Stress Corrosion Cracking - Nuclear Regulatory Commission · Stress Corrosion Cracking Presented...
Transcript of Stress Corrosion Cracking - Nuclear Regulatory Commission · Stress Corrosion Cracking Presented...
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YUCCA MOUNTAIN PROJECT
U.S. Department of EnergyOffice of Civilian Radioactive Waste Management
Stress Corrosion Cracking
Presented to:Waste Package Materials Performance Peer Review Panel
Presented by:Gerald GordonSenior Staff ScientistEngineered S se s--Framnatome Acja ncqed J.Nuc" 6J c~tI V~-ifd-SAI1,C QQmpag -LLGCMivian-Radiac iveW ItSst~r M
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Overview of Project Approach to MitigatePotential for Stress Corrosion Cracking (SCC)
Project test results indicate Alloy 22 is highly resistant, but notimmune to SCC in concentrated brine environments
- Ti Grade 7 has lower SCC resistance- Under waste package stress state conditions (no cycling), SCC
very unlikely to initiate and/or growIf cracks were to initiate, growth rate measurements indicatethey could grow through-wall in several thousand years if SCCconditions persisted
* If SCC could generate through-wall cracks, finite elementanalysis of bounding residual stress patterns at waste packageclosure welds and drip shields damaged by rock drops indicatethey would be short and very tight
- Any radionuclide transport through these cracks would bediffusion limited
- For Ti Grade 7 drip shield, limited length through-wall SCC doesnot compromise component performance
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Overview of Project Approach to MitigatePotential for Stress Corrosion Cracking
(continued)
* The Project has conservatively adopted an approach to mitigate SCCpotential by removing near-surface tensile stresses on entire wastepackage
- Applied tensile stresses are limited to
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Overview of Project Approach to Mitigate StressCorrosion Cracking (SCC) Potential
(continued)
* Solution Annealing of as-fabricated waste package- Finite element modeling (FEM) used to optimize solution annealing
process to produce compressive stresses on outer surfaces* Process utilizes controlled quench rate (consistent with avoiding
TCP phase formation) following heat up to solution annealingtemperature
Temperature difference between the outer surface and the mid-wallthickness should be minimized to reduce residual stresses (Z. Ceylan,"Minimization of Residual Stresses in WP Mock-up due to Solution Annealing' Nickel Development InstituteWorkshop, Las Vegas, NV, October 17-18, 2000)
* Stress measurements on annealed waste package mockup confirmexpected surface compressive stresses
Comparison of Experimental Test Results with FEM ResultsHoop Stress (ksi)
_ _ _ _ Mi dle Bo tomTest Results FEM Results Test Results FEM Results Test Results FEM Results
(2 nodes) (2 nodes) (5 nodes)Location# 1 -51 -57 -81 -49 -51 -46
-34 -49 -36-34-38-49
Location # 2 -43 -56 -37 -48 -47 -45Location # 3 41 -34 -46 -48 -44 -35Location # 4 -45 -46 -38 -34
-37-48
Average -45 -45 -53 -49 -45 A0Difference 0% 8% 11 %
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Alloy 22 Waste Package Mockup:Solution Anneal and Water Quench
I~~~~~~~~~ is
Full-scale diameter, Quarter-scale Length
* Solution Anneal Temperature: 1150 0C
* Quenching from outer surface results in surfacecompression
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Overview of Project Approach to Mitigate SCC(continued)
Local Induction AnnealingTraversing . 1-Vinductioncoil
Closure -A--weld region* FEM also used to optimize
outer closure lid weldgeometry for inductionannealing ~-
I I
I i
-LL- ').WE
Measurements on annealedclosure weld planar mockupconfirm expected 2 5 mmcompressive surface stresslayer (0
0
-5
-10
-15
-20
-25
-30
-35
-40
-45
-50
Typical Induction Annealed Closure W(Stress Distribution on Planar Mockup
* .
N.-
.~~~ I
,ld
* Full diameter short and 1/4length mockups currently alannealing shop awaitingproof of concept testing
I
0 0.05 0.1 0.15 0.2
Depth below surface (inches)
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Closure Weld Mockups at Ajax(Awaiting Induction Annealing)
62.13 - 1.20_ - 2.19 0.50
1,00 - 0 25
3 3 _4 0 V I01.06 0.25
10.47 -tSECTI2N F LID _- 29
9jax ̂ 0DWG: SH-29-OOOS SEoARATE Bay$g u rx.4-Q -- MUa&s nC*- DATE! 10/29/01 APPR. JGT
WARREN. OH. BY: CES SCALE 1=12
Short-ring Mockup One-quarter Length Mockup
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Post-Annealing Evaluation Plans
* To assure solution annealing and inductionannealing processes do not unduly degradecorrosion resistance in weld regions
- annealed mockups will be sectioned and evaluated alongand through the weld regions as well as in the fillet weldareas including
* metallurgical structure to establish any effects on TCP phasesor ordering
* post-annealing corrosion resistance by electrochemicalpolarization testing
In addition, detailed residual stress measurementswill be compared with ANSYS Model calculations
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Waste Package SCC Model PredictionsTwo SCC Models evaluated in AMRIPMR
- A. Threshold Stress Intensity (Kiscc) Model:
* If K, > KIscc, crack growth can occur at existing defects- B. Slip-dissolution Model:
* Crack growth rate, V = f(n)[scjnwhere n = f(material,environment) and soct = crack tip strain rate
* Model initially developed for stainless steelsfor which f(n) = 7.8 x 104(n)3 6 and sect = 4 x 10-14 (K)4(for constant load) - 10 t
* For a given n value, V a (K 1) 4 n l\
* Model later adapted to nickel base alloys m ,2(Andresen et at, "Stress Corrosion Crack Growth RateBehavior of Ni Alloys 182 and 600 in High Temperature 1 iWater", Corrosion/02, Paper 02510, NACE 2002) 3
- Alloy 22 specific values now available Oxi E IeM nuEPRACTURE t
* For smooth surfaces away from welds |'n' obtained from film rupture tests. If stress < threshold stress, V = 0 or fit to growth rate data
* In region of welds, model currently utilizes weld flaw distribution based onstainless steel welds as used in RR-PRODIGAL code
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Weld Flaw Distribution ProgramAn Alloy 22 specific flawcharacterization programunderway
* Sixteen Full-diameter Rings- Duplicates the Outer Barrier Final
Closure Weld Geometry and WeldProcess
* ATIG Process* Remotely Welded
NDE- Ultrasonics- Radiographic Testing- Eddy Current- Dye Penetrant
X-Ray diffraction for stressesMetallographic and corrosionresponse characterization plainned
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Growth of SCC in Pre-cracked Alloy 22* Cracks formed at defects under cyclic loading can
continue to grow under constant load for short periodsSCC#3ma of c163 -Alloy 22 + 20% Cold Work
Crack growth vs time for20% cold-worked Alloy 22 in110°C BSW (monitored withreversing DC method)
110
E
EC
30
a
.108 0£
-106 EIE
-104 1!Alloy 22 in 11O°C BSW
* 102Moving average of10 crack length &temperature data
|SCC of c163 -Alloy 22 + 20% CW, 110C|130 MPa4m, Air sat'd, -Satd Chemistry
100
98
2000 2500 3000 3500
Time, hours4000 4500 Woo0
Summarv of measured crack growth rates for K, = 45 MPa.m1 /2Conditions Approximate Maximum Approximate Maximum
CGR at CGR at Constant LoadR = 0.7 and 0.001 Hz
BSW -110 0C 2-3 x 10-" m/s 3 x 10-3 m/sSAW - 950C 2-3 x 10-"n m/s 2 x 10-13 m/sSCW - 950C 3 x 10-" m/s 5 x 10-13 m/s
13X 1013 M/S is ~Io mm in 1000 years. YUCCA MOUNTAIN PROJECT
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Comparison of Recent Crack Growth RateResults in 1 1 0C BSW with Various
Calculated Film Rupture Model 'n' ValuesI.E-06
1.E-07
EC; 1.E-08
d..
.0
C.,
I.E-10
I.E-11l
Higher growth rates correspond tocontinuous cycling at R-0.7, 0.001 Hz;lower rates are for longer hold timesat K.. & (sometimes) at constant load
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F:U
n =
Calculated statsteel curves fo0.8 and I
/1 / 2
All specimens in this
nless group tested at 30 MPa/mU
Stress Corrosion Crack GrowthPredicted curve using Tests in 110 C Concentrated Groundn = 1.0 & adjusted f(n) Water (Na / K / Si I Cl I S04 / F I C0 3 )for alloy 22
.. . . . . . . . . . . . . . . . . . . . . . . . . .
0 10 20 30 40 50 60
Stress Intensity, ksilin
Exponent 'n' values for Alloy 22 Ž 1
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Approach to Obtain Conservative AlloyKIscc Estimate
22
Cyclic load rate
Constant load rate
'I*EE
0
U9
0.1 1 10 100
Stress Intensity, MPa/m
Extrapolation of constant load SCC growth rate to corrosionrate -> blunting yields conservative KSCC values of ow1 2 MPa/m
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Concept for Threshold Stress for SCC
No C22 failures at high a -*
Stress \I Typical material
response
l $|Low ath justified for C22
Hours to failure
* No constant load failures of Alloy 22 to date at < 2.2 yield* ASME code uses 2X safety factor on stress based on high
frequency air data* YMP environment is highly static
*. Defensible to use a th ~ 3X below failures (~75% yield)
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Summary of Recent SCCExperimental Program Results
Extensive laboratory SCC tests over a range ofstresses, metallurgical conditions and YMP relevantenvironments indicate Alloy 22 highly resistant tocrack initiation
- Titanium Grade 7 is less resistant
* SCC initiation tests performed include:- Constant load (CL) tests in 1O0'C BSW out to >4500 hours
- U-bend tests in Long Term Corrosion Test Facility out to 4yrs
- Slow strain rate tests (SSRT) over a range of environments,applied potentials and temperatures
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Constant Load and U-Bend Test ResultsNo Alloy 22 SCC failures at stresses < 2.2 yield strength out to 4 year4Ti Grade 7 fails at -1.1 yield strength in shorter times
3.0
e 2.5
*aC0
C) 2.0
U) 1.5U)
~0
O 1.0
._
0.5
0.0
0.00
Constant Load Specimens in Concentrated J-13 Brine Solution)XYMPA-22-NoSCC (105 0C, pH=12.2) outto 4500 hours
XYMP Crev. A-22 - No SCC U-bend Specimens in SAW, SDW and SCW at 60, 900C. YMP Weld A-22 - No IGSCC
*YMP Ti Gr 7 - SCC Alloy 22 Ultimate Tensile Strength* YMP Crev Ti Gr 7 SCC _ ....
Jo YMP A-22 U-bends - No SCC * )KKM U
* :
:-R Range of- :-U1 Id >K Alloy 22 :
wil w El *1E3 : by Results_______________ w/o SCC
Ti Grade 7 SCC Failures
Alloy 22 specimens tested include thermally aged YMP = Concentrated salts 105 Cconditions to produce TCP and LRO YMP U-bends 60 - 90 C
1 0.010 0.100 1.000 10.000 100.000
Failure Time, years
Results provide basis to increase Alloy 22 threshold stress from10-40%6 to '40 ield stress
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Slow Strain Rate (SSRT) Test System
Condenser - -- =
ReferenceElectrode
Counter ecimenElectrode
I-U
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SSRT Results Summary for Mill Annealed Alloy 22 at 1.6 x 10-6 S-1Sam- Environment T Ecor E Time to Max RA Observationspie C) Applied Failure Stress (%)
-i - (hi) (MPa)
012 Air 2 N/A N/A 124 786 74 Inert
123 4MNaCIpH-6 8 -323 +350 127 758 80 No SCC
004 SaturatedCaCl 2(-17m),pH -6 20 -140to-180 E. 127 752 71 NoSCC
013 1% PbCI2, pH -4 95 - E. 126 765 72 No SCC
015 SAW,pH3 - 3 -7to+360 E. 118 758 79 NoSCC016 SAW+0.005%Pb(NO 3 )2 ,pH-3 6 -6to+370 Er 124 772 74 No SCC017 SAW+0.005%Pb(N0 3 )2 ,pH-3 16 Oto+350 Ecoff 125 772 74 NoSCC003 SAW+0.005%Pb(NO 3 )2 ,pH-3 15 -90to+400 E. 118 752 85 No SCC
127 1 BSW-[NO3-+SO41,pH 13(1) 8 -240to-220 Ea 123 745 72 No SCC124 1 BSW-1NO3-+SO4-,pH -13 S -330 +100 120 745 78 No SCC122 BSW-N3-N+SO4 ,pH-13 8 -245 +200 122 752 72 NoSCC119 IBSW,pH- 13 5 -301 +400 118 745 75 No SCC120 BSW, pH -13 5 -323 +400 99 745 74 No SCC
115 BSW-NO3-, pH - 13 5 -335 +400 115 752 77 No SCC129 BSW-SO4 ,pH -13 05 -314 +400 119 731 82 NoSCC
125 SSW,pH-6 00° -154 +400 113 717 71 NoSCC
112 SCW,pH-9 73 -94 +400 91 696 71 SCC020 SCW,pH- 9 2 -109 +400 116 800 85 NoSCC030 SCW,pH-9 13 -182 -300 98 NA 65 SCC
021 1 SCW,pH-9 -171 +400 90 662 64 SCC026 SCW,pH -9 1 -241 +100 120 111 79 NoSCC
* No SCC at Ecorr and above over a broad range of environmCaCI 2, 1% PbCI 2, SAW + Pb(NO3) 2 , BSW and SSW)
* In SCW at very oxidizing potentials, +300 to 400 mV (SSC),SCC can occur at high strain levels
ants (4M NaCI, Saturated
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SSRT, MA Alloy 22,1.6 x 10-6 S-1
800 - ' " I ' I_ i '* Testing at +400 mV [SSC]-100
+ : .~~~ For BSW and SSW600 - -------------- --ff- T-----t------------ Fo BS an S W
80 Solutions at 105°C and400 - ------------- -- _ 60 1000C, Elongation to Failure
4 L i~llo y2 2 _ 40 Similar to Elongation to200 400 mrV-SSC 20 Failure in Air
, B BSW-105°C Eg20e -SCW-73'2__j*For SCW, Elongation to
0 - ';20 40 60 80 Failure was ~30% ShorterElongation (%) than in Air
SCW, 730C, + 400 mV [SSC]X 30 X 300
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Potential vs pH Region Where SCCInitiation Observed in SSRT
500
400
300
-. 200
(nL-. 1 00
E-I
..,,,o
0"I
-x
x
-.-- I X ---- II I
I 4 _Region where% I Cr
observed todate I
IIIII
Approximate upper sbound of measuredEcorr values
* Ecorr/Pb* Ecorr/NoPbA Eapp/Pb
Eapp/SCCX Eapp/NoPbt I
-100
-200 -
-300
I U 7
I ~..
-4000 2 A
SAW
4 6
CtCl2y
SSW
8 +SCW
10 1 2 412BSW 14
pH
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Hydrogen Induced Cracking (HIC) of Alloy 22 not expected* Literature* indicates Ni-Cr-Mo Alloys like Alloy 22 highly resistant to HIC in the
annealed condition
- Susceptibility can develop with heavy cold-work, galvanic coupling to lessnoble metals, aging and segregation, reduced sulfur species
* For waste package, compressive surface stresses, annealed structure from SCCmitigation and resistance to aging also beneficial
* Slow Strain Rate Tests performed by LLNL on Alloy 22 at cathodic potentials(Ecorr - 500 mV or - 630 mVssc ) showed no evidence of HIC
SSRT Curves for Alloy 22 in 5% NaCI, pH 2.7, 900C7 Strain rate of 3.3 x 1 0 6 s-1
900
800
700
600
500
400
300
200
100
00 0.1 0.2 0.3 0.4 0.5 0.6
Deflection (in)
0.7
*G.E. Gdowski, "Survey of Degradation Modes of Four Ni-Cr-Ml
**A.K. Roy, et al, "Stress Corrosion Cracking of Ni-Base and TiProceedings, Seventh International Conference on Nuclear EnC
o Alloys, UCRL-ID-108330, March, 1991, p61
Alloys Under Controlled Potential",lineering, Tokyo, Japan, April 19-23,1999
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Summary* Alloy 22 highly resistant but not immune to SCC
- Ti Grade 7 less resistant
* Evaluation of Pb additions in relevant environmentsindicates no deleterious SCC effect
* If SCC were to occur, tight cracks formed would limitaqueous transport processes and structural damage
* Although SCC in waste package highly unlikely,Project mitigating SCC potential
- Waste package designed to limit applied tensile stressesbelow threshold value
- Near-surface residual tensile stresses mitigated throughspecial processing
* Shop solution heat treatment* Hot cell induction annealing and laser peening
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Backups
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Resolution and Accuracy of SCC Data
EE
h.'
C.)
120
118
116
114
112 0i
110 E!C)
E108 g
106
104
102
22.9605 la I"' I -' - 2 . . . . I . . . . I . . . . . i . . . . a . . . I I . . . . 1004800 5000 5200 5400 5600 5800 6000 6200 6400 6600 6800
Time, hours
"Smooth" data at < 10-9 mm/s challenging - resolution < 1 jim
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Resolution and Accuracy of SCC Data(Continued)
* Crack monitoring by reversing dc potential drop:
- crack length resolution of . 1 ,tm
- likely the lowest growth rates ever measured
- crack length accuracy typically within 10 - 20%
* for 3 CT specimens on this project: 1.5%, 10%, 22%*
- corrections of < 30 - 50% have little effect on data quality
- small crack increment justifiable because (even) crackfront samples a wide cross-section of microstructure
* This CT had an unusual problem with dc potential probe leads; re-attachmentcan produce an error- this probably contributed
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U-bends Examined after Exposure in LLNLLong Term Corrosion Test Facility
Testing SAW, SAW, SCW, SCW, SDW, SDW,Time 600C 900C 600C 900C 600C 900C
(months)6 3L,3v, 3L, 3v 3L,3v, 3L,3v, 1L, 1V, 1L, 1V,
3WL,3wv 3WL,3wv 3WL,3wv 1WL, 1Lwv 2WL,2wv12 3L,3v, 3L,3v 3L,3v, 3L,3v, 1L, 1V, 1L, 1V,
3WL,3wv 1WL,3wv 3WL,3wv 1WL, 1wv 2WL,2wv24 3L,3L27 1L, 1V,
1WL, 1WV28 3L,3v, 1L,1V,
1WL,1WV 1WL,1WV29 3L,3v, 3L,3v,
1WL, 1WV48 1WL,1WV
2L
Total 30 22 30 35 12 16Samples
No SCC initiation observed out to 4 years exposure in range ofrelevant environments
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Sketch of Notched Constant LoadTensile Specimens
Notched Keno Specimen Geometry
2.25 (+.00, -.05)
0.8125 0.625(+/- .01) (+/- .02) 0.5 R Typical
- -- ~~~~~0.200 0.200---
Thread 112 -20 D = Gage Section DiameterBoth Ends
U-shape Notch Details
r = 0.010D d ~~h =0.038
0= 0.318d 0.242
A series of sharply notched specimens currently under test _to evaluate effect of potential surface defects on SCC
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Welded Alloy 22 Constant LoadSpecimens before Notching
-- - T; I
a
EMM,�44*14'w *I%- - - -- E�Q � --- - -z ---
fIN' mg-i
"Iff ~ I-.-- EliU U 001 0- �3 ENAMR Mm� �A1
bm M uk
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