加圧水素還元によるUO₂の析出に関する研究

抄録

This paper is concerned with the kinetic study on the precipitation of UO₂ from various carbonates solutions in the presence of Ni powder by hydrogen pressure reduction.
The testing solutions are four different uranyl carbonate solutions prepared by the dissolution of refined UO₃ in K₂CO₃, Na₂CO₃ (NH₄) ₂CO₃ and ethylenediamine carbonate (EDA-CO₃).Experiments have been done in 2l stainless autoclave, equipped with the sampling device and the magnetic induction agitation system.
The results obtained are as follows:
(1) The precipitation rate of UO₂ from these carbonates solutions varies with cation species. It increases in order of K, Na, NH₄, and EDA.
(2) The activation energies from these carbonates solutions are 11.4, 14.1, 18.3 and 19.0kcal/mol respectively.
(3) There is a correlation between the precipitation rate and the hydrogen solubilities in various carbonates solutions.
(4) The precipitation rate increases in proportion to the amount of Ni powder.
(5) The concentration of carbonates influences the precipitation rate. In (NH₄) ₂CO₃ solution, the rate is in converse proportion to the square of its concentration.
(6) The precipitation rates increases in proportion to the square root of hydrogen partial pressures.
(7) From above results, the following rate formula is obtained. -d[U]/dt=K·S·P_H21/2·[M₂CO₃]-ⁿ·exp (-E_M/RT)