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Journal Articles

Safety handling characteristics of high-level tritiated water

Hayashi, Takumi; Ito, Takeshi*; Kobayashi, Kazuhiro; Isobe, Kanetsugu; Nishi, Masataka

Fusion Engineering and Design, 81(8-14), p.1365 - 1369, 2006/03

 Times Cited Count:18 Percentile:18.18(Nuclear Science & Technology)

In a fusion reactor, high-level tritiated water of more than GBq/ml will be generated and stored temporally in the various areas. High level tritiated water decomposes by itself and generates hydrogen and oxygen, and becomes to tritiated hydrogen peroxide water, however, effective G-values from tritiated water are different from those obtained $$gamma$$-ray experiments in our previous report. Furthermore, tritiated water of about 250GBq/ml has been stored for several years safely and checked its characteristics. Using the above experiences, this paper summarizes safety requirements for storage of high-level tritiated water and discusses design issues of the safety storage system. Concerning gaseous species, storage tank should be maintained at negative pressure and purged periodically or constantly to dedicated tritium removal system. Specially, it is important that the G-value of high-level tritiated water is increasing with decreasing the tritium concentration. The pH and ORP (Oxidation Reduction Potential) of tritiated water have been also changed depending on the tritium concentration and maintained for more than several years in glass vessel. High-level tritiated water of more than GBq/ml was acid and became to be corrosive depending on the dissolved species. Large amount of tritiated water will be stored in the various tanks of stainless steel, therefore, it should be monitored so that the liquid situation is maintained not to be corrosive.

Journal Articles

Vapor species evolved from Li$$_{2}$$TiO$$_{3}$$ heated at high temperature under various conditions

Hoshino, Tsuyoshi; Yasumoto, Masaru*; Tsuchiya, Kunihiko; Hayashi, Kimio; Nishimura, Hidetoshi*; Suzuki, Akihiro*; Terai, Takayuki*

Fusion Engineering and Design, 81(1-7), p.555 - 559, 2006/02

 Times Cited Count:12 Percentile:29.89(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Design study of superconducting coils for the fusion DEMO plant at JAERI

Isono, Takaaki; Koizumi, Norikiyo; Okuno, Kiyoshi; Kurihara, Ryoichi; Nishio, Satoshi; Tobita, Kenji

Fusion Engineering and Design, 81(8-14), p.1257 - 1261, 2006/02

 Times Cited Count:4 Percentile:64.34(Nuclear Science & Technology)

In order to realize an economically competitive power generation system, generation of a higher field is required. Toroidal Field (TF) coils of fusion DEMO plant at JAERI are required to generate magnetic field of 16 to 20 T. To realize this high field, advanced superconducting materials, such as Nb$$_3$$Al and high temperature superconductor (HTS), are considered. HTS has enough performance in a 20-T field at 4 K, and a forced-cooled type HTS conductor using a silver alloy sheathed Bi-2212 round wire has been proposed. Required areas of superconductor, structure, stabilizer, coolant and insulator in the cross section of coil winding have been calculated. However, there are many technical issues to be solved, such as accurate temperature control during heat treatment in an atmosphere of oxygen. On the other hand, a large coil using Nb$$_3$$Al has been developed by JAERI, and major technology to fabricate a 16-T Nb$$_3$$Al coil was developed. Validity and issues of grading the winding area are discussed, and there is a possibility to increase a field up to around 17 T using the method.

Journal Articles

Design and development of EC H&CD antenna mirrors for ITER

Takahashi, Koji; Kobayashi, Noriyuki*; Kasugai, Atsushi; Sakamoto, Keishi

Fusion Engineering and Design, 81(1-7), p.281 - 287, 2006/02

 Times Cited Count:5 Percentile:58.37(Nuclear Science & Technology)

In the ITER, an EC H&CD steering antenna mirror was designed to reflect eight or nine 1MW-wave beams. The cross-section and thickness of the mirror are 250$$times$$360 mm$$^{2}$$ and 50mm, respectively. The thermal and stress analysis under the ITER condition show that the copper alloy(DSCu) mirror with stainless steel cooling tubes inside is considered acceptable. The EC H&CD antenna system for the ITER must have a dog-legged transmission lines so as to protect the diamond windows or superconducting magnets of a tokamak. A 90$$^{circ}$$ miter bend, which consists of waveguides and a reflection mirror, is required to make the structure. The mock-up of the mirror based on the ITER design was fabricated and the high power transmission experiment was carried out. The mm-wave transmission with power/pulse length 450kW/5.0sec, was demonstrated. The ohmic loss is estimated to be $$sim$$0.2%, which agrees with the calculation based on electrical resistivity of DSCu 2.0$$times$$10$$^{-8}$$$$Omega$$m.

Journal Articles

Neutron irradiation effect on mechanical properties of SS/SS HIP joint materials for ITER shielding blankets

Yamada, Hirokazu*; Sato, Satoshi; Mori, Kensuke*; Nagao, Yoshiharu; Takada, Fumiki; Kawamura, Hiroshi

Fusion Engineering and Design, 81(1-7), p.631 - 637, 2006/02

 Times Cited Count:1 Percentile:88.32(Nuclear Science & Technology)

This study estimated the neutron irradiation effect with 1.5 dpa on the mechanical properties of the SS/SS HIP joint materials jointed in the standard HIP joint condition. Results of this study showed that the HIP process in the standard HIP condition could make SS/SS HIP joint material of which tensile properties was equivalent to that of the SS base material. In addition, the effect of surface roughness at the HIP joint material on the mechanical properties of SS/SS HIP joint material was estimated.

Journal Articles

Evaluation of contact strength of Li$$_{2}$$TiO$$_{3}$$ pebbles with different diameters

Tsuchiya, Kunihiko; Kawamura, Hiroshi; Tanaka, Satoru*

Fusion Engineering and Design, 81(8-14), p.1065 - 1069, 2006/02

 Times Cited Count:8 Percentile:44.03(Nuclear Science & Technology)

no abstracts in English

Journal Articles

General properties on compatibility between Be-Ti alloy and SS 316LN

Tsuchiya, Kunihiko; Uchida, Munenori*; Kawamura, Hiroshi

Fusion Engineering and Design, 81(8-14), p.1057 - 1063, 2006/02

 Times Cited Count:5 Percentile:58.37(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Distinctive radiation durability of an ion exchange membrane in the SPE water electrolyzer for the ITER water detritiation system

Iwai, Yasunori; Yamanishi, Toshihiko; Isobe, Kanetsugu; Nishi, Masataka; Yagi, Toshiaki; Tamada, Masao

Fusion Engineering and Design, 81(1-7), p.815 - 820, 2006/02

 Times Cited Count:14 Percentile:25.29(Nuclear Science & Technology)

Solid-polymer-electrolyte (SPE) water electrolysis is attractive in electrolytic process of water detritiation system (WDS) in fusion reactors because it can electrolyze liquid waste directly, but radioactive durability of its ion exchange membrane is a key point. Radioactive durability of Nafion, a typical commercial ion exchange membrane, was experimentally investigated using Co-60 irradiation facility and electron beam irradiation facility at Takasaki Radiation Chemistry Research Establishment of JAERI. Nafion is composed of PTFE (Polytetrafluoroethylene) main chain. However the degradation of its mechanical strength by irradiation was significantly distinguished from that of PTFE and no serious damage was observed for its ion exchange capacity up to 530 kGy, the requirement of ITER. Atmospheric effects such as soaking and oxygen on degrading behaviors were discussed from the viewpoint of radical reaction mechanism. Dependencies of operating temperature and radioactive source are also demonstrated in detail.

Journal Articles

Ion and neutron beam analyses of hydrogen isotopes

Kubota, Naoyoshi; Ochiai, Kentaro; Kutsukake, Chuzo; Kondo, Keitaro*; Shu, Wataru; Nishi, Masataka; Nishitani, Takeo

Fusion Engineering and Design, 81(1-7), p.227 - 231, 2006/02

 Times Cited Count:5 Percentile:58.37(Nuclear Science & Technology)

Hydrogen isotopes play important roles in the fuel recycling, the plasma condition etc. at the surface region of plasma facing components. The Fusion Neutronics Source (FNS) of Japan Atomic Energy Research Institute has started microanalysis studies for fusion components since 2002 by applying the beam analyses. In this study, we have measured tritium depth profiles of TFTR tiles exposed to the deuterium-tritium plasma to reveal the hydrogen isotope behavior at the surface region using some microscopic techniques for material analyses at FNS. As the result of the deuteron nuclear reaction analysis, four kinds of elements; deuterium, tritium, lithium-6 and lithium-7, were identified from the energy spectra. Using the spectra, depth profiles of each element were also calculated. The tritium profile had a peak at 0.5 micron, whereas the deuterium and lithium profiles were uniform from the surface to 1.0 micron depth. In addition, the surface region of the TFTR tile has retained the tritium more than one order of magnitude in the bulk.

Journal Articles

Study on tritium accountancy in fusion DEMO plant at JAERI

Nishi, Masataka; Yamanishi, Toshihiko; Hayashi, Takumi; DEMO Plant Design Team

Fusion Engineering and Design, 81(1-7), p.745 - 751, 2006/02

 Times Cited Count:27 Percentile:10.36(Nuclear Science & Technology)

The fusion DEMO plant is under designing at JAERI as a fusion machine following ITER, and it is designed with long-term steady operation and tritium breeding blanket in which more tritium is produced than consumption. Therefore, proper tritium accountancy control concept should be discussed and developed for its safety and operation. From the viewpoint of regulation for the radioisotopes, at first, it will be suitable to divide facilities of the fusion DEMO plant into three accountancy control blocks, that is, (1) the contaminated waste management facility, (2) the long term tritium storage facility, and (3) the fuel processing plant. In each block, tritium amount of receipt and delivery should be carefully accounted. The fuel processing plant involves tritium production in the blanket, therefore proper accounting method for produced tritium should be established. Furthermore, dynamic accountancy is indispensable to the fuel processing plant to monitor tritium inventory distribution for safety and optimum system control in addition to the accountancy under regulation.

Journal Articles

Engineering design and control scenario for steady-state high-beta operation in national centralized tokamak

Tsuchiya, Katsuhiko; Akiba, Masato; Azechi, Hiroshi*; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hashizume, Hidetoshi*; Hayashi, Nobuhiko; Horiike, Hiroshi*; et al.

Fusion Engineering and Design, 81(8-14), p.1599 - 1605, 2006/02

 Times Cited Count:1 Percentile:88.32(Nuclear Science & Technology)

no abstracts in English

Journal Articles

A Design study for tritium recovery system from cooling water of a fusion power plant

Yamanishi, Toshihiko; Iwai, Yasunori; Kawamura, Yoshinori; Nishi, Masataka

Fusion Engineering and Design, 81(1-7), p.797 - 802, 2006/02

no abstracts in English

Journal Articles

Influence of blistering on deuterium retention in tungsten irradiated by high flux deuterium 10-100eV plasmas

Luo, G.; Shu, Wataru; Nishi, Masataka

Fusion Engineering and Design, 81(8-14), p.957 - 962, 2006/02

 Times Cited Count:56 Percentile:2.56(Nuclear Science & Technology)

The influence of blistering on deuterium retention in W was investigated using the newly established plasma generator with controllable incident energies ranging from 100 eV down to around 10 eV and incident flux of 1$$times$$10$$^{22}$$ D/m$$^{2}$$/s. The retention in the irradiated samples was measured using a thermal desorption spectrometer (TDS) at a ramping rate of 5 $$^{circ}$$C/s. The results indicate that only one peak appears in each spectrum, with the peak temperatures ranging from 500 until 850 $$^{circ}$$C, much higher than those from the trapping sites like vacancies, grain boundaries, dislocation loops, or impurities, implying probably a direct origin from the molecules existing inside blisters, voids/bubbles. Significant decrease in the retention at a certain incident fluence after blister appearance was observed and attributed to rupturing of the blisters, consistent with the limited size and increasing number of the blisters with increasing the incident fluence, as observed by means of SEM.

Journal Articles

Monitoring of tritium in diluted gases by detecting bremsstrahlung X-rays

Shu, Wataru; Matsuyama, Masao*; Suzuki, Takumi; Nishi, Masataka

Fusion Engineering and Design, 81(1-7), p.803 - 808, 2006/02

 Times Cited Count:9 Percentile:39.77(Nuclear Science & Technology)

In this work, the counting rate of bremsstrahlung X-rays was measured against the tritium partial pressure in two mixed gases diluted with helium or hydrogen. Subsequently, the counting rate was also measured against total pressure for T$$_{2}$$-He mixture at a constant tritium partial pressure of 93 Pa or 1.3 kPa. For both mixtures, the counting rate of bremsstrahlung X-rays decreased linearly with the decreasing tritium partial pressure when the total pressure is smaller than about 10 kPa. At higher pressures, the deviation from the linear relationship appeared due to absorption of beta-particles in the gas phase, and this can be decreased by some commercially available arrangements. On the other hand, the counting rate of bremsstrahlung X-rays depended only upon the tritium partial pressure when absorption of beta-particles in the gas phase is negligibly small. The results obtained show that this method of tritium monitoring is very promising for the fuel processing system of fusion reactors, especially for tritium recovery system of breeding blankets.

Journal Articles

Case study on tritium inventory in the fusion DEMO plant at JAERI

Nakamura, Hirofumi; Sakurai, Shinji; Suzuki, Satoshi; Hayashi, Takumi; Enoeda, Mikio; Tobita, Kenji; DEMO Plant Design Team

Fusion Engineering and Design, 81(8-14), p.1339 - 1345, 2006/02

 Times Cited Count:32 Percentile:8.31(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Characterization of JT-60U exhaust gas during experimental operation

Isobe, Kanetsugu; Nakamura, Hirofumi; Kaminaga, Atsushi; Tsuzuki, Kazuhiro; Higashijima, Satoru; Nishi, Masataka; Kobayashi, Yasunori*; Konishi, Satoshi*

Fusion Engineering and Design, 81(1-7), p.827 - 832, 2006/02

 Times Cited Count:7 Percentile:48.39(Nuclear Science & Technology)

Exhaust gas from JT-60U during experimental operation has been measured with Gas Chromatography (GC), and the gas exhaust characteristic from JT-60U on plasma discharge conditions has been investigated during the JT-60U experimental campaign in 2003-2004. During experimental operation of JT-60U, hydrogen isotope concentration strongly depended on the type of discharges such as high performance, long pulse and so on. On the other hand, impurity species, such as helium, hydrocarbon and carbon oxide, were detected during plasma discharges occasionally. During the experimental operation, plasma disruption remarkably tended to produce high concentration impurities. Glow discharge and Taylor discharge for wall conditioning also produced impurities. In the case of normal plasma, impurity was detected and high performance plasma, such as high $$beta$$ plasma, tended to produce high concentration impurities. This result indicated that impurities concentration might be higher in the case of normal plasma in ITER, because of its high performance.

Journal Articles

Feasibility study on the blanket tritium recovery system using the palladium membrane diffuser

Kawamura, Yoshinori; Enoeda, Mikio; Yamanishi, Toshihiko; Nishi, Masataka

Fusion Engineering and Design, 81(1-7), p.809 - 814, 2006/02

 Times Cited Count:13 Percentile:27.36(Nuclear Science & Technology)

Tritium bred in the solid breeder blanket of a fusion reactor is extracted by passing of a helium sweep gas. Tritium is separated from sweep gas at the blanket tritium recovery system. Palladium membrane diffuser is one of the applicable processes for the blanket tritium recovery system. It is usually applied for hydrogen purification system such as TEP in ITER. However, it has been reported that the rate controlling step changes at lower hydrogen pressure such as the blanket sweep gas condition, and discussion about application for the blanket sweep gas condition is not enough. Recently, conceptual design of the demonstration reactor, named "DEMO2001", has been proposed from JAERI. In this report, the application of the Pd diffuser for the blanket sweep gas condition is discussed based on the condition of DEMO 2001.

Journal Articles

Sorption and desorption of tritiated water on four kinds of materials for ITER

Kobayashi, Kazuhiro; Hayashi, Takumi; Nishi, Masataka; Oya, Yasuhisa*; Okuno, Kenji*

Fusion Engineering and Design, 81(8-14), p.1379 - 1384, 2006/02

 Times Cited Count:5 Percentile:58.37(Nuclear Science & Technology)

In facilities of ITER, various construction materials are possibly exposed by tritium during periodical maintenances and an accident. It is required to establish the effective surface decontamination methods for the above construction materials of ITER. In tritium decontaminating, so-called "soaking" effect is important. This effect is based on sorption of tritiated water on the materials and subsequent desorption from them. In order to obtain and summarize data on the amount of tritium adsorption on the various materials, a series of tritiated water vapor exposure experiments have been carried out as a function of time. The amounts of tritium adsorption on the materials saturated almost within the period from several weeks to 1 month. The adsorption rate of the epoxy was found to be the largest. In the exposure time less than 2 hrs, the adsorption coefficients for the examined materials were found to be in the same order as those reported by F.Ono. It will be also discussed from viewpoint of kinetics for adsorption and desorption.

Journal Articles

Neutronics design of the low aspect ratio tokamak reactor, VECTOR

Nishitani, Takeo; Yamauchi, Michinori*; Nishio, Satoshi; Wada, Masayuki*

Fusion Engineering and Design, 81(8-14), p.1245 - 1249, 2006/02

 Times Cited Count:13 Percentile:27.36(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Development of a new fusion power monitor based on activation of flowing water

Verzilov, Y. M.; Nishitani, Takeo; Ochiai, Kentaro; Kutsukake, Chuzo; Abe, Yuichi

Fusion Engineering and Design, 81(8-14), p.1477 - 1483, 2006/02

 Times Cited Count:1 Percentile:88.32(Nuclear Science & Technology)

no abstracts in English

43 (Records 1-20 displayed on this page)