METHOD DEVELOPMENT FOR THE EXTRACTION OF NATURALLY-OCCURRING RADIONUCLIDES IN MARINE-SEDIMENTS

The ability of marine sediments to adsorb naturally occurring radionuc lides is dependent upon the surface area to volume ratio of the partic les and hence their grain size. Finer sediments have a greater surface area to volume ratio and so a greater adsorption capacity per unit vo lume of sediment. Some sediments contain naturally occurring radionucl ides within their lattice structure, due to the mineralogy of the sour ce rock, as well as those adsorbed onto particle surfaces. Four marine sediments, differing in grain size and mineralogy, were chosen to inv estigate the efficiency of different chemical extraction methods. Leac hing with 6 M hydrochloric acid is the most widely adopted procedure f or extracting the adsorbed activity. This work compares total dissolut ion with mineral acid leaching methods to investigate the extent to wh ich each method invades the lattice structure. Naturally occurring rad ionuclides in the U-238-decay series were isolated and purified by co- precipitation and ion-exchange techniques. Radioactive tracers were us ed as internal standards to determine the chemical yield. Quantitative and qualitative determinations were performed using alpha spectrometr y. This work has resulted in: (i) optimum methods for the extraction o f radionuclides in each type of sediment; and (ii) a critical comparis on of the techniques through consideration of the tracer yield.