Radioecology is a branch of radiation protection. Its object is the study of the behaviour of radionuclides in the environment. Their transfer from one compartment (water, soil, air) to the other is best modelled based on the results of measurements of radionuclide concentrations in the environment. For this purpose, computer models are developed that describe the path taken by the radionuclides. Input data for such radioecological calculations are concentrations of radionuclides in the air, in water, and sometimes in the soil.
If there is any actual contamination, there will be corresponding measured values. For the purpose of licensing procedures, the values will be determined theoretically with the help of dispersion calculations. At the end of the radioecological model there is usually an amount of radionuclides ingested (either inhaled or taken up with food) by a human being within a certain unit of time. This is then converted into a level of radiation exposure (dose). The radiation exposure of animals and plants can be determined in the same way.
Radioecologial models are used to check whether the set limits for radiation exposure are not exceeded, e.g. in connection with the controlled discharge from nuclear installations and operations or related to the legacies from past uranium ore mining. Taking part in international projects, GRS is involved in the development and validation of radioecological models. On behalf of the European Commission, GRS has checked with the help of radioecological models which potentially contaminated foodstuffs should continue to be subject to import control before entering the European Union. This was done against the background that after the accident at Chernobyl, the limits set for the concentration of the radionuclide caesium-137 in foodstuffs might be exceeded.
A further focus is on the modelling of changing biospheres. Here, for example, the effects of climatic changes on possible radionuclide contamination in the distant future were evaluated, which is necessary for the assessment of the safety of repositories for radioactive materials. In this context, the BIOCLIM project deserves special mention. It is sponsored by the European Commission, with GRS taking an active part in it.
NORM and TENORM
One focus of radioecology is on the study of the physical, chemical or biological processes that will lead to the accumulation of natural radionuclides in interim and final products as well as to residues (naturally occurring radioactive material (NORM), technically enhanced NORM (TENORM)). Such residues may e.g. arise in connection with mining – like for example in the former uranium ore mining regions of the WISMUT SDAG in Saxony and Thuringia – or with oil or natural gas production. The accumulation of radionuclides on the filters of many water works is also an example of NORM or TENORM.
Beyond the study of the fundamental processes, GRS also deals with the development and validation of radioecological models describing the distribution of natural radionuclides in the environment. With the help of such methods, GRS i.a. assesses the dumping or recycling of NORM residues from a radiological point of view, clarifies issues relating to the transport of NORM and TENORM, and participates in the determination of exposure levels at specific workplaces with increased natural background radiation.