Kasada Ryuta | Kyoto University (original) (raw)

Papers by Kasada Ryuta

Materials Science Forum, 2010

Journal of Nuclear Materials, 2009

Breeding blankets are the most important components in DEMO. The DEMO blanket has to withstand hi... more Breeding blankets are the most important components in DEMO. The DEMO blanket has to withstand high neutron flux typically 15-30 dpa/year under continuous operation. Therefore integrated and effective development of blanket structural materials and breeding/multiplying materials is essential in the blanket development for DEMO. In parallel to the ITER program, broader approach (BA) activities are initiated by EU and Japan. Based on the common interest of each party towards DEMO, R&D on reduced activation ferritic martensitic (RAFM) steels as a DEMO blanket structural material, SiC f /SiC composites which have potential for use in DEMO blankets, advanced tritium breeders and neutron multiplier for DEMO blankets, and tritium technologies including tritium behavior studies in advanced materials for DEMO blanket applications will be carried out as a part of the BA activities.

Materials Science Forum, 2010

ABSTRACT A novel GBD treatment with Dy-Ni-Al eutectic alloy powder enhanced the coercivity of the... more ABSTRACT A novel GBD treatment with Dy-Ni-Al eutectic alloy powder enhanced the coercivity of the sintered Nd-Fe-B magnet plate as thick as 5mm to 1760 kA/m (22 kOe) without reducing the remanence. The results of wavelength dispersive X-ray spectroscopy (WDS) indicated that this industrially epoch-making treatment spread Dy, which is a coercivity enhancing element, from the surface to the centre of the magnet through Nd-rich phase. Microstructural observations suggested that Ni and Al, which are the melting point depressants of Nd and Dy, enabled the high diffusivity of Dy.

Journal of Magnetism and Magnetic Materials, 2011

A novel grain boundary diffusion (GBD) treatment with a Dy-Ni-Al eutectic alloy powder allowed Dy... more A novel grain boundary diffusion (GBD) treatment with a Dy-Ni-Al eutectic alloy powder allowed Dy to penetrate into sintered plates of Nd-Fe-B magnet as thick as 5 mm. The coercivity of the magnet was increased from a value of 1160 kA/m (14.5 kOe) to 1760 kA/m (22 kOe). This was achieved without any marked decrease in remanance and with a high squareness.

Journal of Nuclear Materials, 2011

The effects of alloying elements on irradiation hardening behavior of various Fe-based binary all... more The effects of alloying elements on irradiation hardening behavior of various Fe-based binary alloys irradiated with Fe 3+ ions were investigated by using the nano-indentation technique. Ion-irradiations with 6.4 MeV Fe 3+ were performed on Pure-Fe, Fe-1Cr, Fe-1Mn, Fe-1.5Mn, Fe-1Ni, Fe-1Cu, and Fe-1Mo to nominal displacement damage levels of 0.1, 0.3 and 1 dpa, at a damage rate of 1 Â 10 À4 dpa/s at 290°C. Significant irradiation hardening was observed in the Fe-1Mn, Fe-1.5Mn and Fe-1Ni as well as in the Fe-1Cu, but not in the Pure-Fe, Fe-1Cr and Fe-1Mo, after irradiation to 1 dpa at 290°C. The dose dependence of the irradiation hardening was well explained for all the alloys by the saturation fitting model. Microstructural observation suggested that irradiation induced matrix defects in Fe-Mn binary alloy promoted the irradiation hardening.

Materials Science Forum, 2010

ABSTRACT

Journal of Nuclear Materials

ABSTRACT 6.4MeV Fe3+ ion irradiation was applied to a ε-Zr-hydride to clarify the relation betwee... more ABSTRACT 6.4MeV Fe3+ ion irradiation was applied to a ε-Zr-hydride to clarify the relation between the hardening and the microstructure change of bulk Zr-hydrides under neutron irradiation. Irradiation hardening was measured by nano-indentation test. TEM cross-sectional observation results showed that the dominant deformation mechanism of ε-Zr-hydride was the formation of the new fine twin bands and tangled dislocations and black dot-like defects were observed in the irradiated hydride matrix. Ultra low voltage SEM (ULV-SEM) observation showed that cracks were induced obviously in the indents print after the irradiation. The irradiation-induced defects made the deformation of ε-Zr-hydride difficult.

Journal of Nuclear Materials, 2011

The effects of dissolved oxygen (DO:8 ppm) and hydrogen (DH:0.4 ppm and 1.4 ppm) on stress corros... more The effects of dissolved oxygen (DO:8 ppm) and hydrogen (DH:0.4 ppm and 1.4 ppm) on stress corrosion cracking (scc) of SUS316L were tested by slow strain rate test (SSRT) and crevice bent beam test (CBB) in high-temperature (288°C) pressurized (7.8 MPa) water environment. Sensitized and non-sensitized SUS316L were cold-worked up to the rolling ratio of four patterns (0, 25, 50, and 75%). The SSRT tensile elongation of non-sensitized SUS316L was significantly reduced in hydrogen dissolved water environment, indicating hydrogen enhanced SCC. The fractured surface was mainly TGSCC, and the TGSCC increased with increasing dissolved hydrogen in the water. Also the TGSCC in the fractured surface was reduced by cold-work because of the shortage of test period for the cold-worked specimens broken in a small elongation in a ductile manner. The CBB test results indicate that susceptibility of TGSCC was increased by cold work.

Fusion Engineering and Design, 2008

Reduced activation ferritic/martensitic steels (RAFMs) are recognized as the primary candidate st... more Reduced activation ferritic/martensitic steels (RAFMs) are recognized as the primary candidate structural materials for fusion blanket systems. The RAFM F82H was developed in Japan with emphasis on hightemperature properties and weldability. Extensive irradiation studies have conducted on F82H, and it has the most extensive available database of irradiated and unirradiated properties of all 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 from the recent research achievements in Japan. This work clarified that the primary issues with F82H involve welding techniques and the mechanical properties of weld joints. This is the result of the distinctive nature of the joint caused by the phase transformation that occurs in the weld joint during cooling, and its impact on the design of a TBM will be discussed.

Materials Science Forum, 2010

ABSTRACT The effects of small amount (1 or 2 wt.%) of Ni additionson the irradiation hardening of... more ABSTRACT The effects of small amount (1 or 2 wt.%) of Ni additionson the irradiation hardening of the reduced-activation ferritic/martensitic steel, F82H, used as fusion reactor blanket structural materials were investigated by means of Fe-ion irradiation experimental test method and nano-indentation technique. The ion-irradiation hardening of Ni-added F82H is larger than that of the steel without Ni addition. The methodology to derive the irradiation hardening of ion-irradiated F82H steel was proposed from the results of hardness depth profile.

Materials Science Forum, 2010

Journal of Nuclear Materials, 2009

Breeding blankets are the most important components in DEMO. The DEMO blanket has to withstand hi... more Breeding blankets are the most important components in DEMO. The DEMO blanket has to withstand high neutron flux typically 15-30 dpa/year under continuous operation. Therefore integrated and effective development of blanket structural materials and breeding/multiplying materials is essential in the blanket development for DEMO. In parallel to the ITER program, broader approach (BA) activities are initiated by EU and Japan. Based on the common interest of each party towards DEMO, R&D on reduced activation ferritic martensitic (RAFM) steels as a DEMO blanket structural material, SiC f /SiC composites which have potential for use in DEMO blankets, advanced tritium breeders and neutron multiplier for DEMO blankets, and tritium technologies including tritium behavior studies in advanced materials for DEMO blanket applications will be carried out as a part of the BA activities.

Materials Science Forum, 2010

ABSTRACT A novel GBD treatment with Dy-Ni-Al eutectic alloy powder enhanced the coercivity of the... more ABSTRACT A novel GBD treatment with Dy-Ni-Al eutectic alloy powder enhanced the coercivity of the sintered Nd-Fe-B magnet plate as thick as 5mm to 1760 kA/m (22 kOe) without reducing the remanence. The results of wavelength dispersive X-ray spectroscopy (WDS) indicated that this industrially epoch-making treatment spread Dy, which is a coercivity enhancing element, from the surface to the centre of the magnet through Nd-rich phase. Microstructural observations suggested that Ni and Al, which are the melting point depressants of Nd and Dy, enabled the high diffusivity of Dy.

Journal of Magnetism and Magnetic Materials, 2011

A novel grain boundary diffusion (GBD) treatment with a Dy-Ni-Al eutectic alloy powder allowed Dy... more A novel grain boundary diffusion (GBD) treatment with a Dy-Ni-Al eutectic alloy powder allowed Dy to penetrate into sintered plates of Nd-Fe-B magnet as thick as 5 mm. The coercivity of the magnet was increased from a value of 1160 kA/m (14.5 kOe) to 1760 kA/m (22 kOe). This was achieved without any marked decrease in remanance and with a high squareness.

Journal of Nuclear Materials, 2011

The effects of alloying elements on irradiation hardening behavior of various Fe-based binary all... more The effects of alloying elements on irradiation hardening behavior of various Fe-based binary alloys irradiated with Fe 3+ ions were investigated by using the nano-indentation technique. Ion-irradiations with 6.4 MeV Fe 3+ were performed on Pure-Fe, Fe-1Cr, Fe-1Mn, Fe-1.5Mn, Fe-1Ni, Fe-1Cu, and Fe-1Mo to nominal displacement damage levels of 0.1, 0.3 and 1 dpa, at a damage rate of 1 Â 10 À4 dpa/s at 290°C. Significant irradiation hardening was observed in the Fe-1Mn, Fe-1.5Mn and Fe-1Ni as well as in the Fe-1Cu, but not in the Pure-Fe, Fe-1Cr and Fe-1Mo, after irradiation to 1 dpa at 290°C. The dose dependence of the irradiation hardening was well explained for all the alloys by the saturation fitting model. Microstructural observation suggested that irradiation induced matrix defects in Fe-Mn binary alloy promoted the irradiation hardening.

Materials Science Forum, 2010

ABSTRACT

Journal of Nuclear Materials

ABSTRACT 6.4MeV Fe3+ ion irradiation was applied to a ε-Zr-hydride to clarify the relation betwee... more ABSTRACT 6.4MeV Fe3+ ion irradiation was applied to a ε-Zr-hydride to clarify the relation between the hardening and the microstructure change of bulk Zr-hydrides under neutron irradiation. Irradiation hardening was measured by nano-indentation test. TEM cross-sectional observation results showed that the dominant deformation mechanism of ε-Zr-hydride was the formation of the new fine twin bands and tangled dislocations and black dot-like defects were observed in the irradiated hydride matrix. Ultra low voltage SEM (ULV-SEM) observation showed that cracks were induced obviously in the indents print after the irradiation. The irradiation-induced defects made the deformation of ε-Zr-hydride difficult.

Journal of Nuclear Materials, 2011

The effects of dissolved oxygen (DO:8 ppm) and hydrogen (DH:0.4 ppm and 1.4 ppm) on stress corros... more The effects of dissolved oxygen (DO:8 ppm) and hydrogen (DH:0.4 ppm and 1.4 ppm) on stress corrosion cracking (scc) of SUS316L were tested by slow strain rate test (SSRT) and crevice bent beam test (CBB) in high-temperature (288°C) pressurized (7.8 MPa) water environment. Sensitized and non-sensitized SUS316L were cold-worked up to the rolling ratio of four patterns (0, 25, 50, and 75%). The SSRT tensile elongation of non-sensitized SUS316L was significantly reduced in hydrogen dissolved water environment, indicating hydrogen enhanced SCC. The fractured surface was mainly TGSCC, and the TGSCC increased with increasing dissolved hydrogen in the water. Also the TGSCC in the fractured surface was reduced by cold-work because of the shortage of test period for the cold-worked specimens broken in a small elongation in a ductile manner. The CBB test results indicate that susceptibility of TGSCC was increased by cold work.

Fusion Engineering and Design, 2008

Reduced activation ferritic/martensitic steels (RAFMs) are recognized as the primary candidate st... more Reduced activation ferritic/martensitic steels (RAFMs) are recognized as the primary candidate structural materials for fusion blanket systems. The RAFM F82H was developed in Japan with emphasis on hightemperature properties and weldability. Extensive irradiation studies have conducted on F82H, and it has the most extensive available database of irradiated and unirradiated properties of all 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 from the recent research achievements in Japan. This work clarified that the primary issues with F82H involve welding techniques and the mechanical properties of weld joints. This is the result of the distinctive nature of the joint caused by the phase transformation that occurs in the weld joint during cooling, and its impact on the design of a TBM will be discussed.

Materials Science Forum, 2010

ABSTRACT The effects of small amount (1 or 2 wt.%) of Ni additionson the irradiation hardening of... more ABSTRACT The effects of small amount (1 or 2 wt.%) of Ni additionson the irradiation hardening of the reduced-activation ferritic/martensitic steel, F82H, used as fusion reactor blanket structural materials were investigated by means of Fe-ion irradiation experimental test method and nano-indentation technique. The ion-irradiation hardening of Ni-added F82H is larger than that of the steel without Ni addition. The methodology to derive the irradiation hardening of ion-irradiated F82H steel was proposed from the results of hardness depth profile.