There have been many published mathematical models that, to varying degrees of sophistication, attempt to describe dynamic thickener behaviour. CSIRO has undertaken to develop a model under industry sponsorship._x000D_
Recently developed instruments such as the floc density analyser and natural gamma-ray gauge have enabled new data to be collected from plant thickeners for model validation and development. The principles behind the use of the natural gamma-ray gauge are described and the possibilities for its use as a control instrument in the bed have been examined. A simple nomograph illustrates how the gamma-ray gauge data can be used to predict steady state underflow consistency and bed Position.