THE FAST MULTIPLE-PATH NUCTRAN MODEL-CALCULATING THE RADIONUCLIDE RELEASE FROM A REPOSITORY

The NUCTRAN model has been applied to the Swedish KBS-3 nuclear waste repository concept, where the migration of radionuclides is through va rious barriers and pathways. The escape of the nuclides from the canis ter occurs through a small hole. This hole controls the release of nuc lides from the repository. NUCTRAN is a useful tool to calculate the n onstationary transport in a repository for high-level nuclear waste. T he advantage of this model is the use of a coarse compartmentalization of the repository, which makes it flexible and easy to adapt to diffe rent geometries. The several radionuclide release calculations made wi th NUCTRAN have shown the capability of this to handle different situa tions rapidly and easily. The particularity of these calculations is t he high accuracy obtained by using a coarse compartmentalization of th e Swedish KBS-3 repository and the small requirements of computing tim e. At short times for short-lived nuclides, the calculated releases ar e exaggerated. The error can be considerably reduced by an additional subdivision of large compartments into a few compartments.