Prediction of Movement of Radionuclides in Solution Through Porous Media

Abstract

The disposal of radioactive wastes by injection into deep earth formations requires that predictions be made of the rate of travel of the various radioactive contaminants. The transport of a cationic radionuclide through the earth is determined by hydrodynamic convection, hydraulic dispersion and ion-exchange sorption. If the manner of water movement is first ascertained by tritiated water tracer measurements and the exchange properties are determined by laboratory tests, it is possible to predict the arrival of individual radioisotopes at some distant point of concern. For the prediction theory to be fully applicable, the formation should be reasonably homogeneous, the isotope distribution factor should remain constant, and exehange equilibria should prevail at all points. It is also desirable that the hydraulic flow net remain unchanged. The validity of the prediction theory has been tested with laboratory columns and with a field investigation. The field test involved several arrays of injections and relief wells and twenty-three observation wells penetrating a confined aquifer 100 ft below the earth's surface. The results demonstrated the theoretical validity and practical utility of the theory.