[en] In 1972, Nuclear Fuels Divisions of Sumitomo and Furukawa Electric Industries merged and became a subsidiary of Sumitomo and Furukawa Industries which is now called Nuclear Fuel Industries, Ltd. We design and manufacture various kinds of nuclear fuels. As for research reactor fuel, we began our development activities in 1956. Since then we have spent over 2 million dollars for development of nuclear fuels and plant facilities including complete manufacturing and testing capabilities. Now we are the only supplier of the research reactor fuel in Japan. Our fabrication process starts with the melting, alloying, and casting of U-Al. The uranium billets are prepared by foreign fabricators. The uranium content varies from 13 to 22 wt % according to the purchaser's specifications. In making fuel plates, the picture frame method is applied. In this case, our original procedure is sufficiently effective in avoiding dogboning. The plates are finished by hot and cold roll milling and inspected dimensionally, metallurgically, and mechanically, and at the same time the blister test and X-ray radiographic tests are performed. Fuel elements are assembled by rolling flat or curved plates into side plate grooves and end-fit welding. Finished elements are tested dimensionally and hydraulically. Nominal losses during operation are less than 1% of the uranium metal. Our present capacity licensed by the Japanese Government is approximately 950 fuel elements a year. About 35 employees including engineers are engaged in development and manufacturing of fuels. Owing to the small limited demand of the research reactor fuels in Japan during the past 20 years (mostly in last 10 years), we processed only about 350 kg of highly enriched uranium and supplied approximately 1000 fuel elements to JAERI, Kyoto University, and others, and we have been suffering red-ink balance of budget every year

[en] This paper contains a brief summary of activities in the field of research reactor fuel fabrication in Nuclear Fuel Industries Sumitomo and Furukawa Industries. Since 1956 2 million dollars were spent for development of nuclear fuels and plant facilities including complete manufacturing and testing capabilities. Now this company is the only fuel supplier for the research reactors in Japan. The fabrication process starts with the melting, alloying, and casting of U-Al. The uranium billets are prepared by foreign fabricators. The uranium content varies from 13 to 22 wt % according to the purchaser's specifications. In making fuel plates, the picture frame method is applied. In this case, the original procedure is sufficiently effective in avoiding dogboning. The plates are finished by hot and cold roll milling and inspected dimensionally, metallurgically, and mechanically, and at the same time the blister test and X-ray radiographic tests are performed. Fuel elements are assembled by rolling flat or curved plates into side plate grooves and end-fit welding. Finished elements are tested dimensionally and hydraulically. Nominal losses during operation are less than 1% of the uranium metal. Our present capacity licensed by the Japanese Government is approximately 950 fuel elements a year. About 35 employees including engineers are engaged in development and manufacturing of fuels. Owing to the small limited demand of the research reactor fuels in Japan during the past 20 years (mostly in last 10 years), we processed only about 350 kg of highly enriched uranium and supplied approximately 1000 fuel elements to JAERI, Kyoto University, and others, and we have been suffering red-ink balance of budget every year. Some of trials in development are briefly discussed. In case of UO₂-Al metal fuel plates, the vibratory compacting method was very popular among many researchers about 10 years ago. A lot of time and money was spent to study the economic fabrication process of fuel rods for the power reactors. By the way, we tried the feasibility study of applying the method in obtaining the high density UO₂-Al compact as the starting materials for the fuel meat. High density sintered UO₂ pellets were crushed, sieved, and uniformly blended with aluminum powders. The picture frame containing the blend was hot and cold rolled, and the finished plates were inspected. After the extensive work, we reached the conclusions that the particle size distribution of the crushed UO₂ powders must be carefully controlled in the case of high content of UO₂ and that the method is sufficient and economic to furnish the dimensionally and mechanically sound fuel plate. But, in the heating test, blisters occurred severely; therefore, the trial was stopped without any further development. According to JAERI's demand to supply some fuel plates prepared by the U - Aluminide procedure, about years ago, we installed some experimental facilities and surveyed the processing of the materials. Arc melt U - Aluminide was prepared and plates containing up to 30 wt % U were furnished and inspected. The fuel plates were quite similar and equivalent to the plate furnished after the ordinary melting and casting method, but we stopped the trials because, at the time, we had no definite objectives to continue and extend our development works. It is very unfortunate for us that we, in the near future, will lose the chance to supply the fuels fabricated by our already established process using highly enriched uranium and to compensate our past financial deficits. At the present time, we have no firm plans whether we will develop the process of supplying the high uranium content fuels using medium enriched uranium or if we will discontinue our activities

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[en] Results of the surface smoothing of a CVD-diamond membrane by gas cluster ion beams are presented. An as-deposited diamond membrane with a surface roughness of 400 Aa Ra was irradiated by Ar cluster ions with a energy of 20 keV. A very smooth surface of 30 Aa Ra was obtained at a dose of 3x10¹⁷ ions/cm². This result can be clarified by computer simulation which shows that the surface smoothing of the diamond membrane was improved by a lateral sputtering of the cluster ions. However, a thin graphite layer was formed on the surface by contamination of monomer ions in the cluster beam, which decreased the transparency of the diamond membrane. A subsequent irradiation with O₂ cluster ions removed these graphite layers

[en] Bipolar resistive switching characteristics of CeO_x layer on Si-based bottom electrodes (BE) are presented. Owing to the formation and the presence of a thin SiO₂ interfacial layer (SiO₂-IL) between the CeO_x layer and BE, the set process is triggered by a local breakdown at the thin SiO₂-IL due to large differences in dielectric constants. Reset process, on the other hand, is obtained by local anodic oxidation to the breakdown spots by the high oxygen ion conductivity of the CeO_x layer. High insulating properties of SiO₂-IL enables obtaining a resistance ratio of over 10⁵ at high-resistive-state to low-resistive-state. A model to explain the resistance ratio has been proposed using initial trap density of SiO₂-IL. Moreover, forming-free feature can be achieved with NiSi₂ BE. (paper)

[en] Interface properties of La-silicate gate dielectrics on Si substrates with W or nano-sized grain W₂C gate electrodes have been investigated. A low interface state density of 2.5 × 10¹¹ cm⁻²/eV has been achieved with W₂C gate electrodes, which is one third of those with W gate electrode. An interface roughness of 0.33 nm with spatial frequency comparable to the grain size of W gate electrode has been observed. Besides, an atomically flat interface of 0.12 nm has been obtained with W₂C gate electrode. The origin of flat interface may be attributed to the elimination of inhomogeneous stress by grains in metal electrode

[en] The effect of remote Coulomb scattering on electron mobility in W/La₂O₃/Si gate stacked metal-oxide-semiconductor field-effect transistors (MOSFETs) was studied. Experimental results show that scattering caused by the Coulomb charges located near the W/La₂O₃ interface becomes a dominant factor for the mobility of MOSFETs with an equivalent oxide thickness (EOT) of 1 nm or less. (paper)

[en] The physical and electrical properties of Ni silicides, reactively formed by a thin Ni layer of 3 nm, have been investigated. The existence of NiSi₂ phase has been confirmed at low temperature annealing by x-ray photoelectron spectroscopy. The silicides have shown flat surfaces up to an annealing temperature of 800 °C and a stable sheet resistance can be achieved. The Schottky barrier heights extracted from diode characteristics have shown stable values against annealing temperature owing to the stability of the film with an ideality factor nearly to unit.