Neutron induced radioactivity for mineral exploration

Borehole neutron activation-gamma-ray spectrometry is a useful method for mineral exploration. Isotopic or accelerator neutron sources are used with either scintillation or semiconductor detectors in the borehole tools depending on the application, rock formation, required measurement time, etc. The basic neutron processes in rock formations are summarized to point out the problem of spectrometer calibration. The source-to-detector distance is an important consideration to achieve optimum sensitivity. There are several possible solutions of the calibration problem. Some of these are demonstrated by applications of neutron activation to mineral exploration in the field. Although many problems still need to be solved to make borehole neutron-gamma-ray spectrometry a more general analytical tool, the method is a powerful qualitative exploration device applicable to many elements in most rock formations. Under certain conditions, e.g., in a coal seam, it can also be a good quantitative tool. 83 references