March 2025
Progress in Nuclear Science and Technology
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Publications (60)
March 2025
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1 Read
Progress in Nuclear Science and Technology
March 2025
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9 Reads
Progress in Nuclear Science and Technology
March 2025
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2 Reads
Progress in Nuclear Science and Technology
March 2025
Progress in Nuclear Science and Technology
November 2024
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1 Read
ECS Meeting Abstracts
Spent nuclear fuels are generated with the operation of nuclear power generation. The process of recovering nuclear fuel materials from spent nuclear fuels is called reprocessing, and through this reprocessing, nuclear fuel materials are recycled as nuclear fuel. The main reprocessing methods are wet reprocessing and pyro reprocessing. Molten salt electrolysis is used for the pyro reprocessing methods. In pyro reprocessing methods, salt bath is used repeatedly, as a result, ultimately spent salt containing a small amount of nuclear fuel materials is generated. In terms of nuclear material management, the nuclear fuel materials must be isolated and recovered. Therefore, we propose a nuclear fuel material recovery process that combines a precipitation method and a distillation method. However, it has been suggested that spent salt is contaminated by other radioactive materials derived from nuclear reactors, fuel structural materials, and molten salt electrolyzers used in pyro reprocessing. In this study, the behavior of these radioactive substances during precipitate formation was estimated. LiCl–KCl eutectic salt or NaCl–2CsCl salt was placed in a quartz tube in an Ar circulation glove box (GB). 10 wt% of MnCl 2 or CoCl 2 was added to the salt bath. The precipitant Li 2 O was added at stoichiometric amounts of 50 %, 100 %, 150 %, and 200 % relative to the amount of Mn(II) or Co(II), respectively. The quartz tube was placed in an electric furnace inside the GB and heated at 700 ℃ in the LiCl–KCl bath and 800 ℃ in the NaCl–2CsCl bath to melt the sample. After the sample was naturally cooled and solidified in the quartz tube, the precipitate and supernatant salt were collected. The precipitate was crushed, washed with pure water, and mixed with BN after drying. The mixture was formed into pellets and subjected to XAFS measurement. XAFS measurements were performed with KEK PF BL-27B, AichiSR BL5S1, and SPring-8 BL22XU. A portion of the supernatant salt was collected, dissolved in pure water, and analyzed using ICP-OES and AAS. The amount of Mn(II) or Co(II) contained and the constituent elements of the salt bath was determined from the analysis results, and the precipitation ratio was calculated. In addition, the reactions assumed in the experiment were evaluated by simulating the precipitation ratio using the thermodynamic database MALT and the multi-element chemical equilibrium calculation software gem. The precipitation ratio is shown in Figure 1 (left). The precipitation ratio of Mn(II) and Co(II) tended to increase as the amount of precipitant added increased. Both Mn(II) and Co(II) tended to increase up to 150 %, but there was no significant difference between 150 and 200 %. It is thought that the chloride produced an oxide precipitate by adding the precipitant. Theoretically, the precipitation ratio would increase to around 100 % if the amount of precipitant added was 100 %, but it was less than 80 % for both Mn(II) and Co(II). There are two possible reasons. One is that O ions derived from Li 2 O have the property of dissolving in salt bath, so there is a possibility that some of the precipitate will be dissolved in the salt bath. The other reason is that the total amount of Li 2 O added did not react with Mn(II) and Co(II), and a portion of it was dissolved in the salt bath. Furthermore, between Mn(II) and Co(II), the precipitation ratio of Co(II) tended to be higher. This is thought to be due to the fact that Co(II) reacts more easily with the precipitant than Mn(II). Therefore, in a mixed system, it is assumed that Co(II) precipitates first. Figure 1 (right) is the EXAFS radial structure functions of the Co(II) precipitate and the control sample. In the EXAFS radial structure function, not only the first neighborhood structural peak of the Co-O bond at approximately 1.8 Å coincided with the precipitate, but also the correlations at longer distances showed almost the same behavior. From this, it is assumed that the precipitate is CoO. In the presentation, we also plan to explain Fe(III) and Ni(II). As a result of the experiment, it was found that Mn(II) and Co(II) were recovered as oxides. Since the goal is to recover nuclear fuel materials as oxides, Mn(II) and Co(II) are likely to be entrained in the nuclear fuel materials. Therefore, we believe that it is necessary to add a process to separate Mn(II) and Co(II) from nuclear fuel materials. Figure 1
November 2024
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14 Reads
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
November 2024
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3 Reads
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
September 2024
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7 Reads
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
September 2024
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5 Reads
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
Citations (26)
... Hence, these radioisotopes should be removed from the radioactive wastewater to protect humans and the environment. Adsorption [16,17], column [18], impregnation [19], ion exchange [20], and membrane [21] are among the technologies used to remove different ions from wastewater. Adsorption is a cost-effective and highly operative method when accurate adsorbents are used in an adsorption-friendly environment. ...
- Citing Article
September 2023
Nuclear Engineering and Technology
... In this case, the light can be collected and analysed, i.e., ion-beam-induced luminescence or ionoluminescence (IL) method can be utilized as an analytical tool. Luminescence methods are commonly related to light emission from the ultraviolet (UV) to infrared (IR) spectral region, including also the visible range, and show both broad [7,8] and narrow band spectra emitted by optically active centres [9,10]. In the luminescence process, the emission of light is due to electronic excitations by various external factors. ...
- Citing Article
September 2023
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
... Confining of the organic liquid wastes into a chemically stable matrix might be appropriate for organic compounds that are challenging to be mineralized or release hazardous compounds by decomposition operation. We focus on organic liquid waste solidification with a geopolymer [44], and the feasibility of geopolymer solidification for spent solvents is evaluated using a simulated spent solvent. ...
- Citing Article
July 2023
Journal of Nuclear Materials
... Co., Ltd., Japan), and porous silica bead (particle size is 40-75 µm, mean pore size is 50 nm, FUJI SYLISIS CHEMICAL Ltd, Japan) was selected. The porous silica bead was same bead on previous studies about MA recovery operation [2,11,12]. ...
- Citing Article
March 2023
Applied Radiation and Isotopes
... Hexaoctyl-nitrilotriacetamide (HONTA) impregnated adsorbents are used for the 2nd columns owing to its selectivity for MA(III) (Sasaki et al., 2013) and excellent adsorption/desorption performance of the HONTA impregnated adsorbent (Takeuchi et al., 2019;Watanabe et al., 2018b). Our preliminary experiments showed that selective MA(III) recovery is possible even though several modifications have to be made in the process flow for more efficient separation (Akuzawa et al., 2022). In the previous phase, CMPO and HDEHP have been used for MA(III)+RE(III) co-recovery and MA(III)/RE(III) separation, respectively (Watanabe et al., 2018a;Watanabe et al., 2019a). ...
- Citing Article
December 2022
Journal of Radioanalytical and Nuclear Chemistry
... 36 The impregnation of the hydrophobic extractant in the polymer layer caused the increase in the pK a due to the increase in the hydrophobicity. 37 Because the polymer layer containing HONTA molecules is more hydrophobic, the 1:3 complex tends to be distributed to the polymer layer to react with HONTA. Therefore, the increase in C NO3¹ promotes the 1:3 complexes of Eu(III) and Sm(III), resulting in the increase in the K L . ...
- Citing Article
February 2022
Bulletin of the Chemical Society of Japan
... Based on the above adsorbents, this study proposes two MAREC (extraction chromatography for recovering trace actinide elements from high-level radioactive waste) processes [54]. One is a two-step process in which MA(III) and Ln(III) are co-separated from higher-acid HLLW using CMPO/SiO 2 -P or TODGA/SiO 2 -P, and the adsorbed MA(III) and Ln(III) can be desorbed by water. ...
- Citing Article
- Full-text available
October 2021
Journal of Radioanalytical and Nuclear Chemistry
... Our study has shown that Co 2+ and Clcan be combined to work as catalysts, and ammonium ions in nitric acid solutions can be decomposed into N 2 gas through NH 2 Cl [23,24]. Coexisting chemical species influence the efficiency of the reaction, and separating NH 4 + is essential for efficient decomposition with catalysis. ...
- Citing Article
September 2021
Progress in Nuclear Energy
... The design of adsorbents for hazardous chemicals removal is in progress. Studies for the salt treatment have already been started from the previous phase, and combining purification and solidification of the salts is a promising procedure [34]. Here, an overview of the laboratories and study programs for organic wastes treatment are shown. ...
- Citing Article
July 2021
Journal of Nuclear Materials
... The neutron transmission spectra below several tens meV (longer than several angstroms) are analyzed in Bragg edge imaging, while the spectra above several eV provide information on elemental composition of a sample, especially at resonance energies. Resonance absorption imaging visualizes an element's spatial distribution, only analyzing the transmission spectrum (dip) around its resonance energy [3][4][5][6][7][8][9][10] . Although high sensitivity is brought about at resonance energies, measurements take a long time to obtain statistical accuracy due to the narrow energy width of resonances. ...
- Citing Conference Paper
- Full-text available
March 2021
