and were subsequently manually opened. The 'B' Once Through Steam Generator (OTSG) main feedwater (MFW) block valve failed to fully close. Complications associated with manual control of feedwater flow when the MFW block valve failed to fully close resulted in a momentary low level in the 'B' OTSG and Emergency Feedwater (EFW) automatic actuation. EFW flow quickly restored the 'B' OTSG level to normal. Both MFW pumps remained operating throughout the transient, and MFW flow was never lost. The EFW System was allowed to recirc for approximately 2 hours. After the MFW block valve was manually closed, the auxiliary feedwater pump was placed in service and EFW and the MFW pumps were secured. The licensee will be notifying the NRC Resident Inspector.

  • * * UPDATE 2017 EDT ON 8/30/03 FROM RICHARD SCHEIDE TO S. SANDIN * * *

The following information was provided as an update: This message is intended to update the information provided in previous notifications concerning Event Notification #40119. Based on subsequent investigation the automatic reactor trip which occurred at approximately 14:28 CDT on August 29, 2003, was a result of high reactor coolant system (RCS) pressure. The high RCS pressure resulted from the inadvertent closure of the main turbine governor valves. Although not conclusively determined, the closure of these valves is most likely due to a lightning strike on site. This automatic reactor trip also resulted in a main turbine trip. Anomalies associated with this event remain as previously reported. The primary PORV (2450 psia) and Safeties (2500 psia) did not lift during the pressure excursion. The High RCS Pressure setpoint for RPS actuation is 2355 psia. The licensee informed the NRC Resident Inspector. Notified R4DO(Runyan).