High temperature gas cooled reactor core structure with high thermal power

Abstract

The application belongs to the technical field of high temperature reactor, and discloses a high temperature gas cooled reactor core structure with high heat power, wherein a graphite shell and a support are arranged in a reactor core shell, the support is installed at the bottom of the reactor core shell, the graphite shell is fixed to the support, fuel balls are filled in the graphite shell from top to bottom, the fuel balls are stacked to form a pebble bed core, the graphite shell and the inner wall of the reactor core shell cooperate to form a flow cavity, the flow cavity is communicated with the bottom of the graphite shell, a coolant inlet communicated with the flow cavity is arranged in the upper region of the reactor core shell, and a coolant outlet communicated with the outside is arranged in the upper region of the graphite shell; the coolant flows into the flow cavity through the coolant inlet, flows upward in the graphite shell, and flows from top to bottom, and the fuel balls flow from bottom to top, so that the neutron flux in the place where the upper part of fissile nuclides is accumulated more is reduced through temperature negative feedback, the axial power density distribution is flattened, the power density peak value and the highest fuel temperature after the accident are reduced, and the core heat power is improved under the premise of meeting the safety limit.

Description

Technical Field

[0001] This invention relates to the field of high-temperature reactor technology, and in particular to a high-temperature gas-cooled reactor core structure with high thermal power. Background Technology

[0002] As an advanced representative of fourth-generation nuclear power technology, the pebble bed high-temperature gas-cooled reactor (PTC) boasts excellent safety, high power generation efficiency, strong environmental adaptability, and wide applicability, with broad prospects for commercial application in nuclear power generation, combined heat and power (CHP), and high-temperature process heat. The Pebble bed PTC uses a coolant, a graphite moderator, and coated particulate fuel elements. Graphite components are stacked into a cylindrical cavity, within which flowable spherical fuel elements are deposited, forming the "pebble bed" active region.

[0003] In existing pebble bed high-temperature gas-cooled reactor designs, the coolant inlet is located at the bottom of the core shell. After flowing around the bottom, it enters the cold helium rising channel in the graphite bricks and flows into the cold helium header above the active zone for mixing. Helium flows from the top through the pebble bed core to the bottom, is heated, and then flows into the hot helium header below the active zone for mixing before reaching the hot helium outlet at the bottom of the core shell. Both fuel spheres and coolant flow from top to bottom. The fuel elements with shallow burnup and the coolant with lower temperatures are located in the upper and middle parts of the core. Due to the strong temperature negative feedback effect of high-temperature gas-cooled reactors (higher temperatures result in lower power, and vice versa), peak neutron flux and power density will appear in the upper and middle parts of the core. The peak power density is strongly positively correlated with the safety limit after a loss of cooling and depressurization accident—the maximum fuel temperature. When the peak power density is high, the maximum fuel temperature after the accident will also increase accordingly. Once the limit is exceeded, it will endanger the safety of the reactor. Therefore, it is necessary to limit the peak power density to avoid exceeding the maximum fuel temperature limit after an accident, thus limiting the core thermal power. Summary of the Invention

[0004] The purpose of this invention is to provide a high-temperature gas-cooled reactor core structure with high thermal power, thereby improving the core thermal power while ensuring safety.

[0005] To achieve this objective, the present invention adopts the following technical solution: A high-temperature gas-cooled reactor core structure with high thermal power includes a core shell. Inside the core shell, a graphite shell and a support are disposed. The support is installed at the bottom of the core shell, and the graphite shell is fixed to the support. Fuel pellets flow and fill from top to bottom inside the graphite shell, and the fuel pellets accumulate to form a pebble bed core. The graphite shell and the inner wall of the core shell cooperate to form a flow cavity, which connects to the bottom of the graphite shell. A coolant inlet communicating with the flow cavity is provided in the upper region of the core shell, and a coolant outlet communicating with the outside is provided in the upper region of the graphite shell.

[0006] Preferably, the support includes a flow equalization plate with evenly distributed flow distribution holes, the flow equalization plate separating the flow cavity, and the plane of the flow equalization plate facing the coolant inlet.

[0007] Preferably, the two side walls of the flow equalization plate are respectively attached to and fixed to the inner walls of the opposite sides of the core shell, the bottom wall of the flow equalization plate is attached to and fixed to the bottom wall of the core shell, and the top wall of the flow equalization plate is attached to and fixed to the bottom wall of the graphite shell.

[0008] Preferably, the support includes two flow equalization plates arranged opposite each other, which cooperate with the bottom wall of the core shell and the bottom wall of the graphite shell to form a flow equalization cavity.

[0009] Preferably, the bottom of the graphite shell has a plurality of channels pre-set, and the channels are connected to the flow equalization cavity.

[0010] Preferably, the reactor also includes an inlet pipe and an outlet pipe, wherein the inlet pipe is installed in the reactor core shell and connected to the coolant inlet, and the outlet pipe passes through the reactor core shell and is connected to the coolant outlet.

[0011] Preferably, the outlet pipe is coaxially sleeved inside the inlet pipe.

[0012] Preferably, an installation hole is provided in the upper region of the core shell, and the inlet pipe is sealed and inserted into the installation hole.

[0013] Preferably, the system also includes an inlet tube and an outlet tube, wherein one end of the inlet tube is connected to the top of the graphite shell and the other end passes through the top of the core shell, and one end of the outlet tube is connected to the bottom of the graphite shell and the other end passes through the bottom of the core shell.

[0014] Preferably, the ball inlet pipe and the ball unloading pipe are centrally located at the upper and lower parts of the ball bed core, respectively.

[0015] The beneficial effects of this invention are: This invention provides a high-temperature gas-cooled reactor core structure with high thermal power, including a core shell, a graphite shell and a support member disposed inside the core shell, the support member being installed at the bottom of the core shell, the graphite shell being fixed to the support member, fuel balls flowing and filling the interior of the graphite shell from top to bottom, the fuel balls accumulating to form a pebble bed core, the graphite shell and the inner wall surface of the core shell fitting together to form a flow cavity, the flow cavity being connected to the bottom of the graphite shell, a coolant inlet connected to the flow cavity being opened in the upper region of the core shell, and a coolant outlet connected to the outside being being opened in the upper region of the graphite shell; The fuel spheres flow from top to bottom, while the coolant flows from bottom to top. The flow direction of the fuel spheres is opposite to that of the coolant. This results in a higher coolant temperature in the upper part of the pebble bed core where burnup is shallow. Through temperature negative feedback, the neutron flux in the upper part where fissile nuclides accumulate more is reduced, the axial power density distribution is flattened, and the peak power density is reduced. The highest fuel temperature after an accident is also reduced accordingly. Thus, the core thermal power can be increased while meeting safety limits, thereby improving the reactor's economics. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the high-temperature gas-cooled reactor core structure with high thermal power provided in the embodiments of the present invention. Figure 1 ; Figure 2 This is a schematic diagram of the high-temperature gas-cooled reactor core structure with high thermal power provided in the embodiments of the present invention. Figure 2 ; Figure 3 This is a schematic diagram (radial center) showing the flattened comparison of the axial power density distribution of the reactor core provided in an embodiment of the present invention. Figure 4 This is a comparison chart of the highest fuel temperature after an accident, provided in an embodiment of the present invention.

[0017] In the picture: 1. Core shell; 10. Flow chamber; 101. Flow equalization chamber; 11. Coolant inlet; 2. Graphite shell; 21. Coolant outlet; 3. Fuel ball; 4. Flow equalization plate; 41. Flow divider; 5. Inlet pipe; 6. Outlet pipe; 7. Inlet pipe; 8. Outlet pipe. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0019] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0021] In the description of this embodiment, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, 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 the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0022] In existing pebble bed high-temperature gas-cooled reactor designs, the coolant inlet is located at the bottom of the core shell. After flowing around the bottom, it enters the cold helium rising channel in the graphite bricks and flows into the cold helium header above the active zone for mixing. Helium flows from the top through the pebble bed core to the bottom, is heated, and then flows into the hot helium header below the active zone for mixing before reaching the hot helium outlet at the bottom of the core shell. Both fuel spheres and coolant flow from top to bottom. The fuel elements with shallow burnup and the coolant with lower temperatures are located in the upper and middle parts of the core. Due to the strong temperature negative feedback effect of high-temperature gas-cooled reactors (higher temperatures result in lower power, and vice versa), peak neutron flux and power density will appear in the upper and middle parts of the core. The peak power density is strongly positively correlated with the safety limit after a loss of cooling and depressurization accident—the maximum fuel temperature. When the peak power density is high, the maximum fuel temperature after the accident will also increase accordingly. Once the limit is exceeded, it will endanger the safety of the reactor. Therefore, it is necessary to limit the peak power density to avoid exceeding the maximum fuel temperature limit after an accident, thus limiting the core thermal power.

[0023] Therefore, this embodiment provides a high-temperature gas-cooled reactor core structure with high thermal power. It utilizes the temperature negative feedback effect to flatten the core power distribution, reduce the peak power density, and correspondingly reduce the highest fuel temperature after an accident. This allows the core thermal power to be increased while meeting safety limits, thereby improving the reactor's economic efficiency.

[0024] like Figure 1As shown, the high-temperature gas-cooled reactor core structure with high thermal power provided in this embodiment includes a core shell 1. The interior of the core shell 1 is formed by stacking graphite bricks in a ring to form a cylindrical cavity, forming a graphite shell 2. Fuel balls 3 flow and fill the interior of the graphite shell 2 from top to bottom. The fuel balls 3 are stacked to form a pebble bed core. That is, the fuel balls 3 are filled from the top of the graphite shell 2 and move downward by gravity. After reaching the bottom of the graphite shell 2, they leave. The graphite shell 2 and the inner wall of the core shell 1 cooperate to form a flow cavity 10. The flow cavity 10 is connected to the bottom of the graphite shell 2. A coolant outlet 21 is opened in the upper region of the graphite shell 2 to connect to the outside. A coolant inlet 11 is opened in the upper region of the core shell 1 to connect to the flow cavity 10. The coolant flows into the flow cavity 10 through the coolant inlet 11 and flows downward along the flow cavity 10 to the bottom of the graphite shell 2. Inside the graphite shell 2, it flows upward to carry away the heat of the pebble bed core and flows out through the coolant outlet 21.

[0025] With the above configuration, fuel spheres 3 flow from top to bottom, while the coolant flows from bottom to top. The flow direction of fuel spheres 3 is opposite to that of the coolant, achieving a higher coolant temperature in the upper part of the pebble bed core where burnup is shallow. This temperature negative feedback reduces the neutron flux in the upper part where fissile nuclides accumulate more. (See also...) Figure 3 In this scheme, the axial power density distribution is flattened, the peak power density is reduced, and the highest fuel temperature after an accident is also reduced accordingly. This can increase the core thermal power and improve the reactor's economics while meeting safety limits.

[0026] Preferably, helium can be used as the coolant.

[0027] like Figure 1 As shown, in some feasible embodiments, a support member is provided inside the core shell 1. The support member is installed at the bottom of the core shell 1, and the graphite shell 2 is fixed to the support member. The support member supports the graphite shell 2 to ensure the stability of the graphite shell 2.

[0028] For example, such as Figure 1 and Figure 2 As shown, the support includes a flow equalization plate 4 with evenly distributed flow distribution holes 41. The flow equalization plate 4 can divide the flow cavity 10, and the plane of the flow equalization plate 4 is positioned directly opposite the coolant inlet 11. Through this arrangement, the coolant entering through the coolant inlet 11 can be evenly distributed through the flow distribution holes 41 on the flow equalization plate 4 during its flow process, ensuring uniform distribution of the coolant inside the graphite shell 2. This guarantees that the coolant can uniformly cool the pebble bed core, improving the temperature uniformity of the pebble bed core.

[0029] Preferably, the two side walls of the flow equalization plate 4 are respectively attached to and fixed to the inner walls of the opposite sides of the core shell 1, the bottom wall of the flow equalization plate 4 is attached to and fixed to the bottom wall of the core shell 1, and the top wall of the flow equalization plate 4 is attached to and fixed to the bottom wall of the graphite shell 2. That is, there is no gap between the edge of the flow equalization plate 4 and the cavity wall of the flow cavity 10, ensuring that the flow equalization plate 4 can separate the flow cavity 10.

[0030] More preferably, the support includes two flow equalization plates 4 arranged opposite each other. By setting two flow equalization plates 4, the flow equalization effect of the coolant is further improved.

[0031] In this embodiment, several channels are pre-set at the bottom of the graphite shell 2, and two flow equalization plates 4 cooperate with the bottom wall of the core shell 1 and the bottom wall of the graphite shell 2 to form a flow equalization cavity 101. The channels are connected to the flow equalization cavity 101. The coolant flows into the flow cavity 10 through the coolant inlet 11 and flows downward along the flow cavity 10. After being equalized by the flow equalization plates 4, it enters the flow equalization cavity 101 located at the bottom of the graphite shell 2, and then flows into the interior of the graphite shell 2 through the channels.

[0032] The above settings ensure that all coolant entering the graphite shell 2 undergoes flow equalization treatment by the flow equalization plate 4.

[0033] Preferably, a number of channels are evenly spaced to further ensure that the coolant is evenly distributed inside the graphite shell 2 and improve the temperature uniformity of the pebble bed core.

[0034] Furthermore, this embodiment also includes an inlet pipe 5 and an outlet pipe 6. The inlet pipe 5 is installed on the core shell 1 and is connected to the coolant inlet 11. Preferably, one end of the inlet pipe 5 is sealed and connected to the coolant inlet 11. The outlet pipe 6 passes through the core shell 1 and is connected to the coolant outlet 21. Preferably, one end of the outlet pipe 6 is sealed and connected to the coolant outlet 21.

[0035] For example, an installation hole is provided in the upper region of the core shell 1, and one end of the inlet pipe 5 is inserted into the installation hole and sealed to the coolant outlet 21. Preferably, the outer wall of the inlet pipe 5 is circumferentially sealed to the wall of the installation hole by a sealing structure. More preferably, the sealing structure can be a high-temperature resistant sealing ring.

[0036] In some feasible embodiments, the outlet pipe 6 is coaxially sleeved inside the inlet pipe 5, and the outlet pipe 6 and the inlet pipe 5 cooperate to form a sleeve structure.

[0037] Furthermore, this embodiment also includes an inlet pipe 7 and an outlet pipe 8. One end of the inlet pipe 7 is connected to the top of the graphite shell 2, and the other end penetrates the top of the core shell 1. One end of the outlet pipe 8 is connected to the bottom of the graphite shell 2, and the other end penetrates the bottom of the core shell 1. The fuel balls 3 are filled from above the graphite shell 2 through the inlet pipe 7 and move downwards by gravity. After reaching the bottom of the graphite shell 2, they can leave through the outlet pipe 8.

[0038] Optionally, the infeed pipe 7 and the unfeed pipe 8 are respectively centrally located at the upper and lower parts of the pebble bed core to ensure that the fuel balls 3 that make up the pebble bed core are always evenly distributed.

[0039] As an envelope accident in the safety analysis of high-temperature gas-cooled reactors, the maximum fuel temperature after a decooling and depressurization accident is usually used as one of the important indicators for evaluating reactor safety, with a design limit of 1620℃. The maximum fuel temperature after the accident shows a strong positive correlation with the peak power density of the reactor. Therefore, a lower peak power density provides a considerable margin for the maximum fuel element temperature, a key indicator after a decooling and depressurization accident.

[0040] like Figure 4 As shown: In the existing scheme, the core thermal power is set at 250MW, and the maximum fuel temperature after the accident is 1535.8℃; In the scheme provided in this embodiment, the core thermal power is set to 250MW, and the highest fuel temperature after the accident is 1360.1℃, which is a significant reduction in the highest fuel temperature after the accident.

[0041] In the scheme provided in this embodiment, the core thermal power is further set to 350MW, and the highest fuel temperature after the accident is 1578.2℃, which is still lower than the design limit of 1620℃.

[0042] This embodiment sets the fuel spheres 3 to flow from top to bottom and the coolant to flow from bottom to top, with the flow direction of the fuel spheres 3 being opposite to that of the coolant. This achieves a higher coolant temperature in the upper part of the pebble bed core where burnup is shallow. Through temperature negative feedback, the neutron flux in the upper part where fissile nuclides accumulate more is reduced, thereby flattening the axial power density distribution, reducing the peak power density, and correspondingly reducing the highest fuel temperature after an accident. This can increase the core thermal power while meeting safety limits and improve the reactor's economics.

[0043] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A high-temperature gas-cooled reactor core structure with high thermal power, characterized in that, The reactor includes a core shell (1), inside which a graphite shell (2) and a support are disposed. The support is installed at the bottom of the core shell (1), and the graphite shell (2) is fixed to the support. Fuel balls (3) flow and fill from top to bottom inside the graphite shell (2). The fuel balls (3) are stacked to form a pebble bed core. The graphite shell (2) and the inner wall of the core shell (1) cooperate to form a flow cavity (10). The flow cavity (10) is connected to the bottom of the graphite shell (2). A coolant inlet (11) is opened in the upper region of the core shell (1) to connect to the flow cavity (10). A coolant outlet (21) is opened in the upper region of the graphite shell (2) to connect to the outside.

2. The high-temperature gas-cooled reactor core structure with high thermal power according to claim 1, characterized in that, The support includes a flow equalization plate (4) with evenly distributed flow distribution holes (41), the flow equalization plate (4) separates the flow cavity (10), and the plane of the flow equalization plate (4) is directly opposite the coolant inlet (11).

3. The high-temperature gas-cooled reactor core structure with high thermal power according to claim 2, characterized in that, The two side walls of the flow equalization plate (4) are respectively attached to and fixed to the inner walls of the opposite sides of the core shell (1), the bottom wall of the flow equalization plate (4) is attached to and fixed to the bottom wall of the core shell (1), and the top wall of the flow equalization plate (4) is attached to and fixed to the bottom wall of the graphite shell (2).

4. The high-temperature gas-cooled reactor core structure with high thermal power according to claim 3, characterized in that, The support includes two flow equalization plates (4) arranged opposite to each other. The two flow equalization plates (4) cooperate with the bottom wall of the core shell (1) and the bottom wall of the graphite shell (2) to form a flow equalization cavity (101).

5. The high-temperature gas-cooled reactor core structure with high thermal power according to claim 4, characterized in that, The bottom of the graphite shell (2) has several channels pre-set, and the channels are connected to the flow equalization cavity (101).

6. The high-temperature gas-cooled reactor core structure with high thermal power according to any one of claims 1-5, characterized in that, It also includes an inlet pipe (5) and an outlet pipe (6), wherein the inlet pipe (5) is installed on the core shell (1) and connected to the coolant inlet (11), and the outlet pipe (6) penetrates the core shell (1) and is connected to the coolant outlet (21).

7. The high-temperature gas-cooled reactor core structure with high thermal power according to claim 6, characterized in that, The outlet pipe (6) is coaxially sleeved inside the inlet pipe (5).

8. The high-temperature gas-cooled reactor core structure with high thermal power according to claim 6, characterized in that, An installation hole is provided in the upper region of the core shell (1), and the inlet pipe (5) is sealed and inserted into the installation hole.

9. The high-temperature gas-cooled reactor core structure with high thermal power according to any one of claims 1-5, characterized in that, It also includes a ball inlet tube (7) and a ball outlet tube (8). One end of the ball inlet tube (7) is connected to the top of the graphite shell (2), and the other end penetrates the top of the core shell (1). One end of the ball outlet tube (8) is connected to the bottom of the graphite shell (2), and the other end penetrates the bottom of the core shell (1).

10. The high-temperature gas-cooled reactor core structure with high thermal power according to claim 9, characterized in that, The ball inlet pipe (7) and the ball unloading pipe (8) are respectively centrally located at the upper and lower parts of the ball bed core.

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