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Journal Articles

Penetration behavior of water solution containing radioactive species into dried concrete/mortar and epoxy resin materials

Sato, Isamu; Maeda, Koji; Suto, Mitsuo; Osaka, Masahiko; Usuki, Toshiyuki; Koyama, Shinichi

Journal of Nuclear Science and Technology, 52(4), p.580 - 587, 2015/04

 Times Cited Count:5 Percentile:45.73(Nuclear Science & Technology)

Penetration behavior of radionuclides such as $$^{137}$$Cs into dried concrete material, dried mortar material and epoxy paint for a few dozen days was observed using a solution containing fission products extracted from irradiated fuels to obtain fundamental information on the radionuclide penetration rate and depth. Hardly any radionuclides could penetrate into the epoxy paint. The radionuclide solution penetrated into concrete and mortar materials to a depth of a few millimeters for a few dozen days. The penetration behavior observed near the surface of concrete and mortar materials was similar to the diffusion of nuclides in media such as water-saturated concrete, bentonite and cement materials.

JAEA Reports

Penetration behavior of solution containing radioactive nuclides into floor and wall materials

Usuki, Toshiyuki; Sato, Isamu; Suto, Mitsuo; Maeda, Koji; Osaka, Masahiko; Koyama, Shinichi; Tokoro, Daishiro*; Sekioka, Ken*; Ishigamori, Toshio*

JAEA-Testing 2014-001, 29 Pages, 2014/05

JAEA-Testing-2014-001.pdf:5.33MB

The penetration tests with solution containing radioactive nuclides were experimented to understand basic data for floor and wall materials of Fukushima Daiichi reactor buildings. The solution prepared from irradiated fuels was used as solution containing radioactive nuclides. The solution was applied to surface of epoxy paint, dried concrete and mortar used as specimens. Dose-rate profiles of direction of depth were given by radiation measurement and grinding of the specimens. The penetrations of radioactive nuclides for epoxy paint specimens were not clearly observed and the penetration depths would be within 0.4 mm. The penetrations of radioactive nuclides for dried concrete specimens proceeded. The penetration rates were substantially decreased when 16 days have elapsed from start. The dose rates of penetrated dried concrete specimens were reduced to background by grinding-2.0 mm. $$gamma$$-ray spectrometry measurement showed that penetration behavior of near surface concrete are different among nuclides and the penetration behavior of radioactive nuclides into dried concrete and mortar materials through solution is similar to migration behavior of ions into those water-saturated materials.

Journal Articles

MgO-based inert matrix fuels for a minor actinides recycling in a fast reactor cycle

Miwa, Shuhei; Osaka, Masahiko; Usuki, Toshiyuki; Sato, Isamu; Tanaka, Kosuke; Hirosawa, Takashi; Yoshimochi, Hiroshi; Onose, Shoji

Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 8 Pages, 2011/12

A new fast reactor (FR) cycle concept was previously proposed that incorporates MgO-based inert matrix fuels (IMFs) containing minor actinides harmonious with the existing FR cycle technologies. A basic study of MgO-based IMFs was made regarding their fabrication, characterization and reprocessing in terms of applicability to existing FR cycle technology. It was concluded from these basic investigations of MgO-based IMFs that the existing FR cycle technologies can be applied to those for MgO-based IMFs, and the basic technologies of MgO-based IMFs containing minor actinides harmonious with the existing FR cycle technologies were established.

Journal Articles

Reformation of hazardous wastes into useful supporting materials for fast reactor fuels

Osaka, Masahiko; Miwa, Shuhei; Tanaka, Kosuke; Akutsu, Yoko; Ikeda, Kaoru*; Mimura, Hitoshi*; Suzuki, Tatsuya*; Usuki, Toshiyuki; Yano, Toyohiko*

Annals of Nuclear Energy, 38(12), p.2661 - 2666, 2011/10

 Times Cited Count:2 Percentile:78.02(Nuclear Science & Technology)

Novel concepts for effective utilization of molybdenum (Mo) from nuclear waste and magnesium silicates from hazardous asbestos wastes are proposed. A fast reactor cycle scheme that incorporates each material is described in the present paper. Basic studies on some fundamental technologies for the present cycle are given. Basic separation aspects for Mo by using LIX63 micro capsules and tertiary pyridine resin were investigated. A simple chemical synthesis route for Mo precursor powder from Mo containing HNO$$_{3}$$ solution was tested. Effects of impurities in recovered Mo on sintering behavior were experimentally investigated.

Journal Articles

Fabrication and characterization of silicon nitride-based inert matrix fuels sintered with magnesium silicates

Usuki, Toshiyuki; Yoshida, Katsumi*; Yano, Toyohiko*; Miwa, Shuhei; Osaka, Masahiko

Progress in Nuclear Energy, 53(7), p.1078 - 1081, 2011/09

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

The effects of sintering additives of magnesium silicates, i.e. enstatite (MgSiO$$_{3}$$), steatite (MgSiO$$_{3}$$) and forsterite (Mg$$_{2}$$SiO$$_{4}$$), on the fabrication properties and characteristics of the silicon nitride ceramics based inert matrix fuels were experimentally investigated. CeO$$_{2}$$ was selected as simulating element of AmO$$_{2}$$. Sintered pellets were characterized in term of their densities, thermal conductivities and solubility to nitric acid. The densifications of sintered bodies were enhanced by using additives of magnesium silicates at relative low sintering temperature. The relative density of silicon nitride ceramics based inert matrix fuels with forsterite were achieved above 90% at 1723 K. The thermal conductivities of silicon nitride ceramics based inert matrix fuels varied according to sintering temperature, and those sintered at 1923 K were above 34 W/m K. The grain boundary phases in Silicon nitride ceramics based inert matrix fuels found to be dissolved into HNO$$_{3}$$.

Journal Articles

Densification of magnesia-based inert matrix fuels using asbestos waste-derived materials as a sintering additive

Miwa, Shuhei; Osaka, Masahiko; Usuki, Toshiyuki; Yano, Toyohiko*

Progress in Nuclear Energy, 53(7), p.1045 - 1049, 2011/09

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

We proposed a new concept for densification of minor actinides-containing inert matrix fuels by using asbestos waste-derived materials for the effective utilization of resources and protection of public safety. In this concept, magnesium silicates, which are mainly generated by the decomposition of asbestos in low temperature heat-treatment, are used as a sintering additive for the achievement of high density of magnesia-based inert matrix fuels at relatively low sintering temperature. In this study, preliminary fabrication tests of magnesia-based inert matrix fuels with magnesium silicates were carried out by using cerium oxides as a representative of minor actinides oxides.

Journal Articles

Structural basis for the fast phase change of Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$; Ring statistics analogy between the crystal and amorphous states

Kohara, Shinji*; Kato, Kenichi*; Kimura, Shigeru*; Tanaka, Hitoshi*; Usuki, Takeshi*; Suzuya, Kentaro; Tanaka, Hiroshi*; Moritomo, Yutaka*; Matsunaga, Toshiyuki*; Yamada, Noboru*; et al.

Applied Physics Letters, 89(20), p.201910_1 - 201910_3, 2006/11

 Times Cited Count:163 Percentile:2.4(Physics, Applied)

The three-dimensional atomic configuration of amorphous Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$ were derived by reverse Monte Carlo simulation with synchrotron-radiation X-ray diffraction data. The authors found that amorphous Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$ can be regarded as "even-numbered ring structure", because the ring statistics is dominated by four- and six-fold rings analogous to the crystal phase. On the other hand, the formation of Ge-Ge homopolar bonds in amorphous GeTe constructs both odd- and even-numbered rings. They believe that the unusual ring statistics of amorphous Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$ is the key for the fast crystallization speed of the material.

Oral presentation

Densification of nuclear fuel pellets using asbestos waste as a sintering additive

Miwa, Shuhei; Osaka, Masahiko; Usuki, Toshiyuki*; Yano, Toyohiko*

no journal, , 

no abstracts in English

Oral presentation

Sintering and characterization of silicon nitride ceramics as inert matrix with magnesium silicates

Usuki, Toshiyuki*; Yoshida, Katsumi*; Imai, Masamitsu*; Yano, Toyohiko*; Miwa, Shuhei; Osaka, Masahiko

no journal, , 

no abstracts in English

Oral presentation

Sintering and characterization of silicon nitride ceramics as inert matrix with magnesium silicates

Usuki, Toshiyuki; Yoshida, Katsumi*; Yano, Toyohiko*; Miwa, Shuhei; Osaka, Masahiko

no journal, , 

Minor actinides (MA) have lasting radio-toxicity. One of the possible ways to reduce radio-toxicity is transmutation of MA using nuclear reactors. Inert matrix (IM) is applied to host material for MA in transmutation. Silicon nitride (Si$$_{3}$$N$$_{4}$$) ceramics considered to be a candidate material of IM since it has a high thermal conductivity and shows good resistance to neutron irradiation. In this study, We proposed fabrication of silicon nitride ceramics based IMFs with Ce as simulating element and with magnesium silicates, i.e. enstatite (MgSiO$$_{3}$$), steatite (MgSiO$$_{3}$$) and forsterite (Mg$$_{2}$$SiO$$_{4}$$), as additives. The sintered densities of Si$$_{3}$$N$$_{4}$$-based IMFs with forsterite was above 96 % theoretical 1723 K. Furthermore, The thermal conductivities of IMFs sintered at 1923 K were above 34 W/mK.

Oral presentation

Thermal conductivity of MgO-based inert matrix fuels

Miwa, Shuhei; Usuki, Toshiyuki; Sato, Isamu; Hirosawa, Takashi; Tanaka, Kosuke; Osaka, Masahiko; Seki, Takayuki*; Kashimura, Naoki*

no journal, , 

no abstracts in English

Oral presentation

Thermal conductivity of inert matrix fuels using the asbestos waste-derived ceramics as a sintering additive

Miwa, Shuhei; Usuki, Toshiyuki; Sato, Isamu; Hirosawa, Takashi; Tanaka, Kosuke; Osaka, Masahiko; Seki, Takayuki*

no journal, , 

Thermal conductivies of MgO-based inert matrix fuels containing PuO$$_{2}$$ using the asbestos waste-derived ceramics as a sintering additive were experimentally investigated. Thermal diffusivities of fuels were measured by laser flush method. The effects of the MgO-SiO$$_{2}$$ compound additives addition on the thermal conductivity were discussed.

Oral presentation

Decontamination experiment for floor of Fukushima Dai-ichi Reactor Buildings, 2; Penetration behavior of simulated-contaminated water into floor and wall materials

Usuki, Toshiyuki; Sato, Isamu; Kanayama, Fumihiko; Suto, Mitsuo; Maeda, Koji; Koyama, Shinichi; Kawatsuma, Shinji; Fukushima, Mineo; Tokoro, Daishiro*; Sekioka, Ken*; et al.

no journal, , 

no abstracts in English

Oral presentation

Penetration behavior of a solution containing radioactive nuclides into concrete and epoxy resin paint

Usuki, Toshiyuki; Sato, Isamu; Kanayama, Fumihiko; Suto, Mitsuo; Maeda, Koji; Koyama, Shinichi; Kawatsuma, Shinji; Fukushima, Mineo; Tokoro, Daishiro*; Sekioka, Ken*; et al.

no journal, , 

no abstracts in English

Oral presentation

Training of radioactive substances and radiation for young educators, 2; The Aim and effect of on-site training using the hot laboratory

Isozaki, Ryosuke; Katsuyama, Kozo; Tanaka, Kosuke; Sato, Isamu; Usuki, Toshiyuki; Sekio, Yoshihiro; Hayashi, Takehiro; Tokoro, Daishiro*

no journal, , 

no abstracts in English

15 (Records 1-15 displayed on this page)
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