ML032090226
| ML032090226 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 07/25/2003 |
| From: | Lyon C NRC/NRR/DLPM/LPD3 |
| To: | |
| References | |
| 2003-0546, TAC MB9539 | |
| Download: ML032090226 (63) | |
Text
NRC FORM 658 U.S. NUCLEAR REGULATORY COMMISSION TRANSMITTAL OF MEETING HANDOUT MATERIALS FOR IMMEDIATE PLACEMENT IN THE PUBLIC DOMAIN This form is to be filled out (typed or hand-printed) by the person who announced the meeting (ie., the person who issued the meeting notice). The completed form, and the attached copy of meeting handout materials, will be sent to the Document Control Desk on the same day of the meeting; under no circumstances will this be done later than the working day after the meeting.
Do not Include proprietarymaterials.
DATE OF MEETING The attached document(s), which was/were handed out in this meeting, is/are to be placed in
-7/)51)3 the public domain as soon as possible. The minutes of the meeting will be issued in the near future. Following are administrative details regarding this meeting:
Docket Number(s) 5s)- A65 Plant/Facility Name OLD)b C nE5 L)W IT a-TAC Number(s) (if available) MBqS39 Reference Meeting Notice Wc63-oS46 Purpose of Meeting (copy from meeting notice) AQCj -k. m.-CwxteQ atrfid. &
fi04 CX+A~b 0 lrf 1$ L t NAME OF PERSON WHO ISSUED MEETING NOTICE TITLE C.F. LigzP OFFICE NPDk DIVISION DOLP BRANCH PD3 Distribution of this form and attachments:
Docket File/Central File PUBLIC MRCFORM SW8(9-1999) PRINTED ON RECYCLED PAPER This fom was desd uski IFams
Exeklen SM-Nuclear Quad Cities Nuclear Power Station Unit 2 Steam Dryer Performance Exelon/GENE July 25, 2003 Non-Proprietary Version 1
Exe 1 [I SM Nuclear Meeting AgendalPurpose Tim Tulon Site Vice President Quad Cities Nuclear Power Station 2
Agenda ExebnU d*SM Nuclear
- Meeting Agenda/Purpose Tim Tulon
- Background Tom Wojcik
- Root Cause Determination Keith Moser
- Dryer Repair Evaluation Keith Moser
- QCNPS Unit 2 Extent of Condition Roman Gesior
- Independent Review Team Jim Meister
- Startup and Power Ascension Bud Swenson Monitoring
- Planned Actions Jim Meister
- Status of Regulatory Commitments Pat Simpson
- Conclusion Tim Tulon 3
Purpose exekenSM Nuclear
- Present the results of our root cause determination
- Summarize actions we have taken to address the steam dryer structural integrity issues
- Discuss the relationship of the degradation to extended power uprate (EPU) operations
- Extent of condition on other reactor pressure vessel internal components and main steam line piping
- Describe the program implemented to monitor and detect dryer structural integrity issues
- Provide the basis and schedule for returning Quad Cities Nuclear Power Station (QCNPS) Unit 2 to full EPU power
- Describe plans for QCNPS Unit 1 and Dresden Units 2/3 4
xe:h C,'-)nM Nuclear
Background
Tom Wojcik Engineering Programs Manager Quad Cities Nuclear Power Station 5
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Background===
Dryer Configuration Exk SM Nuclear 6
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Background===
Dryer Nomenclature Exek1en SM Nuclear Outlet Plenum UpperSkiiJt l Vane Bank - Bracket welded to hood Dryer Hoods or Banks Inlet Plenum Mid Support Ring Dryer Skirt The drain channels are located on the inside Section View 7
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Background===
Dryer/Main Steam Line Layout l~ ~
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Nuclear A
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Secton A-A rPule Plan YVew of Steam Dryer Outer Elevaton View Bamk&Steam Outlet Nozles 8
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Background===
Main Steam Line Piping Ex*^emueaSM Nuclear 9
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Background===
Main Steam Line Pipin %rNc e-Nuclear
- ca-t o
&- .X 10
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Background===
Function and Safety Considerations Nuclear
- The function of the steam dryer is to remove moisture from steam exiting the reactor by vanes and perforated plates
- The steam dryer does not perform a safety function
- The steam dryer is not required to prevent or mitigate the consequences of accidents
- Failure Modes and Effects Analysis (FMEA) evaluated the likelihood and consequences for bounding loose parts
- For a degraded dryer, structural integrity is adequate if the safety consequences of any loose part that may be generated are analyzed to be acceptable
- FMEA demonstrates that loose parts will not interfere with the ability to shutdown the reactor, provide adequate core cooling, or isolate the main steam lines
- Safe reactor operation is not compromised by a degraded steam dryer 11
=
Background===
Moisture Carryover Trend Nuclear
- Normal moisture carryover (post-EPU) is less than 0.1%
- April 16: Inadvertent opening of 3B PORV
- May 6: Moisture carryover increased to 0.2%
- May 28: Moisture carryover increased to >0.35%
- Power reduced to pre-EPU level
- Moisture carryover decreased and remained steady at 0.2%
- No significant/actionable changes in key reactor parameters
- June 10: Unit 2 shutdown
- Detailed statistical analysis showed small changes in B main steam line flow and reactor water level fluctuations
- Performed thorough inspection and damage assessment 12
Steam Dryer Visual Inspections Exek 6nSM Nuclear 0 DEORE&S Ps-V Z70 DEGREES (A" ms_ D
-00:,Vjt Z7GTYVIs e4.OAsass tIYEJ 30 DEORES S0a-vA 30tV4 SUPPORT T RINO U.E SKIRT TO RIcO WCLo-f 13
Summary of Inspection Results Exe nSM Nil irltaor ILI
- Damage assessment
- Top of outer hood cover plates
- Through-wall crack (90° side)
- Incipient cracking (2700 side)
- Internal bracing
- Three braces detached in outer 900 hood
- One severed vertical brace in outer 2700 hood
- Three tie bars connecting dryer banks cracked
- Industry experience shows tie bar failures at both EPU and pre-EPU conditions
- Inspected for collateral damage
- None identified
- All loose parts retained within the dryer envelope
- All parts retrieved 14
Damage Assessment 900 Top of Bank A Exek nM Nuclear 15
Damage Assessment 900 Bank A Interior Surfaces ExekNu**SM Nucl ear Detached Interior Diagonal Brace Rank A LI 16
Damage Assessment EExenSMn~
2700 Bank F Interior Surfaces
-~~~~~~~~~~~~~~-
Nuclear Li90
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Interior Diagonal Brace to Hood Weld Bank F 17
Background Exek6nSM Nuclear
- Three teams formed in response to dryer failure
- Root cause team
- Repair team
- Independent review team
- Performed comprehensive analyses to understand failure mechanism and extent of condition
- Dryer repairs and modifications were installed
- Developed and implemented a power ascension monitoring plan
- Unit 2 was returned to service on June 29, 2003 18
Exe lonSM Nuclear Root Cause Determination Keith Moser Asset Management Engineering 19
2002 Dryer Damage Root Cause Overview xe on Nuclear
- QCNPS Unit 2 was shutdown on July 11, 2002, due to suspected steam dryer degradation
- Visually inspected outer surface of dryer
- Dryer cover plate (at hood-skirt transition) damage
- Cover plate natural frequency approximately 180 Hertz
- No additional damage observed
- Root cause was high cycle fatigue due to high frequency acoustic resonance (130 to 230 Hertz) 20
2002 Dryer Damage Root Cause Overview Nuclear
- Extent of condition review was focused on components susceptible to high frequency (130 to 230 Hertz) flow induced vibration (FIV)
- Dryer repairs were completed
- Both cover plates were replaced with thicker plates using larger welds
- Continued to evaluate failure to improve understanding of dryer loading
- Computational Fluid Dynamic (CFD) analysis
- Scale model testing
- Full 3-D finite element model 21
2003 Dryer Damage Root Cause Overview Exek~nEM Nuclear
- Utilized diverse analytical techniques
- CFD analysis
- Scale model testing
- Full 3-D finite element model
- Acoustic circuit evaluation
- Metallurgical evaluation
- Expanded evaluation methodology applied
- Expanded extent of condition review
- 0 to 230 Hertz frequency ranges considered
- Reactor internals for EPU conditions
- Steam path components for EPU conditions
- The root cause of the dryer failure is high cycle fatigue resulting from low frequency pressure oscillations 22
Root Cause Evaluation Methodology E l%
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_W Gujsm Nuclear
- 1. Identify potential causes
- 2. Identify locations where failure could occur for various postulated root causes
- 3. Identify the attributes of damage associated with each root cause mil
- 4. Correlate crack locations with root cause
- 5. Rank the probable root cause for the observed failure location and damage attributes 23
Dryer Potential Root Causes Eif EAL Exek nSM Kh irlonr
- Evaluated credible potential root causes I
- Material/fabrication issues
- Weld defects
- Poor quality plate material
- Fatigue due to pre-EPU operation
- Intergranular Stress Corrosion Cracking (IGSCC)
- Dryer support ring deflection
- Bi-stable flow
- Increased stress from 2002 cover plate failure
- Transient loading due to power operated relief valve (PORV) operation
- EPU increased steam flow effects on original dryer design
- FIV high frequency (130 to 230 Hertz)
- FIV medium frequency (50 to 130 Hertz)
- FIV low frequency (0 to 50 Hertz)
- Sources from main steam lines
- Sources inside reactor pressure vessel 24
Analysis Technique Exe Ie~n S Nuclear
- CFD Model
- Steam dryer, steam dome, portion of main Velocity steam lines in model -283. 50
- Velocity and pressure -213.63 fields in/around dryer computed at steady state j~ -143.7S EPU conditions
- 73.88
- Outputs incorporated into I,
finite element structural evaluations
- 4. 00 Ift SA.Ij1 Ali 25
CFD Model Results EPU Steam Dryer Flow Patterns ExeIn SM Nuclear GE Proprietary Information 26
Analysis Technique and Results ExeI On SM Nuclear GE Proprietary Information 27
Analysis Technique Exe InSM Nuclear GE Proprietary Information 28
Finite Element Model Results ExeIAnS.
Nuclear GE Proprietary Information 29
Finite Element Model Forcing Functions ExeI16n S.
Nuclear GE Proprietary Information 30
Analysis Technique Exek6nSM Nuclear
- Acoustic Circuit Analysis
- Purpose is to locate potential sources of low frequency pressure waves
- Model identifies potential acoustic drivers in system
- Predicts system nominal acoustic frequencies 31
Acoustic Circuit Analysis Results exe I Ism Nuclear GE Proprietary Information 32
Analysis Technique Ex ueIn.a Nuclear
- Metallurgical Evaluation
- Base/weld material I
- Chemical properties I
- Mechanical properties
- Scanning electron I microscopy (SEM)
- Metallographic 4-examinations 2700 Hood Top Plate 33
Metallurgical Evaluation EII SEM of Hood Horizontal Plate Fracture Surface XeInfSM
~I m momd 1011 Nuclear 34
Metallurgical Evaluation Results ExekWnSM Nuclear
- The cause of the steam dryer hood cracking was high cycle fatigue; final fracture resulted from decompression wave (PORV actuation)
- The fractures initiated at the stress concentrations at the bracket joint to the interior surface of the hood
- No weld flaws were identified
- Crack propagated lengthwise at a higher rate
- Remaining ligament on 90° side is 0.03 inch through-wall
- Remaining ligament on 2700 side is 0.1 inch through-wall
- No chemistry, material, welding, or manufacturing deficiencies were identified
- No evidence of IGSCC was observed 35
Assessment of Load Frequencies Causing Damage ExeIonSM Nuclear GE Proprietary Information 36
Root Cause Summary Exek6nSM Nuclear The root cause of the dryer failure is high cycle fatigue resulting from low frequency pressure oscillations
- The cracks in the hoods and braces started during normal EPU power operation at the high stress location of the bracket plate on the outer hood
- The length of the cracks continued to increase until the transient pressure loading from the inadvertent 3B PORV opening and subsequent valve openings caused the crack to open through-wall (remaining ligament 0.03 inch), leading to the observed increased moisture carryover
- Most likely source of loading is main steam line D-ring acoustic frequency 37
Contributing Factors Exe 6nsM Nuclear
- Operation with failed cover plate in 2002 resulted in increased fatigue damage in the 90° hood area
- PORV opening caused a decompression wave
- 2 to 3 times steady state loading on degraded hood
- Small remaining ligament (approximately 0.03 inch through-wall) on the 900 hood failed
- This provided an opening which resulted in an increase in moisture carryover 38
ExeIonSM Nuclear Dryer Repair Evaluation 39
Loadings in Dryer Evaluation Low Frequency FIV Peak Loading Magnitude LXeIfnSM Nuclear
- Performed dryer evaluation to determine loads for repair design
- Calculated loads based on observed cracks
- Scale model testing
- Evaluation based on turbulent fluid flow theory resulted in lower values
- Benchmarked against observed vendor in-vessel measured data
- Spatial distribution determined by CFD modeling
- Determined bounding low frequency pressure load 40
Dryer Structural Evaluation Exek nsM Nuclear
- Load conditions
- Bounding low frequency pressure load
- Dead weight load and dryer support ring fluctuations
- Pressure load corresponding to PORV event (all main steam lines simultaneously)
- Repairs performed to address high-stress locations and evaluated with bounding loads 41
Repair Design Exel 1nSM Nuclear GE Proprietary Information 42
Dryer Analysis With Repairs Finite Element Analysis Model Exek n M Nuclear GE Proprietary Information 43
Repair Evaluation ExekW nsM
- Optimization analyses Nuclear
- Selected designs to move plate frequency to a region of low excitation
- Decreased stress levels below the previous stress levels by a factor of two or more
- Diagonal and vertical braces
- Diagonal bracket attachment led to higher stress concentrations at the hood - now removed
- Finite element model showed little change with brackets and braces removed
O vnSM ExeI Nuclear QCNPS Unit 2 Extent of Condition Roman Gesior Director, Asset Management 45
QCNPS Unit 2 Extent of Condition Scope of Impact on, Non-Dryer Components Lxelo M Nuclear
- Evaluated EPU changes to identify potentially impacted components
- Components included in review
- Reactor internals
- Components instrumented during startup testing
- Components in steam path
- External steam path
- Main steam line piping
- Steam path components 46
QCNPS Unit 2 Extent of Condition Evaluation Methodology xe 6nSM Nuclear EPU effects
- Constant pressure and temperature - uprate changes:
- Core power: +18%
- Core flow: no change
- Feedwater/steam flow: +20%
- Feedwatertemperature: +16'F
- Reactor internal pressure differences (RIPD): up to 2.2 psid
- Slight increase in recirculation pump speed and carryunder
- Component evaluation
- Focused on EPU parameter changes
- Root cause insights from QCNPS Unit 2 dryer failure factored into additional evaluations 47
QCNPS Unit 2 Extent of Condition Evaluation Methodology xe onm Nuclear
- Evaluation methods
- Startup testing scaled to EPU conditions
- Development testing
- Frequency evaluations
- Plant monitoring data
- Screening criteria
- Component natural frequency
- Susceptibility to low frequency loading
- Susceptibility to high frequency loading
- Failure history
- Loose part assessment
- Safety consequence 48
QCNPS Unit 2 Extent of Condition Screening Matrix Exe IfISm Nuclear GE Proprietary Information 49
QCNPS Unit 2 Extent of Condition Results Matrix Exel flnSM Nuclear GE Proprietary Information 50
QCNPS Unit 2 Extent of Condition Summary xe 6 n Nuclear
- Reactor internal components and components in the steam flow path were evaluated in light of the dryer failure
- Detailed evaluations were performed for these components to determine their susceptibility to FIV at EPU conditions
- Evaluations validate the results of previous EPU component analyses
- QCNPS Unit 2 can operate at EPU conditions without exciting internal or main steam line components above established vibration limits 51
xe o nSM Nuclear Independent Review Team Jim Meister Vice President, Engineering 52
Independent Review Team ExeI+/-nSm Nuclear
- External independent review team was comprised of members from Structural Integrity Associates (SIA)
- Assessed repairs (prior to QCNPS Unit 2 restart) and root cause evaluation
- Provided additional areas to include for main steam path extent of condition evaluation
- Conclusions
- The dryer failure was due to high cycle fatigue, other potential failure mechanisms have been eliminated
- The load definition is reasonable, especially considering repair margins are on the order of 2 to 3
- An adequate structural evaluation has been performed to:
- Understand failure locations
- Ensure adequacy of repair
- Evaluate the acceptability of not replacing the diagonal braces
- Dryer repair will lead to an improvement in structural performance 53
ExekOnsm Nuclear Startup and Power Ascension Monitoring Plan Bud Swenson Plant Manager Quad Cities Nuclear Power Station 54
QCNPS Unit 2 Dryer Performance Results to Date : 6nsm
- High frequency acoustic monitor Nuclear
- No vibration alarms during or after power ascension to full pre-EPU power (2511 MWt)
- Moisture carryover
- Current value is 0.01% at 2511 MWt
- Main steam line vibration monitoring results
- Readings taken at approximately 53%, 76%, and 85% rated thermal power
- Evaluation concluded vibration readings were not indicative of a challenge to main steam line performance or a change in dryer performance
- Key parameter review (monitored and recorded reactor pressure, reactor water level, main steam line flows, and steam-feed flow mismatch on an hourly basis)
- No adverse trends identified
- No indications of steam dryer structural integrity issues 55
Overview of Power Ascension Plan 2511 MWtto2957MWt 6nm Nuclear
- Steam dryer monitoring plan will be implemented from the current power level of 2511 MWt to full EPU power
- Evaluation points will be established at 92% thermal power (approximately mid-way) and at full EPU power; each evaluation point will include:
- Documented review and assessment of plant data
- Moisture carryover
- High frequency acoustic monitor
- Main steam line vibration levels
- Key reactor parameters
- Plant Operations Review Committee will be convened to perform an assessment of continued power ascension/operation
- On a weekly basis until the next refuel outage, an engineering review and documented assessment of dryer performance will be performed considering trends in reactor power, reactor water level, main steam line flow, and steam-feed flow mismatch 56
ExelnS Nuclear Planned Actions Jim Meister Vice President, Engineering 57
Planned Actions h i01 SM 1 irlionr "I
- Monitoring plan
- Comprehensive plan to provide early detection of dryer structural integrity issues
- Implemented daily monitoring of moisture carryover and other key reactor and plant parameters while operating at full power
- Detailed dryer visual inspections of susceptible areas will be performed during the next refueling outage on each unit
- VT-3 methodology will be used
- Based upon inspections and further evaluations, the Dresden and QCNPS Unit 1 dryers will be modified as necessary
- Insights from QCNPS Unit 2 finite element modeling will be applied 58
Exek~t1nSM Q
Nuclear Status of Regulatory Commitments Pat Simpson Manager, Licensing 59
Status of Regulatory Commitments Exe enSM Nuclear Commitment Status Repair dryer and perform assessment to determine Complete acceptability to operate at full pre-EPU power level Complete Implement daily monitoring of moisture carryover and Complete other key reactor parameters If dryer structural integrity concerns are identified, power levels will be reduced to pre-EPU levels on the affected No change in status unit Re-evaluate monitoring parameters and frequency Complete - no following root cause evaluation changes recommended Evaluate the effects of EPU conditions on reactor internal Complete components and main steam line piping ____ee_ ]
If required, supplement previous EPU licensing August 15, 2003 correspondence 60
Status of Regulatory Commitments Exek=nsm Nuclear Commitment Status Complete root cause evaluation including metallurgical Complete analysis No change in status -
Perform detailed finite element analysis and inspect next refueling outages susceptible areas at Dresden and QCNPS Evaluate the insights gained for QCNPS Unit 2 dryer No change in status -
failure for impact on similar designs, share generic September 5, 2003 issues with BWROG Evaluate and disposition extent of condition on reactor Complete vessel internal components and main steam line piping Submit voluntary LER No change in status -
]_SubmitvoluntaryLER l August 22, 2003 61
Conclusion Exek5 -* *S Nuclear
- Root cause of the dryer failure is high cycle fatigue resulting from low frequency pressure oscillations
- The repaired dryer is qualified for bounding loads at EPU flow conditions
- Extent of condition evaluation of reactor internals and main steam path components identified no concerns
- -A comprehensive program for monitoring and detecting dryer structural integrity issues has been established