A POROUS FLOW MODEL FOR STEADY-STATE TRANSPORT OF RADIUM IN GROUNDWATER

Abstract

The quasi‐steady variation of uranium and radium isotopes from the decay of U, U, and Th has been determined along an idealized, one‐dimensional aquifer which is a distributed source of activity and from which the transfer of radionuclides to solution occurs by alpha recoil and chemical exchange. The model includes the effects of dispersive flow and retardation by adsorption. The importance of these effects on the variation of U and Ra activity ratios along the model aquifer is shown. Predicted limiting activity ratios (for large flow times) of Ra/ Ra, Ra/ Ra, and Ra/ Ra are 21.4, 1.5, and (∼1.7–2.0) (U/Th) , respectively (where (U/Th) is the activity ratio U/ Th in the aquifer rocks..