Determination of Sr 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.

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 Sr, 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 Sr 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 Sr 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. Sr 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 Sr. 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 Sr complex and precise fractionation. This study establishes a pathway toward safer and more practical analysis of radionuclides.