Isotope techniques in the hydrogeological assessment of potential sites for the disposal of high-level radioactive wastes

This report reviews the possible application of isotope techniques within one specialized field where the problem of interest is the characterization of low-flow, low-permeability regimes. For those specialists concerned with planning a repository this report indicates what contribution isotope techniques can make to the understanding of groundwater movement in environments potentially suitable for the disposal of high-level radioactive wastes. In low permeability rocks even the drilling of exploratory boreholes may materially change hydraulic properties, thus making the interpretation of classic hydraulic analyses difficult. Isotopic and geochemical techniques may be the only available methods which can be used to assess groundwater flow conditions without seriously perturbing the system being investigated. Although directed specifically at problems met in the disposal of high- and medium-level wastes, this report indicates techniques which are also applicable when investigating other environmental problems. Thus, they are of use in assessing landfill sites for the disposal of municipal wastes, and of sites for the shallow burial of toxic or low-level radioactive wastes. The origin of mine drainage waters and the use of underground caverns for storage of both wastes and raw materials are also related issues in which the isotopic techniques discussed here can provide useful data. Furthermore, an essential component of hydrological investigations should be to document the pre-disposal isolation of a selected site