DE3327921A1 - METHOD FOR PRODUCING CORE REACTOR FUELS - Google Patents

Description

PATENT LAWYERS

1OOO BERLIN-DAHLEM 33 ■ PODBIELSKIALLEE 68 8OOO MUNICH 22. Wl D EN M AYER STRASS E 4g

BERLIN: DIPL.-INS. R. MÜLLER-BORN ER

MUNICH: D1PL.-ING. HANS-HEINRICH WEY

DIPL.-INS. EKKEHARD KORNER

EUROPEAN ATOMIC COMMUNITY (EURATOM)

Berlin, July 29, 1983

Process for the production of nuclear reactor fuels

(Priority: Luxembourg, No. 84 367 of 6.9.82)

6 pages description with 2 claims 1 process scheme summary

MB / Ma - 27,933

BERLIN: TELEPHONE (O3O) 8312O88 MUNICH: TELEPHONE (08S) 225585

KABELrPROPINDUS-TELEX: 184057 KA B EL: P ROPI N DU S TELEX: 524244

The invention relates to a method for producing nuclear reactor fuels of the MX type, where M is a Actinide metal and X represents nitrogen and / or carbon, the actinide oxide or the actinide oxides mixed with carbon, pressed and! carbothermally reduced.

Type MX fuel (e.g. uranium-plutonium carbide) is generally used for fast breeder reactors because of its higher Great importance is attached to the breeding rate and shorter doubling time compared to oxide fuel. Mixed Carbonitrides are also possible.

The technological production takes place mainly through the carbothermal reduction of uranium oxide-plutonium oxide-carbon mixtures. This oxide-carbon powder mixture ^ be compressed into tablets, wafers, etc., and under vacuum, inert gas or nitrogen b ii temperatures of about 1400 ⁰ C to 1800 ⁰ C heated for several hours. This creates sintered bodies of the desired chemical composition with a density of 40 to 60% of the theoretical density (TD).

However, tablet densities> 80% TD are required for use in the reactor. The sintered bodies are therefore crushed and ground with 40 to 60% TD (hammer mills, ball mills, vibration mills, etc.). The grinding increases the surface area of the powder and increases the reactivity of the powder. These powders are then pressed into the desired shape and sintered The tablet densities are between 80 and 97 % TD.

The process step of comminuting and grinding leads to a large amount of equipment and time, in addition to a certain amount of time and equipment

Dust formation within the working volume in contact with the product (glove box devices). The high proportion of dust within de; On the one hand, the volume of work leads to considerable radiation exposure of the staff and, on the other hand, involves a safety risk, since fine powders of MX fuels are pyrophoric
are.

In addition, because of the high affinity of the powders produced for oxygen, this process step must be carried out under an inert gas atmosphere with very low residual 0 "and H" O contents
(generally C50 ppm).

Most of the technologically relevant processes are based on the principle of carbothermal reduction of oxides and
are based on press-sintering technology (mixing M0 + C, press carbothermal reduction; crushing-grinding of the reaction product MX; pressing; sintering).

According to the invention it is proposed that the reaction product be used directly, that is to say without prior comminution and grinding,
recompressed and then at high temperature, e.g. B. 1400 to 1800 ° C, is thermally treated.

The "direct pressing process" is based, like most of the MX core fuel production processes, on the carbothermic reduction of the oxides or their mixtures. The oxide Kohlenstofhechnik mixtures are in a particular geometry of the final product matched pressed mold, and thermally treated (at 1300 to 1800 ⁰ C under vacuum or inert gas or nitrogen or nitrogen-inert gas mixtures). After the thermal treatment, the reaction product is in the desired one
chemical composition in the form of tablets with

given dimensions and a material density of 40 to 60 % . The individual tablets are in a normal cold press directly, α. H. In contrast to the usual methods without prior crushing and grinding, batched and recompacted. The compacts are then brought to the desired density and dimensions by re-sintering at 1400 to 1800 ° C. under vacuum or inert gas or nitrogen or an inert gas-nitrogen mixture.

This new process eliminates the process step "Mincing-Grinding" used in previous methods. Further details can be found in the attached process diagram.

This results in comparison to previous manufacturing processes the following advantages:

- less equipment and time,

- the handling of MX-type powder with its great affinity not applicable to oxygen,

- a dust content reduced to practically zero.

The two previous points result in less effort for the protective gas atmosphere required for handling (the affinity for oxygen of the MX fuels depends on their specific surface). The risk of self-ignition from powder or dust is avoided. The radiation exposure of the staff is significantly reduced. The flow of fissile materials is facilitated.

Furthermore, the dies of the presses can be charged with compacts instead of powders; H.

- quick and easy charging of the matrices,

- simple and easily controllable material flow,

- short and cheaper dies due to the low compression ratio,

- no metallic impurities, which were previously common crushing and grinding,

- Great possibilities for variation with regard to the fuel structure (e.g. pore size, post-sintering behavior) Choice of the appropriate parameters of the starting materials.

The new process has already been tried out in practice. It was z. B. Uranium-plutonium carbide fuels are produced with different fuel densities and oxygen residues and characterized.

Pellet density: 78% to 86 % TD. There are even samples with 90% TD,

Oxygen content: <100 ppm and approx. 2000 ppm.

Ceramographic cuts of the fuels are also located before.

MB / Ma - 27,933

933

Int. Cl. ³ : G 21 C 3/58

Filing date: July 29, 1983

Disclosure date: March 8, 1984

Process scheme "Production of MX fuels by ltarbothermal reduction of the oxides "

PRESS

Uranium oxide _{raw materials}

MIXING plutonium _stiff oxide

Cold press tablets, slices

^{VacuU! N} > inert gas I. μ or inert gas / N ₂

REDUCTION ₁₃₀₀ . ₁₈ oo »c

-7rni / i γτμγπμ hammer mill CRUSHING Ball Mill

Vibration level

PRESS

Cold press tablets

Vacuum, inert gas SMERN N ₂ or inert gas / N

HOO - 1800 "C MIX

Uranium oxide _coals . Plutonium oxide

material

PRESS

Cold press tablets

i / ADDHTurDM vacuum, inert gas KARBOIHERM, _{n or} . inert gas / N ₂

REDUCTION ₁₃₀₀ . ₁₈₀₀ o _C

RECOMPRESSION

Cold press tablets

MAKE SINTERING

Vacuum, inert gas N ₂ or inert gas / N ₂

- 1800 ⁰ C

previously common procedure new procedure

EUROPEAN! ·: ATOMGKMKINSClIAFT (EURATOM)

Claims (2)

Claims 1st Process for the production of nuclear reactor fuels "- of the MX type, where M is an actinide metal and X is carbon and / or nitrogen, the actinide oxide or actinide oxides being mixed with carbon, pressed and carbothermally reduced, characterized in that the reduction product is directly recompressed and is then thermally treated at high temperature. 2. The method according to claim 1, characterized in that the thermal treatment at a temperature of 1400 - 1800 ⁰ C takes place. MB / Ma 27 9 33 BERLIN: TELEPHONE (O3O) 8312Ο88
CABLE: PROPINDUS TELEX: 1Θ4Ο57 MUNICH: TELEPHONE IQ89) 235585 CABLE: PROPINDUS TELEX: 524244