DETERMINATION OF RA-226 CONCENTRATIONS IN ENVIRONMENTAL WATERS BY LIQUID SCINTILLATION COUNTING EQUIPPED WITH ALPHA/BETA PULSE SEPARATION FUNCTION

摘要

A sensitive analytical procedure for determination of low-level ~(226)Ra concentration in environmental water was developed. The procedure is based on collection of ~(226)Ra in water by co-precipitation with BaSO_4, radiochemical separation of ~(222)Rn, which is grown from the decay of ~(226)Ra and alpha activity measurement for ~(222)Rn and its daughters by liquid scintillation counter equipped with alpha/beta pulse separation function. Each step in the analytical procedure was examined: the amount of Ba added to the water on the collection step and recovery of BaSO_4; the dissolution of BaSO_4 with EDTA solution; emanation of ~(222)Rn and following trap of ~(222)Rn on glass beads in U-tube cooled at liquid nitrogen temperature. The ~(222)Rn and daughter nuclides activity was measured by liquid scintillation counting and alpha counts are extracted from 3-dimentional spectrum obtained by liquid scintillation counting. This sensitive method was applied to determine ~(226)Ra concentration in river water of Kumamoto prefecture, Japan.