This paper presents residence time distribution (RTD) functions acquired in radioisotope tracer experiments carried out on a copper ore thickening, filtration and drying system. The radioactive isotope (CU)-C-64 was selected as a tracer for copper. It was obtained through the activation of the natural ore concentrate in a nuclear reactor. The tracer data lead to proposal of kinetic models of the investigated processes and determination of their parameters. The analysis of the RTD functions as well as modeling results show that there exist stagnant zones and by-passes that influence the efficiency of the dewatering system. (C) 2004 Elsevier B.V. All rights reserved.