Disposal of radioactive liquid wastes through deep wells may be categorized as containment or confinement. Containment means the placement of wastes under conditions that preclude their movement out of a definable zone. Confinement means the placement of wastes in a zone where movement may take place under restricted conditions that can be controlled or monitored.

Disposal of liquid wastes on a continuing basis by containment probably is not practical except for small quantities and may be possible in only a few areas. It is probable, therefore, that any deep disposal of radioactive liquid wastes will be by confinement of wastes in certain geologic horizons through which they will move at measured rates.

Hydrologic principles applied to the data presently available indicate that there is circulation of fluids in almost all sediments. Movement of fluids tend to be restricted in the basal parts of sedimentary basins, but any assumption that wastes introduced into a basin would not eventually move out of the basin or to the near-surface formations should be carefully scrutinized. Introduction of wastes into an anomalously low-pressure zone should not be considered safe until or unless the reason for the low pressure can be explained.

Data necessary to define the hydrodynamics of fluids injected through deep wells will be expensive to obtain, and many of them will have to be collected for each particular disposal site. Geochemical factors may influence greatly the movement of radioactive material in deep formations. A system of monitoring, and possibly removal, is a prime requisite of deep-well disposal of radioactive wastes. Initial disposal activities necessarily will be on an experimental basis pending the results of such monitoring.