Gamma-ray density and thickness gauges using ultra-low activity radioisotope sourcesfillin

Most commercial nuclear density gauges use either 137Cs or 60Co sources of activity between about 185 and 1850 MBq (5 and 50 mCi). In the current work, density and thickness gauges that use ultra-low activity gamma-ray sources that are exempt from licensing requirements have been investigated. Results are reported on gauges that use a 1 MBq 22Na source for determining slurry density in the CSIRO UltraPS slurry particle size analyser and for determining belt loading in the CSIRO on-conveyor belt microwave moisture gauge.