Preparation method of coated particle dispersion fuel

Abstract

The invention provides a preparation method of a coated particle dispersion fuel, which comprises the following steps: mixing silicon carbide powder and a binder according to a preset mass ratio, banburying and granulating to obtain a silicon carbide matrix feed; printing a silicon carbide shell green body by using powder extrusion printing equipment and the silicon carbide matrix feed; degreasing the silicon carbide shell green body by using a degreasing solvent to obtain a silicon carbide shell brown blank; a cavity of the silicon carbide shell brown blank is filled with cladding fuel particles, and pores of the cladding fuel particles are filled with silicon carbide powder; and filling the filled silicon carbide shell brown blank into a chemical vapor infiltration device, generating silicon carbide by the introduced methyl trichlorosilane, filling a gap between the silicon carbide powder and the silicon carbide shell green blank with the silicon carbide, and obtaining the coated particle dispersion fuel after the chemical vapor infiltration is completed. By adopting powder extrusion printing and chemical vapor infiltration methods, the problems that the irradiation swelling resistance of existing coated particle dispersion fuel is reduced, the heat conductivity is low, and the loading capacity of coated fuel particles is limited are solved.

Description

Technical Field

[0001] The present application belongs to the technical field of nuclear fuel preparation, and specifically relates to a method for preparing coated particle dispersed fuel. Background Art

[0002] Coated particle dispersed fuel, also known as Fully Ceramic Microencapsulated fuel (FCM fuel), is currently a hot research topic in the field of accident tolerant fuel (ATF) internationally. Coated particle dispersed fuel uses silicon carbide (SiC) as the matrix phase and tri-structural isotropic (TRISO) coated particles (TRISO particles or TRISO coated particles) as the fuel phase. It adopts a structure in which TRISO coated particle fuel is dispersed in the SiC matrix. The SiC matrix is ​​chemically stable and has good compatibility with the coolant. It also has a high melting point, high thermal conductivity and good irradiation stability. TRISO particles can effectively prevent the release of fission products. The combination of SiC matrix and TRISO particles greatly improves the accident tolerance performance of coated particle dispersed fuel compared to traditional UO2.

[0003] The current coated particle dispersion fuel usually adopts the preparation process of "uniform mixing of silicon carbide powder and TRISO particles - green body molding - densification sintering". However, SiC is a high-temperature ceramic with strong covalent bonds and a very low self-diffusion rate, which limits the material transport during its sintering process. Therefore, it is difficult to achieve high densification by diffusion-controlled solid-phase sintering alone. The existing sintering process mainly increases the solid-phase diffusion rate of SiC by adding sintering aids, generates a liquid glass phase by adding sintering aids to assist SiC particles in achieving viscous flow, and increases the sintering temperature and sintering pressure to increase the density of SiC.

[0004] However, in the preparation of coated particle dispersion fuel, there are certain limitations in adding sintering aids, increasing sintering temperature and sintering pressure. The addition of sintering aids will reduce the thermal conductivity of coated particle dispersion fuel to a certain extent; the increase in sintering temperature will easily lead to the phase transformation of SiC matrix from β-SiC to α-SiC, resulting in a decrease in the ability of coated particle dispersion fuel to resist radiation swelling; the increase in sintering pressure will easily lead to the mutual contact, extrusion and even rupture of TRISO particles in the coated particle dispersion fuel pellets during the pressurized sintering process, so the sintering pressure also limits the loading amount of TRISO particles in the coated particle dispersion fuel to a certain extent. Summary of the invention

[0005] In view of this, the embodiments of the present application are committed to providing a method for preparing a coated particle dispersion fuel, which adopts powder extrusion printing and chemical vapor infiltration methods to solve the problems of reduced radiation swelling resistance, low thermal conductivity and limited loading capacity of coated fuel particles in the existing method of preparing coated particle dispersion fuel using sintering process.

[0006] The present application provides a method for preparing a coated particle dispersion fuel, the method comprising: mixing silicon carbide powder and a binder according to a preset mass ratio, and obtaining a silicon carbide matrix feed for powder extrusion printing after banburying and granulation, wherein the preset mass ratio of silicon carbide powder to binder is 4:1 to 20:1; printing a silicon carbide shell green body according to a three-dimensional model of a fuel shell by using a powder extrusion printing device and a silicon carbide matrix feed; and degreasing the silicon carbide shell green body by using a degreasing solvent. After degreasing, a 3D printed silicon carbide shell brown blank is obtained; the cavity of the silicon carbide shell brown blank is filled with coated fuel particles, and then the pores of the coated fuel particles are filled with silicon carbide powder; the silicon carbide shell brown blank filled with coated fuel particles and silicon carbide powder is loaded into a chemical vapor infiltration device, and methyltrichlorosilane is introduced to generate silicon carbide to fill the gap between the silicon carbide powder and the silicon carbide shell green blank, so that the silicon carbide powder and the silicon carbide shell brown blank are integrated and dense, and after the chemical vapor infiltration is completed, the coated particle dispersed fuel is obtained.

[0007] In a specific embodiment of the present application, the temperature range of chemical vapor infiltration is 850° C. to 1300° C., and the reaction time range of chemical vapor infiltration is 1 h to 144 h.

[0008] In a specific embodiment of the present application, silicon carbide powder and a binder are mixed in a preset mass ratio, and after mixing and granulation, a silicon carbide matrix feed for powder extrusion printing is obtained, comprising:

[0009] Start the internal mixer and granulator, set the internal mixing temperature and granulation temperature, turn on the heating, and preheat the internal mixing chamber and granulation barrel; weigh the silicon carbide powder and binder in a preset mass ratio, and add them into the preheated internal mixing chamber; start the rotor, set the internal mixing speed, lower the pressure hammer to pressurize the silicon carbide powder and binder, set the internal mixing time, and start the closed pressurized mixing of the silicon carbide powder and the binder; after the internal mixing time is reached, remove the internal mixing chamber and transfer the evenly mixed silicon carbide powder and binder to the preheated granulation barrel; set the granulation pressure, press the plunger forward, set the pelletizing speed, start the cutter pelletizing, and turn on the pelletizing air cooling switch to avoid particle adhesion. After the granulation is completed, the silicon carbide matrix feed for powder extrusion printing is obtained.

[0010] In a specific embodiment of the present application, the banburying temperature ranges from 140°C to 220°C. The granulation temperature ranges from 120°C to 180°C. The banburying speed ranges from 1 r / min to 40 r / min. The banburying time ranges from 1 h to 6 h. The granulation pressure ranges from 1 MPa to 10 MPa. The pelletizing speed ranges from 50 r / min to 800 r / min.

[0011] In a specific embodiment of the present application, according to the three-dimensional model of the fuel shell, a silicon carbide shell green body is printed using a powder extrusion printing device and a silicon carbide matrix feed, including:

[0012] Feed the silicon carbide matrix into the extruder of the powder extrusion printing equipment, set the nozzle temperature and platform temperature, and preheat it. After the temperature reaches the set temperature, preheat it for more than half an hour to make the silicon carbide particles become a slurry state, and level the printing platform at the same time; select the established fuel shell three-dimensional model for printing, and extrude the heated silicon carbide slurry from the printing nozzle. The printing nozzle moves according to the set fuel shell three-dimensional model and printing speed to print out the silicon carbide shell green body.

[0013] In a specific embodiment of the present application, the nozzle temperature ranges from 120° C. to 200° C. The platform temperature ranges from 100° C. to 150° C. The printing nozzle diameter ranges from 0.4 mm to 1.2 mm, and the printing speed ranges from 5 mm / s to 60 mm / s.

[0014] In a specific embodiment of the present application, a 3D printed silicon carbide shell brown blank is obtained after degreasing a silicon carbide shell green blank with a degreasing solvent, including: immersing the printed silicon carbide shell green blank in a degreasing solvent, heating it in a water bath to dissolve the binder in the green blank in the degreasing solvent, and obtaining a silicon carbide shell brown blank.

[0015] In a specific embodiment of the present application, the cavity of the silicon carbide shell brown blank is filled with coated fuel particles, and then the pores of the coated fuel particles are filled with silicon carbide powder, including:

[0016] The coated fuel particles are added into the cavity of the degreased silicon carbide shell brown blank, and then silicon carbide powder is added to fill the gaps between the coated fuel particles, and the powder is vibrated by a vibrating screen or ultrasonic vibration to ensure that the silicon carbide powder evenly fills the gaps between the coated fuel particles.

[0017] In a specific embodiment of the present application, the water bath heating temperature is 40° C. to 100° C., and the water bath heating time is 6 h to 144 h.

[0018] In a specific embodiment of the present application, a silicon carbide shell brown blank filled with coated fuel particles and silicon carbide powder is loaded into a chemical vapor infiltration device, methyl trichlorosilane is introduced to generate silicon carbide to fill the gap between the silicon carbide powder and the silicon carbide shell green blank, so that the silicon carbide powder and the silicon carbide shell brown blank are integrated and dense, and after the chemical vapor infiltration is completed, a coated particle dispersed fuel is obtained, including:

[0019] The silicon carbide shell brown blank filled with coated fuel particles and silicon carbide powder is loaded into a chemical vapor infiltration device, and methyltrichlorosilane is introduced to generate silicon carbide to fill the gap between the silicon carbide powder and the silicon carbide shell brown blank, so that the silicon carbide powder and the silicon carbide shell green body are integrated and dense. The chemical vapor infiltration temperature is 850°C to 1300°C, and the reaction time is 1h to 144h. After the chemical vapor infiltration is completed, a coated particle dispersed fuel is obtained.

[0020] The beneficial effect of the technical solution of the present application is that: a method for preparing coated particle dispersion fuel based on powder extrusion printing is proposed, and the molding of special-shaped coated particle dispersion fuel is realized through powder extrusion printing, and the densification of coated particle dispersion fuel and high coated fuel particle loading are improved through chemical vapor infiltration method. In addition, compared with the existing method of preparing coated particle dispersion fuel by sintering process, the technical solution provided by the present application does not adopt sintering process, thus avoiding the limitations of adding sintering aids, increasing sintering temperature and sintering pressure during sintering process, and can improve the thermal conductivity and anti-irradiation swelling ability of coated particle dispersion fuel to a certain extent, and also reduce the risk of rupture of coated fuel particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Shown is a schematic flow chart of a method for preparing a coated particle dispersion fuel provided in one embodiment of the present application.

[0022] Figure 2 Shown is a simplified schematic diagram of a process for preparing a coated particle dispersion fuel provided by an embodiment. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0024] At least one embodiment of the present application provides a method for preparing a coated particle dispersion fuel, referring to Figure 1 and Figure 2 The method for preparing the coated particle dispersion fuel includes the following steps.

[0025] S1: Silicon carbide powder and a binder are mixed in a preset mass ratio, and after mixing and granulation, a silicon carbide matrix feed for powder extrusion printing is obtained. The preset mass ratio of silicon carbide powder to binder is 4:1 to 20:1.

[0026] In some embodiments, the silicon carbide powder includes silicon carbide, a mixture of silicon carbide and silicon carbide whiskers, a mixture of silicon carbide and silicon carbide fibers, and other silicides, etc. The binder includes paraffin oil, polyethylene, ethylene-vinyl acetate copolymer, polyethylene glycol, and the like.

[0027] S2: Based on the three-dimensional model of the fuel shell, a silicon carbide shell green body is printed using a powder extrusion printing device and a silicon carbide matrix feeder.

[0028] It should be noted that the three-dimensional model of the fuel shell is a three-dimensional model based on the silicon carbide matrix shell. The thickness of the three-dimensional model of the fuel shell can range from 0.4 mm to 1.6 mm. In this way, the direct preparation of the fuel-free zone is achieved by using the three-dimensional model of the fuel shell, and the thickness of the fuel-free zone ranges from 0.4 mm to 1.6 mm.

[0029] For example, the three-dimensional model of the fuel shell is cylindrical, with a diameter of 22 mm and a thickness of 0.8 mm. For another example, the three-dimensional model of the fuel shell is hexagonal, with a side length of 30 mm and a thickness of 1.2 mm. For another example, the three-dimensional model of the fuel shell is annular, with an outer diameter of 30 mm, an inner diameter of 24 mm and a thickness of 1.2 mm.

[0030] S3: After degreasing the silicon carbide shell green body with a degreasing solvent, a 3D printed silicon carbide shell brown body is obtained.

[0031] In some embodiments, the degreasing solvent includes n-heptane, kerosene, or trichloroethylene.

[0032] S4: Filling the cavity of the silicon carbide shell brown blank with coated fuel particles, and then filling the pores of the coated fuel particles with silicon carbide powder.

[0033] S5: The silicon carbide shell brown blank filled with coated fuel particles and silicon carbide powder is loaded into a chemical vapor infiltration device, and methyltrichlorosilane is introduced to generate silicon carbide to fill the gap between the silicon carbide powder and the silicon carbide shell green blank, so that the silicon carbide powder and the silicon carbide shell brown blank are integrated and dense, and the coated particle dispersed fuel is obtained after the chemical vapor infiltration is completed.

[0034] In some embodiments, the temperature range of chemical vapor infiltration is 850° C. to 1300° C., and the reaction time range of chemical vapor infiltration is 1 h to 144 h.

[0035] The technical solution provided in the embodiment of the present application proposes a method for preparing coated particle dispersion fuel based on powder extrusion printing. Through powder extrusion printing, the molding of special-shaped coated particle dispersion fuel is realized, and through the chemical vapor infiltration method, the densification of the coated particle dispersion fuel and the high coated fuel particle loading are improved. In the embodiment of the present application, according to the three-dimensional model of the fuel shell, the silicon carbide shell green body is printed out using powder extrusion printing equipment and silicon carbide matrix feeding, thereby realizing the direct preparation of the fuel-free zone. In addition, compared with the existing method of preparing coated particle dispersion fuel using sintering process, the technical solution provided in the embodiment of the present application does not use sintering process, thus avoiding the limitations of adding sintering aids, increasing sintering temperature and sintering pressure during the sintering process, and can improve the thermal conductivity and radiation swelling resistance of the coated particle dispersion fuel to a certain extent, and also reduce the risk of rupture of the coated fuel particles.

[0036] In at least one embodiment of the present application, S1-1 to S1-5 are a specific implementation of the above S1.

[0037] S1-1: Start the internal mixer and granulator, set the internal mixer temperature and granulator temperature, turn on the heating, and preheat the internal mixer chamber and granulator barrel.

[0038] In some embodiments, the internal mixing temperature ranges from 140°C to 220°C and the granulation temperature ranges from 120°C to 180°C.

[0039] S1-2: Weigh silicon carbide powder and binder in a preset mass ratio and add them into a preheated mixing chamber.

[0040] S1-3: Start the rotor, set the internal kneading speed, lower the pressure hammer to pressurize the silicon carbide powder and the binder, set the internal kneading time, and start the closed pressurized kneading of the silicon carbide powder and the binder.

[0041] In some embodiments, the kneading speed ranges from 1 r / min to 40 r / min, and the kneading time ranges from 1 h to 6 h.

[0042] S1-4: After the mixing time is reached, the mixing chamber is removed and the evenly mixed silicon carbide powder and binder are transferred to the preheated granulation barrel.

[0043] S1-5: Set the granulation pressure, press the plunger forward, set the pelletizing speed, start the cutter pelletizing, and turn on the pelletizing air cooling switch to avoid pellet adhesion. After granulation is completed, the silicon carbide matrix feed for powder extrusion printing is obtained.

[0044] In some embodiments, the granulation pressure ranges from 1 MPa to 10 MPa, and the pelletizing speed ranges from 50 r / min to 800 r / min.

[0045] In the above embodiments, the molding of matrices such as silicon carbide, a mixture of silicon carbide and silicon carbide whiskers, a mixture of silicon carbide and silicon carbide fibers, and other silicides is achieved by adjusting the composition and ratio of the binder.

[0046] In at least one embodiment of the present application, S2-1 and S2-2 are a specific implementation of the above-mentioned S2.

[0047] S2-1: Feed the silicon carbide matrix into the extruder of the powder extrusion printing equipment, set the nozzle temperature and platform temperature, and preheat it. After the temperature rises to the set temperature, preheat it for more than half an hour to make the silicon carbide particles become a slurry state, and level the printing platform at the same time.

[0048] In some embodiments, the nozzle temperature ranges from 120°C to 200°C and the platform temperature ranges from 100°C to 150°C.

[0049] It should be noted that the number of extruders is not limited to one, and silicon carbide composite materials can be printed.

[0050] S2-2: The established three-dimensional model of the fuel shell is selected for printing, and the heated silicon carbide slurry is extruded from the printing nozzle. The printing nozzle moves according to the set three-dimensional model of the fuel shell and the printing speed to print out the silicon carbide shell green body.

[0051] In some embodiments, the print nozzle diameter ranges from 0.4 mm to 1.2 mm, and the print speed ranges from 5 mm / s to 60 mm / s.

[0052] In at least one embodiment of the present application, S3-1 is a specific implementation of the above S3.

[0053] S3-1: Immerse the printed silicon carbide shell green body in a degreasing solvent and heat it in a water bath to dissolve the binder in the green body in the degreasing solvent to obtain a silicon carbide shell brown body.

[0054] In some embodiments, the water bath heating temperature (ie, the degreasing temperature) is 40° C. to 100° C., and the water bath heating time (ie, the degreasing time) is 6 h to 144 h.

[0055] In at least one embodiment of the present application, S4-1 is a specific implementation of the above-mentioned S4.

[0056] S4-1: Add coated fuel particles into the cavity of the degreased silicon carbide shell brown blank, then add silicon carbide powder to fill the gaps between the coated fuel particles, and compact the powder by a vibrating screen or ultrasonic vibration to ensure that the silicon carbide powder evenly fills the gaps between the coated fuel particles.

[0057] In at least one embodiment of the present application, S5-1 and S5-2 are a specific implementation of the above S5.

[0058] S5-1: Load the silicon carbide shell brown blank filled with coated fuel particles and silicon carbide powder into a chemical vapor infiltration device, and introduce methyltrichlorosilane to generate silicon carbide to fill the gap between the silicon carbide powder and the silicon carbide shell brown blank, so that the silicon carbide powder and the silicon carbide shell green blank are integrated and dense.

[0059] S5-2: After the chemical vapor infiltration is completed, the coated particle dispersed fuel is obtained.

[0060] The coated fuel particles can be selected according to the actual situation, and the embodiments of the present application do not make specific limitations on this. For example, in some embodiments, the coated fuel particles are tri-structural isotropic coated particles. In this way, the coated particle dispersion fuel prepared by the technical solution provided in the embodiments of the present application has high densification and high TRISO particle loading. For example, the typical value of the volume proportion of TRISO particles is 20% to 65%. Accordingly, the density of the coated particle dispersion fuel prepared by the method provided in the embodiments of the present application can reach more than 95% of the theoretical density.

[0061] The specific implementation of the present application is further described below through several specific examples. In the following examples, the coated fuel particles are TRISO particles.

[0062] Embodiment 1:

[0063] Weigh 330g of silicon carbide powder and binder, and add them to a preheated mixing chamber at 190°C. The binder includes 50g of paraffin, 20g of high-density polyethylene, 15g of low-density polyethylene, and 20g of polyethylene glycol. Start the rotor, lower the pressure hammer to pressurize the silicon carbide powder and binder, set the mixing speed to 40r / min, the mixing time to 2h, and pressurize and mix the silicon carbide powder and binder. After the mixing time is reached, remove the mixing chamber and transfer the evenly mixed silicon carbide powder and binder to the preheated granulation barrel. Set the granulation pressure to 5MPa, the pelletizing speed to 200r / min, start the cutter pelletizing, and turn on the pelletizing air cooling switch.

[0064] Feed the pelletized silicon carbide substrate into the extruder of the powder extrusion printing equipment, set the nozzle temperature to 160°C, the platform temperature to 100°C, and preheat and level it. Build a three-dimensional model of the silicon carbide substrate shell for printing. The shell is cylindrical, 22mm in diameter, 0.8mm thick, including the bottom and circumferential shell, and the upper part is open. The printing nozzle moves according to the set model and printing speed. The printing nozzle diameter is 0.8mm, and the printing speed is 50mm / s.

[0065] The printed silicon carbide shell green body was immersed in trichloroethylene solvent and degreased in a water bath at 60°C for 24 hours.

[0066] The coated fuel particles are added into the cavity of the degreased silicon carbide shell, and then silicon carbide powder is added to fill the gaps between the coated fuel particles. The powder is vibrated by a vibrating screen to ensure that the silicon carbide powder evenly fills the gaps between the coated fuel particles.

[0067] The sample filled with coated fuel particles and silicon carbide powder was loaded into a chemical vapor infiltration device, and methyltrichlorosilane was introduced to generate silicon carbide to fill the gap between silicon carbide powder and silicon carbide shell brown blank, so that silicon carbide powder and silicon carbide shell green blank were integrated and compacted. The chemical vapor infiltration temperature was 1200℃ and the reaction time was 72h. After the chemical vapor infiltration was completed, the coated particle dispersed fuel was obtained. The volume fraction of the fuel area coated particle dispersed fuel in the fuel was 60%, and the density of the fuel was 96.4% of the theoretical density.

[0068] Embodiment 2:

[0069] Weigh 330g of silicon carbide powder and binder, and add them to a preheated mixing chamber at 190°C. The binder includes 50g of paraffin, 20g of high-density polyethylene, 15g of low-density polyethylene, and 20g of polyethylene glycol. Start the rotor, lower the pressure hammer to pressurize the silicon carbide powder and binder, set the mixing speed to 40r / min, the mixing time to 2h, and pressurize and mix the silicon carbide powder and binder. After the mixing time is reached, remove the mixing chamber and transfer the evenly mixed silicon carbide powder and binder to the preheated granulation barrel. Set the granulation pressure to 5MPa, the pelletizing speed to 200r / min, start the cutter pelletizing, and turn on the pelletizing air cooling switch.

[0070] Feed the pelletized silicon carbide substrate into the extruder of the powder extrusion printing equipment, set the nozzle temperature to 160°C, the platform temperature to 100°C, and preheat and level it. Build a three-dimensional model of the silicon carbide substrate shell for printing. The shell is a hexagonal prism with a side length of 30mm and a thickness of 1.2mm, including a bottom and a circumferential shell, and an upper opening. The printing nozzle moves according to the set model and printing speed. The printing nozzle diameter is 0.6mm and the printing speed is 50mm / s.

[0071] The printed silicon carbide shell green body was immersed in trichloroethylene solvent and degreased in a water bath at 60°C for 30 hours.

[0072] The coated fuel particles are added into the cavity of the degreased silicon carbide shell, and then silicon carbide powder is added to fill the gaps between the coated fuel particles. The powder is vibrated by a vibrating screen to ensure that the silicon carbide powder evenly fills the gaps between the coated fuel particles.

[0073] The sample filled with coated fuel particles and silicon carbide powder was loaded into a chemical vapor infiltration device, and methyltrichlorosilane was introduced to generate silicon carbide to fill the gap between silicon carbide powder and silicon carbide shell brown blank, so that silicon carbide powder and silicon carbide shell green blank were integrated and compacted. The chemical vapor infiltration temperature was 1200℃ and the reaction time was 72h. After the chemical vapor infiltration was completed, the coated particle dispersed fuel was obtained. The volume fraction of the fuel area coated particle dispersed fuel in the fuel was 65%, and the density of the fuel was 95.8% of the theoretical density.

[0074] Embodiment 3:

[0075] Weigh 330g of silicon carbide powder and binder, and add them to a preheated mixing chamber at 190°C. The binder includes 50g of paraffin, 20g of high-density polyethylene, 15g of low-density polyethylene, and 20g of polyethylene glycol. Start the rotor, lower the pressure hammer to pressurize the silicon carbide powder and binder, set the mixing speed to 40r / min, the mixing time to 2h, and pressurize and mix the silicon carbide powder and binder. After the mixing time is reached, remove the mixing chamber and transfer the evenly mixed silicon carbide powder and binder to the preheated granulation barrel. Set the granulation pressure to 5MPa, the pelletizing speed to 200r / min, start the cutter pelletizing, and turn on the pelletizing air cooling switch.

[0076] Feed the pelletized silicon carbide substrate into the extruder of the powder extrusion printing equipment, set the nozzle temperature to 160°C, the platform temperature to 100°C, and preheat and level it. Build a three-dimensional model of the silicon carbide substrate shell for printing. The shell is annular with an outer diameter of 30mm, an inner diameter of 24mm, and a thickness of 1.2mm, including the bottom and circumferential shell, and the upper part is open. The printing nozzle moves according to the set model and printing speed. The printing nozzle diameter is 0.6mm and the printing speed is 40mm / s.

[0077] The printed silicon carbide shell green body was immersed in trichloroethylene solvent and degreased in a water bath at 60°C for 30 hours.

[0078] The coated fuel particles are added into the cavity of the degreased silicon carbide shell, and then silicon carbide powder is added to fill the gaps between the coated fuel particles. The powder is vibrated by a vibrating screen to ensure that the silicon carbide powder evenly fills the gaps between the coated fuel particles.

[0079] The sample filled with coated fuel particles and silicon carbide powder was loaded into a chemical vapor infiltration device, and methyltrichlorosilane was introduced to generate silicon carbide to fill the gap between silicon carbide powder and silicon carbide shell brown blank, so that silicon carbide powder and silicon carbide shell green blank were integrated and compacted. The chemical vapor infiltration temperature was 1200℃ and the reaction time was 72h. After the chemical vapor infiltration was completed, the coated particle dispersed fuel was obtained. The volume fraction of the fuel area coated particle dispersed fuel in the fuel was 55%, and the density of the fuel was 95.6% of the theoretical density.

[0080] It should be noted that the combination of the various technical features in the embodiments of the present application is not limited to the combination described in the embodiments of the present application or the combination described in the specific embodiments, and all technical features described in the present application can be freely combined or combined in any way unless there is a contradiction between them.

[0081] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the term "comprising" only indicates that the steps and elements that have been clearly identified are included, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0082] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a coated particle dispersion fuel, characterized in that: include: The silicon carbide powder and the binder are mixed in a preset mass ratio, and after banburying and granulation, a silicon carbide matrix feed for powder extrusion printing is obtained, wherein the preset mass ratio of the silicon carbide powder to the binder is 4:1 to 20:1; According to the three-dimensional model of the fuel shell, a silicon carbide shell green body is printed using a powder extrusion printing device and a silicon carbide matrix feeder; After degreasing the silicon carbide shell green body with a degreasing solvent, a 3D printed silicon carbide shell brown body is obtained; Filling the cavity of the silicon carbide shell brown blank with coated fuel particles, and then filling the pores of the coated fuel particles with silicon carbide powder; The silicon carbide shell brown blank filled with coated fuel particles and silicon carbide powder is loaded into a chemical vapor infiltration device, and methyltrichlorosilane is introduced to generate silicon carbide to fill the gap between the silicon carbide powder and the silicon carbide shell green blank, so that the silicon carbide powder and the silicon carbide shell brown blank are integrated and dense, and coated particle dispersed fuel is obtained after the chemical vapor infiltration is completed.

2. The method for preparing a coated particle dispersion fuel according to claim 1, characterized in that: The temperature range of chemical vapor infiltration is 850°C to 1300°C, and the reaction time range of chemical vapor infiltration is 1h to 144h.

3. The method for preparing a coated particle dispersion fuel according to claim 1, characterized in that: The silicon carbide powder and the binder are mixed in a preset mass ratio, and after mixing and granulating, a silicon carbide matrix feed for powder extrusion printing is obtained, including: Start the internal mixer and granulator, set the internal mixing temperature and granulation temperature, turn on the heating, and preheat the internal mixing chamber and granulation barrel; Weigh the silicon carbide powder and binder in a preset mass ratio and add them into the preheated mixing chamber; Start the rotor, set the mixing speed, lower the pressure hammer to pressurize the silicon carbide powder and the binder, set the mixing time, and start the closed pressurized mixing of the silicon carbide powder and the binder; After the mixing time is reached, the mixing chamber is removed and the evenly mixed silicon carbide powder and binder are transferred to the preheated granulation barrel; Set the granulation pressure, press the plunger forward, set the pelletizing speed, start the cutter pelletizing, and turn on the pelletizing air cooling switch to avoid pellet adhesion. After granulation is completed, the silicon carbide matrix feed for powder extrusion printing is obtained.

4. The method for preparing a coated particle dispersion fuel according to claim 3, characterized in that: The mixing temperature range is 140℃~220℃, the granulation temperature range is 120℃~180℃, the mixing speed range is 1r / min~40r / min, the mixing time range is 1h~6h, the granulation pressure range is 1MPa~10MPa, and the pelletizing speed range is 50r / min~800r / min.

5. The method for preparing a coated particle dispersion fuel according to claim 1, characterized in that: According to the three-dimensional model of the fuel shell, the silicon carbide shell green body is printed using a powder extrusion printing device and a silicon carbide matrix feeder, including: Feed the silicon carbide matrix into the extruder of the powder extrusion printing equipment, set the nozzle temperature and platform temperature, and preheat it. After the temperature rises to the set temperature, preheat it for more than half an hour to make the silicon carbide particles into a slurry state, and level the printing platform at the same time; The established three-dimensional model of the fuel shell is selected for printing, and the heated silicon carbide slurry is extruded from the printing nozzle. The printing nozzle moves according to the set three-dimensional model of the fuel shell and the printing speed to print out the silicon carbide shell green body.

6. The method for preparing a coated particle dispersion fuel according to claim 5, characterized in that: The nozzle temperature range is 120℃~200℃, the platform temperature range is 100℃~150℃, the printing nozzle diameter range is 0.4mm~1.2mm, and the printing speed range is 5mm / s~60mm / s.

7. The method for preparing a coated particle dispersion fuel according to claim 1, characterized in that: After degreasing the silicon carbide shell green body with a degreasing solvent, a 3D printed silicon carbide shell brown body is obtained, including: The printed silicon carbide shell green body is immersed in a degreasing solvent and heated in a water bath so that the binder in the green body is dissolved in the degreasing solvent to obtain a silicon carbide shell brown body.

8. The method for preparing a coated particle dispersion fuel according to claim 1, characterized in that: Filling the cavity of the silicon carbide shell brown blank with coated fuel particles, and then filling the pores of the coated fuel particles with silicon carbide powder, including: The coated fuel particles are added into the cavity of the degreased silicon carbide shell brown blank, and then silicon carbide powder is added to fill the gaps between the coated fuel particles, and the powder is vibrated by a vibrating screen or ultrasonic vibration to ensure that the silicon carbide powder evenly fills the gaps between the coated fuel particles.

9. The method for preparing a coated particle dispersion fuel according to claim 8, characterized in that: The water bath heating temperature is 40°C to 100°C, and the water bath heating time is 6h to 144h.

10. A method for preparing a coated particle dispersion fuel according to any one of claims 1 to 9, characterized in that: The silicon carbide shell brown blank filled with coated fuel particles and silicon carbide powder is loaded into a chemical vapor infiltration device, and methyl trichlorosilane is introduced to generate silicon carbide to fill the gap between the silicon carbide powder and the silicon carbide shell green blank, so that the silicon carbide powder and the silicon carbide shell brown blank are integrated and compacted. After the chemical vapor infiltration is completed, the coated particle dispersed fuel is obtained, including: The silicon carbide shell brown blank filled with coated fuel particles and silicon carbide powder is loaded into a chemical vapor infiltration device, and methyltrichlorosilane is introduced to generate silicon carbide to fill the gap between the silicon carbide powder and the silicon carbide shell brown blank, so that the silicon carbide powder and the silicon carbide shell green body are integrated and dense. The chemical vapor infiltration temperature is 850°C to 1300°C, and the reaction time is 1h to 144h. After the chemical vapor infiltration is completed, a coated particle dispersed fuel is obtained.

Images