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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

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

YUCCA MOUNTAIN PROJECTBSC Presentations._WP Peer Review YMGordon_0318-1902.ppt 2

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

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 %

YUCCA MOUNTAIN PROJECTiBSC Presentations._WP Peer Review _YMGordon_0318-1902.ppt 4

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

=ns YUCCA MOUNTAIN PROJECTBSC Presentations_WP Peer Review _YMGordonO3l 8-1902.ppt 5

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)

_ YUCCA MOUNTAIN PROJECTBSC PresentationsWP Peer Review _YMGordon 0318-1902.ppt 6

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

YUCCA MOUNTAIN PROJECTBSC PresentationsWP Peer Review _YMGordonn_031 8-1902.ppt 7

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

YUCCA MOUNTAIN PROJECTBSC PresentationsWP Peer Review _YMGordon_0318-1902.ppt 8

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

Exxon YUCCA MOUNTAIN PROJECTBSC PresentationsWP Peer Review _YMGordon_0318-1902.ppt 9

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

- - YUCCA MOUNTAIN PROJECT

BSC Presentations._WP Peer Review ._YMGordon_0318-1902.ppt 10

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

BSC PresentationsWP Peer Review _.YMGordon_031 8-1 902.ppt 11

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

I-

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

YUCCA MOUNTAIN PROJECT)2.ppt 12BSC PresentationsWP Peer Review -YMGordon_0318-19(

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

- YUCCA MOUNTAIN PROJECTBSC PresentationsWP Peer Review YMGordon 0318-1 902.ppt 13

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)

YUCCA MOUNTAIN PROJECTBSC Presentations_WP Peer Review .YMGordon 3l1 902.ppt 14

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

rsttn e ReYUCCA MOUNTAIN PROJECTBSC PresentationsWP Peer ReviewYMGordon 0318-1902.ppt 15

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

- .. > .. t. _ YUCCA MOUNTAIN PROJECTBSC PresentationsWP Peer Review _YMGordon 0318-1902.ppt 16

Slow Strain Rate (SSRT) Test System

Condenser - -- =

ReferenceElectrode

Counter ecimenElectrode

I-U

YUCCA MOUN PROJECTBSC Presentationsj.NP Peer Review _YMGordonr0318-1902.ppt 17

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

mmmm YUCCA MOUNTAIN PROJECT= .. sBSC PresentationsWP Peer Review _YMGordon_0318-1 902.ppt 18

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

YUCCA MOUNTAIN PROJECTBSC Presentations-WP Peer Review -YMGordonQ318-1902.ppt 19

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

BSC PresentationsWP Peer Review _YMGordon_0318-191YUCCA MOUNTAIN PROJECT)2.ppt 20

@ /

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

YUCCA MOUNTAIN PROJECTBSC PresentationsWP Peer Review _YMGordon_0318-1902.ppt 21

d t 2-

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

* YUCCA MOUNTAIN PROJECTBSC Presentations WP Peer Review _YMGordon_031 8-1 902.ppt 22

Backups

YUCCA MOUNTAIN PROJECTBSC Presentations WP Peer Review _YMGordon 0318-1902.ppt 23

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

YUCCA MOUNTAIN PROJECT

BSC PresentationsWP Peer Review YMGordon_0318-1902.ppt 24

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

YUCCA MOUNTAIN PROJECTBSC Presentations WP Peer ReviewYMGordon_031 1902.ppt 25

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

YUCCA MOUNTAIN PROJECTBSC PresentationsWP Peer Review yMGordon_0318-21902.ppt 26

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

YUCCA MOUNTAIN PROJECTBSC Presentations WP Peer Review _.YMGordon.031 8-1902.ppt 27

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

YUCCA MOUNTAIN PROJECT

BSC PresentationsWP Peer Review _YMGordon_0318-1902.ppt 28