阅读说明：本技术 弥散分布有二氧化铀芯球的钨或钼基燃料芯块的制备方法 (Preparation method of tungsten or molybdenum-based fuel pellet with uranium dioxide core balls dispersed and distributed ) 是由 张临超 景柯 刘瑞 谢卓明 李刚 何琨 王先平 方前锋 吴学邦 刘长松 于 2020-04-17 设计创作，主要内容包括：本发明公开一种弥散分布有二氧化铀芯球的钨或钼基燃料芯块的制备方法,包括将二氧化铀微球与粘结剂溶于可挥发性溶剂中的溶液进行预混,烘干后得到表面均匀附着有粘结剂的二氧化铀芯球；再将该二氧化铀芯球、钨或钼基金属粉体和/或粘结剂混合,模压成型后得到芯块坯体；将该芯块坯体在保护性气体或真空条件下进行烧结,得到所述弥散分布有二氧化铀芯球的钨或钼基燃料芯块。本发明通过特定混合工艺,实现了大粒度的二氧化铀芯球在钨或钼基金属基体中的均匀分散。(The invention discloses a preparation method of tungsten or molybdenum-based fuel pellets with uranium dioxide core spheres dispersed and distributed, which comprises the steps of premixing uranium dioxide microspheres and a solution of a binder dissolved in a volatile solvent, and drying to obtain the uranium dioxide core spheres with the surface uniformly adhered with the binder; mixing the uranium dioxide core ball, tungsten or molybdenum-based metal powder and/or a binder, and performing compression molding to obtain a pellet blank; sintering the pellet blank under the protective gas or vacuum condition to obtain the tungsten or molybdenum-based fuel pellet with the uranium dioxide core balls dispersed and distributed. The invention realizes the uniform dispersion of the uranium dioxide core ball with large particle size in the tungsten or molybdenum-based metal matrix through a specific mixing process.)

1. A method for preparing tungsten or molybdenum-based fuel pellets with uranium dioxide core balls dispersed and distributed is characterized by comprising the following steps:

s1, premixing the uranium dioxide microspheres and a solution of a binder dissolved in a volatile solvent, and drying to obtain uranium dioxide core spheres with the surface uniformly adhered with the binder;

s2, mixing the uranium dioxide core ball with the surface evenly adhered with the binder, the tungsten or molybdenum-based metal powder and/or the binder obtained in the step S1, and obtaining a pellet blank after compression molding;

and S3, sintering the pellet blank obtained in the step S2 under the protective gas or vacuum condition to obtain the tungsten or molybdenum-based fuel pellets with the uranium dioxide core balls dispersed and distributed.

2. The method for preparing the tungsten or molybdenum-based fuel pellet with the uranium dioxide core spheres dispersed and distributed in the claim 1, wherein the particle size range of the uranium dioxide microspheres is 100-1000 microns, preferably 100-400 microns;

further, the volume of the uranium dioxide core sphere in the tungsten or molybdenum based fuel pellet is 30-80%, preferably 40-70%.

3. The method for preparing tungsten or molybdenum-based fuel pellets with uranium dioxide core spheres dispersed and distributed thereon according to claim 1 or 2, wherein the binder is one or a combination of liquid paraffin, solid paraffin, polytetrafluoroethylene, polyvinylidene fluoride, sodium dodecylbenzene sulfonate, sodium carboxymethylcellulose and polyolefin.

4. A method for producing pellets of tungsten or molybdenum based fuel with uranium dioxide core spheres dispersed and distributed thereon according to any one of claims 1 to 3, wherein the total amount of the binder is 0.1 to 10 wt% of the mass of the pellets of tungsten or molybdenum based fuel, and the volume ratio of the uranium dioxide microspheres to the tungsten or molybdenum based metal powder is 2/3 to 4/1.

5. A method for the preparation of fuel pellets of tungsten or molybdenum base with uranium dioxide core spheres dispersed and distributed in it, according to any of claims 1 to 4, characterized in that the volatile solvent is one or a combination of water, alcohols, ethers, amides, acids, ketones, polyolefinic solvents.

6. Method for the preparation of tungsten or molybdenum based fuel pellets with uranium dioxide core spheres dispersed and distributed thereon according to any of claims 1 to 5, characterized in that step S1 specifically comprises: dissolving the binder in a volatile solvent to obtain a binder solution, soaking the uranium dioxide microspheres in the binder solution, and drying to remove the volatile solvent to obtain the uranium dioxide core spheres with the binder uniformly adhered on the surfaces.

7. Method for the preparation of tungsten or molybdenum based fuel pellets with uranium dioxide core spheres dispersed and distributed thereon according to any of claims 1 to 6, characterised in that step S2 comprises in particular: and (4) uniformly mixing the uranium dioxide core ball with the surface uniformly adhered with the binder, the tungsten or molybdenum metal powder and/or the binder obtained in the step (S1), and pressing the mixture in a die to form a blank body, thus obtaining the pellet blank body.

8. The method for producing pellets of tungsten or molybdenum based fuel with uranium dioxide core spheres dispersed and distributed thereon according to any of claims 1 to 7, wherein in step S3, the sintering temperature is 1600-2400 ℃, and the sintering time is 0.5-20 h;

furthermore, the sintering mode is spark plasma sintering, hot isostatic pressing sintering, hot pressing sintering or pressureless sintering.

9. A method for producing tungsten or molybdenum based fuel pellets with uranium dioxide core spheres dispersed and distributed thereon according to any of claims 1 to 8, wherein in step S3, the protective gas is one or more of hydrogen, argon and nitrogen.

10. A tungsten or molybdenum-based fuel pellet having uranium dioxide core spheres dispersed therein, characterized in that it is produced by the production method according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of nuclear fuel, in particular to a preparation method of tungsten or molybdenum-based fuel pellets with uranium dioxide core balls dispersed and distributed.

Background

The nuclear propulsion system is the optimal or even the only choice for deep space exploration and manned aviation in the future, along with the gradual successful implementation of the China's state manned aviation, ' Chang ' moon exploration plan and Mars plan, the China is in the key period of the high-speed development of the aerospace industry, and more remote deep space exploration and manned landing on other stars are bound to become the next development focus of the aerospace development in China, so the research and development of related key components of the nuclear propulsion system are not slow. As a key component of a space fission reactor in a nuclear propulsion system, fuel pellets are the key for improving the nuclear propulsion performance and are one of the most difficult components to develop, and the nuclear fuel pellet design of a high-performance reactor core is very important. In the aspect of fuel selection, through comparative analysis of the technical route in earlier stages of the two countries of the United states and Russia (Su), the tungsten or molybdenum-based metal ceramic adopting uranium dioxide as fuel has good inclusion performance on fission products, higher relative strength and relatively better compatibility with hydrogen working media, provides favorable conditions for long-time work and repeated starting of the fuel, and has unique advantages and application prospects.

Different from nuclear fuel pellets for ground large-scale nuclear power stations, the nuclear fuel pellets are limited by the mass and the volume of a space aircraft, and the problem to be solved in the design of a space nuclear reactor is that the effective substance proportion of the fuel pellets is improved as much as possible, so that certain requirements are put forward on the structure and the volume proportion of uranium dioxide in the fuel pellets, and the uranium dioxide fuel usually selects microspheric particles to replace irregular powder fuel so as to improve the fuel utilization rate and the irradiation performance and reduce irradiation swelling. And secondly, considering the heat conduction problem, the working temperature is higher and the effective temperature control can be carried out only through the flowing of the hydrogen working medium, so that the heat conduction performance and the heat stability of the fuel pellet are also higher. The ideal distribution of the fuel avoids thermal stress deformation and thermal decomposition due to local overheating, and therefore the uniformity of distribution of the uranium dioxide within the metal matrix is a central factor in determining the performance of the fuel pellet. As the difference between the large-particle-size uranium dioxide microspheres in the raw materials and the tungsten or molybdenum-based metal nano powder is large in particle size, density, shape, toughness and the like, the uniform mixing is difficult. The premise is that the addition of the binder is very important, and the influence of the type and the addition mode on the structure of a final product is very critical. According to the literature reports, the used binders include polyethylene (Journal of nuclear Materials 4862017246-. Therefore, how to realize the uniform mixing of the binder, the uranium dioxide microspheres and the tungsten or molybdenum-based metal powder under the premise of less addition amount is an important factor influencing the performance of the fuel pellet.

Disclosure of Invention

Based on the technical problems in the background art, the invention provides a preparation method of a tungsten or molybdenum-based fuel pellet with uranium dioxide core spheres dispersed and distributed, which realizes the uniform dispersion of the large-particle-size uranium dioxide core spheres in a tungsten or molybdenum-based metal matrix through a specific mixing process.

The invention provides a preparation method of tungsten or molybdenum-based fuel pellets with uranium dioxide core balls dispersed and distributed, which comprises the following steps:

s1, premixing the uranium dioxide microspheres and a solution of a binder dissolved in a volatile solvent, and drying to obtain uranium dioxide core spheres with the surface uniformly adhered with the binder;

s2, mixing the uranium dioxide core ball with the surface evenly adhered with the binder, the tungsten or molybdenum metal powder and/or the binder obtained in the step S1, and obtaining a pellet blank after compression molding;

and S3, sintering the pellet blank obtained in the step S2 under the protective gas or vacuum condition to obtain the tungsten or molybdenum-based fuel pellets with the uranium dioxide core balls dispersed and distributed.

Preferably, the particle size range of the uranium dioxide microspheres is 100-1000 microns, preferably 100-400 microns;

further, the volume of the uranium dioxide core sphere in the tungsten or molybdenum based fuel pellet is 30-80%, preferably 40-70%.

Preferably, the binder is one or a combination of more of liquid paraffin, solid paraffin, polytetrafluoroethylene, polyvinylidene fluoride, sodium dodecyl benzene sulfonate, sodium carboxymethylcellulose and polyolefin.

Preferably, the total dosage of the adhesive is 0.1-10 wt% of the mass of the tungsten or molybdenum-based fuel pellet, and the volume ratio of the uranium dioxide microspheres to the tungsten or molybdenum-based metal powder is 2/3-4/1.

Preferably, the volatile solvent is one or a combination of water, alcohols, ethers, amides, acids, ketones and polyolefin solvents.

Preferably, step S1 specifically includes: dissolving the binder in a volatile solvent to obtain a binder solution, soaking the uranium dioxide microspheres in the binder solution, and drying to remove the volatile solvent to obtain the uranium dioxide core spheres with the binder uniformly adhered on the surfaces.

Preferably, step S2 specifically includes: and (4) uniformly mixing the uranium dioxide core ball with the surface uniformly adhered with the binder, the tungsten or molybdenum metal powder and/or the binder obtained in the step (S1), and pressing the mixture in a die to form a blank body, thus obtaining the pellet blank body.

Preferably, in step S3, the sintering temperature is 1600 ℃ to 2400 ℃, and the sintering time is 0.5 to 20 hours; furthermore, the sintering mode is spark plasma sintering, hot isostatic pressing sintering, hot pressing sintering or pressureless sintering.

Preferably, in step S3, the protective gas is one or more of dry flowing hydrogen, argon, and nitrogen.

The invention also provides a tungsten or molybdenum-based fuel pellet with the uranium dioxide core balls dispersed and distributed, which is prepared by the preparation method.

Compared with the prior art, the preparation method of the tungsten or molybdenum-based fuel pellet with the uranium dioxide core spheres dispersed and distributed adopts a segmented mixing technology in the raw material mixing process, namely, uranium dioxide microspheres, a binder and tungsten or molybdenum-based metal powder are sequentially mixed according to different steps, so that the high uniform mixing degree of the large-particle-size uranium dioxide core spheres and the tungsten or molybdenum-based metal nano powder can be obtained on the premise of less binder consumption.

Drawings

FIG. 1 is a flow chart of a production process in example 1 of the present invention;

FIG. 2 is a scanning electron micrograph of the mixed powder in example 1 of the present invention;

FIG. 3 is a metallographic micrograph of tungsten-based fuel pellets according to example 1 of the present invention;

FIG. 4 is a scanning electron micrograph of the mixed powder in example 2 of the present invention;

FIG. 5 is a scanning electron micrograph of the mixed powder of comparative example 1 of the present invention;

FIG. 6 is a metallographic micrograph of a tungsten-based fuel pellet according to comparative example 2 of the present invention.

Detailed Description

The technical solution of the present invention will be described in detail below with reference to specific examples.