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Preparation method of uranium nitride fuel powder and pellets

A technology for uranium nitride and diuranium trinitride, which is applied in the field of nuclear fuel preparation, can solve problems such as the reduction of cold-pressed forming density, and achieve the effects of easy control, high sintering activity and simple process

Active Publication Date: 2015-07-29
CHINA INSTITUTE OF ATOMIC ENERGY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

With the extension of UN powder ball milling time, the particle size of the powder decreases, which will lead to a decrease in the density of cold pressing, but the sintered density of UN ceramic pellets will increase to about 90% TD

Method used

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  • Preparation method of uranium nitride fuel powder and pellets

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preparation example Construction

[0032] Such as figure 1 Shown, the preparation method of uranium nitride fuel powder and pellet provided by the present invention comprises the following steps:

[0033] (1) Surface purification treatment of pure metal uranium block.

[0034] Polish the pure metal uranium block with sandpaper, remove the surface oxide film with dilute nitric acid, wash with absolute ethanol, and quickly proceed to the next step after drying.

[0035] In the present invention, pure metal uranium is selected as the reaction raw material instead of uranium dioxide, which avoids the oxygen in the raw material remaining in the uranium nitride powder, and because there is no uranium dioxide, there is no need to add carbon to reduce the uranium dioxide Uranium, thus avoiding the introduction of carbon and oxygen impurity elements in uranium nitride powder from the source.

[0036] (2) Cyclic hydrogenation-dehydrogenation method to prepare metal uranium powder.

[0037] The metal uranium powder pre...

Embodiment 1

[0052] Polish the pure uranium metal block with sandpaper, remove the oxide film on the surface with dilute nitric acid, wash with absolute ethanol, and quickly transfer it into a resistance furnace after drying, and vacuumize the furnace.

[0053] Raise the temperature of the furnace to 150°C and fill it with 0.1MPa 99.999% high-purity H 2 Carry out the hydrogenation reaction, the hydrogenation holding time is 16h, after the first hydrogenation is completed, the furnace is evacuated to maintain a vacuum of 5Pa, and the temperature is raised to 600°C for 2h for dehydrogenation, after the dehydrogenation is completed, H 2 , for the second hydrogenation. Hydrogenation-dehydrogenation was cycled 4 times to obtain metal uranium powder. In the process of hydrogenation-dehydrogenation cycle, except that the hydrogenation holding time was reduced from 16h for the first time to 12h, 10h, and 8h, the other parameters remained unchanged.

[0054] After the last dehydrogenation, the met...

Embodiment 2

[0057] The process of preparing metal uranium powder in the present embodiment is identical with embodiment 1, and difference is:

[0058] During cyclic hydrogenation-dehydrogenation, the furnace temperature is raised to 230°C for hydrogenation, and the dehydrogenation is carried out at 490°C and the vacuum degree in the furnace is 50Pa;

[0059] After cyclic hydrogenation-dehydrogenation, metal uranium powder is cooled to 400°C with the furnace, and 0.2MPa99.999% high-purity N is introduced 2 , keep warm for 15h, carry out nitriding reaction;

[0060] Before hot pressing and sintering, denitrify at 1200°C for 1 h, and then maintain a vacuum of 2×10 -2 Pa, under the conditions of 1600°C and mold pressure of 60MPa, hot pressing and sintering were carried out, and the temperature and pressure were kept for 1h, and the obtained UN pellets had a density of 98.9% TD.

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Abstract

The invention relates to a preparation method of uranium nitride fuel powder and a pellet, which comprises the following steps: (1) carrying out surface cleaning treatment on a pure metal uranium lump; (2) hydrogenating the pure metal uranium lump in hydrogen at 150-300 DEG C for 2-16 hours, dehydrogenating in a vacuum, and repeating the hydrogenation-dehydrogenation several times to obtain metal uranium powder; (3) nitridizing the metal uranium powder in nitrogen at 200-600 DEG C for 6-24 hours to obtain U2N3 powder; (4) denitrifying the U2N3 powder in a mold, keeping the system vacuum, pressurizing the mold to 30-60 MPa, sintering at 1450-1620 DEG C for 1-2 hours, and cooling to obtain the UN ceramic pellet. The method provided by the invention is simple in technique and easy to control; and the obtained intermediate product U2N3 powder has higher purity and higher sintering activity, and can be finally subjected to hot pressed sintering to obtain the UN fuel pellet of which the TD is up to 98.9%.

Description

technical field [0001] The invention belongs to the technical field of nuclear fuel preparation, in particular to a method for preparing uranium nitride fuel powder and pellets. Background technique [0002] Uranium nitride fuel has the advantages of high uranium density, high melting point, high thermal conductivity, low thermal expansion coefficient, good radiation stability, low fission gas release rate, and good compatibility with liquid metal coolants. , space nuclear power supply, and the preferred fuel for nuclear rockets. Foreign research and development of uranium nitride fuel for space nuclear power plants has reached the stage of engineering application in the 1990s. Synthesizing uranium nitride powder with high purity, stoichiometric ratio and high sintering activity is one of the key technologies for preparing uranium nitride fuel. [0003] At present, the carbothermal reduction nitriding method of uranium dioxide powder is widely used at home and abroad to pr...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B21/06G21C3/62
CPCY02E30/30
Inventor 尹邦跃屈哲昊
Owner CHINA INSTITUTE OF ATOMIC ENERGY
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