Flow electrolytic separation of radionuclides for interference suppression in γ-spectrometry

The direct and accurate measurement of low-level γ-emitters in samples from nuclear facilities is a challenging task due to the presence of high activities of dominant radionuclides. In this case a complex chemical separation is required to remove interfering radionuclides prior to γ-spectrometric analysis. Several radionuclides such as, ^110mAg, ^124,125Sb, ¹¹³Sn and ^123mTe are of relevance for radioanalytical analysis in nuclear facilities. These may be readily electrodeposited at controlled-potential using flow electrolysis in aqueous solution. Here, the development and use of flow electrolysis for the pre-analytical separation of different radionuclides to suppress interferences in γ-spectrometric measurements is presented.

Model electrochemical systems containing inactive Ag, Sb, Sn, and Te were first characterized by voltammetry. Their separation by selective electrodeposition and stripping was evaluated with a custom-made, low-cost electrochemical flow-through cell. After optimization, the use of the flow-through cell yielded good separation procedures for stable elements at carefully chosen applied potentials. The developed electrochemical procedures were finally employed for the separation of model mixtures of radioactive tracers as well as for samples from nuclear facilities. The separation of, e.g., ^110mAg or ^123mTe by flow electrolysis afforded a substantial decrease of the uncertainty and the detection limits by one order of magnitude during γ-spectrometry. This allowed for a more accurate determination of low-level activity radionuclides in a sample from a nuclear facility (^123mTe) as well as for the identification of others which were previously below the detection limit (¹⁰³Ru, ^110mAg).

These results demonstrate the benefits of combining flow electrolysis with γ-spectrometry for analysis of low-level radionuclides in the presence of dominating radionuclides, and can be readily combined with other measurement techniques such as liquid scintillation counting or α-spectrometry. The presented approach not only provides a different chemical selectivity when compared to traditional separation methods, but can also be used in combination with other flow separation methods such as ion-exchange or extraction chromatography.