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Preparation method of UN pellet for light water reactor

A light water reactor and pellet technology, which is applied in the field of preparation of UN pellets for light water reactors, can solve the problems of low sintering performance, low activity, and difficulty in obtaining dense pellets.

Pending Publication Date: 2021-06-22
CHINA NUCLEAR BAOTOU GUANGHUA CHEM IND
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] At present, there are two major technical problems in the UN pellets prepared by pressureless and pressure sintering: First, the current UN powder is basically prepared by the carbothermal reduction process, and the obtained powder contains a large amount of C and O, and it needs to be decarburized , Deoxidation and other processes for further purification operations, even so, it is difficult to control the O content in the powder below 2000ppm
In addition, the UN powder obtained by the above process has a large particle size and low activity, and its sintering performance is greatly reduced
Second, due to the low diffusion coefficient of UN molecules, poor sintering activity, and the problem that the sintering temperature is limited by the decomposition temperature, it is difficult to obtain pellets with a density higher than 85%.

Method used

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  • Preparation method of UN pellet for light water reactor
  • Preparation method of UN pellet for light water reactor

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preparation example Construction

[0015] The preparation method of UN pellet for light water reactor of the present invention is as follows:

[0016] Using cast uranium ingots as raw materials, through 2-5 cycles of hydrogenation-dehydrogenation process, the metal uranium powder with powder D90x N y , 0.6<x / y<1). In order to prevent the oxidation of high-nitrogen-uranium ratio compound powder, the high-nitrogen-uranium ratio compound powder is pre-pressed in a graphite mold, and heated together with the mold to 1300-1500°C in a tungsten-molybdenum sintering furnace for high-temperature denitrification and decomposition, and then after ball milling Obtain pure fine UN powder. Place the obtained UN powder in a graphite mold, and sinter at 1500-1600° C. for more than 2 hours in a hot-press sintering furnace under a pressure of 20-50 MPa to obtain dense UN fuel pellets.

Embodiment 1

[0018] A kind of preparation method of UN pellet for light water reactor of the present invention, it comprises the steps:

[0019] Step 1: Soak the Φ30×3mm metal uranium piece in nitric acid to remove the oxide film on the surface of the uranium piece, and then wash with absolute ethanol to remove the residual acid solution on the surface of the uranium block. The metal uranium pieces are then placed in a container filled with absolute ethanol;

[0020] Step 2: Transfer the container soaked with metal uranium slices to a hydrodehydrogenation furnace, take out the metal uranium slices soaked in absolute ethanol in the hydrogenation dehydrogenation furnace, and then carry out hydrogenation reaction: heat metal uranium in a hydrogen atmosphere sheet, making it undergo hydrogen absorption reaction to generate UH x Powder, hydrogenation temperature 250°C, hydrogenation time 4h;

[0021] Step 3: Heat the hydrogenated UHx powder to 480°C in a vacuum atmosphere and keep it warm for...

Embodiment 2

[0028] A kind of preparation method of UN pellet for light water reactor of the present invention, it comprises the steps:

[0029] Step 1: Soak the Φ30×3mm metal uranium piece in nitric acid to remove the oxide film on the surface of the uranium piece, and then wash with absolute ethanol to remove the residual acid solution on the surface of the uranium block. The metal uranium pieces are then placed in a container filled with absolute ethanol;

[0030] Step 2: Transfer the container soaked with metal uranium slices to a hydrodehydrogenation furnace, take out the metal uranium slices soaked in absolute ethanol in the hydrogenation dehydrogenation furnace, and then carry out hydrogenation reaction: heat metal uranium in a hydrogen atmosphere sheet, making it undergo hydrogen absorption reaction to generate UH x Powder, hydrogenation temperature 270°C, hydrogenation time 4h;

[0031] Step 3: Heat the hydrogenated UHx powder to 480°C in a vacuum atmosphere and keep it warm for...

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Abstract

The invention belongs to the technical field of nuclear fuel core material manufacturing, and particularly relates to a preparation method of a UN pellet for a light water reactor. The preparation method comprises the steps of taking an as-cast uranium ingot as a raw material, preparing metal uranium powder through a cyclic hydrogenation-dehydrogenation technology, and then obtaining high-nitrogen-uranium-ratio compound powder through nitridation; putting the high-nitrogen-uranium-ratio compound powder into a graphite mold for pre-pressing, carrying out high-temperature denitrification decomposition on the compound powder and the mold in a tungsten-molybdenum sintering furnace, and carrying out ball milling to obtain pure fine UN powder; and placing the obtained UN powder in a graphite mold, and obtaining the compact UN fuel pellet in a hot-pressing sintering furnace. According to the invention, the high-activity UN powder with high purity and small particle size is obtained through the procedures of hydrogenation, dehydrogenation, nitridation and denitrification, compared with a carbon thermal reduction method, the powder purity is greatly improved, and then the fuel pellet with the density being 90% or above is obtained through the optimized hot pressing sintering process.

Description

technical field [0001] The invention belongs to the technical field of manufacturing nuclear fuel core materials, and in particular relates to a preparation method of UN pellets for light water reactors. Background technique [0002] The density of uranium in UN is 13.55gU / cm 3 , significantly higher than UO 2 (9.66gU / cm 3 ). The thermal conductivity of UN is at least higher than that of UO 2 5 times higher and similar melting point (~2850°C). UN fuel has many advantages such as high thermal conductivity, high uranium density, high melting point, high temperature stability, hard neutron spectrum, low thermal expansion coefficient, good radiation stability, low fission gas release rate, and good compatibility with liquid metals. With excellent performance, it has become an important candidate fuel for the fourth generation nuclear energy system in the future. [0003] At present, there are two major technical problems in the UN pellets prepared by pressureless and press...

Claims

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Application Information

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IPC IPC(8): G21C21/16G21C21/10
CPCG21C21/16G21C21/10Y02E30/30
Inventor 何勇李宗书乔伟孙祎强郝若彤隋政杜江平梁方知
Owner CHINA NUCLEAR BAOTOU GUANGHUA CHEM IND