Radionuclide Transport Calculations in the Safety Assessment SR 97

Abstract

This study treats radionuclide transport calculations for a canister defect scenario in the safety assessment SR 97, which concerns a deep repository for spent nuclear fuel of the KBS-3 type in Sweden. The aims of the calculations are to:Quantitatively describe the radionuclide transport.Show the impact of uncertainty in input data and show which parameters govern the calculated release rates.Compare three different real sites in Sweden (Aberg, Beberg and Ceberg) with each other and with dose limits given in Swedish regulations (none of the sites is considered in the on-going localization process). Only briefly described in this paper.Illustrate the impact of the different barriers in the system.Deterministic calculations illustrate the radionuclide transport for reasonable conditions. Uncertainty cases show the influence of the uncertainty for data related to different parts of the repository system by systematically giving them pessimistic values while all others are reasonable. Simplified probabilistic calculations have also been performed.The analysis shows that the most important parameters in the near field are the number of defective canisters and the instant release fraction. In the far field the most important uncertainties affecting release and retention are connected to permeability and connectivity of the fractures in the rock. The dose rate in the biosphere is essentially controlled by the possibilities of dilution.The calculated maximum doses for the hypothetical repositories are well below the dose limits, and hence they meet the acceptance criteria for a deep repository for spent fuel.

Modelling groundwater contamination above a potential nuclear waste repository in the Columbia River Basalt, USA

“…Solubility limits for 10 radionuclides out of a total of 13 are provided by Salter and Jacobs (1982) together with distribution coefficients for CRB groundwater. The missing data (I-129, Pa-231 and Th-230) are taken from a compilation for low-salinity granite groundwater, together with diffusivities for all radionuclides (Table 2; Lindgren and Lindström 1999).…”