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

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MEETING ATTENDANCE LIST

Licensee: Entera

Plant: Vermo

Subject: Steam

Date: July 22, 2004

nt Yankee Nuclear Power Station

Dryer Analysis Associated with Extended Power Uprate Request

Time: 8:00 a.m.

Location: NIR ( HPWnnlr inrforc rlA;FK Rnnm I ('I CI .- - -*-ttJ1t 1tS . .' V V * * I * *tfl*, * .4 S I

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UBWR Steam DryerStructural Analysis Methodology

July 21, 2004"IDye trctra Mars etiodl ogAebg121¶O 42J

Agenda

* Meeting Goals* Meeting Structure* EPU Operating Experience* Fluctuating Load Definition* Structural Analysis Techniques* Finite Element Model* Fatigue Structural Analysis* Load Combinations* Transient and Accident Load Definitions* Primary Stress Structural Analysis

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Meeting Goals

* Update NRC technical staff on BWR steam dryerstructural analysis methodology

- Load definition- Structural analysis

* Provide generic basis and background informationsupporting EPU dryer analyses

* Provide information supporting VY dryer analysisreview

Significant improvements in methodology havebeen made over the last year

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Meeting Structure

* Informal question/answer format- Similar to technical audit- Not a structured presentation

* Review- Detailed analysis results- Design record files- Spreadsheets, etc

* Review of generic methodology- Vermont Yankee EPU analysis used as example

* Copies of materials requested by the staff will beformally provided after the review

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GENE Technical Discussion Leaders

* Fluctuating Load Definition* Structural Analysis

Techniques* Finite Element Model* Fatigue Structural Analysis* Load Combinations* Transient and Accident

Load Definitions* Primary Stress Structural

Analysts

Dan PapponeRichard Wu

Alex PinskerHenry HwangHenry HwangDan Pappone

Henry Hwang

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Steam Dryer Design Basis

* 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 |

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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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Hood Failure Locations

_I Top of Outer Hood

- Location)

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Review Topics

* Load Definition

* Structural Analysis

* Plant Application

Conclusions

* Significant progress in structural analysismethodology

* Overall methodology is conservative

* Dryer modifications assure structural integrity atEPU conditions

- Increased design margin at critical locations

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Closed Session

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Fluctuating Load Definition

* Generic load definition- Assumptions- In-plant test data- Scale model test data- Reference load definition

* Plant-specific application- Load scaling

* Load definition confirmation

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Structural Analysis Techniques

* Equivalent static method- Frequency analysis using reference load- Load scaling- Dynamic amplification, stress concentration

factors

* Response spectrum method- Pressure load to response spectrum transform

* Acceptance Criteria

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Finite Element Model

* Model Assumptions

* Dryer components modeled

* Shell model

* Solid submodels

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Fatigue Structural Analysis

* Analyze current power, EPU power conditions

* Benchmark current power results againstacceptance criteria

* Evaluate EPU results against acceptance.i er

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Load Combinations

* Operating conditions- Normal

- Upset- Faulted

* Loads considered- Deadweight- Static differential pressure- Seismic

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Transient and Accident Load Definitions

* Differential pressure loads- Forward flow transients (e.g., SORV)- Reverse flow transients (e.g., TSV)- Steamline break accident

* Seismic loads-OBE- SSE

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Primary Stress Structural Analysis

* Analyze individual load components for eachoperating condition

* Combine stress results for individualcomponents

* Assess overall stress results againstacceptance criteria

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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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.n Industry Steam Dryer Experience_i n _ .aafl .i..M . .-

Ma | Nearly 50 Reactor Operating Years of EPU Experience

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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

9

--En tefgy

VY Steam Dryer Inspection

7 .Internal & external visual inspection of steam dryeraccessible areas

* No outer bank or lower cover plate cracking found

10

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

11

=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

* Employed low carbon stainless steel - IGSCC resistant

12

'-~ Eterg-y

.. ,�.. Z -��MINh*II VY Dryer - Before & After Strengthening

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m AdVY Steam Dryer Strengthening - Tie Bars

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hitEr Y Steam Dryer Strengthening - Hood

15

-- -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)

16

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

18

1 -En te gy.. .

I. ,. .-dVY Steam System Data Collection Map

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RPV LevelInstrumentReference Leg

High SpeedPressureSensors -

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19

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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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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

21

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