|
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 H20, 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 H20 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.
|
