| To understand and quantify the sources of 36Cl in the environment, this research was undertaken in the eastern Snake River Plain aquifer system near the Idaho National Engineering and Environmental Laboratory (INEEL). The environment at and near the INEEL has significant inputs of 36Cl from nuclear-fuel and nuclear-waste processing that can be orders of magnitude larger than meteoric, weapons-tests, or in situ production. The INEEL is located in southeastern Idaho and is among the U.S. Department of Energy's (DOE) largest nuclear testing facilities.; The first research objective was an evaluation of the archived water samples in terms of 36Cl concentrations and possible chloride isotope fractionation through time. Secondly, concentrations of 36 Cl in the environment from meteoric, weapons-tests, and in situ production were established and compared to releases from nuclear-fuel and nuclear-waste processing at the INEEL. Finally, these 36Cl inputs to the environment were used to determine first arrival times at downgradient observation wells and one-dimensional hydraulic dispersivities in the far field.; To evaluate the suitability of the archived samples as an indicator of historical radionuclide concentrations, water samples from six USGS monitoring wells collected during 1969–93 and one surface water site from 1970 were analyzed for stable chlorine isotopic ratios, chlorine-37/chlorine-35 (37Cl/35Cl). The results of this evaluation indicated that no detectable fractionation of chlorine isotopes had taken place during storage. Therefore, 36Cl concentrations measured today in the archived water samples, are representative of the concentrations at the time of sample collection.; Quantification of 36Cl in the environment at and near the INEEL included calculation of meteoric input, fallout from atmospheric nuclear-weapons tests conducted in the 1950s–60s, and natural in situ production in the aquifer system. After accounting for 36Cl from these three sources, any remaining quantifiable concentration was concluded to originate from nuclear facilities at the INEEL.; To determine first-arrival times of 36Cl from site-disposal practices, analyses were performed on archived ground water samples from selected downgradient observation wells. Estimated first arrival times from 36Cl data in the archived water samples from observation wells indicate minimum ground water flow velocities of 1 to 3 m/day with velocities as large as 6 m/day. (Abstract shortened by UMI.)... |
