On the determination of 226Ra in environmental and geological samples by α-spectrometry using 225Ra as yield tracer

A method for the determination of 226Ra in environmental and geological samples by α-spectrometry is described. The method is based on the use of 225Ra, in radioactive equilibrium with its parent 229Th, as yield tracer. This tracer permits the incorporation of 226Ra determination into the radiochemical procedure commonly used for the determination of U and Th isotopes in the same sample. Estimation of 225Ra in the α-spectra is made via measurement of its α-emitting daughters, 217At being the most suitable to this purpose. In order to achieve it, several requirements need to be fulfilled in the radiochemical procedure, which will be discussed.