RELEVANCE OF NEAR FIELD AND FAR FIELD EFFECTS TO THE RELEASE OF RADIONUCLIDES FROM REPOSITORIES WITH LOW LEVEL WASTE

摘要

The release and transport of radionuclides from repositories into the biosphere is controlled by natural and technical barriers. In the near field, waste containers, sealings, backfill and solubility limits are considered as barriers. In the far field, sorption, dispersion and dilution effects are important. By comparison of the results of performance assessments for repositories within a salt formation and within a sedimentary formation, the behaviour of both kinds of repository is shown. In the studies presented, near field effects are especially important for the repository in salt, far field effects for the repository in sediment. In all the studies, the most important radionuclides with respect to the dose rates are ~(99)Tc, ~(129)I,~(234)U and its daughter nuclides, and ~(237)Np.