ABSTRACT
This chapter compares the two candidate concepts called mined repositories (MR) and very deep holes (VDH) for disposal of highly radioactive waste. While the function of the first-mentioned concept strongly depends on the complex structural constitution of shallow crystalline host rock and groundwater distribution, VDH intersects only a relatively small number of richly water-bearing discontinuities permeated by slowly moving groundwater driven by the very low hydraulic gradients at depth. For VDH, the deployment part of the host rock is tightly confined by high principal stresses, meaning that significant strain is accumulated in the few intersecting major fracture zones without creating any open space where high-level radioactive waste (HLW) is stored. An important difficulty in proper location of both MR and VDH repositories can be due to inadequate or missing data of the groundwater pressure and flow in areas with even surface topography.
