Radioactivity in the nature

The researches of ATOMKI, Hungary, in the field of the presence of radioactive materials in the nature are summarized. A detailed research work was performed to determine the geochemical rules of the presence and concentrations of U an Th in different minerals. The radioactive material content of natural surface and mineral waters were also measured. The fission products of the atmospheric nuclear weapon tests were measured in the precipitation, in the air and in biological materials. The time series of these data can be used to detect the present nuclear tests. The concentration of radioactive gaseous fission products, mainly sup(85)Kr has been increased in the atmosphere since the first nuclear explosions. Recently, the industrial reprocessing plants of nuclear wastes are the main sources of sup(85)Kr. The age determination method by radioactive carbon isotope sup(14)C of biological materials was adopted by ATOMKI. The increase of the concentration of atmospherical sup(14)C due to the nuclear explosions was measured - this effect must be taken into consideration using the sup(14)C age determination. (D.Gy.)