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.
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.
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
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.
Saeki, Morihisa*; Asai, Shiho; Oba, Hironori*
Bunseki, 2018(4), p.138 - 143, 2018/04
Platinum group metal (PGM) has attracted much attention in light of increasing demands in the industrial sector. A wide variety of techniques specialized for PGM separation, such as, solvent extraction, solid phase extraction, and molten salt electrolysis have been developed so far. Among such techniques, a newly developed separation technique based on laser-induced particulate formation can be a promising alternative to conventional ones. It enables non-contact and highly-selective separation with a simple operation. In this review, the research history and the basic mechanism of laser-induced particulate formation were outlined. Several applications were also mentioned, focusing on our latest research progress which achieved a world first quantitation of radioactive palladium in a spent nuclear fuel sample.
Saito, Kyoichi*; Asai, Shiho
Bunseki Kagaku, 66(11), p.771 - 782, 2017/11
Recovery and purification of rare metals, which are essential ingredients for highly functional materials, generally comes with operational difficulty. In this study, we have developed polymer adsorbents specially designed for highly-efficient adsorption of rare metal ions and exhibited their practical adsorption performances. Radiation-induced graft polymerization, one of the effective modification techniques for polymers, was employed for preparing the proposed adsorbents. Among such adsorbents, a 6-nylon fiber with nucleic-acid base, adenine, on the surface of the fiber demonstrated specific adsorption of ruthenium and palladium ions. In addition, a 6-nylon fiber with an extractant HDEHP (bis (2-ethylhexyl) phophoric acid) that has high affinity for lanthanides, achieved higher separation speed than a commercially available HDEHP-impregnated resin.
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.
Asai, Shiho; Saito, Kyoichi*
Biomedical Research on Trace Elements, 28(1), p.1 - 10, 2017/04
Radionuclides are commonly determined with radiometry and mass spectrometry. For -emitting nuclides, the activities can be measured without chemical separation due to the strong penetration ability. In contrast, the measurements of alpha and beta-emitting nuclides are generally associated with tedious and time-consuming chemical separation procedures to remove concomitants. Thus, an adsorbent that achieves rapid separation is desirable to reduce separation time and workload. Our research team has developed compact cartridge-type solid phase extraction materials which enable to facilitate separation procedures. In this review, basic separation performances of the developed cartridges were overviewed along with two application examples to radionuclide-containing samples.
Saito, Kyoichi*; Kojima, Takashi*; Asai, Shiho
Bunseki Kagaku, 66(4), p.233 - 242, 2017/04
Insoluble cobalt ferrocyanide and sodium titanate specifically capture cesium and strontium ions, respectively, in water contaminated with radionuclides which is found in Fukushima Daiichi NPP. The inorganic compounds used in this study were formed as precipitates in the polymer chain grafted onto a commercially available 6-nylon fiber using radiation-induced graft polymerization. An impregnation structure with the precipitates entangled by the grafted polymer chain through an electrostatic interaction via multipoints was indicated. The resultant insoluble cobalt ferrocyanide- or sodium titanate-impregnated fiber exhibited a higher adsorption rate and adsorption capacity per gram of the inorganic compound for cesium or strontium ions in seawater than conventional granular adsorbents.
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).
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.
Konda, Miki; Asai, Shiho; Hanzawa, Yukiko; Magara, Masaaki
JAEA-Technology 2015-054, 22 Pages, 2016/03
Isotope dilution mass spectrometry (IDMS) with ICP-MS is reliable method for determination of Zr-93, which is one of the long-lived fission products found in spent nuclear fuel and high-level radioactive wastes. In order to use an isotope standard solution of zirconium as the spike for IDMS, dissolving a commercially available solid isotope standard is indispensable. Prior to the dissolution of the Zr-91 isotope standard, solubility of metal zirconium in a mixture of HNO and HF was evaluated using zirconium metal chips. Then, 2 mg of the Zr-91 isotope standard was dissolved with 0.2 mL of 1 M HNO-3 v/v% HF mixed solution, followed by adjusting the concentration of Zr-91 to approximately 1,000 g/g. IDMS, in which a natural isotopic abundance standard solution of zirconium was used as the spike, was employed for the determination of the concentration of Zr-91 in the prepared Zr-91 isotope standard solution. The concentration of Zr-91 in the prepared Zr-91 isotope standard solution was (9.61.0) 10 g/g, which is in good agreement with the predicted concentration. This indicates that the Zr-91 metal isotope standard was completely dissolved with sufficient chemical stability. Additionally, no impurities were detected in the prepared Zr-91 isotope standard solution. These positive results denote that the Zr-91 isotope standard solution with the preferable quality for IDMS of Zr-93 can be obtained by the proposed dissolution procedures.
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
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%.
Asai, Shiho; Limbeck, A.*
Talanta, 135, p.41 - 49, 2015/04
A new analytical method for chondrite-normalized Rare earth elements (REE) plot has been developed in this study. Cation-exchange resin particles were used as a substrate to retain REE for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In LA analysis, formation of oxide and hydroxide of the light REE and Ba which causes spectral interferences in the heavy REE measurement was effectively attenuated, compared to conventional solution nebulization ICP-MS. To evaluate the applicability of the proposed method, the REE-adsorbed particles prepared by immersing them in a U-bearing solution were measured with LA-ICP-MS. Additionally, each concentration of REE in the U standard solution was determined with solution nebulization ICP-MS. The chondrite-normalized plot obtained through LA-ICP-MS analysis exhibited close agreement with that obtained through the solution nebulization ICP-MS of the REE-separated solution within the uncertainties.
Someya, Takaaki*; Asai, Shiho; Fujiwara, Kunio*; Sugo, Takanobu*; Umeno, Daisuke*; Saito, Kyoichi*
Nippon Kaisui Gakkai-Shi, 69(1), p.42 - 48, 2015/02
A large amount of seriously contaminated sea water with radioactive Cs has been reserved in semi-enclosed coastal sea area which is separated by silt fences and embankments. Insoluble cobalt ferrocyanide (Co-FC) microparticles-impregnated fiber was developed for removing Cs from the contaminated sea water. The resultant Co-FC-impregnated fiber was immersed in either nonradioactive or radioactive Cs solution. The adsorption isotherm well correlated with a Langmuir-type equation. In addition, mass-transfer capacity coefficients were determined by fitting the experimental data of the rate of Cs adsorption onto the Co-FC-impregnated fiber to theoretical adsorption curves based on the Cs concentration difference between the bulk and the interface in seawater as a driving force of the overall adsorption rate. Decontamination factors as functions of fiber weight and the contact time required for the removal of cesium ions from the contaminated seawater in a closed area were estimated.
Haraga, Tomoko; Saito, Shingo*; Sato, Yoshiyuki; Asai, Shiho; Hanzawa, Yukiko; Hoshino, Hitoshi*; Shibukawa, Masami*; Ishimori, Kenichiro; Takahashi, Kuniaki
Analytical Sciences, 30(7), p.773 - 776, 2014/07
A simple and rapid method with low radiation exposure risk was developed for the determination of neodymium in spent nuclear fuel by CE with LIF detection using a fluorescent ligand having a macrocyclic hexadentate polyaminocarboxylate structure. The concentration of Nd(III) in a spent nuclear fuel sample was determined with no interference from various matrix elements, including lanthanides and uranium (at a 200-fold excess), with 92 3% recovery. This is due to method's high resolution based on establishing a ternary complex equilibrium during migration in which the hydroxyl ion plays an auxiliary role.
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
Bunseki, 2013(6), p.316 - 321, 2013/06
no abstracts in English
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
Asai, Shiho; Toshimitsu, Masaaki; Hanzawa, Yukiko; Suzuki, Hideya; Shinohara, Nobuo; Inagawa, Jun; Okumura, Keisuke; Hotoku, Shinobu; Kimura, Takaumi; Suzuki, Kensuke*; et al.
Journal of Nuclear Science and Technology, 50(6), p.556 - 562, 2013/06
The Sn content in a spent nuclear fuel solution was determined by ICP-MS for its inventory estimation in high-level radioactive waste. An irradiated UO fuel was used as a sample to evaluate the reliability of the methodology. Prior to the measurement, Sn was separated from Te, which causes major isobaric interference in the determination of Sn content, along with highly radioactive coexisting elements using an anion-exchange column. The absence of counts attributed to Te in the Sn-containing effluent indicates that Te was completely removed. After washing, Sn retained on the column was readily eluted with 1 M HNO. The isotope ratios of Sn were successfully determined and showed good agreement with those obtained through ORIGEN2 calculations. The results reported in this paper are the first experimental values of Sn content in the spent nuclear fuel solution originating in spent nuclear fuel irradiated at a nuclear power plant in Japan.
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
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.