The study of relevant and essential flowpaths

At a KBS-type repository, flowpaths relevant to performance interact with the waste packages. Their proximal parts provide essential portions of the flow resistance and transport time. They can be studied by local investigations. The farfield, in contrast, remains inaccessible for detailed study. Validation regarding long-term groundwater transport of nuclides should focus on (1) nearfield mass transfer and retardation under natural gradients, and (2) sub-surface dilution at discharge. Tentative in-situ experiments are briefly considered. Validation concerning other groundwater effects appears more urgent. Inflow to tunnels and shafts is irrelevant to backfilled repositories. 1 fig., 11 refs