PWSCC of Alloy 690 and Weld Metals - NRC: Home Page · 2013. 6. 13. · SCC#2a - c585 - 690, CRDM WQ199, As -Rec'd, 15% Forge, S-L. Outlet conductivity x 0.01 Pt potential CT potential

Al Ahluwalia EPRI MRP

NRC/Industry Meeting

June 5-7, 2013 Rockville, MD

PWSCC of Alloy 690 and Weld Metals

2 © 2013 Electric Power Research Institute, Inc. All rights reserved.

Background

• In 2006, Bettis identified high CGRs (~10XE-07mm/s) for cold worked Alloy 690; about the same as for Alloy 600 (MRP-55)

•Assembled an Expert Panel and an International collaboration to

guide and conduct complementary and confirmatory research

•Monitoring of research by expert panel

•Use of well-established test procedures and characterized materials; many using materials from a central inventory

•Members include EPRI, NRC RES, Bettis/KAPL, EDF/MAI, UNESA, KAERI, MHI, Tohoku Univ. and many others

•Reviewed state of knowledge in 2008 (MRP-237, Rev.1); agreed to eleven knowledge gaps (next slide); an update of research published in 2013 (MRP-237, Rev. 2))


Alloy 690 PWSCC Knowledge Gaps

1. PWSCC susceptibility of HAZ (H) 2. Effect of weld defects in 52(M)/152 on PWSCC susceptibility (H) 3. Effect of weld composition & welding procedure (including dilution effects) on

PWSCC and LTCP (H) 4. Welding fabrication and repair effects on defect population, residual stresses

and susceptibility (H) 5. Reduced resistance to PWSCC due to thermo-mechanical processing of A690

(e.g. 1-D rolling) (M-H) 6. Resolution of contradictory CGR findings among labs for 52(M)/152 (M-H) 7. Relevance of thermo-processing modes (e.g. 1-D rolling) to plant installations

(M-H) 8. Importance of LTCP to operating plants for A690 and welds (M) 9. CGR flaw disposition curves for A690/52/152 (M) 10. Detailed information on actual replacement components in the field (L-M) 11. Crack initiation data on heterogeneously deformed A690 that has shown high

CGR Values(L-M)


EPRI Alloy 690/52/152 PWSCC Program Issue Statement

• Alloys 690/52/152 very resistant to PWSCC; however, PWSCC-related

issues remain: – PWSCC vulnerability for material with abnormal microstructure,

specific product forms, and to thermo-mechanical processing that could be present in the HAZ

– A52 fabrication defects could become a factor in initiation or growth of PWSCC cracks in welds or weld overlays.

– Guidelines for material procurement specifications and weld quality are needed to minimize concerns for PWSCC

• Resolving these issues can inform regulatory consideration of inspection optimization for replacement components such as the reactor pressure vessel head with Alloy 690 penetrations.


Alloy 690/52/152 PWSCC EPRI Program Plan (1/2)

• Alloy 690 PWSCC Degradation Characterization • Alloy 690 HAZ PWSCC Degradation Characterization • Alloy 690/52/152 Macro and Microstructural Mapping and

Strain Analysis • Alloy 690/52/152 Expert Panel • Guidelines for Alloy 690 Material Procurement • Technical Bases for Regulatory Relief for Alloys 690/52/152 • CGR Data to Develop Flaw Disposition Curves for Alloys

690/52/152 • Weld Metals PWSCC Degradation Characterization • PWSCC Resistance of Evolutionary A52 Compositions

Above tasks executed per roadmap schedule

shown on next slide


Alloy 690/52/152 PWSCC EPRI Program Plan (2/2)


CGR Testing

• A690 Testing Parameters – Product form – Microstructure – Heat treatment – Cold work and direction – Crack Orientation – Heat Affected Zone (HAZ); Dilution Zone – Temperature, Stress intensity, Environment

• Alloy 52/152 Testing Parameters – Weld configuration – Crack orientation – Effect of pre-existing cracks – Weld overlay (Alloy 52/52M over Alloy 182/82) – Temperature, Stress intensity, Environment


HAZ PWSCC

• Concern for higher CGR in HAZ than base metal due to altered microstructure and residual strains

• Limited test results of HAZ specimens to date do not show high CGRs – Difficult to align specimen in narrow HAZ

Source: P. Andresen, GE Source: S. Bruemmer, PNNL


Residual Strains in Welds and HAZ

• Early estimates of up to 30% strain in HAZ (based on stainless steel HAZ studies) and even higher for HAZ after weld repairs – Rapid CGRs measured in 30% cold-worked Alloy 690 material

• Parallel work to characterize HAZ revealed maximum strains of ~12%


Residual Strains in Weld and HAZ (After 50% Repair)

• Less than 10% strain • Additional mock ups being fabricated

Repair Weld 1


Effect of Cold versus Hot Forging

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

11.5

11.7

11.9

12.1

12.3

12.5

12.7

12.9

500 1000 1500 2000 2500 3000

Con

duct

ivity

, µS/

cm o

r Pot

entia

l, V s

he

Cra

ck le

ngth

, mm

Test Time, hours

SCC#2 - c523 - 690, ENSA SP547, As-Rec'd, 32% Forge, S-L

Outlet conductivity x 0.01

CT potentialPt potential

c523 - 0.5TCT of 690 AR, 32% Forge, S-L35 MPa√m, 360C, 600B/1Li, 26 cc/kg H2

To

Con

stan

t K

@ 1

173h

At 325C, pH = 7.74. At 300C, pH = 7.40

3.1 x 10-7

mm/s

To

9000

s ho

ld @

454

h

1.1 x 10-7

mm/s

6.0 x 10-8

mm/s

Corrected Data

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

11.1

11.11

11.12

11.13

11.14

11.15

11.16

11.17

600 1100 1600 2100 2600 3100

Con

duct

ivity

, µS/

cm o

r Pot

entia

l, V s

he

Cra

ck le

ngth

, mm

Test Time, hours

SCC#2 - c618 - 690, SP547, 30% HForge @1300F in Th, S-L



c618 - 0.5TCT of 690 AR, 30% Hot Forge, S-L33 MPa√m, 360C, 600B/1Li, 26 cc/kg H2

At 325C, pH = 7.74. At 300C, pH = 7.40

5.6 x 10-9

mm/s

* 5% fall, 95% rise (~500s)

To

28,3

00s

hold

* @

137

1h

~0 mm/s

To

85,9

00s

hold

* @

259

0h

To

9000

s ho

ld*

@ 6

01h

1.6 x 10-8

mm/s32% Cold Forged ENSA SP547 – S-L

30% Hot Forged ENSA SP547 – S-L

12 © 2013 Electric Power Research Institute, Inc. All rights reserved. 12

Hot Forging vs. Cold Forging

Low growth rates when hot forged

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

10 15 20 25 30 35 40 45 50

Crac

k G

row

th R

ate,

mm

/s

Stress Intensity Factor, MPa√m

Alloy 690 CRDM in PWR Water

114092 33% Cold Forge

114092 30% Hot Forge

SP547 32% Cold Ford

SP547 30% Hot Forge

Alloy 690 CRDM600 ppm B, 1 ppm Li

360C Water, 26 cc/kg H2

325C PWR Water A182

A600

MRP Disposition Curves

A82

Very

Low

--

Low

--

Med

ium

---

Hig

h ---

Very

Hig

h

Nov'12

>20X Effect of Hot Forging

** Only 20% CW


Effect of Cold Work on CGR

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

12.8

12.9

13

13.1

13.2

13.3

13.4

13.5

13.6

13.7

1700 1900 2100 2300 2500 2700 2900 3100 3300 3500 3700

Con

duct

ivity

, µS/

cm o

r Pot

entia

l, V s

he

Cra

ck le

ngth

, mm

Test Time, hours

SCC#4 - c504 - 690, WQ199, As-Rec'd, 31% Forge, S-L




At 325C, pH = 7.74. At 300C, pH = 7.40

1.0 x 10-7

mm/s

1.6 x 10-7

mm/s

To

Con

stan

t K

@ 1

687h

Corrected Data

31% Forged CRDM WQ199 – S-L

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

12.12

12.14

12.16

12.18

12.2

12.22

12.24

12.26

12.28

12.3

1700 1900 2100 2300 2500 2700 2900 3100 3300 3500 3700

Con

duct

ivity

, µS/

cm o

r Pot

entia

l, V s

he

Cra

ck le

ngth

, mm

Test Time, hours

SCC#4 - c505 - 690, WQ199, As-Rec'd, 21% Forge, S-L




At 325C, pH = 7.74. At 300C, pH = 7.40

2.8 x 10-8

mm/s

1.9 x 10-8

mm/sTo

Con

stan

t K

@ 1

687h

Corrected Data


-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

11.02

11.025

11.03

11.035

11.04

11.045

800 1000 1200 1400 1600 1800 2000

Con

duct

ivity

, µS/

cm o

r Pot

entia

l, V s

he

Cra

ck le

ngth

, mm

Test Time, hours

SCC#2a - c585 - 690, CRDM WQ199, As-Rec'd, 15% Forge, S-L




At 325C, pH = 7.74. At 300C, pH = 7.40

1.4 x 10-8

mm/s

To

9000

s ho

ld*

@ 2

50h

1 x 10-9 mm/s

* 5% fall, 95% (~500s) riseTo

Con

stan

t K

@ 1

269h


14 © 2013 Electric Power Research Institute, Inc. All rights reserved. 14

Effect of Cold Forging: CRDM WQ199 – S-L

Low growth rates at 13% cold forge

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

10 15 20 25 30 35 40 45 50

Crac

k G

row

th R

ate,

mm

/s

Stress Intensity Factor, MPa√m

Alloy 690 in PWR Water

WQ199 - 32% CF, S-L

WQ199 - 20% CF, S-L

WQ199- 13% CF, S-L

Alloy 690 CRDM600 ppm B, 1 ppm Li

360C Water, 26 cc/kg H2

325C PWR Water A182

A600

MRP Disposition Curves

A82

Very

Low

--

Low

--

Med

ium

---

Hig

h ---

Very

Hig

h

Nov'12

Effect of Cold Work


Summary Alloy 690 CGR Testing

• Relatively high CGRs measured in certain specimen orientations after appreciable (>20%) levels of cold work, CGRs reduce at lower cold work levels

• Clear evidence of effect of cold versus hot forging on CGRs • The role of banding in measured high CGRs has not been confirmed;

but effect is expected to be small • Tests to date do not show high CGR susceptibility in the weld HAZ, but

testing of such specimens is still limited • Weld and HAZ strains even after weld repair appear in the 10 to 15%

range (not a major concern), work continuing • Concern for dilution zone at interface with low-chrome material needs

to be addressed


Alloys 52/152 CGR Testing Current Status

• To date, only one laboratory has shown PWSCC CGRs of real concern for Alloy 152 (~5xE-08mm/s) – Substantial other data show CGRs in the 5xE-09mm/s

range • Some evidence is emerging that pre-existing weld flaws in

the form of hot cracks affect neither the propensity to PWSCC initiation nor to crack growth; more work is continuing


PWSCC Initiation Testing for Alloy 690 and Weld Metals

• Initiation of PWSCC cracks and their growth to detectable levels represents >80% of component life

• Current approach on inspection intervals based on growth of a detectable crack, no recognition for time for crack to initiate

• The NRC/MRP are now developing a probabilistic regulatory framework (xLPR) that will allow recognition of crack initiation times allowing optimization of inspection strategy

• Need PWSCC initiation test data to benefit from xLPR

Perform PWSCC initiation time testing for Alloy 690 and weld metals accounting for variables such as cold work, HAZ, surface conditions, weld design, heat-to-heat and vendor variations, and environment.

Develop PWSCC initiation test data to establish basis for alternate inspection intervals for Alloy 690 components in the xLPR framework.

Objective & Scope

Issue

Crack Nucleation

Crack Precursor

Short Crack

Crack Growth

Detectable Crack


PWSCC Initiation Testing Projects

• Advanced Nuclear Technology project on PWSCC initiation testing of Alloy 52 (2013-2016)

• EPRI funded project at KHNP for PWSCC initiation testing of Alloy 690 at 400ºC steam (2013-2016)

• MRP funded project on PWSCC initiation testing of Alloy 690 under primary water conditions (2014-2017)

• EDF/MAI project on PWSCC initiation of steam generator plugs

These will feed into the xPLR platform


Alloy 690 RVH Inspection Optimization

• Objectives: – Develop an alternative inspection regime for reactor vessel

heads with Alloy 690 nozzles – Develop an associated robust technical basis

• Treatment of A690 heads in ASME CC N-729-1 was intended to be conservative and subject to reassessment once “additional laboratory data and plant experience on the performance of Alloy 690 and Alloy 52/152 weld metals become available [N-729-1 tech basis]”

– Lessons learned will be applied in future efforts seeking regulatory acceptance of optimized inspection requirements for other applications of Alloys 690/52/152 such as for inlays and on-lays


Together…Shaping the Future of Electricity

Documents

PWSCC of Alloy 690 and Weld Metals - NRC: Home Page · 2013. 6. 13. · SCC#2a - c585 - 690, CRDM WQ199, As -Rec'd, 15% Forge, S-L. Outlet conductivity x 0.01 Pt potential CT potential