MOVEMENT OF URANTUM Although uranium is not a transuranic, certain uranium isotopes in the nuclear fuel cycle have been identified as potentially hazardous and Table 3. Warrant discussion. 233 Assumed Radioactivity of Uranium Isotopes 233 in 1 gram of U Fuel 232 Till (1975) discussed the recycle aspects of U bred from Th in the High Temperature Gas-Cooled Reactors. The recycle 773u can contain up to 1200 ppm 232u which was stated a relatively high specific activity, total 772-2344 radioactivity. various uranium isotopes to be very radiotoxic, and as accounting Table 3 in 1 ¢ of lists as having for 82.1% of the the assumed activities of 233y fuel. It can be seen that’??? u can account for greater than 50% of the total uranium activity present. Because of the potential environmental hazard of 7??U, of uranium migration through soils is an evaluation in order. Natural uranium is distributed throughout minerals and sediments world over. Hansen and Stout (1968) the noted that uranium and thorium appeared to accumulate in soils as a result of rock weathering and soil formation. the Maximum natural "B" horizon, whereas thorium concentrations tended to be themaximum uranium concentrations were most are highest in the soil clay fractions; however, Hansen {1970), in a subsequent study, suggested recycle activity fraction (ci) 232), 001 2.14 x 10°? 233) 613 5.82 x 109 234), .243 1.51 x 103 2355) 080 1.72 x 1077 236, .063 3.99 x 1076 Adapted from Till (1975). that 600,900 years after initial deposition, most of the nuclides of the uranium and thorium families are in the finer textured soil fractions and that the uranium that is retained by the soil is more likely to be fixed in some immobile form. Probably the only literature citation revealing uranium migration in environmental soils on a short-time basis was presented by Essington (1976). During the nuclear testing program discussed earlier in the section entitled "Safety Shot Sites," there was an explosive test of 235y enriched nuclear device. A soil profile taken from near the round zero area (Fig. 13) showed the vertical distribution of 239,260 Pu 38 levels reflected the natural concentrations The aey, and 7?5y, However, when 235y was disin the mineral structure of the soil. tributed over the soil surface it did migrate into the soil pro- file as evidenced by the 735y distribution. to behave very much like the same time. 239,240n,) Equilibrium recycle atom clays developed from carbonate rich soils show relatively low uranium and thorium concentrations. Isotope in often in the topsoil. This suggests that thorium moves down the soil profile more rapidly than uranium. Generally, uranium and thorium concentrations Equilibrium This added ??*u appeared also distributed at approximately 66 67