Radial distributions of 60Co contaminants surrounding wellbores at the Hanford Site

The Department of Energy is sponsoring large scale environmental characterization and monitoring efforts at the Hanford Site to determine the properties and movements of plumes containing radioactive contaminants. Halliburton is participating in a Cooperative Research and Development Agreement with DOE-Richland and its contractors to adapt several nuclear borehole geophysical logging systems to the arid Hanford conditions. A number of the more than 4000 Hanford monitoring wells are suitable for various types of logging measurements. In particular, the distributions of gamma-ray-emitting radionuclides can be mapped with spectroscopy instruments. During the demonstration phase of this project gamma ray spectroscopy data were gathered with a Compensated Spectral Natural Gamma sonde in Well W15-7 in the 200-West Area. Using “whole” spectrum techniques developed for oil field applications these spectroscopy data reveal information about the radial distribution of ⁶⁰Co contaminants. Specifically, below the water table, many of the detected gamma rays originate from ⁶⁰Co which appears to be adsorbed onto corroded steel well casing. The relevance of these results to environmental remediation at the Hanford Site is discussed since it appears that some radioactive contamination may be more localized than currently assumed