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

A method for the determination of Ra-226 in environmental and geological sa mples by alpha-spectrometry is described. The method is based on the use of Ra-225, in radioactive equilibrium with its parent Th-229, as yield tracer . This tracer permits the incorporation of Ra-226 determination into the ra diochemical procedure commonly used for the determination of U and Th isoto pes in the same sample. Estimation of Ra-225 in the alpha-spectra is made v ia measurement of its alpha-emitting daughters, At-217 being the most suita ble to this purpose. In order to achieve it, several requirements need to b e fulfilled in the radiochemical procedure, which will be discussed. (C) 20 00 Elsevier Science Ltd. All rights reserved.