Abstract
A precise determination of the extremely low concentration of radium in marine carbonate samples via 222Rn counting using a ZnS(Ag) scintillation chamber was described. Carbonate sample was dissolved with hydrochloric acid and the solution was sealed in a Curie bottle for the period of accumulation of 222Rn from 226Ra. The radon in the bottle was separated from the solution and collected in a trap cooled with liquid nitrogen. Finally the radon was transferred to the scintillation chamber which is coated with a thin layer of ZnS(Ag) powder. The luminescence signals by alpha rays were well discriminated from background. Advantages of this method are as follows; its simple and reliable operation, low background count (4.5±0.5cph) and low detection limit of I × 10-14 g Ra. Some results of radium content determinations of modern and fossil shell samples are reported.
