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Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.
Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03
Times Cited Count:43 Percentile:96.93(Astronomy & Astrophysics)Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.
Wang, H.*; Otsu, Hideaki*; Chiga, Nobuyuki*; Kawase, Shoichiro*; Takeuchi, Satoshi*; Sumikama, Toshiyuki*; Koyama, Shumpei*; Sakurai, Hiroyoshi*; Watanabe, Yukinobu*; Nakayama, Shinsuke; et al.
Communications Physics (Internet), 2(1), p.78_1 - 78_6, 2019/07
Times Cited Count:8 Percentile:56.2(Physics, Multidisciplinary)Searching for effective pathways for the production of proton- and neutron-rich isotopes through an optimal combination of reaction mechanism and energy is one of the main driving forces behind experimental and theoretical nuclear reaction studies as well as for practical applications in nuclear transmutation of radioactive waste. We report on a study on incomplete fusion induced by deuteron, which contains one proton and one neutron with a weak binding energy and is easily broken up. This reaction study was achieved by measuring directly the cross sections for both proton and deuteron for Pd at 50 MeV/u via inverse kinematics technique. The results provide direct experimental evidence for the onset of a cross-section enhancement at high energy, indicating the potential of incomplete fusion induced by loosely-bound nuclei for creating proton-rich isotopes and nuclear transmutation of radioactive waste.
Asai, Shiho; Hanzawa, Yukiko; Konda, Miki; Suzuki, Daisuke; Magara, Masaaki; Kimura, Takaumi; Ishihara, Ryo*; Saito, Kyoichi*; Yamada, Shinsuke*; Hirota, Hideyuki*
Talanta, 185, p.98 - 105, 2018/08
Times Cited Count:8 Percentile:31.98(Chemistry, Analytical)Estimating the risks associated with radiation from long-lived fission products (LLFP) in radioactive waste is essential to ensure the long-term safety of potential disposal sites. In this study, the amount of Zr, a LLFP, was determined by ICP-MS after separating Zr from a spent nuclear fuel solution using a microvolume anion-exchange cartridge (TEDA cartridge). The TEDA cartridge achieved highly selective separation of Zr regardless of its small bed volume of 0.08 cm. The time taken to complete the Zr separation was 1.2 min with a flow rate of 1.5 mL/min, which was 10 times faster than that for a conventional anion-exchange resin column. Almost all the other elements were removed, leading to accurate measurement of Zr. The result connects experimental value to theoretical prediction provided by ORIGEN2, which requires verification. With the measured value, we demonstrated that the theoretical value is reliable enough to estimate radiation risks.
Asai, Shiho; Hanzawa, Yukiko; Konda, Miki; Suzuki, Daisuke; Magara, Masaaki; Kimura, Takaumi; Ishihara, Ryo*; Saito, Kyoichi*; Yamada, Shinsuke*; Hirota, Hideyuki*
Analytical Chemistry, 88(6), p.3149 - 3155, 2016/03
Times Cited Count:8 Percentile:29.82(Chemistry, Analytical)Neptunium-237 (Np) is one of the major long-lived radionuclides found in spent nuclear fuel. To evaluate the long-term safety of a HLW repository, the Np content in spent nuclear fuel must be determined. In this study, micro-volume anion-exchange porous polymer disk-packed cartridges were prepared for Am-Np separation, which is required prior to the measurement of Np with ICP-MS. Disks with a volume of 0.08 cm were cut out from porous sheets having triethylenediamine (TEDA)-containing polymer chains densely attached on the pore surface. The resulting TEDA-introduced disk cartridge was applied to a spent nuclear fuel sample. The chemical yield of Np was 90.4%, which is sufficiently high for ICP-MS measurement of Np. Compared with the conventional separation technique using commercially available anion-exchange resin columns, the time required to adsorb, wash and elute Np using the TEDA-introduced disk cartridge was reduced by 75%.
Tanaka, Ryota*; Ishihara, Ryo*; Miyoshi, Kazuyoshi*; Umeno, Daisuke*; Saito, Kyoichi*; Asai, Shiho; Yamada, Shinsuke*; Hirota, Hideyuki*
Separation Science and Technology, 49(1), p.154 - 159, 2014/01
Times Cited Count:4 Percentile:16.82(Chemistry, Multidisciplinary)Uchiyama, Shoichiro*; Ishihara, Ryo*; Umeno, Daisuke*; Saito, Kyoichi*; Yamada, Shinsuke*; Hirota, Hideyuki*; Asai, Shiho
Journal of Chemical Engineering of Japan, 46(6), p.414 - 419, 2013/06
Times Cited Count:7 Percentile:26.06(Engineering, Chemical)Wada, Go*; Ishihara, Ryo*; Miyoshi, Kazuyoshi*; Umeno, Daisuke*; Saito, Kyoichi*; Asai, Shiho; Yamada, Shinsuke*; Hirota, Hideyuki*
Solvent Extraction and Ion Exchange, 31(2), p.210 - 220, 2013/02
Times Cited Count:2 Percentile:12.24(Chemistry, Multidisciplinary)A crosslinked chelating porous sheet was prepared by cografting ethylene glycol dimethacrylate (EGDMA) with glycidyl methacrylate onto an electron-beam-irradiated porous polyethylene sheet, followed by the introduction of an iminodiacetate group. At a molar percentage of EGDMA of 1.0 mol%, the sheet exhibited a maximum dynamic binding capacity for copper ions of 0.93 mmol/g, while the equilibrium binding capacity remained the same (1.2 mmol/g) as that of a non-crosslinked chelating porous sheet. The crosslinking of the grafted chain causes copper ions to lower their diffusion rate along the sheet thickness driven by the gradient of the amount of copper ions adsorbed.
Ishihara, Ryo*; Asai, Shiho; Otosaka, Shigeyoshi; Yamada, Shinsuke*; Hirota, Hideyuki*; Miyoshi, Kazuyoshi*; Umeno, Daisuke*; Saito, Kyoichi*
Solvent Extraction and Ion Exchange, 30(2), p.171 - 180, 2012/02
Times Cited Count:8 Percentile:31.67(Chemistry, Multidisciplinary)Wada, Go*; Ishihara, Ryo*; Miyoshi, Kazuyoshi*; Umeno, Daisuke*; Saito, Kyoichi*; Asai, Shiho; Yamada, Shinsuke*; Hirota, Hideyuki*
Nihon Ion Kokan Gakkai-Shi, 22(2), p.47 - 52, 2011/01
no abstracts in English
Tanaka, Ryota*; Ishihara, Ryo*; Miyoshi, Kazuyoshi*; Umeno, Daisuke*; Saito, Kyoichi*; Asai, Shiho; Yamada, Shinsuke*; Hirota, Hideyuki*
Reactive and Functional Polymers, 70(12), p.986 - 990, 2010/12
Times Cited Count:7 Percentile:29.11(Chemistry, Applied)Asai, Shiho; Kimura, Takaumi; Miyoshi, Kazuyoshi*; Saito, Kyoichi*; Yamada, Shinsuke*; Hirota, Hideyuki*
Nihon Ion Kokan Gakkai-Shi, 21(3), p.334 - 339, 2010/07
Asai, Shiho; Magara, Masaaki; Shinohara, Nobuo; Yamada, Shinsuke*; Nagai, Masanori*; Miyoshi, Kazuyoshi*; Saito, Kyoichi*
no journal, ,
A porous sheet with a diethylamino (DEA) group as anion-exchange group was prepared for achieving rapid separation of U and Pu. The epoxy group containing monomer, glycidyl methacrylate was grafted onto the surface of the porous sheet. The epoxy group of the poly-GMA graft polymer chain was converted into a DEA group. The amount of the DEA group was increased with increasing reaction time and leveled off at 3.4 mol/kg of the sheet. An iron solution as a model metal ion solution was forced to permeate through the pores of the DEA-introduced sheet (DEA sheet) at a permeation rate of 20 mL/min. The equilibrium adsorption capacity of the DEA sheet for Fe ions (FeCl) was calculated as 1.1 mol-Fe/kg-DEA sheet. This value is comparable to or higher than those of conventional anion-exchange resins. U and Pu in the sample solution were separated using the DEA sheet. Trace amounts of U (38.16 pg) and Pu (0.34 pg) were found to be successfully separated with the DEA sheet.
Asai, Shiho; Magara, Masaaki; Shinohara, Nobuo; Yamada, Shinsuke*; Nagai, Masanori*; Miyoshi, Kazuyoshi*; Saito, Kyoichi*
no journal, ,
The use of a column charged with an ion-exchange resin has been widely employed to separation of actinides. However, the use of the resin-packed column has a drawback in that a higher flow rate of the sample solution through the column results in a lower recovery. In order to overcome this drawback in the use of the conventional column, we prepared an anion-exchange cartridge charged with a diethylamino-group-containing porous disk. To evaluate the applicability, the binding efficiencies of U and Pu were determined at various flow rates. 5 mL of standard solution containing U and Pu was permeated through the anion-exchange cartridge at the flow rate raging from 0.3 to 80 mL/min. Adsorption efficiencies of U and Pu were 1.0 irrespective of the flow rate. This adsorption characteristic is advantageous over the conventional anion-exchange resin-packed column in that a higher flow rate of the sample solution, i. e., a shorter processing time of analysis, is achievable.
Asai, Shiho; Esaka, Fumitaka; Shinohara, Nobuo; Yamada, Shinsuke*; Nagai, Masanori*; Miyoshi, Kazuyoshi*; Saito, Kyoichi*
no journal, ,
no abstracts in English
Asai, Shiho; Esaka, Fumitaka; Shinohara, Nobuo; Hirota, Hideyuki*; Yamada, Shinsuke*; Miyoshi, Kazuyoshi*; Saito, Kyoichi*
no journal, ,
no abstracts in English
Asai, Shiho; Otosaka, Shigeyoshi; Tanaka, Ryota*; Miyoshi, Kazuyoshi*; Ishihara, Ryo*; Saito, Kyoichi*; Yamada, Shinsuke*; Hirota, Hideyuki*
no journal, ,
no abstracts in English
Asai, Shiho; Kimura, Takaumi; Miyoshi, Kazuyoshi*; Saito, Kyoichi*; Yamada, Shinsuke*; Hirota, Hideyuki*
no journal, ,
no abstracts in English
Tanaka, Ryota*; Ishihara, Ryo*; Miyoshi, Kazuyoshi*; Umeno, Daisuke*; Saito, Kyoichi*; Asai, Shiho; Yamada, Shinsuke*; Hirota, Hideyuki*
no journal, ,
A basic extractant Aliquat 336 dissolved in a mixture of ethanol and NaOH aqueous solution was impregnated to carboxydecanyl-thiol (CDT) group containing polymer chains grafted onto a porous sheet. The CDT group was introduced into the graft chain by a reaction of the epoxy group of poly-glycidyl methacrylate (GMA) chain grafted onto the porous sheet with 11-mercaptoundecanoic acid. The electrostatic interaction between the carboxyl moiety of the CDT group and the quaternary ammonium group of Aliquat 336 gave rise to a high-density impregnation of Aliquat 336. Palladium chloride (50 mg-Pd/L) in 1 M HCl was forced to permeate through the pores of the Aliquat 336-impregnated porous sheet. The binding efficiency, defined as the ratio of number of moles of palladium adsorbed to half the number of moles of impregnated Aliquat 336, was found to be 64%.
Asai, Shiho; Hanzawa, Yukiko; Konda, Miki; Suzuki, Daisuke; Magara, Masaaki; Kimura, Takaumi; Ishihara, Ryo*; Saito, Kyoichi*; Yamada, Shinsuke*; Hirota, Hideyuki*
no journal, ,
no abstracts in English
Asai, Shiho; Hanzawa, Yukiko; Konda, Miki; Suzuki, Daisuke; Magara, Masaaki; Kimura, Takaumi; Ishihara, Ryo*; Saito, Kyoichi*; Yamada, Shinsuke*; Hirota, Hideyuki*
no journal, ,
no abstracts in English
Asai, Shiho; Hanzawa, Yukiko; Konda, Miki; Suzuki, Daisuke; Magara, Masaaki; Kimura, Takaumi; Ishihara, Ryo*; Saito, Kyoichi*; Yamada, Shinsuke*; Hirota, Hideyuki*
no journal, ,
Zr is a long-lived fission product which can be found in spent nuclear fuel and HLW. The estimation of theZr content is indispensable to achieve a safety disposal of HLW because Zr is predicted to be one of the major contributors to radiation dose. However, only a few measured Zr values have been reported, leading to a high demand for development of an efficient analytical method. Our group has been prepared a new porous filter cartridge which has densely bound ion-exchanger onto the pore surface of the filter, enabling a high-capacity and rapid adsorption. In order to apply this filter cartridge to a pretreatment for the Zr measurement with ICP-MS, an elution profiles of Zr and the other coexisting elements were examined. According to the resultant separation conditions, Zr in a spent nuclear fuel sample was successfully separated. The measured Zr content is 98.2 5.1 ng, which agrees with the theoretical value.