The small Precambrian U-Th deposit of Palmottu, Finland, has been studied as a natural geological analogue for a highlevel radioactive waste repository. The chemical composition and physico-chemical characteristics of groundwater with tritium values in drill holes intersecting the deposit are given. Uranium concentrations and 234 U/ 238 U radioactivity ratios in groundwater, based on various sampling methods, are presented as depth profiles (from surface to 250 m). Factors affecting the distribution of uranium and the observed activity ratios in groundwater and particulate matter are discussed.

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