Development of small specimen test techniques for the IFMIF test cell

Transcription

1 1 FTP/P7-15 Development of small specimen test techniques for the IFMIF test cell E. Wakai 1), B. Kim 1), T. Nozawa 1), T. Kikuchi 1), M. Hirano 1), A. Kimura 2), R. Kasada 2), T. Yokomine 2), T. Yoshida 2), S. Nogami 3), H. Kurishita 3), Y. Itoh 4), K. Abe 4), M. Saito 4), A. Nishimura 5), K. Kondo 6), F. Arbeiter 6), V. Heinzel 6), P. Jacquet 7), V. Massaut 7), M. Sugimoto 1), T. Nishitani 1) 1) Japan Atomic Energy Agency, Ibaraki, Japan 2) Kyoto Univ., 3) Tohoku Univ., 4) College of Hachinohe, 5) National Institute for Fusion Science, 6) Karlsruhe Institute of Technology, 7) SCK CEN contact of main author: Abstract. Recent progress of small specimen test technique (SSTT) and the engineering design and engineering validation tests of high flux test module (HFTM) for the IFMIF (International Fusion Materials Irradiation Facility) test cell is mainly summarized and evaluated in the IFMIF/EVEDA (Engineering validation and engineering design activities) projects under Broader Approach (BA) Agreement between EURATOM and Japan. The evaluation of the optimization of shape and size of specimen and the arrangement is very important for SSTT of IFMIF. Effects of specimen size on mechanical properties such as impact properties and ductile-to-brittle transition temperature (DBTT) are known to occur in ferritic/martensitic steels, and some parts of them have been prepared in the guideline and standard of mechanical tests by ASTM-international and ISO. However, our research of ferritic/martensitic steel F82H shows that it does not match with our data, i.e., master curve method for fracture in ductile-to-brittle transition behaviour of F82H steel. Accordingly, we need to modify and develop these standards for the tests including small size specimens of fusion materials in IFMIF. In the design of HFTM, two types are preparing for RAF/M steels by EU KIT team and for the advanced materials by JA team, respectively. 1. Introduction Structural materials and functional materials of fusion nuclear reactors will be exposed to neutrons with energies up to about 14 MeV at about 3.5 MW/m 2 (5.0 MW/m 2 at the peak) with a fluence up to more than 10 MWy/m 2 during the operation [1]. Radiation damage of materials in fusion reactor environment can be characterized by synergistic effects of displacement damage and nuclear transmutation products such as hydrogen and helium atoms [2-7]. These damages will induce the degradation of mechanical properties. In order to safely operate fusion nuclear reactors, the detailed behaviour of material degradation with respect to 14 MeV neutrons dose must be known. The International Fusion Materials Irradiation Facility (IFMIF) [8,9] is a deuterium-lithium neutron source with high intensity for irradiation experiments of candidate fusion reactor materials to prepare database obtained from series of tests such as small size specimens for the DEMO s design and licensing. About one thousand small size specimens will be irradiated in the IFMIF-High Flux Test Module (HFTM) with a limited volume of about 0.5 liter [10]. Under Broader Approach (BA) Agreement between EURATOM and Japan, IFMIF/EVEDA (International Fusion Materials Irradiation Facility/Engineering Validation and Engineering Design Activities) has been performing from a middle of The IFMIF has three main facilities such as the accelerator Facility, Li Target Facility and Test Facilities as shown in FIG.1. A previous design report of IFMIF was summarized in IFMIF comprehensive design report [8]. The present EVEDA phase aims at producing a detailed, complete and fully integrated engineering design of IFMIF.

2 2 FTP/P7-15 Accelerators Lithium Target 25 ± 1 mm thick x 260 mm width, 15 m/s, 250C, (Deuteron Beams 40 MeV-125 ma x 2, Continuous wave) MEBT Ion LEBT RFQ HWR-SRFL HEBT Source H M L Test Cell 140 mad kev 5 MeV MeV RFPS RFPS(175MHz CW) Beam shape: High (>20 dpa/y, 0.5 L) 200 x 50 mm 2 Medium (>1 dpa/y, 6 L) Low (<1 dpa/y, >8 L) FIG. 1. IFMIF system composed by mainly two accelerators, Li target and test cell 2. Small Size Specimen Technique The main objective of IFMIF is to obtain the material data base obtained from a series of tests using small specimens mainly irradiated in the IFMIF for the design and licensing of fusion DEMO and power reactors. The irradiation volume of the IFMIF is 12.5 liters (L) in the total, and the highest displacement damage is more than 20 dpa (displacement per atom)/year in a volume of 0.5 L. Therefore, we have to use small size specimens for it, and small specimen test technique or technology (SSTT) is very important. In the IFMIF/EVEDA program, some of SSTT such as fracture toughness, fatigue and fatigue crack-growth measurement are performed by some universities as a collaboration study. For mechanical tests using small specimens, high accuracy controllability in the applied stress and displacement is required. Some guidelines and standard of mechanical tests have been prepared by ASTM-international and ISO [11] as given in TABLE 1. We had examined the specimen size effect on DBTT of reduced-activation ferritic/martensitic (RAF/M) steel, F82H, by Chapry impact test [12]. The dependence of specimen size on DBTT had already been studied by using pressure vessel steel, A533B, however the dependence of specimen size in F82H steel on DBTT was different from that in A533B steel. Furthermore, our research for F82H steel shows that our data does not match with the ASTM master curve based on the data of A533B steel for the evaluation of ductile to brittle transition behaviour. The dimensions of from 1T C(T) to 0.16T C(T) (Thickness, Compact (Tension) type) tested in this study is shown in FIG.2. The normalized fracture toughness of from a small specimen 0.16T C(T) to a standard size specimen 1T C(T) as a function of temperature is shown in FIG.3, and DBTT was ranged from -113 o C to 100 o C [13]. The master curve of fusion structural materials of ferritic/martensitic steel F82H is better to be modified as K JC(med) = exp{0.19(t-t o )}, where K JC(med) is a mediated fracture toughness and T o is a reference temperature, while the original ASTM master curve is presented as K JC(med) = exp{0.05(T-T o )}. Summary of analysis of ductile-to brittle transition behaviour of F82H using ASTM Master curve analysis and the modified curve analysis in this study is given in TABLE 2 [13]. Accordingly, we would have to modify and develop these standards for the tests including small size specimens in IFMIF in the application of test standard for fusion materials.

3 3 FTP/P7-15 TABLE 1. The guideline and status of test methodology in ASTM international, ISO, JIS, and JSME. Test Item ASTM, ISO JIS, JSME Tensile -ASTM E8M-04 (Tension testing of metallic materials), -ASTM E646-00(Tensile strain-hardening exponents (n- Values) of metallic sheet materials, -ISO 6892 Fracture Toughness Charpy Impact Fatigue Creep Fatigue Crack Growth Rates -ASTM E (Plane-strain fracture toughness of metallic materials) -ASTM E (J IC, a measure of fracture toughness) - ASTM E (Plane-strain (Chevron-Notch) fracture toughness of metallic materials, -ASTM E a (Measurement of fracture toughness) (No restrict of specimen size) -ASTM E (Determination of reference temperature, for ferritic steels in the transition range) -ISO 12135:2002 -ASTM E23-05, ISO 148 (Notch bar impact testing of metallic materials) -ASTM E 2248 on miniature Charpy specimens is currently being balloted. -ISO 14556:2000 (instrumented tests) includes KLST specimens. -E606 (Strain-controlled fatigue testing) -E (Statistical analysis of linear or linearized stresslife (S-N) and strain-life(ε-n) fatigue data -ASME SA-213/SA-213M Grade T91 for tube, - ASME SA-387/SA-387M Grade 91 for plate -ASTM A542/A542M for 2.25Cr-1Mo(plate) -E (Measurement of fatigue crack growth rates) JIS Z 2241 (Tensile testing in metals) JSME S 001 (Standard method of test for elastic-plastic fracture toughness, J IC) JIS Z 2242 (Charpy impact testing in metals) JSME S 002 (Standard method of statistical fatigue testing) JIS Z 2271 (Creep and creep fracture testing in metals) Standard Test Method for Stress Corrosion Cracking edited by the 129th Committee on Strength and Fracture of Advanced Materials, Society of Materials Science, Japan 1 CT 1/ 2 CT 1/ 4 CT 0.16 CT FIG.2. The dimensions of from 1T C(T) to 0.16T C(T) tested in this study

4 4 FTP/P7-15 (a) ASTM Master curve (b) Modified curve FIG.3. Evaluation of ductile-to-brittle transition behaviour of F82H steel using ASTM Master curve (a) and the modified curve in this study (b). TABLE 2. Summary of analysis of ductile-to brittle transition behaviour of F82H using ASTM Master curve analysis and the modified curve analysis in this study ASTM Master curve analysis Modified curve analysis Data Specimen T 0 ( o C) Out of Reliability T 0 ( o C) Reliability Number of size data data 1 CT % % 20 1/2 CT % % 28 1/4 CT % % CT % % 38 All of them % % High Flux Test Module In the design of HFTM, two types are proposed for RAF/M steels by EU KIT team and for the advanced materials by JA team, respectively. The former type has 12 (4 sets x 3 layers) rigs or 24 (8 x 3) rigs instrumented inside HFTM. The size of one rig is 11.6 mm in thickness and 50 mm in width and 81 mm in height in the design of KIT team, and the size in height is larger than the neutron beam footprint size with 50mm in height and 200 mm in width. In HFTM, liquid NaK is used as a heat medium for small size specimens such as tensile and fatigue specimens, and the upper limitation temperature would be up to 550 o C. If it needs to test at higher temperatures than 550 o C, we would have to use helium gas as a heat medium. The latter type of HFTM developed by JA team for use at temperatures up to 1,000 o C is shown in FIG.4, and the module design with 9 set-capsules (3 sets x 3 layers) is set in horizontal direction. The size of one capsule is 15 mm in height and 200 mm in width, and the regime of the capsule in HFTM just corresponds to the foot print size of neutron beam. In the tests and engineering design, W-3%Re alloy and SiC f /SiC composites were selected as heater materials and the type R (Pt-Rh alloy and Pt) was chosen as thermocouples because of their phase stability during irradiation. The irradiation tests in BR2 reactor in Belgium is preparing for the engineering validation tests in IFMIF/EVEDA project. 6. Conclusion

5 5 FTP/P7-15 Recent progress of small specimen test technique (SSTT) and the engineering design and engineering validation tests of high flux test module (HFTM) for the IFMIF (International Fusion Materials Irradiation Facility) test cell is mainly summarized and evaluated in the IFMIF/EVEDA (Engineering validation and engineering design activities) projects under Broader Approach (BA) Agreement between EURATOM and Japan as below; (i) The evaluation of the optimization of shape and size of specimen and the arrangement is very important for IFMIF small size specimens. Effects of specimen size on mechanical properties such as impact properties and ductile-to-brittle transition temperature (DBTT) are known to occur in ferritic/martensitic steels, and some parts of them have been prepared in the guideline and standard of mechanical tests by ASTM-international and ISO. However, our research of ferritic/martensitic steel F82H shows that it does not match with our data, i.e., master curve method for fracture in ductile-to-brittle transition behaviour of F82H steel. Accordingly, we need to modify and develop these standards for the tests including small size specimens of fusion materials in IFMIF. (ii) In the engineering design and validation test of HFTM, two types are preparing for RAF/M steels by EU KIT team and for the advanced materials by JA team, respectively. In the HFTM, liquid NaK is used as a heat medium for small size specimens such as tensile and fatigue specimens, and the upper limitation temperature would be up to 550 o C. If it needs to test at higher temperatures than 550 o C, we would have to use helium gas as a heat medium. The latter type of HFTM developed by JA team for use at temperatures up to 1,000 o C is under evaluating. Rig Holder Lower Supporter Side Reflector Specimens HFTM Flow Straightener FIG.4. The developed HFTM with W-Re or SiC f /SiC composite heater. Reference [1] M. Enoeda, Y. Kosaku, T. Hatano, et al., Design and technology development of solid breeder blanket cooled by solid breeder blanket, Nucl. Fusion 43 (2003) [2] E. Wakai, N. Hashimoto, Y. Miwa, et al., Effects of helium production on swelling of F82H irradiated in HFIR, J. Nucl. Mater (2000)799.

6 6 FTP/P7-15 [3] E. Wakai, T. Sawai, K. Furuya, et al., Effect of triple ion beams in ferritic/martensitic steel on swelling behavior, J. Nucl. Mater (2002)278. [4] E. Wakai, K. Kikuchi, S. Yamamoto, et al., Swelling behavior of F82H steel irradiated by triple/dual ion beams, J. Nucl. Mater. 318(2003)267. [5] E. Wakai, M. Ando, T. Sawai, et al., Effect of gas atoms and displacement damage on mechanical properties and microstuctures of F82H, J. Nucl. Mater. 356(2006)95. [6] T. Tanaka, K. Oka, S. Ohnuki, et al., Synergistic effect of helium and hydrogen for defect evolution under multi-ion irradiation of Fe-Cr ferritic alloys, (2004) [7] T. Taguchi, N. Igawa, S. Miwa, et al., Synergistic effects of implanted helium and hydrogen and the effect of irradiation temperature on the microstructure of SiC/SiC composites, 335(2004)508. [8] IFMIF Comprehensive Design Report, by the international Team, an Activity of the international Energy Agency, Implementing Agreement for a program of Research and Development on Fusion Materials, January [9] P. Garin, Start of the engineering validation and design phase of IFMIF, J. Nucl. Mater (2009)944. [10] D. Leichtle, F. Arbiter, B. Dolensky, et al., Design optimization and experimental testing of the High-Flux Test Module of IFMIF, J. Nucl. Mater (2009)954. [11] E. Wakai, et al., Design plan and requirement of test module and testing items in IFMIF, Fus. Eng. Des., 86 (2011)712. [12] E. Wakai, et al., " Small specimen test technology and methodology of IFMIF/EVEDA and the further subjects ", J. Nucl. Mater., 417(2011)1325. [13] B. Kim, E. Wakai, R. Kasada, A. Kimura, Developement of small specimen test technique on fracture toughness for reduced-activation ferritic steels, Fus. Eng. Des., submitted.