Preparation of high-purity ZrF4 and HfF4 for optical fibers and radiation-resistant glasses

The separation coefficients of ZrF4 (HfF4) and metal fluoride impurities in the process of vacuum sublimation between 900 and 1200 K in the molecular vaporization regime were calculated. The separation coefficients were found to decrease in the order CrF2 > MnF2 > NiF2 > CoF2 > MnF3 > FeF2 > AlF3 > CrF3 > CuF2 > FeF3. The conditions for purification of ZrF4 and HfF4 by vac uum sublimation were optimized. The total impurity content in both fluoride s was found to increase with the product of the evaporation rate per unit a rea and the degree of evaporation. Fe was found to be the most difficult-to -remove impurity in ZrF4. and HfF4. The production rate of the sublimating plant is about 100 kg/year of ZrF4 and HfF4 sublimates. ZrF4 was used to pr epare optical fibers for laser applications and noncontact fiber sensors fo r monitoring the composition and temperature of liquid radioactive waste. F luorohafnate glasses were used to fabricate radiation-resistant scintillati ng modules of dimensions 20 x 30 x 150 mm, weighing less than or equal to0. 5 kg.