Radiation Balance of Spent Nuclear Fuel from Thermal Reactors and the Equivalent Uranium Mass for Natural Organisms

The conditions for the onset of radiation equivalence of spent nuclear fuel from VVER and the equivalent mass of natural uranium according to the irradiation dose to organisms of surface ecosystems is investigated. It is found that organisms of soil biota receive the highest dose; mammals are the critical organisms for determining the requirements for wastes in terms of minimizing the onset time of radiation balance. The requirement for the onset of radiation balance in an acceptable time ~300 years can be met by separating from the spent nuclear fuel U, Pu, and Am with the residual amount in wastes no more than 0.1%. Radiation equivalence appears more quickly as the reactor run decreases or the depth of fuel burnup decreases. The results of this work confirm the main positions concerning radiation equivalence which were developed on the basis of comparative assessments of the biological hazard for man of the radionuclides present in the spent fuel and raw uranium.