CS220191B1 - Process for preparing uranium oxide - Google Patents

Abstract

The invention relates to a method for preparing uranium dioxide by reducing hexavalent uranium compounds. It solves the problems associated with high temperatures in the preparation of uranium dioxide. Its essence lies in the fact that hexavalent uranium compounds are treated with a melt of alkali metal cyanide, or a mixture thereof.

Description

The invention relates to a process for the preparation of uranium dioxide by reduction. It is particularly advantageous in the recovery of uranium and in the treatment of the enriched uranium fluoride.

Uranium dioxide, which is an important nuclear fuel and intermediate in the processing of uranium raw materials, has been prepared to a large extent by reducing uranium dioxide-uranoic oxide with hydrogen gas at temperatures around 900 ° C. This method presents the usual problems of high temperature and hydrogen; forming; with air explosive mixtures.

These disadvantages are overcome by the process for preparing uranium dioxide by reducing the hexavalent uranium compounds, in particular uranyl compounds, according to the invention. It is based on the fact that the reduction is carried out in an alkali metal cyanide melt environment, most preferably potassium or sodium salt, or mixtures thereof at temperatures above their melting point at normal pressure.

An advantage of the process for the preparation of uranium dioxide according to the invention is that it is possible to use a reaction vessel made of ceramic material and some metals, for example nickel, without atmosphere control. The melt guarantees high crystallization pressures leading to a perfectly crystalline product and eliminates the possibility of pyrophoricity. The reduction takes place almost immediately. All uranyl compounds, except those whose anions have strong oxidizing effects, such as nitrates, chlorates and the like, can be processed and lead to explosions at elevated temperatures. If anions are also reduced in the melt of cyanides such as arsenites, selenites, tellurates, mixed products are formed.

The invention is described in more detail by way of examples.

Example 1

Uranium dioxide prepared by mixing 20 g of potassium cyanide and 3 g of uranyl carbonate. The mixture was melted in a porcelain crucible at 650 ° C for about 20 minutes. The yellow substance immediately melts in the melt and drops to the bottom of the vessel. After the melt had precipitated with water, preferably hot, the black powder product formed was filtered and dried.

Example 2

The molten potassium cyanide in an oxide ceramic crucible was charged at 650 ° C with · 15% calculated on the basis of cyanide, uranyl phosphate. The yellow fabric immediately turned black. The product was isolated as in Example 1. Processing of phosphates presents considerable difficulties in other methods.

Example 3

The ground mixture of sodium cyanide and uranyl fluoride, which is the product of the hydrolysis of uranium fluoride, was melted in a procellate dish at 600 ° C. The original yellow-white fabric immediately turned black. After dissolving the cyanide with hot water, uranium dioxide was filtered off and dried at 110 ° C.

Claims (1)

A process for the preparation of uranium dioxide by reducing hexavalent uranium compounds, characterized in that the hexavalent uranium compounds are treated with uranium by a melt of an alkali metal cyanide or mixtures thereof.