Ouchi, Kazuki; Tsukahara, Takehiko*; Brandt, A.*; Muto, Yuki*; Nabatame, Nozomi*; Kitatsuji, Yoshihiro
Analytical Sciences, 37(12), p.1789 - 1794, 2021/12
We attempted to scale down a separation process of uranium (U) using the microchip column loaded with anion exchange resin to develop safety and waste-reducing separation technique. The ideal separation performance of U was obtained by the properly design of a microchannel. The concentration of U in seawater as a real-world sample could be quantified with the prepared microchip column. It indicates that the microchip column is sufficiently practical. Compared to separation of U with a general column, the column size was successfully scaled down to 1/5000.
Yomogida, Takumi; Saeki, Morihisa*; Morii, Shiori; Oba, Hironori*; Kitatsuji, Yoshihiro
Analytical Sciences, 37(12), p.1843 - 1846, 2021/12
In this study, we developed a simple and one-step Pd separation technique based on photoreduction with Xe lamp irradiation for the determination of Pd in highly radioactive samples. A simulated high-level radioactive liquid wastes (HLLW) solution, which consists of 14 major elements (Rb, Sr, Zr, Mo, Ru, Rh, Pd, Cs, Ba, La, Ce, Pr, Nd, Sm) in a 3 mol L HNO solution, was used to evaluate the separation performance. The Pd precipitate were formed by Xe lamp irradiation and recovered by centrifugation. The results showed that the recovery of Pd from a simulated HLLW solution depend on the irradiation time and concentration of ethanol. By optimizing the conditions at photo irradiation, the Pd recovery from the simulated HLLW solution reached up to 50 %, while 99.5 % of the other 13 elements were separated. The Pd precipitate could be separated from the elements that are the main source of radioactivity (Sr, Cs, and Ba) and the source of spectral interference for the determination of Pd (Zr, and Ru). These results indicate that selective separation of Pd is achieved with the proposed method, showing the applicability of the proposed separation technique to HLLW samples.
Inagawa, Jun; Kitatsuji, Yoshihiro; Otobe, Haruyoshi; Nakada, Masami; Takano, Masahide; Akie, Hiroshi; Shimizu, Osamu; Komuro, Michiyasu; Oura, Hirofumi*; Nagai, Isao*; et al.
JAEA-Technology 2021-001, 144 Pages, 2021/08
Plutonium Research Building No.1 (Pu1) was qualified as a facility to decommission, and preparatory operations for decommission were worked by the research groups users and the facility managers of Pu1. The operation of transportation of whole nuclear materials in Pu1 to Back-end Cycle Key Element Research Facility (BECKY) completed at Dec. 2020. In the operation included evaluation of criticality safety for changing permission of the license for use nuclear fuel materials in BECKY, cask of the transportation, the registration request of the cask at the institute, the test transportation, formulation of plan for whole nuclear materials transportation, and the main transportation. This report circumstantially shows all of those process to help prospective decommission.
Ouchi, Kazuki; Komatsu, Atsushi; Takao, Koichiro*; Kitatsuji, Yoshihiro; Watanabe, Masayuki
Chemistry Letters, 50(6), p.1169 - 1172, 2021/06
The electrochemical behavior of uranium (IV) tetrachloride in ionic liquid-DMF mixture was studied for first time in order to build a redox flow battery (RFB) using U as an electrode active material. We found a quasi-reversible U/U couple that could be applied to the anode reaction of the RFB.
Sasaki, Yuji; Morita, Keisuke; Kitatsuji, Yoshihiro; Ito, Keisuke*; Yoshizuka, Kazuharu*
Solvent Extraction Research and Development, Japan, 28(2), p.121 - 131, 2021/00
High concentration of Cs is present in high-level radioactive waste. It is well-known that Cs is an alkali element and difficult to extract completely into an organic phase. Crown ether compounds are widely available for Cs extractants; DtBuDB18C6 (di--butyl-dibenzo-18crown6), was used in this study. Organic solvents used for the industrial applications, such as -dodecane and 1-octanol, have low solubility concerning the compound; other solvents were employed and tested. In this study, ketone-, ether-, and ester-type solvents showed high solubility for DtBuDB18C6 and DtBuDB18C6, when dissolved in ketones and alcohols, exhibited relatively high Cs distribution ratios ((Cs)), closely to 10.
Horita, Takuma; Asai, Shiho*; Konda, Miki; Matsueda, Makoto; Hanzawa, Yukiko; Kitatsuji, Yoshihiro
Bunseki Kagaku, 69(10/11), p.619 - 626, 2020/10
We have developed a Sr adsorption fiber for rapid analysis of Sr. The prepared Sr adsorption fiber has a Sr-extraction layer that densely retains a Sr-selective extractant, an 18-crown-6 ether derivative, on the fiber surface. Hydrophobic group-containing polymer chains embedded onto the surface of the fiber allow to form a hydrophobic phase, incorporating Sr-selective extractants. This unique surface structure provides high adsorption capacity, leading to rapid and highly efficient adsorption of Sr. The adsorption capacity of the Sr adsorption fiber was 3 times higher than commercially available 18-crown-6 ether derivative-impregnated resin (Sr Resin). The equilibrium adsorption capacity of the Sr adsorption fiber was comparable to the Sr Resin. The retained Sr was finally determined by a GM counter. The total analysis time including the Sr adsorption and measurement was about 1 hour.
Asai, Shiho*; Ohata, Masaki*; Hanzawa, Yukiko; Horita, Takuma; Yomogida, Takumi; Kitatsuji, Yoshihiro
Analytical Chemistry, 92(4), p.3276 - 3284, 2020/02
The long-term safety assessment of spent Cs adsorbents produced during the decontamination of radiocesium-containing water at the Fukushima Daiichi Nuclear Power Plant requires one to estimate their Cs content prior to final disposal. Cs is usually quantified by inductively coupled plasma mass spectrometry (ICP-MS), which necessitates the elution of Cs from Cs adsorbents. However, this approach suffers from the high radiation dose from Cs. To address this challenge, we herein employed laser ablation ICP-MS for direct quantitation of Cs in Cs adsorbents and used a model Cs adsorbent prepared by immersion of a commercially available Cs adsorbent into radiocesium-containing liquid waste to verify the developed technique. The use of the Cs/Cs ratio and Cs radioactivity obtained by gamma spectrometry achieved simple and precise quantitation of Cs and the resulting Cs activity of 0.36 Bq agreed well with that in the original radiocesium-containing liquid waste.
Kaneko, Masashi; Kato, Akane*; Nakashima, Satoru*; Kitatsuji, Yoshihiro
Inorganic Chemistry, 58(20), p.14024 - 14033, 2019/10
We applied density functional theory calculations to ruthenium-nitrosyl complexes, which are known to exist in high-level radioactive waste, to give a theoretical correlation between Ru Mssbauer spectroscopic parameters ( and ) and ligand field strength () for the first time. The structures of the series of complexes, [Ru(NO)L] (L = Br, Cl, NH, CN), were modeled based on the corresponding single-crystal X-ray coordinates. The comparisons of the geometries and total energies between the different spin states suggested that the singlet spin state of [Ru(II)(NO)L] complexes were the most stable. The calculated results of both the and values reproduced the experimental results by reported previously and increased in the order of L = Br, Cl, NH, CN. Finally, we estimated the ligand field strength () based on molecular orbitals, assuming C symmetry and showed the increase of values in that order, being consistent with well-known spectrochemical series of ligands. The increase attributes to the strengthening of the abilities of -donor and -acceptor of the L-ligands to the Ru atom, resulting in the increase of the values.
Kimuro, Shingo; Kirishima, Akira*; Kitatsuji, Yoshihiro; Miyakawa, Kazuya; Akiyama, Daisuke*; Sato, Nobuaki*
Journal of Chemical Thermodynamics, 132, p.352 - 362, 2019/05
A combination of potentiometry and calorimetry was used for the determination of the thermodynamic quantities of complexation of generic and groundwater humic acid (HA), which was isolated from deep groundwater at Horonobe, Hokkaido, Japan, with copper (II) ions and uranyl (VI) ions. The apparent complexation constant of Horonobe HA was independent of the pH, whereas that of generic HA was dependent on the pH. This observation indicates that the polyelectrolyte effect of Horonobe HA is negligible because of its small molecular size. In addition, the effect of the heterogeneity of Horonobe HA was not significant. Moreover, the complexation enthalpy of Horonobe HA was consistent with that of homogeneous poly(acrylic acid), which means the complexation of Horonobe HA was not affected by the functional group heterogeneity. Consequently, the characteristic complexation mechanism of Horonobe HA was revealed based on the determined thermodynamic quantities.
Asai, Shiho; Ohata, Masaki*; Yomogida, Takumi; Saeki, Morihisa*; Oba, Hironori*; Hanzawa, Yukiko; Horita, Takuma; Kitatsuji, Yoshihiro
Analytical and Bioanalytical Chemistry, 411(5), p.973 - 983, 2019/02
Determination of radiopalladium Pd is required for ensuring the radiation safety of Pd extracted from spent nuclear fuel for recycling or disposal. We employed laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to simplify an analytical procedure of Pd. Pd was separated through selective Pd precipitation reaction from spent nuclear fuel. Laser ablation allows direct measurement of the Pd precipitates, skipping the dissolution and dilution procedure. In this study, Pd in natural Pd standard solution was used as an internal standard, taking advantage of its absence in spent nuclear fuel. The Pd precipitate was uniformly embedded on the surface of the centrifugal filter, forming a microscopically thin flat surface of Pd. The resulting homogeneous Pd layer is suitable for obtaining a stable signal ratio of Pd/Pd. The amount of Pd obtained by LA-ICP-MS corresponds to the values obtained by conventional solution nebulization measurement.
Radioisotopes, 67(10), p.483 - 493, 2018/10
Electrochemical reactions and redox properties of actinides such as uranium and neptunium are outlined. The flow electrolysis enables rapid and high-efficient treatment. It was demonstrated to measure slow processes of actinide redox. Experimental results of electrolysis of actinide ions and the preparation method of oxidation state of the ions based on the fundamental data are described. Mediator reaction and catalysis observed in the process of electrolysis of actinide ions are also explained.
Yomogida, Takumi; Asai, Shiho; Saeki, Morihisa*; Hanzawa, Yukiko; Horita, Takuma; Esaka, Fumitaka; Oba, Hironori*; Kitatsuji, Yoshihiro
Bunseki Kagaku, 66(9), p.647 - 652, 2017/09
Palladium-107 is a long-lived fission product, which can be found in high-level radioactive liquid wastes (HLLW). Determination of the Pd contents in HLLW is essential to evaluate the long-term safety of HLLW repositories. However, the Pd content in HLLW has not been reported because of difficulties in pretreatment for the measurement. In this study, we investigated applicability of laser-induced photoreduction to HLLW solution: it enables a simple and non-contact separation of Pd. The results showed the recovery of 60% was achieved at the conditions: 40% ethanol, 20 min irradiation, 100 mJ of pulse energy. Additionally, major radionuclides and potentially interfering components in ICP-MS were removed from the simulated HLLW over a wide concentration range of Pd from 0.24 to 24 mg L, showing the applicability of the proposed separation technique to HLLW samples.
Segawa, Yukari; Horita, Takuma; Kitatsuji, Yoshihiro; Kumagai, Yuta; Aoyagi, Noboru; Nakada, Masami; Otobe, Haruyoshi; Tamura, Yukito*; Okamoto, Hisato; Otomo, Takashi; et al.
JAEA-Technology 2016-039, 64 Pages, 2017/03
The laboratory building No.1 for the plutonium research program (Bldg. Pu1) was chosen as one of the facilities to decommission by Japan Atomic Energy Agency Reform in September, 2013. The research groups, users of Bldg. Pu1, were driven by necessity to remove used equipment and transport nuclear fuel to other facilities from Bldg. Pu1. Research Group for Radiochemistry proactively established the Used Equipment Removal Team for the smooth operation of the removal in April, 2015. The team classified six types of work into the nature of the operation, removal of used equipment, disposal of chemicals, stabilization of mercury, stabilization of nuclear fuel, transportation of nuclear fuel and radioisotope, and survey of contamination status inside the glove boxes. These works were completed in December, 2015. This report circumstantially shows six works process, with the exception of the approval of the changes on the usage of nuclear fuel in Bldg. Pu1 to help prospective decommission.
Horita, Takuma; Asai, Shiho; Konda, Miki; Hanzawa, Yukiko; Saito, Kyoichi*; Fujiwara, Kunio*; Sugo, Takanobu*; Kitatsuji, Yoshihiro
Bunseki Kagaku, 66(3), p.189 - 193, 2017/03
A Sr-selective adsorption fiber was prepared for rapid analysis of Sr content by using radiation-induced emulsion graft polymerization and subsequent chemical modification. A polyethylene fiber with a diameter of 13 m was first immersed in a methanol solution of an epoxy-group-containing vinyl monomer, glycidyl methacrylate (GMA), and polyoxyethylene sorbitol ester (Tween20) as a surfactant for graft-polymerization of GMA. Octadecylamine was then bound to a polymer chain extending from the fiber surface providing hydrophobicity to the polymer chain. Dicyclohexano-18-crown-6 (DCH18C6) was finally impregnated onto the polymer chain via a hydrophobic interaction between the octadecyl moiety of the polymer chain and the cyclohexyl moiety of DCH18C6. The fiber surface structure, characterized by DCH18C6 molecules loosely entangled with polymer chains, afforded realizes the rapid and selective adsorption of Sr ions with an adsorption rate approximately 100 times higher than that of a commercially available Sr-selective resin (Sr Resin).
Ouchi, Kazuki; Otobe, Haruyoshi; Kitatsuji, Yoshihiro; Yamamoto, Masahiro
ECS Transactions, 75(27), p.51 - 57, 2017/01
We investigated the deposition of U(IV) following a valence change of U as electrodeposition using an electrochemical quartz crystal microbalance (EQCM). When measurements of the reduction of U(VI) in a weak acid solution were performed, deposits of U(IV) were observed on the electrode surface. From deposition rates, pH dependence of them, and oxidation potentials of deposits, we proposed the following deposition mechanism. The deposition is divided into the three phases; First, in the induction phase, U(IV) produced by the disproportionation forms U(IV) hydroxide nucleus. Next, in the growth phase, U(IV) deposits begin to grow. In this phase, the deposits catalyze the reduction of U(V) to U(IV), resulting an increase of the reduction current. Finally, in the transformation phase, U(IV) hydroxide species transform into U dioxide having more stable state.
Asai, Shiho; Yomogida, Takumi; Saeki, Morihisa*; Oba, Hironori*; Hanzawa, Yukiko; Horita, Takuma; Kitatsuji, Yoshihiro
Analytical Chemistry, 88(24), p.12227 - 12233, 2016/12
Safety evaluation of a radioactive waste repository requires credible activity estimates confirmed by actual measurements. A long-lived radionuclide, Pd, which can be found in radioactive wastes, is one of the difficult-to-measure nuclides and results in a deficit in experimentally determined contents. In this study, a precipitation-based separation method has been developed for the determination of Pd with ICP-MS. The photoreduction induced by laser irradiation at 355 nm provides short-time and one-step recovery of Pd. The proposed method was verified by applying it to a spent nuclear fuel sample. In order to efficiently recover Pd, a natural Pd standard was employed as the Pd carrier. The chemical yield of Pd was about 90% with virtually no impurities, allowing accurate quantification of Pd.
Bunseki, 2015(6), p.239 - 244, 2015/06
Electrochemical studies of ion transfer and charge transfer at liquid/liquid interface reported between 2012 and 2014 were surveyed. They were categorized by method of measurement. The merit of the method, improvement, species of application were described. Applied research such as analyses of redox inactive species, sensitive analyses based on adsorption at the interface and developments of new functional materials had been widely carried out.
Fujii, Toshiyuki*; Uehara, Akihiro*; Kitatsuji, Yoshihiro; Yamana, Hajimu*
Journal of Radioanalytical and Nuclear Chemistry, 303(1), p.1015 - 1020, 2015/01
The symmetric vibrational frequency of UO in chloride solutions was studied by Raman spectrometry and ab initio calculations. The frequency experimentally obtained decreased with the increase of concentration of Cl in solvent chlorides. This is attributable to that hydration water molecules in the equatorial plane of UO are substituted by Cl ions, which was consistent with the calculation results. The theoretical part was expanded to aqua- and chloro- Np(VI) complexes. The frequencies of neptunyl species computed were acceptable compared with the reported Raman shifts.
Otobe, Haruyoshi; Kitatsuji, Yoshihiro; Kurata, Masaki; Takano, Masahide
Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 11 Pages, 2014/10
The chemical and transport behaviors of Pu and U in the corroded debris must be understood for the criticality safety control of Pu and U in the debris, especially for the removal operations and storage. Therefore, the chemical changes of UO and PuO powders, disks and U and Pu metal disks in HO aqueous solution have been checked, where HO is formed by the radiolysis of HO. As a result, UO changed to hydrated uranium peroxide, whereas the PuO remained unchanged. U metal was more reactive with HO aqueous solution than Pu metal. The chemical changes of the mixed UO/PuO powders in HO aqueous solution have been investigated. The dried slurry of the middle zone of HO aqueous solution was mainly composed of hydrated uranium peroxide, whereas the dried powder of the bottom zone was mainly composed of PuO.
Kitatsuji, Yoshihiro; Otobe, Haruyoshi; Kimura, Takaumi; Kihara, Sorin*
Electrochimica Acta, 141, p.6 - 12, 2014/09
Reduction processes of U(VI) in weakly acidic solutions were investigated based on electrochemical and spectrophotometric measurements. A reversible one-electron reduction of U(VI) to U(V) and a further irreversible reduction of U(V) were observed voltammetrically at a gold microdisk electrode in solutions of pH from 2.0 to 3.5. Aggregates of U(IV) were formed as a deposit on the electrode and a colloid in the bulk solution, when the electrolysis was carried out at a gold gauze electrode, even though the potential applied was that available for the first one-electron reduction wave of U(VI) observed. It was elucidated that the aggregate was produced by the combination of the one-electron reduction to U(V) and the disproportionation of U(V) producing U(IV) and U(VI). The aggregate enhanced the rate of the disproportionation of U(V), and hence the reduction current of U(VI) increased abruptly when a definite amount of aggregate was formed on the electrode, in the solution, or both.