NUREG/CR-6826 

 ANL-03/22 

 

 

Fracture Toughness and

Crack Growth Rates of

Irradiated Austenitic

Stainless Steels 

Argonne National Laboratory

U.S. Nuclear Regulatory Commission

Office of Nuclear Regulatory Research

Washington, DC 20555-0001
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 NUREG/CR-6826 

 ANL-03/22 

 

Fracture Toughness and

Crack Growth Rates of

Irradiated Austenitic 

Stainless Steels

Manuscript Completed: March 2003

Date Published: August 2003

Prepared by

O.K. Chopra, E.E. Gruber, W.J. Shack

Argonne National Laboratory

9700 South Cass Avenue

Argonne, IL 60439

W.H. Cullen, Jr., and C.E. Moyer, NRC Project Managers

Prepared for

Division of Engineering Technology 

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555-0001

NRC Job Code Y6388 
ii
iii 

Fracture Toughness and Crack Growth Rates

of Irradiated Austenitic Stainless Steels

by

O. K. Chopra, E. E. Gruber, and W. J. Shack

Abstract

Austenitic stainless steels (SSs) are used extensively as structural alloys in the internal

components of reactor pressure vessels because of their superior fracture toughness

properties. However, exposure to high levels of neutron irradiation for extended periods leads

to significant reduction in the fracture resistance of these steels. Experimental data are

presented on fracture toughness and crack growth rates (CGRs) of austenitic SSs irradiated to

fluence levels up to 2.0 x 1021 n/cm2 (E > 1 MeV) (a3.0 dpa) at a288°C. Crack growth tests

were conducted under cycling loading and long hold time trapezoidal loading in simulated

boiling water reactor (BWR) environments, and fracture toughness tests were conducted in air.

Neutron irradiation at 288°C decreases the fracture toughness of the steels; the data from

commercial heats fall within the scatter band for the data obtained at higher temperatures. In

addition, the results indicate significant enhancement of CGRs of the irradiated steels in

normal water chemistry BWR environment; the CGRs for irradiated steels are a factor of a5

higher than the disposition curve proposed for sensitized austenitic SSs. The rates decreased

by more than an order of magnitude in low–dissolved–oxygen BWR environment.
iv
v 

Contents

Abstract.................................................................................................................................... iii

Executive Summary................................................................................................................. xiii

Acknowledgments .................................................................................................................... xv

1. Introduction .................................................................................................................... 1

2. Experimental................................................................................................................... 3

2.1 J–R Curve Characterization................................................................................ 6

2.2 Crack Growth Rate Tests.................................................................................... 11

2.2.1 Procedure............................................................................................. 11

2.2.2 Data Qualification ............................................................................... 12

2.2.3 Effect of Specimen Size........................................................................ 13

3. Results............................................................................................................................. 15

3.1 Fracture Toughness............................................................................................ 15

3.1.1 Nonirradiated Type 304 Stainless Steel.............................................. 15

3.1.2 Irradiated Type 304 Stainless Steels................................................... 18

3.2 Crack Growth Tests on Irradiated Stainless Steels in BWR Environments...... 21

3.2.1 Specimen C3-B Irradiated to 0.9 x 1021 n/cm2 ................................. 22

3.2.2 Specimen C3-C Irradiated to 2.0 x 1021 n/cm2 ................................. 26

3.2.3 Specimen C16-B Irradiated to 2.0 x 1021 n/cm2 ............................... 29

3.2.4 Specimen C3-A Irradiated to 0.3 x 1021 n/cm2 ................................. 34

3.2.5 CGRs of Irradiated Austenitic SSs under Continuous Cycling .......... 37

3.2.6 CGRs of Irradiated Austenitic SSs under Cycling with Long Hold

Periods ................................................................................................. 38

4. Summary......................................................................................................................... 39

References ................................................................................................................................ 41

Appendix .................................................................................................................................. 45
vi

Figures

1. Fracture toughness JIc as a function of neutron exposure for austenitic

Types 304 and 316 SS ............................................................................................... 1

2. Configuration of compact–tension specimen used for this study............................. 3

3. Schematic representation of hot–cell J–R test facility............................................... 3

4. Schematic of the actuator, load cell, test train, autoclave, and furnace.................. 4

5. Schematic diagram of recirculating water system .................................................... 5

6. Examples of load-vs.-loadline displacement curves for irradiated specimens of

Heats C19 and L20 of Type 304 SS tested at 288°C................................................. 7

7. Fracture toughness J–R curves obtained from DC potential and elastic

unloading compliance methods for specimens Y4–02 and Y4–03 of thermally

aged cast CF–8M SS................................................................................................... 9

8. Fracture toughness J–R curves obtained from DC potential and elastic

unloading compliance methods for thermally aged Heat 75 of cast CF–8M SS;

specimen 75–03T, 75–04T, and 75–10T.................................................................... 10

9. Fracture toughness J–R curves obtained from DC potential and elastic

unloading compliance methods for 50% cold–worked Type 316NG; specimen

184–38 and 184–40.................................................................................................... 10

10. Fracture toughness J–R curves for 1/4–T and 1–T CT specimens of aged Heat 75

of CF–8M cast stainless steel at 288°C...................................................................... 11

11. Crack growth rate data under continuous cycling for thermally aged cast SS and

50% cold–worked Type 316LN SS in high–purity water at 289°C. ........................... 13

12. Stress corrosion cracking data for austenitic stainless steels in high–DO water at

289°C.......................................................................................................................... 14

13. Fracture toughness J–R curve obtained by DC potential and unloading

compliance methods for nonirradiated specimens L2–C and L2–E of Heat L2 of

Type 304 SS at 288°C. ............................................................................................... 15

14. Fracture toughness J–R curve obtained by DC potential and unloading

compliance methods for nonirradiated specimen L20–D of Heat L20 of

Type 304 SS at 288°C. ............................................................................................... 16

15. Fracture toughness J–R curve obtained by DC potential and unloading

compliance methods for nonirradiated specimens C16–C and C16–D of Heat C16

of Type 316 SS at 288°C. ........................................................................................... 16

16. Fracture toughness J–R curve obtained by DC potential and unloading

compliance methods for nonirradiated specimen C19–D of Heat C19 of

Type 304 SS at 288°C. ............................................................................................... 17
vii 

17. Fracture toughness J–R curves for nonirradiated Type 304 stainless steels

at 288°C...................................................................................................................... 17

18. Photomicrographs of fracture surfaces of nonirradiated specimens of Heats L2

and L20 tested at 288°C. ........................................................................................... 17

19. Photomicrograph of fracture surface of nonirradiated specimen of Heat C19

tested at 288°C........................................................................................................... 18

20. Photomicrograph of MnS inclusions on the fracture surface of nonirradiated

specimen of Heat L2 tested at 288°C......................................................................... 18

21. Fracture toughness J–R curve obtained by DC potential and unloading

compliance methods at 288°C for Heat C19 of Type 304 SS irradiated to a

fluence level of 0.3, 0.9, and 2.0 x 1021 n/cm2. ....................................................... 19

22. Fracture toughness J–R curve obtained by DC potential and unloading

compliance methods at 288°C for Heat C16 of Type 316 SS irradiated to a

fluence level of 0.9 x 1021 n/cm2.............................................................................. 20

23. Fracture toughness J–R curve obtained by DC potential and unloading

compliance methods at 288°C for Heat L20 of Type 304 SS irradiated to a

fluence level of 0.3 and 0.9 x 1021 n/cm2................................................................. 20

24. Fracture toughness J–R curve obtained by DC potential and unloading

compliance methods at 288°C for Heat L2 of Type 304 SS irradiated to a fluence

level of 0.9 x 1021 n/cm2........................................................................................... 21

25. Fracture toughness JIc of austenitic stainless steels as a function of neutron

exposure at 288°C...................................................................................................... 21

26. Changes in crack length and ECP after the dissolved oxygen level in the

feedwater was decreased from a500 to 10 ppb and increased from a10 to

300 ppb ...................................................................................................................... 23

27. Photomicrographs of the fracture surface of specimen C3–B tested in high–purity

water at 289°C............................................................................................................ 23

28. Crack–length–vs.–time plots for irradiated Type 304 SS in high–purity water at

289°C during test periods 2–5, 6, 7–8, 9–12, and 14–15.......................................... 24

29. Change in crack length and ECP of Pt and SS electrodes for Specimen C3–C

after the dissolved oxygen level in the feedwater was decreased from a300 to

10 ppb......................................................................................................................... 27

30. Photomicrographs of the fracture surface of Specimen C3–C .................................. 27

31. Crack–length–vs.–time plots for irradiated Type 304 SS in high–purity water at

289°C during test periods 1–2, 3–5, 6–7, and 7–8.................................................... 28

32. Change in crack length and ECP of Pt and SS electrodes when the DO level in

feedwater was decreased from a300 to <40 ppb and increased from <40 to

a300 ppb..................................................................................................................... 30
viii

33. Photomicrographs of the fracture surface of Specimen C16–B ................................ 31

34. Crack–length–vs.–time plots for irradiated Type 316 SS in high–purity water at

289°C during test periods up to 1, 2–3, 4–5, 6–7, 8–10, 11–12, and 13–15............ 31

35. Photomicrographs of the fracture surface of Specimen C3–A................................... 35

36. Crack–length–vs.–time plots for irradiated Type 316 SS in high–purity water at

289°C during test periods 1–2, 3–5, 6–7, 8–10, and 11–12...................................... 35

37. CGR data for irradiated austenitic SSs under continuous cycling at 289°C in

high–purity water with a300 ppb and <30 ppb dissolved oxygen. ........................... 37

38. CGR data under constant load with periodic partial unloads for irradiated

austenitic SSs in high–purity water at 289°C ........................................................... 38

A-1.1. Load-vs.-loadline displacement curve for specimen Y4–03 of thermally aged

CF–8M cast SS tested at 288°C ................................................................................. 48

A-1.2. Fracture surface of specimen Y4–03 tested at 288°C ............................................... 48

A-2.1. Load-vs.-loadline displacement curve for specimen Y4–02 of thermally aged

CF–8M cast SS tested at 288°C ................................................................................. 50

A-2.2. Fracture surface of specimen Y4–02 tested at 288°C ............................................... 50

A-3.1. Load-vs.-loadline displacement curve for specimen 75–03T of thermally aged

CF–8M cast SS tested at 288°C ................................................................................. 52

A-3.2. Fracture surface of specimen 75–03T tested at 288°C ............................................. 52

A-4.1. Load-vs.-loadline displacement curve for specimen 75–04T of thermally aged

CF–8M cast SS tested at 288°C ................................................................................. 54

A-4.2. Fracture surface of specimen 75–04T tested at 288°C ............................................. 54

A-5.1. Load-vs.-loadline displacement curve for specimen 75–10T of thermally aged

CF–8M cast SS tested at 288°C ................................................................................. 56

A-5.2. Fracture surface of specimen 75–10T tested at 288°C ............................................. 56

A-6.1. Load-vs.-loadline displacement curve for specimen 184–38 of 50% cold–worked

Type 316NG SS tested at 288°C ................................................................................ 58

A-6.2. Fracture surface of specimen 184–38 tested at 288°C ............................................. 58

A-7.1. Load-vs.-loadline displacement curve for specimen 184–40 of 50% cold–worked

Type 316NG SS tested at 288°C ................................................................................ 60

A-7.2. Fracture surface of specimen 184–40 tested at 288°C ............................................. 60

A-8.1. Load-vs.-loadline displacement curve for specimen C19–D of nonirradiated

Type 304 SS tested at 288°C ..................................................................................... 62
ix 

A-8.2. Fracture surface of specimen C19–D tested at 288°C .............................................. 62

A-9.1. Load-vs.-loadline displacement curve for specimen C16–C of nonirradiated

Type 316 SS tested at 288°C ..................................................................................... 64

A-9.2. Fracture surface of specimen C16–C tested at 288°C............................................... 64

A-10.1. Load-vs.-loadline displacement curve for specimen C16–D of nonirradiated

Type 316 SS tested at 288°C ..................................................................................... 66

A-10.2. Fracture surface of specimen C16–D tested at 288°C .............................................. 66

A-11.1. Load-vs.-loadline displacement curve for specimen L20–D of nonirradiated

Type 304 SS tested at 288°C ..................................................................................... 68

A-11.2. Fracture surface of specimen L20–D tested at 288°C............................................... 68

A-12.1. Load-vs.-loadline displacement curve for specimen L2–C of nonirradiated

Type 304 SS tested at 288°C ..................................................................................... 70

A-12.2. Fracture surface of specimen L2–C tested at 288°C................................................. 70

A-13.1. Load-vs.-loadline displacement curve for specimen L2–E of nonirradiated

Type 304 SS tested at 288°C ..................................................................................... 72

A-13.2. Fracture surface of specimen L2–E tested at 288°C ................................................. 72

A-14.1 Load-vs.-loadline displacement curve for specimen C19–A of irradiated

Type 304 SS tested at 288°C ..................................................................................... 74

A-14.2 Fracture surface of specimen C19–A tested at 288°C............................................... 74

A-15.1 Load-vs.-loadline displacement curve for specimen C19–B of irradiated

Type 304 SS tested at 288°C ..................................................................................... 76

A-15.2 Fracture surface of specimen C19–B tested at 288°C............................................... 76

A-16.1 Load-vs.-loadline displacement curve for specimen C19–C of irradiated

Type 304 SS tested at 288°C ..................................................................................... 78

A-16.2 Fracture surface of specimen C19–C tested at 288°C............................................... 78

A-17.1 Load-vs.-loadline displacement curve for specimen C16–A of irradiated

Type 316 SS tested at 288°C ..................................................................................... 80

A-17.2 Fracture surface of specimen C16–A tested at 288°C............................................... 80

A-18.1. Load-vs.-loadline displacement curve for specimen L20–A of irradiated

Type 304 SS tested at 288°C ..................................................................................... 82

A-18.2. Fracture surface of specimen L20–A tested at 288°C ............................................... 82

A-19.1. Load-vs.-loadline displacement curve for specimen L20–B of irradiated

Type 304 SS tested at 288°C ..................................................................................... 84
x

A-19.2. Fracture surface of specimen L20–B tested at 288°C............................................... 84

A-20.1. Load-vs.-loadline displacement curve for specimen L2–A of irradiated

Type 304 SS tested at 288°C ..................................................................................... 86

A-20.2. Fracture surface of specimen L2–A tested at 288°C ................................................. 86

Tables

1. Composition of austenitic stainless steels irradiated in the Halden reactor............ 6

2. Tensile properties of irradiated austenitic stainless steels at 288°C........................ 6

3. Crack growth results for Specimen C3–B of Type 304 SS in high–purity water

at 289°C...................................................................................................................... 22

4. Crack growth results for Specimen C3–C of Type 304 SS in high–purity water

at 289°C...................................................................................................................... 26

5. Crack growth results for Specimen C16–B of Type 316 SS in high–purity water

at 289°C...................................................................................................................... 29

6. Crack growth results for Specimen C3–A of Type 304 SS in high–purity water

at 289°C...................................................................................................................... 34

A-1. Test data for specimen Y4–03 of thermally aged CF–8M cast SS tested at

288°C.......................................................................................................................... 47

A-2. Test data for specimen Y4–02 of thermally aged CF–8M cast SS tested at

288°C.......................................................................................................................... 49

A-3. Test data for specimen 75–03T of thermally aged CF–8M cast SS tested at

288°C.......................................................................................................................... 51

A-4. Test data for specimen 75–04T of thermally aged CF–8M cast SS tested at

288°C.......................................................................................................................... 53

A-5. Test data for specimen 75–10T of thermally aged CF–8M cast SS tested at

288°C.......................................................................................................................... 55

A-6. Test data for specimen 184–38 of 50% cold–worked Type 316NG SS tested at

288°C.......................................................................................................................... 57

A-7. Test data for specimen 184–40 of 50% cold–worked Type 316NG SS tested at

288°C.......................................................................................................................... 59

A-8. Test data for specimen C19–D of nonirradiated Type 304 SS tested at 288°C........ 61

A-9. Test data for specimen C16–C of nonirradiated Type 316 SS tested at 288°C ........ 63
xi 

A-10. Test data for specimen C16–D of nonirradiated Type 316 SS tested at 288°C........ 65

A-11. Test data for specimen L20–D of nonirradiated Type 304 SS tested at 288°C......... 67

A-12. Test data for specimen L2–C of nonirradiated Type 304 SS tested at 288°C........... 69

A-13. Test data for specimen L2–E of nonirradiated Type 304 SS tested at 288°C........... 71

A-14. Test data for specimen C19–A of irradiated Type 304 SS tested at 288°C............... 73

A-15. Test data for specimen C19–B of irradiated Type 304 SS tested at 288°C............... 75

A-16. Test data for specimen C19–C of irradiated Type 304 SS tested at 288°C .............. 77

A-17. Test data for specimen C16–A of irradiated Type 316 SS tested at 288°C............... 79

A-18. Test data for specimen L20–A of irradiated Type 304 SS tested at 288°C ............... 81

A-19. Test data for specimen L20–B of irradiated Type 304 SS tested at 288°C............... 83

A-20. Test data for specimen L2–A of irradiated Type 304 SS tested at 288°C ................. 85
xii
xiii 

Executive Summary

Austenitic stainless steels (SSs) are used extensively as structural alloys in the internal

components of reactor pressure vessels because of their high strength, ductility, and fracture

toughness. Fracture of these steels occurs by stable tearing at stresses well above the yield

stress, and tearing instabilities require extensive plastic deformation. However, exposure to

neutron irradiation for extended periods changes the microstructure and degrades the fracture

properties of these steels. Irradiation leads to a significant increase in yield strength and

reduction in ductility and fracture resistance of austenitic SSs. Existing data on fracture

toughness of austenitic SSs indicate substantial decrease in toughness at exposures of

1–10 dpa; the effect is largest in high–toughness steels. However, most of the existing fracture

toughness test data have been obtained at temperatures above 350°C; fracture toughness

results that are relevant to light water reactors (LWRs) are very limited.

In addition, radiation can exacerbate the corrosion fatigue and stress corrosion cracking

(SCC) behavior of SSs by affecting the material microchemistry, e.g., radiation–induced

segregation; material microstructure, e.g., radiation hardening; and water chemistry, e.g.,

radiolysis. Service failures in core components of several operating reactors have been

attributed to irradiation assisted stress corrosion cracking (IASCC). While initially considered

as a unique form of cracking that would not occur in the absence of radiation, IASCC is now

generally considered as a radiation accelerated environmental cracking process. It has been

termed as premature subcritical cracking of materials exposed to ionizing irradiation. The

factors that influence SCC susceptibility of materials include neutron fluence, cold work,

corrosion potential, water purity, temperature, and loading.

This report presents experimental data on fracture toughness and crack growth rate

(CGR) for austenitic Types 304 and 316 SS that were irradiated to fluence levels of a0.3, 0.9,

and 2.0 x 1021 n/cm2 (E > 1 MeV) (a0.45, 1.35, and 3.0 dpa) at a288°C. The irradiations were

carried out in a He environment in the Halden heavy water boiling reactor. Fracture toughness

tests were conducted in air and CGR tests in normal water chemistry (NWC) and hydrogen

water chemistry (HWC) BWR environments at a288°C. All tests were performed on 1/4–T

compact tension specimens.

Neutron irradiation at 288°C to 2.0 x 1021 n/cm2 (E > 1 MeV) (3.0 dpa) decreased the

fracture toughness of all of the steels. In general, fracture toughness of the commercial Heats

C16 and C19 is superior to that of the laboratory Heats L20 and L2. These differences arise

primarily from differences in toughness of the nonirradiated steels, i.e., the fracture toughness

of the laboratory heats is significantly lower than that of the commercial heats. The fracture

toughness J–R curves for irradiated Types 304 and 316 SS are comparable. The data from

commercial heats fall within the scatter band for the data obtained at higher temperatures.

For Heat C19 of Type 304 SS irradiated to 0.3, 0.9, and 2.0 x 1021 n/cm2, the JIc values are

507, 313, and 188 kJ/m2, respectively.

The results indicate significant enhancement of CGRs of irradiated steel in the NWC BWR

environment. The CGRs of irradiated steels are a factor of a5 higher than the disposition curve

proposed in NUREG–0313 for sensitized austenitic SSs in water with 8 ppm dissolved oxygen

(DO). The CGRs of Type 304 SS irradiated to 0.9 and 2.0 x 1021 n/cm2 and of Types 304 and

316 SS irradiated to 2.0 x 1021 n/cm2 are comparable.
xiv

In low–DO BWR environments, the CGRs of the irradiated steels decreased by an order of

magnitude in some tests, e.g., Heat C3 of Type 304 SS irradiated to 0.9 x 1021 n/cm2 and Heat

C16 of Type 316 SS irradiated to 2 x 1021 n/cm2. The beneficial effect of decreased DO was

not observed for Heat C3 of Type 304 SS irradiated to 2 x 1021 n/cm2; it is possible that this

different behavior is associated with the loss of constraint in the specimen due to the high

applied load.

Type 304 SS irradiated to 0.3 x 1021 n/cm2 shows very little environmental enhancement

of CGRs in the NWC BWR environment; the CGRs under SCC conditions are below the

disposition curve for sensitized SSs in water with 8 ppm DO given in NUREG–0313.
xv 

Acknowledgments

The authors thank T. M. Galvin, L. A. Knoblich, E. J. Listwan, and R. W. Clark for their

contributions to the experimental effort. This work is sponsored by the Office of Nuclear

Regulatory Research, U.S. Nuclear Regulatory Commission, under Job Code Y6388; Project

Manager: W. H. Cullen, Jr. and C. E. Moyer.
xvi
1 

1. Introduction

Austenitic stainless steels (SSs) are used extensively as structural alloys in reactor

pressure vessel internal components because of their high strength, ductility, and fracture

toughness. Fracture of these steels occurs by stable tearing at stresses well above the yield

stress, and tearing instabilities require extensive plastic deformation. However, exposure to

neutron irradiation for extended periods changes the microstructure and degrades the fracture

properties of these steels. Irradiation leads to a significant increase in yield strength and

reduction in ductility and fracture resistance of austenitic SSs.1–3 Changes in mechanical

properties are known to influence fatigue or corrosion fatigue properties of irradiated

materials.4 Irradiation assisted stress corrosion cracking (IASCC) is another degradation

process that affects light water reactor (LWR) internals exposed to fast neutron radiation.1,5,6

Neutron irradiation of austenitic SSs at temperatures below 400°C leads to the formation

of a substructure with very fine defects that consist of small (<5 nm) vacancy and interstitial

loops or “black spots” and larger (>5 nm) faulted interstitial loops.7–9 The latter are obstacles

to dislocation motion and lead to matrix strengthening and increase in tensile strength. Also,

irradiation–induced defects cause loss of ductility and reduced strain-hardening capacity of the

material. The effects of radiation on various austenitic SSs vary significantly and appear to be

related to minor differences in the chemical composition of the steels;1 the chemical

composition can influence the stacking fault energy and/or irradiation–induced

microstructure. As yield strength approaches ultimate strength, planar slip or dislocation

channeling is promoted and leads to pronounced degradation in the fracture resistance of

these steels.3 In general, higher stacking–fault energy enhances and cold working inhibits

dislocation channeling.1

0

200

400

600

800

1000

1200

0 5 10 15 20 25

Michel & Gray, 1987

Van Osch et al., 1997

Dufresne et al., 1979

Mills et al., 1985

Mills, 1988

Bernard & Verzeletti, 1985

Picker et al., 1983

Ould et al., 1988 JIc (kJ/m2)

Neutron Exposure (dpa)

Types 304 & 316 SS

Irradiation Temp: 350 - 450°C

Test Temp: 350 - 427°C

Figure 1.

Fracture toughness JIc as a function of

neutron exposure for austenitic Types 304

and 316 SS

The effect of neutron exposure on the fracture toughness JIc of austenitic SSs irradiated

at 350–450°C is shown in Fig. 1.10–18 The effects of irradiation may be divided into three

regimes: little or no loss of toughness below a threshold exposure of a1 dpa, substantial
2

decrease in toughness at exposures of 1–10 dpa, and no further reduction in toughness above

a saturation exposure of 10 dpa. The effect is largest in high–toughness steels. The

degradation in fracture properties saturates at a JIc value of a30 kJ/m2 (or equivalent critical

stress intensity factor KJc of 70 MPa m0.5). Also, the failure mode changes from dimple

fracture to channel fracture. However, most of the existing fracture toughness test data have

been obtained at temperatures above 350°C; fracture toughness results that are relevant to

LWRs are very limited.2

Radiation can exacerbate the corrosion fatigue and stress corrosion cracking (SCC)

behavior of SSs by affecting the material microchemistry, e.g., radiation–induced segregation;

material microstructure, e.g., radiation hardening; and water chemistry, e.g., radiolysis.5

Service failures in core components of several boiling water reactors (BWRs)1 9,20 and

pressurized water reactors (PWRs)4,21 have been attributed to IASCC. While initially

considered as a unique form of cracking that would not occur in the absence of radiation,

IASCC is now generally considered as a radiation accelerated environmental cracking process.

It has been termed as premature subcritical cracking of materials exposed to ionizing

irradiation.

The factors that influence SCC susceptibility of materials include neutron fluence, cold

work, corrosion potential, water purity, temperature, and loading. The effects of neutron

fluence on IASCC of austenitic SSs has been investigated for BWR control blade sheaths20 and

laboratory tests on BWR–irradiated material;5,22–24 the extent of intergranular SCC increases

with fluence. Although a threshold fluence level of 5 x 1020 n/cm2 (E >1 MeV) has been

reported for austenitic SSs in BWR environment, the experimental data show an increase in

intergranular cracking above a fluence of a2 x 1020 n/cm2 (E >1 MeV) (a0.3 dpa). The results

also show the beneficial effect of reducing the corrosion potential of the environment.25,26

However, low corrosion potential does not provide immunity to IASCC, e.g., intergranular SCC

has been observed in cold worked, irradiated SS baffle bolts in PWRs. The threshold fluence

for IASCC is higher under low potential conditions such as HWC in BWRs or PWR primary

water chemistry.

This report presents experimental data on fracture toughness, corrosion fatigue, and

stress corrosion cracking (SCC) of austenitic SSs that were irradiated to fluence levels of a0.3,

0.9, and 2.0 x 1021 n/cm2 (E > 1 MeV) (a0.45, 1.35, and 3.0 dpa) at a288°C. The irradiations

were carried out in a He environment in the Halden heavy water boiling reactor. Fracture

toughness tests were conducted in air and CGR tests in normal water chemistry (NWC) and

low–DO BWR environments at 288°C. The results are compared with the existing data

obtained from irradiated reactor internal components removed from operating plants and

materials irradiated in test reactors.
3 

2. Experimental

Fracture toughness J–R curve and crack growth rate (CGR) tests have been conducted at

288°C on several austenitic SSs that were irradiated up to 2.0 x 1021 n/cm2 (E > 1 MeV)

(a3.0 dpa) at a288°C in a helium environment in the Halden boiling heavy water reactor. The

tests were performed on 1/4–T compact tension (CT) specimens; the J–R curve tests were

performed in air and CGR tests in BWR environments. A modified configuration of the CT

specimen geometry, Fig. 2, was used in the present study. Crack extensions were determined

by both DC potential and elastic unloading compliance techniques.

'C'

7.00

7.00

3.30

3.30

.794

CENTERED

3.00 DIA.

2 THRU HOLES

+.05

- .00 15.00

14.00

6.50

'M'

A A .02

A .02

B

B .02

A .02

A .02

6.00

12.00

2.00

1.53 DIA

2 THRU HOLES

2.00

2.00

1.45

3.25

1.45

#56 (1.19) DIA. DRILL 3.25 DP.

#0-80 UNF-2B TAP 2.17 ±.06 DP. 2

XXX-X

SPECIMEN ID

C

C .02

C .02

.45 R

.45

DETAIL 'M'

Figure 2. Configuration of compact–tension specimen used for this study (dimensions in mm)

Hydraulic

Actuator

Furnace

Load Cell

Pneumatic

Cyl inder

Figure 3. Schematic representation of hot–cell J–R test facility

The facility for conducting the tests is designed for in–cell testing, with the test train,

furnace, and other required equipment mounted on top of a portable wheeled cart that can be

easily rolled into the cell. A schematic representation of the system is shown in Fig. 3. A small
4

autoclave is installed inside the furnace for conducting tests in simulated BWR environments.

Water is circulated through a port in the autoclave cover plate that serves both as inlet and

outlet. The hydraulic actuator is mounted on top of the frame, with the test train components

suspended beneath it. A drawing of the actuator, load cell, test train, autoclave, and furnace

are shown in Fig. 4. The 22–kN (5–kip) load cell is at the top of the pull rod. The furnace is

mounted on a pneumatic cylinder and can be raised to enclose the autoclave with the load cage

and the specimen during the test. An Instron Model 8500+ Dynamic Materials Testing System

is used for performing the tests.

The load cage that contains the test specimen consists of the cover plate of a 1–liter SS

autoclave (from PARR Associates) and a 12.7–mm–thick bottom plate separated by four

compression rods. The lower two–piece clevis assembly is fastened to the bottom plate of the

cage with the two sections connected by an oxidized zircalloy pin, electrically insulated with

mica washers. The same arrangement is used for the upper clevice assembly, connected to the

pull rod. A 1/4–T CT specimen is mounted in the clevises with Inconel pins. Platinum wires

are used for the current and potential leads. The current leads are attached to SS split pins

that are inserted into the holes at the top and bottom of the specimen. The potential leads are

attached by screwing short SS pins into threaded holes in the specimen and attaching the

platinum wires with in–line SS crimps.

Furnace

Load Cage

Actuator

Load Cell

Compression

Columns (4)

LVDT

Pull Rod

Autoclave

Specimen

Figure 4. Schematic of the actuator, load cell, test train, autoclave, and furnace

The recirculating water system consists of a storage tank, high pressure pump,

regenerative heat exchanger, autoclave preheater, test autoclave, electrochemical potential

(ECP) cell preheater, ECP cell, regenerative heat exchanger, Mity MiteTM back-pressure

regulator, an ion–exchange cartridge, a 0.2 micron filter, a demineralizer resin bed, another
5 

0.2 micron filter, and return line to the tank. A schematic diagram of the recirculating water

system is shown in Fig. 5. Water is circulated at low flow rates, e.g., a10 mL/min.

The BWR environments comprise high–purity–deionized water that contains either

a300 ppb or <30 ppb DO resulting in ECPs for SS that range from 160 to -500 mV. The

feedwater is stored in a 135–L SS tank manufactured by Filpaco Industries. The tank is

designed for vacuum and over pressure to 60 psig. The deionized water is prepared by passing

purified water through a set of filters that comprise a carbon filter, an Organex–Q filter, two ion

exchangers, and a 0.2–mm capsule filter. Water samples are taken periodically to measure pH,

resistivity, and DO concentration. The DO level in water is established by bubbling nitrogen

that contains a1% oxygen through the deionized water in the supply tank. The DO is reduced

to <10 ppb by bubbling nitrogen through the water; a vacuum is drawn on the tank cover gas

to speed deoxygenation. The cover gas of the storage tank is nitrogen plus 1% oxygen for

high–DO environment, and either pure nitrogen or nitrogen plus 5% hydrogen for low–DO

environment.

 1. COVER GAS SUPPLY TANK

 2. HIGH-PRESSURE REGULATOR

 WITH FLASH ARRESTOR

 3. LOW-PRESSURE REGULATOR

 4. FLOW METER

 5. GAS PURIFIER

 6. PRESSURE GAUGE

 7. PRESSURE RELIEF VALVE

 8. VENT TO AIR WITH FLASH ARRESTOR

 9. FEEDWATER STORAGE TANK

10. SPARGE TUBE

11. FEEDWATER FILL PORT

12. WATER SAMPLE PORT

13. SOLENOID VALVE

14. 0.2–MICRON FILTER

15. HIGH-PRESSURE PUMP

16. CHECK VALVE

17. RUPTURE DISK

18. HEAT EXCHANGER

19. SYSTEM BLEED PORT

20. HIGH-PRESSURE GAUGE

21. AUTOCLAVE PREHEATER

22. PARR AUTOCLAVE

23. THERMOCOUPLE WELL

24. ECP CELL PREHEATER

25. ECP CELL

26. ECP CELL BYPASS LINE

27. BACK–PRESSURE RELIEF VAVLE

28. ION EXCHANGE CARTRIDGE

29. RECIRCULATING PUMP

30. DEMINERALIZER

31. DEMINERALIZER BYPASS LINE

20

12

19

30

14

7

5

6

8

9

10

11

13

15

17

21

23

24

OUTSIDE CELL INSIDE CELL V1

V3 V6

V7

V8

V17

22

V2

25

14

16

19

27

7

12

V12

V13

28 29

V9

18

26

V10

V11 V16

V4

V15

14 V14

V5

1

2 3

4

31

Figure 5. Schematic diagram of recirculating water system

The fracture toughness J–R curve tests were performed in accordance with the

requirements of ASTM Specification E 1737 for “J–Integral Characterization of Fracture

Toughness.” The CGR tests were performed in accordance with ASTM E–647 “Standard Test

Method for Measurement of Fatigue Crack Growth Rates” and ASTM E–1681 “Standard Test

Method for Determining a Threshold Stress Intensity Factor for Environment–Assisted
6

Cracking of Metallic Materials Under Constant Load.” The composition of the various heats of

irradiated austenitic SSs is presented in Table 1. The tensile yield and ultimate stress for the

various SSs irradiated to the three fluence levels and in the nonirradiated condition27,28 are

given in Table 2.

Table 1. Composition (wt.%) of austenitic stainless steels irradiated in the Halden reactor

Alloy

IDa

Vendor

Heat ID Analysis Ni Si P S Mn C N Cr Mo Ob

Type 304 SS

C3 PNL-C-6 Vendor 8.91 0.46 0.019 0.004 1.81 0.016 0.083 18.55

ANL 9.10 0.45 0.020 0.003 1.86 0.024 0.074 18.93 144

C19 DAN–74827 Vendor 8.08 0.45 0.031 0.003 0.99 0.060 0.070 18.21 –

ANL 8.13 0.51 0.028 0.008 1.00 0.060 0.068 18.05 200

L2 BPC–4–111 Vendor 10.50 0.82 0.080 0.034 1.58 0.074 0.102 17.02 66

L20 BPC–4–101 Vendor 8.91 0.17 0.010 0.004 0.41 0.002 0.002 18.10 –

ANL 8.88 0.10 0.020 0.005 0.47 0.009 0.036 18.06 940

Type 316 SS

C16 PNL–SS–14 Vendor 12.90 0.38 0.014 0.002 1.66 0.020 0.011 16.92 –

ANL 12.32 0.42 0.026 0.003 1.65 0.029 0.011 16.91 2.18 157

aFirst letters “C” and “L” denote commercial and laboratory heats, respectively.

bIn wppm.

Table 2. Tensile propertiesa of irradiated austenitic stainless steels at 288°C

Fluence (E >1 MeV)

Nonirradiated 0.3 x 1021 n/cm2 0.9 x 1021 n/cm2 2.0 x 1021 n/cm2

Steel Type

(Heat)

Yield

(MPa)

Ultimate

(MPa)

Yield

(MPa)

Ultimate

(MPa)

Yield

(MPa)

Ultimate

(MPa)

Yield

(MPa)

Ultimate

(MPa)

304 SS (C3) (154) (433) 338 491 632 668 796 826

304 SS (C19) 178 501 554 682 750 769 787 801

304 SS (L2) 193 348 – – 839 849 – –

304 SS (L20) – – 454 552 670

632

743

697

– –

316 SS (C16) (189) (483) 370 527 562 618 766 803

aEstimated values within parentheses.

The experimental data for the fracture toughness J–R curves are compiled in the

Appendix. Some of the results have been presented earlier.29–32 Because tensile properties of

the material were not available for some irradiation conditions, estimated values of flow stress

were used in the earlier presentations. In the present report, the fracture toughness results

have been reevaluated using tensile properties determined from comparably irradiated tensile

specimens.27,28

Also, in earlier publications,29–33 Heat C16 was erroneously identified as Type 304 SS.

Because the flow stress for solution annealed Type 316 SS is typically higher than that for

solution annealed Type 304 SS, the experimental data for nonirradiated Heat C16 have been

corrected in the present report; the difference is essentially in the slope of the blunting line.

2.1 J–R Curve Characterization

Before testing, the specimens were fatigue–precracked in air at room temperature. The

precracked specimens were then tested at 288°C at a constant extension rate; tests were

interrupted periodically to determine the crack length. Specimens were held at constant

extension to measure crack length by both the DC potential drop and elastic unloading

compliance techniques. For most steels, load relaxation occurs during the hold period or
7 

unloading, which causes a time-dependent nonlinearity in the unloading curve. Consequently,

before unloading, the specimen was held for a1 min to allow load relaxation. Elastic unloading

and reloading was carried out in the load control mode.

Specimen extension was monitored and controlled outside the high–temperature zone.

The displacement of load points was determined by subtracting the extension of the load train

from the measured extension. The load train displacement was determined as a function of

applied load using a very stiff specimen. The load–line displacements determined by this

method were compared with actual displacements measured optically during J–R curve tests at

room temperature. The measured and estimated values were in very good agreement; for

load–line displacements up to 2 mm, the error in the estimated values was <0.02 mm.33

Examples of load-vs.-loadline displacement curves for irradiated SS are shown in Fig. 6.

The J–integral was calculated from the load–vs.–loadline displacement curves according

to the correlations for DC(T) specimens in ASTM Specification E 1737. The following

correlation, obtained from the best–fit of the experimental data, was used to determine crack

lengths by the unloading compliance method.

ai/W = 1.2011 – 7.1572 ux + 16.87 ux

2 – 13.527 ux3, (1)

where

ux = 1 / [(BefEefCci)1/2 + 1], (2)

Bef = B –(B – BN)2 / B, (3)

Eef = E / (1 –u2), (4)

W is the specimen width, B is the specimen thickness, BN is the net specimen thickness or

distance between the roots of the side grooves, E is the elastic modulus, u is Poisson's ratio,

and Cci is the specimen elastic compliance corrected for rotation of the crack centerline. The

effective elastic modulus Eef was adjusted with the measured initial crack length ai, i.e., Eef

was determined from Eqs. 1 and 2 by using the measured fatigue precrack length ai and the

corresponding corrected specimen elastic compliance Cci.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 0.5 1 1.5 2 2.5 3 3.5 4

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JRI-21

288°C

Specimen C19–A

0.3 x 102 1 n cm– 2

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 0.5 1 1.5 2 2.5

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JRI-22

288°C Specimen L20–A

0.3 x 10-21 n cm – 2

(a) (b)

Figure 6. Examples of load-vs.-loadline displacement curves for irradiated specimens of Heats

(a) C19 and (b) L20 of Type 304 SS tested at 288°C
8

The following correlation, obtained from the best–fit of the experimental data for

normalized crack length and normalized DC potential, was used to determine crack lengths by

the DC potential method.

a

W

U

U

i = - Ê

Ë

Á ˆ

 ̄

 ̃

È

Î

Í

Í

 ̆

 ̊

 ̇

 ̇ 0 28887 0 5

0

0 34775

. .

.

, (5)

where W is the specimen width, and U and U0 are the current and initial potentials.

Equation 5 is comparable to the ASTM E 1737 correlation for a CT specimen with current

inputs at the W/4 position and DC potential lead connections at the W/3 position.

The DC potential data were corrected for the effects of plasticity on the measured

potential, i.e., large crack–tip plasticity can increase measured potentials due to resistivity

increases without crack extension. As per ASTM E 1737, the change in potential before crack

initiation was ignored, and the remainder of the potential change was used to establish the J–R

curve. A plot of normalized potential vs. loadline displacement generally remains linear until

the onset of crack extension. For all data within the linear portion of the curve, crack

extension was calculated from the blunting–line relationship Da = J/(4sf), where sf is the flow

stress defined as the average of the 0.2% offset yield stress and ultimate tensile stress. The

exclusion lines are parallel to the blunting line intersecting the abscissa at 0.15 and 1.50 mm.

Although ASTM E 813 specifies a slope of two times the effective yield stress (or flow

stress) for the offset line, a slope of four times the flow stress was used to define the offset and

exclusion lines. For high–strain–hardening materials, e.g., nonirradiated austenitic SSs, a

slope that is four times the flow stress (4sf) represents the blunting line better than the slope of

2sf defined in ASTM E 1737.3 In irradiated materials, the increase in yield stress is primarily

due to a high density of barriers to dislocation motion. During deformation as dislocations

sweep through the irradiated matrix, they annihilate the very fine scale of barriers, thus

creating a “channel” for easy dislocation motion. This may result in marked work softening.

To account for possible strain softening that may occur in irradiated materials, an effective flow

stress defined as the average of the nonirradiated and irradiated flow stress was used in J–R

curve data analysis. Because the effective flow stress discounts the irradiation–induced

increase in flow stress by a factor of 2, the slope of the blunting line was defined as 4sf even for

the irradiated materials.

The final crack size was marked by fatigue cycling at room temperature. The specimens

were then fractured and the initial (i.e., fatigue precrack) and final (test) crack lengths of both

halves of the fractured specimen were measured optically. The crack lengths were determined

by the 9/8 averaging technique, i.e., the two near–surface measurements were averaged and

the resultant value was averaged with the remaining seven measurements.

The elastic unloading compliance measurements were adjusted only with the measured

initial crack length, whereas the crack length measurements obtained by the DC potential–drop

technique were adjusted with both the initial and final crack lengths. The two-point pinning

method was used to correct the measured potentials from the test data. The corrected

normalized potentials NP are expressed in terms of the measured normalized potentials NP

(U/U0 in Eq. 5) by the relationship
9 

NP NP P

P P = --

1

2 1

. (6)

The variables P1 and P2 are solutions of the expressions

NP NP P

P P i

i i = -

2 1 - , (7)

and

NP

NP P

P P f

f i = -

2 1 - , (8)

where NPi and NPf are normalized potentials that correspond to initial and final crack lengths

determined from Eq. 5, and NPi and NPf are the measured values. The fracture toughness JIc

values were determined from ASTM E–813 as the intersection of the 0.2–mm offset line with the

power law fit (of the form J = Dan) of the test data between the 0.15– and 1.50–mm exclusion

lines.

Several fracture toughness J–R curve tests were conducted at room temperature and

288°C on thermally aged CF–8M cast SS and on a 50% cold–worked (CW) Type 316LN SS to

develop correlations for estimating crack lengths and to validate the test procedure.

Experimental data for the tests at 288°C are given in the Appendix, Tables A–1 to A–7.

For materials with relatively low fracture toughness, e.g., JIc <300 kJ/m2, the

measurements of crack extension by the elastic unloading compliance method showed

excellent agreement with those obtained by DC potential methods. The J–R curves obtained

from DC potential and elastic unloading compliance methods for thermally aged cast CF–8M

SSs and 50% cold–worked Type 316NG SS at 288°C are shown in Figs. 7–9. Replicate tests on

different specimens of the same material show good reproducibility of the J–R curves.

0

100

200

300

400

500

0 0.5 1 1.5 2 2.5 3 3.5

DC Potential

Elastic Unloading

Deformation J (kJ/m2)

Crack Extension (mm)

CF–8M (Specimen Y4–02)

Aged 700 h at 400°C

288°C

0

100

200

300

400

500

0 0.5 1 1.5 2 2.5 3 3.5

DC Potential

Elastic Unloading

Deformation J (kJ/m2

)

Crack Extension (mm)

CF–8M (Specimen Y4–03)

Aged 700 h at 400°C

288°C

(a) (b)

Figure 7. Fracture toughness J–R curves obtained from DC potential and elastic unloading compliance

methods for specimens (a) Y4–02 and (b) Y4–03 of thermally aged cast CF–8M SS
10

0

100

200

300

400

500

0 0.5 1 1.5 2 2.5 3 3.5

DC Potential

Elastic Unloading

Deformation J (kJ/m2)

Crack Extension (mm)

CF–8M (Specimen 75–03T)

Aged 10,000 h at 400°C

288°C

0

100

200

300

400

500

0 0.5 1 1.5 2 2.5 3 3.5

DC Potential

Elastic Unloading

Deformation J (kJ/m2)

Crack Extension (mm)

CF–8M (Specimen 75–04T)

Aged 10,000 h at 400°C

288°C

(a) (b)

0

100

200

300

400

500

0 0.5 1 1.5 2 2.5 3 3.5

DC Potential

Elastic Unloading

Deformation J (kJ/m2)

Crack Extension (mm)

CF–8M (Specimen 75–10T)

Aged 10,000 h at 400°C

288°C

Figure 8.

Fracture toughness J–R curves obtained from DC

potential and elastic unloading compliance

methods for thermally aged Heat 75 of cast

CF–8M SS; specimen (a) 75–03T, (b) 75–04T,

and (c) 75–10T

(c)

0

100

200

300

400

500

0 0.5 1 1.5 2 2.5 3 3.5

DC Potential

Elastic Unloading

Deformation J (kJ/m2)

Crack Extension (mm)

Type 316NG SS (Specimen 184–38)

50% Cold Worked

288°C

0

100

200

300

400

500

0 0.5 1 1.5 2 2.5 3 3.5

DC Potential

Elastic Unloading

Deformation J (kJ/m2)

Crack Extension (mm)

Type 316NG SS (Specimen 184–40)

50% Cold Worked

288°C

(a) (b)

Figure 9. Fracture toughness J–R curves obtained from DC potential and elastic unloading compliance

methods for 50% cold–worked Type 316NG; specimen (a) 184–38 and (b) 184–40

The J–R curves obtained from 1/4–T CT specimens of thermally aged Heat 75 of CF–8M

cast SS are compared with those obtained from 1–T CT specimens of the same heat in Fig. 10.

The curves for the 1/4–T CT specimens show good agreement with the curve for the 1–T CT

specimen with the same orientation, e.g., transverse orientation.
11 

0

100

200

300

400

500

0 0.5 1 1.5 2 2.5 3 3.5

751-02T

75-03T

75-04T

75-10T

Deformation J (kJ/m2

)

Crack Extension (mm)

288°C, CF–8M (Heat 75)

Aged 10,000 h at 400°C

Open Symbols: 1/4–T CT

Closed Symbols: 1–T CT

Specimen #

Figure 10.

Fracture toughness J–R curves for 1/4–T and 1–T

CT specimens of aged Heat 75 of CF–8M cast

stainless steel at 288°C. The last digit in the

specimen number represents orientation; 

T = transverse.

2.2 Crack Growth Rate Tests

2.2.1 Procedure

All specimens were fatigue precracked in the test environment at temperature and load

ratio R = 0.2, a1 Hz frequency, and maximum stress intensity factor Kmax a15 MPa m1/2. After

a0.5–mm extension, R was increased incrementally to 0.7, and the loading waveform changed

to a slow/fast sawtooth with rise times of 30–1000 s. Constant–load tests were conducted with

the trapezoidal waveform, R = 0.7, 1– or 2–h hold period at peak, and either 4– or 24–s

unload/reload period. During individual test periods, Kmax was maintained approximately

constant by periodic load shedding (less than 2% decrease in load at any given time).

The stress intensity factor range DK was calculated as follows:

D D K P

BB W

a

W

a

W

f a

W N

=

( )

+ Ê

Ë

Á ˆ

 ̄

 ̃

- Ê

Ë

Á ˆ

 ̄

 ̃

Ê

Ë

Á ˆ

 ̄

 ̃ 12 32

2

1

/ / (9)

DPP P = - max min for R > 0 (10)

f a

W

a

W

a

W

a

W

a

W

Ê

Ë

Á ˆ

 ̄

 ̃ = + Ê

Ë

Á ˆ

 ̄

 ̃- Ê

Ë

Á ˆ

 ̄

 ̃ + Ê

Ë

Á ˆ

 ̄

 ̃ - Ê

Ë

Á ˆ

 ̄ 0 886 4 64 13 32 14 72 5 6  ̃

2 34

.. . . . . (11)

where Pmax and Pmin are maximum and minimum applied load, a is crack length, W is the

specimen width, and effective thickness Beff = (B BN)0.5. Also, because a modified configuration

of disc–shaped CT specimen was used in the present study, crack length was calculated from

Eq. 5 that was developed from the best fit of the experimental data for normalized crack length

and normalized DC potential.

Under cyclic loading, the CGR (m/s) can be expressed as the superposition of the rate in

air (i.e., mechanical fatigue) and the rates due to corrosion fatigue and SCC, given as

a a aa  ̇  ̇  ̇ ̇ env air cf scc = ++ . (12)
12

During crack growth tests in high–temperature water, environmental enhancement of CGRs

does not occur from the start of the test. Under more rapid cyclic loading, the crack growth is

dominated by mechanical fatigue. The CGRs during precracking and initial periods of cyclic

loading were primarily due to mechanical fatigue. For the present tests on irradiated SSs,

environmental enhancement typically was observed under loading conditions that would lead

to CGRs between 10-10 and 10–9 m/s in air. For Kmax values of 15–18 MPa m1/2, these values

correspond to a load ratio R ≥ 0.5 and rise time ≥ 30 s.

All tests were started in high–purity water that contained 250–300 ppb DO (i.e., NWC

BWR environment). The ECPs of a Pt electrode and a SS sample located at the exit of the

autoclave were monitored continuously during the test while the water DO level and

conductivity were determined periodically. After data were obtained for high–DO water, the DO

level in the feedwater was decreased to <30 ppb by sparging the feedwater with pure N2, and in

some cases, this was followed by sparging with N2 + 5% H2 [to simulate hydrogen water

chemistry (HWC) BWR environment]. Because of the very low water flow rates, it took several

days for the environmental conditions to stabilize. In general, the changes in ECP of the SS

sample were slower than in the ECP of the Pt electrode.

After the test the final crack size was marked by fatigue cycling in air at room

temperature. The specimens were then fractured, and the fracture surface of both halves of

the specimen was photographed with a telephoto lens through the hot cell window. The final

crack length of each half of the fractured specimen was measured from the photograph by the

9/8 averaging technique.

2.2.2 Data Qualification

The ASTM specifications for specimen K/size criteria are intended to ensure applicability

and transferability of the cracking behavior of a component or specimen of a given thickness

under a specific loading condition to a crack associated with a different geometry, thickness,

and loading condition.

The CGR test results were validated in accordance with the specimen size criteria of

ASTM E 1681 and E 647. These criteria require that the plastic zone at the tip of a fatigue

crack is small relative to the specimen geometry. For constant load tests, ASTM E 1681

requires that

Beff and (W–a) ≥2.5 (K/sys)

2, (13)

and for cyclic loading ASTM 647 requires that

(W–a) ≥(4/p) (K/sys)

2, (14)

where K is the applied stress intensity factor, and sys is the yield stress of the material. For

tests on irradiated material, side grooved specimens are strongly recommended, with a depth

for each side groove between 5 and 10% of the specimen thickness. The effective thickness Beff

of side–grooved specimen should be calculated as a root mean square, i.e., (B·BN)

0.5. In

high–temperature water, because the primary mechanism for crack growth during continuous

cycling is not mechanical fatigue, Eq. 13 is probably the more appropriate criterion, but Eq. 14

may give acceptable results. For high–strain hardening materials, i.e., materials with an
13 

ultimate to yield stress ratio (sult/sys) ≥1.3, both criteria allow the use of the flow stress defined

as sf = (sult + sys)/2 rather than the yield stress.

The K/size criteria were developed for materials that show work hardening and, therefore,

may not be valid for materials irradiated to fluence levels where, on a local level, they do not

strain harden. This lack of strain hardening, or strain softening, is most dramatic when

dislocation channeling occurs but may also occur at lower fluences. For moderate to highly

irradiated material, it has been suggested that an effective yield stress, defined as the average

of the nonirradiated and irradiated yield stresses, be used;34 this discounts the

irradiation–induced increase in yield stress by a factor of 2. This modification of the K/size

criteria has been used in the current analysis.

2.2.3 Effect of Specimen Size

Several CGR tests were conducted on thermally aged CF–8M cast SS and on a 50% CW

Type 316LN SS in BWR environments to establish the test procedures and determine the

possible effect of specimen size. The experimental CGRs for the materials in water and those

predicted in air for the same loading conditions are plotted in Fig. 11. The results obtained

earlier on a 1–T CT specimen of the same heat of 50% CW Type 316LN SS and Heat 75 of

CF8M cast SS in high–DO water are also included in the figure.35 The CGRs in air, a ̇air (m/s),

were determined from the correlations developed by James and Jones;36 it is expressed as

a ̇air = CSS S(R) DK3.3/TR , (15)

where R is the load ratio (Kmin/Kmax), DK is Kmax – Kmin in MPa m1/2, TR is the rise time (s) of

the loading waveform, and function S(R) is expressed in terms of the load ratio R as follows:

S(R) = 1.0 R <0

S(R) = 1.0 + 1.8R 0 <R <0.79

S(R) = -43.35 + 57.97R 0.79 <R <1.0, (16)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-13 10-12 10-11 10-10 10-9 10-8 10-7

Heat 4331, 1/4-T CT

700 h at 400°C

Heat 75, 1-T CT

10,000 h at 400°C or

30,000 h at 350°C

Heat 75 1/4-T CT

10,000 h at 400°C

8 ppm DO

0.3 ppm DO

CGR env (m/s)

CGRair (m/s)

CF8M Cast SS

289°C 

Open Symbols: 

a0.3 ppm DO

Closed Symbols: 

a4.0 ppm DO

Shack/Kassner Model for

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-13 10-12 10-11 10-10 10-9 10-8 10-7

1/4-T CT, a0.55 ppm DO

1-T CT, a7.7 ppm DO

1/4 T-CT , <0.04 ppm DO

8 ppm DO

0.3 ppm DO

CGRenv (m/s)

CGRair (m/s)

50% Cold Worked

Type 316LN SS

289°C

Shack/Kassner Model for

Figure 11. Crack growth rate data under continuous cycling for thermally aged cast SS and 50%

cold–worked Type 316LN SS in high–purity water at 289°C.
14

and function CSS is given by a third–order polynomial of temperature T (°C), expressed as

CSS = 1.9142 x 10–12 + 6.7911 x 10–15 T – 1.6638 x 10–17 T2 + 3.9616 x 10–20 T3. (17)

The two curves in the figure represent the best–fit curves for sensitized austenitic SSs in

high–purity water at 289°C.35 The CGRs in water with a0.3 ppm DO are given by the

expression

a ̇env = a ̇air + 4.5 x 10-5 ( a ̇air)

0.5 (18)

and in water with a8 ppm DO by the expression

a ̇env = a ̇air + 1.5 x 10-4 ( a ̇air)0.5. (19)

The experimental CGRs for the 1/4–T CT specimen of Heat 4331 are in good agreement

with the data obtained on the 1–T CT specimen of Heat 75. The rates for the 1/4–T CT

specimen of Heat 75 and 50% CW Type 316LN SS are somewhat higher. However, the K/size

criteria were generally exceeded for these tests, i.e., the values of Kmax were higher than those

allowed by Eqs. 13 or 14.

For the 50% CW Type 316LN SS, the CGR under constant load conditions in high–DO

water at 289°C is plotted in Fig. 12; the maximum stress intensity for the test was within the

K/size–validity criteria. Data obtained earlier on 1–T CT specimens of several heats of

Types 304 and 316 SS are also included in the figure. In a250–ppb–DO water, the CGRs for a

1/4–T CT specimen of 50% CW Type 316LN SS are higher than those for a 1–T CT specimen of

sensitized Type 304 SS. Rates for the 1/4–T specimen are comparable to those of sensitized

Type 304 SS in very high–DO water (>6000 ppb DO).

10-12

10-11

10-10

10-9

10-8

0 10 20 30 40 50

304 SS Heat 30956 (Sensitized)

304 SS Heat 10285 (Sensitized)

316NG Heat P91576

50% CW 316LN Heat 18474

Experimental CGR (m/s)

Stress Intensity K (MPa·m1/2)

Austenitic SSs

High DO Environment

289°C

Open Symbols: a250 ppb DO

Closed Symbols: ≥6000 ppb DO

NUREG-0313

1-T CT Specimen

1/4-T CT Specimen

Figure 12.

Stress corrosion cracking data for austenitic

stainless steels in high–DO water at 289°C.
15 

3. Results

3.1 Fracture Toughness

3.1.1 Nonirradiated Type 304 Stainless Steel

The fracture toughness J–R curves for nonirradiated specimens of Heats L2, L20, C16,

and C19, obtained in air by the DC potential and elastic unloading compliance methods, are

shown in Figs. 13–16; experimental data for the tests are given in the Appendix. Duplicate

tests were conducted for Heats L2 and C16. The results indicate that the fracture toughness of

the laboratory Heats L2 and L20 is very low. The J–R curves are significantly lower than those

typically observed for Type 304 SSs, Fig. 17.15,38–41 For wrought austenitic SSs,3 the JIc

values at temperatures up to 550°C are typically >400 kJ/m2; experimental JIc for Heats L2

and L20 is in the range of 150–230 and 80–120 kJ/m2, respectively. The commercial Heats

C16 and C19 show the very high fracture toughnesses expected for Type 304 SSs. For both

steels, the J–R curve could not be obtained; the experimental curve is composed only of the

blunting line. Fracture toughness JIc is >830 kJ/m2 for C19, and it could not be determined

for Heat C16.

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2)

Crack Extension (mm)

J = 243Da0.27

JIC = 186 kJ/m2

288°C

DC Potential

Specimen L2-C

Nonirradiated

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

J = 283Da0.20

JIC = 237 kJ/m2

Closed Symbol: Measured Crack

288°C

Unloading Compliance

Specimen L2-C

Nonirradiated

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

J = 268Da0.49

JIC = 159 kJ/m2

288°C

DC Potential

Specimen L2-E

Nonirradiated

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

J = 275Da0.54

J

IC = 154 kJ/m2 Closed Symbol: 

Measured Crack

288°C

Unloading Compliance

Specimen L2-E

Nonirradiated

Figure 13. Fracture toughness J–R curve obtained by DC potential and unloading compliance methods

for nonirradiated specimens L2–C and L2–E of Heat L2 of Type 304 SS at 288°C.
16

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

J = 174Da 0.60

JIC = 78 kJ/m2

288°C

DC Potential

Specimen L20-D

Nonirradiated

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

J = 236Da0.56

J

IC = 119 kJ/m2

Closed Symbol: 

Measured Crack

288°C

Unloading Compliance

Specimen L20-D

Nonirradiated

Figure 14. Fracture toughness J–R curve obtained by DC potential and unloading compliance methods

for nonirradiated specimen L20–D of Heat L20 of Type 304 SS at 288°C.

0

200

400

600

800

1000

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

288°C

DC Potential

Specimen C16-C

Nonirradiated

0

200

400

600

800

1000

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

288°C

Unloading Compliance

Specimen C16-C

Nonirradiated

0

200

400

600

800

1000

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

288°C

DC Potential

Specimen C16-D

Nonirradiated

0

200

400

600

800

1000

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

288°C

Unloading Compliance

Specimen C16-D

Nonirradiated

Figure 15. Fracture toughness J–R curve obtained by DC potential and unloading compliance methods

for nonirradiated specimens C16–C and C16–D of Heat C16 of Type 316 SS at 288°C.
17 

0

200

400

600

800

1000

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

J

IC = 835 kJ/m2

288°C

DC Potential

Specimen C19-D

Nonirradiated

0

200

400

600

800

1000

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

288°C

Unloading Compliance

Specimen C19-D

Nonirradiated

Figure 16. Fracture toughness J–R curve obtained by DC potential and unloading compliance methods

for nonirradiated specimen C19–D of Heat C19 of Type 304 SS at 288°C.

0

500

1000

1500

2000

0 1 2345

Pipe

Plate

Deformation J (kJ/m2

)

Crack Extension (mm)

Type 304 SS

288°C

Figure 17.

Fracture toughness J–R curves for

nonirradiated Type 304 stainless steels at

288°C.

The differences between the fracture toughness of laboratory and commercial heats are

reflected in their fracture behavior. Photomicrographs of the fracture surface of broken

nonirradiated specimens of laboratory Heats L2 and L20 and commercial Heat C19 are shown

in Figs. 18 and 19, respectively. Heat L2 contains relatively high S and P contents and many

clusters of MnS inclusions. Failure occurs primarily via grain–boundary separation, which is

(a) (b)

Figure 18. Photomicrographs of fracture surfaces of nonirradiated specimens of Heats (a) L2 and

(b) L20 tested at 288°C.
18

accompanied by some plastic deformation and decohesion along the MnS clusters (Fig. 20).

Heat L20 exhibits a dimple fracture; failure occurs by nucleation and growth of microvoids and

rupture of remaining ligaments. Heat L20 contains relatively high oxygen and many oxide

particle inclusions. In Fig. 18b, nearly every dimple appears to have been initiated by

decohesion of an oxide inclusion. An identical fracture behavior was observed for Heat L20

irradiated to 0.9 x 1021 n◊cm–2 (1.35 dpa). In contrast, commercial heats exhibit ductile failure

with some dimple fracture, as shown for Heat C19 in Fig. 19.

Figure 19.

Photomicrograph of fracture surface of

nonirradiated specimen of Heat C19 tested at

288°C.

Figure 20.

Photomicrograph of MnS inclusions on the

fracture surface of nonirradiated specimen of

Heat L2 tested at 288°C.

3.1.2 Irradiated Type 304 Stainless Steels

Fracture toughness J–R curve tests were conducted at 288°C on Heats C19, L20, and L2

of Type 304 SS and Heat C16 of Type 316 SS irradiated to 2.0 x 1021 n◊cm–2 (E > 1 MeV)

(3.0 dpa). The J–R curves for the various steels are shown in Figs. 21–24; experimental data

for the tests are given in the Appendix. For specimen C19–C, the J–R curve could not be

determined from the DC potential method because of broken potential leads. Note that the

rather flat J–R curve determined for specimen C19–A most likely is due to the small specimen

size used in these tests; the maximum allowed J values were exceeded for the test.

Neutron irradiation at 288°C decreases the fracture toughness of all steels. In general,

fracture toughness of the commercial Heats C16 and C19 is superior to that of the laboratory

Heats L20 and L2. These differences arise primarily from differences in toughness of the

nonirradiated steels, i.e., the fracture toughness of the laboratory heats is significantly lower

than that of the commercial heats. The fracture toughness J–R curves for irradiated Types 304

and 316 SS are comparable.
19 

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

J = 579Da0.17

J

IC = 507 kJ/m2

288°C

DC Potential

Specimen C19-A

0.3 x 1021 n cm–2

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

J = 661Da0.15

JIC = 599 kJ/m2

Closed Symbol: Measured Crack

288°C

Unloading Compliance

Specimen C19-A

0.3 x 1021 n cm–2

(a)

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

J = 442Da 0.32

JIC = 313 kJ/m2

288°C

DC Potential

Specimen C19-B

0.9 x 1021 n cm-2

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

J = 513Da 0.33

JIC = 368 kJ/m2

Closed Symbol: Measured Crack

288°C

Unloading Compliance

Specimen C19-B

0.9 x 1021 n cm-2

(b)

Specimen C19–C – DC Potential method

Data not obtained

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

J = 268Da0.28

JIC = 188 kJ/m2

Closed Symbol: Measured Crack

288°C

Unloading Compliance

Specimen C19-C

2.0 x 1021 n cm-2

(c)

Figure 21. Fracture toughness J–R curve obtained by DC potential and unloading compliance methods

at 288°C for Heat C19 of Type 304 SS irradiated to a fluence level of (a) 0.3, (b) 0.9, and

(c) 2.0 x 1021 n/cm2.
20

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

Specimen C16-A

0.9 x 1021 n cm-2

J = 491Da0.45

J

IC = 315 kJ/m2

288°C

DC Potential

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

Specimen C16-A

0.9 x 1021 n cm-2

J = 607Da0.52

J

IC = 378 kJ/m2

Closed Symbol: Measured Crack

288°C

Unloading Compliance

Figure 22. Fracture toughness J–R curve obtained by DC potential and unloading compliance methods

at 288°C for Heat C16 of Type 316 SS irradiated to a fluence level of 0.9 x 1021 n/cm2.

0

50

100

150

200

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

Specimen L20-A

0.3 x 1021 n cm-2

J = 100Da0.34

J

IC = 62 kJ/m2

Closed Symbol: Measured Crack

288°C

Unloading Compliance

0

50

100

150

200

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

Specimen L20-A

0.3 x 1021 n cm-2

J = 104Da 0.36

J

IC = 62 kJ/m2

288°C

DC Potential

(a)

0

50

100

150

200

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

Specimen L20-B

0.9 x 1021 n cm-2

J = 55Da0.22

JIC = 39 kJ/m2

288°C

DC Potential

0

50

100

150

200

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

Specimen L20-B

0.9 x 1021 n cm-2

J = 45Da0.12

JIC = 37 kJ/m2

Closed Symbol: 

Measured Crack

288°C

Unloading Compliance

(b)

Figure 23. Fracture toughness J–R curve obtained by DC potential and unloading compliance methods

at 288°C for Heat L20 of Type 304 SS irradiated to a fluence level of (a) 0.3 and

(b) 0.9 x 1021 n/cm2.
21 

0

50

100

150

200

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

Specimen L2-A

0.9 x 1021 n cm-2

J = 52Da0.22

JIC = 38 kJ/m2

288°C

DC Potential

0

50

100

150

200

0 0.5 1 1.5 2 2.5 3 3.5

Deformation J (kJ/m2

)

Crack Extension (mm)

Specimen L2-A

0.9 x 1021 n cm-2

J = 51Da0.24

J

IC = 35 kJ/m2

Closed Symbol: 

Measured Crack

288°C

Unloading Compliance

Figure 24. Fracture toughness J–R curve obtained by DC potential and unloading compliance methods

at 288°C for Heat L2 of Type 304 SS irradiated to a fluence level of 0.9 x 1021 n/cm2.

The experimental JIc values for the two commercial heats of austenitic SSs are plotted as

a function of neutron exposure in Fig. 25. Results from tests on Type 304 SS reactor internal

materials from operating BWRs2 are also included in the figure. All CT specimen data from

commercial heats fall within the scatter band for the data obtained at temperatures higher

than 288°C.

0

100

200

300

400

500

600

0 5 10 15 20 25

C19

C16

Bend Bar

CT Specimen

Short Rod

CT Specimen

JIc (kJ/m2)

Neutron Exposure (dpa)

Types 304 SS

Irradiation Temp: 288°C

Test Temp: 288°C

ANL Heats

JAPEIC Data

GE Data

835 kJ/cm2

Figure 25.

Fracture toughness JIc of austenitic stainless

steels as a function of neutron exposure at

288°C. Dashed lines represent upper and

lower bounds for change in JIc for austenitic

SSs irradiated at 350–450°C. 

JAPEIC = Japan Power Engineering and

Inspection Corporation, GE = General Electric

Nuclear Energy

3.2 Crack Growth Tests on Irradiated Stainless Steels in BWR Environments

Crack growth tests have been completed at 289°C on 1/4–T CT specimens of Type 304 SS

(Heat C3) irradiated to 0.3, 0.9, and 2.0 x 1021 n/cm2 and Type 316 SS (Heat C16) irradiated

to 2.0 x 1021 n/cm2. The significant results for the various tests are summarized below.
22

3.2.1 Specimen C3-B Irradiated to 0.9 x 1021 n/cm2

The environmental and loading conditions, experimental CGRs, allowed Kmax from K/size

criterion in Eq. 13, and the deviation of applied Kmax from the allowed value are given in

Table 3. Allowed Kmax was determined using effective yield stress in Eq. 13. Precracking was

initiated at R = 0.2 and Kmax = 16 MPa m1/2. During most test periods, Kmax was maintained

approximately constant by periodic load shedding.

Table 3. Crack growth results for Specimen C3–B of Type 304 SSa in high–purity water at 289°C

Test

Test

Time,

ECP

mV (SHE)b

O2

Conc.,

b Load

Rise

Time,

Down

Time,

Hold

Time, Kmax, DK,

Growth

Rate,

Kmax from

Eq. 13

Deviation

in Kmax,

Period h Pt Steel ppb Ratio s s s MPa·m1/2MPa·m1/2 m/s MPa m1/2 %

1 28 230 154 300 0.20 0.5 0.5 0 19.14 15.31 6.83E-08 18.4 4

2 172 239 189 300 0.51 60 2 0 18.96 9.29 1.75E-10 18.3 3

3 287 233 187 300 0.70 300 2 0 19.79 5.94 6.38E-10 18.0 10

4 335 235 191 300 0.70 2 2 7200 20.10 0 1.06E-09 17.7 14

5 376 238 195 300 0.70 2 2 7200 22.07 0 1.04E-09 17.4 27

6 624 -475 –595 a10 0.70 2 2 7200 22.27 0 4.02E-11 17.2 30

7 696 -482 –607 a10 0.70 300 2 0 22.10 6.63 8.56E-11 17.1 29

8 935 -495 –614 a10 0.70 2 2 3600 22.66 0 6.42E-12 17.1 32

9 1031 -499 –609 a10 0.70 300 2 0 22.53 6.76 3.37E-11 17.1 32

10a 1127 -495 –613 a10 0.70 1000 2 0 22.19 6.66 negligible 17.1 30

10b 1271 -507 –620 a10 0.70 1000 2 0 23.04 6.91 1.20E-11 17.1 35

11 1295 -507 –624 a10 0.70 30 2 0 22.87 6.86 5.17E-11 17.1 34

12 1343 -498 –617 a10 0.70 300 2 0 23.10 6.93 1.55E-11 17.1 36

14 1608 248 151 250 0.70 1000 2 0 24.17 7.25 5.93E-10 16.7 45

15 1655 244 155 250 0.70 2 2 3600 24.42 0 8.70E-10 16.4 49

a Heat C3, irradiated to 0.9 x 1021 n cm-2. bRepresents values in the effluent.

Conductivity was 0.07 and 0.3–0.45 mS/cm in feedwater and effluent, respectively. Feedwater pH at room

temperature was 6.5.

The test was initiated in high–purity water with a300 ppb DO. After a375 h, the DO level

in the feedwater was decreased to a10 ppb by sparging it with pure nitrogen. After 1380 h, the

DO level was increased from a10 to a300 ppb by sparging the feedwater with nitrogen plus 1%

oxygen gas mixture. Because of the very low flow rates for the recirculating water system it

took several days for the environmental conditions to stabilize. Changes in crack length and

ECP of Pt and SS electrodes during these transient periods are shown in Fig. 26. During the

transition periods, changes in the steel ECP were slower than those in the Pt ECP. For

example, in Fig. 26a, although the Pt ECP decreased below –400 mV (SHE) within 40 h, it took

more than 150 h for the steel ECP to decrease below –400 mV. Also, because of an unexpected

power bump the test tripped after a1390 h (during the second transition period); it was

restarted at 1470 h. The ECPs of both electrodes were below –200 mV before the interruption

and above 100 mV after the test was restarted.

A photomicrograph of the fracture surface of both halves of the specimen is shown in

Fig. 27. The final crack length, determined from the photograph, showed very good agreement

with the value estimated from the DC potential measurements. Changes in crack length and

Kmax with time during various test periods are shown in Fig. 28a–e. In general, the DC

potential measurements show very little scatter, particularly for measured growth rates

>5 x 10–11 m/s. Some fluctuations in DC potential measurements were observed when either

the autoclave temperature varied ±3°C (e.g., 170–260 h) or the DO level in the water was being

changed (e.g., 450–530 h and 1370–1510 h).
23 

7.30

7.35

7.40

7.45

7.50

7.55

7.60

-800

-600

-400

-200

0

200

400

350 400 450 500 550 600 650

Crack Length

Pt ECP

Steel ECP

Crack Length (mm)

ECP [mV (SHE)]

Time (h)

Type 304 SS (Heat C3)

Test CGRI–07 (Spec. C3-B)

Fluence 0.9 x 1021 n/cm2

289°C

High–Purity Water

DO <30 ppb

CGR= 4.02 x 10-11 m/s

Kmax = 22.3 MPa m0.5

R = 1.0

(a)

7.50

7.55

7.60

7.65

7.70

7.75

7.80

-800

-600

-400

-200

0

200

400

1350 1400 1450 1500 1550 1600

Crack Length

Pt ECP

Steel ECP

Crack Length (mm)

ECP [mV (SHE)]

Time (h)

Type 304 SS (Heat C3)

Test CGRI–07 (Spec. C3-B)

Fluence 0.9 x 1021 n/cm2

289°C

High–Purity Water

DO changed from a10 to 250 ppb

(b)

Figure 26. Changes in crack length and ECP after the dissolved oxygen level in the feedwater was

(a) decreased from a500 to 10 ppb and (b) increased from a10 to 300 ppb

Figure 27. Photomicrographs of the fracture surface of specimen C3–B

tested in high–purity water at 289°C
24

6.6

6.8

7.0

7.2

7.4

15

20

25

30

35

100 150 200 250 300 350 400

Crack Length (mm)

Kmax (MPa m0.5)

Time (h)

Type 304 SS (Heat C3)

Test CGRI–07 (Spec. C3-B)

Fluence 0.9 x 1021 n/cm2

289°C

High–Purity Water

CGR = 1.75 x 10–10 m/s

Kmax = 19.0 MPa m0.5

R = 0.5, Rise Time 60 s

K Crack Length max DO a250 ppb

Steel ECP 190 mV (SHE)

DO <30 ppb

1.06 x 10 –9 m/s

20.1 MPa m0.5

R = 1.0

1.04 x 10 –9 m/s

22.1 MPa m0.5

R = 1.0

CGR = 6.38 x 10–10 m/s

Kmax = 19.8 MPa m0.5

R = 0.7, Rise Time 300 s

Constant Load

Unload to R = 0.7 every 2 h

(a)

7.40

7.45

7.50

7.55

7.60

15

20

25

30

35

480 520 560 600

Crack Length (mm)

Kmax (MPa m0.5)

Time (h)

Type 304 SS (Heat C3)

Test CGRI–07 (Spec. C3-B)

Fluence 0.9 x 1021 n/cm2

289°C

High–Purity Water, DO <30 ppb

Steel ECP –300 to –600 mV (SHE)

K Crack Length max

CGR = 4.02 x 10–11 m/s

Kmax = 22.3 MPa m0.5

R = 1.0

(b)

7.45

7.50

7.55

7.60

15

20

25

30

35

600 650 700 750 800 850 900 950

Crack Length (mm)

Kmax (MPa m0.5)

Time (h)

Type 304 SS (Heat C3)

Test CGRI–07 (Spec. C3-B)

Fluence 0.9 x 1021 n/cm2

289°C

High–Purity Water, DO a10 ppb

Steel ECP –610 mV (SHE)

Kmax

Crack Length

CGR = 8.56 x 10–11 m/s

Kmax = 22.1 MPa m0.5

CGR = 6.42 x 10–12 m/s

Kmax = 22.7 MPa m0.5

Constant Load R = 1.0 R = 0.7 Unload to R = 0.7 every 1 or 2 h

Rise Time 300 s

(c)

Figure 28. Crack–length–vs.–time plots for irradiated Type 304 SS (Heat C3) in high–purity water at

289°C during test periods (a) 2–5, (b) 6, (c) 7–8, (d) 9–12, and (e) 14–15
25 

7.50

7.52

7.54

7.56

7.58

7.60

15

20

25

30

35

1000 1100 1200 1300 1400

Crack Length (mm)

Kmax (MPa m0.5)

Time (h)

Type 304 SS (Heat C3)

Test CGRI–07 (Spec. C3-B)

Fluence 0.9 x 1021 n/cm2

289°C

High–Purity Water DO a10 ppb

Steel ECP –610 mV (SHE)

K Crack Length max

 3.37 x 10–11 m/s

22.6 MPa m0.5

0.7, 300 s

1.55 x 10–11 m/s

23.1 MPa m0.5

0.7, 300 s

5.17 x 10–11 m/s

22.9 MPa m0.5

0.7, 30 s

CGR = 1.20 x 10–11 m/s

Kmax = 23.1 MPa m0.5

R = 0.7, Rise Time = 1000 s

no growth

22.2 MPa m0.5

0.7, 1000 s

(d)

7.50

7.60

7.70

7.80

7.90

8.00

15

20

25

30

35

1500 1550 1600 1650

Crack Length (mm)

Kmax (MPa m0.5)

Time (h)

Type 304 SS (Heat C3)

Test CGRI–07 (Spec. C3-B)

Fluence 0.9 x 1021 n/cm2

289°C

High–Purity Water DO a250 ppb

Steel ECP 155 mV (SHE)

Kmax

Crack Length

8.70 x 10 –10 m/s

24.4 MPa m0.5

CGR = 5.93 x 10–11 m/s

Kmax = 24.2 MPa m0.5

Constant load 

Unload to R = 0.7 every 1 h R = 0.7

Rise Time = 1000 s

(e)

Figure 28. (Cont’d.)

For this specimen, environmental enhancement occurred after a170 h (Fig. 28a), when

the load ratio and rise time, respectively, were changed from 0.5 and 60 s to 0.7 and 300 s.

For the new loading condition, although the predicted CGR in air decreased by a factor of a15

(Eqs. 15–17), the measured rate in the environment increased by a factor of a3. The results

indicate the benefit of low–DO environment on growth rates; CGRs decreased by more than an

order of magnitude when the DO level was decreased to <10 ppb and increased when the DO

level was raised back to a300 ppb.

The results also suggest a possible effect of loading history on growth rates, e.g., during

test periods 6 and 8, the CGRs under the same trapezoidal waveform were 4.0 x 10–11 and

6.4 x 10–12 m/s, respectively. The higher rate was observed following a long period of growth

at a higher ECP under a trapezoidal waveform. The lower rate was observed following cycling

under a sawtooth waveform with a 300–s rise time at low DO. It is possible that the cyclic

loading changed the mode of fracture. The reason for such apparent differences in CGRs

under similar loading conditions will be investigated by metallographic evaluation of the

fracture surfaces; if a transition in fracture mode is observed, additional precautions to avoid

such transitions will be observed in future tests.
26

For specimen C3–B, during Test Periods 1–4 the experimental Kmax values were 4–14%

higher than the allowable value based on the effective yield stress and 30–50% higher during

Periods 5–15. For this specimen, loading conditions for all test periods would satisfy the K/size

criterion of Eq. 13 if the actual yield stress instead of effective yield stress is used. The

crack–length–vs.–time plots in Figs. 26a and 28a and b show that environmental factors still

strongly influenced the CGR at these K levels. For example, the CGRs decreased by a factor of

a20 when the DO level was decreased from a300 to 10 ppb. Thus in this case, it is not clear

that the violation of the K size criterion after Test Period 3 actually led to a significant loss of

specimen constraint.

3.2.2 Specimen C3-C Irradiated to 2.0 x 1021 n/cm2

The environmental and loading conditions, experimental CGRs, allowed Kmax from K/size

criterion in Eq. 13, and the deviation of applied Kmax from the allowed value are given in

Table 4. Allowed Kmax was determined using effective yield stress. Precracking was carried out

at R = 0.3 and Kmax = 17 MPa m1/2; the applied Kmax was maintained approximately constant

during individual test periods by periodic load shedding. The test was initiated in high–purity

water with a300 ppb DO. After a240 h, the DO level in the feedwater was decreased to a10 ppb

by sparging the feedwater tank first with pure nitrogen and then with nitrogen plus 5%

hydrogen. The changes in crack length and ECP of Pt and SS electrodes during the transient

period are shown in Fig. 29. As seen earlier for Specimen C3–B, it took several days for the DO

level to decrease below 20 ppb, and changes in the steel ECP were slower than that in the Pt

ECP. For example, the Pt ECP decreased to –450 mV (SHE) within a couple of days while the

steel ECP remained above –250 mV for a long time; it decreased below –400 mV only after the

feedwater tank was sparged with nitrogen plus 5% hydrogen gas mixture. The test was

terminated after 810 h because the range of valid Kmax was significantly exceeded.

Table 4. Crack growth results for Specimen C3–C of Type 304 SSa in high–purity water at 289°C

Test

Test

Time,

ECP

mV (SHE)b

O2

Conc.,

b Load

Rise

Time,

Down

Time,

Hold

Time, Kmax, DK,

Growth

Rate,

Kmax from

Eq. 13

Deviation

in Kmax,

Period h Pt Steel ppb Ratio sss MPa·m1/2 MPa·m1/2 m/s MPa m1/2 %

1 46 241 164 300 0.26 2 2 0 17.89 13.24 2.00E-08 22.4 -20

2 71 223 155 300 0.53 30 2 0 18.40 8.65 2.22E-09 22.1 -17

3 99 235 167 300 0.70 300 2 0 18.80 5.64 1.73E-09 21.8 -14

4 142 232 164 300 0.69 1000 2 0 19.21 5.96 1.25E-09 21.4 -10

5 191 233 164 300 0.70 2 2 3600 19.42 0 6.83E-10 21.1 -8

6 311 -450 7 100 0.70 2 2 3600 23.67 0 5.07E-10 20.5 16

7 560 -547 -294 10 0.70 2 2 3600 27.49 0 6.91E-10 19.1 44

8 706 -551 -502 10 0.70 2 2 3600 34.74 0 2.04E-09 16.4 111

9 724 -557 -457 10 0.70 2 2 3600 36.96 0 3.70E-09 15.8 134

aHeat C3, irradiated to 2.0 x 1021 n/cm2. bRepresents values in the effluent.

Conductivity was 0.07 and 0.3–0.45 mS/cm in feedwater and effluent, respectively. Feedwater pH at room

temperature was 6.5.

A photomicrograph of the fracture surface of both halves of the specimen is shown in

Fig. 30. The final crack length was determined from the photograph of both halves of the

fractured specimen. Several unbroken ligaments can be seen extending back from the final

crack front. Because of these unbroken ligaments the crack lengths were determined from an

average of 16 evenly spaced measurements. A total 17 measurements were made, the two

near–surface measurements were averaged, and the resultant value was averaged with the

remaining 15 measurements. The actual crack extension was a40% greater than the value
27 

determined from the DC potential measurements. This difference is larger than is typically

observed in most of our CGR tests, and is most likely due to the presence of the unbroken

ligaments. Crack extensions estimated from the DC potential method were scaled

proportionately. The values given in Table 4 are the corrected values of Kmax and growth rate.

The changes in the (corrected) crack length and Kmax with time during various test

periods are shown in Figs. 31a–d. For this specimen, significant environmental enhancement

occurred after a100 h (Fig. 31b) during continuous cycling at R = 0.7 when the rise time was

changed from 30 s to 300 s. For the new loading condition, although the predicted CGR in air

decreased by a factor of a10, the rate in water did not change.

Figure 30. Photomicrographs of the fracture surface of Specimen C3–C

Figures 29 and 31c show that when the DO level was decreased from a300 to 10 ppb, the

steel ECP decreased from a240 to -255 mV (SHE), but the CGR did not decrease. For a similar

decrease in DO, the CGR of specimen C3–B, irradiated to 0.9 x 1021 n/cm2, decreased by more

than an order of magnitude. For specimen C3–C, the CGR actually increased at a570 h when

the cover gas was changed from pure nitrogen to nitrogen plus 5% hydrogen and the steel ECP

decreased below –500 mV (Fig. 31d). However, during the whole time at low ECP, the specimen

K/size criteria were exceeded. Thus the apparent absence of a beneficial effect of reduced DO

content on growth rates thus may be a test artifact.

7.40

7.60

7.80

8.00

8.20

8.40

8.60

-800

-600

-400

-200

0

200

400

200 300 400 500 600

Crack Length

Pt ECP

Crack Length (mm)

Steel ECP

ECP [mV (SHE)]

Time (h)

Type 304 SS (Heat C3)

Test CGRI–08 (Spec. C3-C)

Fluence 2.0 x 1021 n/cm2

289°C

High–Purity Water

Constant Load

periodic unloading 

to R = 0.7 every 1 h

<80 ppb DO

<20 ppb DO

a400 ppb DO

N2 + 5% H2

Figure 29. Change in crack length and ECP of Pt and SS electrodes for Specimen C3–C after the

dissolved oxygen level in the feedwater was decreased from a300 to 10 ppb
28

6.00

6.20

6.40

6.60

6.80

7.00

5

10

15

20

25

30

20 30 40 50 60 70 80

Crack Length (mm)

K

max (MPa m0.5)

Time (h)

Type 304 SS (Heat C3)

Test CGRI–08 (Spec. C3-C)

Fluence 2.0 x 1021 n/cm2

289°C

High–Purity Water, DO a300 ppb

Steel ECP 165 mV (SHE)

Kmax

Crack Length

CGR = 2.00 x 10–8 m/s

Kmax = 17.9 MPa m0.5

R = 0.26, Rise Time 2 s

CGR = 2.22 x 10–9 m/s

Kmax = 18.4 MPa m0.5

R = 0.53, Rise Time 30 s

(a)

6.80

6.90

7.00

7.10

7.20

7.30

7.40

5

10

15

20

25

30

80 100 120 140 160 180

Crack Length (mm)

K

max (MPa m0.5)

Time (h)

Type 304 SS (Heat C3)

Test CGRI–08 (Spec. C3-C)

Fluence 2.0 x 1021 n/cm2

289°C

High–Purity Water, DO a300 ppb

Steel ECP 165 mV (SHE)

Kmax

Crack Length

CGR = 1.25 x 10–9 m/s

Kmax = 19.2 MPa m0.5

R = 0.69, Rise Time 1000 s

CGR = 1.73 x 10–9 m/s

Kmax = 18.8 MPa m0.5

R = 0.70, Rise Time 300 s

CGR = 6.83 x 10–10 m/s

Kmax = 19.4 MPa m0.5

Constant load, periodic unload 

to R = 0.7 every 1 h

(b)

7.20

7.40

7.60

7.80

8.00

8.20

20

25

30

35

40

45

200 240 280 320 360 400 440 480 520

Crack Length (mm)

K

max (MPa m0.5)

Time (h)

Type 304 SS (Heat C3)

Test CGRI–08 (Spec. C3-C)

Fluence 2.0 x 1021 n/cm2

289°C

Constant Load, periodic unloading

 to R = 0.7 every 1 h Kmax

Crack Length

CGR = 6.91 x 10–10 m/s

Kmax = 27.5 MPa m0.5

Steel ECP -294 mV (SHE)

5.07 x 10–10 m/s

23.7 MPa m0.5

Steel ECP 165 – 10 mV (SHE)

a400 ppb DO

a80 ppb DO a20 ppb DO

(c)

Figure 31. Crack–length–vs.–time plots for irradiated Type 304 SS (Heat C3) in high–purity water at

289°C during test periods (a) 1–2, (b) 3–5, (c) 6–7, and (d) 7–8
29 

7.80

8.00

8.20

8.40

8.60

8.80

9.00

9.20

9.40

20

25

30

35

40

45

450 500 550 600 650 700

Crack Length (mm)

K

max (MPa m0.5)

Time (h)

Type 304 SS (Heat C3)

Test CGRI–08 (Spec. C3-C)

Fluence 2.0 x 1021 n/cm2

289°C

High–Purity Water a10 ppb DO

Constant Load, periodic unloading

 to R = 0.7 every 1 h

Kmax

Crack Length

N2 + 5% H2

Pure N2

CGR = 6.91 x 10–10 m/s

Kmax = 27.5 MPa m0.5

Steel ECP -254 mV (SHE)

CGR = 2.04 x 10–9 m/s

Kmax = 34.7 MPa m0.5

Steel ECP -502 mV (SHE)

(d)

Figure 31. (Cont’d.)

3.2.3 Specimen C16-B Irradiated to 2.0 x 1021 n/cm2

The environmental and loading conditions, experimental CGRs, allowed Kmax from K/size

criterion in Eq. 13, and the deviation of applied Kmax from the allowed value are given in

Table 5. Allowed Kmax was determined using effective yield stress in Eq. 13. Precracking was

initiated at R = 0.3 and Kmax = 14 MPa m1/2. After a0.4 mm advance, R was increased

incrementally to 0.7, and rise time increased to 30 s. The maximum stress intensity factor

Kmax was maintained approximately constant by periodic load shedding. After a265 h, the DO

level in the feedwater was decreased from a250 ppb to <30 ppb by sparging the feedwater tank

initially with pure nitrogen and then with nitrogen plus 5% hydrogen gas mixture. After 780 h,

Table 5. Crack growth results for Specimen C16–B of Type 316 SSa in high–purity water at 289°C

Test

Test

Time,

ECP b

mV (SHE)

O2

Conc.,

b Load

Rise

Time,

Down

Time,

Hold

Time, Kmax, DK,

Growth

Rate,

Kmax from

Eq. 13

Deviation

in Kmax,

Period h Pt Steel ppb Ratio sss MPa·m1/2 MPa·m1/2 m/s MPa m1/2 %

Pre a 6– – 250 0.32 1 1 0 14.3 9.8 1.75E-08

Pre b 30 232 144 250 0.30 2 2 0 14.0 9.8 7.54E-09

Pre c 52 227 144 250 0.31 2 2 0 14.2 9.8 8.94E-09

1 94 224 148 250 0.56 12 2 0 14.6 6.4 4.94E-10 22.2 -35

2 132 226 147 250 0.73 30 2 0 14.8 4.0 8.65E-10 22.0 -33

3 173 228 151 250 0.71 300 2 0 15.0 4.4 8.16E-10 21.8 -31

4 198 224 153 250 0.70 1000 12 0 15.0 4.5 7.33E-10 21.7 -31

5 265 162 117 250 0.70 12 12 3600 15.2 0 4.62E-10 21.4 -29

6 410 -547 -298 <30 0.70 12 12 3600 15.2 0 1.90E-11 21.3 -28

7 504 -562 -410 <30 0.70 1000 12 0 15.2 4.54 2.76E-11 21.3 -29

8 527 -560 -449 <30 0.73 30 2 0 15.2 4.10 6.07E-11 21.3 -29

9 552 -557 -502 <30 0.70 30 2 0 17.3 5.18 2.51E-10 21.2 -18

10 600 -554 -545 <30 0.69 1000 12 0 17.2 5.34 3.59E-11 21.2 -19

11 672 -557 -554 <30 0.70 12 12 3600 17.3 0 1.73E-11 21.1 -18

12 792 -438 -597 <30 0.70 12 12 3600 19.7 0 4.11E-11 21.1 -7

13 866 219 139 250 0.70 12 12 3600 19.6 0 7.14E-10 21.0 -7

14 871 224 148 250 0.70 12 12 3600 21.9 0 1.10E-09 20.9 5

15 888 224 148 250 1.00c 0 0 – 21.9 – 5.27E-10 20.9 5

aHeat C16, irradiated to 2.0 x 1021 n/cm2. bRepresents values in the effluent. Effluent conductivity was a0.45 mS/cm and DO was a250 ppb during high–DO test

and <40 ppb during low–DO test. Feedwater conductivity was 0.07 mS/cm and pH at room temperature was 6.5. cConstant displacement test.
30

the DO level was increased back to a250 ppb by sparging the feedwater with nitrogen plus 1%

oxygen. Change in crack length and ECP of Pt and SS electrodes during the transient periods

are shown in Fig. 32. In both cases, it took more than 100 h for the changes to occur.

A photomicrograph of the fracture surface of both halves of the specimen is shown in

Fig. 33. The final crack length, determined from the photograph, showed very good agreement

with the value estimated from the DC potential measurement. Also, the results in Table 5

indicate that for specimen C16–B, loading conditions for all test periods satisfied the K/size

criterion of Eq. 13.

The changes in corrected crack length and Kmax with time during various test periods are

shown in Figs. 34a–g. For this specimen, environmental enhancement occurred at a150 h

(Fig. 34b) during continuous cycling at R = 0.7 when the rise time was changed from 30 s to

300 s. For the new loading condition, although the predicted CGR in air decreased by a factor

of a10, the rate in water did not change.

6.75

6.80

6.85

6.90

6.95

-800

-600

-400

-200

0

200

400

200 250 300 350 400

Crack Length

Pt ECP

Steel ECP

Crack Length (mm)

ECP [mV (SHE)]

Time (h)

Type 316 SS (Heat C16)

Test CGRI–09 (Spec. C16-B)

Fluence 2.0 x 1021 n/cm2

289°C, High–Purity Water

Constant Load. periodic

unloading to R = 0.7 every 1 h

Kmax = 15.2 MPa m1/2

CGR = 1.90 x 10-11 m/s

Steel ECP -300 mV (SHE)

Kmax = 15.2 MPa m1/2

CGR = 4.62 x 10-10 m/s

Steel ECP 150 mV (SHE)

250 ppb DO

<40 ppb DO

(a)

6.96

6.98

7.00

7.02

7.04

7.06

7.08

-800

-600

-400

-200

0

200

400

650 700 750 800 850

Crack Length

Pt ECP

Steel ECP

Crack Length (mm)

ECP [mV (SHE)]

Time (h)

Type 316 SS (Heat C16)

Test CGRI–09 (Spec. C16-B)

Fluence 2.0 x 1021 n/cm2

289°C, High–Purity Water

Constant Load. periodic

unloading to R = 0.7 every 1 h

Kmax = 19.6 MPa m1/2

CGR = 4.11 x 10-11 m/s

Steel ECP -590 mV (SHE) Kmax = 17.3 MPa m1/2

CGR = 1.73 x 10-11 m/s

Steel ECP -550 mV (SHE)

Kmax = 19.6 MPa m1/2

CGR = 7.14 x 10-10 m/s

Steel ECP 139 mV (SHE)

(b)

Figure 32. Change in crack length and ECP of Pt and SS electrodes when the DO level in feedwater

was (a) decreased from a300 to <40 ppb and (b) increased from <40 to a300 ppb.
31 

Figure 33. Photomicrographs of the fracture surface of Specimen C16–B

6.00

6.10

6.20

6.30

6.40

6.50

10

12

14

16

18

20

0 20 40 60 80 100

Crack Length (mm)

Kmax (MPa m0.5)

Time (h)

Type 304 SS (Heat C16)

Test CGRI–09 (Spec. C16-B)

Fluence 2.0 x 1021 n/cm2

289°C

High–Purity Water, DO a250 ppb

Steel ECP 165 mV (SHE)

Kmax

Crack Length

CGR = 1.75 x 10–9 m/s

Kmax = 14.3 MPa m0.5

R = 0.32, Rise Time 2 s

5.15 x 10–10 m/s

14.7 MPa m0.5

0.54, 12 s Rise

8.94 x 10–9 m/s

14.2 MPa m0.5

0.31, 2 s Rise

7.54 x 10–9 m/s

14.0 MPa m0.5

0.30, 2 s Rise

(a)

6.40

6.45

6.50

6.55

6.60

6.65

6.70

10

12

14

16

18

20

100 120 140 160 180

Crack Length (mm)

Kmax (MPa m0.5)

Time (h)

Type 304 SS (Heat C16)

Test CGRI–09 (Spec. C16-B)

Fluence 2.0 x 1021 n/cm2

289°C

High–Purity Water, DO a250 ppb

Steel ECP 165 mV (SHE)

Kmax

Crack Length

CGR = 8.65 x 10–10 m/s

Kmax = 14.8 MPa m0.5

R = 0.73, Rise Time 30 s

CGR = 8.16 x 10–10 m/s

Kmax = 15.0 MPa m0.5

R = 0.71, Rise Time 300 s

(b)

Figure 34. Crack–length–vs.–time plots for irradiated Type 316 SS (Heat C16) in high–purity water at

289°C during test periods (a) up to 1, (b) 2–3, (c) 4–5, (d) 6–7, (e) 8–10, (f) 11–12, and

(g) 13–15.
32

6.60

6.65

6.70

6.75

6.80

6.85

6.90

6.95

7.00

10

12

14

16

18

20

180 200 220 240 260 280

Crack Length (mm)

Kmax (MPa m0.5)

Time (h)

Type 304 SS (Heat C16)

Test CGRI–09 (Spec. C16-B)

Fluence 2.0 x 1021 n/cm2

289°C

High–Purity Water, DO a250 ppb

Steel ECP 165 mV (SHE)

Kmax

Crack Length

CGR = 7.32 x 10–10 m/s

Kmax = 15.0 MPa m0.5

R = 0.70, Rise Time 1000 s

CGR = 4.62 x 10–10 m/s

Kmax = 15.2 MPa m0.5

Constant Load, periodic unloading 

to R = 0.7 every 1 h

DO decreased 

to <30 ppb

(c)

6.84

6.86

6.88

6.90

6.92

6.94

10

12

14

16

18

20

300 350 400 450 500

Crack Length (mm)

Kmax (MPa m0.5)

Time (h)

Type 304 SS (Heat C16)

Test CGRI–09 (Spec. C16-B)

Fluence 2.0 x 1021 n/cm2

289°C

High–Purity Water, DO <40 ppb

Kmax

Crack Length

CGR = 2.76 x 10–11 m/s

Kmax = 15.1 MPa m0.5

R = 0.70, Rise Time 1000 s

CGR = 1.90 x 10–11 m/s

Kmax = 15.3 MPa m0.5

Constant Load, periodic unloading 

to R = 0.7 every 1 h

(d)

6.90

6.92

6.94

6.96

6.98

7.00

12

14

16

18

20

22

500 520 540 560 580 600

Crack Length (mm)

Kmax (MPa m0.5)

Time (h)

Type 304 SS (Heat C16)

Test CGRI–09 (Spec. C16-B)

Fluence 2.0 x 1021 n/cm2

289°C

High–Purity Water, DO <40 ppb

Steel ECP -500 mV (SHE)

Kmax

Crack Length

CGR = 3.59 x 10–11 m/s

Kmax = 17.2 MPa m0.5

R = 0.69, Rise Time 1000 s CGR = 2.51 x 10–10 m/s

Kmax = 17.3 MPa m0.5

 R = 0.70, Rise Time 30 s

CGR = 6.07 x 10–11 m/s

Kmax = 15.2 MPa m0.5

 R = 0.73, Rise Time 30 s

(e)

Figure 34. (Cont’d.)
33 

6.96

6.97

6.98

6.99

7.00

7.01

7.02

7.03

7.04

16

18

20

22

24

26

600 650 700 750 800

Crack Length (mm)

Kmax (MPa m0.5)

Time (h)

Type 304 SS (Heat C16)

Test CGRI–09 (Spec. C16-B)

Fluence 2.0 x 1021 n/cm2

289°C

High–Purity Water, DO <40 ppb

Steel ECP -580 mV (SHE)

Kmax

Crack Length

CGR = 4.11 x 10–11 m/s

Kmax = 19.7 MPa m0.5

Constant Load. periodic

unloading to R = 0.7 every 1 h

CGR = 1.73 x 10–11 m/s

Kmax = 17.3 MPa m0.5

Constant Load. periodic unloading to R = 0.7 every 1 h

(f)

7.00

7.05

7.10

7.15

16

18

20

22

24

26

780 800 820 840 860 880 900

Crack Length (mm)

Kmax (MPa m0.5)

Time (h)

Type 304 SS (Heat C16)

Test CGRI–09 (Spec. C16-B)

Fluence 2.0 x 1021 n/cm2

289°C, High–Purity Water

Kmax

Crack Length

CGR = 1.10 x 10–9 m/s

Kmax = 21.9 MPa m0.5

Constant Load. periodic unloading to R = 0.7 every 1 h

CGR = 7.14 x 10–10 m/s

Kmax = 19.6 MPa m0.5

Constant Load. periodic

unloading to R = 0.7 every 1 h

CGR = 5.27 x 10–10 m/s

Kmax = 21.9 MPa m0.5

Constant Displacement

(g)

Figure 34. (Cont’d.)

For this test, a change in loading conditions from continuous cycling to nearly constant

load (e.g., at 198 h), or an increase in applied Kmax (e.g., at 527 h), resulted in a transition

period of somewhat high CGRs; the growth rates gradually decrease later with time. At 527 h,

the increase in Kmax was accomplished by three load increments over a relatively short period

of a0.5 h. It resulted in a crack advance of a0.03 mm (Fig. 34e). To avoid such crack

advances, the increase in load at 675 h was achieved using a ramp loading with 2–h rise time

(Fig. 34f). The sudden increase in crack length was not observed with gradual increase in load.

In addition, the crack growth behavior with a decrease in DO differed distinctly from that

when the DO level was increased (Fig. 32a and b). With decreasing DO, the CGRs decreased by

a factor of about 25, but the change was relatively gradual, extending over 60 h. With

increasing DO, the growth rates increased abruptly from 4.11 x 10–11 to 7.14 x 10–10 m/s, a

factor of 17 increase in CGRs. The ECPs of both the Pt and steel electrodes were above 100 mV

at the time of this increase in growth rate.

Irradiated to the same fluence level as Type 304 SS specimen C3–C, the Type 316 SS

specimen C16–B clearly does show a benefit of reduced DO level on CGRs (Fig. 32a). The

growth rates decreased by more than an order of magnitude when DO was decreased from 250
34

to <30 ppb. Additional data will be obtained to establish the effect of decreased DO level on the

CGRs of irradiated austenitic SSs from testing samples from the Halden II irradiation.

3.2.4 Specimen C3-A Irradiated to 0.3 x 1021 n/cm2

The environmental and loading conditions, experimental CGRs, allowed Kmax from K/size

criterion in Eq. 13, and the deviation of applied Kmax from the allowed value are given in

Table 6. For this specimen, because the ultimate–to–yield stress ratio was >1.3 (Table 2),

effective flow stress instead of effective yield stress was used to determine the allowed Kmax

from Eq. 13. The test was started in a high–DO environment (a300 ppb DO in effluent), and

the water flow rate was a10 mL/min. The ECPs of Pt and SS electrodes in the effluent stream

were monitored continuously. Precracking was carried out at R = 0.3 and Kmax = 13–14 MPa

m1/2. After a0.3 mm crack advance, R was increased incrementally to 0.7, and the waveform

was changed from triangular to saw-tooth with rise times of 12–500 s.

A photomicrograph of the fracture surface of both halves of the specimen is shown in

Fig. 35. The final crack length, determined from the photograph, showed very good agreement

with the value estimated from the DC potential measurement. Also, the results in Table 6

indicate that for specimen C3–A, loading conditions for all test periods, except 11 and 12,

satisfied the K/size criterion of Eq. 13.

The changes in crack length and Kmax with time during various test periods are shown in

Figs. 36a–e. For this specimen, crack growth could not be maintained for loading conditions

with high values of R and relatively low Kmax. For example, at Kmax = 14 MPa m1/2 increasing

R from 0.3 to 0.5 essentially stopped crack growth (Fig. 36a). Changing R back to the earlier

value did not restore crack growth; Kmax had to be increased to start crack growth. To promote

environmentally enhanced crack growth, the rise time for the cyclic loading at R = 0.3 was

increased from 0.5 to 300 s before increasing R (Fig. 36b). For R = 0.7, crack growth occurred

only at Kmax greater than 17 MPa m1/2.

Table 6. Crack growth results for Specimen C3–A of Type 304 SSa in high–purity water at 289°C

Test

Test

Time,

ECP b

mV (SHE)

O2

Conc.,

b Load

Rise

Time,

Down

Time,

Hold

Time, Kmax, DK,

Growth

Rate,

Kmax from

Eq. 13

Deviation

in Kmax,

Period h Pt Steel ppb Ratio sss MPa·m1/2 MPa·m1/2 m/s MPa m1/2 %

Pre 55 226 167 300 0.31 0.5 0.5 0 12.9 8.9 2.94E-09 18.4 -30

1 165 212 166 300 0.30 0.5 0.5 0 14.0 9.8 8.37E-09 17.9 -22

2a 189 221 169 300 0.50 5 5 0 13.9 6.9 negligible 17.9 -23

2b 193 211 169 300 0.50 0.5 0.5 0 13.8 6.9 negligible 17.9 -23

2c 214 209 161 300 0.30 0.5 0.5 0 13.9 9.7 negligible 17.9 -23

2d 219 211 163 300 0.30 0.5 0.5 0 15.0 10.5 1.48E-08 17.7 -15

3 364 218 171 300 0.30 1 1 0 15.9 11.1 1.39E-08 17.5 -9

4 380 218 171 300 0.30 30 4 0 16.0 11.2 1.33E-09 17.4 -8

5 404 219 177 300 0.29 300 4 0 15.9 11.3 3.29E-10 17.4 -8

6 479 204 173 300 0.48 300 4 0 15.7 8.2 4.75E-11 17.4 -10

7 596 235 187 300 0.70 12 12 0 15.7 4.7 negligible 17.4 -10

8 670 228 188 300 0.70 12 12 0 17.6 5.3 6.23E-11 17.3 2

9 717 231 186 300 0.70 12 12 3600 17.8 – – 17.3 3

10 910 234 197 300 0.70 500 12 3600 17.9 – 8.65E-11 17.2 4

11 1080 232 200 300 0.70 500 12 3600 22.0 – 1.11E-10 17.1 29

12 1175 226 203 300 0.70 500 1 9500 22.3 – 1.28E-10 17.0 31

aHeat C3, irradiated to 2.0 x 1021 n/cm2. bRepresents values in the effluent. Conductivity was 0.07 and 0.3–0.45 mS/cm in feedwater and effluent, respectively.

Feedwater pH at room temperature was 6.5.
35 

Figure 35. Photomicrographs of the fracture surface of Specimen C3–A

6.00

6.10

6.20

6.30

6.40

6.50

6.60

10

12

14

16

18

20

140 160 180 200 220 240

Crack Length (mm)

K

max (MPa m0.5)

Time (h)

Type 304 SS (Heat C3)

Test CGRI–12 (Spec. C3-A)

Fluence 0.3 x 1021 n/cm2

289°C

High–Purity Water, DO a250 ppb

Steel ECP 170 mV (SHE)

Kmax

Crack Length

8.37 x 10–9 m/s

14.0 MPa m0.5

0.3, 1 Hz 13.9 MPa m0.5

0.5, 0.1 Hz

13.9 MPa m0.5

0.3, 1 Hz

13.8 MPa m0.5

0.5, 1 Hz

1.48 x 10–8 m/s

15.0 MPa m0.5

0.3, 1 Hz

14.1 MPa m0.5

0.5, Rise time 12 s

(a)

6.40

6.45

6.50

6.55

6.60

6.65

6.70

6.75

6.80

10

12

14

16

18

20

280 300 320 340 360 380 400

Crack Length (mm)

K

max (MPa m0.5)

Time (h)

Type 304 SS (Heat C3)

Test CGRI–12 (Spec. C3-A)

Fluence 0.3 x 1021 n/cm2

289°C

High–Purity Water, DO a300 ppb

Steel ECP 170 mV (SHE)

Kmax

Crack Length

1.39 x 10–8 m/s

15.9 MPa m0.5

0.3, 0.5 Hz

1.33 x 10–9 m/s

16.0 MPa m0.5

0.3, 30 s rise time

3.29 x 10–10 m/s

15.9 MPa m0.5

0.3, 300 s rise time

(b)

Figure 36. Crack–length–vs.–time plots for irradiated Type 316 SS (Heat C16) in high–purity water at

289°C during test periods (a) 1–2, (b) 3–5, (c) 6–7, (d) 8–10, and (e) 11–12.
36

6.60

6.65

6.70

6.75

6.80

6.85

6.90

10

12

14

16

18

20

400 450 500 550 600

Crack Length (mm)

K

max (MPa m0.5)

Time (h)

Type 304 SS (Heat C3)

Test CGRI–12 (Spec. C3-A)

Fluence 0.3 x 1021 n/cm2

289°C

High–Purity Water, DO a300 ppb

Steel ECP 180 mV (SHE)

Kmax

Crack Length 4.75 x 10–11 m/s

15.7 MPa m0.5

0.48, 300 s rise time

negligible growth

0.7, 12 s rise time

(c)

6.60

6.65

6.70

6.75

6.80

6.85

6.90

16

18

20

22

24

600 650 700 750 800 850 900

Crack Length (mm)

K

max (MPa m0.5)

Time (h)

Type 304 SS (Heat C3)

Test CGRI–12 (Spec. C3-A)

Fluence 0.3 x 1021 n/cm2

289°C

High–Purity Water, DO a250 ppb

Steel ECP 210 mV (SHE) Kmax

Crack Length

6.23 x 10–11 m/s

17.6 MPa m0.5

0.70, 12 s rise time

CGR not determined

17.9 MPa m0.5

0.70, 12 s rise time

3600 s hold

8.65 x 10U-11 m/s

17.9 MPa m0.5

0.70, 500 s rise time

3600 s hold

(d)

6.70

6.75

6.80

6.85

6.90

6.95

7.00

20

22

24

26

28

900 950 1000 1050 1100 1150 1200

Crack Length (mm)

K

max (MPa m0.5)

Time (h)

Type 304 SS (Heat C3)

Test CGRI–12 (Spec. C3-A)

Fluence 0.3 x 1021 n/cm2

289°C

High–Purity Water, DO a250 ppb

Steel ECP 218 mV (SHE) Kmax

Crack Length

1.11 x 10U-10 m/s

22.0 MPa m0.5

0.70, 500 s rise time

3600 s hold

1.13 x 10U-10 m/s

22.3 MPa m0.5

0.70, 500 s rise time

9500 s hold

(e)

Figure 36. (Cont’d)
37 

Crack growth rates could not be measured during test period 9 because of significant

variations in the autoclave temperature, which resulted in large fluctuations in the DC

potential measurements (Fig. 36d). Also, during test period 11 (Fig. 36e), applied Kmax

gradually decreased from the desired value of 22 to 20.5 MPa m1/2 over a 50–h period because

of faulty back–pressure regulator. Specimen C3–A irradiated to 0.3 x 1021 n/cm2 showed very

little environmental enhancement of CGRs both under continuous cycling and SCC conditions.

There was no change in CGR when the hold time was increased from 3600 to 9500 s (Fig. 36e

test period 11 and 12).

3.2.5 CGRs of Irradiated Austenitic SSs under Continuous Cycling

For continuous cyclic loading, the experimental CGRs for irradiated austenitic SSs in

high– and low–DO environments and those predicted in air for the same loading conditions are

plotted in Fig. 37. The curves represent the Shack/Kassner model for nonirradiated austenitic

SSs in high–purity water with either 8 or 0.2 ppm DO (Eqs. 18 and 19, respectively) and are

included to provide a comparison with the irradiated CGR data. The CGRs in air a ̇ air (m/s)

were determined from the correlations developed by James and Jones,36 e.g., Eqs. 15–17.

The results for SSs irradiated to 0.9 or 2.0 x 1021 n/cm2 (1.35 or 3.0 dpa) indicate

significant enhancement of the CGRs in high–DO water under cyclic loading with long rise

times. The CGRs for Type 304 SS irradiated to either 0.9 or 2.0 x 1021 n◊cm–2, and Type 316

SS irradiated to 2.0 x 1021 n◊cm–2 are comparable. For these irradiation conditions, the CGRs

in water with a 300 ppb DO are slightly higher than the rates predicted by the Shack/Kassner

model for nonirradiated austenitic SSs in high–purity water with 8 ppm DO (Fig. 37a).

Type 304 SS irradiated to 0.3 x 1021 n/cm2 (0.45 dpa) shows very little environmental

enhancement of CGRs in high–DO water (open diamonds in Fig. 37a); the CGRs in water with

a 300 ppb DO may be represented by the Shack/Kassner model for nonirradiated austenitic

SSs in high–purity water with 0.2 ppm DO.

10-12

10-11

10-10

10-9

10-8

10-7

10-12 10-11 10-10 10-9 10-8 10-7

304 SS 0.3x1021 n/cm2

304 SS 0.9x1021 n/cm2

304 SS 2.0x1021 n/cm2

316 SS 2.0x1021 n/cm2

CGRenv (m/s)

CGRair (m/s)

Austenitic SSs, 289°C

a300 ppb Dissolved Oxygen

Shack/Kassner 

Model 0.2 ppm DO

CGRair +4.5x10-5CGRair

0.5

1-h hold

Shack/Kassner 

Model 8 ppm DO

CGRair +1.5x10-4CGRair0.5

10-12

10-11

10-10

10-9

10-8

10-7

10-12 10-11 10-10 10-9 10-8 10-7

Heat C3 0.9x1021 n/cm2

Heat C16 2.0x1021 n/cm2

a30 ppb dissolved H

CGRenv (m/s)

CGRair (m/s)

Austenitic SSs

289°C

<30 ppb Dissolved Oxygen

Shack/Kassner 

Model 0.2 ppm DO

CGRair +4.5x10-5CGRair

0.5

(a) (b)

Figure 37. CGR data for irradiated austenitic SSs under continuous cycling at 289°C in high–purity water

with (a) a300 ppb and (b) <30 ppb dissolved oxygen.
38

For continuous cyclic loading, decreasing the DO level has a beneficial effect on CGRs,

e.g., decreasing the DO from a300 ppb DO to <30 ppb DO results in a factor of 25 decrease in

the CGR. The growth rates are slightly lower for the irradiated steels in water with <30 ppb DO

than for nonirradiated austenitic SSs in high–purity water with 0.2 ppm DO (Fig. 37b). The

CGR data in low–DO environment was not obtained for Type 304 SS specimen C3–C irradiated

to 2 x 1021 n/cm2. As discussed below, a benefit of reduced DO environment was not observed

for this specimen under SCC conditions.

3.2.6 CGRs of Irradiated Austenitic SSs under Cycling with Long Hold Periods

For CGR tests with a trapezoidal waveform (i.e., constant load with periodic partial

unloading), the experimental CGRs for irradiated SSs in high– and low–DO water are plotted in

Fig. 38. In high–DO water, the CGRs obtained in the present study of Types 304 and 316 SS

irradiated to either 0.9 or 2.0 x 1021 n/cm2 are a factor of a5 higher than the disposition curve

for sensitized SSs in water with 8 ppm DO given in NUREG–0313.37 The growth rates for the

two steels at the same fluence level, as well as those for Type 304 SS irradiated to 0.9 and

2.0 x 1021 n/cm2 fluence levels, are comparable. In high–DO water, the CGRs for Type 304

irradiated to 0.3 x 1021 n/cm2 are below the disposition curve for sensitized SSs in water with

8 ppm DO given in NUREG–0313.

The results also indicate a benefit from a low–DO environment. For Heat C3 irradiated to

0.9 x 1021 n/cm2 and Heat C16 irradiated to 2.0 x 1021 n/cm2 (circles and open diamonds in

Fig. 38), the CGRs decreased more than an order of magnitude when the DO level was

decreased from a300 to <30 ppb.

No benefit of low–DO environment was observed for Heat C3 irradiated to 2.0 x

1021 n/cm2 (open and closed triangles in Fig. 38). However, the applied Kmax for the test

period in low–DO water was 44% greater than the allowable value based on the K/size criterion

in Eq. 13. Additional data will be obtained on Type 316 SS Heat C21 irradiated to 0.3, 0.9, and

2.0 x 1021 n/cm2, to better establish the effect of decreased DO level on the CGRs of irradiated

austenitic SSs.

10-12

10-11

10-10

10-9

10-8

10-7

5 10 15 20 25 30

304 SS 0.9x1021 n/cm2

304 SS 2.0x1021 n/cm2

316 SS 2.0x1021 n/cm2

304 SS 0.3x1021 n/cm2

Experimental CGR (m/s)

Stress Intensity K (MPa·m1/2)

289°C

Open Symbols: High–DO

Closed Symbols: Low–DO

NUREG–0313

Curve

5 x 

NUREG 0313

Curve

Figure 38.

CGR data under constant load with periodic

partial unloads for irradiated austenitic SSs in

high–purity water at 289°C
39 

4. Summary

Fracture toughness J–R curve tests have been conducted on four heats of Type 304 SS

that were irradiated to fluence levels of a0.3, 0.9, and 2.0 x 1021 n/cm2 (E > 1 MeV) (a0.45,

1.35, 3.00 dpa) at a288°C in a helium environment in the Halden boiling heavy water reactor.

The tests were performed on 1/4–T compact tension specimens in air at 288°C; crack

extensions were determined by both DC potential and elastic unloading compliance techniques.

Neutron irradiation at 288°C to 2.0 x 1021 n/cm2 (E > 1 MeV) (3.0 dpa) decreased the

fracture toughness of all of the steels. For these materials, minor differences in the chemical

composition of the steels, e.g., differences in nickel content for Heats C16 and C19 or silicon

content for heats L2 and L20, have little or no effect on the fracture toughness of irradiated

steels.

In general, fracture toughness of the commercial Heats C16 and C19 is superior to that of

the laboratory Heats L20 and L2. These differences arise primarily from differences in

toughness of the nonirradiated steels, i.e., the fracture toughness of the laboratory heats is

significantly lower than that of the commercial heats. The fracture toughness J–R curves for

irradiated Types 304 and 316 SS are comparable. The data from commercial heats fall within

the scatter band for the data obtained at higher temperatures. For Heat C19 of Type 304 SS

irradiated to 0.3, 0.9, and 2.0 x 1021 n/cm2, the JIc values are 507, 313, and 188 kJ/m2,

respectively.

Crack growth tests have been performed in simulated BWR environments at a289°C on

Type 304 SS (Heat C3) irradiated to 0.3, 0.9, and 2.0 x 1021 n/cm2 and Type 316 SS (Heat

C16) irradiated to 2.0 x 1021 n/cm2 at a288°C in a helium environment. The tests were

conducted under cyclic loading with a slow/fast sawtooth waveform and long rise times or a

trapezoidal waveform. The latter essentially represents constant load with periodic partial

unloads.

The results for the steels irradiated to either 0.9 or 2.0 x 1021 n/cm2 indicate significant

enhancement of CGRs in the NWC BWR environment. For these irradiation conditions, the

CGRs under continuous cycling are slightly higher than the rates predicted by the

Shack/Kassner model for nonirradiated austenitic SSs in high–purity water with 8 ppm DO.

The CGRs under SCC conditions are a factor of a5 higher than the disposition curve proposed

in NUREG–0313 for sensitized austenitic SSs. The CGRs of Type 304 SS irradiated to 0.9 and

2.0 x 1021 n/cm2 and of Types 304 and 316 SS irradiated to 2.0 x 1021 n/cm2 are comparable.

In low–DO BWR environments, the CGRs of the irradiated steels decreased by an order of

magnitude in tests where K values clearly met the validity criteria, e.g., Heat C3 of Type 304 SS

irradiated to 0.9 x 1021 n/cm2 and Heat C16 of Type 316 SS irradiated to 2 x 1021 n/cm2. The

beneficial effect of decreased DO was not observed for Heat C3 of Type 304 SS irradiated to

2 x 1021 n/cm2; it is possible that this different behavior is associated with the loss of

constraint in the specimen due to the high K.

Type 304 SS irradiated to 0.3 x 1021 n/cm2 (0.45 dpa) shows very little environmental

enhancement of CGRs in the NWC BWR environment; under continuous cycling, the CGRs are

comparable to those predicted by the Shack/Kassner model for nonirradiated austenitic SSs in
40

high–purity water with 0.2 ppm DO. The CGRs for Type 304 irradiated to 0.3 x 1021 n/cm2

under SCC conditions are below the disposition curve for sensitized SSs in water with 8 ppm

DO given in NUREG–0313.
41 

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42

12. F. H. Huang, “The Fracture Characterization of Highly Irradiated Type 316 Stainless

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43 

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45 

Appendix
46
47 

Table A-1. Test data for specimen Y4–03 of thermally aged CF–8M cast SS tested at 288°C

Test Number : JR–18 Test Temp. : 288°C

Material Type : CF–8M Cast SS Heat Number : 4331

Aging Temp. : 400°C Aging Time : 700 h

Irradiation Temp. : – Fluence : –

Thickness : 6.515 mm Net Thickness : 5.879 mm

Width : 12.005 mm Flow Stress : 410.5 MPa

Modulus E : 180 GPa

Initial Crack : 7.43 mm Init. a/W : 0.62 (Measured)

Final Crack : 8.90 mm Final a/W : 0.74 (Measured)

Final Crack : 8.97 mm Final a/W : 0.75 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.0885 0.000

1 1.6352 0.309 34.5 0.103 32.9 0.021

2 1.7575 0.398 48.6 0.016 45.6 0.030

3 1.8598 0.490 63.3 -0.030 59.3 0.039

4 1.9474 0.583 76.7 0.042 74.0 0.047

5 2.0168 0.678 93.2 -0.001 89.5 0.057

6 2.0747 0.774 110.1 -0.014 105.7 0.067

7 2.1142 0.871 126.9 -0.013 120.7 0.159

8 2.1325 0.971 144.1 -0.003 136.2 0.211

9 2.1641 1.069 158.8 0.061 152.2 0.262

10 2.1930 1.169 175.9 0.077 168.6 0.309

11 2.1907 1.269 192.1 0.120 185.0 0.365

12 2.1627 1.373 205.9 0.209 200.2 0.451

13 2.1592 1.475 220.9 0.266 215.4 0.517

14 2.1463 1.577 235.9 0.325 230.8 0.584

15 2.1369 1.679 251.6 0.370 245.9 0.652

16 2.1329 1.781 266.0 0.432 261.3 0.712

17 2.1169 1.884 282.4 0.468 276.9 0.771

18 2.0898 1.988 293.2 0.569 291.6 0.841

19 2.0822 2.091 307.6 0.621 306.6 0.897

20 2.0395 2.196 321.1 0.688 321.9 0.956

21 1.9870 2.302 331.2 0.781 335.5 1.027

22 1.9336 2.408 337.5 0.903 347.7 1.104

23 1.8696 2.515 345.5 1.004 359.9 1.174

24 1.8184 2.621 348.7 1.139 371.5 1.243

25 1.7353 2.731 347.2 1.309 382.5 1.316

26 1.6788 2.837 348.2 1.444 390.6 1.399

27 1.6272 2.943 354.2 1.541 399.1 1.471

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 258 kJ/m2 (15 Data)

Coeff. C : 334 kJ/m2 Exponent n : 0.25 Fit Coeff. R : 0.907

DC Potential Method JIc : 162 kJ/m2 (20 Data)

Coeff. C : 324 kJ/m2 Exponent n : 0.57 Fit Coeff. R : 0.997
48

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 0.5 1 1.5 2 2.5 3 3.5

Measured

Corrected

Load (kN)

Displacement (mm)

Test JR-18

Specimen Y4-03

288°C

CF–8M (Heat 4331) 

Aged 700 h at 400°C

Load–Loadline

Displacement

Figure A-1.1. Load-vs.-loadline displacement curve for specimen Y4–03

of thermally aged CF–8M cast SS tested at 288°C

Figure A-1.2. Fracture surface of specimen Y4–03 tested at 288°C
49 

Table A-2. Test data for specimen Y4–02 of thermally aged CF–8M cast SS tested at 288°C

Test Number : JR–10 Test Temp. : 288°C

Material Type : CF–8M Cast SS Heat Number : 4331

Aging Temp. : 400°C Aging Time : 700 h

Irradiation Temp. : – Fluence : –

Thickness : 6.515 mm Net Thickness : 5.857 mm

Width : 12.003 mm Flow Stress : 410.5 MPa

Modulus E : 180 GPa

Initial Crack : 7.51 mm Init. a/W : 0.63 (Measured)

Final Crack : 9.32 mm Final a/W : 0.78 (Measured)

Final Crack : 9.79 mm Final a/W : 0.82 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.0454 0.000

1 1.3318 0.126 11.3 0.090 10.2 0.006

2 1.5435 0.207 21.7 0.135 20.3 0.012

3 1.8447 0.380 49.2 -0.127 45.7 0.027

4 1.9550 0.471 61.3 0.015 60.3 0.036

5 2.2615 0.846 129.8 -0.147 127.6 0.076

6 2.3153 0.942 142.5 -0.003 146.1 0.087

7 2.3602 1.039 158.0 0.075 165.0 0.098

8 2.3776 1.139 174.3 0.158 183.5 0.148

9 2.3923 1.240 190.4 0.245 201.3 0.202

10 2.4221 1.338 207.1 0.313 218.4 0.259

11 2.4132 1.440 224.0 0.395 236.7 0.311

12 2.4189 1.537 242.1 0.441 253.7 0.367

13 2.4221 1.638 263.4 0.454 270.7 0.433

14 2.3963 1.741 284.2 0.479 287.4 0.502

15 2.3313 1.846 304.8 0.504 303.1 0.581

16 2.2815 1.951 325.9 0.516 317.4 0.668

17 2.2210 2.056 338.7 0.607 331.3 0.750

18 2.1712 2.161 356.1 0.644 344.9 0.828

19 2.0689 2.270 353.6 0.856 357.3 0.920

20 1.9830 2.379 359.4 0.981 366.8 1.023

21 1.8812 2.488 347.5 1.245 374.5 1.133

22 1.7815 2.597 343.0 1.435 380.2 1.245

23 1.7143 2.704 345.7 1.569 385.9 1.347

24 1.6143 2.815 335.4 1.797 389.5 1.465

25 1.5329 2.923 333.6 1.950 394.1 1.560

26 1.4724 3.029 337.5 2.060 397.5 1.658

27 1.4208 3.136 338.5 2.188 402.4 1.740

28 1.3745 3.241 343.7 2.284 408.5 1.813

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 252 kJ/m2 (14 Data)

Coeff. C : 341 kJ/m2 Exponent n : 0.29 Fit Coeff. R : 0.620

DC Potential Method JIc : 254 kJ/m2 (14 Data)

Coeff. C : 351 kJ/m2 Exponent n : 0.31 Fit Coeff. R : 0.976
50

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 0.5 1 1.5 2 2.5 3 3.5

Measured

Corrected

Load (kN)

Displacement (mm)

Test JR-10

288°C

CF–8M (Heat 4331) 

Aged 700 h at 400°C

Load–Loadline

Displacement

Figure A-2.1. Load-vs.-loadline displacement curve for specimen Y4–02

of thermally aged CF–8M cast SS tested at 288°C

Figure A-2.2. Fracture surface of specimen Y4–02 tested at 288°C
51 

Table A-3. Test data for specimen 75–03T of thermally aged CF–8M cast SS tested at 288°C

Test Number : JR–07 Test Temp. : 288°C

Material Type : CF–8M Cast SS Heat Number : 75

Aging Temp. : 400°C Aging Time : 10,000 h

Irradiation Temp. : – Fluence : –

Thickness : 6.51 mm Net Thickness : 5.90 mm

Width : 11.98 mm Flow Stress : 410.0 MPa

Modulus E : 180 GPa

Initial Crack : 7.28 mm Init. a/W : 0.61 (Measured)

Final Crack : 9.35 mm Final a/W : 0.78 (Measured)

Final Crack : 8.72 mm Final a/W : 0.73 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.0436 0.000

1 1.0106 0.057 2.0 -0.105 3.3 0.002

2 1.3193 0.128 10.0 -0.144 10.4 0.006

3 1.5284 0.209 18.5 0.064 19.9 0.012

4 1.8202 0.385 43.2 -0.115 44.1 0.027

5 1.9252 0.476 54.0 0.075 57.9 0.035

6 2.0155 0.569 65.1 0.293 72.7 0.044

7 2.0982 0.659 88.7 -0.130 87.7 0.053

8 2.1654 0.753 103.9 -0.069 103.8 0.063

9 2.2201 0.849 118.4 0.005 120.8 0.073

10 2.2704 0.946 131.8 0.116 138.2 0.084

11 2.2922 1.045 148.4 0.162 156.3 0.095

12 2.2904 1.147 166.6 0.184 171.4 0.205

13 2.2895 1.247 185.9 0.177 183.9 0.336

14 2.2695 1.351 200.2 0.276 195.7 0.491

15 2.2375 1.455 217.3 0.316 207.2 0.638

16 2.2228 1.558 237.1 0.309 219.2 0.766

17 2.1885 1.663 249.8 0.409 232.0 0.884

18 2.1151 1.770 262.2 0.505 243.1 1.033

19 1.9839 1.883 267.4 0.686 248.8 1.253

20 1.9150 1.991 273.7 0.828 251.1 1.479

21 1.8491 2.099 276.1 1.010 255.4 1.660

22 1.7651 2.208 280.7 1.159 260.9 1.832

23 1.6387 2.322 271.7 1.442 261.9 2.074

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 225 kJ/m2 (11 Data)

Coeff. C : 277 kJ/m2 Exponent n : 0.19 Fit Coeff. R : 0.748

DC Potential Method JIc : 180 kJ/m2 (9 Data)

Coeff. C : 233 kJ/m2 Exponent n : 0.22 Fit Coeff. R : 0.972
52

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 0.5 1 1.5 2 2.5 3 3.5

Measured

Corrected

Load (kN)

Displacement (mm)

CF–8M (Spec. #75–03T) 

Aged 10,000 h at 400°C

288°C

Load–Loadline

Displacement

Figure A-3.1. Load-vs.-loadline displacement curve for specimen

75–03T of thermally aged CF–8M cast SS tested at 288°C

Figure A-3.2. Fracture surface of specimen 75–03T tested at 288°C
53 

Table A-4. Test data for specimen 75–04T of thermally aged CF–8M cast SS tested at 288°C

Test Number : JR–08 Test Temp. : 288°C

Material Type : CF–8M Cast SS Heat Number : 75

Aging Temp. : 400°C Aging Time : 10,000 h

Irradiation Temp. : – Fluence : –

Thickness : 6.51 mm Net Thickness : 5.87 mm

Width : 11.98 mm Flow Stress : 410.0 MPa

Modulus E : 180 GPa

Initial Crack : 7.79 mm Init. a/W : 0.65 (Measured)

Final Crack : 9.89 mm Final a/W : 0.83 (Measured)

Final Crack : 10.07 mm Final a/W : 0.84 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.0436 0.000

1 0.4938 0.033 0.9 -0.198 1.0 0.000

2 1.9252 0.829 92.5 -0.063 99.8 0.062

3 2.0155 0.978 111.2 0.062 121.8 0.151

4 2.0982 1.128 131.3 0.171 142.9 0.246

5 2.1654 1.279 154.1 0.238 164.1 0.347

6 2.2201 1.436 179.8 0.284 185.3 0.458

7 2.2704 1.592 203.9 0.348 203.5 0.595

8 2.2922 1.752 222.6 0.474 220.4 0.738

9 2.2904 1.911 234.5 0.648 232.7 0.908

10 2.2895 2.071 240.6 0.857 245.4 1.048

11 2.2695 2.230 248.0 1.027 258.4 1.175

12 2.2375 2.387 254.8 1.188 269.7 1.299

13 2.2228 2.544 268.4 1.278 283.7 1.390

14 2.1885 2.705 265.5 1.531 295.1 1.520

15 2.1151 2.866 265.4 1.694 301.9 1.651

16 1.9839 3.032 255.1 1.968 304.6 1.819

17 1.9150 3.192 241.8 2.176 300.8 1.978

18 1.8491 3.351 242.7 2.283 299.1 2.108

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 197 kJ/m2 (10 Data)

Coeff. C : 248 kJ/m2 Exponent n : 0.20 Fit Coeff. R : 0.931

DC Potential Method JIc : 154 kJ/m2 (10 Data)

Coeff. C : 246 kJ/m2 Exponent n : 0.39 Fit Coeff. R : 0.997
54

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 0.5 1 1.5 2 2.5 3 3.5

Measured

Corrected

Load (kN)

Displacement (mm)

CF–8M (Spec. #75–04T) 

Aged 10,000 h at 400°C

288°C

Load–Loadline

Displacement

Figure A-4.1. Load-vs.-loadline displacement curve for specimen

75–04T of thermally aged CF–8M cast SS tested at 288°C

Figure A-4.2. Fracture surface of specimen 75–04T tested at 288°C
55 

Table A-5. Test data for specimen 75–10T of thermally aged CF–8M cast SS tested at 288°C

Test Number : JR–32 Test Temp. : 288°C

Material Type : CF–8M Cast SS Heat Number : 75

Aging Temp. : 400°C Aging Time : 10,000 h

Irradiation Temp. : – Fluence : –

Thickness : 6.50 mm Net Thickness : 5.82 mm

Width : 12.01 mm Flow Stress : 410.0 MPa

Modulus E : 180 GPa

Initial Crack : 6.08 mm Init. a/W : 0.51 (Measured)

Final Crack : 8.75 mm Final a/W : 0.73 (Measured)

Final Crack : 8.81 mm Final a/W : 0.72 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.0885 0.000

1 2.7615 0.368 58.5 -0.496 55.8 0.038

2 2.9091 0.458 69.1 -0.195 73.0 0.044

3 3.0341 0.550 85.9 -0.051 91.6 0.055

4 3.1404 0.642 98.7 0.264 110.7 0.062

5 3.2116 0.739 118.4 0.331 128.6 0.195

6 3.2370 0.838 142.7 0.266 146.8 0.309

7 3.2792 0.937 167.1 0.209 164.9 0.426

8 3.3219 1.035 178.9 0.461 183.9 0.514

9 3.3099 1.135 204.2 0.415 203.3 0.609

10 3.2659 1.240 216.2 0.654 221.5 0.747

11 3.2468 1.345 232.5 0.794 239.6 0.865

12 3.1347 1.454 258.7 0.787 257.3 0.999

13 2.9554 1.567 269.0 1.005 270.9 1.185

14 2.8420 1.677 282.7 1.143 282.5 1.363

15 2.7179 1.788 287.7 1.380 294.9 1.511

16 2.6173 1.896 296.5 1.552 306.6 1.656

17 2.4656 2.008 294.4 1.841 316.7 1.812

18 2.2673 2.123 305.2 1.977 322.8 2.000

19 2.1098 2.235 304.0 2.215 325.3 2.194

20 1.9790 2.345 308.0 2.383 327.9 2.367

21 1.8358 2.458 307.8 2.581 330.7 2.530

22 1.7366 2.567 311.3 2.731 334.8 2.667

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 181 kJ/m2 (11 Data)

Coeff. C : 258 kJ/m2 Exponent n : 0.30 Fit Coeff. R : 0.914

DC Potential Method JIc : 146 kJ/m2 (11 Data)

Coeff. C : 246 kJ/m2 Exponent n : 0.42 Fit Coeff. R : 0.989
56

0.0

1.0

2.0

3.0

4.0

5.0

0 0.5 1 1.5 2 2.5 3

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JR-32

288°C

Specimen 75-10T

CF-8M 

Heat 75 (28% Ferrite)

Aged 10,000 h at 400°C

Figure A-5.1. Load-vs.-loadline displacement curve for specimen

75–10T of thermally aged CF–8M cast SS tested at 288°C

Figure A-5.2. Fracture surface of specimen 75–10T tested at 288°C
57 

Table A-6. Test data for specimen 184–38 of 50% cold–worked Type 316NG SS tested at 288°C

Test Number : JR–12 Test Temp. : 288°C

Material Type : 50% CW 316NG SS Heat Number : 18474

Aging Temp. : – Aging Time : –

Irradiation Temp. : – Fluence : –

Thickness : 6.497 mm Net Thickness : 5.819 mm

Width : 12.032 mm Flow Stress : 861.0 MPa

Modulus E : 175 GPa

Initial Crack : 7.14 mm Init. a/W : 0.59 (Measured)

Final Crack : 10.30 mm Final a/W : 0.86 (Measured)

Final Crack : 9.64 mm Final a/W : 0.80 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.0445 0.000

1 1.2522 0.045 2.1 0.048 2.1 0.001

2 1.9296 0.093 7.8 0.055 7.9 0.002

3 2.5430 0.148 17.4 0.023 17.4 0.005

4 3.0577 0.208 30.1 0.184 30.2 0.009

5 3.4665 0.274 45.8 0.169 48.0 0.092

6 3.2041 0.389 72.5 0.522 79.8 0.589

7 2.9932 0.505 93.9 0.779 99.0 1.069

8 2.2784 0.658 115.2 1.169 118.1 1.733

9 1.8362 0.792 121.5 1.594 121.3 2.257

10 1.5115 0.919 136.3 1.903 126.9 2.728

11 1.2219 1.046 113.0 2.501 134.4 3.160

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 51 kJ/m2 (5 Data)

Coeff. C : 102 kJ/m2 Exponent n : 0.46 Fit Coeff. R : 0.989

DC Potential Method JIc : 61 kJ/m2 (5 Data)

Coeff. C : 97 kJ/m2 Exponent n : 0.30 Fit Coeff. R : 0.995
58

0.0

1.0

2.0

3.0

4.0

5.0

0 0.2 0.4 0.6 0.9 1.1 1.3 1.5

Measured

Adjusted

Load (kN)

Displacement (mm)

Test JR-12

288°C

50% CW 316NG

Load–Loadline

Displacement

Figure A-6.1. Load-vs.-loadline displacement curve for specimen 184–38

of 50% cold–worked Type 316NG SS tested at 288°C

Figure A-6.2. Fracture surface of specimen 184–38 tested at 288°C
59 

Table A-7. Test data for specimen 184–40 of 50% cold–worked Type 316NG SS tested at 288°C

Test Number : JR–19 Test Temp. : 288°C

Material Type : 50% CW 316NG SS Heat Number : 18474

Aging Temp. : – Aging Time : –

Irradiation Temp. : – Fluence : –

Thickness : 6.528 mm Net Thickness : 5.829 mm

Width : 12.024 mm Flow Stress : 861.0 MPa

Modulus E : 175 GPa

Initial Crack : 7.35 mm Init. a/W : 0.61 (Measured)

Final Crack : 10.28 mm Final a/W : 0.86 (Measured)

Final Crack : 10.01 mm Final a/W : 0.82 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.0894 0.000

1 1.2295 0.083 4.2 0.407 4.3 0.001

2 1.8900 0.126 13.1 0.177 10.0 0.004

3 2.5012 0.174 18.7 0.099 19.0 0.005

4 3.0493 0.230 32.2 0.135 31.9 0.009

5 3.4621 0.304 52.6 0.148 52.3 0.015

6 3.2699 0.419 79.9 0.481 86.3 0.373

7 2.6147 0.568 99.7 1.030 110.4 0.997

8 2.3976 0.634 103.4 1.228 105.4 1.229

9 1.9777 0.715 109.2 1.530 113.1 1.574

10 1.6716 0.788 114.2 1.699 112.9 1.850

11 1.5275 0.850 116.5 1.890 112.8 2.051

12 1.4056 0.910 116.5 2.098 115.3 2.261

13 1.2873 0.971 118.4 2.238 116.1 2.436

14 1.1210 1.037 118.8 2.420 118.1 2.642

15 1.0453 1.094 119.1 2.547 116.2 2.794

16 0.9715 1.152 120.2 2.666 117.6 2.939

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 61 kJ/m2 (8 Data)

Coeff. C : 96 kJ/m2 Exponent n : 0.30 Fit Coeff. R : 0.993

DC Potential Method JIc : 81 kJ/m2 (8 Data)

Coeff. C : 104 kJ/m2 Exponent n : 0.17 Fit Coeff. R : 0.989
60

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 0.5 1 1.5 2

Measured

Corrected

Load (kN)

Displacement (mm)

Test JR-19

Specimen 184-40

288°C

50% CW Type 316NG

Load–Loadline

Displacement

Figure A-7.1. Load-vs.-loadline displacement curve for specimen 184–40

of 50% cold–worked Type 316NG SS tested at 288°C

Figure A-7.2. Fracture surface of specimen 184–40 tested at 288°C
61 

Table A-8. Test data for specimen C19–D of nonirradiated Type 304 SS tested at 288°C

Test Number : JR–27 Test Temp. : 288°C

Material Type : Type 304 SS Heat Number : C19

Aging Temp. : – Aging Time : –

Irradiation Temp. : – Fluence : –

Thickness : 6.480 mm Net Thickness : 5.890 mm

Width : 12.000 mm Flow Stress : 339.5 MPa

Modulus E : 175 GPa

Initial Crack : 7.28 mm Init. a/W : 0.61 (Measured)

Final Crack : 7.63 mm Final a/W : 0.64 (Measured)

Final Crack : 7.70 mm Final a/W : 0.64 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.089 0.000

1 1.214 0.247 21.8 -0.001 21.8 0.016

2 1.279 0.342 31.5 -0.027 31.2 0.023

3 1.346 0.435 40.3 0.056 40.9 0.030

4 1.407 0.582 56.5 0.070 57.0 0.042

5 1.515 0.774 80.0 0.033 79.3 0.059

6 1.607 0.969 102.8 0.087 103.2 0.076

7 1.674 1.166 125.6 0.181 128.6 0.092

8 1.790 1.562 183.4 0.172 182.4 0.135

9 1.852 1.761 210.0 0.232 210.9 0.155

10 1.931 1.956 247.1 0.134 239.4 0.182

11 2.025 2.355 300.5 0.254 301.1 0.221

12 2.153 2.852 392.9 0.152 381.1 0.289

13 2.221 3.150 433.5 0.253 432.1 0.319

14 2.294 3.449 464.5 0.434 485.7 0.342

15 2.439 4.045 587.5 0.418 590.0 0.433

16 2.536 4.524 673.8 0.519

17 2.617 5.046 765.5 0.625

18 2.670 5.550 834.9 0.811

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 695 kJ/m2 (9 Data)

Coeff. C : 765 kJ/m2 Exponent n : 0.28 Fit Coeff. R : 0.338

DC Potential Method (information could not be determined)
62

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0123456

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JR-27

288°C

Specimen C19–D

Nonirradiated

Figure A-8.1. Load-vs.-loadline displacement curve for specimen C19–D

of nonirradiated Type 304 SS tested at 288°C

Figure A-8.2. Fracture surface of specimen C19–D tested at 288°C
63 

Table A-9. Test data for specimen C16–C of nonirradiated Type 316 SS tested at 288°C

Test Number : JR–31 Test Temp. : 288°C

Material Type : Type 316 SS Heat Number : C16

Aging Temp. : – Aging Time : –

Irradiation Temp. : – Fluence : –

Thickness : 6.500 mm Net Thickness : 5.810 mm

Width : 11.990 mm Flow Stress : 336.0 MPa (estimated)

Modulus E : 175 GPa

Initial Crack : 7.30 mm Init. a/W : 0.61 (Measured)

Final Crack : 7.96 mm Final a/W : 0.66 (Measured)

Final Crack : 7.65 mm Final a/W : 0.64 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.065 0.000 0.0 0.000

1 1.207 0.208 18.9 -0.002 19.0 0.014

2 1.293 0.412 40.2 -0.064 39.5 0.030

3 1.370 0.618 60.7 0.023 61.5 0.045

4 1.426 0.826 82.5 0.103 84.7 0.061

5 1.492 1.023 108.6 0.041 107.8 0.081

6 1.555 1.220 129.2 0.146 132.0 0.096

7 1.620 1.417 152.1 0.219 157.0 0.113

8 1.674 1.615 178.7 0.236 182.9 0.133

9 1.784 2.012 251.4 0.077 236.3 0.187

10 1.831 2.211 278.6 0.095 264.8 0.207

11 1.877 2.410 310.1 0.082 293.7 0.231

12 1.925 2.609 338.6 0.112 323.6 0.252

13 1.977 2.808 373.7 0.081 353.6 0.278

14 2.023 3.007 413.8 0.015 384.0 0.308

15 2.060 3.207 439.0 0.083 416.3 0.327

16 2.100 3.407 469.7 0.108 448.6 0.349

17 2.140 3.607 503.6 0.114 481.1 0.375

18 2.180 3.807 520.0 0.243 515.9 0.387

19 2.219 4.007 555.5 0.249 549.1 0.413

20 2.259 4.207 601.8 0.197 581.4 0.448

21 2.298 4.406 632.6 0.239 616.3 0.471

22 2.330 4.607 646.5 0.371 654.1 0.481

23 2.359 4.808 689.0 0.356 688.2 0.513

Power–Law Fit J = C(Da)n

(information could not be determined)
64

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0123456

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JR-31

288°C

Specimen C16–C

Nonirradiated

Figure A-9.1. Load-vs.-loadline displacement curve for specimen C16–C

of nonirradiated Type 316 SS tested at 288°C

Figure A-9.2. Fracture surface of specimen C16–C tested at 288°C
65 

Table A-10. Test data for specimen C16–D of nonirradiated Type 316 SS tested at 288°C

Test Number : JR–28 Test Temp. : 288°C

Material Type : Type 316 SS Heat Number : C16

Aging Temp. : – Aging Time : –

Irradiation Temp. : – Fluence : –

Thickness : 6.470 mm Net Thickness : 5.90 mm

Width : 11.980 mm Flow Stress : 336.0 MPa (estimated)

Modulus E : 175 GPa

Initial Crack : 7.41 mm Init. a/W : 0.62 (Measured)

Final Crack : 7.83 mm Final a/W : 0.65 (Measured)

Final Crack : 7.60 mm Final a/W : 0.63 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.088 0.000 0.0 0.000

1 1.218 0.247 22.5 0.059 23.0 0.017

2 1.304 0.441 43.5 0.007 42.9 0.032

3 1.373 0.637 63.8 0.072 64.1 0.047

4 1.439 0.834 85.4 0.129 86.5 0.064

5 1.501 1.031 109.2 0.140 109.9 0.081

6 1.567 1.228 138.6 0.026 134.1 0.103

7 1.621 1.426 170.1 -0.096 159.3 0.127

8 1.672 1.625 192.1 -0.014 185.7 0.143

9 1.725 1.823 204.8 0.230 213.3 0.152

10 1.772 2.023 230.1 0.287 241.3 0.171

11 1.818 2.222 260.1 0.295 269.7 0.194

12 1.865 2.421 310.7 0.068 297.6 0.231

13 1.908 2.621 332.8 0.169 327.7 0.248

14 1.949 2.820 368.4 0.134 357.8 0.274

15 1.982 3.020 400.4 0.141 388.8 0.298

16 2.019 3.221 428.9 0.182 420.6 0.319

17 2.055 3.420 467.3 0.148 452.3 0.348

18 2.088 3.621 495.4 0.195 484.8 0.369

Power–Law Fit J = C(Da)n

(information could not be determined)
66

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0123456

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JR-28

288°C

Specimen C16–D

Nonirradiated

Figure A-10.1. Load-vs.-loadline displacement curve for specimen

C16–D of nonirradiated Type 316 SS tested at 288°C

Figure A-10.2. Fracture surface of specimen C16–D tested at 288°C
67 

Table A-11. Test data for specimen L20–D of nonirradiated Type 304 SS tested at 288°C

Test Number : JR–29 Test Temp. : 288°C

Material Type : Type 304L SS (HP) Heat Number : L20

Aging Temp. : – Aging Time : –

Irradiation Temp. : – Fluence : –

Thickness : 6.50 mm Net Thickness : 5.89 mm

Width : 12.00 mm Flow Stress : 307.0 MPa (estimated)

Modulus E : 175 GPa

Initial Crack : 7.22 mm Init. a/W : 0.60 (Measured)

Final Crack : 9.52 mm Final a/W : 0.79 (Measured)

Final Crack : 8.84 mm Final a/W : 0.74 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.0000 0.000

1 1.2384 0.028 3.3 -0.704 3.4 0.003

2 1.4995 0.103 8.4 -0.481 11.4 0.007

3 1.6414 0.190 17.4 -0.170 22.1 0.014

4 1.7179 0.285 28.9 0.082 33.0 0.024

5 1.8211 0.581 78.1 0.072 74.0 0.143

6 1.8264 0.682 88.5 0.184 86.6 0.232

7 1.8069 0.786 102.8 0.204 98.4 0.366

8 1.7975 0.888 117.5 0.209 110.0 0.473

9 1.7949 0.991 125.9 0.397 121.8 0.576

10 1.7917 1.092 138.0 0.460 134.0 0.659

11 1.7704 1.196 153.0 0.473 146.4 0.748

12 1.7468 1.300 169.2 0.460 158.1 0.843

13 1.7148 1.405 175.8 0.635 169.6 0.940

14 1.6761 1.510 192.7 0.600 180.3 1.044

15 1.6365 1.615 203.1 0.686 190.0 1.153

16 1.5991 1.720 212.3 0.774 199.3 1.263

17 1.5627 1.825 224.8 0.808 208.5 1.363

18 1.5440 1.929 225.6 0.999 217.8 1.455

19 1.5088 2.033 240.6 0.990 227.2 1.544

20 1.4684 2.139 243.0 1.150 235.9 1.641

21 1.4354 2.244 253.0 1.200 243.8 1.737

22 1.4021 2.349 266.8 1.211 252.5 1.815

23 1.3652 2.454 272.8 1.306 260.8 1.902

24 1.3260 2.559 283.3 1.344 267.3 2.000

25 1.2886 2.665 293.3 1.386 272.9 2.098

26 1.2517 2.770 289.9 1.550 278.1 2.194

27 1.2104 2.876 294.9 1.626 281.8 2.302

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 119 kJ/m2 (19 Data)

Coeff. C : 236 kJ/m2 Exponent n : 0.56 Fit Coeff. R : 0.948

DC Potential Method JIc : 78 kJ/m2 (21 Data)

Coeff. C : 174 kJ/m2 Exponent n : 0.60 Fit Coeff. R : 0.998
68

0.0

0.5

1.0

1.5

2.0

2.5

0 0.5 1 1.5 2 2.5 3 3.5 4

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JR-29

288°C

Specimen L20–D

Nonirradiated

Figure A-11.1. Load-vs.-loadline displacement curve for specimen

L20–D of nonirradiated Type 304 SS tested at 288°C

Figure A-11.2. Fracture surface of specimen L20–D tested at 288°C
69 

Table A-12. Test data for specimen L2–C of nonirradiated Type 304 SS tested at 288°C

Test Number : JR–20 Test Temp. : 288°C

Material Type : Type 304 SS Heat Number : L2

Aging Temp. : – Aging Time : –

Irradiation Temp. : – Fluence : –

Thickness : 6.51 mm Net Thickness : 5.84 mm

Width : 11.98 mm Flow Stress : 270.5 MPa

Modulus E : 175 GPa

Initial Crack : 7.38 mm Init. a/W : 0.61 (Measured)

Final Crack : 9.17 mm Final a/W : 0.76 (Measured)

Final Crack : 8.08 mm Final a/W : 0.75 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.089 0.000

1 1.300 0.080 6.5 0.237 6.5 0.006

2 1.453 0.169 18.9 0.152 17.1 0.016

3 1.529 0.265 30.2 0.155 29.3 0.028

4 1.596 0.361 43.7 0.126 41.9 0.040

5 1.648 0.459 58.7 0.041 55.2 0.054

6 1.685 0.556 72.5 0.015 68.9 0.067

7 1.717 0.656 87.4 0.027 83.2 0.080

8 1.741 0.756 101.7 0.040 97.7 0.093

9 1.754 0.857 117.1 0.027 112.4 0.107

10 1.769 0.958 130.1 0.082 127.1 0.119

11 1.774 1.059 144.7 0.101 142.1 0.132

12 1.780 1.160 159.9 0.104 157.0 0.146

13 1.775 1.275 176.7 0.120 171.1 0.234

14 1.759 1.379 191.6 0.136 181.6 0.339

15 1.734 1.482 203.5 0.200 192.3 0.432

16 1.708 1.586 214.2 0.277 201.9 0.542

17 1.692 1.688 227.3 0.310 211.0 0.651

18 1.666 1.793 238.6 0.372 220.9 0.747

19 1.619 1.898 243.2 0.518 230.0 0.850

20 1.580 2.001 252.5 0.593 237.2 0.973

21 1.544 2.105 260.8 0.676 244.9 1.075

22 1.504 2.209 265.5 0.798 253.0 1.173

23 1.461 2.315 275.3 0.859 259.4 1.289

24 1.411 2.470 283.6 1.006 270.8 1.429

25 1.353 2.627 292.9 1.132 280.0 1.577

26 1.280 2.785 299.8 1.271 286.5 1.741

27 1.219 2.942 304.8 1.417 292.3 1.893

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 237 kJ/m2 (13 Data)

Coeff. C : 283 kJ/m2 Exponent n : 0.20 Fit Coeff. R : 0.988

DC Potential Method JIc : 186 kJ/m2 (15 Data)

Coeff. C : 243 kJ/m2 Exponent n : 0.27 Fit Coeff. R : 0.996
70

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 0.5 1 1.5 2 2.5 3 3.5 4

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JR-20

288°C

Specimen L2-C

Nonirradiated

Figure A-12.1. Load-vs.-loadline displacement curve for specimen L2–C

of nonirradiated Type 304 SS tested at 288°C

Figure A-12.2. Fracture surface of specimen L2–C tested at 288°C
71 

Table A-13. Test data for specimen L2–E of nonirradiated Type 304 SS tested at 288°C

Test Number : JR–30 Test Temp. : 288°C

Material Type : Type 304 SS Heat Number : L2

Aging Temp. : – Aging Time : –

Irradiation Temp. : – Fluence : –

Thickness : 6.49 mm Net Thickness : 5.87 mm

Width : 12.03 mm Flow Stress : 270.5 MPa

Modulus E : 175 GPa

Initial Crack : 7.38 mm Init. a/W : 0.61 (Measured)

Final Crack : 9.17 mm Final a/W : 0.76 (Measured)

Final Crack : 8.08 mm Final a/W : 0.75 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.0885 0.000

1 1.1441 0.052 4.2 0.027 4.2 0.004

2 1.2273 0.144 13.0 0.049 13.1 0.012

3 1.3033 0.238 23.0 -0.020 22.6 0.021

4 1.3669 0.334 32.8 0.057 32.9 0.030

5 1.4225 0.430 44.4 -0.014 43.7 0.041

6 1.4741 0.527 55.9 -0.022 55.0 0.052

7 1.5226 0.624 65.5 0.102 66.7 0.061

8 1.5627 0.722 78.0 0.088 78.8 0.072

9 1.6022 0.820 88.5 0.185 91.2 0.082

10 1.6347 0.918 99.6 0.261 102.2 0.173

11 1.6534 1.019 116.8 0.150 114.1 0.218

12 1.6743 1.118 123.1 0.371 126.3 0.266

13 1.6908 1.219 142.0 0.244 138.8 0.312

14 1.7019 1.320 147.3 0.468 151.2 0.362

15 1.7095 1.421 159.3 0.523 163.8 0.411

16 1.7166 1.522 175.1 0.512 176.2 0.463

17 1.7192 1.630 185.8 0.619 189.7 0.512

18 1.7143 1.732 203.4 0.584 201.9 0.568

19 1.6899 1.835 211.2 0.715 213.6 0.633

20 1.6690 1.938 228.6 0.688 224.1 0.709

21 1.6561 2.041 255.8 0.535 235.1 0.771

22 1.6458 2.143 242.8 0.899 246.1 0.835

23 1.6276 2.246 263.8 0.819 256.8 0.899

24 1.6009 2.350 277.7 0.848 266.7 0.971

25 1.5867 2.453 284.1 0.949 276.6 1.037

26 1.5529 2.557 307.0 0.874 285.8 1.113

27 1.5280 2.661 305.2 1.049 294.6 1.185

28 1.4928 2.765 318.5 1.064 302.9 1.261

29 1.4599 2.870 314.4 1.244 310.9 1.335

30 1.4265 2.975 322.2 1.307 316.6 1.412

31 1.3963 3.080 335.2 1.329 325.3 1.489

32 1.3705 3.184 341.3 1.406 332.3 1.559

33 1.3300 3.289 334.7 1.579 339.7 1.627

34 1.2771 3.396 340.4 1.649 345.0 1.710

35 1.2371 3.501 348.0 1.706 349.1 1.792

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 154 kJ/m2 (25 Data)

Coeff. C : 275 kJ/m2 Exponent n : 0.54 Fit Coeff. R : 0.866

DC Potential Method JIc : 159 kJ/m2 (19 Data)

Coeff. C : 268 kJ/m2 Exponent n : 0.49 Fit Coeff. R : 0.997
72

0.0

0.5

1.0

1.5

2.0

2.5

0 0.5 1 1.5 2 2.5 3 3.5 4

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JR-30

288°C

Specimen L2-E

Nonirradiated

Figure A-13.1. Load-vs.-loadline displacement curve for specimen L2–E

of nonirradiated Type 304 SS tested at 288°C

Figure A-13.2. Fracture surface of specimen L2–E tested at 288°C
73 

Table A-14. Test data for specimen C19–A of irradiated Type 304 SS tested at 288°C

Test Number : JRI–21 Test Temp. : 288°C

Material Type : Type 304 SS Heat Number : C19

Aging Temp. : – Aging Time : –

Irradiation Temp. : 288°C Fluence : 0.3 x 1021 n/cm2

Thickness : 6.50 mm Net Thickness : 5.85 mm

Width : 12.00 mm Flow Stress : 618.0 MPa

Modulus E : 175 GPa Effective Flow Stress : 478.8 MPa

Initial Crack : 7.45 mm Init. a/W : 0.62 (Measured)

Final Crack : 8.84 mm Final a/W : 0.74 (Measured)

Final Crack : 8.32 mm Final a/W : 0.69 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.088 0.000

1 2.618 1.094 204.8 0.000 204.3 0.107

2 2.637 1.194 226.8 0.000 226.0 0.118

3 2.658 1.295 249.3 0.000 248.1 0.130

4 2.673 1.395 271.4 0.000 270.1 0.140

5 2.687 1.497 294.4 0.000 292.7 0.153

6 2.702 1.597 316.8 0.000 314.9 0.164

7 2.701 1.699 339.5 0.000 337.1 0.179

8 2.706 1.802 356.2 0.068 360.2 0.188

9 2.705 1.902 372.4 0.132 382.8 0.196

10 2.708 2.004 405.3 0.044 405.0 0.213

11 2.705 2.104 427.5 0.050 430.1 0.227

12 2.698 2.207 438.3 0.152 453.5 0.232

13 2.680 2.310 461.9 0.149 475.0 0.251

14 2.666 2.414 486.0 0.147 487.4 0.336

15 2.645 2.516 507.6 0.158 499.7 0.415

16 2.613 2.619 522.2 0.215 510.7 0.502

17 2.589 2.723 545.4 0.215 521.8 0.587

18 2.562 2.827 566.4 0.227 531.2 0.681

19 2.526 2.931 585.2 0.252 544.1 0.748

20 2.460 3.037 570.7 0.467 555.4 0.829

21 2.425 3.143 580.0 0.541 565.2 0.913

22 2.395 3.246 587.8 0.623 575.7 0.987

23 2.354 3.351 608.1 0.639 586.4 1.062

24 2.332 3.454 637.1 0.607 595.9 1.138

25 2.267 3.561 633.3 0.741 604.7 1.220

26 2.218 3.666 652.0 0.757 611.3 1.307

27 2.166 3.771 649.6 0.874 617.3 1.393

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 599 kJ/m2 (15 Data)

Coeff. C : 661 kJ/m2 Exponent n : 0..15 Fit Coeff. R : 0.834

DC Potential Method JIc : 507 kJ/m2 (17 Data)

Coeff. C : 579 kJ/m2 Exponent n : 0.17 Fit Coeff. R : 0.975
74

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 0.5 1 1.5 2 2.5 3 3.5 4

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JRI-21

288°C

Specimen C19–A

0.3 x 1021 n cm–2

Figure A-14.1 Load-vs.-loadline displacement curve for specimen

C19–A of irradiated Type 304 SS tested at 288°C

Figure A-14.2 Fracture surface of specimen C19–A tested at 288°C
75 

Table A-15. Test data for specimen C19–B of irradiated Type 304 SS tested at 288°C

Test Number : JRI–23 Test Temp. : 288°C

Material Type : Type 304 SS Heat Number : C19

Aging Temp. : – Aging Time : –

Irradiation Temp. : 288°C Fluence : 0.9 x 1021 n/cm2

Thickness : 6.50 mm Net Thickness : 5.85 mm

Width : 12.00 mm Flow Stress : 759.5 MPa

Modulus E : 175 GPa Effective Flow Stress : 549.5 MPa

Initial Crack : 7.36 mm Init. a/W : 0.61 (Measured)

Final Crack : 9.40 mm Final a/W : 0.78 (Measured)

Final Crack : 9.01 mm Final a/W : 0.75 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.088 0.000

1 1.971 0.125 9.7 -0.014 9.8 0.004

2 2.630 0.176 19.2 -0.376 19.1 0.007

3 3.185 0.236 26.7 -0.041 33.1 0.010

4 3.544 0.311 52.4 0.055 53.7 0.020

5 3.643 0.404 78.0 0.081 80.5 0.030

6 3.636 0.519 110.5 0.159 114.3 0.043

7 3.589 0.624 142.0 0.119 144.7 0.055

8 3.527 0.729 172.2 0.155 174.6 0.067

9 3.469 0.836 205.8 0.095 204.6 0.080

10 3.426 0.941 233.9 0.143 233.5 0.091

11 3.341 1.047 259.4 0.199 262.3 0.101

12 3.266 1.153 281.3 0.294 285.4 0.210

13 3.195 1.259 309.3 0.296 304.8 0.309

14 3.124 1.366 335.0 0.334 324.7 0.397

15 3.058 1.472 357.7 0.390 344.5 0.479

16 2.959 1.581 384.2 0.405 363.8 0.566

17 2.880 1.689 404.9 0.467 381.4 0.657

18 2.793 1.796 416.2 0.590 397.9 0.746

19 2.709 1.903 440.3 0.599 413.7 0.832

20 2.647 2.009 461.1 0.640 428.7 0.918

21 2.539 2.169 486.0 0.730 452.1 1.040

22 2.431 2.329 508.4 0.819 471.2 1.169

23 2.284 2.491 524.1 0.941 487.7 1.301

24 2.184 2.649 538.6 1.048 503.1 1.416

25 2.060 2.811 550.1 1.167 515.4 1.550

26 1.951 2.970 552.7 1.318 522.6 1.694

27 1.834 3.131 559.7 1.436 529.4 1.823

28 1.743 3.290 569.4 1.534 537.1 1.939

29 1.657 3.449 574.7 1.647 546.4 2.041

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 368 kJ/m2 (16 Data)

Coeff. C : 513 kJ/m2 Exponent n : 0.33 Fit Coeff. R : 0.948

DC Potential Method JIc : 313 kJ/m2 (17 Data)

Coeff. C : 442 kJ/m2 Exponent n : 0.32 Fit Coeff. R : 0.996
76

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 0.5 1 1.5 2 2.5 3 3.5 4

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JRI-23

288°C

Specimen C19–B

0.9 x 1021 n cm-2

Figure A-15.1 Load-vs.-loadline displacement curve for specimen

C19–B of irradiated Type 304 SS tested at 288°C

Figure A-15.2 Fracture surface of specimen C19–B tested at 288°C
77 

Table A-16. Test data for specimen C19–C of irradiated Type 304 SS tested at 288°C

Test Number : JRI–33 Test Temp. : 288°C

Material Type : Type 304 SS Heat Number : C19

Aging Temp. : – Aging Time : –

Irradiation Temp. : 288°C Fluence : 2.0 x 1021 n/cm2

Thickness : 6.50 mm Net Thickness : 5.85 mm

Width : 12.00 mm Flow Stress : 794.0 MPa

Modulus E : 175 GPa Effective Flow Stress : 566.8 MPa

Initial Crack : 7.38 mm Init. a/W : 0.61 (Measured)

Final Crack : 9.20 mm Final a/W : 0.77 (Measured)

Final Crack : 9.13 mm Final a/W : 0.76 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.089 0.000

1 0.621 0.040 1.1 -0.254

2 0.930 0.061 2.1 -0.011

3 1.251 0.082 4.3 0.047

4 1.586 0.106 7.3 -0.034

5 1.911 0.129 10.3 -0.078

6 2.234 0.156 14.3 -0.103

7 2.543 0.182 19.2 -0.381

8 2.839 0.210 23.2 -0.388

9 3.108 0.240 29.1 -0.253

10 3.352 0.273 35.0 -0.176

11 3.540 0.310 42.9 -0.090

12 3.668 0.350 52.3 -0.044

13 3.718 0.397 64.4 0.038

14 3.691 0.449 78.8 0.003

15 3.627 0.504 96.1 0.006

16 3.546 0.558 110.7 0.072

17 3.412 0.668 140.4 0.102

18 3.232 0.781 168.7 0.168

19 3.070 0.893 190.6 0.311

20 2.926 1.004 212.8 0.387

21 2.746 1.118 228.3 0.575

22 2.569 1.232 239.9 0.762

23 2.426 1.343 248.2 0.956

24 2.294 1.453 256.6 1.122

25 2.166 1.564 269.5 1.230

26 2.073 1.672 280.5 1.351

27 1.963 1.780 297.9 1.445

28 1.871 1.889 306.0 1.523

29 1.795 1.997 318.9 1.599

30 1.700 2.105 329.9 1.680

31 1.625 2.212 340.0 1.757

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 188 kJ/m2 (15 Data)

Coeff. C : 268 kJ/m2 Exponent n : 0.28 Fit Coeff. R : 0.967

DC Potential Method (information could not be determined)
78

0.0

1.0

2.0

3.0

4.0

5.0

0 0.5 1 1.5 2 2.5 3

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JR-32

288°C

Specimen C19-C

2 x 1021 n cm-2

Figure A-16.1 Load-vs.-loadline displacement curve for specimen

C19–C of irradiated Type 304 SS tested at 288°C

Figure A-16.2 Fracture surface of specimen C19–C tested at 288°C
79 

Table A-17. Test data for specimen C16–A of irradiated Type 316 SS tested at 288°C

Test Number : JR–26 Test Temp. : 288°C

Material Type : Type 316 SS Heat Number : C16

Aging Temp. : – Aging Time : –

Irradiation Temp. : 288°C Fluence : 0.9 x 1021 n/cm2

Thickness : 6.50 mm Net Thickness : 5.85 mm

Width : 12.00 mm Flow Stress : 590.0 MPa

Modulus E : 175 GPa Effective Flow Stress : 463.0 MPa

Initial Crack : 7.28 mm Init. a/W : 0.61 (Measured)

Final Crack : 8.73 mm Final a/W : 0.73 (Measured)

Final Crack : 8.36 mm Final a/W : 0.70 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.089 0.000

1 2.527 0.212 33.3 0.054 26.6 0.015

2 2.702 0.275 42.4 0.066 39.8 0.019

3 2.755 0.347 59.3 0.004 55.6 0.026

4 2.785 0.421 74.5 0.024 72.0 0.033

5 2.807 0.496 89.8 0.097 88.7 0.039

6 2.810 0.572 106.4 0.099 105.4 0.047

7 2.812 0.649 123.1 0.136 122.8 0.054

8 2.821 0.725 141.0 0.117 139.8 0.062

9 2.832 0.801 159.6 0.097 156.9 0.070

10 2.818 0.880 176.6 0.126 174.5 0.077

11 2.823 0.955 191.1 0.184 191.4 0.084

12 2.821 1.031 207.2 0.202 208.3 0.091

13 2.800 1.136 230.7 0.217 230.0 0.139

14 2.805 1.236 255.9 0.189 249.9 0.183

15 2.784 1.338 279.1 0.198 269.6 0.234

16 2.785 1.441 294.0 0.310 289.0 0.290

17 2.770 1.544 313.2 0.356 307.9 0.346

18 2.745 1.647 343.0 0.293 327.1 0.397

19 2.720 1.751 354.0 0.430 345.8 0.456

20 2.693 1.853 378.8 0.410 363.3 0.515

21 2.655 1.957 402.9 0.413 380.8 0.576

22 2.619 2.063 414.2 0.521 398.1 0.638

23 2.573 2.169 430.2 0.580 414.7 0.703

24 2.539 2.273 455.9 0.561 430.3 0.767

25 2.512 2.378 479.9 0.561 445.4 0.834

26 2.480 2.482 498.3 0.595 461.4 0.888

27 2.444 2.588 513.3 0.648 477.9 0.941

28 2.393 2.693 512.5 0.796 493.9 0.994

29 2.351 2.797 532.4 0.807 506.3 1.051

30 2.292 2.904 550.9 0.836 521.0 1.111

31 2.230 3.010 560.4 0.911 532.4 1.188

32 2.180 3.117 568.0 0.989 543.1 1.260

33 2.128 3.223 584.6 1.016 554.5 1.325

34 2.081 3.328 596.2 1.068 565.4 1.390

35 2.040 3.429 613.3 1.086 575.4 1.453

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 353 kJ/m2 (12 Data)

Coeff. C : 607 kJ/m2 Exponent n : 0.52 Fit Coeff. R : 0.848

DC Potential Method JIc : 299 kJ/m2 (14 Data)

Coeff. C : 490 kJ/m2 Exponent n : 0.45 Fit Coeff. R : 0.997
80

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 0.5 1 1.5 2 2.5 3 3.5 4

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JRI-26

288°C

Specimen C16–A

0.9 x 1021 n cm-2

Figure A-17.1 Load-vs.-loadline displacement curve for specimen

C16–A of irradiated Type 316 SS tested at 288°C

Figure A-17.2 Fracture surface of specimen C16–A tested at 288°C
81 

Table A-18. Test data for specimen L20–A of irradiated Type 304 SS tested at 288°C

Test Number : JR–22 Test Temp. : 288°C

Material Type : Type 304 SS Heat Number : L20

Aging Temp. : – Aging Time : –

Irradiation Temp. : 288°C Fluence : 0.3 x 1021 n/cm2

Thickness : 6.50 mm Net Thickness : 5.85 mm

Width : 2.00 mm Flow Stress : 270.5 MPa

Modulus E : 175 GPa

Initial Crack : 7.38 mm Init. a/W : 0.61 (Measured)

Final Crack : 9.17 mm Final a/W : 0.76 (Measured)

Final Crack : 8.08 mm Final a/W : 0.75 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.089 0.000

1 1.300 0.080 6.5 0.237 6.5 0.006

2 1.453 0.169 18.9 0.152 17.1 0.016

3 1.529 0.265 30.2 0.155 29.3 0.028

4 1.596 0.361 43.7 0.126 41.9 0.040

5 1.648 0.459 58.7 0.041 55.2 0.054

6 1.685 0.556 72.5 0.015 68.9 0.067

7 1.717 0.656 87.4 0.027 83.2 0.080

8 1.741 0.756 101.7 0.040 97.7 0.093

9 1.754 0.857 117.1 0.027 112.4 0.107

10 1.769 0.958 130.1 0.082 127.1 0.119

11 1.774 1.059 144.7 0.101 142.1 0.132

12 1.780 1.160 159.9 0.104 157.0 0.146

13 1.775 1.275 176.7 0.120 171.1 0.234

14 1.759 1.379 191.6 0.136 181.6 0.339

15 1.734 1.482 203.5 0.200 192.3 0.432

16 1.708 1.586 214.2 0.277 201.9 0.542

17 1.692 1.688 227.3 0.310 211.0 0.651

18 1.666 1.793 238.6 0.372 220.9 0.747

19 1.619 1.898 243.2 0.518 230.0 0.850

20 1.580 2.001 252.5 0.593 237.2 0.973

21 1.544 2.105 260.8 0.676 244.9 1.075

22 1.504 2.209 265.5 0.798 253.0 1.173

23 1.461 2.315 275.3 0.859 259.4 1.289

24 1.411 2.470 283.6 1.006 270.8 1.429

25 1.353 2.627 292.9 1.132 280.0 1.577

26 1.280 2.785 299.8 1.271 286.5 1.741

27 1.219 2.942 304.8 1.417 292.3 1.893

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 237 kJ/m2 (13 Data)

Coeff. C : 283 kJ/m2 Exponent n : 0.20 Fit Coeff. R : 0.988

DC Potential Method JIc : 186 kJ/m2 (15 Data)

Coeff. C : 243 kJ/m2 Exponent n : 0.27 Fit Coeff. R : 0.996
82

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 0.5 1 1.5 2 2.5 3 3.5 4

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JR-20

288°C

Specimen L2-C

Nonirradiated

Figure A-18.1. Load-vs.-loadline displacement curve for specimen

L20–A of irradiated Type 304 SS tested at 288°C

Figure A-18.2. Fracture surface of specimen L20–A tested at 288°C
83 

Table A-19. Test data for specimen L20–B of irradiated Type 304 SS tested at 288°C

Test Number : JR–24 Test Temp. : 288°C

Material Type : Type 304 SS Heat Number : L20

Aging Temp. : – Aging Time : –

Irradiation Temp. : 288°C Fluence : 0.9 x 1021 n/cm2

Thickness : 6.51 mm Net Thickness : 5.84 mm

Width : 11.98 mm Flow Stress : 270.5 MPa

Modulus E : 175 GPa

Initial Crack : 7.38 mm Init. a/W : 0.61 (Measured)

Final Crack : 9.17 mm Final a/W : 0.76 (Measured)

Final Crack : 8.08 mm Final a/W : 0.75 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.089 0.000

1 1.300 0.080 6.5 0.237 6.5 0.006

2 1.453 0.169 18.9 0.152 17.1 0.016

3 1.529 0.265 30.2 0.155 29.3 0.028

4 1.596 0.361 43.7 0.126 41.9 0.040

5 1.648 0.459 58.7 0.041 55.2 0.054

6 1.685 0.556 72.5 0.015 68.9 0.067

7 1.717 0.656 87.4 0.027 83.2 0.080

8 1.741 0.756 101.7 0.040 97.7 0.093

9 1.754 0.857 117.1 0.027 112.4 0.107

10 1.769 0.958 130.1 0.082 127.1 0.119

11 1.774 1.059 144.7 0.101 142.1 0.132

12 1.780 1.160 159.9 0.104 157.0 0.146

13 1.775 1.275 176.7 0.120 171.1 0.234

14 1.759 1.379 191.6 0.136 181.6 0.339

15 1.734 1.482 203.5 0.200 192.3 0.432

16 1.708 1.586 214.2 0.277 201.9 0.542

17 1.692 1.688 227.3 0.310 211.0 0.651

18 1.666 1.793 238.6 0.372 220.9 0.747

19 1.619 1.898 243.2 0.518 230.0 0.850

20 1.580 2.001 252.5 0.593 237.2 0.973

21 1.544 2.105 260.8 0.676 244.9 1.075

22 1.504 2.209 265.5 0.798 253.0 1.173

23 1.461 2.315 275.3 0.859 259.4 1.289

24 1.411 2.470 283.6 1.006 270.8 1.429

25 1.353 2.627 292.9 1.132 280.0 1.577

26 1.280 2.785 299.8 1.271 286.5 1.741

27 1.219 2.942 304.8 1.417 292.3 1.893

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 237 kJ/m2 (13 Data)

Coeff. C : 283 kJ/m2 Exponent n : 0.20 Fit Coeff. R : 0.988

DC Potential Method JIc : 186 kJ/m2 (15 Data)

Coeff. C : 243 kJ/m2 Exponent n : 0.27 Fit Coeff. R : 0.996
84

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 0.5 1 1.5 2 2.5 3 3.5 4

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JR-20

288°C

Specimen L2-C

Nonirradiated

Figure A-19.1. Load-vs.-loadline displacement curve for specimen

L20–B of irradiated Type 304 SS tested at 288°C

Figure A-19.2. Fracture surface of specimen L20–B tested at 288°C
85 

Table A-20. Test data for specimen L2–A of irradiated Type 304 SS tested at 288°C

Test Number : JR–25 Test Temp. : 288°C

Material Type : Type 304 SS Heat Number : L2

Aging Temp. : – Aging Time : –

Irradiation Temp. : 288°C Fluence : 0.9 x 1021 n/cm2

Thickness : 6.51 mm Net Thickness : 5.84 mm

Width : 11.98 mm Flow Stress : 270.5 MPa

Modulus E : 175 GPa

Initial Crack : 7.38 mm Init. a/W : 0.61 (Measured)

Final Crack : 9.17 mm Final a/W : 0.76 (Measured)

Final Crack : 8.08 mm Final a/W : 0.75 (Compliance)

Load Deflection Unloading Compliance DC Potential Method

No. (kN) (mm) J (kJ/m2) Da (mm) J (kJ/m2) Da (mm)

0 0.089 0.000

1 1.300 0.080 6.5 0.237 6.5 0.006

2 1.453 0.169 18.9 0.152 17.1 0.016

3 1.529 0.265 30.2 0.155 29.3 0.028

4 1.596 0.361 43.7 0.126 41.9 0.040

5 1.648 0.459 58.7 0.041 55.2 0.054

6 1.685 0.556 72.5 0.015 68.9 0.067

7 1.717 0.656 87.4 0.027 83.2 0.080

8 1.741 0.756 101.7 0.040 97.7 0.093

9 1.754 0.857 117.1 0.027 112.4 0.107

10 1.769 0.958 130.1 0.082 127.1 0.119

11 1.774 1.059 144.7 0.101 142.1 0.132

12 1.780 1.160 159.9 0.104 157.0 0.146

13 1.775 1.275 176.7 0.120 171.1 0.234

14 1.759 1.379 191.6 0.136 181.6 0.339

15 1.734 1.482 203.5 0.200 192.3 0.432

16 1.708 1.586 214.2 0.277 201.9 0.542

17 1.692 1.688 227.3 0.310 211.0 0.651

18 1.666 1.793 238.6 0.372 220.9 0.747

19 1.619 1.898 243.2 0.518 230.0 0.850

20 1.580 2.001 252.5 0.593 237.2 0.973

21 1.544 2.105 260.8 0.676 244.9 1.075

22 1.504 2.209 265.5 0.798 253.0 1.173

23 1.461 2.315 275.3 0.859 259.4 1.289

24 1.411 2.470 283.6 1.006 270.8 1.429

25 1.353 2.627 292.9 1.132 280.0 1.577

26 1.280 2.785 299.8 1.271 286.5 1.741

27 1.219 2.942 304.8 1.417 292.3 1.893

Power–Law Fit J = C(Da)n

Unloading Compliance JIc : 237 kJ/m2 (13 Data)

Coeff. C : 283 kJ/m2 Exponent n : 0.20 Fit Coeff. R : 0.988

DC Potential Method JIc : 186 kJ/m2 (15 Data)

Coeff. C : 243 kJ/m2 Exponent n : 0.27 Fit Coeff. R : 0.996
86

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 0.5 1 1.5 2 2.5 3 3.5 4

Measured Extension

Loading–Pin Displacement

Load (kN)

Displacement (mm)

Test JR-20

288°C

Specimen L2-C

Nonirradiated

Figure A-20.1. Load-vs.-loadline displacement curve for specimen L2–A

of irradiated Type 304 SS tested at 288°C

Figure A-20.2. Fracture surface of specimen L2–A tested at 288°C
NRC FORM 335

(2–89)

NRCM 1102,

3201, 3202

U. S. NUCLEAR REGULATORY COMMISSION

BIBLIOGRAPHIC DATA SHEET

(See instructions on the reverse)

2. TITLE AND SUBTITLE

1. REPORT NUMBER

 (Assigned by NRC. Add Vol., Supp., Rev.,

 and Addendum Numbers, if any.)

NUREG/CR–6826

ANL–03/22

3. DATE REPORT PUBLISHED

MONTH YEAR

August 2003

4. FIN OR GRANT NUMBER

Fracture Toughness and Crack Growth Rates of Irradiated

Austenitic Stainless Steels

Y6388

5. AUTHOR(S) 6. TYPE OF REPORT

Technical

7. PERIOD COVERED (Inclusive Dates)

O. K. Chopra, E. E. Gruber, and W. J. Shack

8. PERFORMING ORGANIZATION – NAME AND ADDRESS (If NRC, provide Division, Office or Region, U.S. Nuclear Regulatory Commission, and mailing address; if

contractor, provide name and mailing address.)

Argonne National Laboratory

9700 South Cass Avenue

Argonne, IL 60439

9. SPONSORING ORGANIZATION – NAME AND ADDRESS (If NRC, type “Same as above”: if contractor, provide NRC Division, Office or Region, U.S. Nuclear

Regulatory Commission, and mailing address.)

Division of Engineering Technology

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555–0001

10. SUPPLEMENTARY NOTES

William H. Cullen, Jr., and Carol E. Moyer, NRC Project Managers

11. ABSTRACT (200 words or less)

Austenitic stainless steels (SSs) are used extensively as structural alloys in the internal components of reactor pressure

vessels because of their superior fracture toughness properties. However, exposure to high levels of neutron irradiation for

extended periods leads to significant reduction in the fracture resistance of these steels. Experimental data are presented on

fracture toughness and crack growth rates (CGRs) of austenitic SSs irradiated to fluence levels up to 2.0 x 1021 n/cm2 (E > 1

MeV) (a3.0 dpa) at a288°C. Crack growth tests were conducted under cycling loading and long hold time trapezoidal loading

in simulated boiling water reactor (BWR) environments, and fracture toughness tests were conducted in air. Neutron

irradiation at 288°C decreases the fracture toughness of the steels; the data from commercial heats fall within the scatter

band for the data obtained at higher temperatures. In addition, the results indicate significant enhancement of CGRs of the

irradiated steels in normal water chemistry BWR environment; the CGRs for irradiated steels are a factor of a5 higher than

the disposition curve proposed for sensitized austenitic SSs. The rates decreased by more than an order of magnitude in

low–dissolved–oxygen BWR environment.

12. KEY WORDS/DESCRIPTORS (List words or phrases that will assist researchers in locating this report.) 13. AVAILABILITY STATEMENT

Unlimited

14. SECURITY CLASSIFICATION

(This Page)

Unclassified

(This Report)

Unclassified

15. NUMBER OF PAGES

Fracture Toughness

J–R Curve

Crack Growth Rate

Neutron Irradiation

BWR Environment

Dissolved Oxygen

Austenitic Stainless Steels

16.ICE PR

NRC FORM 335 (2–89)
Printed 

on recycled 

paper

Fdl RliP