Investigation of leaching of radionuclides and hazardous materials from low-level wastes at Oak Ridge National Laboratory

Leaching of both radioactive contaminants and Resource Conservation and Recovery Act hazardous material contaminants from representative low-level radioactive wastes generated at Oak Ridge National Laboratory was investigated using two different leaching methodologies: the current Environmental Protection Agency (EPA) Toxic Waste Extraction Procedure (EP) and a proposed EPA Toxicity Characteristic Leach Procedure (TCLP). Cesium, both 137Cs and 134Cs, was present in many of the waste samples. The average fraction leached for cesium was only ∼0.4. Since much of the cesium handled is in the form of CsCl, the limited leaching observed was surprising. Cobalt, as 60Co, was present in many samples; the fraction leached ranged from about 0.2 to 0.7 for various samples. Strontium, as 90Sr, was present in all but one waste sample. Strontium was readily leached from most samples; this result seemed reasonable because much of the strontium handled at ORNL is in the form of SrCl2. Selenium, present as 75Se, was identified in one-half the samples tested. This observation was surprising because selenium is not currently listed as a radioactive waste component in ORNL low-level wastes. The selenium fraction leached was only ∼0.2. Chromium, cadmium, and lead were the only inorganic elements identified in a few waste samples at sufficient concentrations to be of potential environmental concern. In no case, however, did the leach extract exceed the EPA toxicity characteristic limit. For a number of the wastes tested, the proposed TCLP leach methodology was more effective in extracting contaminants than was the current EP method. 11 refs., 4 figs., 19 tabs