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JAEA Reports

Transfer and operation of WSPEEDI-II automatic calculation system for responses to nuclear tests by North Korea

Nemoto, Miho*; Ebine, Noriya; Okamoto, Akiko; Hosaka, Yasuhisa*; Tsuzuki, Katsunori; Terada, Hiroaki; Hayakawa, Tsuyoshi; Togawa, Orihiko

JAEA-Technology 2021-013, 41 Pages, 2021/08

JAEA-Technology-2021-013.pdf:2.52MB

When North Korea has carried out nuclear tests, Nuclear Emergency Assistance and Training Center (NEAT) predicts atmospheric dispersion of radionuclides by using the WSPEEDI-II upon requests from Nuclear Regulation Authority (NRA) and submits the predicted results to NRA in cooperation with Nuclear Science and Engineering Center (NSEC). This is a part of the activity of NEAT supporting the Japanese Government in emergency responses. The WSPEEDI-II automatic calculation system specialized for responses to nuclear tests by North Korea was developed by NSEC and was used for responses to three nuclear tests from February 2013 to September 2017. This report describes the transfer and installation of the calculation system to NEAT, and the subsequent maintenance and operation. Future issues for responses to nuclear tests are also described in this report.

Journal Articles

Decrease in pitting corrosion resistance of extra-high-purity type 316 stainless-steel by Cu$$^{2+}$$ in NaCl

Aoyama, Takahito; Ogawa, Hiroaki; Kato, Chiaki; Ueno, Fumiyoshi

Metals, 11(3), p.511_1 - 511_13, 2021/03

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

The effect of Cu$$^{2+}$$ in bulk solution on pitting corrosion resistance of extra high purity type 316 stainless steel was investigated. Pitting occurred in 0.1 M NaCl-1 mM CuCl$$_2$$ whereas pitting was not initiated in 0.1 M NaCl. Although deposition of Cu$$^{2+}$$ on the surface occurred regardless of potential region in 0.1 M NaCl-1 mM CuCl$$_2$$, Cu$$^{2+}$$ in bulk solution had no influence on the passive film formation. The decrease in pitting corrosion resistance in 0.1 M NaCl-1 mM CuCl$$_2$$ resulted from the deposited Cu or Cu compound and continuous supply of Cu$${2+}$$ on the surface.

Journal Articles

Investigation of dominant factors accelerating corrosion under gamma-ray irradiation

Ogawa, Hiroaki; Ioka, Ikuo

QST-M-29; QST Takasaki Annual Report 2019, P. 71, 2021/03

The objective of our research is to clarify corrosion acceleration mechanism of materials under the gamma-ray radiation environment. The irradiation experiment was conducted for 30 mins at the gamma-ray irradiation facility of Takasaki Advanced Radiation Research Institute of QST. During the gamma-ray irradiation, pH decreases, and also the electric conductivity showed a tendency to increase. The concentration of hydrogen peroxide in water was measured after irradiation and was about 3.5$$times$$10$$^{-4}$$ wt%. When the concentration is less than 10 wt%, the pH value decreases with increasing the concentration. A pH of 3.5$$times$$10$$^{-4}$$ wt% hydrogen peroxide water was 5.58. This was almost same as the pH value (5.56) of purified water. It seems that the decrease of pH after irradiation is not able to explain by the production of hydrogen peroxide.

Journal Articles

Stress corrosion cracking of copper in swollen bentonite simulating nuclear waste disposal environment

Fujimoto, Shinji*; Tsuchiya, Hiroaki*; Ogawa, Soma*; Iida, Yoshihisa; Taniguchi, Naoki

Materials and Corrosion, 72(1-2), p.333 - 338, 2021/01

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

The stress corrosion cracking (SCC) of pure copper in bentonite was examined by a slow strain rate test (SSRT). The bentonite was swollen with pure water or aqueous solutions containing NH$$_{3}$$ of 0.05 M and 0.1 M. The thick corrosion films and particulate deposits were formed on copper surface after SSRT. Typical tarnish rupture type SCC occurred on pure copper in swollen bentonite with and without NH$$_{3}$$. Crack propagation rate was enhanced by NH$$_{3}$$. It is confirmed thick oxide layer is formed on copper during plastic deformation which resulting in the tarnish crack type SCC. The many particulate deposits observed on the surface might be formed as a results of rapid dissolution of Cu$$^{2+}$$ to form porous CuO at locallized deformed sites.

Journal Articles

Comprehensive understanding of hillocks and ion tracks in ceramics irradiated with swift heavy ions

Ishikawa, Norito; Taguchi, Tomitsugu*; Ogawa, Hiroaki

Quantum Beam Science (Internet), 4(4), p.43_1 - 43_14, 2020/12

Amorphizable ceramics were irradiated with 200 MeV Au ions, and the as-irradiated samples were observed by transmission electron microscopy (TEM). The ion track diameter and hillock diameter are similar for all the amorphizable ceramics. For SrTiO$$_{3}$$ and niobium-doped STO, 200 MeV Au ion irradiation and TEM observation were also performed. The ion track diameters in these materials are found to be markedly smaller than the hillock diameters. The ion tracks in these materials exhibit inhomogeneity, which is similar to that reported for non-amorphizable ceramics. On the other hand, the hillocks appear to be amorphous, and the amorphous feature is in contrast to the crystalline feature of hillocks observed in non-amorphizable ceramics. No marked difference is recognized between the nanostructures in STO and those in Nb-STO.

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

Development of fabrication technology for oxidation-resistant fuel elements for high-temperature gas-cooled reactors

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

Nihon Genshiryoku Gakkai Wabun Rombunshi, 18(1), p.29 - 36, 2019/03

Japan Atomic Energy Agency carried out development of fabrication technology of oxidation resistant fuel element for improvement of safety of high temperature gas-cooled reactors in serious oxidation accident, based on precursor research in former JAEA. Dummy coated fuel particles (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 dummy oxidation resistant fuel elements with SiC/C mixed matrix. We fabricated dummy oxidation resistant fuel elements with matrix whose Si/C mole ratio (about 0.551) is three times as large as that in precursor research. Si peak was not detected by X-ray diffraction of matrix. Better oxidation resistant was confirmed with oxidation test in 20% O$$_{2}$$ at 1673 K than that of ordinal fuel compact with ordinal graphite/carbon matrix. All dummy coated fuel particles were held in specimen after 10 h oxidation.

Journal Articles

Enhancement of Fe-N-C carbon catalyst activity for the oxygen reduction reaction; Effective increment of active sites by a short and repeated heating process

Yasuda, Satoshi; Uchibori, Yosuke*; Wakeshima, Makoto*; Hinatsu, Yukio*; Ogawa, Hiroaki; Yano, Masahiro; Asaoka, Hidehito

RSC Advances (Internet), 8(66), p.37600 - 37605, 2018/11

 Times Cited Count:7 Percentile:42.43(Chemistry, Multidisciplinary)

We present a quantitative study on the effect of a newly obtained thermal history on the formation of Fe-N-C catalytic sites. A short and repeated heating process is employed as the new thermal history, where short heating (1 min) followed by quenching is applied to a sample with arbitrary repetition. Through electrochemical quantitative analysis, it is found that the new process effectively increases the Fe-N-C mass-based site density (MSD) to almost twice that achieved using a conventional continuous heating process, while the turn-over frequency (TOF) is independent of the process. Elemental analysis shows that the new process effectively suppresses the thermal desorption of Fe and N atoms during the initial formation stage and consequently contributes to an increase in the Fe-N-C site density. The resultant catalytic activity (gravimetric kinetic current density (0.8 V vs. RHE)) is 1.8 times higher than that achieved with the continuous heating process.

JAEA Reports

Activities on predictions of atmospheric dispersion of radionuclides for nuclear tests by North Korea

Ishizaki, Shuhei; Hayakawa, Tsuyoshi; Tsuzuki, Katsunori; Terada, Hiroaki; Togawa, Orihiko

JAEA-Technology 2018-007, 43 Pages, 2018/10

JAEA-Technology-2018-007.pdf:5.67MB

When North Korea has carried out a nuclear test, by a request from Nuclear Regulation Authority (NRA), Nuclear Emergency Assistance and Training Center (NEAT) predicts atmospheric dispersion of radionuclides by WSPEEDI-II system in cooperation with Nuclear Science and Engineering Center (NSEC), and submits the predicted results to NRA as the activity to assist responses by the Japanese Government. This report explains frameworks of the Japanese Government and Japan Atomic Energy Agency (JAEA) to cope with nuclear tests by North Korea, and describes a series of activities by NEAT regarding predictions of atmospheric dispersion of radionuclides in response to the 5th and 6th nuclear tests carried out by North Korea in September 2016 and September 2017. Future plans and issues to be solved for responses to nuclear tests are also described in this report, together with an outline of a computer program system used in the predictions.

JAEA Reports

Handbook of advanced nuclear hydrogen safety (1st Edition)

Hino, Ryutaro; Takegami, Hiroaki; Yamazaki, Yukie; Ogawa, Toru

JAEA-Review 2016-038, 294 Pages, 2017/03

JAEA-Review-2016-038.pdf:11.08MB

In the aftermath of the Fukushima nuclear accident, safety measures against hydrogen in severe accident have been recognized as a serious technical problem in Japan. Therefore, efforts have begun to form a common knowledge base between nuclear engineers and experts on combustion and explosion, and to secure and improve future nuclear energy safety. As one of such activities, we have prepared the "Handbook of Advanced Nuclear Hydrogen Safety" under the Advanced Nuclear Hydrogen Safety Research Program funded by the Agency for Natural Resources and Energy of the Ministry of Economy, Trade and Industry. The concepts of the handbook are as follows: to show advanced nuclear hydrogen safety technologies that nuclear engineers should understand, to show hydrogen safety points to make combustion-explosion experts cooperate with nuclear engineers, to expand information on water radiolysis considering the situation from just after the Fukushima accidents and to the waste management necessary for decommissioning after the accident, etc.

Journal Articles

Development of instrumentation and control systems for the ITER diagnostic systems in JADA

Yamamoto, Tsuyoshi; Hashimoto, Yasunori*; Kitazawa, Sin-iti; Yatsuka, Eiichi; Hatae, Takaki; Sugie, Tatsuo; Ogawa, Hiroaki; Takeuchi, Masaki; Kawano, Yasunori; Itami, Kiyoshi

Fusion Engineering and Design, 96-97, p.1012 - 1016, 2015/10

 Times Cited Count:4 Percentile:40.75(Nuclear Science & Technology)

Japan Domestic Agency (JADA) is responsible for six diagnostic systems in the ITER project. We have successfully developed an instrumentation and control (I&C) system for the diagnostic systems. The I&C system manages internal operations for measurement such as health checks of sensors, configuration of measurement parameters, and consistency checks between measurement parameters. We developed a conversion tool to convert operational flowcharts to EPICS records. The sequencing management function coordinates the execution of operation steps by monitoring changes in the record values. It was designed so that the relationship between the records and steps is determined automatically according to the flowcharts as much as possible. We validated the performance of the I&C system for the thermocouple measurement system, and are continuing the development of even more complex I&C systems for other JADA diagnostic systems.

Journal Articles

Preparation for lower port integration engineering for ITER diagnostic systems in JADA

Kitazawa, Sin-iti; Maruyama, Toshiyuki; Ogawa, Hiroaki; Itami, Kiyoshi; Casal, N.*

Plasma and Fusion Research (Internet), 10(Sp.2), p.3402044_1 - 3402044_4, 2015/04

Journal Articles

Development of divertor IR thermography for ITER

Takeuchi, Masaki; Sugie, Tatsuo; Ogawa, Hiroaki; Ishikawa, Masao; Shimada, Takahiko; Kusama, Yoshinori

Plasma and Fusion Research (Internet), 8(Sp.1), p.2402147_1 - 2402147_5, 2013/11

Divertor IR Thermography is one of the diagnostics which Japan is in charge of development in ITER project. The conceptual design has been performed so far, and the progress is reported here. By reducing the size of mirrors, and making the optical path a labyrinthine structure, the design of a new optics that fills requirements of both spatial resolution and neutron shielding has been advanced. To achieve the required measurement accuracy, the detected signal and the noises such as bremsstrahlung light, detector noise and thermal noise of optical components were evaluated. Higher photons than the bremsstrahlung light are obtained, excluding the low temperature range. The simulation calculation of reflection from wall was started. Detailed method of data processing of deriving the profiles of surface temperature in the divertor plates from the observed signals and in-situ calibration strategies of the optical system are important issues and will be discussed.

Journal Articles

The First electron bunch measurement by means of dast organic EO crystals

Okayasu, Yuichi*; Tomizawa, Hiromitsu*; Matsubara, Shinichi*; Sato, Takahiro*; Ogawa, Kanade*; Togashi, Tadashi*; Takahashi, Eiji*; Minamide, Hiroaki*; Matsukawa, Ken*; Aoyama, Makoto; et al.

Proceedings of 1st International Beam Instrumentation Conference (IBIC 2012) (Internet), 5 Pages, 2012/10

no abstracts in English

JAEA Reports

Bi-directional reflectance distribution function of a tungsten block for ITER divertor

Iwamae, Atsushi*; Ogawa, Hiroaki; Sugie, Tatsuo; Kusama, Yoshinori

JAEA-Research 2011-045, 11 Pages, 2012/02

JAEA-Research-2011-045.pdf:2.36MB

In order to investigate reflection properties on plasma-facing material in ITER, the bi-directional reflectance distribution function (BRDF) of a tungsten block sample has been measured. On the machining surface of the block, one-directional machining lines are engraved. Two laser diodes $$lambda$$652 nm and $$lambda$$473 nm were used to simulate H$$_{alpha}$$ and H$$_{beta}$$ emissions, respectively. The reflected light is affected by the machining surface. The reflected light traces a line when the incident light is injected in the perpendicular direction to the engraved line. On the other hand the reflected light traces an arc shape when the incident light is injected in the parallel direction to the engraved lines. Ray tracing simulation qualitatively explains the experimental results.

Journal Articles

Synthesized intensity of emission lines of hydrogen isotopes and impurities in the ITER divertor plasma

Iwamae, Atsushi; Sugie, Tatsuo; Ogawa, Hiroaki; Kusama, Yoshinori

Plasma Physics and Controlled Fusion, 53(4), p.045005_1 - 045005_17, 2011/04

 Times Cited Count:2 Percentile:11.76(Physics, Fluids & Plasmas)

Journal Articles

${it In-situ}$ spectral calibration method for the impurity influx monitor (divertor) for ITER using angled physical contact fibers

Iwamae, Atsushi; Ogawa, Hiroaki; Sugie, Tatsuo; Kusama, Yoshinori

Review of Scientific Instruments, 82(3), p.033502_1 - 033502_4, 2011/03

 Times Cited Count:3 Percentile:19.8(Instruments & Instrumentation)

Journal Articles

Reply to comment on "A Statistical-mechanical method to evaluate hydrogen solubility in metal"

Ogawa, Hiroaki

Journal of Physical Chemistry C, 114(36), p.15544 - 15545, 2010/08

 Times Cited Count:1 Percentile:66.89(Chemistry, Physical)

no abstracts in English

Journal Articles

A Statistical-mechanical method to evaluate hydrogen solubility in metal

Ogawa, Hiroaki

Journal of Physical Chemistry C, 114(5), p.2134 - 2143, 2010/01

 Times Cited Count:9 Percentile:32.88(Chemistry, Physical)

I propose a site-occupying model for hydrogen solution in metal because there is a logical discrepancy between the concept of conventional site-blocking models and an experimental fact. This model is based on the experimental fact that hydrogen atoms in metal cannot mutually come closer to less than about 0.21nm each other under hydrogen pressure of 1MPa or less. The solubility has been analyzed, developing a statistical-mechanical method. The validity of this method has been judged by agreement with experimental data on the solubility. Comparisons also have been made between the conventional site-blocking models and this model. This model can make its theoretical curve agree well with the experimental data compared to those of the conventional site-blocking models at high hydrogen solubility over 0.5H/M. In the statistical-mechanical description, the solution behavior of tritium is similar to that of hydrogen, rather than that of deuterium from the difference in the spin weights.

Journal Articles

180 (Records 1-20 displayed on this page)