Preparation method of modular reactor core and reactor core

Abstract

The invention provides a preparation method of a modular reactor core and the reactor core, and relates to the technical field of nuclear reaction. The preparation method of the modular reactor core comprises the following steps: S1, processing to obtain a plurality of substrates with assembly holes; s2, the pipe wall of the heat pipe and the cladding wall of the fuel assembly are evenly and fully coated with brazing filler metal; s3, the heat pipe and the fuel assembly prepared in the step 2 are inserted into the assembly holes and fixed through brazing; s4, the outer surface of the base body is fully coated with a high-thermal-conductivity interface material; s5, all the base bodies are assembled, extruded to be compact and fixed, and the reactor core of the specified structure is obtained. The reactor core comprises a central control rod and a plurality of module units, and the module units are arranged layer by layer around the central control rod and form a regular hexagonal structure. The invention solves the technical problem of large thermal resistance of the reactor core in modular design, and provides the preparation method of the reactor core capable of reducing the thermal resistance and improving the thermal conductivity and the reactor core structure.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear reactors, and in particular to a preparation method for a modular reactor core and a reactor core. Background Art

[0002] In the technical field of nuclear reactors, the core of a heat pipe reactor is divided into two forms: an integrated core and a modular core. Among them, the nuclear reactor named NUSTER-100 disclosed by Xi'an Jiaotong University adopts an integrated design scheme. However, the nuclear reactor involved in the integration has the problem of difficult processing. If any process goes wrong during the processing, it is necessary to start all over again. Although the technical scheme of reactor modular design has the advantage of good processability, due to the gap between adjacent modules, the thermal resistance is relatively large, which is not conducive to heat conduction, and the division method and assembly process directly affect the modular degree of the reactor.

[0003] In the prior art, for the modular designed core, Patent CN117854753A proposes a block division method suitable for an octagonal core, but it is not suitable for the mainstream hexagonal core; Patent CN112117016A proposes to place heat pipes and fuel assemblies in a liquid heat-conducting material to reduce the thermal resistance between adjacent modules and between heat pipes and fuel assemblies. However, the liquid heat-conducting material expands after being heated, which will bring risks to the overall core; Patent CN115148380A proposes that the matrix, heat pipes, and fuel assemblies are connected by spot welding, but the spot welding thermal resistance is relatively large, which is not conducive to heat transfer.

[0004] Therefore, the two problems that need to be solved urgently for the current modular heat pipe reactor are: First, how to solve the connection problems between heat pipes, fuel assemblies and matrix modules and the connection problems between matrix modules to achieve efficient heat transfer; Second, how to avoid the critical problems that may occur during the assembly process during the processing and assembly process. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problem of large thermal resistance between adjacent module units and between heat pipes and fuel assemblies in the core of the modular design in the prior art. The present invention provides the following technical solutions:

[0006] A preparation method for a modular reactor core includes the following steps:

[0007] S1: Process to obtain a plurality of matrices with assembly holes;

[0008] S2: Uniformly coat the tube wall of the heat pipe and the cladding wall of the fuel assembly with brazing filler metal;

[0009] S3: Insert the heat pipe and the fuel assembly prepared in step S2 into the assembly holes and fix them by brazing;

[0010] S4: Coat the outer surface of the matrix completely with a high thermal conductivity interface material;

[0011] S5: Assemble all the matrices and squeeze and fix the matrices tightly to obtain a reactor core with a specified structure.

[0012] Among them, the step S5 includes the following preparation steps:

[0013] S5a: Fix and install the central control rod;

[0014] S5b: With the central control rod as the center, assemble the matrices circle by circle from the center outwards. For each layer of matrices laid, squeeze them tightly and fix them by spot welding;

[0015] S5c: Complete the assembly of all the matrices to obtain a reactor core with a specified structure.

[0016] Preferably, the preparation method of the modular reactor core is applicable to a regular hexagonal core.

[0017] Preferably, the solder in step S2 is AgPd.

[0018] Preferably, the high thermal conductivity interface material in step S4 is graphite platinum.

[0019] Furthermore, the brazing in step S3 is vacuum induction brazing.

[0020] A reactor core prepared by the above preparation method of the modular reactor core, comprising a central control rod and a plurality of module units, wherein the module units are arranged layer by layer around the central control rod and form a regular hexagonal structure.

[0021] Furthermore, the module unit includes a matrix, and one or more assembly holes are provided on the matrix, and any one or both of a heat pipe and a fuel assembly pass through the assembly hole and are installed on the matrix.

[0022] Furthermore, the cross-section of the module unit is an isosceles trapezoid or an arrow-like shape, and all the module units arranged in an isosceles trapezoid shape and all the module units arranged in an arrow-like shape are arranged to form a regular hexagonal structure.

[0023] Furthermore, the module units adjacent to the central control rod are six module units with an isosceles trapezoid cross-section, and the six module units are arranged around the central control rod. Among them, the side lengths of the module units close to the central control rod together form a regular hexagon, and the bottom of any one module unit is in partial contact with the waist of another adjacent module unit.

[0024] The present invention has the following advantages:

[0025] (1) A preparation method of a modular reactor core is provided in the present invention. First, a brazing filler metal is evenly coated on the tube walls of the heat pipes and the cladding walls of the fuel assemblies, and then they are installed into the matrix. The connection between the heat pipes, the fuel assemblies and the matrix units is realized through brazing. Through the AgPd brazing filler metal, the heat pipes are in contact with the fuel assemblies during the installation stage of the heat pipes and the fuel assemblies, reducing the thermal resistance and improving the heat transfer efficiency between the heat pipes and the fuel assemblies. At the same time, through the thermal interface material, the gap between the module units and the adjacent module units is reduced, and the connection of the module units is realized through spot welding, thereby realizing efficient heat transfer.

[0026] (2) In the preparation process provided by the present invention, by first installing and fixing the control rods and then arranging the module units around the control rods, the critical problems that may occur during the assembly of the reactor core are eliminated, and the safety of the installation process is improved.

[0027] (3) The present invention provides a reactor core structure. The core structure is simple and conforms to the common regular hexagon structure in the prior art. However, due to the different arrangement methods, compared with the prior art, the core structure provided by the present invention has no contact points at the intersections of the vertices of multiple module units, which is convenient for welding and the arrangement method is more compact. Description of the Drawings

[0028] Figure 1 The matrix prepared in step S1 of the present invention;

[0029] Figure 2 The heat pipes and fuel assemblies prepared in step S2 of the present invention;

[0030] Figure 3 The product prepared in step S3 of the present invention;

[0031] Figure 4 The product prepared in step S4 of the present invention;

[0032] Figure 5 The product prepared in step S5a of the present invention;

[0033] Figure 6 The product prepared in step S5b of the present invention;

[0034] Figure 7 The reactor core prepared by the present invention.

[0035] In the figure: 00. Module unit, 1. Matrix, 2. Fuel assembly, 3. Central control rod, 4. Assembly hole, 5. Heat pipe. Detailed Description of the Invention

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0037] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents some embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0038] It should be noted that, without conflict, the embodiments in the present invention and the features and technical solutions in the embodiments may be combined with each other.

[0039] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present invention is usually placed during use, or the orientation or positional relationship commonly understood by those skilled in the art. Such terms are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for descriptive distinction and cannot be understood as indicating or implying relative importance.

[0040] Refer to Figures 1 to 7 , a preparation method for a modular reactor core, comprising the following steps:

[0041] S1: Process to obtain a plurality of substrates 1 with assembly holes 4;

[0042] S2: Uniformly coat the tube wall of the heat pipe 5 and the cladding wall of the fuel assembly 2 with brazing filler metal;

[0043] S3: Insert the heat pipe 5 and the fuel assembly 2 prepared in step 2 into the assembly holes 4 and fix them by brazing;

[0044] S4: Uniformly coat the outer surface of the substrate 1 with a high thermal conductivity interface material;

[0045] S5: Assemble all the substrates 1 and compact and fix the substrates 1 to obtain a reactor core with a specified structure.

[0046] Among them, the step S5 includes the following preparation steps:

[0047] S5a: Fix and install the central control rod 3;

[0048] S5b: With the central control rod 3 as the center, assemble the matrix 1 circle by circle from the center outwards. For each circle of the matrix 1 laid, it is compacted by extrusion and fixed by spot welding;

[0049] S5c: Complete the assembly of all the matrices 1 to obtain a reactor core with a specified structure.

[0050] The preparation method of the modular reactor core is applicable to a regular hexagonal core.

[0051] The filler metal in step S2 is AgPd, and this material is more suitable for the operating temperature range of the sodium heat pipe 5 reactor.

[0052] The high thermal conductivity interface material in step S4 is graphite platinum.

[0053] The brazing in step S3 is vacuum induction brazing, and this brazing method has a more uniform effect.

[0054] In the above solution, by first coating the outer wall of the heat pipe 5 and the cladding wall of the fuel assembly 2 with the filler metal, and the preferred filler metal is AgPd. Since the filler metal has fluidity under high temperature conditions (the high temperature conditions generally refer to a temperature higher than 1010 °C), after inserting the heat pipe 5 and the fuel assembly 2 with the filler metal into the assembly hole 4, due to the fluidity of the filler metal, it slowly fills the matrix 1 and the gap between the heat pipe 5 and the fuel assembly 2, reducing the thermal resistance caused by the gap between the heat pipe 5 and the fuel assembly 2, and enabling efficient heat conduction between the heat pipe 5 and the fuel assembly 2. Specifically, the outer wall of the heat pipe 5 and the cladding wall of the control assembly are coated with the filler metal, and the diameters of the heat pipe 5 and the fuel assembly 2 after coating are larger than the assembly hole 4. After inserting the heat pipe 5 and the fuel assembly 2 prepared in step S2 into the assembly hole 4, the filler metal accumulates on the upper surface of the matrix 1. Since the filler metal has fluidity under certain conditions, the filler metal flows slowly into the matrix 1 along the gap between the heat pipe 5 or the fuel assembly 2 and the assembly hole 4 of the matrix 1, filling the gap between the heat pipe 5 and the fuel assembly 2, and then the filler metal is solidified, and the heat pipe 5 and the fuel assembly 2 are fixed by brazing technology.

[0055] In step S4, since the outer surface of the matrix 1 is coated with the high thermal conductivity interface material, and the preferred high thermal conductivity interface material is graphite platinum, when the two matrices 1 are arranged and installed, at the contact part of the adjacent two matrices 1, due to the high thermal conductivity interface material, the gap between the adjacent two matrices 1 is filled with the high thermal conductivity interface material with a certain fluidity, which reduces the thermal resistance and thus improves the heat conduction efficiency between the two matrices 1.

[0056] In step S5, by first installing the fixed central control rod 3 and then, with the central control rod 3 as the center, arranging the module units 00 around the central control rod 3, the critical problems that may occur during the assembly of the reactor core are eliminated, and the safety of the installation process is improved. Specifically, by first installing the central control rod 3 and then arranging the module units 00, that is, arranging the fuel assemblies 2, if a nuclear reaction occurs between the fuel assemblies 2 during the arrangement process, neutrons are generated and absorbed by the central control rod 3, which improves the safety during the installation process.

[0057] A reactor core prepared by the method for preparing a modular reactor core as described above, comprising a central control rod 3 and a plurality of module units 00, wherein the module units 00 are arranged layer by layer around the central control rod 3 to form a regular hexagon structure.

[0058] Furthermore, the module unit 00 includes a base body 1, and one or more assembly holes 4 are provided on the base body 1, and any one or both of the heat pipes 5 and the fuel assemblies 2 are installed on the base body 1 through the assembly holes 4.

[0059] Furthermore, the cross-section of the module unit 00 is an isosceles trapezoid or a shape similar to an arrowhead, and all the module units 00 arranged in an isosceles trapezoid shape and all the module units 00 arranged in a shape similar to an arrowhead are arranged to form a regular hexagon structure.

[0060] Furthermore, the module units 00 adjacent to the central control rod 3 are six module units 00 with an isosceles trapezoid cross-section. The six module units 00 are arranged around the central control rod 3. Among them, the side lengths of the module units 00 close to the central control rod 3 together form a regular hexagon, and the bottom side of any one module unit 00 is in partial contact with the waist side of another adjacent module unit 00. The module units 00 adjacent to the central control rod 3 are six module units 00 with an isosceles trapezoid cross-section, that is, the module units 00 closest to the central control rod 3 and at the same distance.

[0061] In the above solution, since the bottom edge of any module unit 00 is in partial contact with the waist edge of another adjacent module unit 00, there will be no situation where the top angles of two adjacent module units 00 are in contact. This enables, when welding two adjacent module units 00, welding only through the part of the adjacent side lengths in contact, without the need to weld at multiple top angle contact points. This layout design method facilitates the execution of subsequent welding steps. At the same time, it avoids technical problems such as instability of the module unit 00 and easy separation after fixation that are prone to occur at the vertex contact points. Further, when arranging the layout, according to the size of the central control rod 3, the contact distance between the bottom edge of the six module units 00 arranged around the central control rod 3 and the waist edge of another adjacent module unit 00 can be adjusted, minimizing the gap between the central control rod 3 and the module unit 00 as much as possible, and further miniaturizing the reactor core volume within the target reactor power amount; achieving the technical effect of the module unit 00 being adjustable according to the size of the central control rod 3.

[0062] Example 1:

[0063] A method for preparing a modular reactor core includes the following steps:

[0064] S1: Through wire cutting or other precision machining techniques, multiple substrates 1 with assembly holes 4 are machined; the diameter of the assembly holes 4 is 10 - 30 mm.

[0065] S2: AgPd is evenly coated on the tube wall of the heat pipe 5 and the cladding wall of the fuel assembly 2.

[0066] S3: The heat pipe 5 and the fuel assembly 2 prepared in step 2 are inserted into the assembly holes 4, the heating temperature is raised to 1010 °C, the solder starts to melt and flow to fill the gaps; after filling the gaps, the temperature is lowered, and after the solder is fixed, it is fixed by vacuum brazing technology.

[0067] S4: The outer surface of the substrate 1 is evenly coated with graphite platinum.

[0068] S5a: Fix and install the central control rod 3;

[0069] S5b: With the central control rod 3 as the center, the substrates 1 are assembled circle by circle from the center outwards. For each circle of substrates 1 laid, they are squeezed tightly and fixed by spot welding;

[0070] S5c: After all the substrates 1 are assembled, a reactor core with the specified structure is obtained. Through theoretical thermal calculation, the thermal resistance value of the above reactor core is 0.03 m·K / W.

[0071] Example 2:

[0072] Prepared according to the steps of Example 1, except that in step S2, the tube walls of the heat pipes 5 and the cladding walls of the fuel assemblies 2 are not fully coated with AgPd, in step S3, they are directly fixed, and in step S4, the outer surface of the substrate 1 is not fully coated with graphite platinum and is directly spot-welded and fixed. The fuel rods or heat pipes 5 of the reactor core prepared in Example 2 are in clearance fit with the substrate 1. Through theoretical thermal-hydraulic calculations, the resistance value of the above reactor core is obtained as 0.05 m·K / W.

[0073] In summary, the reactor core prepared according to the process disclosed in the present invention has a lower resistance value compared with the reactor core prepared by the prior art, reducing the influence of thermal resistance on the heat conduction performance, and the reactor core prepared by the process provided by the present invention has better heat conduction performance.

[0074] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a modular reactor core, characterized in that: The following steps are involved: S1: Processing to obtain a plurality of substrates with assembly holes; S2: evenly apply the brazing filler metal on the tube wall of the heat pipe and the cladding wall of the fuel assembly; S3: inserting the heat pipe and fuel assembly prepared in step 2 into the assembly hole and fixing them by brazing; S4: Coat the outer surface of the substrate with a high thermal conductivity interface material; S5: Assemble all the bases and squeeze and fix them to obtain a reactor core with a specified structure.

2. A method for preparing a modular reactor core according to claim 1, characterized in that: The step S5 comprises the following steps: S5a: fixed installation center control rod; S5b: With the central control rod as the center, assemble the matrix circle by circle from the center to the outside. After each circle of matrix is ​​laid, it is squeezed compactly and fixed by spot welding. S5c: Complete all base assembly and obtain the reactor core of the specified structure.

3. The method for preparing a modular reactor core according to claim 1, characterized in that: The preparation method is applicable to a regular hexagonal core.

4. The method for preparing a modular reactor core according to claim 1, characterized in that: The solder in step S2 is AgPd.

5. The method for preparing a modular reactor core according to claim 1, characterized in that: The high thermal conductivity interface material in step S4 is graphite platinum.

6. A method for preparing a modular reactor core according to claim 2, characterized in that: The brazing in step S3 is vacuum induction brazing.

7. A reactor core prepared by any one of the methods for preparing a modular reactor core according to claims 1 to 6, characterized in that: The invention comprises a central control rod and a plurality of module units, wherein the module units are arranged layer by layer around the central control rod to form a regular hexagonal structure.

8. The reactor core according to claim 7, characterized in that The module unit comprises a base body, one or more assembly holes are arranged on the base body, and any one or both of the heat pipe and the fuel assembly are installed on the base body through the assembly holes.

9. The reactor core according to claim 8, characterized in that The cross section of the module unit is in an isosceles trapezoid or an arrow-like shape, and all the module units arranged in an isosceles trapezoid and all the module units arranged in an arrow-like shape are arranged together to form a regular hexagonal structure.

10. The reactor core according to claim 9, characterized in that The module units adjacent to the central control rod are six module units with isosceles trapezoidal cross sections, and the six module units are arranged around the central control rod, wherein the sides of the module units close to the central control rod together form a regular hexagon, and the bottom of any module unit contacts the waist of another adjacent module unit.

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