Groundwater velocity magnitude in radionuclide transport calculations

Analytical solutions have been developed for many conceptual models of solute transport in groundwater (Bear 1979). Although these models usually rely on assumptions too restrictive for accurate description of actual field situations, they are useful in understanding groundwater transport and in evaluating the relative importance of the subsurface processes affecting transport. In addition, these simple models are often used for generic and screening-type analyses of groundwater contamination problems (Kent et al. 1985). For example, the Nuclear Regulatory Commission assesses potential doses resulting from the disposal of very slightly contaminated material in the ground using analytical solutions for one- and two-dimensional groundwater transport (Codell and Schreiber 1979; Codell et al. 1982; Goode et al. 1986). This note presents a method for determining a "worst-case" groundwater velocity value for two conceptual models of decaying radionuclide transport, resulting in maximum calculated point concentration.