DE1181187B - Process for the production of core fuel carbides - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Kl .: COIb

Number:
File number:
Registration date:
Display day:

German KL: 12 i- 31/30

E 21969IV a / 12 i
November 15, 1961
November 12, 1964

The invention relates to a method for producing nuclear fuel carbides. Under nuclear fuel are to be understood as uranium, thorium and plutonium.

It is known to use a finely divided mixture of oxide of a nuclear fuel and at least that for the carbide formation required stoichiometric amount of carbon to form moldings and for Conversion of oxide into carbide to be heated to 1750-2375 ° C. Such granules are used for Manufacture of fuel elements used for nuclear reactors.

The resulting carbide can be granulated, for example by grinding, and granules of the desired size be sieved out. However, are. Uran-V and Thorium carbide quite hard and brittle, so that a significant proportion of the carbide is used when granulating is pulverized again. This carbide powder is difficult to keep in the working cycle.

The method according to the invention is therefore carried out in such a way that for the production of nuclear fuel carbides In granulated form from the mixture first a granulate of the desired size is formed and then the granulate is heated.

The finely divided mixture can be converted into granules by known methods, for example by pressing the mixture, crushing the compact and the granules with the sifts out the desired size. Coarser and finer granules can of course be pressed and crushed again will.

An organic binder can be added to the finely divided mixture in a manner known per se and the resulting mixture is cold-pressed, after which the compacts are crushed into granules and after sieving are heated to convert the binder into carbon. The binder can converted in a manner known per se by heating the granulate to over 800 ° C and then the reduction of the oxide can be effected by heating the granulate to 2000 ° C.

A suitable particle size of the finely divided mixture of oxide and carbon is between 1 and 5 μ. Suitable forms of carbon are carbon black or finely ground graphite. The compact can be crushed by grinding, while granules of the desired size (for example 50 to 100 μ) can be selected by seven.

The conversion of uranium oxide into carbide can be brought about by the fact that the selected Granulate heated to over 1800 to 2000 ° C at normal pressure in an argon atmosphere, for example Process for the production of nuclear fuel carbides

Applicant:
5

European Atomic Energy Community (Euratom),

Brussels
Representative:

Dipl.-Ing. R. Müller-Börner,
Berlin 33, Podbielskiallee 68,
and Dipl.-Ing. H.-H. Wey, Munich 22,
Patent attorneys

Named as inventor:

Kenneth Wallace Carley-Macauley,

Gwilym Handel Williams, Harwell, Berkshire

(Great Britain)

Claimed priority:
Great Britain 29 November 1960
(41078)

will. Thorium oxides require temperatures of at least 2000 ° C in a vacuum. For heating a drum furnace can expediently be used to avoid sintering of the granules.

As an example of the process according to the invention, its application to uranium carbide production is shown below described.

500 to 600 g of UO ₂ powder with a particle size of less than 5 μ and 100 g of deflocculated graphite powder with a particle size of at most 2 μ were mixed with 35 g of finely powdered methyl cellulose binder in a beaker. The mixture was mixed in a ball mill for 4 hours. About 200 g of the mixture were pressed in a steel mold at 1260 t / cm ² in a hydraulic press to give a cylindrical compact of 1 to IVi "diameter and 100 µ British Standard Specification This fraction was placed in a graphite crucible and placed in a carbon tube

Argon atmosphere heated according to the following scheme: 20 to 800 ° C for 6 hours,
800 to 2000 ° C for 4 hours.

..... *., 409 727/380

After cooling, the particles were removed from the crucible and sieved in a drying box. The weight loss showed that the particles consisted exclusively of uranium carbide UC ₂ ; microscopic examination confirmed. that predominantly UC ₂ was present.

Should a dilute nuclear fuel be desired, the finely divided mixture can do more than that contain the stoichiometric amount of carbon required to convert oxide to carbide.

The process is particularly focused on the extraction of intimately mixed uranium and thorium carbides applicable. Mixing granulates are difficult to produce by curbing the pure metals because a) no uranium-thorium alloy suitable for carburization can be produced in a conventional manner and because b) mixtures of finely divided uranium and thorium are difficult because of their air flammability are to be handled. Such mixed carbides can be obtained according to the invention in that one starts from a finely divided mixture of uranium and thorium oxide, which is based on the above described way is pressed, granulated and heated.

Carbide granules produced according to the invention can as pyrolytically used to manufacture products used in reactor fuel elements be coated with carbon. The coatings can be made, for example, by heating the particles at 900 ° C in a drum furnace in the presence of propane. S.

Claims (3)

Patent claims: 1. Process for the production of nuclear fuel carbides, wherein from the oxide of a nuclear fuel and at least that for carbide formation required stoichiometric amount of carbon produced a finely divided mixture which is heated to convert oxide into carbide, characterized in that that for the production of nuclear fuel carbides in granulated form from the mixture first a granulate of the desired size and then the granules are heated. 2. The method according to claim 1, characterized in that in a known manner finely divided mixture first added an organic binder and the resulting mixture is cold pressed, after which the compacts are crushed into granules and after sieving for conversion of the binder in carbon are heated. 3. The method according to claim 2, characterized in that in a known manner the binder is converted by heating the granulate to over 800 ° C and then the Reduction of the oxide is effected by heating the granulate to 2000 ° C. Considered publications:
U.S. Patent No. 2,448,479;
Nuclear Science Abstracts, 12 (1958), No. 22,
2032, Section No. 16317. 409 727/380 11.64 @ Bundesdruckerei Berlin