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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

https://doi.org/10.1080/00223131.2021.1931520
 Times Cited Count：8 Percentile：63.53(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

Direct quantitation of $$^{135}$$Cs in spent Cs adsorbent used for the decontamination of radiocesium-containing water by laser ablation inductively coupled plasma mass spectrometry

Asai, Shiho*; Ohata, Masaki*; Hanzawa, Yukiko; Horita, Takuma; Yomogida, Takumi; Kitatsuji, Yoshihiro

Analytical Chemistry, 92(4), p.3276 - 3284, 2020/02

https://doi.org/10.1021/acs.analchem.9b05161
 Times Cited Count：7 Percentile：28.35(Chemistry, Analytical)

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 $$^{135}$$Cs content prior to final disposal. $$^{135}$$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 $$^{137}$$Cs. To address this challenge, we herein employed laser ablation ICP-MS for direct quantitation of $$^{135}$$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 $$^{135}$$Cs/$$^{137}$$Cs ratio and $$^{137}$$Cs radioactivity obtained by gamma spectrometry achieved simple and precise quantitation of $$^{135}$$Cs and the resulting $$^{135}$$Cs activity of 0.36 Bq agreed well with that in the original radiocesium-containing liquid waste.

Journal Articles

Measurement of long-lived nuclides by multi-$$gamma$$ ray analysis

Hatsukawa, Yuichi; Toh, Yosuke; Oshima, Masumi; Hayakawa, Takehito; Shinohara, Nobuo; Kushita, Kohei; Ueno, Takashi

KEK Proceedings 2001-14, p.193 - 194, 2001/06

no abstracts in English

Journal Articles

Thermal neutron cross section and resonance integral of the reaction of $$^{135}$$Cs(n,$$gamma$$)$$^{136}$$Cs; Fundamental data for the transmutation of nuclear waste

Hatsukawa, Yuichi; Shinohara, Nobuo; ; Kobayashi, Katsutoshi; Motoishi, Shoji; Tanase, Masakazu; ; ; Harada, Hideo*

Journal of Radioanalytical and Nuclear Chemistry, 239(3), p.455 - 458, 1999/00

https://doi.org/10.1007/BF02349050
 Times Cited Count：2 Percentile：75.00(Chemistry, Analytical)

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 chemical separation method for the measurement of $$^{135}$$Cs/$$^{137}$$Cs isotopic ratio in environmental samples

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

no journal, , 

Although identification of radiocesium in environmental samples is commonly performed by using $$^{134}$$Cs/$$^{137}$$Cs radioactivity ratio, measurement of $$^{134}$$Cs will become challenge in a few decade ago because of short half-life (2 y). Instead of the measurement of $$^{134}$$Cs/$$^{137}$$Cs radioactivity ratio, the measurement of $$^{135}$$Cs/$$^{137}$$Cs isotopic ratio will be effective in future because of long half-life of $$^{135}$$Cs (133 My). In order to measure $$^{135}$$Cs/$$^{137}$$Cs isotopic ratio, Cs must be separated from the matrix of soil. Since 1 Bq of $$^{137}$$Cs is equal to 312.5 fg, large amount of soil have to be treated to extract Cs for the measurement. In the present study, we improved chemical separation method using BOBCalixC6 by optimizing extraction time and reuse of the organic phase. Finally, approximately 170 g of soil sampled at Toka-mura was dissolved and Cs was separate with the developed method to measure $$^{135}$$Cs/$$^{137}$$Cs isotopic ratio.

Oral presentation

Direct measurement of $$^{135}$$Cs in Cs adsorbent used for water decontamination by laser-ablation ICP-MS

Asai, Shiho*; Ohata, Masaki*; Hanzawa, Yukiko; Horita, Takuma; Yomogida, Takumi; Kitatsuji, Yoshihiro

no journal, , 

A large amount of spent Cs adsorbents used for decontaminating water in Fukushima Daiichi Nuclear Power Station are stored in the site. To dispose them safely, the estimation of $$^{135}$$Cs activity along with that of $$^{137}$$Cs is indispensable. $$^{135}$$Cs is generally measured by ICP-MS, which required the sample to be prepared in liquid form and thus the elution of Cs from the Cs adsorbents is essential. However, this approach suffers from the high radiation dose from $$^{137}$$Cs. In this study, we quantified $$^{135}$$Cs in a Cs adsorbent using the $$^{135}$$Cs/$$^{137}$$Cs ratio obtained by LA-ICP-MS and $$^{137}$$Cs radioactivity obtained by gamma spectrometry. To evaluate the applicability, we employed a $$^{135}$$Cs -containing water sample to prepare a model spent Cs adsorbent with a certified $$^{135}$$Cs activity. The resulting $$^{135}$$Cs activity of 0.36 Bq calculated by $$^{135}$$Cs /$$^{137}$$Cs ratio of 0.41 $$pm$$ 0.02 and $$^{137}$$Cs activity agreed well with that of the originally determined $$^{135}$$Cs activity in the model spent Cs adsorbent, demonstrating that the proposed technique has high validity to $$^{135}$$Cs determination of a real sample.

Oral presentation

First measurement of $$^{135}$$Cs/$$^{137}$$Cs isotope ratio in Japanese soil before the accident at the Fukushima Daiichi Nuclear Power Station

Shimada, Asako; Xu, J.*; Tsukahara, Takehiko*; Nomura, Masao*; Takeda, Seiji; Takahashi, Hiroaki*

no journal, , 

Cesium-137 concentration in environmental soil samples near and inside Tokai-mura was exceeded site release standard, 0.1 Bq/g, because of the accident at the Fukushima Daiichi Nuclear Power Station (1F). It is possibly to use the $$^{135}$$Cs/$$^{137}$$Cs isotope ratio to distinguish the $$^{137}$$Cs from the 1F and from decommissioned facility. However, radiocesium from global fallout is also contained in soil and it may be influenced on the $$^{135}$$Cs/$$^{137}$$Cs isotope ratio. There are no data of $$^{135}$$Cs/$$^{137}$$Cs isotope ratio before the 1F accident for soil samples collected in Japan. Therefore, $$^{135}$$Cs/$$^{137}$$Cs isotope ratio in soil samples collected in 2008 y at Tokai-mura was measured to be 2.61$$pm$$0.28 agreed with the result for sampled collected in USA.

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 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

10 (Records 1-10 displayed on this page)
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