Radioactivity of fission products in cistern waters along the Croatian coast of the Adriatic Sea

Measurements of radioactive contamination of water samples from cisterns collecting rainwater from roofs etc. with fission products have been carried out along the Croatian coast of the Adriatic Sea since 1968. An exponential decline of radioactivity followed the nuclear moratorium.After the nuclear accident at Chernobyl, higher levels of 137Cs and 90Sr were detected again, cistern waters being the only environmental samples in Croatia in which elevated 90Sr activities persisted for several years. For the pre-Chernobyl period, the mean residence time of 90Sr in cistern waters being order of magnitude several years was similar to that calculated for fallout.Contrary, for the post-Chernobyl time, Sr mean residence time was calculated to be considerably shorter, reflecting the tropospheric mean residence time.Therefore, the pre-Chernobyl) and the post-Chernobyl mean residence times of 90Sr in cistern waters reflect the mechanism by which strontium was released to the atmosphere. The annual dose for the critical adult population received from 90Sr, 137Cs and 90Cs by drinking cistern water was estimated to be a few per cent of the dose from natural background radiation. (authors)