The accumulation of 90Sr and 137Cs by herbs growing in the areas of operating nuclear fuel-cycle facilities

The areas of a nuclear industry impact were examined within the Radioecological Inspection Program; and an accumulation of radionuclides by some dominating species of medical herbs were studied. A sampling of a soil-plant cover was being made in summer season during 1999-2002 years. The samples were taken from the areas located in the 30-km zone of surveillance of the Beloyarsk NPP (Sverdlovsk region), the East-Ural Radioactive Trail (Chelyabinsk and Sverdlovsk regions) and the flood plain of the Techa River (Chelyabinsk and Kurgan regions). It was shown that a capability of plants to concentrate 90Sr and 137Cs is determined by a genesis of radionuclides coming to an environment, the physical and chemical forms, in which they are present in soil, and a species of a plant. Gas and aerosol discharges from the BNPP (which operates for 30 years) did not make a considerable contamination of the soil-plant cover in the 30-km zone, since the content of 90Sr and 137Cs in the investigated species was close to the level typical for the control sampling (units, tens of Bq/kg). In the areas of the East-Ural Radioactive Trail, formed after the nuclear accident at the nuclear plant Ayak the concentration of the main contaminant (90Sr) in the plants reached a value of hundreds of Bq/kg. It was found that the plants in the flood plain areas of the Techa River, contaminated with liquid industrial effluent from the above plant, accumulated more 90Sr (thousands of Bq/kg), than 137Cs (tens of Bq/kg) at close level of their content in soil. The values of the transfer coefficients of 90Sr and 137Cs into herbs were determined as the content of their mobile and fixed physico-chemical forms. (author)