Biosphere transport and radiation dose calculations resulting from radioactive waste stored in deep salt formations (PACOMA-project)

Abstract

This report presents part of the results of a safety-assessment study of disposal of radioactive waste in two kinds of salt formations in The Netherlands for seven cases with the same Dutch inventory and one with a reference inventory R. The choice of the salt formation has a major influence on the level of the dose. In case of deep domes, a maximum individual dose of 5.5E-4 to 1.2E-3 muSv/a occurs 4E6 years after waste disposal. Radionuclides disposed in shallow domes reach the biosphere much earlier than those out of deep domes. The maximum dose occurs at 1E5 to 4E5 years after disposal, and varies between 3.4E-2 and 8.6E-2 muSv/a for the individual dose and between 3.7E-3 and 1.0E-2 manSv/a for the collective dose. Small differences between dry and wet leached caverns are observed. In all cases, 99% or more of both the individual and the collective dose can be attributed to Np-237 and its daughters Th-229 and Ra-225, and to the U-238 daughters Ra-226 and Pb-210. Consumption of arable products is the major contamination pathway (70% of the individual dose ; 99% of the collective dose). Parameter analysis indicates that the calculated doses are unlikely to vary more than one order of magnitude for the biosphere as specified.