The principal phenomena and processes occurring in the ISP furnace as well as the radiotracer methods for the investigation of charge flow dynamics have been discussed. The65Zn radioisotope was applied for investigations of the batch movement dynamics. The tracer was obtained on the way of direct neutron activation of the zincflead sinter in the nuclear reactor. The activity distribution measurements were performed by taking-out the samples. Three series of experiments were carried out in order to examine the batch material movement and its dependence on the furnace charging manner. The influence of the process parameters on the batch movement has also been discussed. The shortest descent time of the charge material is strongly favoured by the joint system of charging the furnace (i.e. coke and sinter together).