Neutron Moisture Meters: The Effects of Various Soil Parameters

Multigroup nuclear reactor codes were used to determine the effect of soil parameters on the thermal neutron flux at the detector of a neutron moisture meter. The parameters studied were the matrix density, neutron absorption and scattering cross sections, and the moisture content. The source-detector separation was also considered. Polynomial expressions, which were fitted to the variations in the neutron flux resulting from parameter changes, can be incorporated into a simple computer code and used to calculate the moisture content from an input of soil parameters and the detector count rate. This allows the rapid analysis of moisture meter data acquired in such highly variable soil systems as mine overburden heaps. Comparisons of the calculated and measured moisture contents of two different Australian soils are given.