Reaction Model for Fluorination of Uranium Dioxide Using Improved Unreacted Shrinking Core Model for Expanding Spherical Particles

Abstract

A gas-solid reaction model is developed to represent the fluorination of uranium dioxide (UO 2 ), which consists of a two-step reaction: the formation of a solid intermediate of uranyl fluoride (UO 2 F 2 ) on the core of unreacted UO 2 and the consumption of UO 2 F 2 . The model is an extension of the unreacted shrinking core model with a shrinking spherical particle and takes into account particle expansion resulting from the density difference between UO 2 and UO 2 F 2 . This model successfully represents the initial expansion of the particle by the formation of the low-density UO 2 F 2 intermediate. The accuracy of this model is higher than that of the original model, which does not allow particle expansion.

Nitrogen Trifluoride-Based Fluoride- Volatility Separations Process: Initial Studies

“…It is possible that fluorination of metal and metal oxide surfaces using more aggressive reagents such as fluorine (Ogata et al 2004;Homma et al 2008), bromine pentafluoride (BrF 5 ), ClF 3 (Labaton 1959), etc., follows the "shrinking core" reaction model or similar physical kinetic behavior, but it also could be that the reagent reactivity is such that product barriers, for instance, are fluorinated away with equivalent facility as the starting material. Thermoanalyses of fluorination reaction with aggressive fluorinating agents show little evidence of sequential product formation; rather, volatile production appears to be kinetically favored, and the final process of volatilization likely dominates the observable.…”

Desulfurization Process and Kinetics of Fe/Activated Carbon Removal of H2S at Low Temperature

“…The desulfurization reaction is a typical noncatalytic gas-solid phase reaction. [3][4] The unreacted shrinking core model is used to illustrate the process of non-catalytic gas-solid reaction. [5][6] Feng Y and Li Y [7] studied the desulfurization kinetics of Fe 2 O 3 desulfurizer using unreacted shrinkage nucleus model.…”