MEETING ATTENDANCE LIST Licensee: Enterov Plant: Subject: Vermont Yankee Nuclear Power Station General Electric Steam Dryer Analysis Methodology Date: July 21, 2004 Time: 8:00 a.m. Location: NRC Headquarters, TWFN Room 8A1 Name Title Organization 15"O Ais Mf IC I nq4UVL 0 P"C~ ~1 PJr'-Io De-.l 4zg ~n-k c-F4~t~A L~S'e~cE? GAPL ew~i /41 ~c Fh ske- e &V,0104~A-s !I 5r-r -r'tee AtLC, I/4L4 XMEg- SC-HjAe6- i'f1PA6E12-~ 44 -Q CAfm Cty-7~ -2-5-1M_ _ _ __A W_ _ _ _ _ _ -7 t :i csht~ -& 67 1, 64~r/ /97/6d• _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ A l 2 . -7 k ATTI!C~4mtxr t
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2004/09/02-Attachments 1 through 4 of 07/21/2004 & 07/22 ... · BWR/3 Dryer Failure History (QC2) lower cover plate at QC2 High cycde fatigue due to high frequency fluctuating pressure
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* Original Design Requirements- Not ASME-coded component- Fatigue from flow-induced vibration not explicitly considered- Maintain structural integrity for outside steamline break accident
* No loose parts* Deformation acceptable
* Current Dryer Analyses- Finite Element Model of dryer- Fluctuating pressure loads defined- Fatigue from flow-induced vibration analyzed- Normal, upset, faulted conditions analyzed- ASME code criteria used as guidance for modifications
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EPU Operating Experience
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I Nearly 50 Reactor Operating Years of EPU Experience |
11 ., St -d r?,nal1- I Methodology- I'l
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Relative Hood Stresses
o14160 psi zvv366 psi
Flat Hood With Strut, Sianted Hood With Plates
2294 psi
vYNS Modifiede650 psi Dryer
FHlt Hood Without StrutsCarved Hood With flates
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Overall Dryer Screening120
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BWR/3 Dryer Failure History (QC2)
lower cover plate atQC2
High cycde fatiguedue to highfrequency fluctuatingpressure (120-230Hz) thin cover plate,small welds, potentialresonance
Replaced coverplate with Wplate
Developed dryer cornponenlstructural analysis
Used more robust attachmentwelds.
May 2003 Cracks In outer High cycle fatigue Removed diagonal braces Modifed dryer structuralhood, broken due to low frequency from outer hoods analysis to account forbraces and struts In tluctuating pressure Replaced outer hood pltes fluctuating pressure leadthe outer hood loading Hz) Rethac-dpcuter ooda definition over fuit frequency
teotrho opeationg wi Hz with 11 plate range. for aSl dryer typesdamaged ovwer plate Added external gussetscontributing factor
March Cracks In plate at Local stress Fult height 1 vertical hood Solid submodelsforNigh2004 gusset lps, broken concentrations not plate stress locations used to
tie bar welds modeled In sufficient Futt height external gussets supplement 3D shell FinitedetaEliln model
Full penetration shop welds on Analysis Incldes gusset Uspexternal gussets design and weld design
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a-%Entergy
Entergy VYPower Uprate Project
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Steam Dryer RAI Revieew
July 22, 2004
1
-EnStmgy
< Main Steam Dryer- p
2
7w What we know-I.
Significant improvement in methodology- Dryer Finite Element Model adequately reflects dryer
performance under defined loadVY Modified Dryer relative stresses are less thanother dryer types under the same load
* Dryer Loads are adequately defined* VY Steam Line velocity at EPU is less than
QC/Dresden original steam velocity* Reasonable Assurance that Dryer will perform per
current design requirements at Extended PowerUprate Conditions at Vermont Yankee
3
Future Activities
Obtain and evaluate VY Plant Specific data* Comprehensive, deliberate, well monitored
power ascension
4
Quad Cities Experience
Methodologies developed after QC2 failuresaccurately predict high stress locationsConfirmed by actual high stress failurelocations
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a Etergy..- -. .,,-r~
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.n Industry Steam Dryer Experience_i n _ .aafl .i..M . .-
Ma | Nearly 50 Reactor Operating Years of EPU Experience
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"'I.'trt Main Steam Line Flow Velocities220.0
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-En terg
VY Steam Dryer Analysis
GE developed Finite Element Model of VY Dryer. Loads defined based on similar plant instrumented
dryer dataResults: identified increased stress areas at uprateconditionsDeveloped robust modification - industry experienceincorporatedRe-ran the Model incorporating the modification andvalidated stresses were below Code limits at uprateconditionsSignificantly increased structural margin
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--En tefgy
VY Steam Dryer Inspection
7 .Internal & external visual inspection of steam dryeraccessible areas
* No outer bank or lower cover plate cracking found
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a=Enteergy
VY Steam Dryer Inspection7 .Some visual indications were found: consistent with BWR industry
experience• Two 3" cracks in dryer steam dam were repaired & strengthened
. Caused by fabrication residual stressesSeveral intergranular stress corrosion cracks (IGSCC) were found(dryer end bank and drain channel)
. Caused by sensitization and weld residual stresses fromoriginal welding
. Not structurally significant
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=I e rtfgy
Steam Dryer - Strengthening Design
Modifications• Lower cover plate - Increase from 1/4" to 5/8" Upper vertical and
horizontal cover plates in outer hood - Increase from 1/2" to I"• Remove internal diagonal shipping braces
. Eliminate stress concentrators which were the crack initiators for theQuad Cities Failures
* Replace dryer bank tie bars and improve weld attachment• Add six, full-length external gussets to hood plates
Full penetration versus fillet welds. Gusset shoe provides enhanced weld strength
.. ,�.. Z -��MINh*II VY Dryer - Before & After Strengthening
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Before| After 13
A-- Eergy
m AdVY Steam Dryer Strengthening - Tie Bars
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Af-
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V4 -- '7= M. .y
hitEr Y Steam Dryer Strengthening - Hood
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-- -Entergy
VY Steam Dryer Monitoring
* Measurements consistent with SIL 644* Moisture carryover levels• System parameters (flow and level)
* Inspection in planned refuel outage ('8months of <115% uprate operation)
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W tergy
~I.- ,-W VY Acoustic Circuit Model
m Collect VY Main Steam Data
* Develop Acoustic Circuit Model
n Reconcile Test Results with GE Analysis
17
-Entifflgy
, VY Main Steam System Data Collection
. Measurement locations more extensive than otherstations* Pressure data taken with high speed recorder at:
• MSL venturis (one on each steamline)
• Vessel instrument reference legs (2)
* Main steam header
. Strain Gauges located on each steam line close to vessel
* Data taken at 80%, 85%, 90%, 92%, 95%, 97% and100% power
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1 -En te gy.. .
I. ,. .-dVY Steam System Data Collection Map
-.
RPV LevelInstrumentReference Leg
High SpeedPressureSensors -
(10)
I
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-5 . I.4-V e '!L..
VY Steam Dryer TimelineFeb 2004 Mar2004 , Apr 2004 " May 2004 Jun 2004 Jul 2004 , Aug 2004 X Sep 2004
I I I I I I I IVY Review/
Oversight
Tech ReviewRAI Set iSubmittal
GE AuditRAI Set 2Submittal
Design
Inspection
Modification
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APiping Vibs Data
MS System Data
Acoustic Ckt
ACM Complete
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VY Uprate Testing and, ___.._._.._._.____ .eInspection Plan
* Two Step Uprate
* Gradual Power Ascension Test Plan with predefined hold points* Pre-uprate testing provides baseline data
* Measurement program• Main Steam and Feedwater FIV Accelerometers• Steam System Pressure Transmitters• Main Steam Line Strain Gauges• Installed Plant Equipment
Inspection in planned refuel outage (8 months of <115% uprateoperation)n Detailed inspection consistent with SIL 644