Characterization of the Hanford 300 Area Burial Grounds. Task II. Geochemical Analysis

摘要

The geochemical interaction of radionuclides with geologic materials must be understood in order to assess radionuclide migration from waste burial structures. In Task II, Geochemical Analysis, soil samples were taken from a representative disposal site to provide information that could be applied to the retired 300 Area Burial Grounds on the Department of Energy's Hanford Site, Washington. The site chosen for evaluation was the 316-4 Crib, which received liquid waste containing hexone and a total of 939 kg of uranium between 1948 and 1956. The methodology developed to analyze the soil samples combined neutron-enhanced autoradiography, x-ray fluorescence, and electron microprobe and radiochemical data. Results showed that the uranium content of the soil immediately underlying the crib is small. Furthermore, the uranium in the 316-4 Crib generally formed an insoluble phosphorus compound that was not readily leached under ambient conditions. However, uranium was easily leached in dilute acid solutions. Consequently, acidic solutions should not be added to waste burial structures that contain uranium compounds. The buffering and cation exchange capacity of the soil clay fraction tends to retard migration of the water-soluble forms, and uranium from the 316-4 Crib has not been detected in the Columbia River. No significant health hazard is apparent at present as a result ofuranium disposal at the 316-4 Crib; however, efforts should continue to restrict access to this site. (ERA citation 04:049560)