High-purity alumina corundum product for nuclear fuel sintering and preparation method thereof

Abstract

The invention relates to the technical field of nuclear fuel element manufacturing, in particular to a high-purity alumina corundum product for nuclear fuel sintering and a preparation method of the high-purity alumina corundum product. The preparation method comprises the following steps: uniformly mixing fused white corundum, tabular corundum, sintered alpha-Al2O3 micro powder and active Al2O3 micro powder, ageing in a closed container, and re-mixing after ageing is completed; distributing and pressing the mixed powder in a mold to obtain a corundum product green body, and demolding; naturally drying the formed green block at room temperature, heating to 70-90 DEG C for drying, and then heating to 100-120 DEG C for drying; loading the dried green block into a kiln, slowly heating to 290-310 DEG C, and preserving heat; slowly raising the temperature to 590-610 DEG C and keeping the temperature; slowly raising the temperature to 900-1000 DEG C and keeping the temperature; slowly raising the temperature to 1400-1550 DEG C and keeping the temperature; slowly raising the temperature to a firing temperature and keeping the temperature; stopping heating after firing, naturally cooling to 200 DEG C in a closed state, and opening the kiln; and carrying out final finish machining on the sintered corundum product. The prepared high-purity alumina corundum product is good in thermal property and mechanical property and low in cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear fuel element manufacturing, in particular to a high-purity alumina corundum product for nuclear fuel sintering and a preparation method thereof. BACKGROUND

[0002] Sintering is an important process in the production process of nuclear fuel pellets, and the purpose is to sinter the green pellet formed by pressing into a dense ceramic body nuclear fuel pellet with certain strength.

[0003] The service temperature of high-temperature sintering furnace for nuclear industry is as high as 1800℃, and due to the particularity of nuclear industry, there are some clear material ban requirements for materials in the furnace: neutron absorption elements with an absorption cross section greater than 3.5 targets (such as B, Cd, Dy, Eu, Gd, etc.), halogen elements and their compounds, etc. Therefore, some traditional ultra-high temperature refractory materials with excellent high-temperature performance cannot be applied in this field, and Al2O3-based high-temperature corundum refractory furnace bricks are used all over the world.

[0004] Currently, there are three companies in the world involved in this field of refractory materials: French Saint-Gobain, American BTU, and British N-tec Solutions. Their nuclear fuel sintering refractory materials use some conventional processes.

[0005] French Saint-Gobain company has a monopoly position in the industry, and its high-purity corundum refractory materials with AS series and AH series all use high-purity corundum powder and high-purity corundum sand dry pressing forming high-temperature sintering process, but the nuclear fuel refractory furnace bricks produced by Saint-Gobain company have very high requirements for production equipment, mainly reflected in ultra-high pressure forming and 1600℃ high-temperature sintering. Such refractory furnace bricks have the advantages of high service life, high mechanical strength and good thermal performance. However, the cost is high, and it is difficult to prepare large-size special-shaped products, which is not conducive to the realization of complex kiln lining structure.

[0006] The raw materials of nuclear industry refractory furnace bricks of American BTU and British N-tec Solutions are ordered from Saint-Gobain company, which are refractory castables products specially designed for their furnace type by Saint-Gobain company. After traditional wooden mold casting forming, low-temperature drying and 1200℃ sintering process, it is made. Its advantages are that it is easy to manufacture large-size special-shaped refractory furnace bricks, and its disadvantages are that the service life of refractory furnace bricks is poor, the mechanical strength is low, and the thermal performance is poor.

[0007] There are various types of high-purity corundum products in the domestic refractory industry, but there is still a blank in the high-purity Al2O3 corundum refractory products that can simultaneously meet the chemical composition, structural performance, mechanical properties, thermal properties and service performance. SUMMARY

[0008] The technical problem solved by the present application is to provide a high-purity alumina corundum product for nuclear fuel sintering and a preparation method thereof, which has good thermal and mechanical properties and low cost.

[0009] The present application provides a preparation method of a high-purity alumina corundum product for nuclear fuel sintering, comprising the following steps:

[0010] Step S1: uniformly mix 40wt%-50wt% electro-fused white corundum, 30wt-40wt% tabular corundum, 10wt%-20wt% unsaturated polyester resin solution containing sintered α-Al2O3 micropowder, and 200-300PPM active Al2O3 micropowder, and perform material blocking in a closed container, and after the material blocking is completed, perform re-mixing;

[0011] In the unsaturated polyester resin solution containing sintered α-Al2O3 micropowder, the mass percentage of sintered α-Al2O3 micropowder is 4.4wt%-5wt%;

[0012] Step S2: uniformly mix 40wt%-50wt% electro-fused white corundum, 30wt-40wt% tabular corundum, 10wt%-20wt% unsaturated polyester resin solution containing sintered α-Al2O3 micropowder, and 200-300PPM active Al2O3 micropowder, and perform material blocking in a closed container, and after the material blocking is completed, perform re-mixing;

[0013] Step S3: transfer the formed green block to a drying kiln, and dry at room temperature, then heat to 70-90°C for drying, and then heat to 100-120°C for drying;

[0014] Step S4: after the drying of the green block is completed, load the green block into the kiln, and slowly heat to 290-310°C for heat preservation, then slowly heat to 590-610°C for heat preservation, then slowly heat to 900-1000°C for heat preservation, then slowly heat to 1400-1550°C for heat preservation, then slowly heat to the firing temperature for heat preservation, then stop heating after the firing is completed, and naturally cool to 200°C under a closed condition, and then open the kiln;

[0015] Step S5: perform final finishing on the sintered corundum product.

[0016] In a specific embodiment of the present application, in step S1, 40wt%-50wt% electro-fused white corundum, 30wt-40wt% tabular corundum, 10wt%-20wt% unsaturated polyester resin solution containing sintered α-Al2O3 micropowder, and 200-300PPM active Al2O3 micropowder are uniformly mixed in a mixing machine;

[0017] The rotating speed of the mixing machine is 50-300r / min.

[0018] In a specific embodiment of the present application, step S1 is specifically:

[0019] In the mixing machine, 40wt%-50wt% of the electrically fused white corundum is added and mixed for 5-10 minutes to be uniformly mixed;

[0020] 30wt-40wt% of tabular corundum is added and mixed for 5-10 minutes to be uniformly mixed;

[0021] The sintered α-Al2O3 micropowder is added into the unsaturated polyester resin to obtain an unsaturated polyester resin solution containing sintered α-Al2O3 micropowder, the unsaturated polyester resin is an m-benzene type unsaturated polyester resin, the mass percentage of the sintered α-Al2O3 micropowder in the unsaturated polyester resin solution containing sintered α-Al2O3 micropowder is 4.4wt%-5wt%;

[0022] 10wt%-20wt% of the unsaturated polyester resin solution containing sintered α-Al2O3 micropowder is added and mixed for 5-10 minutes to be uniformly mixed;

[0023] The active Al2O3 micropowder is added and mixed for 5-10 minutes to be uniformly mixed;

[0024] The material is stored in a closed container at room temperature for more than 24 hours to complete the material blocking;

[0025] The material after the material blocking is completed is subjected to re-mixing and mixed for 5-10 minutes to complete the mixing process.

[0026] In one specific embodiment of the present application, the natural drying time in step S3 is 10-36 hours.

[0027] In one specific embodiment of the present application, the sintering temperature in step S4 is 1650°C-1800°C.

[0028] In one specific embodiment of the present application, in step S4, the green body block after drying is loaded into a kiln, heated to 300°C for 170-180 minutes, heated to 600°C for 170-180 minutes, heated to 1000°C for 170-180 minutes, heated to 1400-1550°C for 110-130 minutes, and heated to the sintering temperature for 300-400 minutes.

[0029] In one specific embodiment of the present application, in step S4, the green body block after drying is loaded into a kiln, heated to 300°C for 180 minutes, heated to 600°C for 180 minutes, heated to 1000°C for 180 minutes, heated to 1500°C for 120 minutes, and heated to the sintering temperature of 1750°C for 360 minutes.

[0030] In one embodiment of the present application, in step S5, the finishing is performed by using a PDC cutter to CNC machine the fine structure of the final corundum product.

[0031] In one embodiment of the present application, the electrically fused white corundum is high-purity electrically fused white corundum with a particle size ≤5 mm, the tabular corundum has a particle size ≤5 mm, the sintered α-Al2O3 micropowder has a D50 ≤0.045 mm, and the active Al2O3 micropowder has a D50 ≤50 μm.

[0032] The Al2O3 purity of the electrically fused white corundum, the tabular corundum, and the sintered α-Al2O3 micropowder is ≥97%, and the purity of the active Al2O3 micropowder is ≥99.99.

[0033] The present application also provides a high-purity alumina corundum product for nuclear fuel sintering, which is made by the method described above.

[0034] Compared with the prior art, the high-purity alumina corundum product for nuclear fuel sintering and the preparation method thereof can batch-produce the refractory furnace bricks used in the high-temperature continuous sintering furnace for nuclear fuel sintering process. Through experiments, the chemical performance can reach Al2O3 purity ≥99.5%; the structural performance can reach porosity ≤20%, bulk density ≥3.3 g / cm 3 ; the mechanical performance can reach compressive strength 120-150 MPa, cold modulus of rupture ≥25 MPa, and hot modulus of rupture ≥10 MPa. The thermal performance and the use performance can achieve refractoriness >1800℃, permanent change in length after heating 0%, and thermal shock resistance test ≥30 times. The above performances can all meet the international leading level, and can achieve a service life of more than 5 years under the working conditions of 1750℃ and H2 atmosphere in the nuclear fuel sintering process. DETAILED DESCRIPTION

[0035] In order to further understand the present application, the embodiments of the present application are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, and are not limitations of the present application.

[0036] The embodiments of the present application disclose a preparation method of a high-purity alumina corundum product for nuclear fuel sintering, comprising the following steps:

[0037] Step S1: 40wt%~50wt% electrically fused white corundum, 30wt~40wt% tabular corundum, 10wt%~20wt% unsaturated polyester resin solution containing sintered α-Al2O3 micropowder, 200~300PPM active Al2O3 micropowder are mixed, and the material is stuck in a closed container, and after the material is stuck, it is re-mixed; the mass percentage content of sintered α-Al2O3 micropowder in the unsaturated polyester resin solution containing sintered α-Al2O3 micropowder is 4.4wt%~5wt%; the electrically fused white corundum is high-purity electrically fused white corundum with a particle size of ≤5mm, the tabular corundum has a particle size of ≤5mm, the sintered α-Al2O3 micropowder has a D50 of ≤0.045㎜, and the active Al2O3 micropowder has a D50 of ≤50μm,

[0038] The Al2O3 purity of the electrically fused white corundum, tabular corundum, and sintered α-Al2O3 micropowder is ≥97%; and the purity of the active Al2O3 micropowder is ≥99.99.

[0039] Specifically: 40wt%~50wt% electrically fused white corundum, 30wt~40wt% tabular corundum, 10wt%~20wt% unsaturated polyester resin solution containing sintered α-Al2O3 micropowder, and 200~300PPM active Al2O3 micropowder are mixed in a mixer;

[0040] The speed of the mixer is 50~300r / min;

[0041] More specifically: 40wt%~50wt% electrically fused white corundum is added to a mixer with a speed of 50~300r / min, mixed for 5~10 minutes, and uniformly mixed;

[0042] 30wt~40wt% tabular corundum is added, mixed for 5~10 minutes, and uniformly mixed;

[0043] Sintered α-Al2O3 micropowder is added to unsaturated polyester resin to obtain unsaturated polyester resin solution containing sintered α-Al2O3 micropowder, and the mass percentage content of sintered α-Al2O3 micropowder in the unsaturated polyester resin solution containing sintered α-Al2O3 micropowder is 4.4wt%~5wt%; adding sintered α-Al2O3 micropowder in this form can improve the flowability of the material, make it easy to form at room temperature, and have high green body strength; the unsaturated polyester resin is sintered and completely volatilized;

[0044] The unsaturated polyester resin is an m-benzene type unsaturated polyester resin as a solvent, and the α-Al2O3 micropowder should be ensured to be dry and free of impurities. The sintered α-Al2O3 micropowder prepared in advance is added to prepare a solution with an α-Al2O3 micropowder proportion of 4.4wt% to 5wt%. During mixing, attention should be paid to slowly adding the α-Al2O3 micropowder into the resin under low-speed stirring to avoid clumping. The mixing speed is preferably 60 to 100 RPM to reduce the excessive shearing of the α-Al2O3 micropowder and the resin. After the addition of the α-Al2O3 micropowder is completed, the solution should continue to be stirred for sufficient mixing, and the speed at this time is preferably 100 to 200 RPM, and the stirring time is preferably not less than 10 min.

[0045] 10wt% to 20wt% of the unsaturated polyester resin solution containing the sintered α-Al2O3 micropowder is added, and mixed for 5 to 10 min until uniform;

[0046] The active Al2O3 micropowder is added, and mixed for 5 to 10 min until uniform;

[0047] The material is stored in a closed container at room temperature for more than 24 hours to complete the aging;

[0048] The material after aging is subjected to re-mixing for 5 to 10 min to complete the mixing process.

[0049] Step S2: The mixed powder is laid in a mold, and pressed 5 to 10 times at 400t without removing the mold from the pressing position; and then pressed 5 to 10 times at 1000t to obtain a corundum product green body, and the mold is removed;

[0050] Step S3: The formed green body block is transferred to a drying kiln, and dried at room temperature, and then dried by increasing the temperature to 70 to 90℃, and then dried by increasing the temperature to 100 to 120℃;

[0051] The natural drying time is 10 to 36 hours. The natural drying time is 10 to 24 hours in summer, and the natural drying time is 12 to 36 hours in winter;

[0052] The temperature is increased to 70 to 90℃ for drying for 5 to 10 hours, and then the temperature is increased to 100 to 120℃ for drying for 70 to 80 hours;

[0053] Step S4: The dried green body block is loaded into a kiln, and slowly heated to 290 to 310℃ for heat preservation; slowly heated to 590 to 610℃ for heat preservation; slowly heated to 900 to 1000℃ for heat preservation; slowly heated to 1400 to 1550℃ for heat preservation; slowly heated to the firing temperature for heat preservation for 300 to 400 min; after the firing is completed, the heating is stopped, and the kiln is opened after the temperature is naturally reduced to 200℃ in a closed state;

[0054] Specifically, the dried green compact is loaded into a kiln, and heated to 300 DEG C for 170-180 minutes, heated to 600 DEG C for 170-180 minutes, heated to 1000 DEG C for 170-180 minutes, heated to 1400-1550 DEG C for 110-130 minutes, and heated to a firing temperature of 1650 DEG C-1800 DEG C for 300-400 minutes.

[0055] More specifically, the dried green compact is loaded into a kiln, heated to 300 DEG C for 180 minutes, heated to 600 DEG C for 180 minutes, heated to 1000 DEG C for 180 minutes, heated to 1500 DEG C for 120 minutes, and heated to a firing temperature of 1750 DEG C for 360 minutes.

[0056] Step S5: performing final finishing on the sintered corundum product.

[0057] During finishing, a PDC cutter is used to CNC machine the final corundum product to a detailed structure.

[0058] The application also provides a high-purity alumina corundum product for sintering nuclear fuel, which is sintered from 40wt%-50wt% electro-fused white corundum, 30wt%-40wt% tabular corundum, 10wt%-20wt% sintered alpha-Al2O3 micro powder, and 200-300 PPM active Al2O3 micro powder.

[0059] The electro-fused white corundum is high-purity electro-fused white corundum with a particle size of ≤5mm, the tabular corundum has a particle size of ≤5mm, the sintered alpha-Al2O3 micro powder has a D50 of ≤0.045㎜, and the active Al2O3 micro powder has a D50 of ≤50μm.

[0060] The electro-fused white corundum, the tabular corundum, and the sintered alpha-Al2O3 micro powder have an Al2O3 purity of ≥97%, and the active Al2O3 micro powder has a purity of ≥99.99.

[0061] In the application, raw materials are processed through special mixing, molding, drying, sintering, and milling to produce a high-purity alumina corundum refractory product. 3, compressive strength 120-150 MPa, room temperature bending resistance ≥ 25 MPa, high temperature bending resistance ≥ 10 MPa (@ 1250℃*0.5h, referring to the detection method of GB / T3002-2017, high temperature bending resistance experiment at 1250℃ for 0.5h), fire resistance > 1800℃, heating permanent linear change rate 0%, etc. Compared with traditional corundum products, the above chemical indicators, mechanical properties, thermal properties and use performance are significantly improved. At the same time, the method is reproducible and suitable for large-scale production.

[0062] In order to further understand the present application, the high-purity alumina corundum product and the preparation method thereof provided by the present application are described in detail below in combination with examples, and the protection scope of the present application is not limited by the following examples.

[0063] Example 1

[0064] (1) Mixing process: weighing raw materials according to weight percentage, electric smelting white corundum is high-purity electric smelting white corundum with particle size ≤5mm, the tabular corundum has particle size ≤5mm, the sintered α-Al2O3 micro powder has D50 ≤0.045mm, and the active Al2O3 micro powder has D50 ≤50μm,

[0065] The Al2O3 purity of the electric smelting white corundum, tabular corundum and sintered α-Al2O3 micro powder is ≥97%; and the purity of the active Al2O3 micro powder is ≥99.99.

[0066] 40wt%-50wt% of the electric smelting white corundum is added to a mixer with a rotating speed of 50-300r / min, mixed for 5 minutes, and uniformly mixed;

[0067] 30wt-40wt% of the tabular corundum is added, mixed for 5 minutes, and uniformly mixed;

[0068] The sintered α-Al2O3 micro powder is added to the m-phenol type unsaturated polyester resin to obtain an m-phenol type unsaturated polyester resin solution containing sintered α-Al2O3 micro powder, and the mass percentage of the sintered α-Al2O3 micro powder in the m-phenol type unsaturated polyester resin solution containing sintered α-Al2O3 micro powder is 4.4wt%-5wt%;

[0069] 10wt%-20wt% of the m-phenol type unsaturated polyester resin solution containing sintered α-Al2O3 micro powder is added, mixed for 5 minutes, and uniformly mixed;

[0070] The active Al2O3 micro powder is added, mixed for 5 minutes, and uniformly mixed;

[0071] The closed container is closed and stored at room temperature for more than 24 hours to complete the material;

[0072] The material with completed difficult material is re-mixed and mixed for 5 minutes, and the mixing process is completed.

[0073] (2) The mixed powder is weighed according to technical requirements, and is distributed in a mold tool. A 1000t friction press is used for 5 times of 400t pressing, and the upper mold does not separate from the pressing position. Then, 1000t is pressed for 5 times, and a corundum product green body is obtained, and is demolded.

[0074] (3) The shaped green body block is transferred to a drying kiln, and is naturally dried at room temperature for 12 hours, dried at 80℃ for 6 hours, and dried at 110℃ for 72 hours.

[0075] (4) The sintering process is as follows: the dried green body block is loaded into a kiln, heated to 300℃ for 200 minutes, kept for 180 minutes, heated to 600℃ for 100 minutes, kept for 180 minutes, heated to 1000℃ for 120 minutes, kept for 180 minutes, heated to 1500℃ for 240 minutes, kept for 120 minutes, and heated to the sintering process temperature of 1750℃ for 360 minutes. After sintering is completed, heating is stopped, and the kiln is opened after natural cooling to 200℃ in a closed state.

[0076] (5) According to the requirements of the process drawing, the sintered corundum product is finally machined, and a PDC cutter is used to CNC machine the detailed structure of the final corundum product.

[0077] Through experimental verification, the chemical performance can reach Al2O3 purity ≥ 99.5%; the structural performance can reach porosity ≤ 20%, bulk density ≥ 3.3g / cm 3 The mechanical performance can reach compressive strength 120-150MPa, room temperature bending resistance ≥ 25MPa, high temperature bending resistance ≥ 10MPa. The thermal performance and use performance can achieve refractoriness > 1800℃, heating permanent linear change rate 0%, and thermal shock resistance test can reach ≥ 30 times. The above performances can meet the international leading level, and can reach more than 5 years of service life under the working conditions of 1750℃, H2 atmosphere of the nuclear fuel sintering process.

[0078] The above examples are only used to help understand the method of the present application and its core idea. It should be pointed out that for ordinary skilled persons in the art, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

[0079] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing high-purity alumina corundum products for nuclear fuel sintering, characterized in that, Includes the following steps: Step S1: Mix 40wt% to 50wt% fused white corundum, 30wt% to 40wt% tabular corundum, 10wt% to 20wt% unsaturated polyester resin solution containing sintered α-Al2O3 micro powder, and 200 to 300 PPM of active Al2O3 micro powder, and then tame the mixture in a closed container. After tamement, re-mix the mixture. In the unsaturated polyester resin solution containing sintered α-Al2O3 micro powder, the mass percentage of sintered α-Al2O3 micro powder is 4.4 wt% to 5 wt%. Step S2: The mixed powder is spread in the mold and pressed at 400t for 5 to 10 times without falling off the upper mold; then it is pressed at 1000t for 5 to 10 times to obtain the corundum product blank, and then demolded. Step S3: Transfer the formed green blocks to a drying kiln and dry them naturally at room temperature, then heat them to 70-90℃ and then heat them to 100-120℃. Step S4: Load the dried green blocks into the kiln, slowly raise the temperature to 290-310℃ and hold; slowly raise the temperature to 590-610℃ and hold; slowly raise the temperature to 900-1000℃ and hold; slowly raise the temperature to 1400-1550℃ and hold; slowly raise the temperature to the firing temperature and hold; after firing, stop heating and allow the kiln to cool naturally to 200℃ in a closed state before opening. Step S5: Perform final finishing on the sintered corundum product.

2. The method for preparing high-purity alumina corundum products for nuclear fuel sintering according to claim 1, characterized in that, In step S1, 40wt% to 50wt% of fused white corundum, 30wt% to 40wt% of tabular corundum, 10wt% to 20wt% of an unsaturated polyester resin solution containing sintered α-Al2O3 micro powder, and 200 to 300 PPM of active Al2O3 micro powder are mixed evenly in a mixer. The mixing machine operates at a speed of 50–300 r / min.

3. The method for preparing high-purity alumina corundum products for nuclear fuel sintering according to claim 2, characterized in that, Step S1 specifically involves: Add 40wt% to 50wt% fused white corundum to the mixer and mix for 5 to 10 minutes until homogeneous. Add 30wt-40wt% tabular corundum and mix for 5-10 minutes until homogeneous. Sintered α-Al2O3 micro powder is added to unsaturated polyester resin to obtain an unsaturated polyester resin solution containing sintered α-Al2O3 micro powder. The unsaturated polyester resin is an isophthalic unsaturated polyester resin as a solvent. The mass percentage of sintered α-Al2O3 micro powder in the unsaturated polyester resin solution containing sintered α-Al2O3 micro powder is 4.4 wt% to 5 wt%. Add 10wt% to 20wt% of an unsaturated polyester resin solution containing sintered α-Al2O3 micro powder, mix for 5 to 10 minutes until homogeneous; Add activated Al2O3 micro powder and mix for 5-10 minutes until well mixed. The material is sealed in a closed container and stored at room temperature for more than 24 hours to complete the material trapping process; The material that has been trapped is then re-mixed for 5-10 minutes to complete the mixing process.

4. The method for preparing high-purity alumina corundum products for nuclear fuel sintering according to claim 1, characterized in that, In step S3, the natural drying time is 10 to 36 hours.

5. The method for preparing high-purity alumina corundum products according to claim 1, characterized in that, In step S4, the firing temperature is 1650℃~1800℃.

6. The method for preparing high-purity alumina corundum products for nuclear fuel sintering according to claim 5, characterized in that, In step S4, the dried green blocks are loaded into the kiln, heated to 300℃ for 190-210 minutes and held for 170-180 minutes; heated to 600℃ for 90-110 minutes and held for 170-180 minutes; heated to 1000℃ for 110-130 minutes and held for 170-180 minutes; heated to 1400-1550℃ for 230-250 minutes and held for 110-130 minutes; and heated to the firing temperature for 190-210 minutes and held for 300-400 minutes.

7. The method for preparing high-purity alumina corundum products for nuclear fuel sintering according to claim 6, characterized in that, In step S4, the temperature is increased to 300℃ and held for 180 minutes after 200 minutes; the temperature is increased to 600℃ and held for 180 minutes after 100 minutes; the temperature is increased to 1000℃ and held for 180 minutes after 120 minutes; the temperature is increased to 1500℃ and held for 120 minutes after 240 minutes; and the temperature is increased to the firing temperature of 1750℃ and held for 360 minutes after 200 minutes.

8. The method for preparing high-purity alumina corundum products for nuclear fuel sintering according to claim 1, characterized in that, In step S5, during the finishing process, PDC tools are used to CNC machine the final detailed structure of the corundum product.

9. The method for preparing high-purity alumina corundum products for nuclear fuel sintering according to claim 1, characterized in that, The fused white corundum is high-purity fused white corundum with a particle size ≤5mm, the tabular corundum has a particle size ≤5mm, the sintered α-Al2O3 micro powder has a D50 ≤0.045mm, and the active Al2O3 micro powder has a D50 ≤50μm. The Al2O3 purity of fused white corundum, tabular corundum, and sintered α-Al2O3 micro powder is ≥97%; the purity of active Al2O3 micro powder is ≥99.99%.

10. A high-purity alumina corundum product for nuclear fuel sintering, characterized in that, Made by the method described in any one of claims 1 to 9.