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Journal Articles

Design of microchannel suitable for packing with anion exchange resins; Uranium separation from seawater containing a large amount of cesium

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.

Journal Articles

Determination of $$^{135}$$Cs/$$^{137}$$Cs isotopic ratio in soil collected near Fukushima Daiichi Nuclear Power Station through mass spectrometry

Shimada, Asako; Tsukahara, Takehiko*; Nomura, Masao*; Kim, M. S.*; Shimada, Taro; Takeda, Seiji; Yamaguchi, Tetsuji

Journal of Nuclear Science and Technology, 58(11), p.1184 - 1194, 2021/11

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Determining the completeness of nuclear reactor decommissioning is an important step in safely utilizing nuclear power. For example, $$^{137}$$Cs from the Fukushima Daiichi Nuclear Power Station (FDNPS) accident can be treated as background radioactivity, so determining the origin of $$^{137}$$Cs is essential. To accomplish this, measuring the $$^{135}$$Cs/$$^{137}$$Cs isotope ratio can be useful, so this study optimized a solvent extraction method, with calix[4]arene-bis(t-octylbenzo-crown-6) [BOBCalixC6] in 1-octanol, to purify radioactive Cs, radiocesium, from a solution of major environmental soil elements and mass spectrometry interference elements. This optimized method was applied to Cs purification in soil samples (40 g), and the final solutions contained a total of 10$$mu$$g/ml of the major soil elements and ng/ml concentrations at most of interfering elements. Soil samples collected near the FDNPS were then purified, and the $$^{135}$$Cs/$$^{137}$$Cs isotope ratios were measured, using both thermal ionization mass spectrometry (TIMS) and triple quadrupole induced coupled plasma mass spectrometry (ICP-QQQ). The results of each of these measurements were compared, and we found that Cs isotope ratios obtained by TIMS were more precise, by an order of magnitude, while the ICP-QQQ results possessed good abundance sensitivities. A slightly higher $$^{135}$$Cs/$$^{137}$$Cs ratio in the northwest area of the FDNPS was observed, while other areas exhibited similar values, all within the measurement error range, which indicated different origins of radiocesium. These results agreed with previously reported $$^{134}$$Cs/$$^{137}$$Cs activity distributions, suggesting that this ratio may be useful in identifying radiocesium origins for evaluating future nuclear reactor decommissions.

Journal Articles

No secondary waste recycle technology for rare metals using the hydrophilic extraction with phase transfer phenomena

Tsukahara, Takehiko*; Saga, Kaname*; Suzuki, Hideya*; Matsumura, Tatsuro

Kurin Tekunoroji, 29(12), p.4 - 7, 2019/12

no abstracts in English

Oral presentation

$$^{135}$$Cs/$$^{137}$$Cs isotope ratio near the Fukushima Daiichi Nuclear Power Station

Shimada, Asako; Tsukahara, Takehiko*; Nomura, Masao*; Shimada, Taro; Takeda, Seiji

no journal, , 

no abstracts in English

Oral presentation

Development of dose evaluation method for confirmation of completion of decommissioning, 2; Identification of radiocesium origin using $$^{135}$$Cs/$$^{137}$$Cs isotope ratio

Shimada, Asako; Tsukahara, Takehiko*; Nomura, Masao*; Kim, M. S.*; Shimada, Taro; Takeda, Seiji; Yamaguchi, Tetsuji

no journal, , 

Radiocesium from the Fukushima Daiichi Nuclear Power Station (1F) accident can be treated as background radioactivity at completion of decommissioning, so determining the origin of radiocesium is essential. Therefore, we studied identification of radiocesium origin using $$^{135}$$Cs/$$^{137}$$Cs isotope ratio. The ratio originated from 1F was 0.3628$$pm$$0.0005. When the ratio originated from decommissioning facility was 0.05$$sim$$0.2 larger than that originated from 1F, it is challenging to decrease the stand deviation less than 0.01 for 1 Bq/g of $$^{137}$$Cs because precision was decreased as decreasing the $$^{137}$$Cs concentration. If the ratio is able to be determined within the standard deviation of 0.0005 for 0.5 Bq/g of soil sample, the identification would be available.

Oral presentation

Development of analytical method of $$^{135}$$Cs/$$^{137}$$Cs isotope ratio in environmental soil samples

Shimada, Asako; Kim, M. S.*; Tsukahara, Takehiko*; Nomura, Masao*; Shimada, Taro; Takeda, Seiji; Yamaguchi, Tetsuji

no journal, , 

no abstracts in English

Oral presentation

Development of microscale separation technique for uranium

Ouchi, Kazuki; Muto, Yuki*; Brandt, A.*; Nabatame, Nozomi*; Tsukahara, Takehiko*; Kitatsuji, Yoshihiro

no journal, , 

The adsorption and elution performance of uranium with the microchip column (length 11 mm, column volume 0.39 $$mu$$L) loaded an anion exchange resin for faster and safer radioactive waste analysis were investigated. When a mixed sample of lanthanides and uranium was flown on the microchip column at the feed rate of 1 ml h$$^{-1}$$, uranium could be selectively adsorbed and eluted in about 4 minutes of operation time. This was faster than a conventional column which took several tens of minutes. When this column was applied to uranium separation of the standard seawater, the uranium concentration was determined to be 2.86$$pm$$0.05 ppb, which was in good agreement with the certified value (2.81$$pm$$0.16 ppb). Therefore, the verification test was successful.

Oral presentation

Basic research programs of vitrification technology for waste volume reduction, 96; Development of on-line monitoring technique of target elements for chromatographic valve control

Tsukahara, Takehiko*; Brandt, A.*; Watanabe, So; Sano, Yuichi; Takeuchi, Masayuki

no journal, , 

no abstracts in English

Oral presentation

Evaluation of remaining spent extraction solvent in vermiculite by PIXE analysis

Arai, Yoichi; Watanabe, So; Hasegawa, Kenta; Okamura, Nobuo; Watanabe, Masayuki; Takeda, Keisuke*; Fukumoto, Hiroki*; Ago, Tomohiro*; Hagura, Naoto*; Tsukahara, Takehiko*

no journal, , 

Oral presentation

Design and performance evaluation of microchannel for packing with aion-exchange resins

Ouchi, Kazuki; Tsukahara, Takehiko*; Brandt, A.*; Muto, Yuki*; Nabatame, Nozomi*; Koma, Yoshikazu; Kitatsuji, Yoshihiro

no journal, , 

We designed microchannel for packing with aion-exchange resins that can reduce the radiation exposure risk and the secondary radioactive wastes during uranium (U) separation. Two types of microchips were designed to densely pack the microchannels with resins. The microchannels had almost the same cross-sectional area, but different outer circumferences. A satisfactory separation performance could be obtained by arranging more than ca. 10 resins along the depth and width of the microchannels. The separation performance of the microchannel was evaluated using the seawater standard added Cs-133 as a reference of 1F retained water. The measured value of U in the seawater sample was in good agreement with the certified value. These results indicate that a resin-packed microchannel is suitable for determining the U from highly concentrated matrix elements.

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