Primary System Corrosion Research (PSCR)
Primary System Corrosion Research(PSCR)TG Lian, EPRINRC – Industry Technical Information Exchange MeetingJune 5-7, 2013. Rockville, MD
Outlines PSCR roles, R&D strategies MDM gaps List of PSCR projects Recently completed projects Selected on-going projects– IASCC CGR data analysis & model development– IASCC study on BOR-60 irradiated materials (EPRI-DOE co-fund)– localized deformation and IASCC mechanistic study– Advanced Radiation Resistant Materials (ARRM) project 2013 Electric Power Research Institute, Inc. All rights reserved.2
PSCR Supports Materials Strategic Objectives PSCR program supports the NEI 03-08 MaterialsInitiative which calls for more proactive managementof materials degradation to enhance safety andreliability Including long-term operation (LTO) Identify component degradation mechanismknowledge gaps Understand degradation mechanisms throughfundamental R&D, and establish technical basis for– developing physically based predictive models– identifying appropriate mitigation, repair or replacement options 2013 Electric Power Research Institute, Inc. All rights reserved.3
PSCR Strategies Perform fundamental R&D to address key degradationissues identified in Material Degradation Matrix (MDM)‒ Irradiation-assisted stress corrosion cracking of stainless steelsand Ni-base alloys in BWR and PWR environments‒ SCC of austenitic stainless steels and Ni-base alloys in BWR andPWR environments‒ Environmental effects on fracture resistance.‒ Environmental effects on fatigue life Collaboration: coordinate PSCR research with thematerials issue programs and stakeholders Leverage: develop alliances with DOE and internationalpartners to leverage research funds 2013 Electric Power Research Institute, Inc. All rights reserved.4
Major Challenges Need for more accurate prediction ofthe occurrence of environmentallyassisted cracking for pressureboundary components:– PWSCC of Ni-based alloys and welds Need for more accurate prediction ofoccurrence of irradiation assistedcracking for reactor internalcomponents:– Cracking of baffle bolts, shrouds, top guides Unavailability of radiation resistantmaterials for repair and replacementof reactor internal components– All current materials crack under irradiation 2013 Electric Power Research Institute, Inc. All rights reserved.5
Key MDM Gaps ‒ PWR Primary System RPV integrity: late occurring damage phenomena and effects onembrittlement trends PWSCC initiation: lack of ability to predict initiation in thick-wallprimary system Ni-based metals & dissimilar-metal welds SCC of stainless steels: factors causing SCC of stainless steels inPWR primary system services IASCC initiation: lack of ability to predict IASCC initiation in reactorinternal fasteners with high fluence Void swelling: need of physically based model to predict void swellingrate and its significance to core structure integrity Effects of high fluence on fatigue life of reactor internals Effects of LTO on performance of high-strength periphery components Long-term performance (PWSCC resistance) of Alloy 690/52/152 Steam generators: ability to predict ODSCC and PWSCC initiation ofAlloy 600TT tubes, to develop effective mitigation strategies 2013 Electric Power Research Institute, Inc. All rights reserved.6
Key MDM Gaps ‒ BWR Primary System RPV integrity: uncertainties regarding the effect of neutron flux onembrittlement rate, most data from PWR or test reactor irradiation LAS SCC: crack initiation in nickel-base alloy vessel ID attachmentwelds and crack extension into irradiated reactor vessel shells IASCC: 1) the possibility of significant crack growth in unaffected basemetal and under low stress conditions; 2) the possibility of an increasein crack growth rates in highly irradiated materials; and 3) fundamentalknowledge regarding the key factors influencing IASCC initiation andgrowth Effects of LTO: 80-year EOL fluence on performance of high-strengthcore periphery components (X-750, X-19 tie rods, beams ) 2013 Electric Power Research Institute, Inc. All rights reserved.7
2013 PSCR Key Projects (1 of 2) Irradiated Materials Testing & IASCC DegradationMechanism Studies––––––Study of compositional effects on IASCC (EPRI-DOE co-funding)APT study of microstructural effects on IASCCCT specimen size and orientation effects on IASCCMechanistic study of localized deformation and IASCC (cause-&-effect)Expert panel on IASCC data compilation & CGR modelDevelopment of IASCC resistant alloys (EPRI-DOE co-funding) SCC of Non-irradiated Stainless Steels and Ni-Base Alloy––––––Japanese POLIM program on SCC mechanisms and prediction modelsOxide film and oxidation kinetics study on Ni-alloys and stainless steelsRole of creep and creep crack growth in EAC of austenitic materialsSCC initiation of Alloy 690 and SCC susceptibility of Ni alloy weldsTheoretical model for SCC/IASCC propagationSCC initiation model for cold worked stainless steels 2013 Electric Power Research Institute, Inc. All rights reserved.8
2013 PSCR Key Projects (2 of 2) Environmental Effects on Fracture Resistance– Fracture resistance of irradiated stainless steel and non-irradiated Ni welds in LWRoperating environments.– Scoping study of low temperature fracture property on thermally aged cast austeniticstainless steels Environmental Fatigue– Mechanistic understanding and modeling of EAF enhancement and retardation inBWR and PWR environments Synergistic Effects in Degradation– Synergetic effects of thermal aging and irradiation aging on degradation of stainlesssteel welds in reactor internals MDM , Materials Information Portal and Materials Handbook– MDM Revision-3 has been published in May 2013 (EPRI Report - 3002000628) 2013 Electric Power Research Institute, Inc. All rights reserved.9
Recently Completed Works PWSCC propagation models for Ni-Alloys Developed more accurate and mechanistically based PWSCCpropagation models for Ni-base alloys and welds in PWRenvironment Ready to be utilized for improvement of MRP-55 and MRP-115disposition curves for PWSCC of Ni-based alloys and welds, andas an input to the xLPR program Investigation of “rapid fracture” phenomenon Resolved one degradation mechanism gap that would potentiallyhave severe impact to safety evaluation The observed degradation was due to mechanical overloading, andwas not caused by the effects of LWR environments 2013 Electric Power Research Institute, Inc. All rights reserved.10
Investigation of Rapid Fracture (completed)To perform studies on the susceptibility to rapid SCC crack advance andcrack instability, and to fully characterize the nature of materials andenvironmental conditions associated to rapid fracture Perform SEM characterization of the final stages of SCC, and initial,middle and final stages of rapid fracture in previously reported rapidfracture samples Evaluate the test conditions of existing rapid-fracture specimensincluding water temperature, dissolved H2 and/or O2 concentration, andrate of change of K Perform control experiments to create an IGSCC crack that grows at amoderate to high rate over sufficient time to allow H permeationthroughout the specimen. Then allow the K to slowly rise versus time todetermine at what K value crack instability occurs. 2013 Electric Power Research Institute, Inc. All rights reserved.11
Common Features in Crack MorphologyAlloy 182 Weld MetalFinal in-air fractureRapid fractureSCC fracture 2013 Electric Power Research Institute, Inc. All rights reserved.12
Previous Data: Exceeding K/size Validity CriterionTo maintain plain strain condition, ASTM standards E399 requires:SpecimenMaterial, ProcessingEnvironmentat Jumpa/Wat JumpK(MPa m)EstimatedExp,hoursB(mm)σf(MPa)C157316L, 50% Forge @ 140C, T-L1580 ppb H2, BWR0.8184.7604212.7680C181316L, 50% Forge @140C, T-L95 ppb H2, BWR0.81126.5392712.7680C192304L, GG, 70% Forge @140C, T-L2000 ppb O2, BWR0.875.9674912.78800.820.371.71C451304, Stock, 17.5% 1D-CR @25C,S-L63 ppb H2 to 2000ppb O2, BWR0.54541.8177512.76503.07C338316L, Tohoku, 600 MPa2000 ppb O2, BWR0.666128.7799125.4650M013800H, 20% Forge, L-T2000 ppb O2, BWR0.7291.3527212.7550C205Alloy 182, T-S95 ppb H2, BWR0.81117.7632512.7500C276Alloy 182, T-S2000 ppb O2, BWR0.8101.2591412.7500C435Wrot A182, 22% 1D-CR, L-T3124 ppb H2, PWR0.913302.5441812.7550C290Alloy 182, T-S2000 ppb O2, BWR0.725127.6504025.4500C160A182, 10% Forge @ 25C, T-S/T-L2000 ppb O2, BWR0.53149.61217825.4550C403Alloy 182, T-S63 ppb H2, BWR0.746104.51349125.4500C407Alloy 82, T-S2000 ppb O2, 340.580.54C422Alloy 82, T-S63 ppb H2 to 2000ppb O2, BWR0.69885.81100825.45000.86 2013 Electric Power Research Institute, Inc. All rights reserved.13
Investigate Rapid Fracture -- Controlled Tests In pure waters with various DO/DH at 288 C Increase K during the test to moderate/high stressintensity factors, or use slowly rising K/load (e.g.,increasing by 30 MPa m over several weeks). Exposure times should be sufficient to allow hydrogenpermeation throughout the metal Try to achieve or maintain a high crack growth rate, sothat the crack remains sharp as the K changes. Highgrowth rates tend to occur at– high K– high corrosion potential– high water impurity level Additional tests in air with similar loading conditions 2013 Electric Power Research Institute, Inc. All rights reserved.14
Controlled Tests: “Rapid Fracture” Observedin Water at 288 CMaterialEnvironmentVariablesLoadingProfilea/W atJumpAt JumpK(MPa m)EstimatedB(mm)σf(MPa)EPRI 182(C552, 0.5T CT)63ppb H2Load ramp at0.002 lbs/s0.61282.512.7EPRI 182(C551, 0.5T CT)1580ppb H2Load ramp at0.002 lbs/s0.6682.512.73EPRI 182(C573, 0.5T CT)2ppm O2Load ramp at0.002 lbs/s0.65361.612.73EPRI 182(C578, 0.5T CT)63ppb H2Load ramp at 0.02lbs/s0.6027712.7BHK JOG 82(C538, 0.5T CT)H2 O2 mixture with Hexcess coolant conditionLoad ramp at0.002 lbs/s0.53689.112.75000.399IHI JOG 182(C536, 0.5T CT)H2 O2 mixture with Hexcess coolant conditionIncreasing DCPDerror duringconstant load0.7276612.75000.729GE 304SS, 17.5%cold-rolled(C537, 0.5T CT)H2 O2 mixture with Hexcess coolant conditionLoad ramp at0.002 lbs/s0.58350.612.76502.294 2013 Electric Power Research Institute, Inc. All rights reserved.155005005005000.4670.4680.8390.536
Specimen Size Effect: 1T vs. 0.5TThe increase of size can markedly increase the sudden fracture K,which may suggest the instability of 0.5T CT.1T CT A182 Weld Metal0.5T CT EPRI A182 Weld Metal14.814.60.20Sudden Fracture@1517h-0.2actual K 82.5 MPa mafter post-correction-0.43135 ksi in No CyclingContinue at 63 ppb H2320.430290.20.10-0.1-0.21.2 x 10-6mm/s-0.3CT Potential3 x 10-8mm/s-0.4CT Potential-0.5Pt Potential-0.6Pt Potential2614.21413550.3Sudden Fractureat 143 MPa m282714.4Outlet ConductivityC552 - 0.5T CT of Alloy 182, T-S, 63ppb H2,288 C13751395141514351455147514951515C596 - 1T CT of Alloy 182, T-S, 35 ksi in,63ppb H2, 30 ppb SO42-, 288 C-0.81535253000Time, hours 2013 Electric Power Research Institute, Inc. All rights reserved.-0.7320034003600380040004200Time, hoursFailed at K 143 MPa mFailed at K 82.5 MPa m16-0.6Potential, Vshe or Conductivity, µS/cm15Outlet Conductivity0.4Start Load Ramp to 18000 lbs@ 3286h15.233Crack length, mmCrack length, mm15.4SCC#5 of c596 - Alloy 182, T-S, Rapid Fracture0.6Potential, Vshe or Conductivity, µS/cm15.6Stop Constant K, Start Load Ramp @ 1401h15.8Continue at Constnat K 38.5 MPa m, No CyclingContinue at (4%H2 96%N2)SCC#3 of C552fix - Alloy 182, T-S, Rapid Fracture16
Similar Rapid Fracture Observed in Air !!!0.5T CT GE Stock 304 SS with17.5% Cold Work, in Air0.5T CT EPRI 182 Weld MetalIn Air2.8 x 10-6mm/sactual K 59MPa m14.914.8914.8814.87-5.4 xmm/s10-914.8614.32.2 x 10-7mm/s8.4 x 10-9mm/s1.3 x 10-7mm/sSudden Fracture@695hactual K 53 MPa mafter postcorrection14.85C586 - 0.5T CT of Alloy 182, T-S,38.5 MPa m, In Air, 288 C14.2800820840860880900920940960C595 - 0.5T CT of 304SS, 17.5%CR@25C, S-LK 38.5 MPa m, Air, 288 C14.849805501000570590610630650670Time, hoursTime, hoursFailed at K 53 MPa mFailed at K 59 MPa m(Load Ramp at 0.002 lbs/s) 2013 Electric Power Research Institute, Inc. All rights reserved.17690Potential, Vshe or Conductivity, µS/cm14.91Start Load Ramp at 0.002 lbs/s @ 650h14.92To Constant K 38.5 MPa m, No Cycling @ 630h14.414.93actual K 70.4MPa mafter post-correctionCrack length, mm14.5Sudden Fracture@983hContinue at 38.5 MPa m, R 0.6, 0.001 Hz, No Hold TimeConstant K 35ksi in, No Cycling @ 836hStart Load Ramp from 1398 lbs to 5500 lbsat 0.002 lbs/s@ 844hCrack length, mm14.6R 0.6, 0.001 Hz, 9000s hold14.714.94To 38.5 MPa m, R 0.6, 0.001 Hz, 9000s hold @ 622hSCC#3 of c595 - 304SS, S-L, Rapid FractureSCC#2 of c586 - EPRI 182, T-S, Rapid Fracture14.8
Summary of Rapid Fracture InvestigationThis investigation has concluded that the reported “rapid fracture”phenomenon is not induced by LWR environments The calculation from both ASTM linear elastic criteria and limit loadanalysis suggest that rapid fracture mostly happened when the loadis beyond the limit for CT specimen. 2013 Electric Power Research Institute, Inc. All rights reserved.18
IASCC CGR Data Compilation & Analysis Task 1: Collect and compile results of crack growth tests from: CIR-fast reactor irradiated materials Halden-LWR irradiated materials & in-reactor tests BWRVIP-BWR irradiated materials MRP-PWR irradiated materials Literature data (ANL NUREG reports, JNES reports) Task 2: Convene an Expert Panel to review, screen and categorize theavailable data using consensus screening criteria. The panel includessome of the investigators who generated the data as well selectedindustry experts and vendors. Task 3:The Expert Panel uses the screened data to develop andrecommend appropriate crack growth models and disposition curvesfor irradiated stainless steels in BWR and PWR environments. Thefinal report will be issued after review by PSCR, MRP and BWRVIP. 2013 Electric Power Research Institute, Inc. All rights reserved.19
IASCC CGR Data Screening Criteria Review original a vs. t curves for each test segment (rawdata is a must) Stress Intensity (K) validity for irradiated materials vs. ASTME 399 and alternative criteria Crack extension (da) Test segment interval (dt) Variation of K with crack length dK/da Constant load or K vs. partial unloading Load ratio (R) Correlation coefficient on the linear fit to crack growth rateover a given test segment The consensus was that criteria should not be appliedindividually without considering the entire context of the test 2013 Electric Power Research Institute, Inc. All rights reserved.20
IASCC Data Ranking The database includes more than 1600 testsegments including those under cyclic loading For IASCC crack growth rates only test segmentsunder constant load or periodic partial unloadingwere considered The reviewers have ranked the test segments ona scale of 1 (best) to 5 (worst) after examining theraw data from crack length vs. time plots Data ranked from 1 to 3 was considered suitablefor development for models for BWR NWC, HWCand PWR environments 2013 Electric Power Research Institute, Inc. All rights reserved.21
IASCC CGR: Low- and High-ECP Models The models account for effects of dose, stress intensity K, ECP,temperature, type of loading (constant load vs. PPU) There was no significant difference in the CGRs between BOR 60 andLWR irradiated materials after accounting for the above factors The CGRs under PPU were approximately 2X higher than underconstant load Analysis showed that common model can be used for BWR-HWC andPWR environments with a temperature term to account for higherPWR temperatures After accounting for these parameters there is still a significant heat toheat (or specimen to specimen variability) that is not understood This variability is reflected in heat coefficients or specimenscoefficients in the models 2013 Electric Power Research Institute, Inc. All rights reserved.22
IASCC Data Analysis – Next Step Work with the Expert Panel to produce and document the finalconsensus PWR and BWR IASCC models from the extensive IASCCdatabase that was compiled and ranked by the Expert Panel in earlierphases of this Project A revised version of the draft report on the IASCC database and bothlow ECP (PWR and HWC) and high ECP (NWC) IASCC models,incorporating all revisions requested by the Expert Panel and EPRIreviewers will be prepared by November 2013 The draft report will be sent to PSCR, MRP and BWRVIP inDecember 2013 for review Final report will be published in the second quarter of 2014 aftercomment resolution The report will provide the technical basis for crack growth dispositioncurves for irradiated BWR and PWR stainless steel internals 2013 Electric Power Research Institute, Inc. All rights reserved.23
Identification of Key Factors Affecting IASCC(EPRI-DOE co-fund) Tailored Alloys with solute addition: Alloys E, F, G, H, I, K, L, M, N, P––Alloy E is a reference alloy of high purity 304LAlloys A, B, C and SW are various commercial grade austenitic stainless 0230.01519.9510.80.530.072 .0130.00716.7712.782.180.008 0.010.380.0040.10.06SW0.0221.070.240.015 0.00218.4210.45E0.0210.940.04 0.010.00318.7612.370.040.00030.0050.010.0040.01 0.01F0.0080.980.03 0.010.00318.1712.060.020.00050.0020.010.0130.01 0.01G0.020.970.03 1H0.021.011.05 0.010.00218.1712.450.020.0005 0.0010.010.0070.01 0.01I0.0071.010.030.0160.00318.2112.110.020.0004 0.0010.010.0120.01 0.01K0.0210.03 0.010.00218.2125.080.020.0005 0.0010.010.0030.01 0.01L0.021.020.03 0.010.00225.2225.070.020.0005 0.0010.010.0090.010.01M0.0210.03 0.010.00318.0311.220.020.0005 0.0010.30.0110.73 0.01N0.0210.03 0.010.00318.2412.120.020.00040.5950.010.0040.01 0.01P0.0281.010.10.010.00717.0313.62.18 2013 Electric Power Research Institute, Inc. All rights reserved.24Hf0.0251.17
CIR database20 CGR expts.This programCERT of protonIrradiatedsamples6 CGR expts.32 CERT expts.Microstructure ofproton and neutronirrad. samples Role of solutes in IASCC crack propagation, and in crack initiation Role of starting microstructure in crack propagation and in crack initiation Effectiveness of proton irradiation in predicting relative CGR behavior Comparison of crack initiation following proton and neutron irradiation Comparison of crack initiation and crack growth in neutron-irradiated samples as afunction of solute addition or starting microstructure Structure-property relationship for neutron irradiated alloys Effect of alloy, alloy purity, heat and dose on crack growth and crack initiation 2013 Electric Power Research Institute, Inc. All rights reserved.25
Preliminary Results IASCC susceptibility of neutron irradiated alloys determined by CERTin 288ºC BWR NWC follows order:KS LS B ES GS PS HS Proton irradiated alloys tested under similar conditions show thesame trend in IASCC susceptibility:KS LS ES GS HS Crack initiation and growth may depend on different variables. CGRresults show that for alloys ES, PS, HS, and LS:– Factors causing differences in initiation did not cause significantdifferences in growth rate– CGR data are limited at comparable K 2013 Electric Power Research Institute, Inc. All rights reserved.26
Cause-&-Effect Relationship between LocalizedDeformation and IASCC (with DOE collaboration)It is well known that IASCC is a combination of GB characteristics and environment.However, their relative contributions to cracking have yet to be understood.Establish direct evidence of a cause-and-effect relationship Site-specific approach to confirm whether an IASCC crack can beinitiated at a pre-characterized siteDirect measurement approach to determine the degree of localizeddeformation at the cr
TG Lian, EPRI . NRC – Industry Technical Information Exchange Meeting . June 5-7, 2013. Rockville, MD . Primary System Corrosion Research (PSCR)
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