Refine your search:     
Report No.
Search Results: Records 1-20 displayed on this page of 118

Presentation/Publication Type

Initialising ...


Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...


Initialising ...


Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

The Hydrogen-bond network in sodium chloride tridecahydrate; Analogy with ice VI

Yamashita, Keishiro*; Nakayama, Kazuya*; Komatsu, Kazuki*; Ohara, Takashi; Munakata, Koji*; Hattori, Takanori; Sano, Asami; Kagi, Hiroyuki*

Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 79(5), p.414 - 426, 2023/10

The structure of a recently-found hyperhydrated form of sodium chloride, NaCl$$cdot$$ 13H(D)$$_{2}$$O, has been determined by ${it in situ}$ single-crystal neutron diffraction at 1.7 GPa and 298 K. It has large hydrogen-bond networks and some water molecules have distorted bonding features such as bifurcated hydrogen bonds and five-coordinated water molecules. The hydrogen-bond network has similarities to ice VI in terms of network topology and disordered hydrogen bonds. Assuming the equivalence of network components connected by pseudo symmetries, the overall network structure of this hydrate can be expressed by breaking it down into smaller structural units which correspond to the ice VI network structure. This hydrogen-bond network contains orientational disorder of water molecules in contrast to the known salt hydrates. Here, we present an example for further insights into a hydrogen-bond network containing ionic species.

Journal Articles

Improvement of nano-polycrystalline diamond anvil cells with Zr-based bulk metallic glass cylinder for higher pressures; Application to Laue-TOF diffractometer

Yamashita, Keishiro*; Komatsu, Kazuki*; Ohara, Takashi; Munakata, Koji*; Irifune, Tetsuo*; Shimmei, Toru*; Sugiyama, Kazumasa*; Kawamata, Toru*; Kagi, Hiroyuki*

High Pressure Research, 42(1), p.121 - 135, 2022/03

 Times Cited Count:1 Percentile:61.09(Physics, Multidisciplinary)

Journal Articles

Deep learning approach for an interface structure analysis with a large statistical noise in neutron reflectometry

Aoki, Hiroyuki; Liu, Y.*; Yamashita, Takashi*

Scientific Reports (Internet), 11(1), p.22711_1 - 22711_9, 2021/11

 Times Cited Count:5 Percentile:58.53(Multidisciplinary Sciences)

Journal Articles

Summary results of subsidy program for the "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy and Thermal Behavior Estimation of Fuel Debris))"

Koyama, Shinichi; Nakagiri, Toshio; Osaka, Masahiko; Yoshida, Hiroyuki; Kurata, Masaki; Ikeuchi, Hirotomo; Maeda, Koji; Sasaki, Shinji; Onishi, Takashi; Takano, Masahide; et al.

Hairo, Osensui Taisaku jigyo jimukyoku Homu Peji (Internet), 144 Pages, 2021/08

JAEA performed the subsidy program for the "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy and Thermal Behavior Estimation of Fuel Debris))" in 2020JFY. This presentation summarized briefly the results of the project, which will be available shortly on the website of Management Office for the Project of Decommissioning and Contaminated Water Management.

Journal Articles

Effect of solute carbon on the characteristic hardening of steel at high temperature

Koga, Norimitsu*; Umezawa, Osamu*; Yamamoto, Masayuki*; Yamamoto, Takashi*; Yamashita, Takayuki; Morooka, Satoshi; Kawasaki, Takuro; Harjo, S.

Metallurgical and Materials Transactions A, 52(3), p.897 - 901, 2021/03

 Times Cited Count:3 Percentile:26.82(Materials Science, Multidisciplinary)

Journal Articles

GPU acceleration of multigrid preconditioned conjugate gradient solver on block-structured Cartesian grid

Onodera, Naoyuki; Idomura, Yasuhiro; Hasegawa, Yuta; Yamashita, Susumu; Shimokawabe, Takashi*; Aoki, Takayuki*

Proceedings of International Conference on High Performance Computing in Asia-Pacific Region (HPC Asia 2021) (Internet), p.120 - 128, 2021/01

 Times Cited Count:0 Percentile:0.01

We develop a multigrid preconditioned conjugate gradient (MG-CG) solver for the pressure Poisson equation in a two-phase flow CFD code JUPITER. The MG preconditioner is constructed based on the geometric MG method with a three-stage V-cycle, and a RB-SOR smoother and its variant with cache-reuse optimization (CR-SOR) are applied at each stage. The numerical experiments are conducted for two-phase flows in a fuel bundle of a nuclear reactor. The MG-CG solvers with the RB-SOR and CR-SOR smoothers reduce the number of iterations to less than 15% and 9% of the original preconditioned CG method, leading to 3.1- and 5.9-times speedups, respectively. The obtained performance indicates that the MG-CG solver designed for the block-structured grid is highly efficient and enables large-scale simulations of two-phase flows on GPU based supercomputers.

Journal Articles

GPU-acceleration of locally mesh allocated two phase flow solver for nuclear reactors

Onodera, Naoyuki; Idomura, Yasuhiro; Ali, Y.*; Yamashita, Susumu; Shimokawabe, Takashi*; Aoki, Takayuki*

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.210 - 215, 2020/10

This paper presents a GPU-based Poisson solver on a block-based adaptive mesh refinement (block-AMR) framework. The block-AMR method is essential for GPU computation and efficient description of the nuclear reactor. In this paper, we successfully implement a conjugate gradient method with a state-of-the-art multi-grid preconditioner (MG-CG) on the block-AMR framework. GPU kernel performance was measured on the GPU-based supercomputer TSUBAME3.0. The bandwidth of a vector-vector sum, a matrix-vector product, and a dot product in the CG kernel gave good performance at about 60% of the peak performance. In the MG kernel, the smoothers in a three-stage V-cycle MG method are implemented using a mixed precision RB-SOR method, which also gave good performance. For a large-scale Poisson problem with $$453.0 times 10^6$$ cells, the developed MG-CG method reduced the number of iterations to less than 30% and achieved $$times$$ 2.5 speedup compared with the original preconditioned CG method.

Journal Articles

Microstructure and texture evolution and ring-tensile properties of recrystallized FeCrAl ODS cladding tubes

Aghamiri, S. M. S.*; Sowa, Takashi*; Ukai, Shigeharu*; Ono, Naoko*; Sakamoto, Kan*; Yamashita, Shinichiro

Materials Science & Engineering A, 771, p.138636_1 - 138636_12, 2020/01

 Times Cited Count:25 Percentile:90.87(Nanoscience & Nanotechnology)

Oxide dispersion strengthened (ODS) FeCrAl ferritic steels are being developed as potential accident tolerance fuel cladding materials for the light water reactors (LWRs) due to significant improvement in steam oxidation by alumina forming scale and good mechanical properties up to high temperatures. In this study, the microstructural characteristics and tensile properties of the two FeCrAl ODS cladding tubes with different extrusion temperatures of 1100$$^{circ}$$C and 1150$$^{circ}$$C were investigated during processing conditions. While the hot extruded sample showed micron sized elongated grains with strong $$alpha$$-fiber in $$<$$110$$>$$ texture, cold pilger rolling process change the microstructure to submicron/micron size grain structure along with texture evolution to both $$alpha$$-fiber ($$<$$110$$>$$ texture) and $$gamma$$-fiber ({111} texture) via crystalline rotations. Subsequently, final annealing resulted in evolution of microstructure to large grain recrystallized structure starting at recrystallization temperature of $$sim$$810-850$$^{circ}$$C. Two distinct texture development happened in recrystallized cladding tubes, i.e., only large elongated grains of (110) $$<$$211$$>$$ texture following extrusion temperature of 1100$$^{circ}$$C; and two texture components of (110) $$<$$211$$>$$ and {111} $$<$$112$$>$$ following higher extrusion temperature of 1150$$^{circ}$$C. The different texture development and retarding of recrystallization progress in 1100$$^{circ}$$C-extruded cladding tubes were attributed to higher distribution of oxide particles.

Journal Articles

Overview of accident-tolerant fuel R&D program in Japan

Yamashita, Shinichiro; Ioka, Ikuo; Nemoto, Yoshiyuki; Kawanishi, Tomohiro; Kurata, Masaki; Kaji, Yoshiyuki; Fukahori, Tokio; Nozawa, Takashi*; Sato, Daiki*; Murakami, Nozomu*; et al.

Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.206 - 216, 2019/09

After the nuclear accident at Fukushima Daiichi Power Plant, research and development (R&D) program for establishing technical basis of accident-tolerant fuel (ATF) started from 2015 in Japan. Since then, both experimental and analytical studies necessary for designing a new light water reactor (LWR) core with ATF candidate materials are being conducted within the Japanese ATF R&D Consortium for implementing ATF to the existing LWRs, accompanying with various technological developments required. Until now, we have accumulated experimental data of the candidate materials by out-of-pile tests, developed fuel evaluation codes to apply to the ATF candidate materials, and evaluated fuel behavior simulating operational and accidental conditions by the developed codes. In this paper, the R&D progresses of the ATF candidate materials considered in Japan are reviewed based on the information available such as proceedings of international conference and academic papers, providing an overview of ATF program in Japan.

Journal Articles

Technical basis of accident tolerant fuel updated under a Japanese R&D project

Yamashita, Shinichiro; Nagase, Fumihisa; Kurata, Masaki; Nozawa, Takashi; Watanabe, Seiichi*; Kirimura, Kazuki*; Kakiuchi, Kazuo*; Kondo, Takao*; Sakamoto, Kan*; Kusagaya, Kazuyuki*; et al.

Proceedings of 2017 Water Reactor Fuel Performance Meeting (WRFPM 2017) (USB Flash Drive), 10 Pages, 2017/09

In Japan, the research and development (R&D) project on accident tolerant fuel and other components (ATFs) of light water reactors (LWRs) has been initiated in 2015 for establishing technical basis of ATFs. The Japan Atomic Energy Agency (JAEA) has coordinated and carried out this ATF R&D project in cooperation with power plant providers, fuel venders and universities for making the best use of the experiences, knowledges in commercial uses of zirconium-base alloys (Zircaloy) in LWRs. ATF candidate materials under consideration in the project are FeCrAl steel strengthened by dispersion of fine oxide particles(FeCrAl-ODS) and silicon carbide (SiC) composite, and are expecting to endure severe accident conditions in the reactor core for a longer period of time than the Zircaloy while maintaining or improving fuel performance during normal operations. In this paper, the progresses of the R&D project are reported.

Journal Articles

Non-aqueous selective synthesis of orthosilicic acid and its oligomers

Igarashi, Masayasu*; Matsumoto, Tomohiro*; Yagihashi, Fujio*; Yamashita, Hiroshi*; Ohara, Takashi; Hanashima, Takayasu*; Nakao, Akiko*; Moyoshi, Taketo*; Sato, Kazuhiko*; Shimada, Shigeru*

Nature Communications (Internet), 8, p.140_1 - 140_8, 2017/07

 Times Cited Count:25 Percentile:64.44(Multidisciplinary Sciences)

Journal Articles

The Welded joint strength reduction factors of modified 9Cr-1Mo Steel for the advanced loop-type sodium cooled fast reactor

Yamashita, Takuya; Wakai, Takashi; Onizawa, Takashi; Sato, Kenichiro*; Yamamoto, Kenji*

Journal of Pressure Vessel Technology, 138(6), p.061407_1 - 061407_6, 2016/12

 Times Cited Count:0 Percentile:0(Engineering, Mechanical)

Journal Articles

Material strength evaluation for 60 years design in Japanese sodium fast reactor

Nagae, Yuji; Onizawa, Takashi; Takaya, Shigeru; Yamashita, Takuya

Proceedings of 2014 ASME Pressure Vessels and Piping Conference (PVP 2014) (DVD-ROM), 9 Pages, 2014/07

JAEA Reports

Chemical composition of artificial seawater after leaching tests of irradiated fuel

Tanaka, Kosuke; Suto, Mitsuo; Onishi, Takashi; Akutsu, Yoko; Yoshitake, Tsunemitsu; Yamashita, Shinichiro; Sekioka, Ken*; Ishigamori, Toshio*; Obayashi, Hiroshi; Koyama, Shinichi

JAEA-Research 2013-036, 31 Pages, 2013/12


In the accident of Fukushima Daiichi NPPs, the water ingress was performed in order to decrease the reactor temperature. At that time, sea water was temporarily used as a coolant and the water contacted with nuclear fuel directly. It can be supposed that fission products (FP) were easily migrated from the fuel to sea water in this situation and that affect the water quality. The knowledge of leaching behavior, therefore, is necessary for evaluating the integrity of reactor component materials such as steels for pressure containment vessel and for reactor vessel. In order to obtain the fundamental knowledge for leaching behavior of FP in the hot sea water, the leaching tests of irradiated fuel were performed and the leachates were subjected to chemical analysis. It is found that he leaching rate of each nuclides obtained in this study were similar to that of the leaching results simulating the underground water.

Journal Articles

Experimental study for the production cross sections of positron emitters induced from $$^{12}$$C and $$^{16}$$O nuclei by low-energy proton beams

Akagi, Takashi*; Yagi, Masashi*; Yamashita, Tomohiro*; Murakami, Masao*; Yamakawa, Yoshiyuki*; Kitamura, Keiji*; Ogura, Koichi; Kondo, Kiminori; Kawanishi, Shunichi*

Radiation Measurements, 59, p.262 - 269, 2013/12

 Times Cited Count:14 Percentile:74.64(Nuclear Science & Technology)

In proton therapy, positron emitters are induced from $$^{12}$$C and$$^{16}$$O nuclei by protons on the beam path in the patient. Many studies for monitoring positron emitters with beam-induced PET technique have been performed by various groups to verify the proton beam range and the dose in the patient for quality assurance. The aim of this study was to develop a method for measuring the production cross sections of positron emitters using standard equipment for proton therapy. The time-activity curve was then obtained with a high-sensitivity PET scanner to extract the number of positron emitters produced in the target. The production cross sections for four reaction channels: $$^{16}$$O(p,pn)$$^{15}$$O, $$^{16}$$O(p,3p3n)$$^{11}$$C, $$^{16}$$O(p,2p2n)$$^{13}$$N, and $$^{12}$$C(p,pn)$$^{11}$$C were then measured. The cross sections for the $$^{16}$$O(p,pn)$$^{15}$$O reaction channel were consistent with data of previous experiments within the uncertainties, while those of $$^{12}$$C(p,pn)$$^{11}$$C were generally lower than data of previous experiments.

JAEA Reports

Evaluation of irradiation behavior on oxide dispersion strengthened (ODS) steel claddings irradiated in Joyo/CMIR-6

Yano, Yasuhide; Otsuka, Satoshi; Yamashita, Shinichiro; Ogawa, Ryuichiro; Sekine, Manabu; Endo, Toshiaki; Yamagata, Ichiro; Sekio, Yoshihiro; Tanno, Takashi; Uwaba, Tomoyuki; et al.

JAEA-Research 2013-030, 57 Pages, 2013/11


It is necessary to develop the fast reactor core materials, which can achieve high-burnup operation improving safety and economical performance. Ferritic steels are expected to be good candidate core materials to achieve this objective because of their excellent void swelling resistance. Therefore, oxide dispersion strengthened (ODS) ferritic steel and 11Cr-ferritic/martensitic steel (PNC-FMS) have been respectively developed for cladding and wrapper tube materials in Japan Atomic Energy Agency. In this study, the effects of fast neutron irradiation on mechanical properties and microstructure of 9Cr-and 12Cr-ODS steel claddings for fast reactor were investigated. Specimens were irradiated in the experimental fast reactor Joyo using the CMIR-6 at temperatures between 420 and 835$$^{circ}$$C to fast neutron doses ranging from 16 to 33 dpa. The post-irradiation ring tensile tests were carried out at irradiation temperatures.

Journal Articles

Polymerization mechanism for radiation-induced grafting of styrene into Alicyclic polyimide films for preparation of polymer electrolyte membranes

Park, J.; Enomoto, Kazuyuki; Yamashita, Takashi*; Takagi, Yasuyuki*; Todaka, Katsunori*; Maekawa, Yasunari

Journal of Membrane Science, 438, p.1 - 7, 2013/07

 Times Cited Count:14 Percentile:43.43(Engineering, Chemical)

Alicyclic polyimides (APIs) were successfully applied to radiation-induced graft polymerization for developing polymer electrolyte membranes for fuel cells. The grafting into fully aromatized polyimide barely proceeded (grafting degrees (GDs) of less than 5%), whereas that of styrene into the API films proceeded with styrene GDs of up to 70%. In combination of electron spin resonance measurements and ultraviolet-visible (UV-VIS) spectroscopy, the radical species was identified as a long-lived intermediate and 10% of the radicals were consumed as grafting initiators. The moderate reaction conditions allowed for selective sulfonation on the polystyrene grafts, and not on the API substrates, to give API-based polymer electrolyte membranes (PEMs) with ion exchange capacities (IEC) of 1.7-2.8 mmol/g. The PEMs exhibited appropriate proton conductivity and low water uptake, together with excellent mechanical properties, compared with conventional PEMs such as Nafion.

Journal Articles

Irradiation performance of oxide dispersion strengthened (ODS) ferritic steel claddings for fast reactor fuels

Kaito, Takeji; Otsuka, Satoshi; Yano, Yasuhide; Tanno, Takashi; Yamashita, Shinichiro; Ogawa, Ryuichiro; Tanaka, Kenya

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Safe Technologies and Sustainable Scenarios (FR-13) (USB Flash Drive), 11 Pages, 2013/03

The oxide dispersion strengthened (ODS) ferritic steel claddings developed by Japan Atomic Energy Agency were irradiated in Joyo and BOR-60 in order to confirm their irradiation performance and thus judge their applicability to high burnup and high temperature fast reactor fuels. In Joyo, material irradiation tests up to 33 dpa were carried out at in the temperature range of 693 - 1108 K. The irradiation data were obtained concerning mainly mechanical properties and of microstructure stability. In BOR-60, fuel pin irradiation tests were conducted up to burnup of 11.9 at% and neutron dose of 51 dpa. The irradiation data were obtained concerning fuel-cladding chemical interaction, dimensional stability under irradiation and so on. These results showed the superior irradiation performance of the ODS ferritic steel claddings and their application possibility as fast reactor fuels. This paper describes the evaluation of the obtained irradiation data of ODS ferritic steel claddings.

Journal Articles

Spectroellipsometric studies on EB induced refractive index change of aliphatic polyimide

Seito, Hajime; Hakoda, Teruyuki; Hanaya, Hiroaki; Haruyama, Yasuyuki; Kaneko, Hirohisa; Yamashita, Takashi*; Kojima, Takuji

JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 150, 2012/01

no abstracts in English

Journal Articles

Role of residual transition-metal atoms in oxygen reduction reaction in cobalt phthalocyanine-based carbon cathode catalysts for polymer electrolyte fuel cell

Kobayashi, Masaki*; Niwa, Hideharu*; Harada, Yoshihisa*; Horiba, Koji*; Oshima, Masaharu*; Ofuchi, Hironori*; Terakura, Kiyoyuki*; Ikeda, Takashi; Koshigoe, Yuka*; Ozaki, Junichi*; et al.

Journal of Power Sources, 196(20), p.8346 - 8351, 2011/10

 Times Cited Count:32 Percentile:67.48(Chemistry, Physical)

The electronic structure of Co atoms in CoPc-based carbon catalysts, which were prepared by pyrolyzing a mixture of CoPc and phenol resin polymer up to 1000$$^circ$$C, has been investigated using XAFS analysis and HXPES. The Co K XAFS spectra show that most of the Co atoms are in the metallic state and small quantities of oxidized Co components are present in the samples even after acid washing to remove Co atoms. Based on the difference in probing depth between XAFS and HXPES, it was found that after acid washing, the surface region with the aggregated Co clusters is primarily composed of metallic Co. Since the electrochemical properties remain almost unchanged even after the acid washing process, the residual metallic and oxidized Co atoms themselves will hardly contribute to the ORR activity of the CoPc-based carbon cathode catalysts, implying that the active sites of the CoPc-based catalysts primarily consist of light elements such as C and N.

118 (Records 1-20 displayed on this page)