Determination of low 137Cs concentration in seawater using ammonium 12-molybdophosphate adsorption and chemical separation method

A new method has been developed for analyzing 137Cs in a small volume of seawater. Ammonium 12-molybdophosphate (AMP) was used two times during pretreatment procedure. The first step was to adsorb 137Cs in seawater samples into AMP in order to reduce sample volume, and the second was to remove 87Rb, interference nuclide for β counting. The AMP adsorbing 137Cs was dissolved by sodium hydroxide solution, and then 137Cs was finally formed to be cesium chloroplatinate precipitate by adding 10% hexachloroplatinic acid. The beta rays emitted from 137Cs were measured with a low background gas-proportional α/β counter. This method was applied to several seawater samples taken in the East Sea of Korea. Compared to the routinely used γ-spectrometry method, this new AMP method was reliable and suitable for analyzing 137Cs in deep seawater.