LPR Mod lar CodexLPR Modular CodeA Probabilistic Approach to LBB

David RudlandU.S. NRC RES/DE/CIB

NRC-Industry 2011 Meeting on Alloy 690 ResearchNRC-Industry 2011 Meeting on Alloy 690 ResearchRockville, MD

Tuesday, June 7, 2011

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y, ,

GDC-4 and LBBGDC 4 and LBB

• 10CFR50 Appendix A GDC-4 allows local dynamic effects of pipe ruptures to be excluded from design basis if pipe ruptures have extremely low probability of occurrenceof occurrence

• Local dynamic effects include pipe whipping and y p p pp gdischarging fluids

C i i d ti fl t l• Commission-approved conservative flaw tolerance analyses developed and incorporated in SRP3.6.3 to demonstrate leak-before-break and satisfy GDC-4demonstrate leak before break and satisfy GDC 4

• One screening criterion in SRP3.6.3 requires no active

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degradation mechanismvg 2

xLPR P bl / M ti tiProblem / Motivation

• PWSCC is an active degradation mechanismg

• LBB approved for piping systems prior to PWSCC operational experienceoperational experience

• LBB systems still in compliance with regulations

• Qualitative: mitigations and inspections

• Quantitative: probabilistic evaluation to assess compliance (xLPR)

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xLPR DevelopmentxLPR Development

• NRC goal to develop “Modular” code for addressing i l d i k f d iissues related to Risk of Pressure Boundary Integrity Failure

Internal External

Review boardACRS

Industry and NRC staff and contractors

• Currently focusing on piping issues (xLPR) to solve current LBB need. May be applicable to other needs

Models Group

AcceptanceCriteria

Computational Group

May be applicable to other needs

• Working cooperatively with EPRI through a Memorandum of Project

IntegrationInput Groupthrough a Memorandum of

Understanding Addendum• NRC and Industry staff participation in all aspects of• NRC and Industry staff participation in all aspects of

code development

I i i l il d ff i f h06/07/2011vg 4

• Initial pilot study to assess effectiveness of approach

Team MembersTeam MembersComputational GroupDavid Rudland – U.S. NRCBruce Bishop – Westinghouse

Models GroupMarjorie Erickson – PEAIGary Stevens – U.S. NRCp g

Nathan Palm – Westinghouse Patrick Mattie – Sandia National LaboratoriesCedric Sallaberry – Sandia National LaboratoriesDon Kalinich – Sandia National LaboratoriesJon Helton – Sandia National LaboratoriesHilda Klasky – Oak Ridge National LaboratoryPaul Williams – Oak Ridge National Laboratory

yHoward Rathbun – U.S. NRCDavid Rudland – U.S. NRCJohn Broussard – Dominion EngineeringGlenn White – Dominion EngineeringDo-Jun Shim – Emc2

Gery Wilkowski – Emc2

Bud Brust – Emc2g yRobert Kurth – Emc2

Scott Sanborn – Pacific Northwest National LaboratoryDavid Harris – Structural Integrity AssociatesDilip Dedhia – Structural Integrity AssociatesAnitha Gubbi – Structural Integrity Associates

Cliff Lange – Structural Integrity AssociatesDave Harris – Structural Integrity AssociatesSteve Fyfitch – AREVA NP Inc.Ashok Nana – AREVA NP Inc.Rick Olson – BattelleDarrell Paul – BattelleLee Fredette – Battelle

PEAI

Craig Harrington – EPRIGabriel Ilevbare – EPRIFrank Ammirato – EPRIPatrick Heasler – Pacific Northwest National LaboratoryBruce Bishop – Westinghouse

Inputs GroupEric Focht – U.S. NRCMark Kirk – U.S. NRCGuy DeBoo – ExelonPaul Scott – BattelleAshok Nana – AREVA NP Inc.John Broussard – Dominion Engineering

Program Integration BoardCraig Harrington – EPRIAladar Csontos – U.S. NRCRobert Hardies – U.S. NRCDenny Weakland - Ironwood Consulting

John Broussard Dominion EngineeringNathan Palm – WestinghousePat Heasler – Pacific Northwest National LaboratoryGery Wilkowski – Emc2

Acceptance GroupM k Ki k U S NRC

David Rudland – U.S. NRCBruce Bishop WestinghouseMark Kirk – U.S. NRC

Glenn White – Dominion Engineering Inc.Aladar Csontos – U.S. NRCRobert Hardies – U.S. NRCDavid Rudland – U.S. NRCBruce Bishop – WestinghouseRobert Tregoning – U.S. NRC

Bruce Bishop – WestinghouseEric Focht – U.S. NRCGuy DeBoo – ExelonMarjorie Erickson – PEAIGary Stevens – U.S. NRCHoward Rathbun – U.S. NRCMark Kirk – U.S. NRCGlenn White Dominion Engineering Inc

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Glenn White – Dominion Engineering Inc.

vg 5

xLPR – NRC Intended Use C te ded Use• Version 1.0 – Pilot study – Surge nozzle DM weld

To demonstrate feasibility– To demonstrate feasibility– Determine appropriate probabilistic framework– Develop plan for future versionp p

• Version 2.0 – Primary pipingS pport LBB Reg lation G ide de elopment– Support LBB Regulation Guide development

– Assess compliance with GDC-4– Prioritize future research effortsPrioritize future research efforts

• Version 3.0 – Reactor coolant pressure boundary C bi i i ith t l t t t– Combine piping with reactor vessel, steam generator, etc.

– Analyze probability of failure for all coolant pressure boundary components

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y p

xLPR ProcessxLPR Process

Epistemic loop

Aleatory loopPurple boxes represent

self-contained, independent modules

From Main Loop

Load Module

Epistemic – Lack of Knowledge uncertainty

t=t+1

Leak Module-Leak Rate

Critical Flaw Module Critical?

COD Module

t>tf

no

yes

Knowledge uncertainty

Aleatory – Irreducible uncertainty

Crack Growth M d l

TWC

SCCritical?Inspection

Module-POD yesno

SC

TWC

yes

Stress IntensityM d l

PreemptiveMitigate?

y

Probability of Crack Initiation

Module

Module

Crack Coalescence

Moduley

leak/rupture

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Crack Coalescence Module

Version 1.0 Models DescriptionDescription

Crack InitiationSeveral models are available for initiation probabilityA.) Direct Approach) pp

nRTQ

I

Aet

σ/1 −= ( thσσ > ) )]1/()ln[(/]ln[

)]//()ln[(/

zzDDmBBwhere

zzDBetq

I

ysRTQ

I

−−=

−−= σσ

B ) Weibull

It Iσth = 137MPa (20ksi)

0.40.50.60.70.8

zB.) Weibull3)/(1)( Ct

I ettP −−=< 00.10.20.3

1 1.5 2 2.5 3

σth = zσy

)( InRTQeCC −= σ/

1

1 1.5 2 2.5 3

siguts/sigys

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• Capable of handling zinc/hydrogen changes, but not implementedvg 8

Models DescriptionModels DescriptionCrack Initiation

• For Version 1 0, models are “calibrated” to MRP-216For Version 1.0, models are calibrated to MRP 216 surge nozzle data and base WRS

Pressurizer Nozzle DMW Inspections (mid 2007)

Nozzle # inspected # circ cracks # axial cracks

Surge 10 5 2

Safety 20 1 4

Relief 6 1 2Relief 6 1 2

Spray 7 0 0

0.01 cracks/year

• Multiple circumferential crack initiation allowed• Axial cracks added in Version 2.0

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Models DescriptionModels Description

Crack Growth from MRP-2632

/1 ( 1) exp 0.5 Ni NiOP ECPP P c

− Δ + −

1 1exp ( )βweld thf

QCGR f K KR T T

= − − α − P P c refR T T

For K<Kth, CGR=0

[ ][ ]

2/

2 /

273.1529.58 log298.15Ni NiO

Ni NiO

HTECPH

+ Δ = [ ] (0.0111 2.59)

2 /10 T

Ni NiOH −=

CGR = crack growth rate at temperature T in m/sQg = thermal activation energy for crack growth = 130 kJ/mole R = universal gas constant = 8.314 x 10-3 kJ/mole-K T = absolute operating temperature at the crack location in KTref = absolute reference temperature to normalize data = 598.15K α = power law constant = 2.01 x 10-12 Kth = threshold crack stress intensity factor = 0.0 MPa-m0.5 β = exponent = 1.6

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β pH2 = 25 cc/kg-STP

xLPR FrameworkxLPR Framework

Fully Open Source GoldSim Commercial CodeFully Open Source GoldSim Commercial Code

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Pilot Study ProblemsPilot Study Problems

Analysis DescriptionAnalysis Description

Probabilistic Base Case Probabilistic base case analysis using Monte Carlo sampling.

Sensitivity StudySensitivity Study

Stress Mitigation Analyses evaluate different mitigation times, for the same stress-based mitigation.

Chemical Mitigation

Chemical effects of increasing the hydrogen concentration in the water on the crack growth module. Three hydrogen concentrations were

evaluatedevaluated.

Crack Initiation Considers the crack initiation model uncertainty.

Considers stainless steel safe end weld, which causesSafe End Evaluation

Considers stainless steel safe end weld, which causes a through-thickness bending stress that can reduce

the tensile inner-diameter stress.

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UncertaintyUncertainty

• Uncertainties were classified by models/inputs groupUncertainties were classified by models/inputs group• More discussion needed, but satisfactory for pilot

studystudyEpistemic (Lack of knowledge) Aleatory (Irreducible)

• Loads • Crack size• Loads• WRS• Crack growth (fweld)

C k i i i i

• Crack size• POD detection• Material properties

C k h (Q/R P)• Crack initiation parameters• POD parameters

• Crack growth parameters (Q/R,c,P)

• Currently uses LHS (epistemic) and MC (aleatory) • Importance sampling was demonstrated

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Base Case ResultsBase Case Results

Problem is driven by crack initiation!!

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Grey lines represent individual epistemic realizations

Base Case ResultsBase Case Results

Sensitivity analyses were conducted to d t i d i i i bl

var. R2 R2 inc. SRRC var. R2 R2 inc. SRRCSIG0WRS 41 80% 41 80% 0 5363 SIG0WRS 43 90% 43 90% 0 5764

EXPCFO: 50 yr EXPCFO: 60 yr

determine driving variables

SIG0WRS 41.80% 41.80% 0.5363 SIG0WRS 43.90% 43.90% 0.5764B1 57.10% 15.30% -0.3299 B1 60.70% 16.80% -0.3568FWELD 57.80% 0.70% 0.0701 FWELD 61.60% 0.90% 0.0853RANDL17 58.00% 0.20% 0.0369 RANDP05 61.80% 0.20% 0.0391

ODRAND 62.00% 0.20% -0.0358

• R2 - how much of the output variance is explained with the current input and all

i i tprevious inputs

• The incremental R2 - how much variance is explained by the addition of this inputis explained by the addition of this input

• SIG0WRS – ID weld residual stress

• B1 crack initiation parameter

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• B1 – crack initiation parameter

Safe End Sensitivity CaseCase

80

n

30

40

50

60

70

Dis

trib

utio

n Fu

ncti

on

0

10

20

4.6E-08 6.7E-07 1.3E-06 1.9E-06 2.6E-06 3.2E-06

Prob

abili

ty

Mean Probability of Rupture

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Pilot Study ResultsPilot Study Results

• The project team demonstrated that it is feasible toThe project team demonstrated that it is feasible to develop a modular-based probabilistic fracture mechanics code within a cooperative agreement while properly accounting for the problem uncertainties

• The project team demonstrated that the cooperative management structure was promising, but

d d d l l d b l drecommends a code development leader be selected and the PIB be restructured as an advisory committee

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Pilot Study ResultsPilot Study Results

• Based on the framework code comparison, a costBased on the framework code comparison, a cost analysis, and long term prospects, the xLPR project team recommends that the future versions of xLPR be developed using the GoldSim commercial software as the computational framework

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xLPR Pilot study Final Report

GSxLPR Users SIAMxLPR xLPR Version 1.0 Version 1.0Manual

ML110700017Users Manual

ML110700023Report

ML110660292

Version 1.0 Comparison report

ML111510924

xLPR Version 1.0 Goldsim

Framework ReportML110700019

xLPR Version 1.0 SIAM Framework

ReportML110700026

xLPR Version 1.0 Models/Inputs

ReportBeing published as EPRI report

Includes:D i i f f k Written by Computational groupWritten by SNL

Being published as EPRI report

• Description of framework development

• QA and CM• Pilot study problem and results

S iti it l

Written by Computational group

Written by Models/Inputs group

Written by SNL

Written by ORNL

Written by CNWRA NUREG/EPRI Report• Sensitivity analyses• Code assessment and comparison

with other• Lessons learned

R d ti f f th LPR

Written by CNWRA NUREG/EPRI Report

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• Recommendations for further xLPR development

vg 19

Path ForwardPath Forward

• Project management restructuring - underwayProject management restructuring underway

• Version 2.0 QA program development – underway

• Version 2.0 Model and capability discussions –underway – Focus first on SCC initiationy

• Version 2.0 Model development – Sept 2011

• Version 2.0 Framework implementation – April 2012

• Version 2 0 V&V April 2013• Version 2.0 V&V – April 2013

• Version 2.0 release – End 2013

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