Pressurized water reactor fuel assembly and core

Abstract

The application discloses a pressurized water reactor fuel assembly and a reactor core, and the pressurized water reactor fuel assembly comprises: a first fuel assembly arranged in a central area of a pressure vessel; and at least one second fuel assembly arranged in a gap between the first fuel assembly and the pressure vessel. The second fuel assembly in the pressurized water reactor fuel assembly is arranged in an irregular space between the pressure vessel and the conventional first fuel assembly, which is different from conventional pressurized water reactor fuel assemblies such as square assemblies or hexagonal assemblies. The internal space of the pressure vessel is reasonably utilized, so that the fuel loading capacity of the reactor core is increased, the average power density of the reactor core is reduced, the safety of the reactor core is improved, the power of the reactor core is increased, and the economy of the reactor core is improved.

Description

Technical Field

[0001] This invention belongs to the field of pressurized water reactor design technology, specifically relating to a pressurized water reactor fuel assembly and reactor core. Background Technology

[0002] In a pressurized water reactor (PWR), coolant flows over the outer wall of the fuel rods, carrying away the heat generated by the fission reaction. If the heat generated inside the fuel rods cannot be carried away by the coolant in time, it will cause the fuel rods to melt down or break. Therefore, in core design, the maximum linear power density of the core is limited to ensure core safety. The maximum linear power density of the core is the core average linear power density multiplied by the power peak factor. With the power peak factor constant, the core average linear power density is related to the core's economics and safety.

[0003] Reducing the average line power density of the reactor core can improve safety but reduce economic efficiency; increasing the average line power density of the reactor core can improve the economic efficiency of the reactor core but reduce its safety.

[0004] The Hualong One reactor types Fuqing Units 5 and 6 increased the number of fuel assemblies from 157 in the M310 reactor type to 177. While increasing the overall core power, the average linear power density was appropriately reduced. However, the increased pressure vessel radius will increase construction costs.

[0005] The Zhangzhou scheme for the Hualong One reactor increases the core thermal power from 3050MW to 3180MW in the Fuqing Unit 56, improving economic efficiency, but reducing thermal margin. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a pressurized water reactor fuel assembly and core, which can increase the number of fuel rods, reduce the average linear power density of the core, and improve economy and safety without increasing the radius of the pressure vessel.

[0007] The technical solution adopted to solve the technical problem of the present invention is to provide a pressurized water reactor fuel assembly, including: a first fuel assembly, which is disposed in a pressure vessel and in the central region of the pressure vessel; the pressurized water reactor fuel assembly further includes: at least one second fuel assembly, which is disposed in the gap between the first fuel assembly and the pressure vessel.

[0008] Preferably, the second fuel assembly includes: a fuel rod, a grid, an upper tube seat, and a lower tube seat. The upper tube seat is located above the fuel rod, the lower tube seat is located below the fuel rod, and the grid is located in the middle of the fuel rod's axial direction. The upper tube seat, lower tube seat, and grid serve to fix the fuel rod.

[0009] Preferably, two sides of the cross-section of the second fuel assembly are in contact with the first fuel assembly, and the remaining sides of the cross-section of the second fuel assembly are any one of a straight line, an arc, or a broken line.

[0010] Preferably, the second fuel assembly has at least one grid.

[0011] Preferably, the vertical projection view of the second fuel assembly is within the inner diameter of the pressure vessel, and the cross-sectional area of ​​the second fuel assembly is smaller than that of the first fuel assembly.

[0012] The present invention also provides a pressurized water reactor core, comprising: a pressurized water reactor fuel assembly, a pressure vessel, and a coolant. The pressurized water reactor fuel assembly is the pressurized water reactor fuel assembly described above. The pressurized water reactor fuel assembly includes: a first fuel assembly and a second fuel assembly. The first fuel assembly is disposed inside the pressure vessel and in the central region of the pressure vessel. The second fuel assembly is disposed in the gap between the first fuel assembly and the pressure vessel. The coolant is dispersed inside the pressure vessel.

[0013] The second fuel assembly in the pressurized water reactor fuel assembly of this invention differs from traditional pressurized water reactor fuel assemblies such as square or hexagonal assemblies. It is arranged in an irregular space between the pressure vessel and the traditional first fuel assembly. By making reasonable use of the internal space of the pressure vessel, the fuel loading of the reactor core can be increased without increasing the radius of the pressure vessel, thereby reducing the average power density of the reactor core and improving the safety of the reactor core; it can also increase the core power and improve the economics of the reactor core. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of a traditional small modular reactor core.

[0015] Figure 2 This is a schematic diagram of the small stack core in Embodiment 2 of the present invention.

[0016] Figure 3 This is a schematic diagram of the small stack core in Embodiment 2 of the present invention.

[0017] Figure 4 This is a schematic diagram of the small stack core in Embodiment 2 of the present invention.

[0018] Figure 5 This is a schematic diagram of the structure of the second fuel assembly in Embodiment 2 of the present invention.

[0019] Figure 6 This is a diagram showing the core power distribution of a traditional small modular reactor (SMR).

[0020] Figure 7 This is a power distribution diagram of the small reactor core loaded with an irregularly shaped second fuel assembly in Embodiment 2 of the present invention.

[0021] In the diagram: 1-Second fuel assembly; 2-First fuel assembly; 3-Pressure vessel; 4-Fuel rod; 5-Grid. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] The embodiments of this patent are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this patent, and should not be construed as limiting this patent.

[0024] In the description of this patent, it should be understood that the terms “center,” “upper,” “lower,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this patent 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 patent.

[0025] In the description of this patent, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this patent according to the specific circumstances.

[0026] Example 1

[0027] This embodiment provides a pressurized water reactor fuel assembly, including: a first fuel assembly disposed inside a pressure vessel and in the central region of the pressure vessel; the pressurized water reactor fuel assembly further includes: at least one second fuel assembly disposed in the gap between the first fuel assembly and the pressure vessel.

[0028] This embodiment also provides a pressurized water reactor core, including: a pressurized water reactor fuel assembly, a pressure vessel, and a coolant. The pressurized water reactor fuel assembly is the pressurized water reactor fuel assembly described above. The pressurized water reactor fuel assembly includes: a first fuel assembly and a second fuel assembly. The first fuel assembly is disposed inside the pressure vessel and in the central region of the pressure vessel. The second fuel assembly is disposed in the gap between the first fuel assembly and the pressure vessel. The coolant is dispersed inside the pressure vessel.

[0029] The second fuel assembly in this embodiment of the pressurized water reactor fuel assembly differs from traditional pressurized water reactor fuel assemblies such as square or hexagonal assemblies. It is arranged in an irregular space between the pressure vessel and the traditional first fuel assembly. By making reasonable use of the internal space of the pressure vessel, the fuel loading of the reactor core can be increased without increasing the radius of the pressure vessel, thereby reducing the average power density of the reactor core and improving the safety of the reactor core; it can also increase the core power and improve the economics of the reactor core.

[0030] Example 2

[0031] This embodiment provides a pressurized water reactor fuel assembly, including: a first fuel assembly 2, which is disposed inside a pressure vessel 3 and in the central region of the pressure vessel 3. The pressurized water reactor fuel assembly also includes: at least one second fuel assembly 1, which is disposed in the gap between the first fuel assembly 2 and the pressure vessel 3.

[0032] The pressurized water reactor fuel assembly in this embodiment differs from the conventional tetragonal or hexagonal prism fuel assemblies located in the central region of the pressure vessel. The fuel assembly of the pressurized water reactor core includes: a conventional fuel assembly, namely the first fuel assembly 2; and a second fuel assembly 1 located in the gap between the conventional fuel assembly and the pressure vessel 3. The pressurized water reactor core includes at least one second fuel assembly 1.

[0033] Preferably, the second fuel assembly 1 includes: a fuel rod 4, a grid 5, an upper tube seat, and a lower tube seat. The upper tube seat is located above the fuel rod, the lower tube seat is located below the fuel rod, and the grid 5 is located in the middle of the fuel rod's axial direction. The upper tube seat, the lower tube seat, and the grid 5 serve to fix the fuel rod.

[0034] Preferably, two sides of the cross-section of the second fuel assembly 1 are in contact with the first fuel assembly 2, and the remaining sides of the cross-section of the second fuel assembly 1 are any one of a straight line, an arc, or a broken line. The cross-section of the second fuel assembly 1 is parallel to its bottom surface.

[0035] Preferably, the second fuel assembly 1 has at least one grid 5.

[0036] Preferably, the vertical projection view of the second fuel assembly 1 is within the inner diameter range of the pressure vessel 3, and the cross-sectional area of ​​the second fuel assembly 1 is smaller than the cross-sectional area of ​​the first fuel assembly 2. The cross-section of the second fuel assembly 1 is parallel to its bottom surface, and the cross-section of the first fuel assembly 2 is parallel to its bottom surface.

[0037] The present invention also provides a pressurized water reactor core, comprising: a pressurized water reactor fuel assembly, a pressure vessel 3, and a coolant. The pressurized water reactor fuel assembly is the pressurized water reactor fuel assembly described above, and the pressurized water reactor fuel assembly includes: a first fuel assembly 2 and a second fuel assembly 1. The first fuel assembly 2 is disposed inside the pressure vessel 3 and in the central region of the pressure vessel 3. The second fuel assembly 1 is disposed in the gap between the first fuel assembly 2 and the pressure vessel 3. The coolant is dispersed inside the pressure vessel 3.

[0038] The second fuel assembly 1 is arranged in the irregular space between the pressure vessel 3 and the conventional first fuel assembly 2, without increasing the size of the pressure vessel 3 or reducing the original minimum distance between the first fuel assembly 2 and the pressure vessel 3. The cross-sectional shape of the second fuel assembly 1 is as follows: the two sides of the transverse section perpendicular to the axial direction near the first fuel assembly 2 are straight segments at a 90-degree angle to each other, and the other line segments that make up the cross-section are straight segments, broken line segments, and curved segments that do not exceed the inner diameter of the pressure vessel 3.

[0039] This embodiment can increase the number of fuel rods without increasing the radius of the pressure vessel, thereby reducing the average linear power density of the reactor core and improving both economy and safety.

[0040] This embodiment increases the core equivalent radius, making it easier to flatten the core power peak and further increasing safety.

[0041] This embodiment reduces the core neutron leakage rate and extends the core lifespan.

[0042] This embodiment does not reduce the minimum distance between the core pressure vessel 3 and the fuel assembly, so the impact on the irradiation of the pressure vessel 3 is minimal.

[0043] Specifically, this embodiment takes a small reactor with 57 fuel cores as an example. The traditional core arrangement is as follows: Figure 1 As shown, there is an irregular space between the first fuel assembly 2 and the pressure vessel 3 in the reactor core. This space cannot accommodate conventional fuel assemblies, rendering it unusable. The second fuel assembly 1 for a pressurized water reactor described in this invention can have various cross-sectional shapes. Its two sides closest to the reactor core are straight segments forming a 90-degree angle. The other line segments constituting this cross-section can be:

[0044] It can be a straight line segment that forms a triangle, such as Figure 2 As shown.

[0045] It can be composed of line segments, forming polygons, such as... Figure 3 As shown;

[0046] These can be curved segments, forming sector shapes and other geometric shapes not exceeding 3 mm of the pressure vessel's inner diameter, such as... Figure 4 As shown.

[0047] Taking the triangular irregular second fuel assembly 1 as an example, the reactor core loading the triangular irregular second fuel assembly 1 is as follows: Figure 2 As shown. The fuel rods of the second fuel assembly 1 are as follows. Figure 5 As shown, some fuel rods can be replaced with guide tubes or instrument tubes according to design requirements. After loading the irregularly shaped second fuel assembly 1, the number of fuel rods in the core increases from the original 15,048 to 16,680, an increase of 10.85%. This means that the average core power is reduced by 10%, but a 10% margin is added; or, while maintaining the original line power level, the core power level can be increased by 10%, increasing economic efficiency by 10%.

[0048] Furthermore, loading the irregularly shaped second fuel assembly 1 will bring even more advantages:

[0049] The reactor core is larger than before, making it easier to flatten the core power and reduce the power peak factor. For example... Figure 6 and Figure 7 As shown.

[0050] It has a lower core leakage rate, better fuel economy, and can extend core life.

[0051] The minimum distance between the core pressure vessel 3 and the first fuel assembly 2 was not reduced, so the impact on the irradiation of the pressure vessel 3 was minimal.

[0052] The above only uses small reactors as an example. The irregular second fuel assembly 1 described in this patent can be used in more pressurized water reactor types such as M310 and Hualong. Especially in annular fuel cores, since the fuel loading of the first fuel assembly 2 in annular cores is reduced, the use of this invention can increase fuel loading, reduce linear power density, increase power, and extend core life, that is, improve safety and economy.

[0053] In this embodiment, the second fuel assembly 1 of the pressurized water reactor fuel assembly differs from conventional pressurized water reactor fuel assemblies such as square or hexagonal assemblies. It is arranged in the irregular space between the pressure vessel 3 and the conventional first fuel assembly 2. By making reasonable use of the internal space of the pressure vessel 3, the fuel loading of the reactor core can be increased without increasing the radius of the pressure vessel 3, thereby reducing the average power density of the reactor core and improving the safety of the reactor core; it can also increase the core power and improve the economics of the reactor core.

[0054] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A pressurized water reactor fuel assembly, comprising: The first fuel assembly is disposed within a pressure vessel and in the central region of the pressure vessel, characterized in that the pressurized water reactor fuel assembly further includes: at least one second fuel assembly disposed in the gap between the first fuel assembly and the pressure vessel.

2. The pressurized water reactor fuel assembly according to claim 1, characterized in that, The second fuel assembly includes: a fuel rod, a grid, an upper tube seat, and a lower tube seat. The upper tube seat is located above the fuel rod, the lower tube seat is located below the fuel rod, and the grid is located in the middle of the fuel rod's axial direction.

3. The pressurized water reactor fuel assembly according to claim 2, characterized in that, The second fuel assembly has at least one grid.

4. The pressurized water reactor fuel assembly according to claim 1, characterized in that, Two sides of the cross-section of the second fuel assembly are in contact with the first fuel assembly, and the remaining sides of the cross-section of the second fuel assembly are any one of a straight line, an arc, or a broken line.

5. The pressurized water reactor fuel assembly according to claim 1, characterized in that, The vertical projection view of the second fuel assembly is within the inner diameter of the pressure vessel, and the cross-sectional area of ​​the second fuel assembly is smaller than that of the first fuel assembly.

6. A pressurized water reactor core, characterized in that, include: The pressurized water reactor fuel assembly, pressure vessel, and coolant are provided. The pressurized water reactor fuel assembly is the pressurized water reactor fuel assembly as described in any one of claims 1 to 5. The pressurized water reactor fuel assembly includes a first fuel assembly and a second fuel assembly. The first fuel assembly is disposed inside the pressure vessel and in the central region of the pressure vessel. The second fuel assembly is disposed in the gap between the first fuel assembly and the pressure vessel. The coolant is dispersed inside the pressure vessel.

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