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Journal Articles

Interlaboratory comparison of electron paramagnetic resonance tooth enamel dosimetry with investigations of the dose responses of the standard samples

Toyoda, Shin*; Inoue, Kazuhiko*; Yamaguchi, Ichiro*; Hoshi, Masaharu*; Hirota, Seiko*; Oka, Toshitaka; Shimazaki, Tatsuya*; Mizuno, Hideyuki*; Tani, Atsushi*; Yasuda, Hiroshi*; et al.

Radiation Protection Dosimetry, 199(14), p.1557 - 1564, 2023/09

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

Interlaboratory comparison studies are important for radiation dosimetry in order to demonstrate how the technique is universally available. The set of standard samples are examined in each participating laboratory in the present study. After a set of standard samples together with the samples with unknown doses, which were prepared in the same laboratory as the standard samples, are measured at a participating laboratory, those samples are sent to another participating laboratory for next measurement. There is some small difference observed in the sensitivity (the slope of the dose response line) of the standard samples while the differences in the obtained doses for the samples with unknown doses are rather systematic, implying that the difference is mostly due to the samples but not to measurements.

Journal Articles

Development of safety design philosophy of HTTR-Heat Application Test Facility

Aoki, Takeshi; Shimizu, Atsushi; Noguchi, Hiroki; Kurahayashi, Kaoru; Yasuda, Takanori; Nomoto, Yasunobu; Iigaki, Kazuhiko; Sato, Hiroyuki; Sakaba, Nariaki

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 9 Pages, 2023/05

The safety design philosophy is developed for the HTTR (High Temperature Engineering Test Reactor) heat application test facility connecting high temperature gas-cooled reactor (HTGR) and the hydrogen production plant. The philosophy was proposed to apply proven conventional chemical plant standards to the hydrogen production facility for ensuring public safety against anticipated disasters caused by high pressure and combustible gases. The present study also proposed the safety design philosophy to meet specific safety requirements identified to the nuclear facilities with coupling to the hydrogen production facility such as measures to ensure a capability of normal operation of the nuclear facility against a fire and/or explosion of leaked combustible material, and fluctuation of amount of heat removal occurred in the hydrogen production plant. The safety design philosophy will be utilized to establish its basic and detailed designs of the HTTR-heat application test facility.

Journal Articles

Development plan for coupling technology between high temperature gas-cooled reactor HTTR and hydrogen production facility, 1; Overview of the HTTR heat application test plan to establish high safety coupling technology

Nomoto, Yasunobu; Mizuta, Naoki; Morita, Keisuke; Aoki, Takeshi; Okita, Shoichiro; Ishii, Katsunori; Kurahayashi, Kaoru; Yasuda, Takanori; Tanaka, Masato; Isaka, Kazuyoshi; et al.

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 7 Pages, 2023/05

Journal Articles

Development plan for coupling technology between high temperature gas-cooled reactor HTTR and Hydrogen Production Facility, 2; Development plan for coupling equipment between HTTR and Hydrogen Production Facility

Mizuta, Naoki; Morita, Keisuke; Aoki, Takeshi; Okita, Shoichiro; Ishii, Katsunori; Kurahayashi, Kaoru; Yasuda, Takanori; Tanaka, Masato; Isaka, Kazuyoshi; Noguchi, Hiroki; et al.

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 6 Pages, 2023/05

Journal Articles

Efficient hydrogen isotope separation by tunneling effect using graphene-based heterogeneous electrocatalysts in electrochemical hydrogen isotope pumping

Yasuda, Satoshi; Matsushima, Hisayoshi*; Harada, Kenji*; Tanii, Risako*; Terasawa, Tomoo; Yano, Masahiro; Asaoka, Hidehito; Gueriba, J. S.*; Di$~n$o, W. A.*; Fukutani, Katsuyuki

ACS Nano, 16(9), p.14362 - 14369, 2022/09

 Times Cited Count:12 Percentile:85.62(Chemistry, Multidisciplinary)

The fabrication of hydrogen isotope enrichment system is essential for the development of industrial, medical, life science, and nuclear fusion fields, therefore alternative enrichment techniques with high separation factor and economic feasibility have been still explored. Herein, we report the fabrication of heterogeneous electrode with layered structures consisting of palladium and graphene layers for polymer electrolyte membrane electrochemical hydrogen pumping for the hydrogen isotope enrichment. We demonstrated significant bias voltage dependence of hydrogen/deuterium (H/D) separation ability and its high H/D at lower bias voltage. Theoretical analysis also demonstrated that the observed high H/D at low bias voltage stems from hydrogen isotopes tunneling through atomically-thick graphene during the electrochemical reaction, and the bias dependent H/D results in a transition from the quantum tunneling regime to classical over- barrier regime for hydrogen isotopes transfer via the graphene. These findings provide new insight for a novel economical methodology of efficient hydrogen isotope enrichment.

Journal Articles

Production of $$^{266}$$Bh in the $$^{248}$$Cm($$^{23}$$Na,5$$n$$)$$^{266}$$Bh reaction and its decay properties

Haba, Hiromitsu*; Fan, F.*; Kaji, Daiya*; Kasamatsu, Yoshitaka*; Kikunaga, Hidetoshi*; Komori, Yukiko*; Kondo, Narumi*; Kudo, Hisaaki*; Morimoto, Koji*; Morita, Kosuke*; et al.

Physical Review C, 102(2), p.024625_1 - 024625_12, 2020/08

 Times Cited Count:6 Percentile:59.56(Physics, Nuclear)

Journal Articles

Development of fabrication and inspection technologies for oxidation-resistant fuel element for high-temperature gas-cooled reactors

Aihara, Jun; Yasuda, Atsushi*; Ueta, Shohei; Ogawa, Hiroaki; Honda, Masaki*; Ohira, Koichi*; Tachibana, Yukio

Nihon Genshiryoku Gakkai Wabun Rombunshi, 18(4), p.237 - 245, 2019/12

Development of fabrication and inspection technologies of oxidation resistant fuel element for improvement of safety of high temperature gas-cooled reactors (HTGRs) in severe oxidation accident was carried out. Simulated coated fuel particles (CFPs), alumina particles, were over-coated with mixed powder of Si, C and small amount of resin to form over-coated particles, and over-coated particles were molded and hot-pressed to sinter simulated oxidation resistant fuel elements with SiC/C mixed matrix. Simulated oxidation resistant fuel elements with matrix whose Si/C mole ratio is 1.00 were fabricated. Failure fraction of CFPs in fuel elements is one of very important inspection subjects of HTGR fuel. It is essential that CFPs are extracted from fuel elements without additional failure. Development of method for extraction of CFPs was carried out. Desolation of SiC by KOH method or pressurized acidolysis method should be applied to extraction of CFPs.

Journal Articles

Variation of half-life and internal-conversion electron energy spectrum between $$^{235m}$$U oxide and fluoride

Shigekawa, Yudai*; Kasamatsu, Yoshitaka*; Yasuda, Yuki*; Kaneko, Masashi; Watanabe, Masayuki; Shinohara, Atsushi*

Physical Review C, 98(1), p.014306_1 - 014306_5, 2018/07

 Times Cited Count:4 Percentile:36.29(Physics, Nuclear)

The nuclear half-life of $$^{235m}$$U has been reported to vary depending on the chemical environment. In this study, both the half-life and the internal-conversion (IC) electron energy spectrum were measured for $$^{235m}$$U with identical chemical environments for the first time. $$^{235m}$$U oxide and fluoride samples were subjected to these measurements, and clear differences in the half-life and the energy spectrum between these samples were observed. The peaks in the energy spectra were identified with the relativistic density functional theory calculation, and the molecular orbital states of the $$^{235m}$$U oxide and fluoride estimated from the energy spectra and the calculation qualitatively explained the difference in the half-lives between the samples.

Journal Articles

Feasibility study of advanced measurement technology for solution monitoring at reprocessing plant; Dose rate measurement for the solution including Pu with FP

Matsuki, Takuya; Yamanaka, Atsushi; Sekine, Megumi; Suzuki, Satoshi*; Yasuda, Takeshi; Tsutagi, Koichi; Tomikawa, Hirofumi; Nakamura, Hironobu; LaFleur, A. M.*; Browne, M. C.*

Proceedings of INMM 58th Annual Meeting (Internet), 8 Pages, 2017/07

The Tokai Reprocessing Plant (TRP) has been developing a new detector from 2015 to 2017 for purpose to monitor Pu amount in High Active Liquid Waste (HALW) containing FP. It can make a contribution to an advanced approach to effectively and efficiently conduct safeguards for reprocessing facilities because it becomes available to monitor and verify nuclear material movement continuously by a new detector, which has proposed by IAEA. For the second step of this project, we conducted dose rate measurement on the guide rail installing in the cell storing the HALW tank and comparison between measured dose rate distribution and calculation result by MCNP simulation in order to investigate the dose rate distribution which is needed for shielding design of a new detector that is used for radiation (neutron/$$gamma$$ spectrum) measurement in the cell and inquest on the monitoring position of the detector for Pu monitoring. In this paper, we report the result of the dose rate measurement in the cell, improvement of the simulation model which is cleared by comparison between measurement result and calculation result and our future plan.

Journal Articles

Feasibility study of advanced technology for Pu with FP solution monitoring; Overview of research plan and modelling for simulation

Sekine, Megumi; Matsuki, Takuya; Suzuki, Satoshi; Tanigawa, Masafumi; Yasuda, Takeshi; Yamanaka, Atsushi; Tsutagi, Koichi; Nakamura, Hironobu; Tomikawa, Hirofumi; LaFleur, A. M.*; et al.

EUR-28795-EN (Internet), p.788 - 796, 2017/00

The IAEA has proposed in its long-term R&D plan, the development of technology to enable real-time flow measurement of nuclear material as a part of an advanced approach to effective and efficient safeguards for reprocessing facilities. To address this, JAEA has designed and developed a neutron coincidence based nondestructive assay system to monitor Pu directly in solutions which is after purification process and contains very little fission products (FPs). A new detector to enable monitoring of Pu in solutions with numerous FPs is being developed as a joint research program with U.S. DOE at the High Active Liquid Waste (HALW) Storage Facility in Tokai Reprocessing Plant. As the first step, the design information of HALW tank was investigated and samples of HALW was taken and analyzed for Pu concentration and isotope composition, density, content of dominant nuclides emitting $$gamma$$ ray or neutron, etc. in order to develop a Monte Carlo N-Particle Transport Code (MCNP) of the HALW tank. In addition, $$gamma$$ ray source spectra simulated by Particle and Heavy Ion Transport code System (PHITS) was developed by extracting peaks from the analysis data with germanium detector. These outputs are used for the fundamental data in the MCNP model which is then used to evaluate the type of detector, shielding design and measurement positions. In order to evaluate available radiations to measure outside the cell wall, continuous $$gamma$$ ray and neutron measurement were carried out and the results were compared to the simulation results. The measurement results showed that there are no FP peaks above 3 MeV. This paper presents an overview of the research plan, characteristics of HALW, development of source term for MCNP, simulation of radiation dose from the HALW tank and radiation measurement results at outside of cell wall.

Journal Articles

Measurement of fluorine distribution in carious enamel around 1.5-year aged fluoride-containing materials

Komatsu, Hisanori*; Kojima, Kentaro*; Funato, Yoshiki*; Matsuda, Yasuhiro*; Kijimura, Taiki*; Okuyama, Katsushi*; Yamamoto, Hiroko*; Iwami, Yukiteru*; Ebisu, Shigeyuki*; Nomachi, Masaharu*; et al.

JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 85, 2012/01

Journal Articles

Study on defects in H$$^+$$ ion implanted B2 type Fe-Al alloy using slow positron beam

Komagata, Eiichi*; Kawasuso, Atsuo; Yabuuchi, Atsushi*; Maekawa, Masaki; Batchuluun, C.*; Yasuda, Keisuke*; Ishigami, Ryoya*; Kume, Kyo*; Iwase, Akihiro*; Hori, Fuminobu*

Physics Procedia, 35, p.75 - 79, 2012/00

 Times Cited Count:2 Percentile:62.54(Physics, Particles & Fields)

Fe48-at.% Al alloy were implanted with 50 keV H$$^+$$ ions to the fluence of 3$$times$$10$$^{16}$$ and 1$$times$$10$$^{18}$$ /cm$$^2$$ at room temperature. Positron annihilation Doppler broadening and lifetime measurements for these alloys have been carried out using slow positron beam apparatus with an energy range of 0.2 to 30.2 keV. The positron annihilation S-parameter decreased by H$$^+$$ ion irradiation. Also the positron lifetimes for hydrogen deposited region in the alloy decreased by the irradiation. These results show that implanted H atoms were trapped by vacancy type defects.

Journal Articles

Fluorine analysis of human enamel around fluoride-containing materials under different pH-cycling by $$mu$$-PIGE/PIXE system

Komatsu, Hisanori*; Yamamoto, Hiroko*; Matsuda, Yasuhiro*; Kijimura, Taiki*; Kinugawa, Michihiko*; Okuyama, Katsushi*; Nomachi, Masaharu*; Yasuda, Keisuke*; Sato, Takahiro; Oikawa, Masakazu*

Nuclear Instruments and Methods in Physics Research B, 269(20), p.2274 - 2277, 2011/10

 Times Cited Count:18 Percentile:78.83(Instruments & Instrumentation)

Journal Articles

Development of high temperature gas-cooled reactor (HTGR) fuel in Japan

Ueta, Shohei; Aihara, Jun; Sawa, Kazuhiro; Yasuda, Atsushi*; Honda, Masaki*; Furihata, Noboru*

Progress in Nuclear Energy, 53(7), p.788 - 793, 2011/09

 Times Cited Count:27 Percentile:87.94(Nuclear Science & Technology)

In Japan, high temperature gas-cooled reactor (HTGR) fuel fabrication technologies have been developed by Nuclear Fuel Industries, Ltd. (NFI) with the collaboration of JAEA through the HTTR project since 1960's. NFI successfully fabricated first and second loading fuel (0.9 tU each) for the HTTR of JAEA. Its excellent quality was confirmed from the first loading fuel through the long-termed high temperature operation by the end of March 2010. Based on the HTTR fuel technologies, silicon carbide (SiC) coated fuel is being developed for burn-up extension. For an advanced fuel designs, replacement of the SiC layer by a zirconium carbide (ZrC) layer is a very promising example. JAEA has performed ZrC coating tests to investigate the influence of coating parameters and material properties such as stoichiometry and density of ZrC.

Journal Articles

Development of wavelength-shifting-fiber neutron image detector with a fiber-optic taper with a high spatial resolution

Nakamura, Tatsuya; Yasuda, Ryo; Katagiri, Masaki*; To, Kentaro; Sakasai, Kaoru; Birumachi, Atsushi; Ebine, Masumi; Soyama, Kazuhiko

Proceedings of 2011 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC 2011), Vol.1, p.382 - 384, 2011/00

The neutron image detector that was based on wavelength-shifting-fibers (WLS fibres) equipped with the fibre optic taper (FOT) was developed. By inserting the FOT in between the scintillator and WLS fibers the measured neutron image was magnified on the WLS fibres, resulting in better spatial resolution. We have tested two FOTs; a square shaped one in a size of 2.6 $$times$$ 2.6 mm and a round shaped with a diameter of 20 mm. Both FOTs have identical magnification ratios of 3.1. By implementing the larger FOT the detector has the neutron-sensitive area of 314 mm$$^{2}$$ with the effective pixel size of 0.17 $$times$$ 0.17 mm$$^{2}$$ whilst the light transmission rate decreased 20% less compared to that with the small FOT. The detector equipped with the larger FOT exhibited a spatial resolution of 0.26 $$pm$$ 0.07 mm, which was similar to the one with the small FOT.

Journal Articles

Effect of heat treatment on TEM microstructures of Zirconium carbide coating layer in fuel particle for advanced high temperature gas cooled reactor

Aihara, Jun; Ueta, Shohei; Yasuda, Atsushi*; Takeuchi, Hitoshi*; Mozumi, Yasuhiro*; Sawa, Kazuhiro; Motohashi, Yoshinobu*

Materials Transactions, 50(11), p.2631 - 2636, 2009/11

 Times Cited Count:8 Percentile:45.88(Materials Science, Multidisciplinary)

The ZrC coating layer has been fabricated using the bromide process at JAEA. The coated particles with IPyC layers reported in a previous study were annealed at around 1800$$^{circ}$$C for 1h, under which compact sintering will be done in a practical process, in order to study effects of the heat treatment (annealing) on their microstructure evolution. Then the microstructures of the ZrC layers in the cases (batches) of C/Zr = 1.11 and 1.35 were characterized by means of TEM and STEM. Certain changes in the shape and size of voids or free carbons region caused by the heat treatment were found in the cases of both batches. After the heat treatment, the voids or free carbons region have shown a clod like feature with diameters of 50 to 100 nm. The grain growth of ZrC was also observed in both cases: In the ZrC layer with C/Zr = 1.11, the fibrous carbons grew as of to stand from the PyC to ZrC layers on some places in the IPyC/ZrC boundary.

Journal Articles

Adsorption of Db and its homologues Nb and Ta, and the pseudo-homologue Pa on anion-exchange resin in HF solution

Tsukada, Kazuaki; Haba, Hiromitsu*; Asai, Masato; Toyoshima, Atsushi; Akiyama, Kazuhiko*; Kasamatsu, Yoshitaka; Nishinaka, Ichiro; Ichikawa, Shinichi; Yasuda, Kenichiro; Miyamoto, Yutaka; et al.

Radiochimica Acta, 97(2), p.83 - 89, 2009/02

 Times Cited Count:20 Percentile:77.78(Chemistry, Inorganic & Nuclear)

Anion-exchange chromatography of element 105, dubnium (Db), produced in the $$^{248}$$Cm($$^{19}$$F, 5n)$$^{262}$$Db reaction is investigated together with the homologues Nb and Ta, and the pseudo-homologue Pa in 13.9 M hydrofluoric acid (HF) solution. The distribution coefficient (K$$_{d}$$) of Db on an anion-exchange resin is successfully determined by running cycles of the 1702 chromatographic column separations. The result clearly indicates that the adsorption of Db on the resin is significantly different from that of the homologues and that the adsorption of anionic fluoro complexes of these elements decreases in the sequence of Ta $$approx$$ Nb $$>$$ Db $$geq$$ Pa.

JAEA Reports

Development of production technology of ZrC-coated particle, 2 (Contract research)

Yasuda, Atsushi; Ueta, Shohei; Aihara, Jun; Ishibashi, Hideharu*; Sawa, Kazuhiro

JAEA-Technology 2008-083, 11 Pages, 2009/01


The Very-High-Temperature Reactor (VHTR) is one of the candidates for the Generation IV nuclear energy system. ZrC coated fuel particles are expected to make the performance of the VHTR higher. Therefore, we are investigating the ZrC-coating process. From April 2007 to March 2008, ZrC-outer pyrolytic carbon (OPyC) layer continuous coating tests were carried out with the nonnuclear particles and we succeeded to coat continuously the ZrC layer and the OPyC layer with the thicknesses up to about 27 and about 48 $$mu$$m, respectively, in the batch scale of 100 g.

Journal Articles

TEM/STEM observation of ZrC coating layer for advanced high-temperature gas-cooled reactor fuel, Part II

Aihara, Jun; Ueta, Shohei; Yasuda, Atsushi; Ishibashi, Hideharu; Mozumi, Yasuhiro; Sawa, Kazuhiro; Motohashi, Yoshinobu*

Journal of the American Ceramic Society, 92(1), p.197 - 203, 2009/01

 Times Cited Count:7 Percentile:42.38(Materials Science, Ceramics)

The ZrC coating layer was fabricated with bromide process at JAEA. In a later stage of the project, we have successfully kept nominal deposition temperature almost constant. Microstructures of the ZrC layers, of which nominal deposition temperatures were able to measure, were characterized by means of TEM and STEM and the results were compared and discussed with those obtained for different batches including those reported in a previous study. The ZrC grains were oriented in the ZrC layers deposited at about 1630 K. This feature was rather different from that reported in the previous study. The formation of fairly different PyC structures was found on the PyC/ZrC boundary as well as around the pores existing near the boundary. Fibrous carbons were observed on the PyC/ZrC boundary produced in a batch deposited at a higher temperature (nominal temperature was 1769 K); no such fibrous carbons were found in a batch deposited at a lower temperature (nominal temperature was 1632 K).

Journal Articles

High-spatial-resolution neutron image detector based on wavelength-shifting fiber read out for time-of-flight measurements

Nakamura, Tatsuya; Yasuda, Ryo; Katagiri, Masaki*; To, Kentaro; Sakasai, Kaoru; Birumachi, Atsushi; Ebine, Masumi; Soyama, Kazuhiko

Proceedings of 2009 IEEE Nuclear Science Symposium and Medical Imaging Conference (2009 NSS/MIC), Vol.2, p.1271 - 1273, 2009/00

 Times Cited Count:1 Percentile:54.1(Engineering, Electrical & Electronic)

A wavelength-shifting-fiber based neutron image detector with a spatial resolution of less 200 $$mu$$m was developed. The detector had a capability of clear imaging with a temporal resolution of several $$mu$$s. The detector equipped with a ZnS/$$^{6}$$LiF scintillator where the scintillation light was read out with individual fibers based on a photon counting method. The fiber optic tapers (FOTs) were implemented in between the scintillator and the fibers to magnify a neutron image. The prototype detector that equipped with the FOTs exhibited the spatial resolution, which was improved by an order better compared that with the original detector. This kind of detector would be a quite unique and powerful tool for energy-selective neutron radiography at a pulsed source.

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