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Category:Licensee Event Report (LER)
MONTHYEAR05000237/LER-2023-001, HPCI Inoperable Due to Air Void Accumulation2024-01-19019 January 2024
HPCI Inoperable Due to Air Void Accumulation
05000237/LER-2022-001-01, Reactor Scram Due to Turbine Trip on High Reactor Water Level Caused by Feedwater Regulating Valve Failure2022-10-28028 October 2022
Reactor Scram Due to Turbine Trip on High Reactor Water Level Caused by Feedwater Regulating Valve Failure
05000237/LER-2022-002-01, Ultimate Heat Sink Declared Inoperable Due to River Grass Accumulation2022-10-28028 October 2022
Ultimate Heat Sink Declared Inoperable Due to River Grass Accumulation
05000237/LER-2022-002, Ultimate Heat Sink Declared Inoperable Due to River Grass Accumulation2022-09-27027 September 2022
Ultimate Heat Sink Declared Inoperable Due to River Grass Accumulation
05000237/LER-2022-001, Reactor Scram Due to Turbine Trip on High Reactor Water Level Caused by Feedwater Regulating Valve Failure2022-09-0909 September 2022
Reactor Scram Due to Turbine Trip on High Reactor Water Level Caused by Feedwater Regulating Valve Failure
05000249/LER-2021-001-01, Reactor Scram Due to Main Power Transformer Failure2022-06-14014 June 2022
Reactor Scram Due to Main Power Transformer Failure
ML20135G7442020-05-14014 May 2020
Final ASP Analysis - Dresden 2 (LER 237-90-006)
05000249/LER-2017-0012017-12-27027 December 2017
Unit 3 Standby Liquid Control System Inoperable Due to a Manufacturing Defect Causing a Piping Leak, LER 17-001-01 for Dresden Nuclear Power Station, Unit 3 Regarding Unit 3 Standby Liquid Control System Inoperable Due to a Manufacturing Defect Causing a Piping Leak
ML17252B5052017-11-0303 November 2017
LER 77-050/03L-0 for Dresden, Unit 2 Re Local Leak Rate Test of Drywell Personnel Air Lock During Refueling
ML17252A3262017-10-21021 October 2017
LER 77-040/03L-0 for Dresden 3 Regarding the Circuit Breaker for Service Water Makeup Valve MO-3-4102 to the Isolation Condenser Found in Off Position
ML17252B4922017-08-28028 August 2017
LER 78-028/01X-1 for Dresden, Units 2 and 3 Re NRC Request for Immediate Actions to Be Taken to Mitigate the Potential for a Spurious Closure of a Recirculation Loop Suction Valve with a LOCA Occurring Between the Loop Discharge and Suction
05000237/LER-2016-0032017-05-26026 May 2017
Control Room Emergency Ventilation System Charcoal Filter Bank Failure to meet the Methyl Iodide Penetration Acceptance Criteria, Dresden Nuclear Power Station, Units 2 and 3, Cancellation of Licensee Event Report 237/2016-003-00, Control Room Emergency Ventilation System Charcoal Filter Bank Failure to meet the Methyl Iodide Penetration Acceptance Criteria
ML17153A0342017-05-26026 May 2017
Cancellation of Licensee Event Report 237/2016-003-00, Control Room Emergency Ventilation System Charcoal Filter Bank Failure to Meet the Methyl Iodide Penetration Acceptance Criteria
05000237/LER-2016-0042017-01-0909 January 2017
Reactor Building Differential Pressure Less than Technical Specification Requirement, LER 16-004-00 for Dresden Nuclear Power Station, Unit 2, Regarding Reactor Building Differential Pressure Less than Technical Specification Requirement
05000249/LER-2016-0012016-08-25025 August 2016
Alert Declared from Unit 3 HPCI Auxiliary Oil Pump Motor Fire, LER 16-001-00 for Dresden Nuclear Power Station Regarding Alert Declared from Unit 3 HPCI Auxiliary Oil Pump Motor Fire
05000237/LER-2016-0022016-07-15015 July 2016
Unit 2 HPCI Inlet Steam Drain Pot Piping Leak Resulting in HPCI Inoperability, LER 16-002-00 for Dresden Nuclear Power Station, Unit 2 Regarding HPCI Inlet Steam Drain Pot Piping Leak Resulting in HPCI Inoperability
05000237/LER-2016-0012016-04-0808 April 2016
Secondary Containment Differential Pressure Transient, LER 16-001-00 for Dresden Nuclear Power Station, Unit 2 and 3 Regarding Secondary Containment Differential Pressure Transient
05000249/LER-2015-0012016-01-22022 January 2016
Main Steam Line Flow Switches Found Outside Tech Spec Allowed Value, LER 15-001-01, Dresden, Unit 3 Main Steam Line Flow Switched Found Outside Tech Spec Allowed Value
ML1015505692009-07-24024 July 2009
Letter LS-AA-1 25-1001, Elevated Tritium Values Identified in 2 Storm Drains Due to Through-Wall Leaks in Underground Piping for Dresden Units 2 and 3.
ML0602404072004-05-0505 May 2004
Final Precursor Analysis - Dresden Unit 3 - Unit 3 Scram Due to Loss of Offsite Power and Subsequent Inoperability of the Standby Gas Treatment System for Units 2 and 3
ML0234501722002-12-0202 December 2002
LER 89-029-05, Dresden Unit 2, Elevated HPCI Discharge Piping Temperature Due to Reactor Feedwater System Back Leakage
ML17252B5391981-06-10010 June 1981
LER 81-034/03L-0 for Dresden, Unit 2 Re J-3 CRD Was Tested for Overtravel. the Overtravel Alarm Came Up and Rod Position Indication Was Lost
ML17252B5411981-06-0808 June 1981
LER 81-030/01T-0 for Dresden, Unit 2 Re Operator Noticed the HPCI Steam Line Was Cold and Filled with Water. the HPCI System Was Declared Inoperable
ML17252B5401981-06-0505 June 1981
LER 81-024/03L-0 for Dresden, Unit 2 Re While Conducting Routine Review of Surveillance, It Was Found That the Monthly Surveillance Required by Tech. Spec. 4.4.c.1 for Standby Liquid Control Tank Sampling Was Three Days Overdue
ML17252B5271981-06-0303 June 1981
LER 81-023/03L-0 for Dresden, Unit 2 Re While Running HPCI Pump Test, the Operator Observed Torus Wide Range Level Instrument Reading 0 Inches and Narrow Range Level Instrument Reading, About - 2 Inches and Oscillating
ML17252B5281981-04-14014 April 1981
LER 81-015/03L-0 for Dresden, Unit 2 Re the Fire Marshall Discovered That the Heat Detectors Were Not Functionally Tested within the 6 Month Interval Required by Tech. Spec. 4.12.A.1
ML17252B5291981-03-23023 March 1981
LER 81-011-03L-0 for Dresden, Unit 2 Re Observed Inadequacies in the Implementation of Administrative or Procedural Controls Which Threaten to Cause Reduction of Degree of Redundancy Provided in Reactor Protection Systems or Engineered Safe
ML17252B5301981-02-20020 February 1981
LER 81-080/031-0 for Dresden, Unit 2 Re Abnormal Degradation of Systems Other than Those Specified in Item B.1.e Above Designed to Contain Radioactive Material Resulting from the Fission Process
ML17252B5321981-02-17017 February 1981
LER 81-070/03L for Dresden, Unit 2 Re While Conducting Steam Line Area Temperature Switch Calibration Surveillance, Temperature Switch TS 2-261-180 Failed to Trip
ML17252B5331981-02-0202 February 1981
LER 81-020/03L-0 for Dresden, Unit 2 Re During Refueling Outage LPCI Test Spray Valve Failed to Shut Electrically, One Set of Thermal Contacts Would Not Reset
ML17252B5351981-01-23023 January 1981
LER 80-050/03L-0 for Dresden, Unit 2 Re the 1501-62D Pressure Switch Actuated at 44.2 Inches of Water Increasing, Tech. Spec. Limit Is Less than or Equal to 41.6 Inches of Water Increasing
ML17252B5341981-01-23023 January 1981
LER 80-049/03L-0 for Dresden, Unit 2 Re at Completion of Secondary Containment Leak Rate Test the Reactor Building Ventilation Isolation Valve 2A-5742 Would Not Open
ML17252B5371980-12-30030 December 1980
LER 80-046-00 for Dresden 2 Regarding a Failure to Receive CRD Volume During a Reactor Scram
ML17252B5361980-12-29029 December 1980
LER 80-046/03L-0 for Dresden, Unit 2 Re Conditions Leading to on Operation in a Degraded Mode Permitted by a Limiting Condition for Operation or Plant Shutdown Required by a Limiting Condition for Operation
ML17252B5381980-12-0303 December 1980
LER 80-043/03L-0 for Dresden, Unit 2 Re Surveillance Testing of the Condenser Low Vacuum Switches, Pressure Switch 2-503D Was Found to Have a Trip Point of 22.85 Inches Hg
ML17252B5431980-11-12012 November 1980
LER 80-041/03L-0 for Dresden, Unit 2 Re Reactor Building Vent and Refueling Floor Rad Monitor Surveillance (DCP 2007-12) Was Performed
ML17252B5421980-11-12012 November 1980
LER 80-042/03L-0 for Dresden, Units 2 and 3 Re That Technical Staff Personnel Revealed That the Ultrasonic Testing of the Scram Discharge Volume Was Not Performed During the 1500-2300 Shift
ML17252B1841980-10-31031 October 1980
LER 80-40/01T-0 for Dresden Unit 3 Regarding Failure of the HPCI Inboard Steam Supply Valve to Open
ML17252B5441980-10-29029 October 1980
LER 80-039/03X-1 for Dresden, Unit 2 Re HPCI Inboard Steam Supply Valve Opened and Had a Dual Light Indication
ML17252B5451980-10-23023 October 1980
LER 79-017-01X2 for Dresden, Units 2 and 3 Re Inadequacies Observed in Implementation of Administrative Procedural Controls Which Threaten to Cause Reduction of Degree of Redundancy Provided in Reactor Protection System or Engineered Safety
ML17252B5461980-10-0808 October 1980
LER 80-016/01T-1 for Dresden, Unit 2 Re While Shutdown and Conducting 300 Psi Primary System Hydrostatic Leak Inspection, Water Discovered Dripping from LPCI Check Valve Up Stream Drain Line
ML17252B5471980-10-0707 October 1980
LER 80-036/03L-0 for Dresden, Unit 2 Re Discovery That the Six Month Functional Test Required by Tech. Spec. 4.12.A.1 of the Cardox System Heat Detectors Was Not Performed within the Allowable Surveillance Interval
ML17252B5481980-10-0101 October 1980
LER 80-033/03L-0 for Dresden, Unit 2 Re the Frequency of Water Addition to the Torus Increased. Leak Rate Tests Indicated a Leak in the 2B LPCI Heat Exchanger
ML17252B1861980-08-22022 August 1980
LER 80-032/03L-0 for Dresden Unit 3 Regarding During Normal Operations While Performing APRM Rod Block and Scram Functional Tests, APRM 3 Failed to Initiate a Rod Block
ML17252B5501980-08-19019 August 1980
LER 80-027/03L-0 for Dresden, Unit 2 Re Dropping Load in Preparation for I.E.B. 80-17 Scram Tests, Low Level of Diesel Generator Coolant Present in the Water Tank Was Noticed by Equipment Operator
ML17252B5161980-08-14014 August 1980
LER 80-024/03L-0 for Dresden, Unit 2 Re Drywell Oxygen Concentration Indication Failed Downscale in Violation of Tech. Spec. 3.7.A.6.d
ML17252B1881980-08-0404 August 1980
LER 80-030/03L-0 for Dresden Unit 3 Regarding While Reducing Power for Manual Scram Required by I.E. Bulletin 80-17, Routine Surveillance of MSIV Closure Times Showed That MSIVs 3-203-2B and 2D Closed in Less than 3 Seconds
ML17252B1901980-06-13013 June 1980
LER 80-023/03L-0 for Dresden Unit 3 Regarding During Normal Operation with Reactor Level Instrument Surveillance in Progress, Level Switch LIS 3-263-58A Tripped at Less than Tech. Spec. Limit of 144 Inches
ML17252B1911980-06-13013 June 1980
LER 80-024/03L-0 for Dresden Unit 3 Regarding During Normal Operation with Reactor Level Instrument Surveillance in Progress, Level Switch LIS 3-263-58AB Tripped at Less than Tech. Spec. Limit of 84 Inches
ML17252B1921980-06-10010 June 1980
LER 80-025/03L-0 for Dresden Unit 3 Regarding During Normal Operation While Performing Main Steam Line High Flow Isolation Surveillance, Flow Switch DPIS 3-261-2A Was Out of Tech. Spec. Limits, Table 3.2.1
2024-01-19
[Table view] |
Text
B-88 ACCIDENT SEQUENCE PRECURSOR PROGRAM EVENT ANALYSIS LER No.:
Event
Description:
Date of Event:
Plant:
237/90-006 Stuck open safety relief valve followed by a manual scram August 2, 1990 Dresden 2 Summary Dresden had its Target Rock main steam combination safety relief valve (SRV) spuriously lift and stick open for 2.8 h on August 2, 1990. The valve lift was apparently caused by steam cuts on the first stage pilot valve disc. The unit was manually scrammed from 87% power. The conditional core damage probability estimated for this event is 2.6 x 10-4. The relative significance of this event compared to other postulated events at Dresden 2 is shown below.
LER 237/90-006-lE-8 IE-7 IE-6 1E-5 lE-4 1 E-3 III I
I 7
360 ht unava~ij L
L36o'hEP LTRIP IHPCI +IC j OD precursor cutoff.-J LO)FW + HPCI Event Description During a Load Dispatcher requested power reduction from 90% power on August 2, 1990, the operators at Dresden received indication (acoustic monitor alarm, elevated tailpipe temperature, and a 600,000 lbn,/h decrease in main steam flow indication) that the Target Rock SRV had spuriously opened. The operators were unable to close the valve and within 5 min they had started two containment cooling service water (CCSW) pumps and one low-pressure coolant injection (LPCI) pump to try and control the increasing suppression chamber temperature. However, the suppression chamber water temperature continued to rise, so they started the other two CCSW pumps and one additional LPCI pump. About 2 min later the operators manually scrammed the reactor from 87% power. They started the last two LPCI pumps about 3 min after that to
B-89 maximize suppression chamber cooling, and the main turbine main steam bypass valves were opened to limit the heat load on the suppression chamber.
Approximately 2.8 h after it opened the SRV was determined to be closed. The reactor was placed in cold shutdown about 5 h after the event began. The apparent cause of the failure of the Target Rock SRV was a severely steam cut pilot valve disc. Excessive steam leakage through the pilot sensing port and past the pilot valve via the severe steam cuts allowed pressure to be transferred to the second stage piston. The second stage piston was forced down, moving the second stage disc away from its seat. This permitted pressure from the top of the main valve piston to be vented via the second stage disc and out the main valve piston vent. This created a differential pressure across the main valve piston. Reactor pressure then lifted the main valve piston and the main valve disc, thus opening the valve. When reactor pressure reached approximately 100 psig, the main valve preload spring force overcame the reactor pressure force, and the main valve disc subsequently closed. The root cause for the steam cuts on the pilot disc is believed by the utility to be an inherent design deficiency.
The Target Rock SRV indicator on the front panel showed a closed position due to the position indicators receiving their signals from the pressure switches on the drywell pneumatic air line between the solenoid and the SRV. Indication of the open SRV was provided by its acoustic monitor and tailpipe temperature indication, and by a change in main steam flow indication.
When the SRV was inspected in the drywell, an electrical junction box in the vicinity of the valve was found detached from its mounting, and a pressure switch nearby had separated from its conduit. However, both remained functional.
Additional Event-Related Information Dresden 2 has four electromatic main steam relief valves, eight spring-loaded main steam safety valves, and one Target Rock SRV. The relief valves and the Target Rock SRV relieve to the torus below the surface of the water, and the safety valves relieve to the drywell atmosphere.
The Target Rock SRV operates through self-actuation (safety mode) at 1135 psig reactor pressure, or through remote actuation of a solenoid valve that admits a pneumatic supply to an air operator. This remote actuation may occur from the following sources:
- 1. Remote manual switch in the control room.
- 2. High reactor pressure (1115 psig) from a pressure controller.
- 3. Initiation of automatic depressurization system (ADS) logic.
B-90 One other event (LER 237n76-034) like this occurred at Dresden 2 in 1976. The Target Rock SRV was opened during automatic blowdown surveillance testing and it remained open for approximately 3.8 h.
ASP Modeling Assumptions and Approach This event has been modeled as a loss-of-coolant accident (LOCA) due to a stuck open relief valve.
Analysis Results The conditional probability of severe core damage for this event is 2.6 x 10-4 The dominant sequence associated with the event is highlighted on the following event tree.
This sequence involves a LOCA with subsequent HPCI and ADS failure.
The LER for this report includes a detailed description of the operation of the Target Rock valve.
B-91 F iJCA Ix HC SRVs/SD LPCI)
IET SHUT HPI ADS IPOS LPCI SDC o
SEQ END DONMODE) OTHER NO STATE OK OK 71 CORE DAMAGE OK OK 72 CORE DAMAGE OK OK 73 CORE DAMAGE OK 74 CORE DAMAGE OK 75 CORE DAMAGE 76 CORE DAMAGE 77 CORE DAMAGE 96 ATWS Dominant core damage sequence for LER 237/90-006
B-92 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
237/90-006 Event
Description:
Stuck open relief valve followed by manual scram Event Date:
08/02/90 Plant:
Dresden 2 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOCA SEQUENCE CONDITIONAL PROBABILITY SUNS End State/Initiator 1.0E+00 Probability CD LOCA Total ATWS 2.6E-04 2.6E-04 3.OE-05 3.OE-D5 LOCA Total SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence 77 LOCA -rx.shutdown hpci srv.ads 96 LOCA rx.shutdown non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence 77 LOCA -rx.shutdown hpci srv.ads 96 LOCA rx.shutdown non-recovery credit for edited case SEQUENCE MODEL:
c: \\asp\\1989\\bwrbseal.cmp BRANCH MODEL:
c:\\asp\\1969\\dresden.sll PROBABILITY FILE:
c:\\asp\\1989\\bwr-csll.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System trans 3.4E-04 loop 1.6E-05 LOCA 3.3E-06 > 3.3E-06 End State CD ATWS End State CD AT9IS Non-Re coy 1.0E+00
- 3. 6E-01 5.OE-Dl > l.DE+00 P rob 2.6E-04 3.OE-D5
- Prob, 2.6E-04 3.OE-05 N Rec**
5.OE-01 1.DE+DD N Rec**
S.DE-Dl 1.DE+00 Opr Fail Event Identifier: 237/90-006
B-93 Branch Model:
INITOR Initiator Freq:
3.3E-06 rx.shutdown 3.OE-05 1.OE+OO rx *shuitdown/ep 3.5E-04 l.OE+OO pcs/trans 1.7E-01 l.OE+OO arv.chall/trans.-scram l.OE+OO l.OE+OO 3rv.chall/loop.-scram.
l.OE+OO l.OE+OO srv.cloae 1.6E-02 l.OE+OO eznerq.power 2.9E-03 B.OE-Ol ep.rec 6.6E-02 l.OE+OO fw/pcae.trans 2.9E-01 3.4E-Ol hpci 2.9E-02 7.0E-01 isol.cond 2.OE-02 l.OE+OO crd l.OE-02 l.OE+OO l.OE-02 srv.ads 3.7E-03 7.1E-01 l.0E-02 lpcs 2.0E-03 3.4E-01 lpci l.0E-03 7.1E-01 sdc 2.9E-03 3.4E-01 l.OE-03 lpCi (cc) l.0E-03 34E-01 lpci(cc)/lpci l.OE+OO l.OE+OO lpei (cc) /-lpci O.OE+OO 1.OE+OO firewater l.OE+OO l.OE+OO 2.09-03
- forced Minarick 08-06-1991 17:31:17 Event Identifier: 237/90-006
