DE1667653A1 - Process for the production of nuclear fuel nitrides from fluorides - Google Patents

Description

NUKEM

Nuclear Chemistry and Metallurgy Society m.b.H.

Wolfgang b. Hanau

Process for the production of nuclear fuel nitrides

from fluorides.

In the preprocessing of nuclear fuels, these are part of the process often referred to as fluoride. So far it was known that these fluorides by conversion with alkaline earth metals to the nuclear fuel be converted in metallic form. For example, uranium tetrafluoride became uranium metal and plutonium tetrafluoride Plutonium metal produced as a nuclear fuel.

Recently, however, connections have played a role in Roaktortechnik of nuclear fuels, as long as they are resistant to high temperatures and high nuclear densities have a preferred role. Among these, the nitrides are considered to be particularly promising. So far have been Nitrides of nuclear fuels due to the reaction of elemental nitrogen or ammonia is produced with the metals or hydrides (uranium and plutonium). In addition, there are still in the literature Reactions of solutions of nuclear fuel in metallic form (amalgams) with ammonia have become known.

The nitrides of the nuclear fuels are not formed in these ways directly as mononitride. However, as these, due to their favorable physico-chemical properties (density, temperature resistance, Crystal lattices) are desired, they have to be produced from the higher nitrides by heating.

Ks is also known to be uranium trichloride and uranium trichloride by high-temperature ammonolysis via the intermediate stages convert the amido compound into uranium nitrides, which are then built into uranium mononitride.

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However, uranium trichloride and uranium tetrachloride have practically none in the chemical processing of nuclear fuels Can gain importance, especially because their production is cumbersome.

Surprisingly, it has now been found that uranium tetrafluoride and uranium trifluoride if the reaction is carried out appropriately by high-temperature ammonolysis can be converted into uranium nitride or uranium mononitride. It is essential that the residence time the ammonia in the system and the materials are chosen so that there is still enough undissociated ammonia for the high temperature turammonolysis is available.

The new method according to the invention offers the decisive Advantage that when processing. Nuclear fuel as an intermediate stage, the nuclear fuel fluoride is now available directly can be used as a starting product for the production of nitrides.

Example 1 (uranium mononitride from uranium tetrafluoride)

In an aluminum oxide tube with a diameter of 20 mm, 0.2 g uranium tetrafluoride was reacted in a platinum boat for 2 hours with carefully dried ammonia gas at a temperature between 890 and 920 ^° C. and a flow rate of 1800 ml ammonia per hour. The obtained fluoride-free product UN, _Q was then at a temperature around

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1 100 0 degraded to uranium mononitride in vacuo at 10 torr.

Example 2 (uranium mononitride from uranium trifluoride)

In an aluminum oxide ear, 0.2 g uranium tetrafluoride was initially reduced to UF using hydrogen in a known manner. This was then superiors in the course of 1 hour at 800 ⁰ C with a carefully

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BATH ORIGINAL

trooknetem ammonia was reacted at a flow rate of 1 800 ml of ammonia per hour, Pas obtained fluoride-free product UX _ü, - as indicated in Example 1 - reduced in vacuo to Uranmononitrid.

Example 3 (uranium mononitride from uranium hexafluoride over ammonium pentafluoruranate IV,)

Solid aminonium pentafluorouranate IV was produced in a cylindrical reactor vessel by simultaneously introducing uranium hexafluoride and ammonia at approx. 300 ° C. As shown in Example 1, 0.2 g of this product were converted to uranium nitride UK, _n . This was - as indicated in Examples 1 and 2 - degraded to uranthate ion nitride.

Example h (plutonium nitride from plutonium tetrafluoride)

In an aluminum oxide tube 20 mm in diameter, 0.3 g of plutonium tetrafluoride was reacted in a platinum boat for 3 hours with carefully dried ammonia gas at a temperature between 920 and 9 '* 0 ° C. and a flow rate of 2,000 ml of ammonia per hour . The fluorine-free product obtained was then heated at a temperature of 1 05
nitride degraded.

perafcur of 1 050 ⁰ C in a vacuum 10 "" Torr to plutonium mono-

Example 5 (uranium zirconium nitride from a mixture of uranium tetrafluor id / zircon te met luo rid)

0.2 g of a homogeneous mixture of uranium tetrafluoride and zirconium tetrafluoride were placed in a zirconia tube in a platinum boat 2 hours with carefully dried ammonia

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gas and at a temperature between S70 and 920 ° C and a flow rate of 1,800 ml ammonia per hour. The obtained fluoride-free mixed nitrides were then degraded to the mixed mononitrides at a temperature of 1,200 ° C. in a vacuum of 10 Torr. The mixed crystal formation was proven radiographically.

Example 6 (uranium plutonium nitride from mixed uranium / Plutoniuinf luori den)

In an aluminum oxide tube, 0.3 g of the h : mixed fluorides of uranium and plutonium were reduced in a known manner with hydrogen to the trifluorides. These were then reacted in the course of 1 1/2 hours at 900 ^° C. with carefully predried ammonia and a flow rate of 2,000 ml of ammonia per hour. The nitrides obtained

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were degraded to the mononitrides at a temperature of 1,100 ° C. in a vacuum of 10 torr. The presence of a homogeneous Solid solution of uranium-plutonium-nitride was X-rayed proven.

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Claims (7)

- 5 - PATKNTANS PRÜCTIE 1. A process for the production of nitrides of the nuclear fuel uranium and plutonium alone or in a mixture with zircon from the corresponding fluorides, characterized in that the fluorine compounds or the corresponding amnionium double fluorides by high-temperature ammonolysis to form higher nitrides (metal-nitrogen ratio 1.7 his 1.9) and these are broken down in vacuo to form the corresponding mononitrides. 2. The method according to claim 1, characterized in that the higher-value fluorides of the nuclear fuel first reduced to lower-value fluorides (tetrafluorides and trifluorides) and these are then reacted with ammonia. 3. The method according to claim 1, characterized in that ammonium pentafluorouranate IV, which is obtained by direct reaction of uranium hexafluoride with ammonia, is converted directly at a higher temperature with ammonia to form uranium nitride. Ί. The method of claim 1-3 "characterized in that the Tlochtemperaturammonolyse the tetrafluoride and Ammoniuradoppelfluoride between 850 and 96O ° C, but preferably" wipe 890 and 920 ⁰ C ₁ is carried out. 5. The method of claim 1-3, characterized in that the Ilochtemperaturammonolyse the trifluorides at temperatures from 750 to 1050 ° 0, it is preferably, however, 850-1 ⁰ 00o C is performed. - 6 109830/1474 6. The method according to claim 1, 3 and 5, characterized in that the tetrafluorides are initially reduced with hydrogen to trifluorides in one operation and these are then subjected to the Tlochtemperaturammonolysis iver the. 7. The method according to claim 1-5, characterized in that the ilicht temperature ammonolysis is carried out at higher pressures, but preferably at atmospheric pressure. Frankfurt / Main, August 7th, 1967
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