Determination of 90Sr in highly radioactive aqueous samples via conversion to a kinetically stable 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid complex followed by concentration-separation-fractionation based on capillary electrophoresis-liquid scintillation

Kazuki Ouchi; Tomoko Haraga; Kazuki Hirose; Yuika Kurosawa; Yoshiyuki Sato; Masami Shibukawa; Shingo Saito

doi:10.1016/j.aca.2024.342399

Determination of ⁹⁰Sr in highly radioactive aqueous samples via conversion to a kinetically stable 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid complex followed by concentration-separation-fractionation based on capillary electrophoresis-liquid scintillation

Anal Chim Acta. 2024 Apr 15:1298:342399. doi: 10.1016/j.aca.2024.342399. Epub 2024 Feb 20.

Authors

Kazuki Ouchi¹, Tomoko Haraga², Kazuki Hirose³, Yuika Kurosawa³, Yoshiyuki Sato⁴, Masami Shibukawa³, Shingo Saito⁵

Affiliations

¹ Nuclear Science and Engineering Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki, 319-1195, Japan; Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama, 338-8570, Japan.
² Department of Decommissioning and Waste Management, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki, 319-1195, Japan. Electronic address: haraga.tomoko@jaea.go.jp.
³ Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama, 338-8570, Japan.
⁴ Department of Decommissioning and Waste Management, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki, 319-1195, Japan.
⁵ Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama, 338-8570, Japan. Electronic address: shingo@mail.saitama-u.ac.jp.

PMID: 38462347
DOI: 10.1016/j.aca.2024.342399

Abstract

Background: The Fukushima Daiichi Nuclear Power Plant accident (2011) released large amounts of radioactive substances into the environment and generated highly radioactive debris. Post-accident countermeasures are currently in the phase of fuel debris removal, which requires the analysis of radioactive contaminants in the environment and fuel. The spectra of solely β-emitting nuclides, such as ⁹⁰Sr, overlap; thus, an effective method for nuclide separation is desired. Since conventional methods for high-dose sample analysis pose substantial exposure risks and generate large amounts of secondary radioactive waste, faster procedures allowing for decreased radiation emission are highly desirable.

Results: In this study, we developed a ⁹⁰Sr²⁺ quantitation technique based on liquid scintillation counting (LSC)-coupled capillary transient isotachophoresis (ctITP), along with two-point detection and relying on the rapid concentration, separation, and fractionation of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-complexed ⁹⁰Sr²⁺ in a single run. The applicability of our method for the analysis of real-world samples was verified by conducting addition-recovery experiments using a seawater reference material and radioactive liquid waste obtained from the radioactive waste treatment facility at the Japan Atomic Energy Agency. The recovery determined by LSC was 95-113%, indicating successful quantitative analysis. ⁹⁰Sr recovery was determined to be 90.1% from a contaminated water sample obtained from the Fukushima Daiichi Nuclear Power Plant, which was analyzed using the standard addition of ⁹⁰Sr. The sensitivity (detection limit = 0.016 Bq) of the proposed method on a radioactivity basis was equal to or higher than that of the conventional method using ion exchange-LSC (0.012-0.07 Bq).

Significance and novelty: Our method allows for the handling of high-dose radioactive samples at the microliter level and is substantially faster than conventional ion exchange protocols, whereas ctITP has not been used for practical applications due to inaccurate collection and lack of a suitable chemical system. The concentration-separation-fractionation protocol in ctITP is successful due to the existence of a rare inert Sr²⁺ complex and precise fractionation. This study establishes a pathway toward safer and more practical analysis of radionuclides.

Keywords: Beta-emitting nuclide; Capillary transient isotachophoresis; Electrophoresis; Fractionation; Liquid scintillation counter; Strontium-90.