Enhanced natural environmental radioactivity by human impact

Recultivated waste rock pile in a uranium mining area

Natural radiation exposure is essentially caused by radionuclides which occur in the uranium-238, uranium-235 and thorium-232 decay chains and are found in the earth’s crust. Higher concentrations of these radionuclides (compared to the geogenic level) can be released into the environment in particular through mining activities but also through the processing of raw materials.

While radiation protection is ensured from the start for industrial residues since 2001 on the basis of the Radiation Protection Ordinance (StrlSchV), radiation protection measures for contaminations which have already occurred can only be taken subsequently.

Occurrence

This occurs most importantly in ores of the uranium deposits in Saxony and Thuringia, but it is also valid for deposits of silver, copper, tin and other resources in different German regions, for example the Ore Mountains (Erzgebirge).

Other raw materials with enhanced concentrations of natural radionuclides, such as bauxite and phosphate ores, have been imported on a large scale.

Accumulation in residues during conditioning and processing

During conditioning and processing of the raw materials these radionuclides may accumulate in the residues (including sludges, slags, dusts, ashes, incrustations) and their concentrations may increase considerably compared to the geogenic level so that they must be taken into account from the radiation protection point of view.

Radioactive relics

In the past such residues were deposited on waste heaps or in tailings ponds or even further utilised because people were unaware of - or, in some cases, ignored - the enhanced radioactivity contained therein. Dissolved radionuclides or solid residues can be released through seepage but also through accidents, such as dam failures in tailings ponds, and in the worst case accumulate in river sediments or on alluvial soils.

Partly, former industrial sites of residues with enhanced natural radionuclide concentration were covered with buildings. Depending on the site and usage conditions such contaminations may, in individual cases, cause radiation exposures to members of the public which require subsequent protection measures.

The field of radioactive relics – with the exception of regulations on residues of the former uranium mining area in eastern Germany –, however, is still not sufficiently regulated by law.