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Journal Articles

Selective Pd separation from simulated radioactive liquid waste by precipitation using xenon lamp irradiation for a simplified procedure

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 $$^{107}$$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$$^{-1}$$ HNO$$_{3}$$ 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 $$^{107}$$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.

Journal Articles

Radiation dose rate effects on the properties of a laser-induced breakdown spectroscopy system developed using a ceramics micro-laser for fiber-optic remote analysis

Tamura, Koji; Oba, Hironori; Saeki, Morihisa; Taguchi, Tomitsugu*; Lim, H. H.*; Taira, Takunori*; Wakaida, Ikuo

Journal of Nuclear Science and Technology, 58(4), p.405 - 415, 2021/04

 Times Cited Count:1 Percentile:39.17(Nuclear Science & Technology)

Radiation dose rate effects on the properties of a compact fiber-optic laser-induced breakdown spectroscopy (LIBS) system with a monolithic Nd:YAG/Cr:YAG composite ceramics were investigated for remote analysis in hazardous environment. To investigate radiation effects on the LIBS signal, properties related to the Nd:YAG laser operation such as oscillation threshold, output energy, oscillation timing, temporal pulse shape, and beam profile were measured as a function of the radiation dose rate from 0 to 10 kGy/hr in view of their influences to the signal. LIBS spectra of zirconium metal were measured under irradiation. Although signal intensity decreased considerably by irradiation, informative spectra were well obtained even at the maximum radiation dose rate. From the comparison of the LIBS-related parameters among the laser properties, signal reduction was mainly ascribed to the pulse energy reduction. Scintillation emission spectra were also measured from the ceramics during the irradiation, where the signal intensity increased linearly with the dose rate. The results show that the developed system.

Journal Articles

Highly sensitive detection of sodium in aqueous solutions using laser-induced breakdown spectroscopy with liquid sheet jets

Nakanishi, Ryuzo; Oba, Hironori; Saeki, Morihisa; Wakaida, Ikuo; Tanabe, Rie*; Ito, Yoshiro*

Optics Express (Internet), 29(4), p.5205 - 5212, 2021/02

 Times Cited Count:0 Percentile:0(Optics)

Laser-induced breakdown spectroscopy (LIBS) combined with liquid jets was applied to the detection of trace sodium (Na) in aqueous solutions. The sensitivities of two types of liquid jets were compared: a liquid cylindrical jet with a diameter of 500 $$mu$$m and a liquid sheet jet with a thickness of 20 $$mu$$m. Compared with the cylindrical jet, the liquid sheet jet effectively reduced the splash from the laser-irradiated surface and produced long-lived luminous plasma. The limit of detection (LOD) of Na was determined to be 0.57 $$mu$$g/L for the sheet jet and 10.5 $$mu$$g/L for the cylindrical jet. The LOD obtained for the sheet jet was comparable to those obtained for commercially available inductively coupled plasma emission spectrometers.

Journal Articles

Application of an augmentation method to MCR-ALS analysis for XAFS and Raman data matrices in the structural change of isopolymolybdates

Saeki, Morihisa*; Yomogida, Takumi; Matsumura, Daiju; Saito, Takumi*; Nakanishi, Ryuzo*; Tsuji, Takuya; Oba, Hironori*

Analytical Sciences, 36(11), p.1371 - 1378, 2020/11

 Times Cited Count:0 Percentile:0(Chemistry, Analytical)

We measured X-ray absorption fine structure (XAFS) and Raman spectra of isopolymolybdates(VI) in HNO$$_{3}$$ solution (0.15- 4.0 M), which change their geometries depending on acid concentration, and performed simultaneous resolution of the XAFS and Raman data using a multivariate curve resolution by alternating least-squares (MCR-ALS) analysis. In iterative ALS optimization, initial data matrices were prepared by two different methods. The MCR-ALS result of single XAFS data matrix shows large dependence on the preparation method of the initial data matrices. The MCR-ALS result of an augmented matrix of Raman and XAFS data has little dependence on the initial data matrices. It indicates that the augmentation method effectively improves the rotation ambiguities in the MCR-ALS analysis of the XAFS data. Based on the model fitting of the pure EXAFS oscillations, we revealed the change of [Mo$$_{36}$$O$$_{112}$$(H$$_{2}$$O)$$_{16}$$]$$^{2+}$$ $$rightarrow $$ [Mo$$_{2}$$O$$_{5}$$(H$$_{2}$$O)$$_{6}$$]$$^{2+}$$ $$rightarrow $$ [HMoO$$_{3}$$(H$$_{2}$$O)$$_{3}$$]$$^{+}$$ in the highly concentrated HNO$$_{3}$$ solution.

Journal Articles

Extractions and spectroscopic studies of various metals with Diglycolamide-Type Tridentate Ligands

Sasaki, Yuji; Saeki, Morihisa*; Yoshizuka, Kazuharu*

Solvent Extraction Research and Development, Japan, 26(1), p.21 - 34, 2019/06

 Times Cited Count:5 Percentile:43.69(Chemistry, Multidisciplinary)

Three tridentate extractants and three masking reagents including O, N, and S donors have been developed and their properties are compared and discussed. The extractants are termed as tetraoctyl-diglycolamide (TODGA), methylimino-dioctylacetamide (MIDOA) and tetraoctyl-thiodiglycolamide (TDGA(C8)) and masking agents have the same central frame but with short alkyl chain. The results of the present study indicate that TODGA can extract mainly hard acid metals belonging groups 2-4,13-15 in periodic table, MIDOA can extract soft acid metals and oxyanions (groups 5-10, 16), and TDGA can extract soft acid metals (groups 10-11). Some spectrophotometric studies (UV, IR, and NMR) indicate the stoichiometry and effect of donor atoms for metal-complexation. The Hf values, the heat generation during complex formation, obtained by chemical calculation by DFT theory show the reverse-correlation with their extraction ability.

Journal Articles

Determination of $$^{107}$$Pd in Pd purified by selective precipitation from spent nuclear fuel by laser ablation ICP-MS

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

 Times Cited Count:5 Percentile:57.47(Biochemical Research Methods)

Determination of radiopalladium $$^{107}$$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 $$^{107}$$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, $$^{102}$$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 $$^{107}$$Pd/$$^{102}$$Pd. The amount of $$^{107}$$Pd obtained by LA-ICP-MS corresponds to the values obtained by conventional solution nebulization measurement.

Journal Articles

In Situ Time-Resolved XAFS Studies on Laser-induced Particle Formation of Palladium Metal in an Aqueous/EtOH solution

Saeki, Morihisa*; Matsumura, Daiju; Yomogida, Takumi; Taguchi, Tomitsugu*; Tsuji, Takuya; Saito, Hiroyuki*; Oba, Hironori*

Journal of Physical Chemistry C, 123(1), p.817 - 824, 2019/01

 Times Cited Count:6 Percentile:37.24(Chemistry, Physical)

Reaction kinetics of laser-induced particle formation in an aqueous solution of PdCl$$_{4}$$$$^{2-}$$ was investigated by transmission electron microscope (TEM) and dispersive X-ray absorption fine structure (DXAFS). The Pd particle was generated by irradiation of nanosecond pulsed 266-nm laser. The TEM observation showed dependence of the particle size on the laser fluence and promotion of the particle growth by irradiation of high-fluence laser. The DXAFS data give us the Pd$$^{2+}$$ concentration. Temporal changes of the Pd$$^{2+}$$ concentration analyzed based on Finke-Watzky two step mechanism. The analysis elucidates that the laser photon contributes to the reduction of the PdCl$$_{4}$$$$^{2-}$$ ion by the one-photon process and to the autocatalytic growth of the Pd particles by the multi-photon process.

Journal Articles

Laser-induced breakdown spectroscopy and related resonance spectroscopy for nuclear fuel cycle management and for decommissioning of "Fukushima Daiichi Nuclear Power Station"

Wakaida, Ikuo; Oba, Hironori; Miyabe, Masabumi; Akaoka, Katsuaki; Oba, Masaki; Tamura, Koji; Saeki, Morihisa

Kogaku, 48(1), p.13 - 20, 2019/01

By Laser Induced Breakdown Spectroscopy and by related resonance spectroscopy, elemental and isotope analysis of Uranium and Plutonium for nuclear fuel materials and in-situ remote analysis under strong radiation condition for melt downed nuclear fuel debris at damaged core in "Fukushima Daiichi Nuclear Power Station", are introduced and performed as one of the application in atomic energy research field.

Journal Articles

Development of separation technique for platinum group metals from radioactive liquid waste utilizing laser-induced particulate formation

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.

Journal Articles

Metal extractions by diglycolamide-type tridentate ligands

Sasaki, Yuji; Morita, Keisuke; Saeki, Morihisa*; Hisamatsu, Shugo*; Yoshizuka, Kazuharu*

Proceedings of 21st International Solvent Extraction Conference (ISEC 2017) (Internet), p.131 - 134, 2017/11

Three tridentate extractants including soft and hard donor has been developed and examined. The extractants are termed as $$N, N, N', N'$$-tetraoctyl-diglycolamide (TODGA), methylimino-$$N, N'$$-dioctylacetamide (MIDOA) and $$N, N, N', N'$$-tetraoctyl-thiodiglycolamide (TDGA). The results of the present study show that TODGA can extract completely lanthanides and actinides, MIDOA can extract palladium, technetium, and rhenium, and TDGA can extract palladium, silver, and gold. We can compare the distribution ratios of these metals by TODGA, MIDOA, and TDGA. These results can be supported by some spectrometric studies, i.e., IR, NMR and UV, and calculations of metal complexes.

Journal Articles

Non-contact and selective Pd separation based on laser-induced photoreduction for determination of $$^{107}$$Pd by ICP-MS; The Relation between separation conditions and Pd recovery

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

 Times Cited Count:1 Percentile:5.18(Chemistry, Analytical)

Palladium-107 is a long-lived fission product, which can be found in high-level radioactive liquid wastes (HLLW). Determination of the $$^{107}$$Pd contents in HLLW is essential to evaluate the long-term safety of HLLW repositories. However, the $$^{107}$$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$$^{-1}$$, showing the applicability of the proposed separation technique to HLLW samples.

Journal Articles

Study on laser-induced particle formation of palladium ion by time-resolved X-ray spectroscopy

Saeki, Morihisa*; Taguchi, Tomitsugu*; Oba, Hironori*; Matsumura, Daiju; Tsuji, Takuya; Yomogida, Takumi

Denki Gakkai Kenkyukai Shiryo, Denshi Zairyo Kenkyukai (EFM-17-010$$sim$$021), p.15 - 18, 2017/09

Irradiation of nanosecond pulsed UV laser into a solution of palladium ion leads to formation of palladium particles with sub-micron size particles by time-resolved X-ray absorption spectroscopy.

Journal Articles

Precious metal extraction by N,N,N',N'-tetraoctyl-thiodiglycolamide and its comparison with N,N,N',N'-tetraoctyl-diglycolamide and methylimino-N,N'-dioctylacetamide

Sasaki, Yuji; Morita, Keisuke; Saeki, Morihisa*; Hisamatsu, Shugo; Yoshizuka, Kazuharu*

Hydrometallurgy, 169, p.576 - 584, 2017/05

 Times Cited Count:10 Percentile:59.14(Metallurgy & Metallurgical Engineering)

The novel tridentate extractant including soft donor has developed and examined. The extractant, tetraoctyl-thiodiglycolamide (TDGA), is analogous structure to tetraoctyl-diglycolamide (TODGA) and methylimino-dioctylacetamide (MIDOA), but with sulfur donor instead of ether oxygen or nitrogen atoms of TODGA or MIDOA. From the present work, TDGA can extract silver, palladium, gold, and mercury from acidic solutions to n-dodecane. In addition to these results, the distribution ratios of hard and soft acid metals by using TDGA, TODGA, and MIDOA are compared, where the metal-complexations with each donor atom are investigated. 1H-NMR and IR studies for the metal-TDGA complexes indicate the role on donor atoms, S and N, of TDGA.

Journal Articles

Determination of $$^{107}$$Pd in Pd recovered by laser-induced photoreduction with inductively coupled plasma mass spectrometry

Asai, Shiho; Yomogida, Takumi; Saeki, Morihisa*; Oba, Hironori*; Hanzawa, Yukiko; Horita, Takuma; Kitatsuji, Yoshihiro

Analytical Chemistry, 88(24), p.12227 - 12233, 2016/12

 Times Cited Count:10 Percentile:47.49(Chemistry, Analytical)

Safety evaluation of a radioactive waste repository requires credible activity estimates confirmed by actual measurements. A long-lived radionuclide, $$^{107}$$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 $$^{107}$$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 $$^{107}$$Pd.

Journal Articles

Studies on the extraction of soft acid metal species using MIDOA and analogous compounds

Sasaki, Yuji; Saeki, Morihisa; Sugo, Yumi; Ikeda, Yasuhisa*; Kawasaki, Takeshi*; Suzuki, Tomoya*; Ohashi, Akira*

Solvent Extraction Research and Development, Japan, 22(1), p.37 - 45, 2015/05

 Times Cited Count:9 Percentile:37.92(Chemistry, Multidisciplinary)

An extractant, methylimino-bis-${it N,N'}$-dioctylacetamide (MIDOA), was used for the extraction of soft acid metals. It was found that MIDOA can extract not only Cr(VI), Mo(VI), W(VI), Tc(VII) and Re(VII), whose metals can form the oxonium anions due to their high oxidation states, but also other metal cations, like Nb(V), Ta(V) and Pd(II). Analogous compounds, imino-bis-${it N,N'}$-dioctylacetamide (IDOA) and methylimino-bis-${it N,N'}$-di-2-ethylhexylacetamide (MIDEHA), are synthesized and compared for their extractability. It is clear that these extractants have almost same or lower $$D$$ values than those for MIDOA. In order to examine the effect on extractability with different donor atoms, TODGA (${it N,N,N',N'}$-tetraoctyl-diglycolamide) and TDGA (${it N,N,N',N'}$-tetraoctyl-tyiodiglycolamide) having oxygen and sulfur donor are employed. The comparison of their extractabilities suggests that the trend of Pd and Re extraction is N $$>$$ S $$>$$ O and N $$>$$ O $$>$$ S, respectively.

Journal Articles

Wet separation between palladium(II) and molybdenum(IV) ions by using laser-induced particle formation; Enhancement of recovery efficiency of palladium by laser condition

Saeki, Morihisa; Taguchi, Tomitsugu; Nakashima, Nobuaki*; Oba, Hironori

Journal of Photochemistry and Photobiology A; Chemistry, 299, p.189 - 193, 2015/02

 Times Cited Count:7 Percentile:21.94(Chemistry, Physical)

Journal Articles

Application of laser-induced breakdown spectroscopy method for elements analysis of metal ions in an aqueous solution in nuclear reprocessing process control

Oba, Hironori; Saeki, Morihisa; Wakaida, Ikuo

Reza Kenkyu, 42(12), p.892 - 896, 2014/12

Laser-induced breakdown spectroscopy (LIBS) is an attractive technique for determining elemental composition in real time, in-situ and remotely without any sample preparation. The LIBS analysis of metal ions in an aqueous solution is available in process control and environmental monitoring. In the present paper, we have reviewed the LIBS methods for a liquid phase that tried to improve the detection sensitivity. We have performed the LIBS measurement with the sheet flow for the simultaneous determination of elements in the simulated high-level radioactive waste liquid and have discussed on the application possibility as a tool for online process monitoring.

Journal Articles

Effect of liquid-sheet thickness on detection sensitivity for laser-induced breakdown spectroscopy of aqueous solution

Oba, Hironori; Saeki, Morihisa; Wakaida, Ikuo; Tanabe, Rie*; Ito, Yoshiro*

Optics Express (Internet), 22(20), p.24478 - 24490, 2014/10

 Times Cited Count:14 Percentile:66.41(Optics)

For aqueous-solution-based elemental analysis, we used a thin liquid sheet ($$mu$$m-scale thickness) in laser-induced breakdown spectroscopy with nanosecond laser pulses. Laser-induced plasma is emitted by focusing a pulsed Nd:YAG laser (1064 nm) on a 5- to 80-$$mu$$m-thick liquid sheet in air. To optimize the conditions for detecting elements, we studied how the signal-to-background ratio (SBR) for H$$alpha$$ Balmer and Na-neutral emission lines depends on the liquid-sheet thickness. The SBR of the H$$alpha$$ Balmer and Na-neutral lines was maximized for a sheet thickness of $$sim$$20 $$mu$$m at the laser energy of 100 mJ. The hydrodynamics of liquid flow induced by the laser pulse was analyzed by laser flash shadowgraph imaging. Time-resolved observation of the hydrodynamics and plasma emission suggests that the dependence of the SBR on the liquid-sheet thickness is correlated with the volume of flowing liquid that interacts with the laser pulses.

Journal Articles

Development of a fiber-coupled laser-induced breakdown spectroscopy instrument for analysis of underwater debris in a nuclear reactor core

Saeki, Morihisa; Iwanade, Akio; Ito, Chikara; Wakaida, Ikuo; Thornton, B.*; Sakka, Tetsuo*; Oba, Hironori

Journal of Nuclear Science and Technology, 51(7-8), p.930 - 938, 2014/07

 Times Cited Count:49 Percentile:98.47(Nuclear Science & Technology)

To inspect post-accident nuclear core reactor of the TEPCO Fukushima Daiichi Nuclear Power Plant, a transportable fiber-coupled LIBS instrument was developed. The developed LIBS instrument was designed to analyze the underwater sample in high-radiation field by single-pulse breakdown with gas flow or double-pulse breakdown. To check the feasibility of the assembled fiber-coupled LIBS instrument to the inspection inside Fukushima Daiichi Nuclear Power Plant, we investigated (1) influence of radiation dose on optical transmittance of the laser delivery fiber, (2) survey of the LIBS techniques to analyze the underwater sample and (3) candidates of emission lines for analysis of the debris. By employing the selected emission lines, we demonstrated that the developed LIBS instrument can analyze the simulated debris underwater by the single-pulse breakdown with the gas flow with high signal to noise ratio.

Journal Articles

In-vessel inspection probing technique using optical fibers under high radiation dose

Ito, Chikara; Naito, Hiroyuki; Oba, Hironori; Saeki, Morihisa; Ito, Keisuke; Ishikawa, Takashi; Nishimura, Akihiko; Wakaida, Ikuo; Sekine, Takashi

Proceedings of 22nd International Conference on Nuclear Engineering (ICONE-22) (DVD-ROM), 7 Pages, 2014/07

A high-radiation resistant optical fiber has been developed in order to investigate the interiors of the reactor pressure vessels and the primary containment vessels of the Fukushima Daiichi Nuclear Power Station. The radiation resistance of an optical fiber was improved by increasing the amount of hydroxyl up to 1000 ppm in pure silica fiber. The improved image fiber consists of common cladding and a large number of fiber cores made from pure silica that contains 1000 ppm hydroxyl. The transmissive rate of an infrared image was not affected after the irradiation of 1 MGy. We have developed the fiber-coupled LIBS system to detect plasma emission efficiently in near-infrared region. In addition, we have performed a $$gamma$$ ray dose rate measurement using an optical fiber of which scintillator is attached to the tip. As a result, the concept of applicability of a probing system using the high-radiation resistant optical fibers has been confirmed.

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