DE1171890B - Process for the production of uranium dioxide with a smooth surface and a round shape - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Kl .: COIg

German class: 12 η - 43/02

Number: 1171 890

File number: St 16910IVa / 12 η

Filing date: September 15, 1960

Opening day: June 11, 1964

The invention relates to a process for the production of uranium dioxide with a smooth surface and round shape.

In the context of the production of fissile material and / or potential fissile material for nuclear reactors, especially those where a suspension of granular, fissile material in a carrier liquid is used, a method is advantageous, with the aid of which granular uranium-containing material from precisely defined particle size and almost round shape can be obtained directly, d. H. without that on chemical or physical production the application of intricate separation and / or classification procedure needs to be followed while it is it is also advantageous if properties that are important for the material, namely a smooth surface, can be obtained in a reproducible manner.

According to the invention, these properties are obtained in that, in a solution of a uranium salt, after ammonia has been added to the point of precipitation, solid ammonium sulfate with stirring dissolves or a concentrated ammonium sulfate solution is added to the solution, with the proviso that the Pn value of the reaction liquid during the preferably Precipitation that takes place at room temperature is not below a temperature between 2 and 3 lying critical value is maintained that the resulting precipitate is separated off, this after heating, preferably to about 150 ° C., with an aqueous ammonia solution and the solid formed thereby dries and then reduced.

The process is advantageously carried out in such a way that the solution is added before the ammonia is added an ammonium salt, preferably ammonium nitrate, is added.

The process feature of this invention that the _pH value does not drop to the reaction liquid during the taking place precipitate formation under a lying 2-3 critical value, wherein the precipitate is subsequently separated off, can be achieved by measures known per se. However, it is particularly favorable, the initial _pH value of Uranylsalzlösung by adding such. B. to bring ammonia or ammonium hydroxide to a sufficiently high value.

The real size of the critical p _H -value which is in itself already within precise boundaries, essentially on the concentration of Uranylsalzlösung, starting from the determined. The rule is that the critical _pH value may be lower at higher concentration.

Process for the production of uranium dioxide with a smooth surface and round shape

Applicant:

Stichting Reactor Centrum Nederland, The Hague

Representative:

Dr. F. Zumstein,

Dipl.-Chem. Dr. rer. nat. E. Assmann and Dipl.-Chem. Dr. R. Koenigsberger, Patent Attorneys, Munich 2, Bräuhausstr. 4th

Named as inventor:

Marie Egidius Antonius Hermans, Theo van der Pias, Arnhem (Netherlands)

Claimed priority:

Netherlands of September 18, 1959 (243 520)

The precipitate obtained in the process according to the invention consists of uranium-containing material from complex composition, which consists of particles of smooth surface, the almost spherical shape to have. The precipitate has a grain size distribution with a sharp maximum at an exact certain particle size.

The measure of adding an ammonium salt, preferably ammonium nitrate, before adding the ammonia, admittedly, it is especially important if you start from relatively highly concentrated uranyl solutions want.

After the precipitate produced in this way, the shape and grain size distribution are retained Uranium dioxide. This can be done by converting the precipitate using aqueous ammonia with slight heating, e.g. B. to 40 ° C, and subsequent drying and reduction, z. B. by means of Hydrogen.

The uranium dioxide obtained in this way can be used very well as a fissile material in a suspension reactor use with continuous cleaning during operation (see German patent specification 948,000).

Example I.

To 50 ml of an aqueous uranyl nitrate solution containing 210 g of uranium and 1.58 g equivalent of nitrate ions per liter

409 599/220

contains, 2.0 g of solid ammonium nitrate are added. After this has dissolved, become 34 ml of 1N ammonia solution were added to the solution at a temperature of 20 ° C.

Then 5.0 g of solid ammonium sulfate are dissolved therein with stirring; a few seconds after the sulfate has completely dissolved, a yellow precipitate begins to form. The precipitation is over after 90 minutes. At the end of precipitation the _pH value of the liquid is 2.9.

9.4 g of precipitate with a content of 64.9% U, 13.9% SO ₄ - and 2.7% NH ₄ ^{+ are obtained} .

The precipitate consists of almost round grains with a smooth surface. The grain size distribution has a sharp maximum at 10 μ.

After preheating up to 150 ° C., after reaction with ammonia solution and reduction with hydrogen, granular UO ₂ with a smooth surface and almost spherical shape ao was obtained from the precipitate. The grain size distribution showed a sharp maximum at 7 μ.

Example II

To 50 ml of an aqueous uranyl nitrate solution containing 433 g of uranium and 3.62 gram equivalent of nitrate ions per liter contains 0.44 g of solid ammonium nitrate. After this has dissolved, become 30 ml of 2N ammonia solution were added to the solution at a temperature of 15 ° C.

Then 10.0 g of solid ammonium sulfate are dissolved therein with stirring; A yellow precipitate begins to form 30 seconds after the sulfate has completely dissolved. The precipitation is over after 60 minutes. At the end of precipitation, the p _H of the liquid is 2.3.

There are 12.8 g of precipitate with a content of 64.0% U, 14.4% SO ₄ - and 3.3% NH ₄ ⁺ .

The precipitate consists of almost round grains with a smooth surface. The grain size distribution has a sharp maximum at 6 μ.

After preheating to 150 ° C., after reaction with ammonia solution and reduction with hydrogen, granular UO ₂ with a smooth surface and almost round shape was obtained from the precipitate.

The grain size distribution shows a sharp maximum at 4 μ.

Claims (2)

Patent claims: 1. A process for the production of uranium dioxide with a smooth surface and round shape, characterized in that solid ammonium sulfate is dissolved with stirring in a solution of a uranyl salt after ammonia has been added to the point of precipitation, or a concentrated ammonium sulfate solution is added to the solution with the proviso that the _pH value of the reaction liquid during, preferably at room temperature, taking place precipitate formation is not held under a lying 2-3 critical value, which comprises separating the resulting precipitate, this after heating, preferably to about 150 ° C, with an aqueous ammonia solution and the solid formed thereby dries and then reduced. 2. The method according to claim 1, characterized in that the solution before Adding the ammonia, an ammonium salt, preferably ammonium nitrate, is added. 409 599/220 6.64 © Bundesdruckerei Berlin