Optical methods for research of uranium hexafluoride under conditions imitating the atmosphere

Capabilities of optical methods in real-time monitoring of uranium hexafluoride and products of its hydrolysis in the air over the production areas have been studied experimentally in the process of hydrolysis of uranium hexafluoride under controlled conditions imitating the atmosphere. The scattering and absorption coefficients were used to study the process of formation and kinetics of aerosols at interaction of UF₆ with water vapor. It has been shown that time of aerosol formation is mostly determined by time of the hydrolysis, and the lifetime of aerosols is determined by diffusion and convective processes, as well as coagulation. At low concentrations of the parent material the effect of coagulation on the process of aerosol formation is insignificant because of low collision probability of particles. When initial concentration of UF₆ (up to 20 g·m^-3) increases hydrolysis occurs faster, and particles are generated during minutes and less. At tenfold excess over the H₂O, concentration the intense (active) volume hydrolysis of uranium hexafluoride occurs with formation of aerosols even at the low concentration of UF₆, and this hydrolysis terminates within first 20 min. At lower concentrations of initial substances (∼25 μg·m^-3), the process of intense hydrolysis proceeds slower and generation of aerosol has no pronounced time interval. It should be emphasized that termination of the intense hydrolysis does not mean complete termination of the reaction that indicate presence of a "penetrative fraction" of UF₆, which continues to react with H₂O and hydrolysis products more than hour. The experiments showed that optical methods allow rather reliable detection of low concentrations of radioactive and toxic admixtures at UF₆ hydrolysis at the level exceeding the MPC, and the equipment based on these methods is capable of providing the reliable monitoring of pre-emergency situations; in addition, this equipment is relatively cheap and convenient in use.