CA3228079A1 - Homogenized coated particle dispersion fuel and preparation method therefor - Google Patents

Abstract

A homogenized coated particle dispersion fuel and a preparation method therefor. The homogenized coated particle dispersion fuel comprises a matrix material, dressed TRISO coated fuel particles and a series of silicon carbide cylinder bodies (1). The radial uniform distribution of the TRISO coated fuel particles is achieved, the temperature gradient of the coated particle dispersion fuel during operation in a reactor is reduced, the risk of radioactive product release is reduced, and at the same time, the problem of inaccurate neutron physics and thermal hydraulic theory calculation of a gas-cooled microreactor is solved.

Description

HOMOGENIZED COATED PARTICLE DISPERSION FUEL AND
PREPARATION METHOD THEREFOR
The present disclosure claims priority from the Chinese patent application CN
202111026524.4 titled "HOMOGENIZED COATED PARTICLE DISPERSED FUEL
AND MANUFACTURING PROCESS THEREFOR" filed on September 2, 2021, the entirety of which is incorporated herein by reference.
TECHNICAL FIELD
[0001] The present disclosure relates to, but is not limited to, the field of coated particle dispersed fuel manufacture.
BACKGROUND

[0002] A gas-cooled micro-reactor is a micro modular gas-cooled reactor developed and improved based on prismatic high-temperature gas-cooled reactors. The gas-cooled micro-reactor enables no fuel reloading throughout the service life, adopts an inherent safety design, sufficiently simplifies the system configuration, and improves the user's experience by intelligent operation and maintenance as well as modular arrangement and deployment. With the design characteristics of being "inherently safe, intelligent and flexible", the gas-cooled micro-reactor can meet the power supply requirements of special regions such as seabed, isolated islands, remote lands and even outer space.

[0003] Due to the design requirements on inherent safety, no fuel reloading throughout service life, direct helium circulation, less manual intervention and the like of the gas-cooled micro-reactor, the gas-cooled micro-reactor fuel should possess features such as strong stability, corrosion resistance, very little release of fission products and the like.
However, current mature nuclear fuels, such as uranium dioxide fuel pellets for a pressurized water reactor, graphite fuel spheres for a high-temperature gas-cooled reactor and the like, cannot fully meet the design requirements of the gas-cooled micro-reactor fuel. Therefore, a newly proposed brand new fuel, i.e., the coated particle dispersed fuel, is selected as the gas-cooled micro-reactor fuel. This is a columnar fuel formed by dispersing tri-structural isotropic coated particles (TRISO coated fuel particles) into a silicon carbide matrix, where the irradiation stability and chemical stability of the silicon carbide material can ensure a long service life of the fuel, while the dual barrier effect of both the TRISO coated fuel particles and the silicon carbide matrix material on the fission products ensures very little fission product release during operation.

[0004] Different from the fuel moving in the reactor core in the high-temperature gas-cooled reactor, the coated particle dispersed fuel of the gas-cooled micro-reactor is placed in a graphite pore channel throughout the service life without moving, and if there is a temperature gradient within the coated particle dispersed fuel, a direction of the temperature gradient remains unchanged throughout the service life. The TRISO
coated fuel particles form a core component of the coated particle dispersed fuel, while the amoeba effect caused by the temperature gradient is one of the important damage mechanisms causing damage to the TRISO coated fuel particles. In conventional production processes of the coated particle dispersed fuel, no special means is adopted to ensure uniform distribution of the TRISO coated fuel particles, so the TRISO
coated fuel particles may be aggregated in some regions in the produced coated particle dispersed fuel, while other regions have fewer TRISO coated fuel particles, which may cause a higher temperature gradient within the coated particle dispersed fuel, and, further considering the relatively long service life of the coated particle dispersed fuel and the fact that the coated particle dispersed fuel does not move throughout the service life, a more severe amoeba effect may occur, causing damage to the TRISO coated fuel particles and eventually causing release of radioactive fission products.
Since the coated particle dispersed fuel is present in the gas-cooled micro-reactor in the form of a fuel column, the cylindrical side surface of the fuel column is exposed outside and has a lower temperature, a radial temperature gradient is greater than an axial condition.
Therefore, priority needs to be given to solving the problem concerning the radial temperature gradient, that is, optimizing the uniformity of radial distribution of the TRISO coated fuel particles. In addition, current neutron physics and thermal-hydraulic theory calculation and analysis results of the gas-cooled micro-reactor are all based on a homogenized coated particle dispersed fuel, and not quite consistent with the results of the coated particle dispersed fuel with TRISO coated fuel particles in actual use.
Therefore, the problem of inaccurate neutron physics and thermal-hydraulic calculation can be solved by optimizing the uniformity of the TRISO coated fuel particles in the coated particle dispersed fuel.
SUMMARY

[0005] An object of the present disclosure is to provide a homogenized coated particle dispersed fuel and a manufacturing process therefor, which can achieve uniform radial distribution of the TRISO coated fuel particles to optimize uniformity of the TRISO
coated fuel particles in the fuel, reduce the temperature gradient of the coated particle dispersed fuel during operation in the reactor, effectively protect integrity of the coated particle dispersed fuel, reduce the risk of radioactive product release, while solving the problem of inaccuracy in neutron physics and thermal-hydraulic calculation for the gas-cooled micro-reactor.

[0006] To achieve this object, the present disclosure provides a homogenized coated particle dispersed fuel, including a matrix material, overcoated TRISO coated fuel particles, and a series of silicon carbide cylindrical bodies; wherein :
the matrix material is manufactured by adding a sintering additive into nanoscale silicon carbide powder, uniformly mixing the sintering additive and the nanoscale silicon carbide powder, and drying and screening a resulting mixture;
the overcoated TRISO coated fuel particles are obtained by coating surfaces of TRISO coated fuel particles with silicon carbide powder layer, wherein the silicon carbide powder layer includes silicon carbide;
the series of silicon carbide cylindrical bodies are manufactured through a chemical vapor deposition method or a silicon carbide powder sintering process; and the homogenized coated particle dispersed fuel is manufactured by uniformly mixing the overcoated TRISO coated fuel particles and the matrix material with agitation, filling a resulting mixed slurry into gap spaces formed by the series of silicon carbide cylindrical bodies mounted in annular grooves at a bottom of a graphite mold and the graphite mold, and then performing pressure sintering.

[0007] The TRISO coated fuel particles are tri-structural isotropic coated fuel particles.

[0008] Further, in the homogenized coated particle dispersed fuel, the volume proportion of the matrix material is 50% to 65%, the volume proportion of the overcoated TRISO coated fuel particles is 10% to 42%, and the volume proportion of the series of silicon carbide cylindrical bodies is 8% to 25%.

[0009] Further, the matrix material is manufactured by adding a sintering additive into nanoscale silicon carbide powder, and screening a resulting mixture, in which the weight proportion of the sintering additive is 1% to 10%.

[0010] Further, the overcoated TRISO coated fuel particles are obtained by coating surfaces of TRISO coated fuel particles with silicon carbide powder layer, wherein the coated silicon carbide powder layer has a thickness of 10 to 100pm.

[0011] Further, the sintering additive is an oxide; and the method for uniformly mixing includes uniformly mixing the nanoscale silicon carbide powder and the sintering additive through a wet ball milling process with an organic solvent as a dispersant.

[0012] Further, the sintering additive is any one or more of alumina, yttria, gadolinia, erbia, or silicon oxide.

[0013] Further, the dispersant is alcohol and/or polyethylenimine.

[0014] Further, the method for uniformly mixing includes uniformly mixing the nanoscale silicon carbide powder and the sintering additive through a wet ball milling process with an organic solvent as a dispersant, in which the weight proportion of the dispersant is 0.5% to 5%.

[0015] Further, the silicon carbide powder layer is a mixture of the matrix material and a viscous organic solvent.

[0016] Further, the viscous organic solvent is polyethylene glycol and/or glycerol.

[0017] Further, the silicon carbide powder layer is a mixture of the matrix material and a viscous organic solvent, wherein the weight proportion of the viscous organic solvent is 0.5% to 5%.

[0018] Further, the chemical vapor deposition method is performed in a methyltrichlorosilane atmosphere, and the chemical vapor deposition method or the silicon carbide powder sintering process is performed at a temperature higher than 1600 C.

[0019] Further, the chemical vapor deposition method or the silicon carbide powder sintering process is performed at a temperature of 1600 C to 2000 C.

[0020] Further, for any two adjacent silicon carbide cylindrical bodies in the series of silicon carbide cylindrical bodies, one of the two silicon carbide cylindrical bodies is arranged around a periphery of the other.

[0021] Further, the series of silicon carbide cylindrical bodies are coaxially arranged, and radii of the series of silicon carbide cylindrical bodies form an arithmetic progression with a common difference equal to a diameter of the smallest silicon carbide cylindrical body.

[0022] Further, in the series of silicon carbide cylindrical bodies, the smallest silicon carbide cylindrical body has a diameter greater than the overcoated TRISO
coated fuel particles, and the largest silicon carbide cylindrical body has a radius equal to a cylindrical radius of the homogenized coated particle dispersed fuel.

[0023] Further, the series of silicon carbide cylindrical bodies each have a wall thickness less than 0.25mm.

[0024] Further, the series of silicon carbide cylindrical bodies have a wall thickness of 0.1mm to 0.25mm.

[0025] Further, the pressure sintering is performed at a temperature higher than 1600 C.

[0026] Further, the pressure sintering is performed at a temperature of 1600 C
to 2000 C.

[0027] The present disclosure further provides a process for manufacturing the homogenized coated particle dispersed fuel as described above. The method includes steps of:
(1) manufacturing a matrix material: adding a sintering additive into nanoscale silicon carbide powder, uniformly mixing the sintering additive and the nanoscale silicon carbide powder, and drying and screening a resulting mixture to obtain a matrix material for the coated particle dispersed fuel;
(2) manufacturing overcoated TRISO coated fuel particles: coating surfaces of TRISO coated fuel particles with a silicon carbide powder layer to obtain overcoated TRISO coated fuel particles;
(3) manufacturing a series of silicon carbide cylindrical bodies: performing a chemical vapor deposition method in a methyltrichlorosilane atmosphere or performing a silicon carbide powder sintering process to manufacture a series of silicon carbide cylindrical bodies, wherein the chemical vapor deposition method or the silicon carbide powder sintering process is performed at a temperature higher than 1600 C;
(4) filling and compacting a graphite mold: mounting the series of silicon carbide cylindrical bodies into annular grooves at the bottom of a graphite mold, uniformly mixing the overcoated TRISO coated fuel particles and the matrix material with agitation, filling a resulting mixed slurry into gap spaces formed by the series of silicon carbide cylindrical bodies and the graphite mold, and then compacting the gap spaces by a matching graphite indenter;
(5) pressure sintering: integrally feeding the graphite mold and the graphite indenter compacting the gap spaces in the step (4) into a sintering device, and performing pressure sintering at a temperature higher than 1600 C, wherein a pressure of the graphite indenter is maintained at 50 to lOOMPa during sintering, and the temperature is kept for 30 to 60min during sintering; and (6) demolding and machining to remove a portion of the series of silicon carbide cylindrical bodies exceeding a cylindrical base (cylindrical base of the manufactured fuel), to manufacture a cylindrical homogenized coated particle dispersed fuel.

[0028] Further, in the step (3), the chemical vapor deposition method or the silicon carbide powder sintering process is performed at a temperature of 1600 C to 2000 C.

[0029] Further, in the step (5), the pressure sintering is performed at a temperature of 1600 C to 2000 C.

[0030] Further, the sintering additive is an oxide.

[0031] Further, the silicon carbide powder layer is coated by spray-coating the surfaces of the TRISO coated fuel particles with a mixture of the matrix material and the viscous organic solvent, thereby forming the silicon carbide powder layer.

[0032] The present disclosure has the following beneficial effects: the homogenized coated particle dispersed fuel manufactured by the process for manufacturing a homogenized coated particle dispersed fuel of the present disclosure has all advantages of the coated particle dispersed fuel, which ensures the structural and chemical stability of the fuel under irradiation, high temperature and accident conditions, while the silicon carbide powder layer and the silicon carbide matrix material in the TRISO
coated fuel particles can block most gaseous and solid fission products. On this basis, the present disclosure further optimizes uniformity of the TRISO coated fuel particles in the fuel, especially achieves uniform radial distribution of the TRISO coated fuel particles, increases the accuracy of neutron physics and thermal calculation and analysis for the reactor core, while efficiently reducing: a radial temperature gradient of the fuel, a risk of damage to the TRISO coated fuel particles, and thus a risk of fission products release.
In addition, the reduced radial temperature gradient of the fuel can further reduce the likelihood of fuel core breakup of the coated particle dispersed fuel after long operation.
BRIEF DESCRIPTION OF DRAWINGS

[0033] FIG. 1 is a flowchart of a process for manufacturing a homogenized coated particle dispersed fuel according to the present disclosure.

[0034] FIG. 2 is a schematic diagram showing filling of a graphite mold according to the present disclosure.

[0035] FIG. 3 is a schematic diagram of a graphite indenter according to the present disclosure.

[0036] FIG. 4 is a schematic top view of a homogenized coated particle dispersed fuel according to the present disclosure.
DETAIL DESCRIPTION OF EMBODIMENTS

[0037] To enable those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure will be further described in conjunction with the accompanying drawings and the detailed description of embodiments.

[0038] The embodiments of the present invention will now be described in detail with the examples thereof shown in the drawings throughout which, the same or similar reference signs refer to the same elements or to similar elements with the same or similar functions. The embodiments described below with reference to the drawings are merely illustrative, and are used only for the purpose of explaining the present invention and should not be interpreted as limitations to the present invention.
Embodiment 1

[0039] An embodiment of the present disclosure provides a homogenized coated particle dispersed fuel, including a matrix material, overcoated TRISO coated fuel particles, and a series of silicon carbide cylindrical bodies; wherein:

[0040] the matrix material is manufactured by: adding A1203 as a sintering additive into nanoscale silicon carbide powder, in which a weight proportion of the sintering additive is 1%; uniformly mixing the sintering additive and the nanoscale silicon carbide power through a wet ball milling process with alcohol as a dispersant, in which the weight proportion of the dispersant is 2%; and then drying and screening a resulting mixture.

[0041] The overcoated TRISO coated fuel particles are obtained by coating surfaces of TRISO coated fuel particles each having a fuel kernel made of uranium dioxide with a silicon carbide powder layer, wherein the coated silicon carbide powder layer has a thickness of 50 m. As a buffer layer, the coated silicon carbide powder layer can prevent damage to outer layers of the TRISO coated fuel particles caused by collision of the TRISO coated fuel particles due to operations in the processing and manufacturing process. The silicon carbide powder layer is a mixture of the matrix material and a viscous organic solvent, in which the viscous organic solvent is polyethylene glycol, and the weight proportion of the viscous organic solvent is 2%.

[0042] The series of silicon carbide cylindrical bodies are manufactured through a chemical vapor deposition method at a temperature higher than 1600 C in a methyltrichlorosilane atmosphere. In one implementation, a deposition base face is formed by an outer surface of a cylindrical graphite mold, and a silicon carbide cylindrical body is manufactured through chemical vapor deposition in a methyltrichlorosilane atmosphere at a deposition temperature of 1800 C, thereby manufacturing a series of silicon carbide cylindrical bodies.

[0043] The homogenized coated particle dispersed fuel is manufactured by uniformly mixing the overcoated TRISO coated fuel particles and the matrix material with agitation, filling a resulting mixed slurry into gap spaces formed by the series of silicon carbide cylindrical bodies mounted in annular grooves at the bottom of a graphite mold and the graphite mold, and performing pressure sintering at a temperature higher than and then demolding. In one implementation, the pressure sintering is performed at a temperature of 1800 C.

[0044] In one implementation, in the homogenized coated particle dispersed fuel, the volume proportion of the matrix material is 50%, the volume proportion of the overcoated TRISO coated fuel particles is 42%, and the volume proportion of the series of silicon carbide cylindrical bodies is 8%.

[0045] In one implementation, for any two adjacent silicon carbide cylindrical bodies in the series of silicon carbide cylindrical bodies, one of the two silicon carbide cylindrical bodies is arranged around a periphery of the other. In this manner, uniform radial distribution of the TRISO coated fuel particles can be facilitated.

[0046] In one implementation, the series of silicon carbide cylindrical bodies are coaxially arranged, and radii of the manufactured series of silicon carbide cylindrical bodies form an arithmetic progression with a common difference equal to a diameter of the smallest silicon carbide cylindrical body. The smallest silicon carbide cylindrical body has a diameter slightly greater than the overcoated TRISO coated fuel particles, and the largest silicon carbide cylindrical body has a radius equal to a cylindrical radius of the homogenized coated particle dispersed fuel. In this manner, the overcoated TRISO
coated fuel particles are arranged at equal intervals in the radial direction.

[0047] Further, the series of silicon carbide cylindrical bodies each have a wall thickness less than 0.25mm.

[0048] In one implementation, the series of silicon carbide cylindrical bodies each have a wall thickness of 0.15mm to 0.2mm.

[0049] As shown in FIG. 1, this embodiment provides a process for manufacturing the homogenized coated particle dispersed fuel as described above, including:
(1) manufacturing a matrix material: adding A1203 as a sintering additive into nanoscale silicon carbide powder, uniformly mixing the sintering additive and the nanoscale silicon carbide powder through a wet ball milling process with alcohol as a dispersant, drying and screening a resulting mixture to obtain the matrix material for the coated particle dispersed fuel;
(2) manufacturing overcoated TRISO coated fuel particles: mixing the matrix material of the coated particle dispersed fuel with polyethylene glycol, and spray-coating the resulting mixture on surfaces of TRISO coated fuel particles to form a silicon carbide powder layer, thereby obtaining overcoated TRISO coated fuel particles;
(3) manufacturing a series of silicon carbide cylindrical bodies 1: performing a chemical vapor deposition method in a methyltrichlorosilane atmosphere with an outer surface of a cylindrical graphite mold as a deposition base face, thereby depositing in the methyltrichlorosilane atmosphere to obtain a silicon carbide cylindrical body, and manufacturing a series of silicon carbide cylindrical bodies 1 in this manner, wherein the chemical vapor deposition is performed at a temperature higher than 1600 C, in one implementation, the deposition temperature is 1800 C, so as to ensure quality of the series of silicon carbide cylindrical bodies 1. The radii of the manufactured series of silicon carbide cylindrical bodies 1 form an arithmetic progression, wherein a common difference of the arithmetic progression is equal to a diameter of the smallest silicon carbide cylindrical body; the smallest silicon carbide cylindrical body has a diameter slightly greater than the overcoated TRISO coated fuel particles, and the largest silicon carbide cylindrical body has a radius equal to a cylindrical radius of the homogenized coated particle dispersed fuel; and the series of silicon carbide cylindrical bodies 1 each have a wall thickness of 0.15mm to 0.2mm;
(4) filling and compacting a graphite mold: as shown in FIGs. 2, 3 and 4, mounting the series of silicon carbide cylindrical bodies 1 into annular grooves at the bottom of a graphite mold 3, uniformly mixing the overcoated TRISO coated fuel particles and the matrix material with agitation, filling a resulting mixed slurry 2 into gap spaces formed by the series of silicon carbide cylindrical bodies 1 and the graphite mold 3, and then compacting the gap spaces by a matching graphite indenter 4;
(5) pressure sintering: integrally feeding the graphite mold 3 and the graphite indenter 4 compacting the gap spaces in the step (4) into a sintering device for pressure sintering; wherein the pressure sintering is performed at a temperature higher than 1600 C, and in one implementation, at 1800 C; and the pressure of the graphite indenter 4 is maintained at 50MPa during sintering, and the temperature is kept for 60min during sintering; and (6) demolding and machining to remove a portion of the series of silicon carbide cylindrical bodies 1 exceeding a cylindrical base, to manufacture a cylindrical homogenized coated particle dispersed fuel.

[0050] Taking the performance of the fuel in the gas-cooled micro-reactor under a specific working condition, with the volume proportion of the TRISO particles being 40%, and the fuel having a size of (p20x30mm, as an example, a Keff value 1.029 is obtained by the homogenized coated particle dispersed fuel of this embodiment, while for a coated particle dispersed fuel with the TRISO fuel particles randomly distributed in the fuel under the same working condition (which may be referred to as conventional FCM fuel), the Keff value is 1.028, which means that the service life of the homogenized coated particle dispersed fuel is about 20 days longer; and compared with the conventional FCM fuel, a maximum temperature at fuel center of the homogenized coated particle dispersed fuel of this embodiment in the gas-cooled micro-reactor under a specific working condition is reduced from 1150 C to 1125 C, and the corresponding TRISO coated fuel particles' failure probability is reduced from 3.83 x10-6 to 2.08X
10-6.

[0051] The beneficial effects of this embodiment lie in that: the homogenized coated particle dispersed fuel manufactured by the process for manufacturing a homogenized coated particle dispersed fuel of this embodiment has all advantages of the coated particle dispersed fuel, which ensures the structural and chemical stability of the fuel under irradiation, high temperature and accident conditions, while the silicon carbide powder layer and the silicon carbide matrix material in the TRISO coated fuel particles can block most gaseous and solid fission products. On this basis, this embodiment further optimizes uniformity of the TRISO coated fuel particles in the fuel, especially achieves uniform radial distribution of the TRISO coated fuel particles, increases the accuracy of neutron physics and thermal calculation and analysis for the reactor core, while efficiently reducing: a radial temperature gradient of the fuel, a risk of damage to the TRISO coated fuel particles, and thus a risk of fission products release.
In addition, the reduced radial temperature gradient of the fuel can further reduce the likelihood of fuel core breakup of the coated particle dispersed fuel after long operation.
Embodiment 2

[0052] An embodiment of the present disclosure provides a homogenized coated particle dispersed fuel, including a matrix material, overcoated TRISO coated fuel particles, and a series of silicon carbide cylindrical bodies; wherein:
the matrix material is manufactured by: adding Y203 as a sintering additive into nanoscale silicon carbide powder, in which the weight proportion of the sintering additive is 3%; uniformly mixing the sintering additive and the nanoscale silicon carbide power through a wet ball milling process with alcohol as a dispersant, in which the weight proportion of the dispersant is 0.5%; and then drying and screening a resulting mixture.

[0053] The overcoated TRISO coated fuel particles are obtained by coating surfaces of TRISO coated fuel particles each having a fuel kernel made of uranium dioxide with a silicon carbide powder layer, wherein the coated silicon carbide powder layer has a thickness of lOpm. As a buffer layer, the coated silicon carbide powder layer can prevent damage to outer layers of the TRISO coated fuel particles caused by collision of the TRISO coated fuel particles due to operations in the processing and manufacturing process. The silicon carbide powder layer is a mixture of the matrix material and a viscous organic solvent, wherein the viscous organic solvent is glycerol, and the weight proportion of the viscous organic solvent is 0.5%.

[0054] The series of silicon carbide cylindrical bodies are manufactured through a silicon carbide powder sintering process at a temperature higher than 1600 C.
Specifically, in this embodiment, the silicon carbide powder is mixed with a sintering additive, and subjected to high-temperature pressure sintering at 2000 C in a graphite sintering mold for silicon carbide cylindrical body, thereby manufacturing a series of silicon carbide cylindrical bodies.

[0055] The homogenized coated particle dispersed fuel is manufactured by uniformly mixing the overcoated TRISO coated fuel particles and the matrix material with agitation, filling a resulting mixed slurry into gap spaces formed by the series of silicon carbide cylindrical bodies mounted in annular grooves at a bottom of a graphite mold and the graphite mold, and performing pressure sintering at a temperature higher than and then demolding. In one implementation, the pressure sintering is performed at a temperature of 2000 C.

[0056] In one implementation, in the homogenized coated particle dispersed fuel, the volume proportion of the matrix material is 65%, the volume proportion of the overcoated TRISO coated fuel particles is 10%, and the volume proportion of the series of silicon carbide cylindrical bodies is 25%.

[0057] In one implementation, for any two adjacent silicon carbide cylindrical bodies in the series of silicon carbide cylindrical bodies, one of the two silicon carbide cylindrical bodies is arranged around a periphery of the other. In this manner, uniform radial distribution of the TRISO coated fuel particles can be facilitated.

[0058] In one implementation, the series of silicon carbide cylindrical bodies are coaxially arranged, and radii of the manufactured series of silicon carbide cylindrical bodies form an arithmetic progression with a common difference equal to a diameter of the smallest silicon carbide cylindrical body. The smallest silicon carbide cylindrical body has a diameter slightly greater than the overcoated TRISO coated fuel particles, and the largest silicon carbide cylindrical body has a radius equal to a cylindrical radius of the homogenized coated particle dispersed fuel. In this manner, the overcoated TRISO
coated fuel particles are arranged at equal intervals in the radial direction.

[0059] Further, the series of silicon carbide cylindrical bodies each have a wall thickness less than 0.25mm.

[0060] In one implementation, the series of silicon carbide cylindrical bodies each have a wall thickness of 0.1mm to 0.15mm.

[0061] As shown in FIG. 1, this embodiment provides a process for manufacturing the homogenized coated particle dispersed fuel as described above, including:
(1) manufacturing a matrix material: adding Y203 as a sintering additive into nanoscale silicon carbide powder, uniformly mixing the sintering additive and the nanoscale silicon carbide powder through a wet ball milling process with alcohol as a dispersant, drying and screening a resulting mixture to obtain the matrix material for the coated particle dispersed fuel;
(2) manufacturing overcoated TRISO coated fuel particles: mixing the matrix material of the coated particle dispersed fuel with glycerol, and spray-coating the resulting mixture on surfaces of TRISO coated fuel particles to form a silicon carbide powder layer, to obtain overcoated TRISO coated fuel particles;
(3) manufacturing a series of silicon carbide cylindrical bodies 1:
performing, on a mixture of silicon carbide powder and sintering additive in a graphite sintering mold for silicon carbide cylindrical body, a silicon carbide powder sintering process at a temperature higher than 1600 C, in one implementation performing high-temperature pressure sintering at a temperature of 2000 C, thereby manufacturing a series of silicon carbide cylindrical bodies 1, and the quality of the series of silicon carbide cylindrical bodies is ensured. The radii of the manufactured series of silicon carbide cylindrical bodies 1 form an arithmetic progression, wherein a common difference of the arithmetic progression is equal to a diameter of the smallest silicon carbide cylindrical body; the smallest silicon carbide cylindrical body has a diameter slightly greater than the overcoated TRISO coated fuel particles, and the largest silicon carbide cylindrical body has a radius equal to a cylindrical radius of the homogenized coated particle dispersed fuel; and the series of silicon carbide cylindrical bodies 1 each have a wall thickness of 0.1mm to 0.15mm;
(4) filling and compacting a graphite mold: as shown in FIGs. 2, 3 and 4, mounting the series of silicon carbide cylindrical bodies 1 into annular grooves at a bottom of a graphite mold 3, manufactured by uniformly mixing the overcoated TRISO
coated fuel particles and the matrix material with agitation, filling a resulting mixed slurry 2 into gap spaces formed by the series of silicon carbide cylindrical bodies 1 and the graphite mold 3, and then compacting the gap spaces by a matching graphite indenter 4;
(5) pressure sintering: integrally feeding the graphite mold 3 and the graphite indenter 4 compacting the gap spaces in the step (4) into a sintering device for pressure sintering; wherein the pressure sintering is performed at a temperature higher than 1600 C, and in one implementation, at 2000 C; the pressure of the graphite indenter 4 is maintained at 100M Pa during sintering, and the temperature is kept for 30min during sintering; and (6) demolding and machining to remove a portion of the series of silicon carbide cylindrical bodies 1 exceeding a cylindrical base, to manufacture a cylindrical homogenized coated particle dispersed fuel.

[0062] Taking the performance of the fuel in the gas-cooled micro-reactor under a specific working condition, with the volume proportion of the TRISO particles being 10% and the fuel having a size of (p20x30mm, as an example, a Keff value 1.013 is obtained by the homogenized coated particle dispersed fuel of this embodiment, while for a coated particle dispersed fuel with the TRISO fuel particles randomly distributed in the fuel under the same working condition (which may be referred to as conventional FCM fuel), the Keff value is 1.009, which means that the service life of the homogenized coated particle dispersed fuel is about 90 days longer; and compared with the conventional FCM fuel, a maximum temperature at fuel center of the homogenized coated particle dispersed fuel of this embodiment in the gas-cooled micro-reactor under a specific working condition is reduced from 800 C to 755 C, and the corresponding TRISO coated fuel particles' failure probability is reduced from 7.57 X10" to 1.03X
1011.
Embodiment 3

[0063] An embodiment of the present disclosure provides a homogenized coated particle dispersed fuel, which differs from the embodiment 1 in that:

[0064] In this embodiment, the matrix material is manufactured by: adding gadolinia as a sintering additive into nanoscale silicon carbide powder, in which the weight proportion of the sintering additive is 4%; uniformly mixing the sintering additive and the nanoscale silicon carbide power through a wet ball milling process with polyethylenimine as a dispersant, in which the weight proportion of the dispersant is 5%;
and then drying and screening a resulting mixture.

[0065] In this embodiment, the overcoated TRISO coated fuel particles are obtained by coating surfaces of TRISO coated fuel particles each having a fuel kernel made of uranium dioxide with a silicon carbide powder layer, wherein the coated silicon carbide powder layer has a thickness of 100pm. The silicon carbide powder layer is a mixture of the matrix material and a viscous organic solvent, wherein the viscous organic solvent is polyethylene glycol, and the weight proportion of the viscous organic solvent is 5%.

[0066] In this embodiment, the chemical vapor deposition method is performed at a deposition temperature of 1650 C.

[0067] In this embodiment, the pressure sintering is performed at a temperature of 1650 C.

[0068] In this embodiment, the volume proportion of the matrix material is 58%, the volume proportion of the overcoated TRISO coated fuel particles is 21%, and the volume proportion of the series of silicon carbide cylindrical bodies is 21%.

[0069] In this embodiment, the series of silicon carbide cylindrical bodies each have a wall thickness of 0.1mm to 0.2mm.

[0070] This embodiment provides a process for manufacturing the homogenized coated particle dispersed fuel as described above, which differs from the embodiment 1 in that:

[0071] In this embodiment, the chemical vapor deposition method is performed at a deposition temperature of 1650 C.

[0072] In this embodiment, the pressure sintering is performed at a temperature of 1650 C, the pressure of the graphite indenter 4 is maintained at 60M Pa during sintering, and the temperature is kept for 40min during sintering.

[0073] Taking the performance of the fuel in the gas-cooled micro-reactor under a specific working condition, with the volume proportion of the TRISO particles being 20% and the fuel having a size of tp20x30mm, as an example, a Keff value 1.019 is obtained by the homogenized coated particle dispersed fuel of this embodiment, while for a coated particle dispersed fuel with the TRISO fuel particles randomly distributed in the fuel under the same working condition (which may be referred to as conventional FCM fuel), the Keff value is 1.016, which means that the service life of the homogenized coated particle dispersed fuel is about 65 days longer; and compared with the conventional FCM fuel, a maximum temperature at fuel center of the homogenized coated particle dispersed fuel of this embodiment in the gas-cooled micro-reactor under a specific working condition is reduced from 960 C to 925 C, and the corresponding TRISO coated fuel particles' failure probability is reduced from 6.74 x10-9 to 1.26X
10-g.
Embodiment 4

[0074] An embodiment of the present disclosure provides a homogenized coated particle dispersed fuel, which differs from the embodiment 1 in that:

[0075] In this embodiment, the matrix material is manufactured by: adding erbia and alumina of a weight ratio 1:1 as sintering additives into nanoscale silicon carbide powder, in which the weight proportion of the sintering additives is 2%; uniformly mixing the sintering additives and the nanoscale silicon carbide power through a wet ball milling process with alcohol as a dispersant, in which the weight proportion of the dispersant is 3%; and then drying and screening a resulting mixture.

[0076] In this embodiment, the overcoated TRISO coated fuel particles are obtained by coating surfaces of TRISO coated fuel particles each having a fuel kernel made of uranium dioxide with a silicon carbide powder layer, wherein the coated silicon carbide powder layer has a thickness of 40 m. The silicon carbide powder layer is a mixture of the matrix material and a viscous organic solvent, wherein the viscous organic solvent is polyethylene glycol, and the weight proportion of the viscous organic solvent is 3%.

[0077] In this embodiment, the chemical vapor deposition method is performed at a deposition temperature of 1700 C.

[0078] In this embodiment, the pressure sintering is performed at a temperature of 1700 C.

[0079] In this embodiment, the volume proportion of the matrix material is 60%, the volume proportion of the overcoated TRISO coated fuel particles is 30%, and the volume proportion of the series of silicon carbide cylindrical bodies is 10%.

[0080] In this embodiment, the series of silicon carbide cylindrical bodies each have a wall thickness of 0.2mm to 0.25mm.

[0081] This embodiment provides a process for manufacturing the homogenized coated particle dispersed fuel as described above, which differs from the embodiment 1 in that:

[0082] In this embodiment, the chemical vapor deposition method is performed at a deposition temperature of 1700 C.

[0083] In this embodiment, the pressure sintering is performed at a temperature of 1700 C, the pressure of the graphite indenter 4 is maintained at 70M Pa during sintering, and the temperature is kept for 50min during sintering.

[0084] Taking the performance of the fuel in the gas-cooled micro-reactor under a specific working condition, with the volume proportion of the TRISO particles being 30% and the fuel having a size of tp20x30mm, as an example, a Keff value 1.023 is obtained by the homogenized coated particle dispersed fuel of the embodiment, while for a coated particle dispersed fuel with the TRISO fuel particles randomly distributed in the fuel under the same working condition (which may be referred to as conventional FCM
fuel), the Keff value is 1.021, which means that the service life of the homogenized coated particle dispersed fuel is about 40 days longer; and compared with the conventional FCM fuel, a maximum temperature at fuel center of the homogenized coated particle dispersed fuel of this embodiment in the gas-cooled micro-reactor under a specific working condition is reduced from 1090 C to 1060 C, and the corresponding TRISO coated fuel particles' failure probability is reduced from 1.64 x10-7 to 4.83X
10-8.
Embodiment 5

[0085] An embodiment of the present disclosure provides a homogenized coated particle dispersed fuel, which differs from the embodiment 1 in that:

[0086] In this embodiment, the matrix material is manufactured by: adding alumina and silicon oxide with a weight ratio 3:2 as sintering additives into nanoscale silicon carbide powder, in which the weight proportion of the sintering additives is 10%;
uniformly mixing the sintering additives and the nanoscale silicon carbide power through a wet ball milling process with alcohol and polyethylenimine of a weight ratio 1:2 as dispersants, in which the weight proportion of the dispersants is 4%; and then drying and screening a resulting mixture.

[0087] In this embodiment, the overcoated TRISO coated fuel particles are obtained by coating surfaces of TRISO coated fuel particles each having a fuel kernel made of uranium dioxide with a silicon carbide powder layer, wherein the coated silicon carbide powder layer has a thickness of 60 m. The silicon carbide powder layer is a mixture of the matrix material and a viscous organic solvent, in which the viscous organic solvent is polyethylene glycol and glycerol of a weight ratio 2:1, and in which the weight proportion of the viscous organic solvent is 4%.

[0088] In this embodiment, the chemical vapor deposition method is performed at a deposition temperature of 1900 C.

[0089] In this embodiment, the pressure sintering is performed at a temperature of 1900 C.

[0090] In this embodiment, the volume proportion of the matrix material is 55%, the volume proportion of the overcoated TRISO coated fuel particles is 32%, and the volume proportion of the series of silicon carbide cylindrical bodies is 13%.

[0091] In this embodiment, the series of silicon carbide cylindrical bodies each have a wall thickness of 0.15mm to 0.2mm.

[0092] This embodiment provides a process for manufacturing the homogenized coated particle dispersed fuel as described above, which differs from the embodiment 1 in that:

[0093] In this embodiment, the chemical vapor deposition method is performed at a deposition temperature of 1900 C.

[0094] In this embodiment, the pressure sintering is performed at a temperature of 1900 C, the pressure of the graphite indenter 4 is maintained at 80MPa during sintering, and the temperature is kept for 45min during sintering.

[0095] Taking the performance of the fuel in the gas-cooled micro-reactor under a specific working condition, with the volume proportion of the TRISO particles being 30% and the fuel having a size of (p20x30mm, as an example, a Keff value 1.023 is obtained by the homogenized coated particle dispersed fuel of the embodiment, while for a coated particle dispersed fuel with the TRISO fuel particles randomly distributed in the fuel under the same working condition (which may be referred to as conventional FCM
fuel), the Keff value is 1.021, which means that the service life of the homogenized coated particle dispersed fuel is about 40 days longer; and compared with the conventional FCM fuel, a maximum temperature at fuel center of the homogenized coated particle dispersed fuel of this embodiment in the gas-cooled micro-reactor under a specific working condition is reduced from 1090 C to 1060 C, and the corresponding TRISO coated fuel particles' failure probability is reduced from 1.64 x10-7 to 4.83X
10-8.

[0096] The above embodiments are merely illustrative of the present disclosure, and various changes and variations may be made to the present disclosure by those skilled in the art without departing from the spirit and scope of the present disclosure.
Thus, if such modifications and variations to the present disclosure are within the scope of the claims of the present disclosure and their equivalents, the present disclosure is also intended to encompass such modifications and variations.

Claims (25)

What is claimed is:

1. A homogenized coated particle dispersed fuel, comprising a matrix material, overcoated TRISO coated fuel particles, and a series of silicon carbide cylindrical bodies; wherein :
the matrix material is manufactured by adding a sintering additive into nanoscale silicon carbide powder, uniformly mixing the sintering additive and the nanoscale silicon carbide powder, and drying and screening a resulting mixture;
the overcoated TRISO coated fuel particles are obtained by coating surfaces of TRISO coated fuel particles with a silicon carbide powder layer;
the series of silicon carbide cylindrical bodies are manufactured through a chemical vapor deposition method or a silicon carbide powder sintering process; and the homogenized coated particle dispersed fuel is manufactured by uniformly mixing the overcoated TRISO coated fuel particles and the matrix material with agitation, filling a resulting mixed slurry into gap spaces formed by the series of silicon carbide cylindrical bodies mounted in annular grooves at a bottom of a graphite mold and the graphite mold, and then performing pressure sintering.

2. The homogenized coated particle dispersed fuel according to claim 1, wherein in the homogenized coated particle dispersed fuel, a volume proportion of the matrix material is 50% to 65%, a volume proportion of the overcoated TRISO

coated fuel particles is 10% to 42%, and a volume proportion of the series of silicon carbide cylindrical bodies is 8% to 25%.

3. The homogenized coated particle dispersed fuel according to claim 1, wherein the matrix material is manufactured by adding a sintering additive into nanoscale silicon carbide powder, and screening a resulting mixture, in which a weight proportion of the sintering additive in the matrix material is 1% to 10%.

4. The homogenized coated particle dispersed fuel according to claim 1, wherein the overcoated TRISO coated fuel particles are obtained by coating surfaces of TRISO coated fuel particles with a silicon carbide powder layer, wherein the coated silicon carbide powder layer has a thickness of 10 to 100pm.

5. The homogenized coated particle dispersed fuel according to claim 1, wherein the sintering additive is an oxide, and the method for uniformly mixing comprises uniformly mixing the nanoscale silicon carbide powder and the sintering additive through a wet ball milling process with an organic solvent as a dispersant.

6. The homogenized coated particle dispersed fuel according to claim 5, wherein the sintering additive is any one or more of alumina, yttria, gadolinia, erbia, or silicon oxide.

7. The homogenized coated particle dispersed fuel according to claim 5, wherein the dispersant is alcohol and/or polyethylenimine.

8. The homogenized coated particle dispersed fuel according to claim 5, wherein the method for uniformly mixing comprises uniformly mixing the nanoscale silicon carbide powder and the sintering additive through a wet ball milling process with an organic solvent as a dispersant, in which a weight proportion of the dispersant is O. 5% to 5%.

9. The homogenized coated particle dispersed fuel according to claim 1, wherein the silicon carbide powder layer is a mixture of the matrix material and a viscous organic solvent.

10. The homogenized coated particle dispersed fuel according to claim 9, wherein the viscous organic solvent is polyethylene glycol and/or glycerol.

11. The homogenized coated particle dispersed fuel according to claim 9, wherein the silicon carbide powder layer is a mixture of the matrix material and a viscous organic solvent, in which a weight proportion of the viscous organic solvent is 0. 5% to 5%.

12. The homogenized coated particle dispersed fuel according to claim 1, wherein the chemical vapor deposition method is performed in a methyltrichlorosilane atmosphere, and the chemical vapor deposition method or the silicon carbide powder sintering process is performed at a temperature higher than 1600 C.

13. The homogenized coated particle dispersed fuel according to claim 12, wherein the chemical vapor deposition method or the silicon carbide powder sintering process is performed at a temperature of 1600 C to 2000 C.

14. The homogenized coated particle dispersed fuel according to claim 1, wherein for any two adjacent silicon carbide cylindrical bodies in the series of silicon carbide cylindrical bodies, one of the two silicon carbide cylindrical bodies is arranged around a periphery of the other.

15. The homogenized coated particle dispersed fuel according to claim 14, wherein the series of silicon carbide cylindrical bodies are coaxially arranged, and radii of the series of silicon carbide cylindrical bodies form an arithmetic progression with a common difference equal to a diameter of the smallest silicon carbide cylindrical body.

16. The homogenized coated particle dispersed fuel according to claim 1, wherein the smallest silicon carbide cylindrical body has a diameter greater than that of the overcoated TRISO coated fuel particles, and the largest silicon carbide cylindrical body has a radius equal to a cylindrical radius of the homogenized coated particle dispersed fuel.

17. The homogenized coated particle dispersed fuel according to claim 1, wherein the series of silicon carbide cylindrical bodies each have a wall thickness less than O. 25mm.

18. The homogenized coated particle dispersed fuel according to claim 17, wherein the series of silicon carbide cylindrical bodies each have a wall thickness of 0.1mm to 0.25mm.

19. The homogenized coated particle dispersed fuel according to claim 1, wherein the pressure sintering is performed at a temperature higher than 1600 C.

20. The homogenized coated particle dispersed fuel according to claim 19, wherein the pressure sintering is performed at a temperature of 1600 C to 2000 C.

21. A process for manufacturing a homogenized coated particle dispersed fuel according to any one of claims 1 to 20, wherein the method comprises steps of:
(1) manufacturing a matrix material: adding a sintering additive into nanoscale silicon carbide powder, uniformly mixing the sintering additive and the nanoscale silicon carbide powder, and drying and screening a resulting mixture to obtain a matrix material for the coated particle dispersed fuel;
(2) manufacturing overcoated TRISO coated fuel particles: coating surfaces of TRISO coated fuel particles with a silicon carbide powder layer to obtain overcoated TRISO coated fuel particles;
(3) manufacturing a series of silicon carbide cylindrical bodies: performing a chemical vapor deposition method in a methyltrichlorosilane atmosphere or performing a silicon carbide powder sintering process to manufacture a series of silicon carbide cylindrical bodies, wherein the chemical vapor deposition method or the silicon carbide powder sintering process is performed at a temperature higher than 1600 C;
(4) filling and compacting a graphite mold: mounting the series of silicon carbide cylindrical bodies into annular grooves at a bottom of a graphite mold, uniformly mixing the overcoated TRISO coated fuel particles and the matrix material with agitation, filling a resulting mixed slurry into gap spaces formed by the series of silicon carbide cylindrical bodies and the graphite mold, and then compacting the gap spaces by a matching graphite indenter;
(5) pressure sintering: integrally feeding the graphite mold and the graphite indenter compacting the gap spaces in the step (4) into a sintering device, and performing pressure sintering at a temperature higher than 1600 C, wherein a pressure of the graphite indenter is maintained at 50 to 100MPa during sintering, and the temperature is kept for 30 to 60min during the sintering; and (6) demolding and machining to remove a portion of the series of silicon carbide cylindrical bodies exceeding a cylindrical base, to manufacture a cylindrical homogenized coated particle dispersed fuel.

22. The process for manufacturing a homogenized coated particle dispersed fuel according to claim 21, wherein in the step (3), the chemical vapor deposition method or the silicon carbide powder sintering process is performed at a temperature of 1600 C to 2000 C.

23. The process for manufacturing a homogenized coated particle dispersed fuel according to claim 21, wherein in the step (5), the pressure sintering is performed at a temperature of 1600 C to 2000 C.

24. The process for manufacturing a homogenized coated particle dispersed fuel according to claim 21, wherein the sintering additive is an oxide.

25. The process for manufacturing a homogenized coated particle dispersed fuel according to claim 21, wherein the silicon carbide powder layer is coated by spray-coating the surfaces of the TRISO coated fuel particles with a mixture of the matrix material and a viscous organic solvent, thereby forming the silicon carbide powder layer.