NUREG/CR-4667 ANL-9719 VOl. 22 Environmentally Assisted Cracking in Light Water Reactors Semiannual Report January 1996 - June 1996 Manuscript Completed: May 1997 Date Published: May 1997 Prepared by 0. K.C hopra, H. M. Chung, D. J. Gavenda, E. E. Gruber, T. H. Hughes, T. F. Kassner, P. R. Luebbers, J. -H. Park, T. T. Pleune, W. E. Ruther, W. J. Shack, W. K. Soppet, R. V. Strain Argonne National Laboratory 9700 South Cass Avenue Argonne, IL 60439 M. McNeil, NRC Project Manager Prepared for MASTE Division of Engineering Technology Office of Nuclear Regulatory Research DISCLAIMER U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 This report was prepared as an account of work sponsored by an agency of the United States NRC Job Code W6610 Government. Neither the United States Government nor any agency thereof, nor any,of their employees. makes any warranty, express or implied, or assumes any legal liability or responsi- bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Refcr- ence herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom- mendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. WSTRlBUTlON OF THIS DOCUMENT IS UNLlMlP ED Previous Documents in Series Environmentally Assisted Cracking in Light Water Reactors Semiannual Report April-September 1985, NUREG/CR-4667 Vol. I, ANL-86-3 1 (June 1986). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report October 1985- March 1986, NUREG/CR-4667 Vol. 11, ANL-86-37 (September 1987). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report April-September 1986, NUREG/CR-4667 Vol. 111, ANL-87-37 (September 1987). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report October 1986- March 1987, NUREG/CR-4667 Vol. IV,A NG87-41 (December 1987). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report April-September 1987, NUREG/CR-4667 Vol. V,A NGs8-32 (June 1988). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report October 1987- March 1988, NUREG/CR-4667 Vol. 6, ANL-89/ 10 (August 1989). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report April-September 1988, NUREG/CR-4667 Vol. 7, ANG89/40 (March 1990). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report October 1988- March 1989, NUREG/CR-4667 Vol. 8,A NG90/4 (June 1990). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report April-september 1989, NUREG/CR-4667 Vol. 9, ANL-90/48 (March 1991). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report October 1989- March 1990, NUREG/CR-4667 Vol. 10, ANL-91/5 (March 1991). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report April-September 1990, NUREGjCR-4667 Vol. 11, ANL-91/9 (May 1991). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report October 1990- March 1991, NUREG/CR-4667 Vol. 12, ANL-9 1/ 24 (August 199 1). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report April-September 1991, NUREG/CR-4667 Vol. 13, ANL-92/6 (March 1992). I Environmentally Assisted Cracking in Light Water Reactors Semiannual Report October 1991- March 1992, NUREG/CR-4667 Vol. 14, ANG92/30 (August 1992). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report April-September I 1992, NUREG/CR-4667 Vol. 15, ANG93/2 (June 1993). Enviro king in Light Water Reactors Semiannual Report October 1992- March 7 Vol. 16, ANG93/27 (September 1993). En&o king in Light Water Reactors Semiannual Report April-September 1993, 17, ANL-94/26 (June 1994). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report October 1993- March 1994, NUREG/CR-4667 Vol. 18, ANL-95/2 (March 1995). I Environmentally Assisted Cracking in Light Water Reactors Semiannual Report April-September 1994, NUREG/CR-4667 Vol. 19, ANL-95/25 (September 1995). Environmentally Assisted Cracking in Light Water Reactors Semiannual Report October 1994- March 1995, NUREG/CR-4667 Vol. 20, ANL-95/4 1 (January 1996). I Environmentally Assisted Cracking in Light Water Reactors Semiannual Report April-December 1995, NUREG/CR-4667 Vol. 2 1, ANG96/ 1 (July 1996). NUREG/CR4667, Vol. 22 ii I DISCLAIMER Portions of this document m y b e illegiiIe in electronic image produds. Images are produced from the best available original dOCUIIlent, Environmentally Assisted Cracking in Light Water Reactors Semiannual Report January 199Wune 1996 0. K. Chopra, H. M. Chung, D. J. Gavenda, E. E. Gruber, T. H. Hughes, T. F. Kassner, P. R. Luebbers, J.-H. Park, T. T. Pleune. W. E. Ruther, W. J. Shack, W. K. Soppet, and R. V. Strain Abstract This report summarizes work performed by Argonne National Laboratory on fatigue and environmentally assisted cracking (EAC) in light water reactors from January 1996 to June 1996. Topics that have been investigated include (a) fatigue of carbon, low-alloy, and austenitic stainless steels (SSs) used in reactor piping and pressure vessels, (b) irradiation- assisted stress corrosion cracking of Type 304 SS, and (c) EAC of Alloys 600 and 690. Fatigue tests were conducted on ferritic and austenitic SS s in water that contained various concentrations of dissolved oxygen (DO) to determine whether a slow strain rate applied during various portions of a tensile-loading cycle are equally effective in decreasing fatigue life. Slow-strain-rate-tensile tests were conducted in simulated boiling water reactor (BWR) water at 288°C on SS specimens irradiated to a low fluence in the Halden reactor and the results were compared with similar data from a control-blade sheath and neutron-absorber tubes irradiated in BWRs to the same fluence level. Crack-growth-rate tests were conducted on compact-tension specimens from several heats of Alloys 600 and 690 in air and high-purity, low-DO water. iii NUREG/CR-4667, Vol. 22 Contents Executive Summary .......................................................................................................... xi Acknowledgments ............................................................................................................. xiii Introduction ............................................................................................................... 1 Environmental Effects on Fatigue Strain-versus-Life (S-N) Behavior of Primary Pressure Boundary Materials ..................................................................................... 2 2.1 Carbon and Low-Alloy Ferritic Steels ................................................................ 5 2.2 Effects of Loading Conditions on Fatigue Life .................................................... 11 2.3 Crack Initiation and Crack Growth Characteristics ........................................... 20 2.4 Austenitic Stainless Steels ................................................................................ 30 Irradiation Assisted Stress Corrosion Cracking of Austenitic SS .................................. 39 3.1 Slow-Strain-Rate-Tensile Tests of Austenitic Stainless Steels Irradiated in the Halden Reactor ................................................................................................. 40 3.2 Properties of Stainless Steel Welds .................................................................... 43 3.3 Development of Hot-Cell J-R Testing Facility ..................................................... 48 Environmentally Assisted Cracking of Alloys 600 and 690 in Simulated LWR Water ... 49 4.1 Experimental Methods for CGR Measurements on Alloys 600 and 690 .............. 49 4.2 CGRs of Mill-Annealed Alloy 600 and Thermally Treated Alloy 690 in Air at 35. 130. and 289°C ........................................................................................... 52 4.3 CGRs ofAlloy 690 in HP Deoxygenated Water at 289 and 32OOC ....................... 56 4.4 CGRs of Alloys 600 and 690 in HP Deoxygenated Water at 240 and 320°C ........ 57 4.5 Comparison of CGRs of Alloys 600 and 690 in HP Deoxygenated Water and Air .................................................................................................................... 60 4.6 Morphology of Crack Path and Surface of Alloy 600 and 690 Specimens ........... 63 Summary of Results ................................................................................................... 68 5.1 Environmental Effects on Fatigue S-N Behavior of Primary Pressure Boundary Materials .......................................................................................... 68 5.2 Irradiation Assisted Stress Corrosion Cracking .................................................. 70 5.3 EAC of Alloys 600 and 690 in Simulated LWR Water ......................................... 71 References ......................................................................................................................... 73 V NUREG/CR-4667. Vol . 22 Figures 1. Fatigue S-N behavior for CSs and LASs in air at room temperature and 250- 300°C ...................................................................................................................... a 2. Fatigue S-N behavior of A106-Gr B and A533-Gr B steels, estimated from a statistical model and determined experimentally in high-DO water at 288°C.. .. . . . . . . . . 11 3. Schematic representation of fully connected neural network with four input neurons, two hidden layers, and one output neuron .. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4. Experimental values of fatigue life of CSs and LASs and those predicted by artificial neural network in air and water environments ............................................ 15 5. Dependence of fatigue life on temperature for CSs and LASs in air at 0.4 and 0.004?40/s strain rates .............................................................................................. 17 6. Dependence of fatigue life on tensile strain rate for CSs and LASs in air at room temperature and 288°C .. .. . .. . . . . . . .. . . . .. .. .. . . . .. . . . .. . . .. .. . .. .. .. . . . . . . . .. .. .. . . . .. . . . . .. ... .. . . . . . . . .. . .. .. .. 17 7. Dependence of fatigue life on sulfur content of CSs and LASs in air at 0.4 and 0.004%/s strain rates .............................................................................................. 18 8. Dependence of fatigue life on temperature for CSs and LASs in water at 0.4 and 0.004%/s strain rates ....... . . . . . . .. . .. . . . . .. . . . . . . .. . . . .. . . .. .. . . . . . . .. . .. . . . . . . . .. . . . . .. . . . . .. . .. .. .. . . . . . . . .. ... 18 9. Dependence of fatigue life on DO for CSs and LASs in water at 0.4 and 0.004%/s strain rates .............................................................................................................. 19 10. Dependence of fatigue life on tensile strain rate for CSs and LASs in water containing 0.2 and 1. O ppm DO .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 11. Dependence of fatigue life on sulfur content of CSs and LASs in water at 0.4 and 0.004?40/s strain rates ..... ... ......... .. ........ . .... ... ....... .......... ............. ............. ........... ..... 20 12. Two stages of fatigue crack growth in smooth test specimens ................................... 21 13. Growth of cracks in smooth fatigue specimens ......................................................... 22 14. Formation of surface cracks along slip bands, carbide particles, and femte/pearlite phase boundaries of A106-Gr B steel ............................................... 23 15. Schematic illustration of film rupture/slip dissolution process .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 16. Schematic illustration of hydrogen-induced cracking of low-alloy steels .. . . . . . . . . . . . . . . . . . 24 NTJREG/CR-4667, Vol. 22 vi 17. Morphology and length of surface crack after varying numbers of cycles for A533- Gr B steel tested in air at room temperature, 0.75% strain range, and slow/fast saw-tooth waveform .. .. .. . .. .. .. .. . .. .. .. .. . .. .. .. . . . .. .. .. . .. .. .. .. ... .. .. . . . . . .. .. .. .. .. . .. .. .. .. ... .. . . ... . . ..... 26 18. Fracture surface and probable crack front after varying numbers of fatigue cycles for surface crack shown in Fig. 17. ........................................................................... 26 19. Beach marks produced by four of five block loading sequences on the fracture surface of A533-Gr B steel tested at 288°C in high-DO water ................................... 27 20. Fatigue lives of A533-Gr B steel tested in air at room temperature and in high- DO water at 288°C ................................................................................................... 28 2 1. Photomicrographs of fractured specimen from tests that were interrupted every 50 and 30 cycles and subjected to block loading at lower strain range ...................... 28 22. Depth of largest crack plotted as a function of fatigue life or fractional life for A533-Gr B low-alloy steel tested in air and water environments ............................... 29 23. Crack depth plotted as a function of fractional life for CSs and LASS tested in room-temperature air.. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 24. Crack growth rates plotted as a function of crack size for A533-Gr B LAS tested in air and water environments ................................................................................. 29 25. Fatigue S-N behavior for Types 304, 316. and 316NG S S s in air at various temperatures ........................................................................................................... 31 26. Total strain range-versus-fatigue-life data for Types 3 16NG and 304 SS in air.. .. . . . . . . 34 27. Effect of strain range on cyclic strain-hardening behavior of Type 316NG SS in air at room temperature and 288°C and 0.4%/s strain rate ...... . .. .. .. . . . . . . . .. .. .. .... .. ...... 34 28. Effect of strain rate on cyclic strain-hardening behavior of Types 316NG and 304 SS in air at 288°C .................................................................................................... 35 29. Cyclic stress-strain curve for Types 304, 316, and 316NG SS in air at room temperature, 288, and 288-430°C ............................................................................ 35 30. Effect of strain rate on cyclic stress-strain curve for Type 3 16 SS in air .. .. . .... ... .. .. .. .. 36 31. Total strain range-versus-fatigue-life data for Types 316 NG and 304 SS in air and water ....... .......... ............... ... ............ .. .... ...... ..... ............ .................................... 37 32. Cyclic strain-hardening behavior of Type 3 16NG SS in air and PWR water at 288°C ...................................................................................................................... 37 33. Effect of strain rate on fatigue lives of austenitic SSs in air, and simulated PWR and high-DO water environments .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 vii NUREG/CR4667, Vol. 22 34. Photomicrographs of fracture surface of Type 316NG SS specimens tested at 288°C and 0.75%s train range in air, high-DO water, and simulated low-DO PWR water ... ... .. .. . .. . ... .. . .. . . . . .. . .. .. .. .. .. . .. .. .. . .. .. .. .. . . . .. .. .. . . . . . .. .. . . . . . .. .. .. . .. . . .. . . . . ... .. . .. .. . . . .. .. .. ..... 38 35. SEM photomicrographs of gage surface of Type 316NG SS specimens tested in air, simulated PWR, and high-DO water environments ............................................. 39 36. Stress-versus-strain of commercial heat C1 of Type 304 SS irradiated in Halden reactor, and of BWR components irradiated and tested under similar conditions.. .. . . 42 37. Percent IGSCC of SS heats irradiated in helium in the Halden reactor to a fluence ~ 0 . 4 5x 1021 ncm-2 (E > 1 MeV). .............................................................................. 43 38. Susceptibility to IGSCC versus bulk oxygen content of specimens from Type 304 SS BWR components irradiated to a fluence of =2 x 1021 ncm-2 (E > 1 MeV) ............ 43 39. SEM image of cross section of welding electrode used for shielded metal arc welding .. .. .. . . . . . .. .. . . . . . .. .. .. . . . . . .. . . .. .. . . . . . .. .. . . . .. ... .. . . .. .. . . . . . .. .. .. . . , . . .. ..... .. . . . . . . .. .. .. .. .. .. . ..... .. . 45 40. EDS spectrum obtained from cross section of welding electrode used for shielded metal arc welding, showing CaF2 ............................................................................. 45 41. Composition of SMA and GTA welds o f m e 3 04, 304L, and 316 SS ......................... 46 42. Fluorine concentration profiles in fusion and heat-affected zones of SMA weld of Type 304 SS, Heat C1, determined by SIMS technique ............................................ 48 43. Dependence of the CGR of Alloys 600 and 690 on AK in air at 35, 130, and 289°C and data at three temperatures ................................................................................ 55 44. Combined data at 35, 130, and 289OC for the dependence on AK of CGRs of Alloys 600 and 690 in air ......................................................................................... 55 45. Calculated versus experimental CGRs for Alloys 600 and 690 in air ........................ 56 46. Calculated CGRs for Alloys 600 and 690 in air versus AK for stress intensity factors between 33 and 100 MPaml/2 and load ratios of 0.1-0.98 from Eqs. 16- 18, and calculated CGRs/AK3.O29 versus R, which illustrates that S(R) relationships in Eqs. 17 and 18 adequately account for R dependence in Eq. 16... . . . . 56 47. Dependence of CGRs on AK of Alloy 690 specimens from two heats with differing heat treatment conditions in deoxygenated HP water at 289 and 320°C. ................... 57 48. Crack growth rate of Alloys 600 and 690 in HP deoxygenated water at 240 and 320°C versus AK ...................................................................................................... 60 49. Combined data for dependence on AK of crack growth rate of Alloys 600 and 690 in HP deoxygenated water at 240 and 320°C ............................................................ 61 NUREG/CR-4667, Vol. 22 viii 50 . Dependence of CGRs of Alloy 690 specimens in HP deoxygenated water on AK at 240. 289. and 320°C and combined results at the three temperatures ...................... 61 51. Dependence on AK of ratio of CGRs of Alloys 600 and 690 at 289°C and combined data at 240-320°C in HP deoxygenated water to CGRs in air at 289OC . and ratio of CGRs from combined data at 240-320°C in HP deoxygenated water to CGRs from combined data in air at 35-289OC ..................................................................... 63 52. Crack path. fracture surface. and fracture morphology of lTCT specimen of Alloy 600 (No. 526-03) after crack growth experiment in air at 35 and 130°C. ................... 64 53. Crack path. fracture surface. and fracture morphology of 1 K T specimen of Alloy 690 (No. HlB-03) after crack growth experiment in air at 35 and 130°C. .................. 64 54. Crack path. fracture surface. and fracture morphology of lTCT specimen of Alloy 600 (No. 197-10) after crack growth experiment in air at 289°C ............................... 65 55. Crack path. fracture surface. and fracture morphology of lTCT specimen of Alloy 690 (No. HG-10) after crack growth experiment in air at 289°C ................................ 65 56 . Crack path. fracture surface. and fracture morphology of lTCT specimen of Alloy 600 (No. 526-01) after crack growth experiment HP water at 240 and 320°C ............ 66 57. Crack path. fracture surface. and fracture morphology of lTCT specimen of Alloy 690 (No. G21-01) after crack growth experiment in HP water at 240 and 32OOC ....... 66 58 . Crack path. fracture surface. and fracture morphology of lTCT specimen of Alloy 690 (No. G21-02) after crack growth experiment in HP water at 289 and 320°C ....... 67 59 . Crack path. fracture surface. and fracture morphology of lTCT specimen of AUoy 690 (No. KlA-01) after crack growth experiment in HP water at 289 and 320°C ....... 67 60 . Crack path. fracture surface. and fracture morphology of lTCT specimen of Alloy 690 (No. KlI3-01) after crack growth experiment in HP water at 289 and 320°C ....... 68 Tables 1. Chemical and strength specifications for carbon and low-alloy steels ....................... 6 2. Fatigue results for A533-Gr B steel in air and water environments ........................... 25 3. Composition of austenitic stainless steels used for fatigue tests ................................ 32 4 . Fatigue test results for Qpe 316NG austenitic stainless steel ................................... 33 5. Fatigue test results for Type 304 austenitic stainless steel ....................................... 34 ix NUREG/CR-4667. Vol . 22