Special Studies FRACTION OF TOTAL 23%Pu G00! 0.01 on rrr ee 0! i ¥ TT © There have been a number of special studies dealing with migration of transuranics in soils, particularly with respect to laboratory investi~ gations and radioactive waste disposal problems. | E Routson et ai. (1975) reported on a study to evaluate SOFoanate Washington and South Carolina in their capacity to sorb and Am. In this study the effects of Ca*tt- and Na*~ion concentrations on the radionuclide distribution coefficient, Kae were determined. Distribution coefficient values for 73’np decreased in all cases of increased Catt- and Na*-ion concentrations, as shown in Fig. 10, Values for 2"Iam also decreased with increasing Catt~ and Nat-ion levels 2 in the South Carolina soil. ever 78 am-Ky values from the Washington soil were greater than 1200 and were not influenced by different concentrations of either Catt or Nat, a. uJ a The distribution coefficient can be related to ion migration rate in soil, making the proper assumptions that equilibrium is attained during leaching and that the species measured in the laboratory determination of Ka are the same as those in the leaching system and that the system is saturated. For example: _) 20F Oo ve r ”) 30 Fig. 9. i aia al. iL a al iL Ao pet = Ww Of | 1-0) p Ky + 8) where v, = velocity of the radionuclide in soil, Vw = velocity of the leaching water, 8 = fractional porosity, ® = grain density, 23 ®pu in Rocky Flats, Colorado Soil (Adapted from Krey and Hardy, 1970). Distribution of and Kq = measured distribution coefficient. Using the above relationship and data of Fig. 10, 73’Np, as a ion, can migrate much faster than 2 Na’-ion concentrations. lam, soluble particularly at low Catt+~ and Of course the specific physical and chemical characteristics of the soil will govern the actual degree of movement. Glover et al. (1976) conducted equilibrium sorption measurements on 17 soils fromthe United States with plutonium and americium nitrates. This experiment was designed to discover relationships between plutonium and americium and certain physical and chemical characteristics of the soils. Among the factors investigated were cation exchange capacity, soluble carbonate, soluble salt content, organic carbon, pH, Eh, and particle size distribution. Distribution coefficient values for americium at a concentration of 10719 M ranged from 82 to 10,000, and plutonium Kg values ranged from 35 to 14,000 for a concentration of 107§ M. Regression analysis was used to determine correlations between chemical/physical parameters and the degree of radionuclide sorption. Cation exchange capacity and clay and sand contents were found to be the most important, which indicates that a conventional ion exchange process was respensible for the sorption of plutonium and 60 61 How-