Uranium / Radium / Polonium / Natural waters / Soluble fraction / SorptionSummary. Water of five drilled wells was filtered with three membranes (pore size 0.45 µm − 5 kD) to determine the soluble and particle-bound forms of 234,238 U, 226 Ra and 210 Po. Three of the waters were of Ca−HCO 3 type and two of Na−Cl type. Some of the waters also exhibited high concentrations of Fe, Mn and humic substances. 234,238 U was present entirely in soluble form in all waters, probably as uranyl ion (UO 2 2+ ) in soluble carbonate complexes. 226 Ra was in soluble form in the waters with low concentrations of Fe and Mn, but 10% of the total 226 Ra activity was bound to particles in the Fe−Mn-rich waters. The behaviour of Po varied with water composition. Particle-bound 210 Po was observed to correlate with the combined concentration of iron and manganese in the raw waters. In the two of waters of Na−Cl type, in which the concentrations of Fe, Mn and humic substances were high, salinity of the waters did not enhance the solubility of polonium. Polonium was present in both soluble and particle-bound forms in all the ground waters.

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For estimation of the activity of the long-lived 41 Ca isotope in seven concrete samples exposed to a varying neutron flux, 45 Ca activities in the samples were determined. Instead of total dissolution the concrete samples were treated with 8 M HCl and HNO 3 for partial dissolution of calcium. From the leachate, stable calcium was determined by AAS and 45 Ca activity with LSC after radiochemical separation while the total stable calcium in the concrete samples was determined by XRF. Calcium was separated from the leachates using cycles of precipitation and ion exchange. In addition to 45 Ca, seventeen γ -emitting radionuclides were detected directly in the concrete samples by γ -spectrometry. Ratios of 45 Ca activity concentrations to those of γ -emitting nuclides in the concrete samples with varying dose were more or less identical. Determination of 63 Ni activity in the concrete samples failed because activity levels were below the detection limit.

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