A method of manufacturing triso fuel pellets and fuel pellets

Abstract

The application discloses a TRISO fuel pellet manufacturing method and a fuel pellet, and belongs to the nuclear power field. The TRISO fuel pellet manufacturing method comprises the following steps: laying a graphite powder layer in a fuel pellet mold; compacting the graphite powder layer by using a semispherical working part with a protrusion to form a positioning hole; loading a fuel ball into the positioning hole and covering the graphite powder layer; repeating the steps of compacting to form the positioning hole and loading the fuel ball until the graphite powder body reaches a preset height; and sintering after overall compaction to obtain the TRISO fuel pellet. The method can improve the uniformity of the TRISO fuel pellet and is convenient for large-scale continuous production.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power, specifically relating to a method for manufacturing TRISO fuel pellets and the fuel pellets themselves. Background Technology

[0002] Currently, TRISO (tristructural-isotropic) fuel is widely used in high-temperature gas-cooled reactor (HTGR) and other advanced nuclear reactor designs due to its excellent safety performance. In the design of heat pipe microreactors, excellent reactor safety and mobility are often required, thus placing high demands on fuel safety, making TRISO-based fuel pellets ideally suited for use.

[0003] In the prior art, TRISO fuel particles are usually randomly dispersed in the graphite matrix, which may lead to uneven local fuel density, thereby affecting fuel performance and the overall thermal characteristics of the reactor core.

[0004] Patent CN116417166A discloses a method for manufacturing dispersed fuel pellets. This method utilizes a vacuum adsorption device to implant fuel microspheres layer by layer into the matrix powder of the fuel pellet, achieving a uniform distribution of the fuel microspheres within the pellet. After pressing and molding, the pellets are sintered to form the finished dispersed fuel pellets. This method can control the position of the fuel microspheres in each layer using the vacuum adsorption device and adjust the longitudinal distribution of the fuel microspheres by adjusting the thickness of the matrix powder layers. However, the vacuum adsorption device inevitably draws in matrix powder during the implantation of fuel microspheres, leading to uneven distribution of the matrix powder and contamination of the vacuum adsorption system, thus affecting production efficiency.

[0005] Therefore, providing a more efficient method for manufacturing TRISO fuel pellets is of positive significance for improving production efficiency and optimizing economics. Summary of the Invention

[0006] The purpose of this invention is to provide a method for manufacturing TRISO fuel pellets, thereby improving the continuous production efficiency of TRISO fuel pellets. This invention also provides a fuel pellet.

[0007] According to one aspect of the present invention, a method for manufacturing TRISO fuel pellets is provided for manufacturing TRISO fuel pellets composed of a graphite matrix and fuel spheres.

[0008] The method specifically includes the following steps:

[0009] Step a): Provide a fuel pellet mold, and lay a layer of graphite powder inside the fuel pellet mold;

[0010] Step b): Provide a puncture mold, the puncture mold having a puncture working surface, the puncture working surface being provided with a raised hemispherical working part; use the puncture mold to compact the graphite powder layer and make the hemispherical working part form a positioning hole in the graphite powder layer;

[0011] Step c): Insert the fuel ball into the positioning hole and cover the fuel ball with a layer of graphite powder;

[0012] Step d): The graphite powder layer laid in step c) is compacted using the pressing mold, and the hemispherical working part forms a positioning hole in the graphite powder layer;

[0013] Step e): Repeat steps c) and d) until the graphite powder reaches the preset thickness, compact the graphite powder and sinter it to obtain TRISO fuel pellets.

[0014] This method achieves layer-by-layer positioning of fuel balls by forming positioning holes in the compacted graphite powder layer, eliminating the need for a vacuum adsorption device and effectively avoiding contamination caused by graphite powder mixed into the vacuum adsorption device. At the same time, the positioning holes can limit the position of the fuel balls, preventing uneven distribution of fuel balls caused by deviation in the position of the fuel balls when the graphite powder is further spread.

[0015] Furthermore, in some embodiments, two puncture molds are configured, and when the two puncture molds are arranged coaxially, the projected positions of their respective hemispherical working parts are staggered.

[0016] Adjacent graphite powder layers are compacted using different denting dies.

[0017] Using different denting dies can stagger the positions of fuel balls between adjacent layers, preventing the fuel balls from being squeezed and broken during compaction, and can also increase the density of the fuel balls.

[0018] Furthermore, in some embodiments, when the graphite powder layer is laid, the thickness of the compacted graphite powder layer is not less than the diameter of the fuel ball.

[0019] Furthermore, in some embodiments, the method for loading the fuel balls into the positioning holes is as follows: the same number of fuel balls as the positioning holes are sprinkled on the graphite powder layer in which the positioning holes are formed, and the fuel balls are made to fall into the positioning holes by vibration.

[0020] Furthermore, in some embodiments, the method also provides a filling mold having filling holes that correspond one-to-one with the positioning holes and allow the fuel ball to be engaged in the filling holes;

[0021] The method for inserting the fuel ball into the positioning hole is as follows:

[0022] The fuel ball is inserted into the filling hole of the filling mold, and the fuel ball is fed into the positioning hole through the filling mold.

[0023] Furthermore, in some embodiments, the fuel pellet mold used in this method is provided with a lifting mechanism at its bottom, and the method for loading the fuel pellets into the positioning holes is as follows:

[0024] No fewer than the number of fuel balls in the positioning holes are spread on the graphite powder layer with the positioning holes. Vibration is used to ensure that each fuel ball falls into the positioning hole. The compacted graphite powder blank is lifted to the top of the fuel pellet mold using a lifting mechanism, so that the fuel balls that do not fall into the positioning holes roll away from the graphite powder layer.

[0025] Furthermore, in some embodiments, the hemispherical working part has the same radius as the fuel ball.

[0026] Furthermore, in some embodiments, the radius of the positioning hole is 0.8mm-1.0mm.

[0027] According to another aspect of the present invention, a fuel pellet is provided, the fuel pellet comprising a graphite matrix and fuel spheres, and employing the TRISO fuel pellet manufacturing method provided in any of the foregoing embodiments. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the puncture mold structure in one embodiment;

[0029] Figure 2 This is a schematic diagram of the fuel ball positioning process in one embodiment.

[0030] Meaning of the reference numerals in the attached figures:

[0031] 1-Pressing die;

[0032] 2- Hemispherical working part;

[0033] 3-Fuel Balls;

[0034] 4-Graphite powder layer;

[0035] 5-Positioning hole.

[0036] The purpose of the above-described drawings is to provide a detailed description of the present invention so that those skilled in the art can understand the technical concept of the invention, and not to limit the invention. For the sake of brevity, the above-described drawings only schematically depict the structures related to the technical features of the present invention, and do not depict the complete structure and all details strictly according to actual scale. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0038] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment herein. The phrase appearing in various places in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive, independent, or alternative embodiments. Those skilled in the art will understand that the embodiments herein can be combined with other embodiments without causing structural conflicts.

[0039] In this description, unless otherwise explicitly specified and limited, the technical terms "installation," "connection," "joining," etc., should be interpreted broadly, for example, referring to movable connections, fixed connections, or integration. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0040] In this description, terms such as "upper," "lower," "left," "right," "lateral," "longitudinal," "height," "length," and "width," which indicate orientation or positional relationships, are intended to accurately describe the embodiments and simplify the description, rather than limiting the parts or structures involved to have a specific orientation, or to be installed or operated in a specific orientation, and should not be construed as limiting the embodiments in this document.

[0041] In this document, terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating relative importance or limiting the number, specific order, or primary / secondary relationship of the described technical features. In this document, "multiple" means at least two.

[0042] To address the issue of uneven fuel particle distribution in TRISO fuel and to achieve continuous and efficient production of TRISO fuel pellets, one embodiment of the present invention provides a TRISO fuel pellet manufacturing method that ensures uniform fuel particle distribution in TRISO fuel pellets, improves the thermal conductivity and radiation resistance of the fuel pellets, and is suitable for large-scale continuous production.

[0043] This method uses graphite powder and spherical fuel particles as raw materials and includes the following steps:

[0044] Step a): Provide a fuel pellet mold for pressing fuel pellets into shape, and lay a layer of graphite powder inside the fuel pellet mold.

[0045] Step b): Provide, for example Figure 2The puncture mold 1 is shown. The internal dimensions of the puncture mold match those of the fuel pellet mold, and the puncture mold 1, when used in conjunction with the fuel pellet mold, can fully compact the graphite powder within the fuel pellet mold. The puncture mold 1 has a working surface for compacting the graphite powder, and a protruding hemispherical working part 2 is provided on the working surface, combined with... Figure 2 During the process of compacting the graphite powder layer 4, the hemispherical working part 2 can form positioning holes 5 in the graphite powder layer 4.

[0046] Step c): Insert the fuel ball 3 into the positioning hole and continue to cover the fuel ball 3 completely with a layer of graphite powder.

[0047] Step d): Use the puncture mold 1 to continue compacting the graphite powder layer laid in step c) and forming positioning holes 5.

[0048] Step e): Repeat steps c) and d) until the graphite powder reaches the predetermined thickness, fully compact the graphite powder and sinter it to obtain TRISO fuel pellets.

[0049] In a preferred embodiment, two puncture dies 1 are configured, and when the two puncture dies 1 are arranged coaxially, the projected positions of their respective hemispherical working parts 2 are staggered. During the pellet manufacturing process, the two puncture dies 1 are used alternately. In this way, the positions of the fuel balls 3 in adjacent layers are staggered in the thickness direction, avoiding direct contact and crushing of the fuel balls 3 during the compaction process. In a further preferred embodiment, the fuel balls 3 are arranged in a roughly body-centered cubic or face-centered cubic manner within the graphite powder to further improve the effective fuel density in the TRISO fuel pellet.

[0050] In different embodiments, the fuel ball 3 can be inserted into the positioning hole 5 in different ways.

[0051] In some preferred embodiments, after the graphite powder layer 4 is compacted and the positioning holes 5 are formed, the same number of fuel balls 3 as the positioning holes 5 are sprinkled on the graphite powder layer 4, and the fuel balls 3 are naturally dropped into the positioning holes 5 by vibration.

[0052] In some preferred embodiments, fuel balls 3 are loaded into positioning holes 5 on the graphite powder layer 4 using a filling mold. Specifically, the filling mold is provided with filling holes, and the filling mold is manufactured according to the structural design of the pressing mold so that the filling holes and positioning holes 5 are aligned and correspond one-to-one. The filling holes and fuel balls 3 are similar in size, allowing the fuel balls 3 to be snapped into the filling holes. In this way, fuel balls 3 are loaded into each filling hole of the filling mold, and the fuel balls 3 are fed into the fuel pellet mold using the filling mold. The fuel balls 3 are then discharged to be loaded into the positioning holes 5 corresponding to the filling holes, thus completing the setting of the fuel balls 3. In different embodiments, different methods can be used to discharge the fuel balls 3 from the filling holes: for example, in some embodiments, a mechanical device can be used to push the fuel balls 3 out of the filling holes; in other embodiments, an air blowing device can be used to blow the fuel balls 3 out of the filling holes using air pressure.

[0053] In some preferred embodiments, a lifting mechanism is provided at the bottom of the fuel pellet mold, which can lift the compacted graphite powder to the top of the fuel pellet mold. In this embodiment, after the graphite powder layer 4 is compacted, a number of fuel balls 3, no less than the number of positioning holes 5, are inserted into the fuel pellet mold, and vibration is used to ensure that each positioning hole 5 contains a fuel ball 3. Subsequently, the compacted graphite powder is lifted by the lifting mechanism so that the upper surface of the graphite powder layer 4 is not lower than the top edge of the fuel pellet mold. Finally, by means of blowing or other methods, excess fuel balls that have not fallen into the positioning holes 5 are rolled off the surface of the graphite powder layer 4, completing the arrangement of the fuel balls 3.

[0054] In a preferred embodiment, the radius of the hemispherical working part 2 is the same as that of the fuel ball 3, so that the size of the formed positioning hole 5 matches that of the fuel ball 3. Further, the positioning hole 5 and the fuel ball 3 are both set to a radius of 0.9 mm.

[0055] In a preferred embodiment, to prevent the fuel balls 3 from contacting each other and crushing during compaction, the thickness of the compacted graphite powder layer 4 should not be less than the diameter of the fuel balls 3. Specifically, the thickness of the graphite powder layer 4 under different pressures can be determined through experimental testing to determine the amount of graphite powder in each graphite powder layer 4.

[0056] The method provided in the above embodiments can manufacture TRISO fuel pellets with uniform fuel particle distribution, which is suitable for reactors such as heat pipe microreactors that have high requirements for fuel safety.

[0057] The TRISO fuel pellet manufacturing method provided in the above embodiments can improve the uniformity of fuel particle distribution within the TRISO fuel pellet, enhance the thermal conductivity and radiation resistance of the fuel pellet, and improve the reliability of the fuel pellet. Simultaneously, it reduces the risk of TRISO particles being exposed on the surface during the manufacturing process of randomly mixing and sintering fuel particles with matrix powder, eliminating the need for a step to prepare a fuel-free surface area.

[0058] The purpose of the above embodiments is to provide a further detailed description of the present invention in conjunction with the accompanying drawings, so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, optimization or equivalent substitution of the method steps involved, as well as combination of implementation methods in different embodiments without causing structural and principle conflicts, all fall within the protection scope of the present invention.

Claims

1. A method for manufacturing TRISO fuel pellets, wherein the TRISO fuel pellets comprise a graphite matrix and fuel spheres, characterized in that, Includes the following steps: Step a): Provide a fuel pellet mold, and lay a layer of graphite powder inside the fuel pellet mold; Step b): Provide a puncture mold, the puncture mold having a puncture working surface, the puncture working surface being provided with a raised hemispherical working part; use the puncture mold to compact the graphite powder layer and make the hemispherical working part form a positioning hole in the graphite powder layer; Step c): Insert the fuel ball into the positioning hole and cover the fuel ball with a layer of graphite powder; Step d): The graphite powder layer laid in step c) is compacted using the pressing mold, and the hemispherical working part forms a positioning hole in the graphite powder layer; Step e): Repeat steps c) and d) until the graphite powder reaches the preset thickness, compact the graphite powder and sinter it to obtain TRISO fuel pellets.

2. The TRISO fuel pellet manufacturing method according to claim 1, characterized in that, Two pressing dies are configured, and when the two pressing dies are arranged coaxially, the projected positions of the hemispherical working parts of each die are staggered. Adjacent graphite powder layers are compacted using different denting dies.

3. The TRISO fuel pellet manufacturing method according to claim 1 or 2, characterized in that, When the graphite powder layer is laid, the thickness of the compacted graphite powder layer is not less than the diameter of the fuel ball.

4. The TRISO fuel pellet manufacturing method according to claim 1 or 2, characterized in that, The method for loading the fuel balls into the positioning holes is as follows: the same number of fuel balls as the positioning holes are sprinkled on the graphite powder layer in which the positioning holes are formed, and the fuel balls are made to fall into the positioning holes by vibration.

5. The TRISO fuel pellet manufacturing method according to claim 1 or 2, characterized in that, A filling mold is provided, wherein the filling mold is provided with filling holes, the filling holes corresponding one-to-one with the positioning holes, and the fuel ball is allowed to be engaged in the filling holes; The method for inserting the fuel ball into the positioning hole is as follows: The fuel ball is inserted into the filling hole of the filling mold, and the fuel ball is fed into the positioning hole through the filling mold.

6. The TRISO fuel pellet manufacturing method according to claim 1 or 2, characterized in that, The bottom of the fuel pellet mold is equipped with a lifting mechanism. The method for loading the fuel pellets into the positioning holes is as follows: No fewer than the number of fuel balls in the positioning holes are spread on the graphite powder layer with the positioning holes. Vibration is used to ensure that each fuel ball falls into the positioning hole. The compacted graphite powder blank is lifted to the top of the fuel pellet mold using a lifting mechanism, so that the fuel balls that do not fall into the positioning holes roll away from the graphite powder layer.

7. The TRISO fuel pellet manufacturing method according to claim 1 or 2, characterized in that, The hemispherical working part has the same radius as the fuel ball.

8. The TRISO fuel pellet manufacturing method according to claim 1 or 2, characterized in that, The radius of the positioning hole is 0.8mm-1.0mm.

9. A fuel pellet, comprising a graphite matrix and fuel spheres, characterized in that, The fuel pellets are manufactured using the TRISO fuel pellet manufacturing method as described in any one of claims 1 to 7.

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