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Kawaguchi, Munemichi; Miyahara, Shinya; Uno, Masayoshi*
Journal of Nuclear Science and Technology, 56(6), p.513 - 520, 2019/06
This study revealed melting points and thermal conductivities of four samples generated by sodium-concrete reaction (SCR). We prepared the samples using two methods such as firing mixtures of sodium and grinded concrete powder, and sampling depositions after the SCR experiments. In the former, the mixing ratios were determined from the past experiment. The latter simulated the more realistic conditions such as the temperature history and the distribution of Na and concrete. The thermogravimetry-differential thermal analyzer (TG-DTA) measurement showed the melting points were 865-942
C, but those of the samples containing metallic Na couldn't be clarified. In the two more realistic samples, the compression moldings in a furnace were observed. The observation revealed the softening temperature was 800-840C and the melting point was 840-850C, which was 10-20C lower than the TG-DTA results. The thermodynamics calculation of FactSage 7.2 revealed the temperature of the onset of melting was caused by melting of the some components such as Na
SiO
and/or Na
SiO. Moreover, the thermal conductivity was 
=1-3W/m-K, which was comparable to xNaO-1-xSiO (x=0.5, 0.33, 0.25), and those at 700C were explained by the equation of 
.
Ikusawa, Yoshihisa; Morimoto, Kyoichi; Kato, Masato; Saito, Kosuke; Uno, Masayoshi*
Nuclear Technology, 205(3), p.474 - 485, 2019/03
Percentile：100(Nuclear Science & Technology)This study evaluated the effects of plutonium content and self-irradiation on the thermal conductivity of mixed-oxide (MOX) fuel. Samples of UO fuel and various MOX fuels were tested. The MOX fuels had a range of plutonium contents, and some samples were stored for 20 years. The thermal conductivity of these samples was determined from thermal diffusivity measurements taken via laser flash analysis. Although the thermal conductivity decreased with increasing plutonium content, this effect was slight. The effect of self-irradiation was investigated using the stored samples. The reduction in thermal conductivity caused by self-irradiation depended on the plutonium content, its isotopic composition, and storage time. The reduction in thermal conductivity over 20 years' storage can be predicted from the change of lattice parameter. In addition, the decrease in thermal conductivity caused by self-irradiation was recovered with heat treatment, and recovered almost completely at temperatures over 1200 K. From these evaluation results, we formulated an equation for thermal conductivity that is based on the classical phonon-transport model. This equation can predict the thermal conductivity of MOX fuel thermal conductivity by accounting for the influences of plutonium content and self-irradiation.
Takamatsu, Kuniyoshi; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*
Annals of Nuclear Energy, 122, p.201 - 206, 2018/12
Percentile：100(Nuclear Science & Technology)A RCCS having passive safety features through radiation and natural convection was proposed. The RCCS design consists of two continuous closed regions: an ex-reactor pressure vessel region and a cooling region with a heat-transfer surface to ambient air. The RCCS uses a novel shape to remove efficiently the heat released from the RPV through as much radiation as possible. Employing air as the working fluid and ambient air as the ultimate heat sink, the RCCS design can strongly reduce the possibility of losing the working fluid and the heat sink for decay-heat-removal. This study addresses an improvement of heat-removal capability using heat conduction on the RCCS. As a result, a heat flux removed by the RCCS could be doubled; therefore, it is possible to halve the height of the RCCS or increase the thermal reactor power.
Hosomi, Seisuke*; Akashi, Tomoyasu*; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*; Takamatsu, Kuniyoshi
Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 7 Pages, 2018/11
A new RCCS with passive safety features consists of two continuous closed regions. One is a region surrounding RPV. The other is a cooling region with heat transferred to the ambient air. The new RCCS needs no electrical or mechanical driving devices. We started experiment research with using a scaled-down test section. Three experimental cases under different emissivity conditions were performed. We used Monte Carlo method to evaluate the contribution of radiation to the total heat released from the heater. As a result, after the heater wall was painted black, the contribution of radiation to the total heat could be increased to about 60%. A high emissivity of RPV surface is very effective to remove more heat from the reactor. A high emissivity of the cooling part wall is also effective because it not only increases the radiation emitted to the ambient air, but also may increase the temperature difference among the walls and enhance the convection heat transfer in the RCCS.
Nishi, Tsuyoshi; Nakajima, Kunihisa; Takano, Masahide; Kurata, Masaki; Arita, Yuji*
Journal of Nuclear Materials, 464, p.270 - 274, 2015/09
Percentile：100(Materials Science, Multidisciplinary)no abstracts in English
Aso, Tomokazu; Monde, Masanori*; Sato, Hiroshi; Hino, Ryutaro; Tatsumoto, Hideki; Kato, Takashi
Nippon Genshiryoku Gakkai Wabun Rombunshi, 5(3), p.179 - 189, 2006/09
no abstracts in English
Aso, Tomokazu; Monde, Masanori*; Sato, Hiroshi; Tatsumoto, Hideki; Kato, Takashi; Ikeda, Yujiro
LA-UR-06-3904, Vol.2, p.385 - 394, 2006/06
no abstracts in English
Ishiyama, Shintaro
Nippon Genshiryoku Gakkai Wabun Rombunshi, 3(3), p.288 - 297, 2004/09
Target plate mode of divertor device for fusion reactor was fabricated using low activated and light material, Si/xSiC metal matrix composite and high strength and thermal conductive SiC. This model was exposed under 5MW/m
30sec high heat flux and showed very good cooling performance and no damage was found after this test.
TiO added with TiOHoshino, Tsuyoshi; Kobayashi, Takeshi*; Nashimoto, Makoto*; Kawamura, Hiroshi; Dokiya, Masayuki*; Terai, Takayuki*; Yamawaki, Michio*; Takahashi, Yoichi*
JAERI-Conf 2004-012, p.140 - 147, 2004/07
no abstracts in English
TiOHoshino, Tsuyoshi; Kobayashi, Takeshi*; Nashimoto, Makoto*; Kawamura, Hiroshi; Terai, Takayuki*; Yamawaki, Michio*; Takahashi, Yoichi*
Journal of the Ceramic Society of Japan, Supplement, Vol.112, No.1 (CD-ROM), p.S354 - S357, 2004/05
no abstracts in English
Enoeda, Mikio; Kosaku, Yasuo; Hatano, Toshihisa; Kuroda, Toshimasa*; Miki, Nobuharu*; Homma, Takashi; Akiba, Masato; Konishi, Satoshi; Nakamura, Hirofumi; Kawamura, Yoshinori; et al.
Nuclear Fusion, 43(12), p.1837 - 1844, 2003/12
Times Cited Count：85 Percentile：5.79(Physics, Fluids & Plasmas)no abstracts in English
TiUchida, Munenori*; Ishitsuka, Etsuo; Kawamura, Hiroshi
Fusion Engineering and Design, 69(1-4), p.499 - 503, 2003/09
Times Cited Count：16 Percentile：23.69no abstracts in English
TiO pebble bed for a demo blanketHatano, Toshihisa; Enoeda, Mikio; Suzuki, Satoshi; Kosaku, Yasuo; Akiba, Masato
Fusion Science and Technology, 44(1), p.94 - 98, 2003/07
Times Cited Count：14 Percentile：25.5(Nuclear Science & Technology)no abstracts in English
Shirai, Hiroshi
Purazuma, Kaku Yugo Gakkai-Shi, 79(7), p.691 - 705, 2003/07
Methods for heat transport analysis and heat transport simulation in toroidal plasmas are summarized on the basis of energy balance equation. Joule heating, NBI heating, RF heating and 
heating are briefly explained. Among the energy loss mechanism, the conduction loss and the radiation loss dominate in the core plasma region and the peripheral region, respectively. In tokamaks, the anomalous transport caused by microturbulence is much larger than the neoclassical transport. The other mechanisms of enhanced transport, the sawtooth oscillation and the magnetic island formation, are also shown.
Shiina, Yasuaki; Inagaki, Terumi*
Nippon Kikai Gakkai Rombunshu, B, 69(681), p.1233 - 1241, 2003/05
In order to reduce phase change time in latent heat technology, improvement of effective thermal conductivity of heat storage unit would be one of the techniques. Effect of effective thermal conductivity on melting time are studied analytically of circular composite heat storage capsules made by immersing phase change materials (PCM) into porous metals. Numerical and approximate analysis were made with the consideration of uniform and non-uniform heat transfer coefficients around the cylindrical surface. Four PCMs (HO,Octadecane, LiCO, NaCl) and three metals (copper, aluminum and carbon steel) were selected specific materials. Porosity of the metals were restricted larger than 0.9 in order to lessen decrease in latent heat. Results show that reduction in melting time was obtained for the above PCMs, especially for low conductivity PCMs. Melting time obtained by approximate analysis agrees well with numerical analysis. High Nusselt number and high thermal conductivity of heat transfer fluid would be more effective to reduce phase change time.
Uemura, Takuya*; Takeda, Tetsuaki; Ichimiya, Koichi*
Nippon Kikai Gakkai Yamanashi Koenkai Koen Rombunshu (020-4), p.49 - 50, 2002/10
A heat transfer experiment was performed using a horizontal circular tube to obtain the heat transfer and fluid flow characteristics in the tube inserted copper wire. From the results obtained in this experiment, it was found that an amount of heat removal in the tube with copper wire inserts increased about 20% comparing with a tube having a smooth wall. A heat transfer coefficient of the tube inserted copper wire also increased 30% to 50% under the constant pumping power condition.
Urano, Hajime*; Kamada, Yutaka; Shirai, Hiroshi; Takizuka, Tomonori; Kubo, Hirotaka; Takenaga, Hidenobu; Miura, Yukitoshi; Hatae, Takaki; Fukuda, Takeshi
Plasma Physics and Controlled Fusion, 44(5A), p.A437 - A443, 2002/05
Times Cited Count：15 Percentile：49.2(Physics, Fluids & Plasmas)no abstracts in English
Nakamura, Jinichi
Saishin Kaku Nenryo Kogaku; Kodoka No Genjo To Tembo, p.93 - 98, 2001/06
no abstracts in English
Suzuki, Motoe
Saishin Kaku Nenryo Kogaku; Kodoka No Genjo To Tembo, p.131 - 140, 2001/06
no abstracts in English
Enoeda, Mikio; Ohara, Yoshihiro; Roux, N.*; Ying, A.*; Pizza, J.*; Malang, J.*
Fusion Technology, 39(No.2 Part.2), p.612 - 616, 2001/03
no abstracts in English
