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Journal Articles

Determination of fusion barrier distributions from quasielastic scattering cross sections towards superheavy nuclei synthesis

Tanaka, Taiki*; Narikiyo, Yoshihiro*; Morita, Kosuke*; Fujita, Kunihiro*; Kaji, Daiya*; Morimoto, Koji*; Yamaki, Sayaka*; Wakabayashi, Yasuo*; Tanaka, Kengo*; Takeyama, Mirei*; et al.

Journal of the Physical Society of Japan, 87(1), p.014201_1 - 014201_9, 2018/01

 Times Cited Count:10 Percentile:72.43(Physics, Multidisciplinary)

Excitation functions of quasielastic scattering cross sections for the $$^{48}$$Ca + $$^{208}$$Pb, $$^{50}$$Ti + $$^{208}$$Pb, and $$^{48}$$Ca + $$^{248}$$Cm reactions were successfully measured by using the gas-filled recoil-ion separator GARIS. Fusion barrier distributions were extracted from these data, and compared with the coupled-channels calculations. It was found that the peak energies of the barrier distributions for the $$^{48}$$Ca + $$^{208}$$Pb and $$^{50}$$Ti + $$^{208}$$Pb systems coincide with those of the 2n evaporation channel cross sections for the systems, while that of the $$^{48}$$Ca + $$^{248}$$Cm is located slightly below the 4n evaporation ones. This results provide us helpful information to predict the optimum beam energy to synthesize superheavy nuclei.

Journal Articles

Influence of heating method on size and morphology of metallic oxide powder synthesized from metallic nitrate solution

Segawa, Tomomi; Fukasawa, Tomonori*; Yamada, Yoshikazu; Suzuki, Masahiro; Yoshida, Hideto*; Fukui, Kunihiro*

Proceedings of Asian Pacific Confederation of Chemical Engineering 2015 (APCChE 2015), 8 Pages, 2015/09

A mixed solution of uranyl nitrate and plutonium nitrate is converted to MOX raw powder by the microwave heating de-nitration method in nuclear reprocessing. Copper oxide synthesized by heating de-nitration was used as a model for the de-nitration process. The microwave heating method (MW) and infrared heating method (IR) were used, and how they and their heating rate influence the obtained particle morphology and size were investigated. The particles obtained by the MW and IR were sufficiently similar in the surface morphology and the mass median diameter was decreased by the increased heating rate. The mass median diameters by the MW were the heating rate and smaller than those obtained by IR. The particle size distribution of the particle obtained by the MW was broader than that by the IR. The relationship of the temperature distribution and particle size distribution by the MW was discussed by the numerical simulation.

Journal Articles

Nickel oxide powder synthesis from aqueous solution of nickel nitrate hexahydrate by a microwave denitration method

Segawa, Tomomi; Kawaguchi, Koichi; Ishii, Katsunori; Suzuki, Masahiro; Arimitsu, Naoki*; Yoshida, Hideto*; Fukui, Kunihiro*

Advanced Powder Technology, 26(3), p.983 - 990, 2015/05

 Times Cited Count:6 Percentile:27.32(Engineering, Chemical)

Denitration of the aqueous solution of nickel nitrate hexahydrate (Ni(NO$$_{3}$$)$$_{2}$$$$cdot$$6H$$_{2}$$O) by a microwave heating method was investigated. Since Ni(NO$$_{3}$$)$$_{2}$$$$cdot$$6H$$_{2}$$O aqueous solution cannot be heated to over 300 $$^{circ}$$C by microwave irradiation owing to the low microwave absorptivity of its intermediate, NiO could not previously be obtained by microwave heating. We propose a novel NiO synthesis method that uses microwave heating without the risk of chemical contamination. A NiO powder reagent was added to the solution as a microwave acceptor. The denitration efficiency to NiO could be improved by an adiabator around the reactor to increase the temperature homogeneity in the reactor. Numerical simulations also reveal that the use of the adiabator results in remarkable changes in the electromagnetic field distribution in the reactor, temperature inhomogeneity decreases.

Journal Articles

Characterization of water conducting fracture and their long-term behavior in deep crystalline rock; A Case study of the Toki granite

Ishibashi, Masayuki; Ando, Tomomi*; Sasao, Eiji; Yuguchi, Takashi; Nishimoto, Shoji*; Yoshida, Hidekazu*

Oyo Chishitsu, 55(4), p.156 - 165, 2014/10

Understanding of long-term history of water-conducting features such as flow-path fractures is key issue to evaluate deep geological environment for geological disposal of high-level radioactive waste (HLW). Thus, we conducted study on the geological features and the long-term behavior of flow-path fractures based on the data obtained at -300m levels in the Mizunami Underground research laboratory (MIU), central Japan. Total 1670 fractures were mapped in underground gallery at the -300m levels. Flow-path fractures occupy about 11% of all fractures. The flow-path fractures are divided into grout filling fractures and low inflow-rate fractures. All of the grout filling fractures is filled with calcite as fracture filling minerals without conspicuous host rock alteration around fractures. The low inflow-rate fractures possessed similar geological character with the sealed fractures which are not acted as flow-path. The geological character of fracture filling and host tock alteration around fractures indicates the history of the formation at the time of intrusion and emplacement of host granite (Stage I), then filling at hydrothermal event (Stage II), and finally opening and elongation during exhumation stage (Stage III). In conclusion, the present flow-path fractures were formed by opening and/or elongation of pre-existed fractures, which were filled at the hydrothermal event, at the time of exhumation.

Journal Articles

Mechanism of synthesis of metallic oxide powder from aqueous metallic nitrate solution by microwave denitration method

Fukui, Kunihiro*; Igawa, Yusuke*; Arimitsu, Naoki*; Suzuki, Masahiro; Segawa, Tomomi; Fujii, Kanichi*; Yamamoto, Tetsuya*; Yoshida, Hideto*

Chemical Engineering Journal, 211-212, p.1 - 8, 2012/11

 Times Cited Count:13 Percentile:46.48(Engineering, Environmental)

The process for synthesizing metallic oxide powders by the microwave denitration method was investigated using hexahydrated nickel nitrate and trihydrated copper nitrate aqueous solutions, and the electrical field and the temperature distributions in the reactor were numerically simulated. Although CuO powder can be obtained from a trihydrated copper nitrate aqueous solution by the microwave denitration method, a hexahydrated nickel nitrate aqueous solution cannot be heated up to over 270 $$^{circ}$$C by microwave irradiation. It was also found that the reaction routes for microwave heating are the same as those for conventional external heating. This finding indicates that the success of producing oxide particles by microwave denitration depends not only on the microwave absorptivity of the intermediate and the metallic oxide, but also on the temperature difference.

Oral presentation

Development of synthesis process of nikel oxide powder by microwave

Segawa, Tomomi; Suzuki, Masahiro; Fujii, Kanichi; Igawa, Yusuke*; Arimitsu, Naoki*; Yamamoto, Tetsuya*; Fukui, Kunihiro*; Yoshida, Hideto*

no journal, , 

The synthesis process of the denitration reaction by the microwave heating method was investigated using a nickel nitrate (Ni(NO$$_{3}$$)$$_{2}$$) aqueous solution. NiO powder cannot be obtained from Ni(NO$$_{3}$$)$$_{2}$$ aqueous solution by the microwave heating method because of low microwave absorption of the intermediate obtained from nitrate aqueous solution. In the present work, it was showed that Ni(NO$$_{3}$$)$$_{2}$$ aqueous solution with 6.0 g of NiO powder as a microwave absorber can be completely converted to NiO powder by microwave heating. NiO powder promotes the denitration reaction, and reduces the required reaction time with increasing the amount of NiO powder. Furthermore the adiabator was set around the reactor in order to equalize the temperature distribution in the reactor. It was also found that the denitration efficiency of Ni(NO$$_{3}$$)$$_{2}$$ aqueous solution to NiO powder can be improved by using the adiabator when the center of the reactor has the same temperature.

Oral presentation

Development of the thermogravimetric analysis method using microwave heating and its application

Segawa, Tomomi; Hamaba, Taishu*; Yoshida, Hideto*; Fukui, Kunihiro*

no journal, , 

In the field of reprocessing of spent nuclear fuel, the aqueous solution of uranyl nitrate and plutonium nitrate is converted to the mixed oxide powder (MOX raw powder) using the microwave heating method for direct denitration. In order to clarify the reaction mechanism of denitration of a metallic nitrate aqueous solution using microwaves, the novel thermogravimetric analysis unit using microwave heating was developed. The absorbed microwave energy can be measured by 2 power meters set on the both side of the raw material. The change in the temperature and the mass of the raw material can be also measured continuously. The process for synthesizing metallic oxide powders by the microwave denitration method was investigated using trihydrated copper nitrate aqueous solutions with this apparatus. As a result of this study, it was found that the reaction routes for microwave heating are the same as those for conventional external heating.

Oral presentation

Development of the thermogravimetric analysis unit using microwave heating and its application

Hamaba, Taishu*; Segawa, Tomomi; Fukasawa, Tomonori*; Yoshida, Hideto*; Fukui, Kunihiro*

no journal, , 

no abstracts in English

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