Geochemistry of 239Pu, 99Tc and 129I

The occurrence of selected long-lived fission products (99Tc and 129I) and 239Pu is being studied in solid and water samples. Methods of extraction of these isotopes from large volumes of groundwater have been developed, as well as methods for their measurement at the very low natural levels. Thus by directly measuring the neutron production rate on each ore sample and then using Monte Carlo Neutron/Photon Transport Code (McNP) to track the fate of these neutrons was possible to identify the critical elemental parameters controlling radionuclide production rates, and to test for expected correlations among product/target radionuclide pairs. The thermal component of neutron fluxes in uranium deposit appears to be quite small, with the vast majority of neutrons being absorbed in higher energy ranges. It is trerfore concluded that it is nearly impossible to estimate 239Pu and 129I concentrations and correlations by any simplistic calculations. In water from within and down-gradient of the deposit, 129I/I ratios are higher by one to three orders of magnitude over background levels in the vicinity of the deposit. The down-gradient decrease is not systematic with distance from the orebody and probably reflects differing extents of dilution rather than sorptive losses. 1 tab., 2 figs