Application of borehole geophysics to the selection and monitoring of nuclear waste disposal sites

Geophysical well logging provides in situ measuring techniques that can be used in conjunction with other geologic and hydrologic methods for evaluating and monitoring proposed and existing radioactive waste disposal sites. Conventional well-logging techniques provide useful data on lithology, porosity, and ground-water quality. The borehole televiewer is used for identifying fracture porosity that can have crucial bearing on the patterns of ground-water flow and, consequently, the migration of radionuclides associated with radioactive wastes. Borehole gamma spectrometry is used to identify and determine the concentration levels of artificial gamma-emitting radionuclides moving in the ground-water system. The artificial radioisotopes 60Co, 134Cs, and 137Cs have been detected in a monitoring research program conducted at some of the existing commercially and federally operated solid low-level radioactive waste-burial sites. Concentration levels as great as several tens of picocuries per gram have been measured. The detection limits of the borehole gamma spectrometry system now in use are of the order of 0.1 picocuries per gram