A method for preparing FCM fuel pellets by gelcasting

Abstract

The application discloses a preparation method of FCM fuel pellets by gel injection molding, which comprises the following steps: preparing SiC-based slurry, injecting the slurry into a mold, adding TRISO fuel particles into the SiC-based slurry, and performing water bath solidification forming to obtain a green pellet, drying and degassing the green pellet to obtain a semi-product pellet, sintering the semi-product pellet to obtain the FCM fuel pellet. The FCM fuel pellet prepared by the gel injection molding technology has a good surface appearance, a compact structure and few surface defects, the volume proportion of the TRISO particles is effectively improved, and the neutron economy of the FCM fuel is improved. The prepared FCM fuel has the characteristics of high thermal conductivity, corrosion resistance, closed fissile product and gas, and the safety of a nuclear reactor is further improved. The preparation method saves the time cost in the production process, improves the production efficiency and is good in economy.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel preparation technology, specifically to a method for preparing FCM fuel pellets by gel injection molding. Background Technology

[0002] FCM fuel is a novel accident-tolerant fuel applicable to various reactor types, including light water reactors. The basic structure of FCM fuel pellets consists of TRISO particles dispersed within a SiC matrix, exhibiting high overall stability and thermal conductivity, as well as good compatibility with coolants. The excellent oxidation resistance and high-temperature resistance of the SiC matrix help maintain structural integrity, while the TRISO particles and the dense SiC matrix provide multiple barriers to prevent the release of fission products, allowing time for safety measures to be implemented and delaying the spread of the accident under accident conditions.

[0003] Currently, FCM fuels are mainly prepared through hot pressing. Existing methods include: Terrani et al. (Kurt A. Terrani, Caen Ang, Lance L. Snead, Yutai Katoh, Irradiation stability and thermal-mechanical properties of NITE-SiC irradiated to 10 dpa, Journal of Nuclear Materials, Volume 499, 2018, Pages 242-247) used nano-infiltration and transient eutectic (NITE) technology to prepare a SiC matrix, and then hot-pressed it at 1800℃–1900℃ and 10–20 MPa pressure to obtain dense FCM fuel pellets; or Cao et al. (Cao, FC; Fan, XH; Liu, B.; Zhao, XF; Guo, FW; Xiao, P., Microstructure and thermalconductivity of fully ceramic microencapsulated fuel fabricated by sparkplasma sintering. Journal of the American .... Journal of the American Journal of Nuclear Materials, Volume 499, 2018, Pages (Ceramic Society 2018, 101 (9), 4224-4236.) Green pellets were prepared by biaxial cold pressing at 5–10 MPa using a steel mold, followed by spark plasma sintering (SPS) at 1800–1850 °C and 10–20 MPa for 10–20 min using a graphite mold. This resulted in fuel pellets with good adhesion between the SiC matrix and the fuel particle spherical coating. However, this method produces FCM fuel pellets with a relatively low volume fraction of TRISO particles, and the preparation process is complex, making industrialization difficult.

[0004] For example, Chinese patent document CN108249926A discloses a method for preparing annular FCM fuel pellets, including the following steps: (1) processing an annular pellet forming mold containing an annular hollow cavity according to the geometric shape of the annular pellet; (2) coating a layer of binder on the surface of TRISO particles, the binder being glycerol diluted with anhydrous ethanol; (3) placing the binder-coated TRISO particles and SiC powder into a container, so that the TRISO particles and SiC powder are uniformly mixed, and a layer of SiC powder is uniformly bonded on the surface of the TRISO particles as a forming raw material; (4) pressing the forming raw material using a forming mold; (5) sintering the annular FCM fuel pellets using spark plasma sintering technology. The FCM fuel pellets prepared by this method have uneven TRISO particle arrangement, uncontrollable spacing, and the coated particles are easily damaged, which may affect the working performance of the FCM fuel pellets. Summary of the Invention

[0005] The purpose of this invention is to propose a gel injection molding method for FCM fuel pellets to solve the problems of low volume fraction of TRISO particles in FCM fuel and breakage due to mutual contact in FCM fuel, which exist in the prior art, and at least provide a beneficial option or create conditions.

[0006] To achieve the above technical objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing FCM fuel pellets by gel injection molding, the method comprising the following steps:

[0008] Step 1: Prepare SiC-based slurry;

[0009] Step 2: Pour the SiC-based slurry into the mold and add TRISO fuel pellets;

[0010] Step 3: Heat the mold to obtain the core block blank;

[0011] Step 4: Dry and remove the glue from the core block green to obtain a semi-finished green;

[0012] Step 5: Sinter the semi-finished green blank to obtain FCM fuel pellets.

[0013] Furthermore, in step 1, the sub-step for preparing the SiC-based slurry is as follows:

[0014] Step 1.1: Mix SiC powder with sintering aids to form a mixed powder;

[0015] The sintering aid is a mixture of alumina and yttrium oxide or a mixture of aluminum nitride and yttrium oxide, and the amount of sintering aid added is 10-20 wt% of the mixed powder.

[0016] Step 1.2: Prepare a mixed solvent by mixing ethanol and water in a volume ratio of (6-7):(3-4), and add the monomer and dispersant to the mixed solvent and stir until homogeneous;

[0017] The monomer is N-hydroxymethylacrylamide, and the dispersant is ammonium polyacrylate; based on the mass of the mixed solvent, the amount of monomer added is 16-20 wt%, and the amount of dispersant added is 1-2%.

[0018] Step 1.3: Pour the mixed powder, mixed solvent, and crosslinking agent into a ball mill jar for ball milling to obtain a viscous slurry;

[0019] The volume ratio of the mixed powder to the solvent is (3-4):(9-10), and the crosslinking agent is methylenebisacrylamide, which is added at 4-5% of the monomer mass.

[0020] Step 1.4: Add initiator and catalyst to the viscous slurry obtained by ball milling, and perform vacuum degassing treatment to obtain SiC-based slurry;

[0021] The initiator is a 10 wt% ammonium persulfate solution, and the amount of initiator added is 0.7-1% of the slurry mass.

[0022] The catalyst is tetramethylethylenediamine, and the amount of catalyst added is 0.04 to 0.6% of the slurry mass.

[0023] Furthermore, in step 2, the bottom diameter of the mold is 30–1000 mm, the height is 50–100 mm, and the mass ratio of the added TRISO particles to SiC powder is 1:(1–3.3).

[0024] Furthermore, in step 3, the sub-step of heating the mold to obtain the core block blank is as follows:

[0025] The mold is heated in a water bath at a temperature of 40–45 °C for 10–15 minutes.

[0026] Further, in step 4, the sub-step of drying and debinding the core block green to obtain a semi-finished green is as follows:

[0027] Step 4.1: Set the drying temperature to 25–30 °C, the drying humidity to 60–65% RH, and the drying time to 24–36 h;

[0028] Step 4.2: Set the drying temperature to 30–35 °C, the drying humidity to 20–25% RH, and the drying time to 12–16 h;

[0029] Step 4.3: Set the drying temperature to 80–90 °C, the drying humidity to 20–25% RH, and the drying time to 6–8 h;

[0030] Step 4.4: Perform debinding to obtain a semi-finished green body; the debinding process is a two-stage debinding process, the atmosphere is nitrogen, the debinding heating rate is 0.2-1 ℃ / min, the maximum temperature is 700-800 ℃, and the maximum temperature is held for 1-2 h before being cooled in the furnace.

[0031] Step 4, the drying process, is divided into three parts. The principle behind this is that the green body contains a large amount of moisture in the early stages of drying, requiring a low drying rate. Therefore, during the drying process, the ambient temperature and humidity are controlled to reduce the moisture concentration gradient between the green body and the environment, thus controlling the dehydration rate of the green body. In the later stages of drying, increasing the drying temperature and decreasing the humidity promotes the solidification of the outer layer particles of the sample, stopping the shrinkage of the sample and maintaining the consistency of moisture diffusion inside and outside the green body, thereby preventing phenomena such as cracking of the green body.

[0032] Further, in step 5, the sub-step of sintering the semi-finished green product to obtain FCM fuel pellets is as follows:

[0033] FCM fuel pellets are obtained by sintering semi-finished green blanks. The sintering method is either spark plasma sintering (SPS) or pressureless sintering.

[0034] Furthermore, in step 5, the conditions for spark plasma sintering (SPS) are: sintering temperature of 1750–1850 °C, sintering atmosphere of argon, heating rate of 100 °C / min, and holding at the highest temperature for 10–20 min.

[0035] Preferably, in step 5, the sintering method is pressureless sintering, the sintering temperature is 1800-1900℃, the sintering atmosphere is argon, the heating rate is 10-15℃ / min, and the temperature is held at the highest temperature for 2-2.5 h.

[0036] Preferably, the volume fraction of TRISO particles in the obtained FCM fuel pellets is 30-60%.

[0037] Preferably, all undefined variables in this invention, if not explicitly defined, can be manually set thresholds.

[0038] Compared with the prior art, the present invention has the following beneficial technical effects:

[0039] This invention utilizes gel casting technology to prepare FCM fuel pellets with a good surface appearance, dense structure, and significantly fewer surface defects. This greatly simplifies the preparation process of FCM fuel pellets, resulting in faster molding times and easier industrialization. By adjusting appropriate proportions and process parameters, ceramic powder, dispersant, solvent, and other ingredients are mixed in a liquid state, and then a green body of a certain shape is obtained through solvent removal. This green body effectively encapsulates TRISO particles, producing high-performance FCM fuel pellets.

[0040] The gel casting technology proposed in this invention effectively increases the volume fraction of TRISO particles, improving the neutron economy of FCM fuel. The prepared FCM fuel exhibits high thermal conductivity, corrosion resistance, and the ability to seal fission products and gases, further enhancing the safety of nuclear reactors. The low-toxicity gel casting system used poses less harm to humans. Compared to the casting and lamination method for preparing FCM fuel, this invention significantly reduces the number of steps in FCM fuel pellet preparation, saving time and increasing production efficiency. Attached Figure Description

[0041] The above and other features of the present invention will become more apparent from the detailed description of the embodiments shown in conjunction with the accompanying drawings. In the accompanying drawings, the same reference numerals denote the same or similar elements. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort. In the drawings:

[0042] Figure 1 A flowchart of a gel injection molding method for preparing FCM fuel pellets provided by the present invention;

[0043] Figure 2 This is a photograph of the FCM fuel pellets after SPS sintering.

[0044] Figure 3 Electron micrograph of the polished surface of an FCM fuel pellet. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0046] It should also be understood that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0047] like Figure 1 The diagram shows a flowchart of a gel injection molding method for preparing FCM fuel pellets. The following section will discuss this method in conjunction with... Figure 1 This invention describes a method for preparing FCM fuel pellets using gel injection molding according to an embodiment of the present invention. The method includes the following steps:

[0048] Step 1: Prepare SiC-based slurry;

[0049] Step 2: Pour the SiC-based slurry into the mold and add TRISO fuel pellets;

[0050] Step 3: Heat the mold to obtain the core block blank;

[0051] Step 4: Dry and remove the glue from the core block green to obtain a semi-finished green;

[0052] Step 5: Sinter the semi-finished green blank to obtain FCM fuel pellets.

[0053] The following is an exemplary description of a gel injection molding method for preparing FCM fuel pellets provided by the present invention.

[0054] Example 1

[0055] Weigh 45 g of SiC powder, 2.15 g of Al2O3 powder, and 2.85 g of Y2O3 powder and mix them in a ball mill jar. Measure 15 ml of deionized water and 35 ml of anhydrous ethanol to prepare a mixed solvent. Weigh 10.7 g of monomer (N-hydroxymethylacrylamide) and pour it into the mixed solvent. Stir until it is completely dissolved.

[0056] Add 1.5 g of dispersant (ammonium polyacrylate) dropwise to the mixed solvent and stir until homogeneous. Weigh 0.36 g of crosslinking agent (methylenebisacrylamide) and add it to the ball mill jar. Pour in the mixed solvent, cover the ball mill jar, and place it in the ball mill for 3 hours. Set the speed of the ball mill to 300 r / min.

[0057] The slurry obtained after ball milling is transferred to a slurry tank for a vacuum defoamer. A 10 wt% initiator solution (ammonium persulfate solution) and a catalyst (N,N,N'N'-tetramethylethylenediamine (TEMED)) are added. 0.07 g of initiator solution and 0.004 g of catalyst are added for every 10 g of slurry.

[0058] Place the slurry tank into a vacuum degassing machine for degassing for 20 minutes. After degassing, slowly inject the ceramic slurry into the mold along the mold wall. Then add TRISO particles to the mold, with a mass of 30% of the SiC powder mass. Shake well to allow the TRISO particles to settle to the bottom of the mold and be neatly arranged. After completion, place the mold in a water bath and heat it at 45 ℃ for 10 minutes. At this point, the green body is basically solidified and no longer flows.

[0059] The mold was placed in a constant temperature and humidity chamber for 24 hours to dry at 25 ℃ and 60%RH. After demolding, it was dried in the constant temperature and humidity chamber for another 12 hours at 35 ℃. After drying, the sample shrinkage was basically complete. Then it was placed in an electric heating forced air drying oven for 8 hours at 80 ℃.

[0060] The drying process is divided into three parts. The principle behind this is that the green body contains a large amount of moisture in the early stages of drying, requiring a low drying rate. Therefore, a lower ambient temperature and higher humidity are set during the drying process to reduce the moisture concentration gradient between the green body and the environment, thus controlling the dehydration rate of the green body. In the later stages of drying, increasing the drying temperature and decreasing the humidity promotes the solidification of the outer layer particles of the sample, stopping the shrinkage of the sample and maintaining the consistency of moisture diffusion inside and outside the green body, thereby preventing phenomena such as cracking of the green body.

[0061] After drying, the material is placed in a tube furnace for debinding under an argon atmosphere. The temperature is first increased to 300 °C at a rate of 1 °C / min, and then held at 300 °C for 2 hours. The temperature is then increased to 500 °C at a rate of 0.5 °C / min and held for 2 hours. Finally, the temperature is increased to 800 °C at a rate of 1 °C / min and held for 2 hours before being cooled with the furnace.

[0062] The degelatinized sample was subjected to discharge plasma sintering under the following conditions: sintering temperature of 1800℃, sintering atmosphere of argon, heating rate of 100℃ / min, and holding at the highest temperature for 10 min.

[0063] Example 2

[0064] Weigh 42.5 g of SiC powder, 3.23 g of Al2O3 powder, and 4.27 g of Y2O3 powder and mix them in a ball mill jar. Measure 17 ml of deionized water and 33 ml of anhydrous ethanol to prepare a mixed solvent. Weigh 7.5 g of monomer (N-hydroxymethylacrylamide) and pour it into the mixed solvent. Stir until it is completely dissolved. Add 1.5 g of dispersant (ammonium polyacrylate) to the mixed solvent and stir until it is evenly mixed. Weigh 0.36 g of crosslinking agent (methylenebisacrylamide) and add it to the ball mill jar. Pour in the mixed solvent, cover the ball mill jar, and place it in a ball mill for 3 hours. The speed of the ball mill is 300 r / min.

[0065] The slurry obtained after ball milling is transferred to a slurry tank for a vacuum defoamer. A 10 wt% initiator solution (ammonium persulfate solution) and a catalyst (N,N,N'N'-tetramethylethylenediamine (TEMED)) are added. 0.06 g of initiator solution and 0.004 g of catalyst are added for every 10 g of slurry.

[0066] The slurry tank is placed in a vacuum degassing machine for degassing for 20 minutes. After degassing, the ceramic slurry is slowly injected into the mold along the mold wall. Then, TRISO particles are added to the mold, with a mass of 50% of the SiC powder mass. The mixture is stirred evenly so that the TRISO particles can settle to the bottom of the mold and be arranged neatly. After completion, the mold is placed in a water bath and heated in a water bath at a temperature of 40 ℃ for 15 minutes. At this point, the green body is basically solidified and no longer flows.

[0067] The mold was placed in a constant temperature and humidity chamber for 24 hours to dry at 25 ℃ and 60%RH. After demolding, it was dried in the constant temperature and humidity chamber for another 16 hours at 35 ℃ and 20%RH. After drying, the sample shrinkage was basically complete. Then it was placed in an electric heating forced air drying oven for 6 hours at 80 ℃.

[0068] The drying process is divided into three parts. The principle behind this is that the green body contains a large amount of moisture in the early stages of drying, requiring a low drying rate. Therefore, a lower ambient temperature and higher humidity are set during the drying process to reduce the moisture concentration gradient between the green body and the environment, thus controlling the dehydration rate of the green body. In the later stages of drying, increasing the drying temperature and decreasing the humidity promotes the solidification of the outer layer particles of the sample, stopping the shrinkage of the sample and maintaining the consistency of moisture diffusion inside and outside the green body, thereby preventing phenomena such as cracking of the green body.

[0069] After drying, the material is placed in a tube furnace for debinding under an argon atmosphere. The temperature is first increased to 300 °C at a rate of 1 °C / min, and then held at 300 °C for 2 hours. The temperature is then increased to 500 °C at a rate of 0.5 °C / min and held for 2 hours. Finally, the temperature is increased to 800 °C at a rate of 1 °C / min and held for 2 hours before being cooled with the furnace.

[0070] The degelatinized sample was subjected to discharge plasma sintering under the following conditions: sintering temperature of 1800 ℃, sintering atmosphere of argon, heating rate of 100 ℃ / min, and holding at the highest temperature for 10 min.

[0071] Example 3

[0072] Weigh 40 g of SiC powder, 4.3 g of Al2O3 powder, and 5.7 g of Y2O3 powder and mix them in a ball mill jar. Measure 17 ml of deionized water and 33 ml of anhydrous ethanol to prepare a mixed solvent. Weigh 10 g of monomer (N-hydroxymethylacrylamide) and pour it into the mixed solvent. Stir until it is completely dissolved. Add 1.7 g of dispersant (ammonium polyacrylate) to the mixed solvent and stir until it is evenly mixed. Weigh 0.35 g of crosslinking agent (methylenebisacrylamide) and add it to the ball mill jar. Pour in the mixed solvent, cover the ball mill jar, and place it in a ball mill for 3 hours. The speed of the ball mill is 300 r / min.

[0073] The slurry obtained after ball milling was transferred to a slurry tank specifically designed for a vacuum degassing machine. A 10 wt% initiator solution (ammonium persulfate solution) and a catalyst (N,N,N'N'-tetramethylethylenediamine (TEMED)) were added, with 0.06 g of initiator solution and 0.004 g of catalyst added per 10 g of slurry. The slurry tank was then placed in the vacuum degassing machine for 20 minutes. After degassing, the ceramic slurry was slowly poured into the mold along the mold wall. TRISO particles, accounting for 90% of the SiC powder mass, were then added to the mold and stirred thoroughly to ensure the TRISO particles settled to the bottom of the mold and arranged neatly. The mold was then placed in a water bath at 40 ℃ for 15 minutes. At this point, the green body was essentially solidified and no longer flowable.

[0074] The mold was placed in a constant temperature and humidity chamber for 24 hours to dry at 30 ℃ and 60%RH. After demolding, it was dried in the constant temperature and humidity chamber for another 12 hours at 35 ℃ and 20%RH. After drying, the sample shrinkage was basically complete. Then it was placed in an electric heating forced air drying oven for 8 hours at 90 ℃.

[0075] The drying process is divided into three parts. The principle behind this is that the green body contains a large amount of moisture in the early stages of drying, requiring a low drying rate. Therefore, a lower ambient temperature and higher humidity are set during the drying process to reduce the moisture concentration gradient between the green body and the environment, thus controlling the dehydration rate of the green body. In the later stages of drying, increasing the drying temperature and decreasing the humidity promotes the solidification of the outer layer particles of the sample, stopping the shrinkage of the sample and maintaining the consistency of moisture diffusion inside and outside the green body, thereby preventing phenomena such as cracking of the green body.

[0076] After drying, the material is placed in a tube furnace for debinding under an argon atmosphere. The temperature is first increased to 300 °C at a rate of 1 °C / min, and then held at 300 °C for 2 hours. The temperature is then increased to 500 °C at a rate of 0.3 °C / min and held for 2 hours. Finally, the temperature is increased to 700 °C at a rate of 1 °C / min and held for 2 hours before being cooled with the furnace.

[0077] The debinding sample was sintered without pressure under the following conditions: sintering temperature of 1880 ℃, sintering atmosphere of argon, heating rate of 10 ℃ / min, and holding at the highest temperature for 2 h.

[0078] like Figure 2 The image shown is a physical picture of the FCM fuel pellet after SPS sintering. The bottom diameter of the sample is 28 mm and the height is 3 mm.

[0079] like Figure 3 The image shown is an electron microscope image of the polished surface of an FCM fuel pellet. The circles are polished TRISO pellet spherical models. The TRISO pellets in the image are not in direct contact. The minimum distance between the pellet shells is 20.0 μm and the average distance is 52.4 μm.

[0080] The TRISO particles in the obtained FCM fuel pellets are all in contact with each other, which avoids the shell cracking caused by particle compression and also reduces the uneven heat distribution of the FCM fuel caused by the dense TRISO particles. The smaller the gap between the particles, the more TRISO particles are contained in the FCM fuel, the higher the volume fraction of TRISO particles, and the higher the neutron economy of the FCM fuel.

[0081] Preferably, all undefined variables in this invention, if not explicitly defined, can be manually set thresholds.

[0082] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0083] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing FCM fuel pellets by gel injection molding, characterized in that, The method includes the following steps: Step 1, Prepare SiC-based slurry: Step 1.1: Mix SiC powder with sintering aids to form a mixed powder; The sintering aid is a mixture of alumina and yttrium oxide or a mixture of aluminum nitride and yttrium oxide, and the amount of sintering aid added is 5-20 wt% of the mixed powder. Step 1.2: Prepare a mixed solvent by mixing ethanol and water in a volume ratio of (6~7):(3~4), and add the monomer and dispersant to the mixed solvent and stir until homogeneous; The monomer is N-hydroxymethylacrylamide, and the dispersant is ammonium polyacrylate; based on the mass of the mixed solvent, the amount of monomer added is 16~20 wt%, and the amount of dispersant added is 1~2%. Step 1.3: Pour the mixed powder, mixed solvent, and crosslinking agent into a ball mill jar for ball milling to obtain a viscous slurry; The volume ratio of the mixed powder to the solvent is (3~4):(9~10), and the crosslinking agent is methylenebisacrylamide, which is added at 4~5% of the monomer mass. Step 1.4: Add initiator and catalyst to the viscous slurry obtained by ball milling, and perform vacuum degassing treatment to obtain SiC-based slurry; The initiator is a 10 wt% ammonium persulfate solution, and the amount of initiator added is 0.7-1% of the slurry mass. The catalyst is tetramethylethylenediamine, and the amount of catalyst added is 0.04~0.6% of the slurry mass. Step 2: Pour the SiC-based slurry into the mold and add TRISO fuel pellets; Step 3: Heat the mold to obtain the core block blank; Step 4: Dry and remove the glue from the core block green to obtain a semi-finished green: Step 4.1: Set the drying temperature to 25~30 ℃, the drying humidity to 60~65%RH, and the drying time to 24~36 h; Step 4.2: Set the drying temperature to 30~35 ℃, the drying humidity to 20~25%RH, and the drying time to 12~16 h; Step 4.3: Set the drying temperature to 80~90 ℃, the drying humidity to 20~25%RH, and the drying time to 6~8 h; Step 4.4: Perform debinding to obtain a semi-finished green body; wherein the debinding process is a two-stage debinding process, the atmosphere is nitrogen, the debinding heating rate is 0.2~1 ℃ / min, the maximum temperature is 700~800 ℃, and the maximum temperature is held for 1~2 h before being cooled in the furnace. Step 5: Sinter the semi-finished green blank to obtain FCM fuel pellets.

2. The method for preparing FCM fuel pellet gel injection molding according to claim 1, characterized in that, The ball milling time is 3~5 hours, and the ball mill speed is 300~350 r / min; the vacuum degree of the vacuum degassing treatment is -0.05~-0.1 Pa, and the degassing time is 20~30 min.

3. The method for preparing FCM fuel pellet gel injection molding according to claim 1, characterized in that, In step 2, the bottom diameter of the mold is 30~1000 mm and the height is 50~100 mm. The mass ratio of TRISO particles to SiC powder is 1:(1-3.3).

4. The method for preparing FCM fuel pellet gel injection molding according to claim 1, characterized in that, In step 3, the sub-step of heating the mold to obtain the core block blank is as follows: The mold is heated in a water bath at a temperature of 40-45 ℃ for 10-15 minutes.

5. The method for preparing FCM fuel pellet gel injection molding according to claim 1, characterized in that, In step 5, the sub-step of sintering the semi-finished green product to obtain FCM fuel pellets is as follows: FCM fuel pellets are obtained by sintering semi-finished green blanks. The sintering method is either spark plasma sintering (SPS) or pressureless sintering.

6. The method for preparing FCM fuel pellet gel injection molding according to claim 5, characterized in that, The conditions for spark plasma sintering (SPS) are: sintering temperature of 1550~1850 ℃, sintering atmosphere of argon, heating rate of 100℃ / min, and holding at the highest temperature for 5~20 min.

7. The method for preparing FCM fuel pellet gel injection molding according to claim 5, characterized in that, The conditions for pressureless sintering are: sintering temperature of 1800~1900 ℃, sintering atmosphere of argon, heating rate of 10~15 ℃ / min, and holding at the highest temperature for 2~2.5 h.

8. The method for preparing FCM fuel pellet gel injection molding according to claim 1, characterized in that, The volume fraction of TRISO particles in FCM fuel pellets is 30-60%.

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