Improvements in the radiochemical method for separating ²²⁶Ra in solid samples through coprecipitation with BaSO₄

The aim of this work was to improve the commonly used method for ²²⁶Ra determination in water and to establish its application in solid samples. This method is based on the coprecipitation of Ra with BaSO₄ and gross alpha counting of the precipitate. An exhaustive study of the coprecipitation behaviour of the most abundant cations present in solid samples was performed to avoid incorrect radiochemical yields. As a result, it was considered necessary to introduce two new purification steps into the conventional method. Likewise, two nuclides, ²⁴¹Am and ²²⁶Ra, were compared to obtain the mass efficiency curve given their different behaviour in the coprecipitation process. While Ra behaves similarly to Ba, Am coprecipitates, forming mixed crystals that may behave differently in the self-absorption process. The influence of the cations on the chemical yield with no precipitate purification was: Sr²⁺≫Fe³⁺>Mg²⁺≈Ca²⁺>K⁺≈Na⁺. The method was successfully applied to soil, sediment, and plant ash samples.