THE INFLUENCE OF RADIOACTIVE-WASTE DISPOSAL ON NATURAL ACTIVITY, HEAT-PRODUCTION, AND RADIOTOXICITY

The activity, hear production rate, and radiotoxicity of natural radio nuclides in parts of the continental crust and in seawater are compare d with the same quantities due to the radionuclides in spent fuel disp osed of as radioactive waste. A comparison based on a 5.16 x 10(4) GWa scenario with enrichments of natural radionuclides of the elements K, Th and U results in time periods of the order of 10(5) years for the activity, heat production rate, and toxicity of the repositories to de crease to the global levels of natural enrichments (deposits). These t ime periods are in agreement with the possibilities and limitations of performance and safety assessments. The site specific effects which d epend on masses and concentrations are also discussed. The results of the comparison with natural levels in seawater based on a model of com plete dilution in the oceans show that 10 year old fuel from a 5.16 x 10(4) GWa scenario would exceed the natural levels for about 1000 year s.