This article presents a study on the kinetics of the uranium conversion process, consisting in the reduction of uranium trioxide to uranium dioxide using hydrogen gas at temperatures of 500°C, 600°C and 700&...This article presents a study on the kinetics of the uranium conversion process, consisting in the reduction of uranium trioxide to uranium dioxide using hydrogen gas at temperatures of 500°C, 600°C and 700°C. Hydrogen concentrations used in the flow were 0.25 M, 0.50 M and 0.75 M. The mechanism established for the study of the kinetics of reduction of uranium trioxide was through the formation of an intermediate compound, U3O8. For this reason, these tests were divided into 2 stages: the first one the reduction from UO3 to U3O8, and second one from U3O8 to UO2. The results of each test were quantified by the release of H2O(g) produced by both reactions. Tests showed that the ideal working conditions are for hydrogen concentration flows of 0.75 M and temperatures in the range of 500°C - 600°C, with the intent to decrease the occurrence of side reactions that interfere with the process.展开更多
This article shows the modeling of a uranium dioxide production reactor using COMSOL Multiphysics software program in its 4.3b version. The model was made using 3 kinds of studies: momentum, heat and mass transport, i...This article shows the modeling of a uranium dioxide production reactor using COMSOL Multiphysics software program in its 4.3b version. The model was made using 3 kinds of studies: momentum, heat and mass transport, in order to determine the influence of the most important operational parameters: UO<sub>3</sub> reaction rate, composition and flow of the reduction gas, the initial temperature reactor and the reducing gas. The operational parameters evaluated were the followings: constant gas flow of2.5 L/min, initial hydrogen concentration of 0.25, 0.50 and0.75 M, and initial temperature of 400°C. The obtained results allow to conclude that under these working conditions, uranium dioxide is obtained virtually instantaneous and, with concentrations close to 0.5 M H<sub>2</sub> in the reducing gas, the process can operate continuously and autogenously, without applying additional energy and temperatures around 600°C.展开更多
文摘This article presents a study on the kinetics of the uranium conversion process, consisting in the reduction of uranium trioxide to uranium dioxide using hydrogen gas at temperatures of 500°C, 600°C and 700°C. Hydrogen concentrations used in the flow were 0.25 M, 0.50 M and 0.75 M. The mechanism established for the study of the kinetics of reduction of uranium trioxide was through the formation of an intermediate compound, U3O8. For this reason, these tests were divided into 2 stages: the first one the reduction from UO3 to U3O8, and second one from U3O8 to UO2. The results of each test were quantified by the release of H2O(g) produced by both reactions. Tests showed that the ideal working conditions are for hydrogen concentration flows of 0.75 M and temperatures in the range of 500°C - 600°C, with the intent to decrease the occurrence of side reactions that interfere with the process.
文摘This article shows the modeling of a uranium dioxide production reactor using COMSOL Multiphysics software program in its 4.3b version. The model was made using 3 kinds of studies: momentum, heat and mass transport, in order to determine the influence of the most important operational parameters: UO<sub>3</sub> reaction rate, composition and flow of the reduction gas, the initial temperature reactor and the reducing gas. The operational parameters evaluated were the followings: constant gas flow of2.5 L/min, initial hydrogen concentration of 0.25, 0.50 and0.75 M, and initial temperature of 400°C. The obtained results allow to conclude that under these working conditions, uranium dioxide is obtained virtually instantaneous and, with concentrations close to 0.5 M H<sub>2</sub> in the reducing gas, the process can operate continuously and autogenously, without applying additional energy and temperatures around 600°C.
