Hexagonal fuel assembly for a nuclear reactor

Abstract

The application relates to the technical field of nuclear fuel assemblies, and particularly discloses a hexagonal fuel assembly for a heat supply reactor, wherein the upper end plane of an upper pressing spring is in contact with a pressing plate at the uppermost end of a hexagonal upper tube seat, the pressing plate is in contact with an upper grid plate of a reactor core, the upper pressing spring is sleeved outside a control rod guide tube, the lower end of the upper pressing spring is in abutment against a bottom plate of the hexagonal upper tube seat, and the upper pressing spring can axially press the hexagonal upper tube seat and components below the hexagonal upper tube seat; the lower end plane of a lower pressing spring is in contact with a pressing plate at the lowermost end of a hexagonal lower tube seat, the pressing plate is in contact with a lower grid plate of the reactor core, the lower pressing spring is sleeved outside the control rod guide tube, the upper end of the lower pressing spring is in abutment against a bottom plate of the hexagonal lower tube seat, and the lower pressing spring can axially support the hexagonal lower tube seat and components above the hexagonal lower tube seat. When an earthquake occurs, the vibration of the reactor core transmitted to the fuel assembly of the application can be absorbed by the upper pressing spring and the lower pressing spring, so that the anti-seismic performance of the whole assembly under the earthquake condition is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of nuclear fuel assembly technology, specifically relating to a hexagonal fuel assembly for a heated reactor. Background Technology

[0002] Nuclear energy, as a safe and clean energy source, is one of the more mature methods for replacing primary energy sources. Extensive research has been conducted on using nuclear energy for district heating. Compared with traditional heat sources, it can reduce pollution emissions and ensure heating safety. This will effectively improve my country's energy structure, alleviate the increasingly serious energy supply shortage, and has positive significance for protecting the environment, protecting public health, and easing the pressure on coal transportation.

[0003] During the operation of a nuclear power plant reactor, the performance of nuclear fuel is a crucial factor affecting reactor safety and economics. Therefore, international research on fuel elements has always been given high priority. Through optimizing fuel element design, adopting advanced structural materials, and improving element manufacturing processes, the various performance characteristics of nuclear fuel elements are continuously improved, promoting the development of nuclear power towards a safer and more economical direction. For large pressurized water reactor fuel assemblies, the seismic resistance requirement is generally 0.3g acceleration. However, for heated reactor fuel assemblies with a wider site selection range, to adapt to various site selection ranges, the seismic resistance requirement is higher, at 0.6g acceleration.

[0004] Therefore, it is necessary to design a new hexagonal fuel assembly that has advantages over traditional square fuel assemblies in terms of overall structural seismic performance and component stability, in order to meet the requirements of heating reactors for fuel assemblies. Summary of the Invention

[0005] The purpose of this invention is to provide a hexagonal fuel assembly for a heating reactor, which can improve the seismic performance of the fuel assembly.

[0006] The technical solution of the present invention is as follows:

[0007] A hexagonal fuel assembly for a heating reactor includes a lower compression spring, a hexagonal lower tube seat, a positioning grid, an annular fuel rod, a hexagonal upper tube seat, an upper compression spring, and a control rod guide tube;

[0008] The hexagonal upper tube seat and the hexagonal lower tube seat are respectively connected to the upper and lower ends of the control rod guide tube;

[0009] The positioning grid is welded onto the control rod guide tube;

[0010] The annular fuel rod is inserted into the grid cell of the positioning grid and held by the grid cell spring. The lower end plug of the annular fuel rod is fixed on the hexagonal lower tube seat, while the upper end plug is in a free and relaxed state.

[0011] The upper end of the upper compression spring contacts the uppermost compression plate of the hexagonal upper tube seat, the compression plate contacts the upper grid plate of the core, the upper compression spring is sleeved outside the control rod guide tube, and the lower end of the upper compression spring presses against the bottom plate of the hexagonal upper tube seat, which can exert an axial compression effect on the hexagonal upper tube seat and its components below it.

[0012] The lower end of the lower clamping spring contacts the clamping plate at the bottom of the hexagonal lower tube seat. The clamping plate contacts the lower grid plate of the core. The lower clamping spring is sleeved outside the control rod guide tube. The upper end of the lower clamping spring rests on the bottom plate of the hexagonal lower tube seat, which can provide axial support for the hexagonal lower tube seat and the components above it.

[0013] The positioning grid is hexagonal in shape and consists of an outer strip and triangular grid elements;

[0014] Among them, the triangular grid elements are welded together to form a hexagonal egg-shaped structure, and the outer strip is welded around the egg-shaped structure.

[0015] The hexagonal upper pipe seat and hexagonal lower pipe seat respectively include a hexagonal flow divider plate, a side rib plate, and a sleeve.

[0016] The hexagonal lower tube seat and the hexagonal upper tube seat have the same structure but opposite directions.

[0017] The diameter of the control rod guide tube is 1.1-1.5 times the diameter of the square fuel assembly guide tube.

[0018] In the relaxed state, the upper end of the upper compression spring and the position of the clamping plate of the hexagonal upper tube seat extend beyond the upper end of the control rod guide tube;

[0019] In the compressed state, the upper grid plate of the reactor core presses against the upper plane of the clamping plate until the upper end of the clamping plate and the upper end of the upper clamping spring are flush with the upper end of the control rod guide tube.

[0020] In the relaxed state, the lower end of the lower compression spring and the clamping plate of the hexagonal lower tube seat extend beyond the lower end of the control rod guide tube;

[0021] In the compressed state, the lower grid plate of the reactor core is pressed onto the lower end plane of the clamping plate until the lower end of the clamping plate and the lower end of the lower clamping spring are flush with the lower end of the control rod guide tube.

[0022] Both the upper and lower compression springs are long cylindrical springs.

[0023] The number of annular fuel rods is determined by thermophysical calculations after the cross-sectional area of ​​the hexagonal fuel assembly and the cross-sectional area of ​​the annular fuel rods are determined.

[0024] The number of control rod guide tubes is the same as the number of control rods, and the number of control rods is obtained based on physical calculations.

[0025] Suitable for heating reactors, meeting the seismic resistance requirement of 0.6g acceleration.

[0026] The significant advantages of this invention are:

[0027] (1) The hexagonal fuel assembly of the present invention, through the action of elastic elements such as upper and lower compression springs, allows the vibration transmitted from the reactor core to the fuel assembly to be partially absorbed by the upper and lower compression springs during an earthquake, thereby improving the seismic performance of the entire assembly under earthquake conditions.

[0028] (2) The control rod guide tube of the hexagonal fuel assembly of the present invention has a large diameter, thick wall and high strength, which can ensure the smooth insertion of the control assembly in case of an accident and achieve safe shutdown.

[0029] (3) In addition to the compression spring, the hexagonal fuel assembly of the present invention also uses a hexagonal upper tube seat, a positioning grid, a hexagonal lower tube seat, etc., which can achieve uniform symmetry of the assembly structure and ensure the replaceability of the fuel assembly in various parts of the reactor core.

[0030] (4) In terms of the unit cross section of the fuel assembly, the hexagonal fuel assembly of the present invention has more and denser fuel rods than the quadrilateral fuel assembly of the traditional pressurized water reactor. Since the fuel rods themselves are also an important component of the strength of the fuel assembly, the hexagonal fuel assembly has greater strength than the quadrilateral fuel assembly under the same conditions. Attached Figure Description

[0031] Figure 1 The example shows a hexagonal fuel assembly with 157 fuel rods.

[0032] In the diagram: 1. Hexagonal upper tube seat, 2. Upper compression spring, 3. Hexagonal lower tube seat, 4. Lower compression spring, 5. Positioning grid, 6. Annular fuel rod, 7. Control rod guide tube. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] A hexagonal fuel assembly for a heating reactor includes a lower compression spring, a hexagonal lower tube seat, a positioning grid, an annular fuel rod, a hexagonal upper tube seat, an upper compression spring, and a control rod guide tube.

[0035] The hexagonal upper tube seat is composed of components such as a hexagonal diversion plate, side ribs, and sleeve. The hexagonal lower tube seat has the same structure as the hexagonal upper tube seat but is oriented in the opposite direction.

[0036] Both the upper and lower compression springs are long cylindrical springs.

[0037] The positioning grid is hexagonal in shape and consists of an outer strip and triangular grid elements. The triangular grid elements are welded together to form a hexagonal egg-shaped structure, and the outer strip is welded around the egg-shaped structure.

[0038] An annular fuel rod is a fuel rod with upper and lower end plugs, inner and outer shells, and an annular core.

[0039] The control rod guide tube is a hollow tube, with a larger diameter than that of the square fuel assembly guide tube, which can be 1.1-1.5 times the diameter of the square fuel assembly guide tube. It also has a thicker wall and higher strength.

[0040] The hexagonal upper tube seat and hexagonal lower tube seat are connected to the upper and lower ends of the control rod guide tube, respectively; the positioning grid is welded to the control rod guide tube, and the positioning grid, together with the hexagonal upper tube seat, the hexagonal lower tube seat, and the control rod guide tube, form the fuel skeleton; the annular fuel rod is inserted into the grid cell of the positioning grid and is held by the grid cell spring; the lower end plug of the annular fuel rod is fixed to the hexagonal lower tube seat through the lower end plug connector, and the upper end plug is in a free and relaxed state.

[0041] The upper end of the upper clamping spring contacts the circular perforated clamping plate at the top of the hexagonal upper tube seat. The clamping plate contacts the upper grid plate of the reactor core. The inner ring of the upper clamping spring contacts the outer wall of the control rod guide tube. The lower end of the upper clamping spring rests on the bottom plate of the hexagonal upper tube seat, providing axial clamping for the hexagonal upper tube seat and its components below. In the relaxed state, the upper end of the upper clamping spring and the clamping plate of the hexagonal upper tube seat extend beyond the upper end of the control rod guide tube. In the clamped state, the upper grid plate of the reactor core presses against the upper end plane of the clamping plate until the upper end of the clamping plate and the upper end of the upper clamping spring are flush with the upper end of the control rod guide tube.

[0042] The lower end of the lower clamping spring contacts the circular perforated clamping plate at the bottom of the hexagonal lower tube seat. The clamping plate contacts the lower grid plate of the reactor core. The inner ring of the lower clamping spring contacts the outer wall of the control rod guide tube. The upper end of the lower clamping spring rests on the bottom plate of the hexagonal lower tube seat, providing axial support for the hexagonal lower tube seat and the components above it. In the relaxed state, the lower end of the lower clamping spring and the clamping plate of the hexagonal lower tube seat extend beyond the lower end of the control rod guide tube. In the clamped state, the lower grid plate of the reactor core presses against the lower end plane of the clamping plate until the lower end of the clamping plate and the lower end of the lower clamping spring are flush with the lower end of the control rod guide tube.

[0043] Because the upper and lower clamping springs are respectively fitted outside the control rod guide tube, the guiding effect of the outer wall of the control rod guide tube prevents radial displacement under vibration, resulting in only slight axial vibration. At the same time, the inner wall of the control rod guide tube also guides the control rod assembly inside the reactor, ensuring smooth insertion of the control rods in the event of an accident and achieving safe reactor shutdown.

[0044] The hexagonal fuel assembly of this invention is suitable for reactors with higher requirements for the seismic performance of fuel assemblies, such as heating reactors, where the seismic resistance requirement is generally 0.6g acceleration, which is much higher than the 0.3g seismic resistance requirement of large commercial pressurized water reactors.

[0045] Example

[0046] like Figure 1 The hexagonal fuel assembly for a heating reactor shown comprises a hexagonal upper tube seat 1, an upper compression spring 2, a hexagonal lower tube seat 3, a lower compression spring 4, a positioning grid 5, 157 annular fuel rods 6, and 12 control rod guide tubes 7; or, it comprises a hexagonal upper tube seat 1, an upper compression spring 2, a hexagonal lower tube seat 3, a lower compression spring 4, a positioning grid 5, 56 annular fuel rods 6, and 6 control rod guide tubes 7.

[0047] The number of annular fuel rods 6 is obtained through a series of thermophysical calculations after the cross-sectional area of ​​the hexagonal fuel assembly and the cross-sectional area of ​​the annular fuel rods 6 are determined; the number of control rods is obtained according to physical calculations, and the number of control rod guide tubes 7 is consistent with the number of control rods.

[0048] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A hexagonal fuel assembly for a heating reactor, characterized in that: Includes a lower clamping spring, a hexagonal lower tube seat, a positioning grid, an annular fuel rod, a hexagonal upper tube seat, an upper clamping spring, and a control rod guide tube; The hexagonal upper tube seat and the hexagonal lower tube seat are respectively connected to the upper and lower ends of the control rod guide tube; The positioning grid is welded onto the control rod guide tube; The annular fuel rod is inserted into the grid cell of the positioning grid and held by the grid cell spring. The lower end plug of the annular fuel rod is fixed on the hexagonal lower tube seat, while the upper end plug is in a free and relaxed state. The upper end of the upper compression spring contacts the uppermost compression plate of the hexagonal upper tube seat, the compression plate contacts the upper grid plate of the core, the upper compression spring is sleeved outside the control rod guide tube, and the lower end of the upper compression spring presses against the bottom plate of the hexagonal upper tube seat, which can exert an axial compression effect on the hexagonal upper tube seat and its components below it. The lower end of the lower clamping spring contacts the clamping plate at the bottom of the hexagonal lower tube seat. The clamping plate contacts the lower grid plate of the core. The lower clamping spring is sleeved outside the control rod guide tube. The upper end of the lower clamping spring rests on the bottom plate of the hexagonal lower tube seat, which can provide axial support for the hexagonal lower tube seat and the components above it. The diameter of the control rod guide tube is 1.1-1.5 times the diameter of the square fuel assembly guide tube.

2. The hexagonal fuel assembly for a heating reactor as described in claim 1, characterized in that: The positioning grid is hexagonal in shape and consists of an outer strip and triangular grid elements; Among them, the triangular grid elements are welded together to form a hexagonal egg basket-shaped structure, and the outer strip is welded around the egg basket-shaped structure.

3. The hexagonal fuel assembly for a heating reactor as described in claim 1, characterized in that: The hexagonal upper pipe seat and hexagonal lower pipe seat respectively include a hexagonal flow divider plate, a side rib plate, and a sleeve.

4. The hexagonal fuel assembly for a heating reactor as described in claim 3, characterized in that: The hexagonal lower tube seat and the hexagonal upper tube seat have the same structure but opposite directions.

5. A hexagonal fuel assembly for a heating reactor as described in claim 1, characterized in that: In the relaxed state, the upper end of the upper compression spring and the position of the clamping plate of the hexagonal upper tube seat extend beyond the upper end of the control rod guide tube; In the compressed state, the upper grid plate of the reactor core presses against the upper plane of the clamping plate until the upper end of the clamping plate and the upper end of the upper clamping spring are flush with the upper end of the control rod guide tube.

6. The hexagonal fuel assembly for a heating reactor as described in claim 1, characterized in that: In the relaxed state, the lower end of the lower compression spring and the clamping plate of the hexagonal lower tube seat extend beyond the lower end of the control rod guide tube; In the compressed state, the lower grid plate of the reactor core is pressed onto the lower end plane of the clamping plate until the lower end of the clamping plate and the lower end of the lower clamping spring are flush with the lower end of the control rod guide tube.

7. A hexagonal fuel assembly for a heating reactor as described in claim 1, characterized in that: Both the upper and lower compression springs are long cylindrical springs.

8. A hexagonal fuel assembly for a heating reactor as described in claim 1, characterized in that: The number of annular fuel rods is determined by thermophysical calculations after the cross-sectional area of ​​the hexagonal fuel assembly and the cross-sectional area of ​​the annular fuel rods are determined. The number of control rod guide tubes is the same as the number of control rods, and the number of control rods is obtained based on physical calculations.

9. A hexagonal fuel assembly for a heating reactor as described in any one of claims 1 to 8, characterized in that: Suitable for heating reactors, meeting the seismic resistance requirement of 0.6g acceleration.

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