Experimental and computational study of particle formation kinetics in UF₆ hydrolysis

Abstract

The formation and growth of UO2F2 particles by gas-phase UF6 hydrolysis remains of interest to actinide chemistry researchers.

Formation of Aerosol Nanoparticles by Gas-Phase Hydrolysis Reaction of Uranium Hexafluoride

“…Using a reasonable value for the activation energy of self-diffusion, we also computationally verified the primary particle size and predicted a size range for the UO2F2 primary particles comparable to that estimated from experiments (Cheng et al 2020). The results strongly suggest that the volume-driven coalescence process assumption used in the derivation of the primary particle model was reasonable.…”

“…These results were unachievable in the past because of a lack of suitable aerosol instruments. We analyzed data for particle growth and formation rates and found that they were proportional to ω and the aerosol reactor elapsed time (τ) (Cheng et al 2020). The results provided a means to quantitively predict the size and size distribution of the uranyl particles at any given ω and τ, which can be used to design a scale-up pilot plant to theoretically make much high-quality nuclear fuel powder.…”

Kinetic investigation of the hydrolysis of uranium hexafluoride gas

“…Studies evaluating the safety implications of small or large releases of UF 6 within a processing facility have been performed previously, [1][2][3] as it is well known that this material undergoes a hydrolysis reaction in ambient air according to the simplied reaction: UF 6 (g) + 2H 2 O(g) / UO 2 F 2 (s) + 4HF(g) producing both uranium particulates and hydrouoric acid vapor. Recent work 4 has explored the formation of the uranium particulate materials but the precise molecular mechanism of the initiating reaction has yet to be veried. Previous efforts to characterize this reaction have focused on spectroscopic measurements [5][6][7] and computational studies.…”

Progress in Uranium Chemistry: Driving Advances in Front-End Nuclear Fuel Cycle Forensics

“…Recently, Cheng et al studied the formation and growth of primary UO 2 F 2 particles produced by gas-phase hydrolysis of UF 6 . 108 For the conditions investigated, they found UO 2 F 2 primary particle formation and growth was strongly dependent on the H 2 O molecules available. Higherhumidity conditions resulted in larger primary particle sizes with a peak aerosol mobility diameter of approximately 8 nm, whereas water-deprived reaction conditions produced smaller primary particles with a peak aerosol mobility diameter of approximately 3.6 nm.…”

“…Overall, the observations of Kips et al compare more favorably with Pickrell’s observations than those of Lux. Recently, Cheng et al studied the formation and growth of primary UO 2 F 2 particles produced by gas-phase hydrolysis of UF 6 . For the conditions investigated, they found UO 2 F 2 primary particle formation and growth was strongly dependent on the H 2 O molecules available.…”