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Journal Articles

Numerical evaluation on fluctuation absorption characteristics based on nuclear heat supply fluctuation test using HTTR

Takada, Shoji; Honda, Yuki*; Inaba, Yoshitomo; Sekita, Kenji; Nemoto, Takahiro; Tochio, Daisuke; Ishii, Toshiaki; Sato, Hiroyuki; Nakagawa, Shigeaki; Sawa, Kazuhiro*

Proceedings of 9th International Topical Meeting on High Temperature Reactor Technology (HTR 2018) (USB Flash Drive), 7 Pages, 2018/10

Nuclear heat utilization systems connected to HTGRs will be designed on the basis of non-nuclear grade standards for easy entry of chemical plant companies, requiring reactor operations to continue even if abnormal events occur in the systems. The inventory control is considered as one of candidate methods to control reactor power for load following operation for siting close to demand area, in which the primary gas pressure is varied while keeping the reactor inlet and outlet coolant temperatures constant. Numerical investigation was carried out based on the results of nuclear heat supply fluctuation tests using HTTR by non-nuclear heating operation to focus on the temperature transient of the reactor core bottom structure by imposing stepwise fluctuation on the reactor inlet temperature under different primary gas pressures below 120C. As a result, it was emerged that the fluctuation absorption characteristics are not deteriorated by lowering pressure. It was also emerged that the reactor outlet temperature did not reach the scram level by increasing the reactor inlet temperature 10 C stepwise at 80% of the rated power as same with the full power case.

Journal Articles

A Kinetic analysis of cadmium accumulation in a Cd hyper-accumulator fern, ${it Athyrium yokoscense}$ and tobacco plants

Yoshihara, Toshihiro*; Suzui, Nobuo; Ishii, Satomi; Kitazaki, Mayu*; Yamazaki, Haruaki*; Kitazaki, Kazuyoshi*; Kawachi, Naoki; Yin, Y.-G.; Tanabata, Sayuri*; Hashida, Shinnosuke*; et al.

Plant, Cell & Environment, 37(5), p.1086 - 1096, 2014/05

 Times Cited Count:15 Percentile:34.15(Plant Sciences)

Journal Articles

Extraction of chromatographic behavior of Rf, Zr, and Hf in HCl solution with styrenedivinylbenzene copolymer resin modified by TOPO (trioctylphosphine oxide)

Toyoshima, Atsushi; Kasamatsu, Yoshitaka*; Tsukada, Kazuaki; Asai, Masato; Ishii, Yasuo; Tome, Hayato*; Nishinaka, Ichiro; Sato, Tetsuya; Nagame, Yuichiro; Sch$"a$del, M.; et al.

Journal of Nuclear and Radiochemical Sciences, 11(1), p.7 - 11, 2010/06

The extraction behavior of rutherfordium (Rf) into trioctylphosphine oxide (TOPO) from 2.0 - 7.0 M HCl solution was studied together with that of the homologues Zr and Hf. The extracted yields of Rf, Zr, and Hf increased with an increase of HCl concentration, and the sequence of their extraction was Zr $$>$$ Hf $$geq$$ Rf. It is suggested that the stability of the RfCl$$_{4}$$$$cdot$$2(TOPO) complex is lower than that of the corresponding species of the homologues.

Journal Articles

Anionic fluoro complex of element 105, Db

Kasamatsu, Yoshitaka*; Toyoshima, Atsushi; Asai, Masato; Tsukada, Kazuaki; Li, Z.; Ishii, Yasuo; Tome, Hayato*; Sato, Tetsuya; Kikuchi, Takahiro; Nishinaka, Ichiro; et al.

Chemistry Letters, 38(11), p.1084 - 1085, 2009/10

 Times Cited Count:14 Percentile:49.04(Chemistry, Multidisciplinary)

We report on the characteristic anion-exchange behavior of the superheavy element dubnium (Db) with atomic number Z = 105 in HF/HNO$$_{3}$$ solution at the fluoride ion concentration [F$$^{-}$$] = 0.003 M. The result clearly demonstrates that the fluoro complex formation of Db is significantly different from that of the group-5 homologue Ta in the 6th period of the periodic table while the behavior of Db is similar to that of the lighter homologue Nb in the 5th period.

Journal Articles

Oxidation of element 102, nobelium, with flow electrolytic column chromatography on an atom-at-a-time scale

Toyoshima, Atsushi; Kasamatsu, Yoshitaka*; Tsukada, Kazuaki; Asai, Masato; Kitatsuji, Yoshihiro; Ishii, Yasuo; Tome, Hayato; Nishinaka, Ichiro; Haba, Hiromitsu*; Oe, Kazuhiro*; et al.

Journal of the American Chemical Society, 131(26), p.9180 - 9181, 2009/07

 Times Cited Count:12 Percentile:52.7(Chemistry, Multidisciplinary)

We report here on the successful oxidation of element 102, nobelium (No), on an atom-at-a-time scale in 0.1 M $$alpha$$-hydroxyisobutyric acid ($$alpha$$-HIB) solution using newly developed flow electrolytic column chromatography. It is found that the most stable No$$^{2+}$$ is oxidized to No$$^{3+}$$ within 3 min and that the oxidized No complex with $$alpha$$-HIB holds the trivalent state in the column above the applied potential of 1.0 V.

JAEA Reports

Improvement of the protection devices for JT-60U LHRF antenna system

Suzuki, Sadaaki; Seki, Masami; Shinozaki, Shinichi; Sato, Fumiaki; Hiranai, Shinichi; Ishii, Kazuhiro*; Hasegawa, Koichi; Moriyama, Shinichi

JAEA-Technology 2007-055, 27 Pages, 2007/09


In the experiments featuring lower hybrid range of frequency (LHRF) system in JT-60U, carbon grills were attached to the plasma-facing part of the antenna in order to avoid the damage by the excessive heat load from the plasma. However some electric discharge traces were found there in the observation after the experiments. To avoid such discharges, improvements of the arc detector and the protection interlock by visible picture detection were tackled. In the arc detector, the amplification circuit was improved in order to obtain shorter response time and higher resolution of optical detection. Moreover, in visible picture detection, a new function of RF-on/off control utilizing PC image processing was added to distinguish the light of the arc from one of the plasma. This report summarizes improvement of the protection interlock device in a LHRF heating system.

JAEA Reports

Development of power measuring device of transmission type with dielectric for high power millimeter wave

Yokokura, Kenji; Moriyama, Shinichi; Hasegawa, Koichi; Suzuki, Sadaaki; Hiranai, Shinichi; Ishii, Kazuhiro*; Sato, Fumiaki

JAEA-Technology 2007-045, 22 Pages, 2007/07


A power measuring device using a dielectric disk for a high power millimeter waves is investigated. In the device, a high power wave is transmitted in a waveguide and then heats a dielectric installed in the waveguide. The transmitted power is estimated from the temperature rise of the dielectric disk. It is a new type of power measurement device, which is not sensitive to higher modes or change of their polarization in time. It also can measure the wide power range of kW to MW levels flexibly by choosing dielectric material proper to the power level as a detector. In the report, materials that have small dielectric loss for millimeter wave are chosen, and their properties of temperature rise and millimeter wave power capacity are estimated. On the basis of these results, design of the power measurement device and fabrication of its prototype are described for practical use in the electron cyclotron heating systems for the JT-60U and JT-60SA.

JAEA Reports

Power injection performance of the LH antenna tipped with carbon grills in JT-60U

Ishii, Kazuhiro; Seki, Masami; Shinozaki, Shinichi; Hasegawa, Koichi; Hiranai, Shinichi; Suzuki, Sadaaki; Sato, Fumiaki; Moriyama, Shinichi; Yokokura, Kenji

JAEA-Technology 2007-036, 30 Pages, 2007/07


The lower hybrid (LH) antenna in JT-60U has interaction with plasmas because it should be close to them in order to inject effectively radio frequency (RF) power into them. As a result, it has been a serious problem that the antenna mouth made of stainless steels was damaged due to excessive heat loads of plasmas and RF breakdowns. To solve the problem, a heat-resistant LH antenna was developed tipping carbon grills with fairly high heat resistance on the antenna mouth, and therefore reduction in damages on the mouth was expected. Power injection into plasmas was firstly performed with the heat-resistant antenna. RF conditioning was done carefully in the initial phase because RF breakdown due to outgassing from the grills might be occurred. After sufficient degassing was done through RF conditioning, RF power of about 1.6 MW $$times$$ 10 sec injection was successfully injected to plasmas. Moreover it was demonstrated that it had comparably high plasma current drive capability (about 1.6 $$times$$ 10$$^{19}$$ A/W/m$$^{2}$$), required as a current drive LH antenna.

Journal Articles

Conceptual design study and evaluation of advanced fuel fabrication systems in the feasibility study on commercialized FR fuel cycle in Japan

Namekawa, Takashi; Kawaguchi, Koichi; Koike, Kazuhiro; Haraguchi, Shingo; Ishii, Satoru

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10

New concepts of future fabrication system for low decontaminated transuranium (TRU) fuel was designed. It is essential to establish a remote fabrication system in the hot cell, because materials with high levels of radiation and high generation of heat are handled in the system. The configuration of the present systems including aspects related to economy was clarified through the conceptual design study. Technical feasibility of each concepts is follwiong. For oxide fuels, the simplified pelletizing method has a high technical feasibility for the process, and its expected practical use is possible at early stage, because this method is based on wealth results of a conventional method. The sphere-pack method has the advantage of lesser dispersion of the fine powder due to the use of solution and granule in the process. However this system will shoulder additional cost for the liquid waste treatment process due to need dispose of a large bulk of process liquid waste. The vipack method has the possibility of economical improvement if simplification of the process can be achieved. However this system has some problems for quality assurance etc. For the casting method of metal fuel, high economical efficiency is generally expected of small-scale facilities, although verification of fabrication of the TRU alloy slug is required. For nitride fuel, technology developments for N-15 enrichment and recycling, and nitride conversion process etc. In particular, for coated particle fuel fabrication, crucial technology developments are required on coating and assembly process.

JAEA Reports

Performance and experience of a 110 GHz gyrotron operation on the JT-60U ECH system

Takahashi, Masami*; Seki, Masami; Shimono, Mitsugu; Terakado, Masayuki; Igarashi, Koichi*; Ishii, Kazuhiro*; Kasugai, Atsushi

JAERI-Tech 2003-080, 27 Pages, 2003/11


The JT-60U electron cyclotron heating (ECH) system has been introduced to suppress MHD instabilities via a current profile control by local heating or current drive. The ECH system consists of four 1MW-110GHz gyrotrons, four 60m transmission lines composed of a corrugated waveguide with a diameter of 31.75mm and two steerable type mirror antennas. Recently, a gyrotron developed for ITER has realized high power in an extremely high frequency range of millimeter waves although there was no high power source around 110GHz ten years ago. Therefore, it requires many techniques to operate the gyrotoron. The oscillation conditions had to be found at output power 1MW by adjusting the magnetic field parameters and anode voltage after heater aging. Then conditioning of the gyrotoron was done, where the pulse length is gradually extended in order to operate for 1sec level of pulse length. Consequently, 1MW-5sec of the designed value was achieved and the ECH system with four gyrotrons successfully injected the millimeter wave energy of 10MJ into plasmas, which is the world record.

JAEA Reports

An Investigation of fuel and fission product behavior in rise-to-power test of HTTR, 2; Results up to 30 MW operation

Ueta, Shohei; Emori, Koichi; Tobita, Tsutomu*; Takahashi, Masashi*; Kuroha, Misao; Ishii, Taro*; Sawa, Kazuhiro

JAERI-Research 2003-025, 59 Pages, 2003/11


In the safety design requirements for the High Temperature Engineering Test Reactor (HTTR) fuel, it is determined that "the as-fabricated failure fraction shall be less than 0.2%" and "the additional failure fraction shall be small through the full service period". Therefore the failure fraction should be quantitatively evaluated during the HTTR operation. In order to measure the primary coolant activity, primary coolant radioactivity signals the in safety protection system, the fuel failure detection (FFD) system and the primary coolant sampling system are provided in the HTTR. The fuel and fission product behavior was evaluated based on measured data in the rise-to-power tests (1) to (4). The measured fractional releases are constant at 2$$times$$10$$^{-9}$$ up to 60% of the reactor power, and then increase to 7$$times$$10$$^{-9}$$ at full power operation. The prediction shows good agreement with the measured value. These results showed that the release mechanism varied from recoil to diffusion of the generated fission gas from the contaminated uranium in the fuel compact matrix.

JAEA Reports

Measures against the damage of the antenna mouth of JT-60U LHRF system

Ishii, Kazuhiro*; Seki, Masami; Shimono, Mitsugu; Terakado, Masayuki; Igarashi, Koichi*; Takahashi, Masami*

JAERI-Tech 2003-079, 22 Pages, 2003/10


In JT-60U, the study of current drive by radio-frequency (RF) waves in lower hybrid range of frequency (LHRF) has been done as one of research and development works aiming at steady state operation of tokamaks. The main subject of hardware and technology development in this study is to develop a high power LHRF antenna, the main component of the system. The LHRF antenna is set closely to plasma to efficiently inject RF power into it. The LHRF antenna normally receives heat loads from the plasma, and it is required to inject high RF power. Then, it has become a problem that the antenna mouth was melted by excessive heat loads from plasma or it was melted and deformed by RF discharges. As a counter measurement against this, the LHRF antenna has been conditioned to improve its stand-off voltage capability. Furthermore, by monitoring the temperature of the LHRF antenna, adjusting its position, developing a injection method of power modulation even for current drive, and setting an arc sensor which picks up the RF discharge, the damage of the antenna mouth has been suppressed.

JAEA Reports

Low-power and long-pulse test of a klystron of the JT-60U LHRF heating system

Shimono, Mitsugu; Seki, Masami; Terakado, Masayuki; Igarashi, Koichi*; Ishii, Kazuhiro*; Takahashi, Masami*; Shinozaki, Shinichi; Hiranai, Shinichi; Sato, Fumiaki*; Anno, Katsuto

JAERI-Tech 2003-075, 29 Pages, 2003/09


no abstracts in English

JAEA Reports

Operational experiences of the super conducting magnet for a gyrotron of the JT-60U ECH system

Igarashi, Koichi*; Seki, Masami; Shimono, Mitsugu; Terakado, Masayuki; Ishii, Kazuhiro*; Takahashi, Masami*

JAERI-Tech 2003-030, 40 Pages, 2003/03


The JT-60U electron cyclotron heating (ECH) system can heat plasmas locally and drive a plasma current with four 1 MW-5 sec gyrotrons. The super conducting magnets (SCM) are required for oscillation of the gyrotron at a working frequency of 110 GHz. The SCM provides a high magnetic field of 4.5T at the cavity inside the gyrotron. This SCM system is characterized by (1) operation without liquid Helium owing to a 4 K-refrigerator applied to the magnetic coils, (2) easy maintenance. Operational experiences about the SCM system through a long term experiment for a high power gyrotron are very valuable. According to those operational experiences, it is clarified the 4 K-refrigerator should be renewed in oder to keep low temperature of the SCM. It is also found that 200 hours or less are required for the super conducting condition ($$<$$5K) after long stopping time of the refrigerator up to 150 hours. This is useful information for making a plan about ECH experiments.

Journal Articles

Power control by changing anode voltage of a 1MW-gyrotron

Terakado, Masayuki; Shimono, Mitsugu; Igarashi, Koichi*; Takahashi, Masami*; Ishii, Kazuhiro*; Seki, Masami

Heisei-14-Nendo Tokyo Daigaku Sogo Gijutsu Kenkyukai Gijutsu Hokokushu, 3 Pages, 2003/03

no abstracts in English

Journal Articles

Operation results and improvements on JT-60 ECH system

Shimono, Mitsugu; Seki, Masami; Terakado, Masayuki; Igarashi, Koichi*; Ishii, Kazuhiro*; Kajiwara, Ken; Anno, Katsuto

NIFS-MEMO-36, p.382 - 385, 2002/06

no abstracts in English

Oral presentation

Feasibility study on commercialization of fast breeder reactor cycle systems; Exothermic influence evaluation in a low decontamination TRU fuel fabrication system, 2

Koike, Kazuhiro; Ohshima, Hiroyuki; Ishii, Satoru; Namekawa, Takashi; Tsuji, Nobumasa*; Hashimoto, Akihiko*

no journal, , 

no abstracts in English

Oral presentation

Development of power measurement for electron cyclotron heating system in JT-60U, 2

Moriyama, Shinichi; Yokokura, Kenji; Hasegawa, Koichi; Suzuki, Sadaaki; Hiranai, Shinichi; Ishii, Kazuhiro; Sato, Fumiaki; Tani, Takashi; Igarashi, Koichi; Shimono, Mitsugu; et al.

no journal, , 

no abstracts in English

Oral presentation

R&Ds of the LH antenna mouth made of carbon in JT-60U

Seki, Masami; Sawahata, Masayuki; Shinozaki, Shinichi; Hiranai, Shinichi; Suzuki, Sadaaki; Hasegawa, Koichi; Shimono, Mitsugu; Yokokura, Kenji; Ishii, Kazuhiro; Sato, Fumiaki; et al.

no journal, , 

no abstracts in English

Oral presentation

Improvement of the protection devices for JT-60 LH antenna system

Suzuki, Sadaaki; Hasegawa, Koichi; Shinozaki, Shinichi; Sato, Fumiaki; Hiranai, Shinichi; Ishii, Kazuhiro; Seki, Masami; Moriyama, Shinichi; Yokokura, Kenji

no journal, , 

no abstracts in English

42 (Records 1-20 displayed on this page)