English Abstract PROSA is a study on the safety of radioactive waste
disposal in a salt formation using probabilistic techniques. The present
report describes the determination of the input parameters for the PROSA
calculations as far as the groundwater compartment is concerned. One of the
most important parameters for the transport of radionuclides through the
geosphere is the vertical groundwater velocity. This constant uniform
velocity is interpreted as an effective velocity representing a
2-dimensional flow in a more complex geological system. This system is
modelled with the code METROPOL using a Monte Carlo approach. Sets of input
data are obtained by Latin Hypercube sampling. Particle tracking in the
calculated flow field yields a travel time for conservative nuclides. The
effective velocity is found by dividing the overburden thickness by the
travel time. For the diapirism/subrosion scenorio the effect of a gradually
decreasing thickness has been taken into account. Statistical analysis of
the results indicates that the particle velocities are lognormally
distributed. The data display a significant relationship between the
particle velocity and the thickness of the overburden.
