E. Wakai - Academia.edu (original) (raw)
Papers by E. Wakai
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
ABSTRACT
Modelling and Simulation in Materials Science and Engineering, 2008
A new meso-scale three-dimensional computer model has been proposed to enhance the modeling capab... more A new meso-scale three-dimensional computer model has been proposed to enhance the modeling capability of the bubble growth in metals, particularly the helium bubble growth under the condition of post-irradiation annealing. We assume that the bubble growth be modeled by a process driven by energy minimization of the surface energy and thermal fluctuation with a framework of a Monte-Carlo simulation method. We found that it is possible to simulate growing bubbles following the ideal gas law and in equilibrium with the surface tension. The simulation results show a good agreement with some experimental evidences, in particular, of the log-normal bubble-size distribution. The extension of the model to the bubble growth on grain boundaries with reference to the helium-embrittlement has succeeded in reproducing a particular bubble shape observed in experiments.
Journal of Nuclear Materials, 2000
Journal of Nuclear Materials, 2002
ABSTRACT The synergistic effects of displacement damage and atomic hydrogen and helium on swellin... more ABSTRACT The synergistic effects of displacement damage and atomic hydrogen and helium on swelling of the ferritic/martensitic steel, F82H, has been investigated. The irradiation was performed at temperatures between 470 and 600 °C to 50 dpa (displacement per atoms) under conditions of simultaneous ion beams consisting of Fe3+, He+ and H+ ions or Fe3+ and He+ ions. The swelling of F82H steel under triple beams with 18 appm He/dpa and 70 appm H/dpa was larger than that under dual beams with 18 appm He/dpa. The swelling in F82H under triple beams increased with decreasing irradiation temperature from 0.1% to 3.2%, while swelling under dual beams was between 0.04% and 0.08%. On the other hand, in the case of triple beam irradiation with a high ratio of gas/dpa, the swelling tended to increase with irradiation temperature. The swelling in ferritic/martensitic steels is significantly enhanced by the synergistic effect of displacement damage, hydrogen and helium atoms.
Journal of Nuclear Materials, 2004
For basic understanding of how to produce a homogeneous distribution of nano-scale oxide particle... more For basic understanding of how to produce a homogeneous distribution of nano-scale oxide particles, we have applied dual ion-implantation to make a super-saturation of oxide-forming elements. Y+ and O+ ions were implanted into ferritic alloys at room temperature. Both in situ annealing in an electron microscope for thin samples and conventional annealing for bulk samples were carried out at 300–1300
Journal of Nuclear Materials, 2002
ABSTRACT Metallurgical examinations and hardness measurements were performed at hot isostatic pre... more ABSTRACT Metallurgical examinations and hardness measurements were performed at hot isostatic pressing (HIP)-bonded regions in blanket structures made from F82H alloy in order to investigate the HIP-bondability and the influence on the microstructure due to the HIP and heat treatments which would correspond to the fabrication of an actual blanket. The metallurgical examination showed that the HIP-bonded interfaces were sufficiently diffusion-bonded without significant defects, i.e. voids and/or exfoliations, although grain coarsening was observed at a part of the HIP interfaces. Hardness was nearly equal in the coarsening region and a region without coarsening, but about a 10 Hv increase was found in a boundary in between the regions with and without coarsening. Microcrystallized grains were observed in a region about ∼6 μm from HIP interfaces, and the hardness increased by about 0.2 GPa in the region.
Journal of Nuclear Materials, 2003
Corrosion tests of austenitic stainless tube were done under flowing Pb-Bi conditions for 3000 h ... more Corrosion tests of austenitic stainless tube were done under flowing Pb-Bi conditions for 3000 h at 450°C. Specimens were 316SS produced as a tubing form with 13.8 mm outer diameter, 2 mm thickness and 40 cm length. During operation, maximum temperature, temperature difference and flow velocity of Pb-Bi at the specimen were kept at 450, 50°C, and 1 m/s, respectively. After the test, specimen and components of the loop were cut and examined by optical microscope, SEM, EDX, WDX and X-ray diffraction. Pb-Bi adhered on the surface of the specimen even after Pb-Bi was drained out to the storage tank from the circulating loop. Results differed from a stagnant corrosion test in that the specimen surface became rough and the corrosion rate was maximally 0.1 mm/3000 h. Mass transfer from the high temperature to the lower temperature area was observed: crystals of Fe-Cr were found on the tube surface in the lowtemperature region. The sizes of crystals varied from 0.1 to 0.2 mm. The depositing crystals were ferrite grains and the chemical composition ratio (mass%) of Fe to Cr was 9:1.
Journal of Nuclear Materials, 2004
ABSTRACT
Fusion Engineering and Design, 2008
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
ABSTRACT
Modelling and Simulation in Materials Science and Engineering, 2008
A new meso-scale three-dimensional computer model has been proposed to enhance the modeling capab... more A new meso-scale three-dimensional computer model has been proposed to enhance the modeling capability of the bubble growth in metals, particularly the helium bubble growth under the condition of post-irradiation annealing. We assume that the bubble growth be modeled by a process driven by energy minimization of the surface energy and thermal fluctuation with a framework of a Monte-Carlo simulation method. We found that it is possible to simulate growing bubbles following the ideal gas law and in equilibrium with the surface tension. The simulation results show a good agreement with some experimental evidences, in particular, of the log-normal bubble-size distribution. The extension of the model to the bubble growth on grain boundaries with reference to the helium-embrittlement has succeeded in reproducing a particular bubble shape observed in experiments.
Journal of Nuclear Materials, 2000
Journal of Nuclear Materials, 2002
ABSTRACT The synergistic effects of displacement damage and atomic hydrogen and helium on swellin... more ABSTRACT The synergistic effects of displacement damage and atomic hydrogen and helium on swelling of the ferritic/martensitic steel, F82H, has been investigated. The irradiation was performed at temperatures between 470 and 600 °C to 50 dpa (displacement per atoms) under conditions of simultaneous ion beams consisting of Fe3+, He+ and H+ ions or Fe3+ and He+ ions. The swelling of F82H steel under triple beams with 18 appm He/dpa and 70 appm H/dpa was larger than that under dual beams with 18 appm He/dpa. The swelling in F82H under triple beams increased with decreasing irradiation temperature from 0.1% to 3.2%, while swelling under dual beams was between 0.04% and 0.08%. On the other hand, in the case of triple beam irradiation with a high ratio of gas/dpa, the swelling tended to increase with irradiation temperature. The swelling in ferritic/martensitic steels is significantly enhanced by the synergistic effect of displacement damage, hydrogen and helium atoms.
Journal of Nuclear Materials, 2004
For basic understanding of how to produce a homogeneous distribution of nano-scale oxide particle... more For basic understanding of how to produce a homogeneous distribution of nano-scale oxide particles, we have applied dual ion-implantation to make a super-saturation of oxide-forming elements. Y+ and O+ ions were implanted into ferritic alloys at room temperature. Both in situ annealing in an electron microscope for thin samples and conventional annealing for bulk samples were carried out at 300–1300
Journal of Nuclear Materials, 2002
ABSTRACT Metallurgical examinations and hardness measurements were performed at hot isostatic pre... more ABSTRACT Metallurgical examinations and hardness measurements were performed at hot isostatic pressing (HIP)-bonded regions in blanket structures made from F82H alloy in order to investigate the HIP-bondability and the influence on the microstructure due to the HIP and heat treatments which would correspond to the fabrication of an actual blanket. The metallurgical examination showed that the HIP-bonded interfaces were sufficiently diffusion-bonded without significant defects, i.e. voids and/or exfoliations, although grain coarsening was observed at a part of the HIP interfaces. Hardness was nearly equal in the coarsening region and a region without coarsening, but about a 10 Hv increase was found in a boundary in between the regions with and without coarsening. Microcrystallized grains were observed in a region about ∼6 μm from HIP interfaces, and the hardness increased by about 0.2 GPa in the region.
Journal of Nuclear Materials, 2003
Corrosion tests of austenitic stainless tube were done under flowing Pb-Bi conditions for 3000 h ... more Corrosion tests of austenitic stainless tube were done under flowing Pb-Bi conditions for 3000 h at 450°C. Specimens were 316SS produced as a tubing form with 13.8 mm outer diameter, 2 mm thickness and 40 cm length. During operation, maximum temperature, temperature difference and flow velocity of Pb-Bi at the specimen were kept at 450, 50°C, and 1 m/s, respectively. After the test, specimen and components of the loop were cut and examined by optical microscope, SEM, EDX, WDX and X-ray diffraction. Pb-Bi adhered on the surface of the specimen even after Pb-Bi was drained out to the storage tank from the circulating loop. Results differed from a stagnant corrosion test in that the specimen surface became rough and the corrosion rate was maximally 0.1 mm/3000 h. Mass transfer from the high temperature to the lower temperature area was observed: crystals of Fe-Cr were found on the tube surface in the lowtemperature region. The sizes of crystals varied from 0.1 to 0.2 mm. The depositing crystals were ferrite grains and the chemical composition ratio (mass%) of Fe to Cr was 9:1.
Journal of Nuclear Materials, 2004
ABSTRACT
Fusion Engineering and Design, 2008