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Uranium carbide pellets, preparation method thereof, and fuel rod

A technology of uranium carbide and pellets, applied in the field of nuclear reactors, can solve the problems of high energy consumption, inapplicability to industrialized mass production, and reduced safety, and achieve the effect of low energy consumption and batch sintering

Active Publication Date: 2019-09-10
CHINA NUCLEAR POWER TECH RES INST CO LTD +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] 2. When adding sintering aids to sinter uranium carbide pellets, although it is beneficial to densification, it will significantly reduce the melting point of the pellets and reduce the safety
However, this method can only sinter one pellet per furnace, which has extremely low efficiency, high energy consumption, and high equipment requirements, and is not suitable for industrial mass production.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

preparation example Construction

[0031] The preparation method of uranium carbide pellet of the present invention comprises the following steps:

[0032] S1. Weigh the uranium nitride powder and carbon source according to the molar ratio of 1:0.8-1.5, add them to the solvent, and mix them uniformly to form a slurry.

[0033] Among them, the purity of the uranium nitride (UN) powder is greater than 95%, and the particle size is 0.1-50 μm. The carbon source (C) is carbon black and / or graphite, the purity is greater than 95%, and the particle size is 0.1-50 μm.

[0034] The solvent can be ethanol or acetone. The uranium nitride powder and the carbon source are added to the solvent in order to make the two fully mixed and evenly distributed.

[0035] S2, drying the slurry to obtain a mixed powder.

[0036] The resulting slurry can be dried by rotary evaporation to obtain a dry mixed powder. The evaporation and drying time is adjusted according to the actual situation.

[0037] S3, pressing the mixed powder i...

Embodiment 1

[0057] Prepare uranium carbide pellets with a density of 98%, and weigh according to the molar ratio of UN:C of 1:1.2: 249 grams of UN powder and 14.4 grams of carbon black.

[0058] Using ethanol as a solvent, at a speed of 120 rpm, with Si 3 N 4After ball-roller mixing for 24 hours, the resulting slurry was dried by rotary evaporation to obtain a uniformly mixed powder. Put the mixed powder into the pellet steel mold, first apply a pressure of 10MPa for pre-compression, then vacuum-seal the preformed green body with oil paper, and then use a cold isostatic press to apply 200MPa pressure to the oil-paper vacuum-sealed green body. Equal pressure load, hold pressure at 200MPa for 5 minutes, so that the initial density of the pellet green body reaches more than 50%.

[0059] Take out the green body and put it into a high-temperature pressureless furnace for reaction sintering. Using pressureless sintering, in the first reaction stage, the heating rate is 10°C / min, the tempera...

Embodiment 2

[0062] Prepare uranium carbide pellets with a density of 95%. The carbon source is replaced by graphite from the carbon black in Example 1. Weigh according to the molar ratio of UN:C of 1:0.8: 249 grams of UN powder and 9.6 grams of graphite.

[0063] The green body was prepared according to the same method as in Example 1, the in-situ reaction temperature was 1500° C. for 2 hours, and the sintering temperature was 1900° C. for 1 hour.

[0064] According to X-ray diffraction analysis, the phase of the sintered pellet is uranium carbide, and the diffraction peak shifts slightly to the left, indicating that nitrogen solid solution exists. It is found through testing that the uranium carbide pellets prepared after heat preservation and sintering at 1900°C for 1 hour have a density of 95%, a porosity of 5%, a pore diameter of 500nm, and open pores.

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Abstract

The invention discloses a uranium carbide pellet, a preparation method thereof and a fuel rod. The preparation method of uranium carbide pellets comprises the following steps: S1, weighing uranium nitride powder and a carbon source according to a molar ratio of 1:0.8-1.5 and adding them to a solvent, and mixing them uniformly to form a slurry; S2, mixing the Drying the slurry to obtain a mixed powder; S3, pressing the mixed powder into a green body with a density of 50% or more; S4, high-temperature pressureless sintering to obtain a uranium carbide pellet with a density ≥ 95%. In the present invention, uranium nitride and carbon source are used as raw materials to realize two processes of carbothermal reduction reaction and densification sintering under high-temperature pressureless sintering, without using hot-press sintering process with low production efficiency, and without introducing sintering aids. It avoids the problem of lowering the melting point of pellets, can realize batch sintering, has low energy consumption, and is suitable for industrial production of fuel pellets.

Description

technical field [0001] The invention relates to the technical field of nuclear reactors, in particular to a uranium carbide pellet, a preparation method thereof, and a fuel rod. Background technique [0002] Existing commercial pressurized water reactor nuclear fuel is mainly uranium dioxide (UO 2 ) pellets, but UO 2 The thermal conductivity of the pellets is low, and the temperature of the centerline is high. Even if the reactor has been shut down safely in the event of an accident, a large amount of decay heat is still stored in the pellets. When the coolant is lost, it is difficult to export the residual heat, so that the temperature of the fuel rod cladding rises rapidly. to dangerous levels. Due to the chemical properties of the existing zirconium alloy materials, an obvious zirconium-water reaction begins to occur above 650°C. This reaction is an exothermic reaction and releases a large amount of hydrogen gas, which seriously deteriorates the safety of fuel assemblie...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G21C3/62C04B35/56
CPCG21C3/62C04B35/56C04B2235/425C04B2235/424C04B2235/3852C04B2235/608C04B2235/77C04B2235/96Y02E30/30C04B35/5158C04B2235/6562C04B2235/6567C04B2235/5445C04B2235/5436C04B2235/6581C04B2235/661
Inventor 薛佳祥张显生刘彤李锐严岩李思功黄华伟龚星任啟森严俊卢志威
Owner CHINA NUCLEAR POWER TECH RES INST CO LTD
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