Radioactive contamination of cistern waters along the Croatian coast of the Adriatic sea

Radioaktivna kontaminacija cisternskih voda 90Sr, 134Cs i 137Cs mjeri se od 1968. godine duž hrvatske obale Jadranskog mora. Nakon prestanka većih pokusa s nuklearnim oružjem u atmosferi, radioaktivnost eksponencijalno pada. Poslije nuklearne nesreće u Černobilju opet dolazi do značajnog porasta radioaktivnosti. Srednje vrijeme boravka 90Sr u cisternskim vodama prije i poslije Černobilja upućuje na način kojim je stroncij dospio u atmosferu (pokusi nuklearnog oružja u stratosferi, odnosno eksplozije u černobiljskom reaktoru kojima je radioaktivni materijal dospio samo do troposfere). Za pretčernobiljsko razdoblje srednje vrijeme boravka 90Sr u cisternskim vodama od oko 10 godina slično je srednjem vremenu boravka u radioaktivnim oborinama. Postčernobiljski omjer aktivnosti 137Cs/90Sr se smanjuje, ali još nije dosegao pretčernobiljske vrijednosti (=1,6). Vremenski ovisan omjer aktivnosti 134Cs/137Cs reflektira reaktorski inventar tih radionuklida. Godišnja doza za kritičnu odraslu populaciju primljena od 90Sr, 134Cs i 137Cs konzumacijom cisternske vode procijenjena je na nekoliko postotaka doze od prirodnog zračenja.Measurements of radioactive contamination of cistern waters with 90Sr, 134Cs and 137Cs have been carried out along the Croatian coast of the Adriatic Sea. An exponential define of radioactivity followed the moratorium on nuclear tests. After the nuclear accident at Chernobyl, high radioactivity levels were detected again. 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 (atmospheric nuclear weapon tests conducted in the stratosphere or explosions in the Chernobyl nuclear reactor releasing radioactive material to the troposphere). For the pre-Chernobyl period, the mean residence time of Sr in cistern waters was similar to that calculated far fallout, being approximately 1O years. The post-Chernobyl 137Cs/90Sr activity ratio has been decreasing, but it has not yet reached the pre-Chernobyl values (=1.6). The time-dependent 134Cs/137Cs activity ratio reflects the Chernobyl reactor inventory of these radionuclides. The annual dose far the critical adult population received from 90Sr, 134Cs and 137Cs by consumption of cistern water was estimated to be a few percentages of the dose from natural background radiation