Hirose, Takanori; Sokolov, M. A.*; Ando, Masami; Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Stoller, R. E.*; Odette, G. R.*
Journal of Nuclear Materials, 442(1-3), p.S557 - S561, 2013/11
Kim, G.; Shiba, Kiyoyuki; Sawai, Tomotsugu; Ioka, Ikuo; Kiuchi, Kiyoshi; Nakayama, Jumpei*
Proceedings of 2nd International Workshop on Structural Materials for Innovative Nuclear Systems (SMINS-2), p.273 - 279, 2012/12
Shiba, Kiyoyuki; Tanigawa, Hiroyasu; Hirose, Takanori; Sakasegawa, Hideo; Jitsukawa, Shiro
Fusion Engineering and Design, 86(12), p.2895 - 2899, 2011/12
Aging properties of reduced activation ferritic/martensitic steel F82H was researched at temperature ranging from 400C to 650C up to 100,000 hr. Microstructure, tensile, and Charpy properties were carried out. Laves was found at temperatures between 550 and 650C and MC carbides were found at the temperatures between 500 and 600C over 10,000 hr. These precipitates caused degradation in toughness, especially at temperatures ranging from 550C to 650C. Tensile properties do not have serious aging effect, except for 650C, which caused large softening even after 10.000 hr. Increase of precipitates also causes some degradation in ductility, but it is not critical. Large increase in DBTT caused by the large Laves phase precipitation at grain boundary was observed in the 650C aging. Laves precipitates at grain boundary also degrades the USE of the aged materials. These aging test results provide F82H can be used up to 30,000 hr at 550C.
Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Mslang, A.*; Stoller, R. E.*; Lindau, R.*; Sokolov, M. A.*; Odette, G. R.*; Kurtz, R. J.*; Jitsukawa, Shiro
Journal of Nuclear Materials, 417(1-3), p.9 - 15, 2011/10
ITER construction was started, and R&D toward DEMO shifted to more practical stage. On this stage, the candidate material for DEMO blanket have to be the one which have sound engineering bases to be ready for engineering designing activity for DEMO reactor in 10 years. Reduced activation ferritic/martensitic (RAFM) steels, such as F82H (Fe-8Cr-2W-0.2V-0.04Ta) or EUROFER97 (Fe-9Cr-1W-0.2V- 0.12Ta), is the only material which currently have enough potential to meet this requirement, and selected as the target material in the R&D on materials engineering for DEMO blanket under the International Fusion Energy Research Centre (IFERC) project in the Broader Approach (BA) activities between EU and Japan. In this paper, current status of RAFM R&D is overviewed especially on fabrication technology, inspection/testing technology, and material database. Overview on irradiation effect study is also provided.
Kim, G.; Shiba, Kiyoyuki; Sawai, Tomotsugu; Ioka, Ikuo; Kiuchi, Kiyoshi
Materials Research Society Symposium Proceedings, Vol.1298, p.61 - 66, 2011/04
The irradiation behaviour in two different precipitation hardening types of Ni-base alloys with the ultra high purity grade (EHP), namely, the ' type and G phase type was investigated by multi-ion beam techniques simulated to the irradiation conditions in fuel cladding tubes used in sodium cooled FBRs. Single ion-beam irradiation tests were conducted up to 90 dpa (by Fe or Ni) at 673 K. Triple ion-beam irradiation tests were conducted up to 90 dpa (by Ni, 90 appmHe and 1350 appmH) at 823 K. The irradiation behaviour was examined by nano-indentation tests to irradiation hardening, and the microscopic observation by TEM to the distribution of dislocations, cavities and voids. The behaviour was compared with those of PNC316. The dominating irradiation defects in EHP(') alloy at 673 K by single ion-beam are Frank loops, perfect unfaulted loops and line dislocations. Whereas, those of EHP(WSi) alloy are the irradiation-induced G phase precipitates along planes. Those dominating defect structures at 823 K by triple ion-beam are classified as followings, bimodal distributions in EHP('), bubbles in EHP(WSi) and voids in PNC316. The ratio of void swelling is estimated as nearly 0.01% in EHP(WSi), 0.2% in EHP('), 3.4% in PNC316. From those results, the excellent irradiation properties of EHP(WSi) alloy is clarified as the inhibition effects of secondary irradiation defects.
Jitsukawa, Shiro; Suzuki, Kazuhiko; Okubo, Nariaki; Ando, Masami; Shiba, Kiyoyuki
Nuclear Fusion, 49(11), p.115006_1 - 115006_8, 2009/11
Irradiation often causes hardening and reduction of elongation as well as toughness degradation to a considerable degree. Data, however, indicate that these changes remain in manageable ranges for ITER-TBM application. Moreover, the saturation tendency of the changes with neutron dose suggests that some of the reduced activation martensitic steels are feasible even for future DEMO applications. It is also stressed that the development of a design methodology that is compatible with the large irradiation induced changes is essential to enable these applications. Modeling activities for the macroscopic mechanical response are expected to play key roles in design methodology development. Macroscopic models of plasticity (a constitutive equation) and cyclic softening behavior after irradiation are discussed. Significance of models to estimate microstructural changes during irradiation and beneficial effects of the heat treatment for irradiation performance are also introduced.
Tanigawa, Hiroyasu; Sokolov, M. A.*; Sawahata, Atsushi*; Hashimoto, Naoyuki*; Ando, Masami; Shiba, Kiyoyuki; Enomoto, Masato*; Klueh, R. L.*
Journal of ASTM International (Internet), 6(5), 10 Pages, 2009/05
The master curve (MC) method works when the transition fracture toughness values follow the MC, and once the value is scaled properly, the MC is usually independent of the type of steel or the type of test specimen. This method is very much depending on the assumption that the fracture initiation points are homogeneously distributed and its initiation mechanism is independent on test temperature. The reduced-activation ferritic/martensitic steels (RAFs), such as F82H (Fe-8Cr-2W-0.2V-0.04Ta), has AlO Ta(V,Ti)O composite inclusions, or simple Ta(V)O inclusions, and shows inhomogeneous distribution, and it was revealed that that RAFs which contain Ta could initiate the facture in the different mechanism at lower temperature as the composite inclusions become fragile, and this should be considered when the toughness measured with small size toughness specimen which is usually tested at lower temperature.
Tanigawa, Hiroyasu; Hirose, Takanori; Shiba, Kiyoyuki; Kasada, Ryuta*; Wakai, Eiichi; Serizawa, Hisashi*; Kawahito, Yosuke*; Jitsukawa, Shiro; Kimura, Akihiko*; Kono, Yutaka*; et al.
Fusion Engineering and Design, 83(10-12), p.1471 - 1476, 2008/12
Reduced activation ferritic/martensitic steels (RAFMs) are recognized as the primary candidate structural materials for fusion blanket systems. F82H, which were developed and studied in Japan, was designed with an emphasis on high temperature properties and weldability. The database on F82H properties is currently the most extensive available among the existing RAFMs. The objective of this paper is to review the R&D status of F82H and to identify the key technical issues for the fabrication of an ITER Test Blanket Module (TBM) suggested by recent achievements in Japan.
Hirose, Takanori; Shiba, Kiyoyuki; Enoeda, Mikio; Akiba, Masato
Journal of Nuclear Materials, 367-370(2), p.1185 - 1189, 2007/08
A reduced activation ferritic/martensitic steel, F82H has been tested through slow strain rate tests with strain rates of 310 s in Super Critical Pressurized Water (SCPW) environment. The water was pressurized up to 23.5 MPa and the range of its temperature was from 280 C to 550 C. The stress drop and the loss of ductility, both due to the stress corrosion cracking, have not been observed in all the specimens. Also the fracture surface showed no brittle fracture. The weight change during the SSRT depends strongly on the test temperature, but dissolved oxygen content does not have significant effects. The time dependence of weight change has been described through the plot of some parabolic curves.
Nakamura, Hiroo; Ida, Mizuho; Chida, Teruo; Shiba, Kiyoyuki; Shimizu, Katsusuke*; Sugimoto, Masayoshi
Journal of Nuclear Materials, 367-370(2), p.1543 - 1548, 2007/08
The IFMIF is an accelerator-based intense neutron source for testing candidate materials of fusion reactor. Intense neutrons are emitted inside the Li flow through a backwall. The backwall made of 316L stainless steel or RAFM is attached to the target assembly with a lip seal welded by YAG laser. Since the backwall is operating under a severe neutron irradiation of 50 dpa/year and a maximum nuclear heating rate of 25 W/cm, thermo-structural design is one of critical issues in a target design. Thermal stress was calculated by ABAQUS code. As a permissible stress, yield strength at 300C was used. In a case of the 316 stainless steel backwall, a maximum thermal stress was more than the permissible stress(164MPa). On the other hand, in case of the F82H backwall, a maximum thermal stress is was below the permissible stress(455MPa). Therefore, F82H is recommended as a backwall material.
Ando, Masami; Li, M.*; Tanigawa, Hiroyasu; Grossbeck, M. L.*; Kim, S.-W.; Sawai, Tomotsugu; Shiba, Kiyoyuki; Kono, Yutaka*; Koyama, Akira*
Journal of Nuclear Materials, 367-370(1), p.122 - 126, 2007/08
Irradiation creep behavior of the F82H and several JLF-1 steels have been measured up to 5 dpa, using helium-pressurized creep tubes irradiated in HFIR. These tubes were pressurized with helium to hoop stress levels of 0 to 400 MPa for irradiation temperature. The results of F82H and JLF-1 with 200 MPa hoop stress showed small creep strains ( 0.15%) after irradiation. Irradiation creep rate in these steels is linearly dependent on the applied stress less than 200 MPa. However, at higher hoop stress level, the creep rate of them is nonlinear. The creep compliance coefficient for F82H and JLF-1 at 300 C is very small values. These data contribute to a part of materials database for ITER Test blanket design work.
Ando, Masami; Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Jitsukawa, Shiro; Kono, Yutaka*; Koyama, Akira*; Li, M.*; Stoller, R. E.*
Nippon Kinzoku Gakkai-Shi, 71(7), p.559 - 562, 2007/07
no abstracts in English
Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Hirose, Takanori; Kasada, Ryuta*; Wakai, Eiichi; Jitsukawa, Shiro; Kimura, Akihiko*; Koyama, Akira*
Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 6 Pages, 2007/03
The status of research and development of reduced activation martensitic steels (RAMs) in Japan are reviewed and key issues suggested from recent achievements in Japan since the last conference are highlighted, with the aim of the fabrication for the ITER Test Blanket Module (TBM) and application for the DEMO reactor. It was pointed out that international collaboration would be desirable for research on key issues such as precipitate stability under irradiation or Ta effects which are common for all RAMs and require an extensive research effort.
Sawahata, Atsushi; Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Enomoto, Masato*
Nippon Kinzoku Gakkai-Shi, 71(2), p.244 - 248, 2007/02
Reduced activation ferritic/martensitic steels (RAFs), such as F82H (Fe-8Cr-2W-0.2V-0.04Ta-0.1C), are one of the leading candidates for structural materials of fusion reactors, and it is essential for RAFs R&D to assure its good toughness property for fusion application. In this study, the influence of Ti on impact property was studied based on microstructural analyses and charpy impact tests which were performed against general-purity F82H (0.004Ti-0.0060N) and high-purity F82H (0.001Ti- 0.0014N). In general-purity F82H, its impact property around DBTT showed both 100% brittle fracture and brittle-ductile, and this tendency is not appeared in high-purity F82H. SEM observation on those brittle fracture surfaces of general-purity F82H revealed the presence of AlO-Ta(V,Ti)O complex oxides at the fracture initiation point. The size distribution analyses of oxides suggest that the complex oxide in general-purity F82H showed a higher number density than in high-purity F82H. In addition to this, EDS analyses showed the complex oxides in general-purity F82H had a strong peak of Ti, but they were not detected in the oxide in high-purity F82H. These results suggest the influence of Ti on complex oxide formation which affects impact property.
Nakata, Toshiya; Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Komazaki, Shinichi*; Fujiwara, Mikio*; Kono, Yutaka*; Koyama, Akira*
Nippon Kinzoku Gakkai-Shi, 71(2), p.239 - 243, 2007/02
no abstracts in English
Nakata, Toshiya; Komazaki, Shinichi*; Nakajima, Motoki*; Kono, Yutaka*; Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Koyama, Akira*
Nippon Kinzoku Gakkai-Shi, 70(8), p.642 - 645, 2006/08
no abstracts in English
Wakai, Eiichi; Jitsukawa, Shiro; Tomita, Hideki*; Furuya, Kazuyuki; Sato, Michitaka*; Oka, Keiichiro*; Tanaka, Teruyuki*; Takada, Fumiki; Yamamoto, Toshio*; Kato, Yoshiaki; et al.
Journal of Nuclear Materials, 343(1-3), p.285 - 296, 2005/08
The dependence of helium production on radiation-hardening and -embrittlement has been examined in a reduced-activation martensitic F82H steel doped with B, B and B+B irradiated at 250C to 2.2 dpa. The total amounts of doping boron were about 60 massppm. The range of He concentration produced in the specimens was from about 5 to about 300 appm. Tensile and fracture toughness tests were performed after neutron irradiation. 50 MeV-He irradiation was also performed to implant about 85 appm He atoms at 120C by AVF cyclotron to 0.03 dpa, and small punch testing was performed to obtain DBTT. Radiation-hardening of the neutron-irradiated specimens increased slightly with increasing He production. The 100 MPam DBTT for the F82H+B, F82H+B+B, and F82H+B were 40, 110, and 155C, respectively. The shifts of DBTT due to He production were evaluated as about 70C by 150 appmHe and 115C by 300 appmHe. The DBTT shift in the small punch testing was evaluated as 50C.
Wakai, Eiichi; Sato, Michitaka*; Okubo, Nariaki; Sawai, Tomotsugu; Shiba, Kiyoyuki; Jitsukawa, Shiro
Nippon Kinzoku Gakkai-Shi, 69(6), p.460 - 464, 2005/06
no abstracts in English
Taguchi, Tomitsugu; Jitsukawa, Shiro; Sato, Michitaka*; Matsukawa, Shingo*; Wakai, Eiichi; Shiba, Kiyoyuki
Journal of Nuclear Materials, 335(3), p.457 - 461, 2004/12
F82H (Fe-8Cr-2W) and its variant doped with 2%Ni were irradiated up to 20 dpa at 300C in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. Post irradiation tensile testing was performed at room temperature. During testing, the images of the specimens including the necked region were continuously recorded. Tests on cold worked material were also carried out for comparison. From the load-displacement curves and the strain distributions obtained from the images, flow stress levels and strain hardening behavior was evaluated. A preliminary constitutive equation for the plastic deformation of irradiated F82H is presented. The results suggest that the irradiation mainly causes defect-induced hardening while it did not strongly affect strain hardening at the same flow stress level for F82H irradiated at 300C. The strain hardening of Ni doped specimens was, however, strongly affected by irradiation. Results provide basics to determine allowable stress levels at temperatures below 400C.
Hirose, Takanori; Shiba, Kiyoyuki; Sawai, Tomotsugu; Jitsukawa, Shiro; Akiba, Masato
Journal of Nuclear Materials, 329-333(Part1), p.324 - 327, 2004/08
Reduced activation ferritic/martensitic steel, RAFs is the leading candidates for the structural materials of breeding blankets. HIP is examined as a near-net-shape fabrication process for this structure. The HIP requires heating above the normalizing temperature and the final microstructural features depends on the HIP processing conditions. Conventional HIP process caused a prior-austenite grain (PAG) coarsening of RAFs and subsequent increase of ductile brittle transition temperature. Japanese RAFs F82H and its modified steels were investigated by metallurgical method after isochronal heat treatment up to 1473K simulating HIP equivalent thermal hysteresis. Although Conventional F82H IEA heat showed significant grain growth after conventional solid HIP conditions (1313K 2hr.), F82H with 0.1wt.% tantalum kept fine grain after the same heat treatment. On the other hands, conventional RAF/Ms with coarse grain were recovered by the post HIP normalizing at temperature below TaC dissolution temperature. This process can refine the PAG size of F82H more than ASTM grain size number 7.