LU84367A1 - METHOD FOR PRODUCING CORE REACTOR FUELS - Google Patents

Description

Λ r I / 2C57 EUROPEAN ATCXCdTSIXSCHAFï (EUHÂTOIi) P at eutanmeldung

Process for the production of nuclear refractory fuels

Inventor: K. RICHTER

k G. KRAHER

The invention relates to a process for producing nuclear reactor fuels of the I-TX7 type, where I * 'is an actinide metal and X is nitrogen and / or carbon.

For fast breeder realotors, type XX fuel (e.g. uranium-plutoniunkarbide) is generally used because of a higher breeding rate and shorter. Doubling time in comparison with oxide fuel is of great importance. Mixed Careouitride come in stretcher.

A / Λ / / Λ r - c. -

Technological production mainly takes place through the carbothermal reduction of uranium oxide-plutonium ozone-carbon mixtures. These oxide-carbon powder mixtures are compressed into tablets, disks, etc. and heated under vacuum, inert gas or nitrogen at temperatures from approx. 1400 ° C to 1800 ° C for several hours. This produces sintered bodies of the desired chemical composition with a density of 40-6θ'_ theoretical density (TD).

With the insert in the reactor, however, tablet diameters> 8O7Î TD are required. The sintered bodies are therefore crushed and ground with Δ0 - cQ) o TD (hammer mills, ball mills, vibration mills, etc.). The surface of the powders is increased by grinding, the reactivity of the powders is increased. These powders are then pressed into the desired shape and sintered. The tablet densities are between 80 - 97¾ TD.

In addition to a certain amount of equipment and time, the process step of shredding and grinding leads to strong dust formation within the product-affected working volume (glove box equipment). The high proportion of dust within the working volume leads to considerable radiation exposure for the personnel and also involves a safety risk, since fine powders of KX separants are pyrophoric.

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 Oo and HgO contents (generally <50 PP ^ O).

Most technologically relevant processes are based on the principle of carbothermal reduction by Ouyden and are based on press-sinxer technology (mixing MOg + C, press; carbothermal reduction; ore-grinding of the reaction product HX; press; sinter).

'You found that the reaction product was directly compacted, i.e. without previous crushing and throat, and then, tnemiscr. oehar.deln can at high temperature, 3.3. IhOO - 1800 ° C.

. The "direct feeding process", like most lüC nuclear fuel generation processes, is based on the carbothermally shy reduction of the Ouyde ozw. who he.

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Mixtures. The ox.yd-x-carbon mixtures are pressed in a specific shape adapted to the geometry of the brewing product and thermally treated (at 1300-l800 ° C under vacuum or inert gas or nitrogen or nitrogen inert gas). After the thermal treatment, the reaction product is in the desired chemical composition in the form of j tablets with predetermined dimensions and a material density of 40-60fo. The individual tablets are directly in a normal cold press, i.e. in contrast to conventional processes without previous grinding and grinding, charged and post-compacted. Subsequently, "·" the compacts are brought to the desired density and dimension by re-sintering at 1400 - 180 ° C under vacuum or inert gas or nitrogen or an inert gas / nitrogen mixture.

This method eliminates the step "shredding-balding" (see procedural scheme, page A '., Which is used in the previous methods ".

This has the following advantages over previous manufacturing processes: - less equipment and time required - handling of KX-type powder with its great affinity for oxygen is eliminated - a dust content reduced to practically shell.

The two previous points result in less effort for the protective gas atmosphere required for handling (the affinity for oxygen of the KX 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. Fission flow control is made easier.

It is much more possible to charge the dies of the presses by means of compacts, instead of powders, i.e.

- simple and quick loading of the matrices - simple and easily controllable material flow / · / κ.-4- - short and. cheaper matrices due to the low compression ratio - no metallic impurities, which are the result of the usual grinding and grinding - great variation options in terms of fuel structure (e.g. pore size, 11 axis intercalcifications) by grinding the corresponding parameters of the starting materials.

The new process has already been tested in practice. For example, IJran

Plutonic acid carbide fuels are manufactured and characterized with various fuel densities and residual oxygen levels.

Pellet density: 7S; 1 - 86f_- TB. Bs even have samples at 90? » TB

Oxygen content: <100 ppm and approx. 2000 ppm

Ceramic cuts of the fuels are available.

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Process scheme Production of MX fuels by carbothermal reduction of the oxides ^ a "0XJ, d coal I I“ ranoxyd carbons.

MIX olyd ° nlul "" fabric MIX ^ ’^ ornu, n 'fabric

Jt ____ _____ PRESS. Tablets! DISCS PRESSES SbîSS * KARBOTHERM,}! £ ** I KARBOTHERM. ™ i *; "ACTION 1300. I800, c REDUCTION, ^ 00., 800" c CRUSH [GRIND Vibrati onmahlhl e PRESSING tablets6 AFTER- cold press COMPRESSING tablets______

Vacuum, inert gas Vacuum, inert gas SINTERN N2 or inert gas / N2 Nach- or inert gas / N2

1400 - 1800% SINTER 1400 - 1800 ° C

previously common procedure new procedure

Claims (2)

1. A process for the preparation of Xernreaktorfosels of type 3K, wherein Γ · ϊ represents an Actinidenmetsll and / 1 carbon ur.d / cderststoff, wherein the Actinidécria or the .Actinide Oxyden ait carbon mixed, pressed and carbothermally reduced, characterized in that that the Redulctionsprodulct is directly densified and then thermally treated at high temperature. 2. The method according to claim 1, characterized in that the thermal treatment takes place at a temperature of 1400 - 1800 ° C. * #L_ \ • θ 'nu V -. Luxembourg, le h »te Umm-mi:,] '~ y * ~ ^ c \'