Determination of potential radiation exposure via terrestrial food chains by the release of radioactive material from nuclear facilities

The radiation exposure level caused by consumption of vegetable and animal products in the environment of nuclear power plants is determined to a large extent by the release of 90Sr, 134Cs, and 137Cs. For long-lived nuclides, especially 90Sr, transfer from the soil into vegetation makes the essential contribution to plant contamination after several years of power plant operation. The relevant transfer coefficients for the different plant species vary, depending on the soil properties, between 0.02 and 6.0 [pCi/kg fresh weigth of vegetation : pCi/kg dry weight of soil] for Sr and between 1.10-3 and 0.2 [pCi/kg fresh weight of vegetation : pCi/kg dry weight of soil] for Cs. The sensitivity analysis shows that already a variation of the transfer coefficients for Sr from 0.5 up to 2.5 [pCi/kg fresh weight of vegetation : pCi/kg dry weight of soil] and for Cs from 3.10-2 up to 2.10-1 cause variations in the level of radiation exposure for individual exposure pathways by factors fo 2 to 4. Correspondingly higher values are to be expected by still larger transfer of Sr and Cs from the ground to vegetation. For transfer coefficients >- 2.5 [pCi/kg fresh weight of vegetation : pCi/kg dry weight of soil], however, removal of radioactive substances from the ground by the plants must not remain without consideration any longer. (orig./HP)