radial traveling wave reactor

Abstract

The application provides a radial traveling wave reactor, comprising a heat pipe and a plurality of fuel assemblies, the plurality of fuel assemblies are sequentially arranged along the radial direction of a reactor core; the heat pipe is correspondingly arranged with fuel elements in the fuel assemblies located at the reactor core; in the radial direction from the center of the reactor core to the edge of the reactor core, the enrichment degree of the plurality of fuel assemblies is different, the fuel assembly with the largest enrichment degree is used as an ignition area, and the other fuel assemblies are used as breeding areas. The application can stabilize the power peak in the axial direction and is beneficial to improving the heat transfer efficiency of the heat pipe with axial heat conduction.

Description

Technical Field

[0001] This invention relates to the field of traveling wave reactor technology, and more specifically, to a radial traveling wave reactor, particularly a novel traveling wave reactor for radial propagation of breeding-burnout waves. Background Technology

[0002] Traveling wave (fast) reactors utilize fast neutrons to generate energy through a chain fission reaction. During operation, the reactor core exhibits a moving "breeding-burnup" wave. They can employ an open fuel cycle or directly use low-enrichment fuels (such as natural uranium or spent fuel from thermal reactors). A single fuel load can sustain "burning" to a sufficient burnup depth, avoiding mid-life shutdowns for refueling (except for standing wave reactors).

[0003] Taking a traveling wave reactor with a uranium-plutonium cycle where the breeder-burnup wave (traveling wave) propagates axially as an example, the reactor's fuel elements are composed of fuels with different enrichment levels along the axial direction. The basic principle is that the reactor core is divided into a small ignition zone (using highly enriched uranium) and a large burnup zone (using highly enriched fuel) along the axial direction (traveling wave direction). When the reactor is started, the ignition zone first "ignites" to criticality. The fast neutrons produced will cause U238 in the nearby burnup zone to be converted into Pu239. Then, these converted Pu239 will cause the nearby area to enter criticality, thus forming a breeder-burnup wave. This wave continuously causes the natural uranium or spent fuel in the burnup zone ahead of the wave to produce a breeder reaction, and then enters the "burnup" (critical fission) reaction stage. Along the propagation direction of this wave, the local reactivity goes through a process of first rising to supercritical and then falling to subcritical. The critical wave slowly passes through the entire reactor core along the axial direction during the core's lifespan. During this process, after ignition and startup, the traveling wave reactor enters a self-sustaining phase. Under ideal conditions, the remaining reactivity of the entire reactor remains unchanged during burnup, so no reactivity control is required. Theoretically, a self-sustaining traveling wave fast reactor with an arbitrarily long lifespan only needs to increase the fuel reserve in the traveling wave direction of its core.

[0004] Based on the propagation mode of the traveling wave (burnup-breeding wave), current traveling wave reactor designs can be divided into two main categories: axial traveling wave reactors, where the fuel elements are composed of fuels with different enrichment levels along the axial direction and the traveling wave also propagates along the axial direction; and radial standing wave reactors, where the fuel assemblies are divided into multiple groups along the core radially and the positions of these fuel assemblies are continuously adjusted during reactor operation (i.e., "refueling"). This involves removing the fuel that has burned in the center of the core, adding new fuel to the outside of the core, and moving other core components sequentially towards the center to stabilize the core power distribution (i.e., the burnup-breeding wave is a standing wave, not a traveling wave, in the laboratory reference coordinate system). (If the reference coordinate system is set on a certain group of fuel elements, the process of burnup-breeding wave propagation on that fuel element can still be observed because all the fuel elements in the core are moving towards the core center. This is why this reactor design is still classified as a traveling wave reactor.)

[0005] Radial standing wave reactors are complex to design, and fuel assemblies can be classified into nearly 10 types according to different enrichment levels. The feeding process requires the support of relevant engineering equipment, which increases the difficulty and cost of designing and operating this type of reactor.

[0006] Patent document CN111739666B discloses a traveling wave reactor for space exploration. The reactor core is dispersed into several modules along the traveling wave direction. In a zero-burnup configuration, the new reactor consists of a start-up source module and multiple new fuel modules. These modules are coaxially assembled along the traveling wave direction using assembly components. Each module also includes heat pipes. During assembly, the heat pipes in the front-end modules pass through all the modules behind them and extend from the rearmost module. After a period of burnup, the reactor core, along the traveling wave direction, consists of a start-up source module, spent fuel modules, critical fuel modules, and new fuel modules. However, this patent document still highlights the significant challenges and costs associated with reactor design and operation. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the purpose of this invention is to provide a radial traveling wave stack.

[0008] According to the present invention, a radial traveling wave reactor includes: a plurality of heat pipes and a plurality of fuel assemblies, wherein the plurality of fuel assemblies are arranged sequentially along the radial direction of the reactor core;

[0009] In the radial direction from the core center to the core edge, the enrichment of several fuel assemblies is different. The fuel assembly with the highest enrichment is designated as the ignition zone, and the other fuel assemblies are designated as the breeding zone.

[0010] Each of the fuel assemblies includes a plurality of fuel elements, and each of the fuel elements is provided with a heat pipe.

[0011] Preferably, the fuel elements in the same fuel assembly are connected by any of the following methods: welding, integral casting, or mechanical connection.

[0012] Preferably, integral casting involves directly forming all fuel elements into a single fuel assembly using metalworking methods;

[0013] The welding connection involves welding and fixing the fuel elements together using pre-reserved joints. Fuel elements located at the edge of the fuel assembly are welded and fixed on the side, while fuel elements located in the inner ring of the fuel assembly are welded and fixed at the top and bottom.

[0014] The mechanical connection is fixed by inserting and interlocking pins and grooves machined on the side of the fuel element.

[0015] Preferably, the heat pipe includes a heat pipe wall, a liquid wick, an evaporator end cap, and a condenser end cap;

[0016] The liquid-absorbing core is disposed on the inner side wall of the heat pipe, and the evaporation end cap and the condensation end cap are respectively disposed at both ends of the heat pipe wall;

[0017] The heat pipe wall is provided with an evaporation section, an insulation section and a condensation section in sequence. The evaporation section is provided with a heat source and the condensation section is provided with a heat dissipation component.

[0018] Preferably, the fuel assembly is installed within several nested structures.

[0019] Preferably, the nested structure is provided with an installation cavity for installing the fuel assembly.

[0020] Preferably, a ball bearing buckle is provided on the surface of the fuel assembly that contacts the nested structure, and a positioning groove and a fixing recess are provided on the surface of the nested structure that contacts the fuel assembly.

[0021] Preferably, during the consumption of the fuel assembly in the ignition zone, the fissile nuclides in the ignition zone gradually decrease, and the radial power peak gradually moves to the breeding zone, forming a radially traveling wave.

[0022] Preferably, the fuel assembly located at the center of the reactor core is cylindrical, and the remaining fuel assemblies are sleeve-shaped and are sequentially sleeved around the fuel assembly located at the center of the reactor core along the radial direction of the reactor core.

[0023] Preferably, the fuel assembly is configured as three parts, namely a first fuel assembly, a second fuel assembly, and a third fuel assembly;

[0024] The first fuel assembly, the second fuel assembly, and the third fuel assembly are arranged radially along the stack configuration;

[0025] The regions where the first and second fuel assemblies are located are designated as the breeding zone, and the region where the third fuel assembly is located is designated as the ignition zone.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The structural design of this invention can stabilize the power peak in the axial direction, which is beneficial to improving the heat transfer efficiency of the axial heat pipe. Furthermore, due to the movement of the radial power peak, the fuel element with the highest radial temperature will gradually shift during core operation, which is beneficial to improving fuel safety.

[0028] 2. The difference between this invention and existing designs is that it is the first to propose a design in which the traveling wave propagates radially in a traveling wave stack. In existing designs, the traveling wave is either propagated axially or is a standing wave that is stable in either the radial or axial direction.

[0029] 3. The fuel assembly of the present invention is divided into multiple groups with different enrichment levels from the inside out. One group has the highest enrichment level and serves as the ignition zone. The other fuel assemblies with lower enrichment levels serve as the breeder zones. Since the proportion of fissile nuclides in the breeder zone is higher, they can absorb neutrons from the ignition zone and undergo a breeder reaction to generate fissile nuclides, thereby improving the quality of fissile nuclides in the breeder zone. As the fissile nuclides decrease due to the consumption of fuel in the ignition zone, the radial power peak gradually moves to the breeder zone, forming a radial traveling wave and maintaining the long-term stable criticality of the reactor core. Attached Figure Description

[0030] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0031] Figure 1 A schematic diagram of the fuel assembly arrangement in a radial traveling wave reactor;

[0032] Figure 2 This is a schematic diagram of a heat pipe structure;

[0033] Figure 3 This is a schematic diagram of the power peak shift in a radial traveling wave stack.

[0034] Figure 4 Axonometric drawing of a single nested structure;

[0035] Figure 5 The main view of a single nested structure;

[0036] Figure 6 The left view of a single nested structure;

[0037] Figure 7 A top view of a single nested structure;

[0038] Figure 8 A cross-sectional view of a single nested structure along line AA;

[0039] Figure 9 Axonometric view of a single fuel element;

[0040] Figure 10 A front view of a single fuel element;

[0041] Figure 11 Left view of a single fuel element;

[0042] Figure 12 A top view of a single fuel element;

[0043] Figure 13 A schematic diagram of fuel elements being installed into a nested structure.

[0044] The diagram shows:

[0045] First fuel assembly 1, heat source 5

[0046] Second fuel assembly 2, heat dissipation assembly 6

[0047] Third fuel assembly 3, fuel element 7

[0048] Heat pipe 4 nested structure 8

[0049] Heat pipe wall 401 Mounting cavity 801

[0050] Liquid suction core 402, positioning slot 802

[0051] Evaporator end cap 403, fixing recess 803

[0052] Condenser cap 404 stainless steel, ball bearing clip 9 Detailed Implementation

[0053] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0054] Example 1:

[0055] like Figures 1-13As shown, this embodiment provides a radial traveling wave reactor, including: a plurality of heat pipes 4 and a plurality of fuel assemblies. The plurality of fuel assemblies are arranged sequentially along the radial direction of the reactor core. In the direction from the center of the reactor core to the edge of the reactor core, the enrichment of the plurality of fuel assemblies is different. The fuel assembly with the highest enrichment is used as the ignition zone, and the other fuel assemblies are used as the breeding zone. Each fuel assembly includes a plurality of fuel elements 7, and each fuel element 7 is provided with a heat pipe 4.

[0056] The radial traveling wave reactor also includes several nested structures 8, within which fuel assemblies are installed. Each nested structure 8 has a mounting cavity 801 for installing the fuel assemblies. A ball bearing buckle 9 is provided on the surface of the fuel assembly that contacts the nested structure 8, and a positioning groove 802 and a fixing recess 803 are provided on the surface of the nested structure 8 that contacts the fuel assembly. Figures 9-13 Take the first fuel assembly 1 as an example.

[0057] In this embodiment, three fuel assemblies are provided, namely the first fuel assembly 1, the second fuel assembly 2 and the third fuel assembly 3. The first fuel assembly 1, the second fuel assembly 2 and the third fuel assembly 3 are arranged in sequence along the radial direction of the stack. The area where the first fuel assembly 1 and the second fuel assembly 2 are located is the breeding zone, and the area where the third fuel assembly 3 is located is the ignition zone.

[0058] Several fuel elements 7 in the same fuel assembly are connected by any of the following methods: welding, integral casting, or mechanical connection. Integral casting involves directly forming all fuel elements 7 into a single fuel assembly through metal processing methods. Welding connection involves welding and fixing the fuel elements 7 together with pre-reserved joints. Fuel elements 7 located at the edge of the fuel assembly are welded and fixed on the side, while fuel elements 7 located in the inner ring of the fuel assembly are welded and fixed at the top and bottom. Mechanical connection involves connecting and fixing the fuel elements 7 by inserting and interlocking pins and grooves machined on the side of the fuel elements 7.

[0059] The heat pipe 4 includes a heat pipe wall 401, a liquid wick 402, an evaporation end cap 403, and a condensation end cap 404. The liquid wick 402 is disposed on the inner side wall of the heat pipe wall 401. The evaporation end cap 403 and the condensation end cap 404 are respectively disposed at both ends of the heat pipe wall 401. An evaporation section, an adiabatic section, and a condensation section are sequentially disposed on the heat pipe wall 401. A heat source 5 is disposed in the evaporation section, and a heat dissipation component 6 is disposed in the condensation section.

[0060] The fuel assembly located at the core center is cylindrical, while the remaining fuel assemblies are sleeve-shaped and sequentially fitted around the fuel assembly at the core center along the radial direction of the core. During the consumption of fuel assemblies in the ignition zone, the fissile nuclides in the ignition zone gradually decrease, and the radial power peak gradually shifts to the breeding zone, forming a radially traveling wave.

[0061] In this embodiment, the fuel assembly is divided into multiple groups of different enrichment levels (e.g., 3 groups) from the inside out. One group has the highest enrichment level and serves as the ignition zone. The other fuel assemblies with lower enrichment levels serve as the breeder zones. Since the breeder zone assemblies have a higher proportion of fissile nuclides (e.g., U238), they can absorb neutrons from the ignition zone and undergo a breeder reaction to generate fissile nuclides (Pu239), thereby improving the quality of fissile nuclides in the breeder zone. As the fissile nuclides decrease due to the consumption of fuel in the ignition zone, the radial power peak gradually moves to the breeder zone, forming a radial traveling wave and maintaining the long-term stable criticality of the reactor core.

[0062] Figure 1 As shown, the reactor core is divided into three radially regions. The region containing the third fuel assembly 3 has the highest enrichment level and serves as the ignition zone. The region containing the second fuel assembly 2 has a lower enrichment level and serves as the breeding zone. The region containing the first fuel assembly 1 has the lowest enrichment level. Given the core's geometry, materials, and power design, a radial power distribution as shown can be achieved. Figure 3 As shown, in the initial burnup phase, the power peak is located in the ignition zone. As the core operates, the breeder-burnup peak shifts, and the power peak gradually moves to the breeder zone, successfully forming a radially traveling wave reactor design with a radially shifting power peak. The three fuel assemblies are internally fixed, using methods such as welding, casting, or mechanical connection, and then formed into a complete core through nested insertion. Figure 1 The areas containing the first fuel assembly 1, the second fuel assembly 2, and the third fuel assembly 3 each form a separate unit. During each installation, the area with the highest enrichment is installed last before the reactor is finally started to ensure reactor safety.

[0063] Multiple fuel assemblies can be fixed together individually by welding, casting, or mechanical fastening, and then the fuel assemblies are nested together to form a complete reactor core. During manufacturing, transportation, and commissioning, the assembly with the highest enrichment can be left out, preventing accidental criticality of the core and improving reactor safety.

[0064] Unlike existing axial traveling wave reactors, in which each fuel assembly has a high enrichment region (ignition zone) at one end of the axial direction and a low enrichment region (breeding zone) in the remaining axial direction, the breeding-burnup wave propagates from the ignition zone to the breeding zone, forming a traveling wave along the axial direction.

[0065] Unlike existing radial standing wave reactor designs, where fuel assemblies are divided into nearly 10 groups from the inside out and are continuously extracted from the central area by refueling, all fuel assemblies move inward sequentially, and new fuel is then added to the outside. That is, the central group of fuel assemblies is extracted first, and then all other fuel assemblies are filled inward sequentially. New fuel assemblies are then added to the nine areas formed by the inward filling of the outermost nine groups of fuel assemblies, thus maintaining the power stability of the reactor. In the proposed design, the fuel assemblies are fixed in groups, and individual assemblies cannot be moved during operation.

[0066] This embodiment uses heat pipes for axial heat conduction to remove heat from the reactor core. In contrast, all existing radial standing wave reactors use non-heat pipe technology, which uses fluid (such as water, gas, liquid metal, etc.) pipes and pump sets for forced circulation as a cooling method. The heat pipe design in this embodiment will not cause the loss of coolant accident (LOCA) that is common when using fluid pipes and pump sets, thus providing higher safety.

[0067] This embodiment differs from existing designs in that it proposes for the first time a design where traveling waves propagate radially in a traveling wave reactor. Existing designs either propagate traveling waves axially or consist of standing waves that remain stable in either the radial or axial direction. This embodiment's design allows for axial power peak stabilization, which improves the heat transfer efficiency of axially conductive heat pipes. Furthermore, the radial shift of the power peak causes the radially hottest fuel element to gradually transfer during core operation, enhancing fuel safety.

[0068] Example 2:

[0069] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1.

[0070] This embodiment provides a radial traveling wave reactor, including: a heat pipe 4 for discharging core heat energy and several fuel assemblies for generating fission heat energy, wherein the fuel assemblies are arranged sequentially along the radial direction of the core; the heat pipe 4 is connected to fuel elements 7 located in the core. In the direction from the core to the edge of the reactor structure, the enrichment levels of the fuel assemblies are different, with the fuel assembly with the highest enrichment level serving as the ignition zone and the other fuel assemblies serving as the breeding zone.

[0071] The enrichment level can be selected and set using the following method:

[0072] Step 1: Initially set the fuel enrichment level in the ignition zone to 20%;

[0073] Step 2: Set the fuel in the breeder zone furthest from the ignition zone to the enrichment level of natural uranium (or thorium);

[0074] Step 3: Select the enrichment degree of the intermediate breeder zone fuel (excluding the breeder zone in Step 2) as a uniform interval value between 20% and the enrichment degree of natural uranium (or thorium);

[0075] Step 4: Calculate whether the design meets the criticality requirements throughout the entire operating cycle of the reactor core;

[0076] Step 5: If the condition is not met, increase the enrichment level in Step 1 by 5%, which corresponds to increasing the enrichment level in Step 3 by 20% as the increased value. Then repeat Step 3 and Step 4.

[0077] Step 6: Repeat step 5 until the critical requirements for the entire operating cycle are met.

[0078] The fuel assembly includes several fuel elements 7. Since the fuel elements of the same enrichment in this embodiment do not need to be frequently repositioned in the core, unlike the separate and movable fuel elements 7 in most existing nuclear reactors, the several fuel elements 7 within the same fuel assembly are connected in any of the following ways:

[0079] Integral casting means that all fuel elements 7 are directly formed into a single fuel assembly through metal processing methods such as casting.

[0080] Welded connection, that is, multiple fuel elements 7 are welded and fixed by pre-reserved joints, fuel elements 7 located at the edge of the module are welded and fixed on the side, and fuel elements 7 located in the inner ring of the module are welded and fixed at the top and bottom;

[0081] The mechanical connection can be achieved by inserting and interlocking pins and grooves machined on the side of the fuel element 7, and then fixing the connection.

[0082] The heat pipe 4 includes a heat pipe wall 401, a liquid wick 402, an evaporation end cap 403, and a condensation end cap 404. The liquid wick 402 is disposed on the inner side wall of the heat pipe wall 401. The evaporation end cap 403 and the condensation end cap 404 are respectively disposed at both ends of the heat pipe wall 401. An evaporation section, an adiabatic section, and a condensation section are sequentially disposed on the heat pipe wall 401. A heat source 5 is disposed in the evaporation section, and a heat dissipation component 6 is disposed in the condensation section.

[0083] The radial traveling wave reactor also includes a nested structure, within which several fuel assemblies are installed. On the contact surfaces of the nested structures where different fuel assemblies are installed, ball bearing clips are provided on one side of the contact surface, and positioning grooves and fixing recesses are provided on the corresponding other side of the contact surface to ensure accurate positioning and fixation of the nesting.

[0084] The nested structure has several mounting cavities for installing fuel assemblies.

[0085] During the consumption of fuel assemblies in the ignition zone, the fissile nuclides in the ignition zone gradually decrease, and the radial power peak gradually moves to the breeding zone, forming a radial traveling wave.

[0086] The fuel assembly located at the core of the reactor is a near-cylindrical polygonal prism, while the other fuel assemblies are sleeve-shaped and arranged in layers around the fuel assembly at the center of the core along the radial direction of the core.

[0087] The fuel assembly is configured as three fuel assemblies, namely the first fuel assembly 1, the second fuel assembly 2, and the third fuel assembly 3. The first fuel assembly 1, the second fuel assembly 2, and the third fuel assembly 3 are arranged in sequence along the radial direction of the reactor. The area where the first fuel assembly 1 and the second fuel assembly 2 are located is the breeding zone, and the area where the third fuel assembly 3 is located is the ignition zone.

[0088] The heat pipe evaporation end is inserted into the pre-drilled hole of the fuel element, and the condensation end is connected to the energy conversion system outside the reactor core.

[0089] like Figure 1 As shown, the largest hexagonal prism is called the reactor core, which is divided into three concentric rings (the innermost ring is a cylinder). Each ring is called a fuel assembly, and each fuel assembly is composed of many smaller hexagonal prisms, which are called fuel elements. The circle or rod at the center of each fuel element is the heat pipe. This embodiment does not limit the shape of the fuel assembly; it can be a hexagonal prism or other shapes. When the fuel assemblies are connected by casting, the small hexagonal prisms do not exist, and the entire reactor core can be made into a standard cylinder. The three rings of fuel assemblies then become a structure of rings within rings within cylinders.

[0090] This invention can stabilize the power peak in the axial direction, which is beneficial to improving the heat transfer efficiency of axially heat-conducting heat pipes.

[0091] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0092] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A radial traveling wave stack, characterized in that, include: A plurality of heat pipes (4) and a plurality of fuel assemblies, wherein the plurality of fuel assemblies are arranged in sequence along the radial direction of the core; In the radial direction from the core center to the core edge, the enrichment of several fuel assemblies is different. The fuel assembly with the highest enrichment is designated as the ignition zone, and the other fuel assemblies are designated as the breeding zone. Each of the fuel assemblies includes a plurality of fuel elements (7), and each of the fuel elements (7) is provided with a heat pipe (4); The fuel assemblies are grouped and fixed, and individual assemblies cannot be moved during operation.

2. The radial traveling wave stack according to claim 1, characterized in that, The fuel elements (7) in the same fuel assembly are connected by any of the following methods: welding, integral casting, or mechanical connection.

3. The radial traveling wave stack according to claim 2, characterized in that, One-piece casting involves directly forming a single fuel assembly by using metal processing methods to integrate all fuel elements (7). The welding connection is to weld and fix the fuel elements (7) together by pre-reserved joints. The fuel elements (7) located at the edge of the fuel assembly are welded and fixed on the side, and the fuel elements (7) located in the inner ring of the fuel assembly are welded and fixed at the top and bottom. The mechanical connection is fixed by inserting and interlocking pins and grooves machined on the side of the fuel element (7).

4. The radial traveling wave stack according to claim 1, characterized in that, The heat pipe (4) includes a heat pipe wall (401), a liquid wick (402), an evaporation end cap (403), and a condensation end cap (404). The liquid-absorbing core (402) is disposed on the inner side wall of the heat pipe wall (401), and the evaporation end cap (403) and the condensation end cap (404) are respectively disposed at both ends of the heat pipe wall (401); An evaporation section, an insulation section, and a condensation section are sequentially arranged on the heat pipe wall (401). The evaporation section is provided with a heat source (5), and the condensation section is provided with a heat dissipation component (6).

5. The radial traveling wave stack according to claim 1, characterized in that, It also includes several nested structures (8), within which the fuel assembly is installed.

6. The radial traveling wave stack according to claim 5, characterized in that, The nested structure (8) is provided with an installation cavity (801) for installing the fuel assembly.

7. The radial traveling wave stack according to claim 6, characterized in that, A ball buckle (9) is provided on the surface of the fuel assembly that contacts the nested structure (8), and a positioning groove (802) and a fixing recess (803) are provided on the surface of the nested structure (8) that contacts the fuel assembly.

8. The radial traveling wave stack according to claim 1, characterized in that, During the consumption of the fuel assembly in the ignition zone, the fissile nuclides in the ignition zone gradually decrease, and the radial power peak gradually moves to the breeding zone, forming a radially traveling wave.

9. The radial traveling wave stack according to claim 1, characterized in that, The fuel assembly located at the center of the reactor core is cylindrical, while the remaining fuel assemblies are sleeve-shaped and are sequentially sleeved around the fuel assembly located at the center of the reactor core along the radial direction of the reactor core.

10. The radial traveling wave stack according to claim 1, characterized in that, The fuel assembly is configured as three parts, namely the first fuel assembly (1), the second fuel assembly (2) and the third fuel assembly (3). The first fuel assembly (1), the second fuel assembly (2), and the third fuel assembly (3) are arranged sequentially along the radial direction of the reactor structure; The area where the first fuel assembly (1) and the second fuel assembly (2) are located is designated as the breeding zone, and the area where the third fuel assembly (3) is located is designated as the ignition zone.

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