Composite material for spent fuel storage and preparation method thereof
阅读说明：本技术 一种乏燃料贮存用复合材料及其制备方法 (Composite material for spent fuel storage and preparation method thereof ) 是由 李丘林 刘伟 王靓 汪佳 于 2020-06-17 设计创作，主要内容包括：本发明公开了一种乏燃料贮存用复合材料及其制备方法,该乏燃料贮存用复合材料包括以下重量百分数计的制备原料：0.5～3％的碳纳米管、5～45％的TiB<Sub>2</Sub>粉和52～94.5％的铝粉；其制备方法包括：将占碳纳米管总质量80～100％的碳纳米管与TiB<Sub>2</Sub>粉混合均匀,制得混料一；将剩余的碳纳米管和铝粉混合均匀,制得混料二；将混料一和混料二混合均匀后,进行冷等静压,制成坯料；再将坯料烧结,而后进行轧制。通过以上方法制得的乏燃料贮存用复合材料具有优异的耐高温性能、导热性能和力学性能。(The invention discloses a composite material for spent fuel storage and a preparation method thereof, wherein the composite material for spent fuel storage comprises the following preparation raw materials in percentage by weight: 0.5-3% of carbon nano tube and 5-45% of TiB 2 Powder and 52-94.5% of aluminum powder; the preparation method comprises the following steps: mixing the carbon nanotubes and TiB accounting for 80-100% of the total mass of the carbon nanotubes 2 Uniformly mixing the powder to obtain a first mixed material; uniformly mixing the rest carbon nano tubes and aluminum powder to prepare a mixed material II; will be provided withAfter uniformly mixing the first mixed material and the second mixed material, carrying out cold isostatic pressing to prepare a blank; and sintering the blank, and then rolling. The composite material for spent fuel storage prepared by the method has excellent high temperature resistance, heat conductivity and mechanical property.)
1. The preparation method of the composite material for spent fuel storage is characterized in that the composite material for spent fuel storage comprises the following preparation raw materials in percentage by weight: 0.5-3% of carbon nano tube and 5-45% of TiB2Powder and 52-94.5% of aluminum powder; the preparation method of the composite material for spent fuel storage comprises the following steps:
s1, mixing the carbon nano-tube and TiB which account for 80-100% of the total mass of the carbon nano-tube2Uniformly mixing the powder to obtain a first mixed material;
s2, uniformly mixing the residual carbon nano tubes and aluminum powder to obtain a mixed material II;
s3, uniformly mixing the first mixed material and the second mixed material to obtain a mixed material;
s4, carrying out cold isostatic pressing on the mixture to prepare a blank;
s5, sintering the blank, and then rolling;
wherein, the sequence of the step S1 and the step S2 is not sequential.
2. The method for preparing the spent fuel storage composite material according to claim 1, wherein in the steps S1 and S2, the mixing is performed by wet ball milling;
in step S3, the first mixed material and the second mixed material are uniformly mixed and then dried to obtain a mixed material; or, drying the first mixed material and the second mixed material respectively and then uniformly mixing to obtain a mixed material.
3. The preparation method of the spent fuel storage composite material according to claim 2, wherein the wet ball milling mixing is performed by using alcohol as a mixing medium, and the ball-to-feed ratio is (6-10): 1.
4. the preparation method of the spent fuel storage composite material according to claim 3, wherein the rotation speed of the wet ball milling mixing is 100-250 r/min, and the mixing time is 1-3 h.
5. The method for preparing the spent fuel storage composite material according to claim 1, wherein in step S4, the cold isostatic pressing pressure is 350-450 MPa, and the dwell time is 1-3 min.
6. The method for preparing the spent fuel storage composite material according to any one of claims 1 to 5, wherein in step S5, the sintering temperature of the sintering is 400-550 ℃, the vacuum degree is controlled to be less than 100Pa, and the sintering time is 2-5 h.
7. The method for preparing the spent fuel storage composite material according to claim 6, wherein in step S5, the rolling temperature is 450-600 ℃, and the rolling reduction is 20-90%.
8. The method for preparing the spent fuel storage composite according to claim 7, wherein the rolling comprises: preserving heat for 2-4 h at 450-600 ℃, and then performing primary rolling with the rolling reduction of 20-25%; then preserving heat for 30min, and then performing second rolling, wherein the reduction is 12-20%; and repeating the second rolling until the total rolling reduction reaches 50-90%.
9. The method for preparing the spent fuel storage composite according to claim 7, wherein the step S5 further comprises an annealing treatment after the rolling.
10. A spent fuel storage composite material, characterized by being prepared by the method for preparing the spent fuel storage composite material according to any one of claims 1 to 9.
Technical Field
The invention relates to the technical field of material preparation, in particular to a composite material for spent fuel storage and a preparation method thereof.
Background
As a clean and efficient new energy, nuclear power is widely concerned and paid attention to and is correspondingly rapidly developed. With the rapid development of nuclear power industry, the amount of spent fuel discharged from nuclear reactors is also rapidly increased. Spent fuel, a nuclear fuel that has been irradiated by radiation, is still radioactive, and therefore requires protection from materials that have the ability to absorb thermal neutrons during storage of the spent fuel.
Abundant boron (B) reserves, among them10The B neutron has high absorption cross section (3837barn) and high abundance, so the B neutron is widely used in materials for storing spent fuel. At present, the materials for storing the spent fuel mainly comprise boron-containing stainless steel, boron-aluminum alloy and B4C/Al composite material.
The boron-containing stainless steel is a neutron absorption material with a certain amount of B element added into austenitic steel, and has good irradiation resistance, but because the solubility of B in the stainless steel is very low, the content of B in the product is difficult to be added to more than 2.25%, the material is generally made very thick, so that the storage capacity of the material is obviously reduced compared with that of the similar material, the brittleness of boron steel is obviously increased along with the increase of boron content, and the continuously deteriorated mechanical property is not beneficial to the long-term storage of spent fuel.
Boron-aluminum alloy is a material similar to boron stainless steel, and because the solubility of B element in the aluminum alloy is low, the thickness of the boron-aluminum alloy material is often larger; and which are generally concentrated10B is prepared, and the concentration technology of B is expensive, so the material is less applied.
B4The C/Al composite material is a neutron absorption material for spent fuel storage which is currently mainstream internationally. B is4The C has high modulus and hardness, high melting point and small thermal expansion coefficient, is widely used for a reinforcing phase of a neutron absorption composite material, and is widely applied nearly half a century. Preparation of B by liquid Process by Alcan, Canada4The C/Al composite material has good heat-conducting property and better mechanical property, but because of B4The wettability of C and liquid Al is poor,products of this company B4The C content is always below 25 wt.%, and the neutron absorption properties are insufficient.
In addition, in the service process of the spent fuel dry-method storage material, the material is continuously absorbed by thermal neutrons so as to be in a high-temperature (350 ℃) environment for a long time, and researches show that B4C and Al can generate a fast chemical reaction at 660 ℃ and a slow reaction below 660 ℃, so that Al can be generated when the material is in a long-term high-temperature environment or in an accident3BC and the like, which cause the mechanical property of the material to be reduced, namely B4The C/Al composite material has certain safety risk when being used as a neutron absorption material at high temperature. And, conventional high temperature use B4The C/Al composite material usually adopts submicron-grade superfine aluminum powder as a matrix, an aluminum oxide film is easily formed on the surface of the aluminum powder, the aluminum oxide film on the surface is favorable for improving the high-temperature mechanical property of the material, but is also used as a barrier layer with poor thermal conductivity, the thermal conductivity of the material is deteriorated, the heat generated by thermal neutrons absorbed by the material is difficult to dissipate under the service condition of spent fuel dry storage, and thus, the whole storage system is easy to cause accidents due to high temperature and deteriorated strength. Therefore, a neutron absorbing material for the spent fuel dry storage, which has high temperature resistance, high mechanical property and thermal conductivity, is urgently needed.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a composite material for spent fuel storage and a preparation method thereof.
The technical scheme adopted by the invention is as follows:
the invention provides a preparation method of a composite material for spent fuel storage, which comprises the following preparation raw materials in percentage by weight: 0.5-3% of carbon nano tube and 5-45% of TiB2Powder and 52-94.5% of aluminum powder; the preparation method of the composite material for spent fuel storage comprises the following steps:
s1, mixing the carbon nano-tube and TiB which account for 80-100% of the total mass of the carbon nano-tube2Uniformly mixing the powder to obtain a first mixed material;
s2, uniformly mixing the residual carbon nano tubes and aluminum powder to obtain a mixed material II;
s3, uniformly mixing the first mixed material and the second mixed material to obtain a mixed material;
s4, carrying out cold isostatic pressing on the mixture to prepare a blank;
s5, sintering the blank, and then rolling;
wherein, the sequence of the step S1 and the step S2 is not sequential.
In the steps S1 and S2, the purity of the carbon nanotubes is generally more than 99.5%, the diameter is 20-60 nm, and the length is 5-30 μm. In step S1, TiB2The purity of the powder is more than 95%, and the particle size is 1-100 mu m; in step S2, aluminum powder with a purity of more than 99% is generally used, and the particle size of the aluminum powder is generally 0.1-100 μm. Preferably, the composite material for spent fuel storage comprises the following preparation raw materials in percentage by weight: 1-2% of carbon nano tube and 20-25% of TiB2Powder and 73-78% of aluminum powder.
According to some embodiments of the invention, the mixing in steps S1 and S2 is wet ball milling;
in step S3, the first mixed material and the second mixed material are uniformly mixed and then dried to obtain a mixed material; or, drying the first mixed material and the second mixed material respectively and then uniformly mixing to obtain a mixed material.
According to some embodiments of the invention, the wet ball milling mixing uses alcohol as a mixing medium, and the ball-to-material ratio is (6-10): 1.
according to some embodiments of the invention, the rotation speed of the wet ball milling mixing is 100-250 r/min, and the mixing time is 1-3 h. The ball milling and mixing process has no atmosphere protection, and cooling water with the temperature of 10-20 ℃ can be introduced for cooling. In addition, the mixing can be carried out by a conventional V-type mixer or a dry-type stirrer.
According to some embodiments of the invention, in step S4, the cold isostatic pressing pressure is 350-450 MPa, and the dwell time is 1-3 min.
According to some embodiments of the invention, in step S5, the sintering temperature of the sintering is 400-550 ℃, the vacuum degree is controlled below 100Pa, and the sintering time is 2-5 h. The specific controllable sintering temperature rise process is as follows: heating to 120 ℃ and preserving heat for 30min, then heating to 350 ℃ and preserving heat for 30min, and finally heating to 400-550 ℃.
According to some embodiments of the invention, in the step S5, the rolling temperature is 450-600 ℃, and the rolling reduction is 20-90%; the preferable reduction amount is 50-90%. The rolling is carried out for multiple times at 450-600 ℃, and specifically, the temperature is kept at 450-600 ℃ for 2-4 h, and the rolling reduction for the first time is 20-25%; then preserving heat for 30min, and then performing second rolling, wherein the reduction is 12-20%; the second rolling pass can be repeated for a plurality of times until the total rolling reduction reaches 50-90%.
According to some embodiments of the invention, the step S5 further includes an annealing process after the rolling. The annealing temperature is generally 150-200 ℃ and the annealing time is 2-5 h.
In a second aspect of the present invention, a composite material for spent fuel storage is provided, which is prepared by any one of the methods for preparing a composite material for spent fuel storage provided by the first aspect of the present invention.
The embodiment of the invention has the beneficial effects that:
the embodiment of the invention provides a preparation method of a composite material for spent fuel storage, wherein TiB is used2As reinforcing phase, by adding appropriate TiB2Sufficient neutron absorption capacity can be achieved and due to TiB2Does not react with aluminum, so the high-temperature service process is more stable, and the safety factor of extreme conditions such as accident conditions and the like is improved. In addition, proper carbon nano tubes are added, and step-by-step mixing is adopted in the preparation process, so that the carbon nano tubes are coated with TiB (titanium dioxide) with low thermal conductivity in the matrix2And a network is formed in the subsequent powder mixing and rolling processes, which is helpful for the directional heat transfer and can improve the heat conductivity coefficient of the material (the principle is shown in figure 1); moreover, if a certain amount of carbon nanotubes are uniformly mixed with the aluminum particles, the surface breaking of the aluminum particles in the deformation process can be assisted in the subsequent rolling deformation processAnd crushing to generate more nano-scale aluminum oxide fragments as dislocation pinning phases at high temperature, so that the high-temperature performance of the material is improved, and the mechanism can damage the aluminum oxide layer with low thermal conductivity and provide the thermal conductivity of the material. In conclusion, the composite material for spent fuel storage with high temperature resistance, excellent heat conductivity and excellent mechanical property can be prepared by the preparation method.
Drawings
FIG. 1 is a schematic diagram of the action of the components in the composite material for spent fuel storage according to the present invention;
fig. 2 is a microstructure photograph of the composite for spent fuel storage prepared in example 1.
Detailed Description
The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.