Prismatic TRISO particle dispersion additive fuel element as well as preparation method and application thereof

Abstract

The invention discloses a prismatic TRISO particle dispersion additive fuel element as well as a preparation method and application thereof, and relates to the technical field of nuclear fuel. The method comprises the following steps: preparing the SiC shell by adopting a binder injection molding process or a photocuring molding process; the SiC shell is subjected to degreasing treatment; carrying out chemical vapor infiltration pretreatment on the SiC shell subjected to degreasing treatment; the pretreated SiC shell is filled with simulated TRISO particles and SiC matrix powder, high-solid-content SiC slurry is adopted for packaging, then an enhanced chemical vapor infiltration method is adopted for densifying the dried additive SiC element, and the prismatic TRISO particle dispersion additive fuel element is obtained. The TRISO fuel particles with high inherent safety and the nuclear-grade SiC ceramic material with excellent high-temperature resistance and irradiation resistance are combined, the additive manufacturing process is matched, the design flexibility and expansibility are improved, and the TRISO fuel particles have large application potential in the high-temperature gas cooled reactor.

Description

Technical Field

[0001] The present invention relates to the field of nuclear fuel technology, and in particular to a prismatic TRISO particle dispersion additive fuel element and a preparation method and application thereof. Background Art

[0002] Advanced manufacturing (such as additive manufacturing) and artificial intelligence technologies provide technical support for the development and deployment of advanced reactors. By integrating multidisciplinary advances, the design, manufacturing, evaluation and deployment of advanced nuclear energy systems can be accelerated to achieve the goals of significantly reducing costs, improving the deployment efficiency of new reactors, and accelerating nuclear energy innovation and modernization.

[0003] Advanced manufacturing combined with intelligent design has created basic conditions for the revolutionary change of reactor types. On the one hand, it allows high-performance SiC materials and tri-structural isotropic particle fuel (TRISO) to be prepared into structurally integrated SiC-TRISO fuel components, which improves the efficiency of core construction and reduces deployment costs while ensuring safety; on the other hand, advanced additive manufacturing technology is used to give core fuel components unlimited design space, and to prepare integrated fuel components that are not restricted by traditional manufacturing geometric dimensions. Geometric complexity can be manipulated to enhance the required performance characteristics, such as adding surface features to complex nuclear fuel elements, optimizing the topology of components, achieving better neutron economy or heat transfer characteristics, and adjusting power and coolant distribution, reducing temperature gradients and maintaining low stress levels in core components, providing sufficient conditions for reactor power optimization.

[0004] Therefore, conducting research on advanced additive manufacturing technology and intelligent design for TCR core fuel components, completing the evaluation of the core performance and service behavior of the components, and establishing the corresponding performance degradation mechanism and reliability evaluation of the components are the key to achieving this paradigm shift in reactor deployment, and also determine the design, manufacturing and safe service life of the reactor; in addition, the development of additive manufacturing technology suitable for various advanced nuclear energy systems is also an inevitable trend in the design and development of advanced reactors, which can effectively shorten their research and development, evaluation, verification and application cycles.

[0005] Currently, the Oak Ridge National Laboratory in the United States has completed the preliminary design, manufacturing and evaluation of the Transformation Challenge Reactor. From the overall feature design of the reactor, the structural optimization design of the fuel components to the integrated additive manufacturing of SiC-TRISO fuel components, and the evaluation of the key service performance of the components (mechanical properties, thermophysical properties, and radiation resistance), all have been completed and supported by relevant public data.

[0006] Existing technologies combine binder jet printing and chemical vapor infiltration in a process that can produce high-purity, fully crystalline ceramics, properties that are critical for achieving ideal performance in extremely high-temperature applications or where displacement damage is present.

[0007] The technicians in this field also obtain submicron silicon carbide powder with reduced absorbance and no silicon dioxide impurities on the surface by means of physical modification under a specific heat treatment system to solve the problem of 3D printing silicon carbide molding accuracy in the prior art. At the same time, the technicians in this field also use a two-dimensional characteristic model to simulate the thermodynamic behavior of fully ceramic microencapsulated dispersion (FCM) fuels with different fuel-free zone thicknesses. By optimizing the fuel-free zone thickness and adjusting the spacing between TRISO particles, the fuel-free zone and the SiC layer are ensured to have a low stress level at the same time. Structural optimization provides a basis for the application of FCM fuel.

[0008] In the existing technology, the geometric flexibility of traditional graphite-based fuel elements is limited, and there are limitations in the volume utilization of the fuel phase, which fails to fully utilize the fuel potential. In addition, the stability and performance of graphite-based fuel elements under high temperature and high radiation conditions are challenging and cannot meet the reliability and safety requirements of new reactor types. Summary of the invention

[0009] In view of the deficiencies in the above-mentioned background technology, the present invention mainly solves the problems of the existing traditional graphite-based fuel elements in terms of geometric design flexibility, fuel phase volume utilization, and stability and performance under high temperature and high radiation conditions.

[0010] The present invention provides a prismatic TRISO particle dispersion additive fuel element and a preparation method and application thereof. The method studies four main process flows, namely additive manufacturing, shell pre-CVI, particle filling method, and CVI densification, respectively, and obtains an ideal densified simulated fuel element. The prismatic TRISO dispersion fuel element combines the characteristics of TRISO fuel particles with high inherent safety and nuclear-grade SiC ceramic materials with excellent high temperature resistance and irradiation performance, and cooperates with additive manufacturing technology to improve the flexibility and scalability of the design, and has great application potential in high-temperature gas-cooled reactors.

[0011] The first object of the present invention is to provide a method for preparing a prismatic TRISO particle dispersion augmented fuel element, comprising the following steps:

[0012] The SiC shell is prepared by a binder injection molding process or a light-curing molding process; wherein the SiC shell is a prismatic shell with a cavity structure inside;

[0013] Degreasing the SiC shell;

[0014] The degreased SiC shell is pretreated by chemical vapor infiltration to obtain a pretreated SiC shell;

[0015] The pretreated SiC shell is filled with simulated TRISO particles and SiC matrix powder, and the port is packaged with SiC slurry. After drying at 80°C for 10-20 hours, the dried additive SiC element is densified by enhanced chemical vapor infiltration. Trichloromethylsilane is used as the source gas, hydrogen is used as the carrier gas, and hydrogen and argon are used as the dilution gases, wherein the molar ratio of hydrogen to trichloromethylsilane is 11-8:1, the deposition temperature is controlled at 1000-1200°C, the carrier gas hydrogen flow rate is 3-5L / min, the dilution gas hydrogen flow rate is 1-3L / min, the dilution gas argon flow rate is 3-6L / min, the deposition pressure is 3-10kPa, and the deposition time is 96-120h, so as to obtain a prismatic TRISO particle dispersion additive fuel element.

[0016] Preferably, the SiC shell is prepared by a binder injection molding process, comprising:

[0017] Select SiC powder with a particle size of 30-40 μm, the phase is α phase or β phase, and the mass proportion is 80-95%; select a binder with a mass proportion of about 5-20%;

[0018] The printing speed is 30-80mm / s, and the printing layer thickness is 0.03-0.06mm.

[0019] Preferably, the adhesive is a water-based adhesive C6H 10 A mixed adhesive of O5 and phenolic resin, with a mass ratio of 1:1-2.

[0020] Preferably, the SiC shell is prepared by a photocuring molding process, comprising:

[0021] SiC powder, resin monomer, photoinitiator and dispersant are prepared to obtain SiC ceramic slurry;

[0022] The SiC ceramic slurry is ball-milled for a period of time and then photocured to obtain a SiC shell;

[0023] The SiC powder is 5-40 μm in size, the phase is β-phase silicon carbide, and the Si / C atomic percentage is 1-1.05;

[0024] The resin monomers include HDDA and TMPTA, wherein the HDDA accounts for 40-55% of the total mass of the resin monomers;

[0025] The dispersant is a mixed dispersant of KOS110 and Solsperse 17000 in a mass ratio of 1:1-1:2, and the content is 4-6wt%;

[0026] The ball milling time is 3-5h, at which time the viscosity of the slurry is 2.6-2.8Pa·s (≤3Pa·s);

[0027] The photocuring printing parameters are: slice thickness 50 μm, UV wavelength 405 nm; intensity: 7.5 mw / cm2; exposure time: 30 seconds;

[0028] The solid content of the SiC ceramic slurry is 40-45 vol%.

[0029] Preferably, the SiC shell prepared by the photocuring molding process has a resin content of 50-60%, a wall thickness of 0.8-1 mm, a printing dimensional accuracy of ≥0.08-0.1 mm, and a shell density of 40-50% after printing.

[0030] Preferably, the degreasing treatment includes: a heating rate of 1-3°C / min, maintaining the temperature for 1-3h after reaching 500-600°C, and a cooling rate of 3-5°C / min.

[0031] Preferably, the SiC shell after degreasing is pretreated by chemical vapor infiltration, comprising:

[0032] Trichloromethylsilane is used as the source gas, hydrogen is used as the carrier gas, hydrogen and argon are used as the diluent gas, wherein the molar ratio of hydrogen to trichloromethylsilane is 11-9:1, the deposition temperature is controlled at 900-1080°C, the flow rate of the carrier gas hydrogen is 2-4L / min, the flow rate of the diluent gas hydrogen is 1-2L / min, and the flow rate of the diluent gas argon is 3-4L / min. The deposition pressure is 2-5kPa, and the deposition time is 20-50h;

[0033] The density of the obtained dense SiC shell is 60-70%.

[0034] Preferably, when the simulated TRISO particles and SiC matrix powder are filled into the pretreated SiC shell, the volume ratio of the simulated TRISO particles to the SiC matrix powder is 5.5:4.5.

[0035] A second object of the present invention is to provide a prismatic TRISO particle dispersion augmented fuel element.

[0036] The third object of the present invention is to provide a prismatic TRISO particle dispersion augmented fuel element for use in the nuclear industry.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention provides a prismatic TRISO particle dispersion additive fuel element and a preparation method and application thereof. The present invention adopts a preparation technology combining 3D printing and a two-step chemical vapor deposition process to realize the preparation of a silicon carbide shell with a complex structure, which can break through the traditional core fuel molding method and flow channel design limitations, so that the thermal fluid properties and structural reliability of the reactor core are better.

[0039] The present invention adopts nuclear-grade SiC ceramic material with excellent high-temperature resistance and radiation performance as the shell and coolant channel of the fuel element, thereby improving the high-temperature resistance and radiation resistance.

[0040] The present invention adopts TRISO particle dispersion design to achieve high fuel phase volume, increases the proportion of TRISO particles in fuel elements by filling, chemical vapor infiltration densification, and packaging, and does not require high-temperature sintering, thus solving many drawbacks of the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Printing SiC shell for binder;

[0042] Figure 2 For photocuring treatment of SiC shell;

[0043] Figure 3 Densify the shell for the pre-CVI part;

[0044] Figure 4 This is a schematic diagram after the mixed powder is filled;

[0045] Figure 5 Densified fuel elements for CVI;

[0046] Figure 6 This is the CT effect diagram of the additive SiC-based particle dispersion simulated fuel;

[0047] Figure 7 The microstructure of the SiC shell after densification;

[0048] Figure 8 This is the fuel temperature distribution diagram at the end of life. DETAILED DESCRIPTION

[0049] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0050] The purpose of the present invention is to provide a prismatic TRISO particle dispersion additive fuel element and its preparation method and application. The five main process flows of additive manufacturing, degreasing treatment, shell pre-CVI, particle filling method, and CVI densification are studied respectively to obtain an ideal densified simulated fuel element. The prismatic TRISO dispersion fuel element combines the characteristics of TRISO fuel particles with high inherent safety and nuclear-grade SiC ceramic materials with excellent high temperature resistance and irradiation performance, and cooperates with additive manufacturing technology to improve the flexibility and scalability of the design, and has great application potential in high-temperature gas-cooled reactors.

[0051] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a prismatic TRISO particle dispersion augmented fuel element, comprising the following steps:

[0052] The SiC shell is prepared by a binder injection molding process or a light-curing molding process; wherein the SiC shell is a prismatic shell with a cavity structure inside;

[0053] Degreasing the SiC shell;

[0054] The degreased SiC shell is pretreated by chemical vapor infiltration;

[0055] The pretreated SiC shell is filled with simulated TRISO particles and SiC matrix powder, and the port is sealed with SiC slurry with a high solid content of 80-90% (i.e., the mass ratio of silicon carbide powder to deionized water is 4:1-9:1). The dried additive SiC element is then densified by enhanced chemical vapor infiltration after drying at 80°C for 10-20h. The prismatic TRISO particle dispersed additive fuel element is obtained in a deposition furnace at 1000-1200°C, a deposition pressure of 3-10kPa, and a deposition time of 96-120h.

[0056] The SiC slurry has a solid content of 80-90%, that is, the mass ratio of silicon carbide powder to deionized water is 4-9:1.

[0057] Compared with the preparation process of the traditional rod-type nuclear fuel element, the prismatic dispersed TRISO particle fuel element involved in the present invention adopts additive molding processes such as photocuring molding and binder injection molding to realize the molding of the silicon carbide shell with a complex structure. At the same time, in order to maintain the purity and precision of the nuclear material element, the degreased silicon carbide shell is subjected to multi-step chemical vapor deposition densification, wherein the first step of short-time chemical vapor pre-deposition at a lower temperature can make the silicon carbide shell have a certain strength to ensure the smooth filling of TRISO fuel particles; the second step of long-time chemical vapor pre-deposition after encapsulation and drying can obtain a high-density additive fuel element. The preparation process of the prismatic dispersed TRISO particle fuel element can better control the volume ratio of fuel and coolant, avoid the problem that the internal state of the pebble bed fuel is difficult to detect and control, and the utilization rate of the prismatic fuel is higher.

[0058] In the present invention, when the SiC shell is prepared by the binder injection molding process, the process includes:

[0059] Select SiC powder with a particle size of 30-40 μm, the phase is α phase or β phase, and the mass proportion is 80-95%; select a binder with a mass proportion of about 5-20%;

[0060] The printing speed is 30-80mm / s, and the printing layer thickness is 0.03-0.06mm.

[0061] The adhesive is a water-based adhesive C6H 10 A mixed adhesive of O5 and phenolic resin, with a mass ratio of 1:1-2.

[0062] For binder injection molding, the shell density after printing is 40-50%.

[0063] Exemplarily, when a SiC shell is prepared by a photocuring molding process, the process includes:

[0064] SiC powder, resin monomer, photoinitiator and dispersant are prepared to obtain SiC ceramic slurry;

[0065] The SiC ceramic slurry is ball-milled for a period of time and then photocured to obtain a SiC shell;

[0066] The SiC powder is 5-40 μm in size, the phase is β-phase silicon carbide, and the Si / C atomic percentage is 1-1.05;

[0067] The resin monomers include HDDA and TMPTA, wherein the HDDA accounts for 40-55% of the total mass of the resin monomers;

[0068] The dispersant is a dual dispersant of KOS110 and Solsperse 17000 in a mass ratio of 1:1, with a content of 4-6wt%; the photoinitiator is TPO, with a content of 2wt%;

[0069] The ball milling time is 3-5h, at which time the viscosity of the slurry is 2.6-2.8Pa·s (≤3Pa·s);

[0070] The photocuring printing parameters are: slice thickness 50 μm, UV wavelength 405 nm; intensity: 7.5 mw / cm2; exposure time: 30 seconds;

[0071] The solid content of the SiC ceramic slurry is 40-45 vol%.

[0072] Specifically, the SiC shell prepared by the photocuring molding process has a resin content of 50-60%, a wall thickness of 0.8-1 mm, a printing size accuracy of ≥0.08-0.1 mm, and a shell density of 40-50% after printing.

[0073] In the present invention, the degreasing treatment includes: a heating rate of 1-3°C / min, maintaining the temperature for 1-3h after reaching 500-600°C, and a cooling rate of 3-5°C / min.

[0074] The SiC shell after degreasing is pretreated by chemical vapor infiltration, including:

[0075] Trichloromethylsilane is used as source gas, hydrogen is used as carrier gas, hydrogen and argon are used as diluent gas, wherein the molar ratio of hydrogen to trichloromethylsilane is 11-9:1, the deposition temperature is 900-1080°C, the deposition pressure is 2-5kPa, and the deposition time is 20-50h;

[0076] The density of the obtained dense SiC shell is 60-70%.

[0077] Exemplarily, the shell is pretreated by chemical vapor infiltration (CVI): trichloromethylsilane is used as the source gas, hydrogen is used as the carrier gas, hydrogen and argon are used as the diluent gas, wherein the molar ratio of hydrogen to trichloromethylsilane is 11-9:1, the deposition temperature is controlled at 900-1080°C, the flow rate of the carrier gas hydrogen is 2-4L / min: the flow rate of the diluent gas hydrogen is 1-2L / min: the flow rate of the diluent gas argon is 3-4L / min. The deposition pressure is 2-5kPa, the deposition time is 20-50h, and the shell density obtained after the preliminary CVI process is 60-70%.

[0078] In the present invention, when the simulated TRISO particles and SiC matrix powder are filled into the dense SiC shell, the volume ratio of the simulated TRISO particles to the SiC matrix powder is 5.5:4.5, and the SiC slurry with a solid content of 80-90% (i.e., the mass ratio of silicon carbide powder to deionized water is 4:1-9:1) is used to package the port.

[0079] Exemplarily, a process of mixing particles and then filling is adopted to complete the filling of particles and matrix SiC powder in the additive SiC shell. The particles and SiC powder are weighed according to a volume ratio of 5.5:4.5, and the mixing ratio needs to be slightly higher than 50% of the preset phase volume. The mixture of particles and SiC powder is continuously mixed in a rotary mixer for 72 hours, and the ball mill speed is constant at 450 / min. The mixed particles and powder are poured into the shell in batches and vibrated separately, and the port is encapsulated with SiC mud with a solid content of 80-90% (i.e., the mass ratio of silicon carbide powder to deionized water is 4:1-9:1), and then dried at 80°C for 10-20h, and then the dried additive SiC element is densified by enhanced chemical vapor infiltration: trichloromethylsilane is used as the source gas, hydrogen is used as the carrier gas, hydrogen and argon are used as the diluent gas, wherein the molar ratio of hydrogen to trichloromethylsilane is 11-8:1, the deposition temperature is controlled at 1000-1200°C, the carrier gas hydrogen flow rate is 3-5L / min, the diluent gas hydrogen flow rate is 1-3L / min, and the diluent gas argon flow rate is 3-6L / min. The deposition pressure is 3-10kPa, the deposition time is 96-120h, and the density of the deposited fuel SiC matrix is ​​higher than 85%.

[0080] A second aspect of the present invention provides a prismatic TRISO particle dispersion augmented fuel element.

[0081] A third aspect of the present invention provides an application of a prismatic TRISO particle dispersion augmented fuel element in the nuclear industry.

[0082] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0083] Example 1

[0084] In this embodiment, the prismatic TRISO particle dispersion fuel element is additively manufactured using a binder injection molding process.

[0085] Step 1: Select SiC powder with a particle size of 30 μm, the phase is α phase, the mass ratio is about 85%, and the selected binder is water-based adhesive C6H 10 The mixed adhesive of O5 and phenolic resin has a mass ratio of 1:1.5, and the mass proportion of the adhesive is about 10%. Figure 1Shown is a binder printed SiC housing.

[0086] Step 2: First, spread the dried β-SiC powder all over the powder supply cylinder, and then spread a layer of SiC powder on the work surface. The three-dimensional model of the SiC shell is printed through computer input. The printing speed is 40mm / s, and the printing layer thickness is 0.05mm. The nozzle starts to spray the binder according to the path of the computer slice. After the nozzle completes one inkjet, the working cylinder drops one layer, and the powder supply cylinder rises one layer. The powder spreading process is completed by the rotation and movement of the powder spreading roller. One round trip completes the printing process of the entire SiC shell. After printing, take out the sample for drying and curing, and the shell density is 46%.

[0087] Step 3: Degrease the shell: the heating rate is 2℃ / min, keep warm for 2h after reaching 600℃, and the cooling rate is 4℃ / min.

[0088] Step 4: Pre-treat the shell by chemical vapor infiltration (CVI): trichloromethylsilane is used as the source gas, hydrogen is used as the carrier gas, hydrogen and argon are used as the dilution gases, wherein the molar ratio of hydrogen to trichloromethylsilane is 11:1, the deposition temperature is controlled at 1000°C, the carrier gas hydrogen flow rate is 3L / min: the dilution gas hydrogen flow rate is 1L / min: the dilution gas argon flow rate is 3L / min. The deposition pressure is 2-5kPa, the deposition time is 40h, and the shell density obtained after the preliminary CVI process is 60%. The dimensional accuracy error is controlled within ±0.1mm, and the shell after pre-CVI is as follows Figure 3 shown.

[0089] Step 5: Fill the shell with simulated TRISO particles and SiC matrix powder. The study used simulated TRISO particles with a ZrO2 core. Each coating layer of the simulated TRISO particles was obtained by chemical vapor deposition, and the matrix was made of pure β-SiC powder. The powder mixing process was carried out in a rotary mixer. Before mixing, the simulated particles and SiC powder were weighed according to a volume ratio of 5.5:4.5. 120.9g of simulated particles and 52.8g of SiC powder were weighed. In order to avoid the particle filling fraction being less than the target phase volume, the powder mixing ratio needs to be slightly higher than the preset phase volume of 50%. The mixture of simulated particles and SiC powder was continuously mixed in the rotary mixer for 72 hours, and the ball mill speed was constant at 450 / min. During the transfer and filling of the powder, it is necessary to avoid large-scale vibration under the action of external forces to prevent the powder from falling off. The mixed particles and powder were poured into the shell in batches and compacted separately, and the port was sealed with SiC slurry with a solid content of 90% (i.e., the mass ratio of silicon carbide powder to deionized water was 9:1), and dried at 80°C for 15h. Figure 4 shown.

[0090] Step six: After the shell sample is dried, the deposition temperature is controlled at 1150°C and the pressure is 5-6kPa in a CVI deposition furnace for 100 hours. Trichloromethylsilane is the source gas, hydrogen is the carrier gas, hydrogen and argon are the dilution gases, the molar ratio of hydrogen to trichloromethylsilane is 10:1, the flow rate of the carrier gas hydrogen is 4L / min, the flow rate of the dilution gas hydrogen is 2L / min, and the flow rate of the dilution gas argon is 5L / min. The density of the fuel SiC matrix after deposition is about 85%, and the fuel sample obtained after the final deposition is as follows Figure 5 As shown in Figure 2, the microstructure of the sample shell is as follows: Figure 7 shown.

[0091] Example 2

[0092] In this embodiment, the prismatic TRISO particle dispersion fuel element is additively manufactured using a photo-stereolithography process.

[0093] Step 1: The selected SiC powder is 8μm, the physical phase is β-phase silicon carbide, and the Si / C element atomic percentage is 1:1. The resin monomer in the prepared SiC ceramic slurry is a HDDA-TMPTA dual resin monomer system, in which the HDDA / (HDDA+TMPTA) mass ratio is 50%; the TPO photoinitiator content is 2wt% (relative to the total mass of the resin); the dispersant is a KOS110+17000 dual dispersant with a mass ratio of 1:1, and the optimal content is 5wt%; the solid phase content of the SiC ceramic slurry is 40vol% (≥30vol%); the ball milling time is 4h, at which time the viscosity of the slurry is 2.8Pa·s (≤3Pa·s), and the printing parameters are a slice thickness of 50μm, an ultraviolet wavelength of 405nm; intensity: 7.5mw / cm 2 ; Exposure time: 30 seconds. Figure 2 Shown is a photocured SiC shell.

[0094] Step 2: For the photocuring molding sample, the resin content is 55%, the wall thickness is 0.8mm, the printing size accuracy is not less than 0.08mm, and the shell density is 45% after printing.

[0095] Step 3: Degrease the shell: the heating rate is 2℃ / min, keep warm for 2h after reaching 600℃, and the cooling rate is 4℃ / min.

[0096] Step 4: Pre-treat the shell by chemical vapor infiltration (CVI): trichloromethylsilane is used as the source gas, hydrogen is used as the carrier gas, hydrogen and argon are used as the diluent gas, wherein the molar ratio of hydrogen to trichloromethylsilane is 10:1, the deposition temperature is controlled at 1080°C, the flow rate of the carrier gas hydrogen is 4L / min, the flow rate of the diluent gas hydrogen is 2L / min, and the flow rate of the diluent gas argon is 4L / min. The deposition pressure is 2-5kPa, the deposition time is 50h, and the shell density obtained after the preliminary CVI process is about 65%, and the dimensional accuracy error is controlled within ±0.1mm.

[0097] Step 5: Fill the shell with simulated TRISO particles and SiC matrix powder. Use simulated TRISO particles with a ZrO2 core. Each coating layer of the simulated TRISO particles is obtained by chemical vapor deposition technology, and the matrix is ​​pure β-SiC powder. The powder mixing process is carried out in a rotary mixer. Before mixing, the simulated particles and SiC powder are weighed according to a volume ratio of 5.5:4.5. Weigh 120.9g of simulated particles and 52.8g of SiC powder. In order to avoid the particle filling fraction being less than the target phase volume, the powder mixing ratio needs to be slightly higher than the preset phase volume of 50%. The mixture of simulated particles and SiC powder is continuously mixed in the rotary mixer for 72 hours, and the ball mill speed is constant at 450 / min. During the transfer and filling of the powder, it is necessary to avoid large-scale vibration under the action of external forces to prevent the powder from falling off. The mixed particles and powder were poured into the shell in batches and compacted separately, and the port was sealed with SiC slurry with a solid content of 90% (i.e., the mass ratio of silicon carbide powder to deionized water was 9:1) and dried at 80°C for 15h.

[0098] Step 6: After the shell sample is dried, the deposition temperature is controlled at 1200°C and 6-9kPa pressure in a CVI deposition furnace for 120 hours. Trichloromethylsilane is the source gas, hydrogen is the carrier gas, hydrogen and argon are the dilution gases, the molar ratio of hydrogen to trichloromethylsilane is 9:1, the flow rate of the carrier gas hydrogen is 5L / min, the flow rate of the dilution gas hydrogen is 3L / min, and the flow rate of the dilution gas argon is 6L / min. The density of the fuel SiC matrix after deposition is about 88%. Figure 6 The CT rendering of the additive SiC-based particle dispersion simulated fuel provided in Example 2 shows that the particle sizes of most of the identified particles are relatively consistent, and the particle sizes of a small part of the particles at the bottom are slightly higher.

[0099] like Figure 8 As shown, the temperature field of the unit body provided in Example 2 at the end of its life, from the perspective of overall temperature distribution, the highest temperature of the particles near the central area is about 1050K, which is lower than the fuel temperature peak of 1134K. The cooling effect of most areas of the fuel is better and the temperature is generally lower.

[0100] The present invention describes preferred embodiments and their effects. However, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0101] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a prismatic TRISO particle dispersion fuel element, characterized in that: The following steps are involved: The SiC shell is prepared by a binder injection molding process or a light-curing molding process; wherein the SiC shell is a prismatic shell with a cavity structure inside; Degreasing the SiC shell; The degreased SiC shell is pretreated by chemical vapor infiltration; The pretreated SiC shell is filled with simulated TRISO particles and SiC matrix powder, and the port is packaged with SiC slurry. After drying at 80°C for 10-20 hours, the dried additive SiC element is densified by enhanced chemical vapor infiltration. Trichloromethylsilane is used as the source gas, hydrogen is used as the carrier gas, and hydrogen and argon are used as the dilution gases, wherein the molar ratio of hydrogen to trichloromethylsilane is 11-8:1, the deposition temperature is controlled at 1000-1200°C, the carrier gas hydrogen flow rate is 3-5L / min, the dilution gas hydrogen flow rate is 1-3L / min, the dilution gas argon flow rate is 3-6L / min, the deposition pressure is 3-10kPa, and the deposition time is 96-120h, so as to obtain a prismatic TRISO particle dispersion additive fuel element.

2. The method for preparing a prismatic TRISO particle dispersion fuel element according to claim 1, characterized in that: When the SiC shell is prepared by the binder injection molding process, it includes: Select SiC powder with a particle size of 30-40 μm, the phase is α phase or β phase, and the mass proportion is 80-95%; select a binder with a mass proportion of about 5-20%; The printing speed is 30-80mm / s, and the printing layer thickness is 0.03-0.06mm.

3. The method for preparing a prismatic TRISO particle dispersion fuel element according to claim 2, characterized in that: The adhesive is a water-based adhesive C6H 10 A mixed adhesive of O5 and phenolic resin, with a mass ratio of 1:1-2.

4. The method for preparing a prismatic TRISO particle dispersion fuel element according to claim 1, characterized in that: When the SiC shell is prepared by the light curing molding process, it includes: SiC powder, resin monomer, photoinitiator and dispersant are prepared to obtain SiC ceramic slurry; After ball milling the SiC ceramic slurry for a period of time, the SiC shell body is obtained by photocuring printing, and then the SiC shell is obtained by photocuring; The SiC powder is 5-40 μm in size, the phase is β-phase silicon carbide, and the Si / C atomic percentage is 1-1.05; The resin monomers include HDDA and TMPTA, wherein the HDDA accounts for 40-55% of the total mass of the resin monomers; The dispersant is a dual dispersant of KOS110 and Solsperse 17000 in a mass ratio of 1:1, with a content of 4-6wt%; The ball milling time is 3-5h, at which time the viscosity of the slurry is 2.6-2.8Pa·s (≤3Pa·s); The photocuring printing parameters are: slice thickness 50 μm, UV wavelength 405 nm; intensity: 7.5 mw / cm 2 ;Exposure time: 30 seconds; The solid content of the SiC ceramic slurry is 40-45 vol%.

5. The method for preparing a prismatic TRISO particle dispersion fuel element according to claim 4, characterized in that: The SiC shell prepared by the photocuring molding process has a resin content of 50-60%, a wall thickness of 0.8-1mm, a printing size accuracy of ≥0.08-0.1mm, and a shell density of 40-50% after printing.

6. The method for preparing a prismatic TRISO particle dispersion fuel element according to claim 1, characterized in that: The degreasing treatment includes: a heating rate of 1-3°C / min, maintaining the temperature for 1-3h after reaching 500-600°C, and a cooling rate of 3-5°C / min.

7. The method for preparing a prismatic TRISO particle dispersion fuel element according to claim 1, characterized in that: The SiC shell after degreasing is pretreated by chemical vapor infiltration, including: Trichloromethylsilane is used as the source gas, hydrogen is used as the carrier gas, hydrogen and argon are used as the diluent gas, wherein the molar ratio of hydrogen to trichloromethylsilane is 11-9:1, the deposition temperature is controlled at 900-1080°C, the flow rate of the carrier gas hydrogen is 2-4L / min, the flow rate of the diluent gas hydrogen is 1-2L / min, and the flow rate of the diluent gas argon is 3-4L / min. The deposition pressure is 2-5kPa, and the deposition time is 20-50h; The density of the obtained dense SiC shell is 60-70%.

8. The method for preparing a prismatic TRISO particle dispersion fuel element according to claim 1, characterized in that: When the simulated TRISO particles and SiC matrix powder are filled into the pretreated SiC shell, the volume ratio of the simulated TRISO particles to the SiC matrix powder is 5.5:4.

5.

9. A prismatic TRISO particle dispersion fuel element produced by the method according to any one of claims 1 to 8.

10. Use of the prismatic TRISO particle dispersion fuel element according to claim 9 in the nuclear industry.

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