The relevance of the study is conditioned by the fact that the nuclear-power engineering requires nuclear-pure zirconium with the content of hafnium not more than 0,01-0,05 wt. %, as hafnium has high capture cross-section of «thermal» neutrons. The «dry» fluoride technology of treatment of zirconium-containing raw materials consists of the following stages: raw material fluorination with elemental fluorine, purification and separation of zirconium and hafnium tetrafluorides, metal-thermal production of zirconium, hafnium and their alloys. Purification of zirconium tetrafluoride from hafnium tetrafluoride is the most difficult operation, because their properties are very similar. The aim of the work is to determine and study the most effective way of purification of zirconium tetrafluoride from hafnium, which is suitable for use in industrial conditions. Research methods: theoretical calculation and experimental determination of separation factor of zirconium and hafnium fluorides in a melt of potassium fluoride. Results. The calculations carried out show that potassium fluoride increases the separation factor of zirconium and hafnium tetrafluorides as compared with vacuum sublimation without separation agents. The increase in the content of potassium fluoride in the fluoride mixture to be separated leads to increase in the efficiency of separation, and the separation factor reaches a maximum value when the potassium fluoride content of 0,12 wt. %. Temperature has an insignificant effect on the separation factor of zirconium and hafnium tetrafluorides. The experiments confirm the following results of the calculation: the degree of sublimation is 68,0 % and the cleaning factor is 2,59 at the initial concentration of potassium fluoride of 12 wt. %. Despite the fact that the purification coefficient in the presence of potassium fluoride is high enough, it is impossible to reduce the hafnium concentration in zirconium tetrafluoride from 2 to 0,05 % or below during one separation stage. Therefore, several successive sublimation processes of zirconium tetrafluoride were carried out. The desublimate, obtained after a double vacuum sublimation of zirconium tetrafluoride with the hafnium content of 0,82 wt. %, was sintered with potassium fluoride and it was subjected to vacuum sublimation. The obtained desublimate was examined for its hafnium content; it was mixed with potassium fluoride; the experiment was repeated several times. The experiment results demonstrate that although the purification efficiency decreases as the concentration of hafnium decreases, six decontamination cycles are sufficient to obtain reactor-grade zirconium tetrafluoride. Summary. The authors have proposed and studied the separation methods of zirconium and hafnium tetrafluorides from fluoride melts with alkaline metals. It was shown that the separation factor of tetrafluorides reaches the value of 2,59, i. e. this technique makes it possible to obtain reactor-grade zirconium tetrafluoride.