Determination of 226Ra and 228Ra in slightly mineralised natural waters

A radiochemical method for simultaneous separation of 226Ra and 228Ra from natural waters by precipitating the radionuclides in the form of chromates that have low solubility in weak acetic acid has been described. For analytical purposes the change into soluble state was achieved through high-temperature melting the radium chromates precipitate with sodium and potassium carbonates at certain ratios. The chemical yield for radium-226 amounted to 87.1 ± 1.4% at the efficiency of counting 92.8 ± 0.7%. Calculated in series of 20 parallel determinations, reproducibility of the method was 7%. The chemical yield in separating radium-228 made up 63.8 ± 1.1%.

Research highlights
► The aim of this study was to develop a fairly quick technique for 226Ra and 228Ra concentration from large (10 l) volumes of water with mineralization ranging between 80 mg/l and 129 mg/l.
► The main stage of radium chromate (RaCrO4) precipitation is done straight in the field, and the precipitate is subsequently dissolved in the laboratory.
► This method has several advantages: low levels of radium-226 and radium-228 can be determined, sample preparation adapted to use in the field is easy, speedy and inexpensive.