Core fuel element and heat pipe cooled reactor having radial extraction heat pipes

Abstract

A core fuel element (10) and a heat pipe cooled reactor having radial extraction heat pipes (2). The core fuel element (10) is used for forming a core fuel (1), and the core fuel (1) is used for forming a heat pipe cooled reactor; the core fuel element (10) is divided into a core fuel element segments (11) along the axis; an axial heat pipe channel is formed in each core fuel element segment (11); and a radial heat pipe extraction channel is further formed in the radial direction in each core fuel element segment (11) other than the core fuel element segments (11) located at the head and the tail. The heat pipes (2) are accommodated in both the axial heat pipe channel and the radial heat pipe extraction channel. Straight heat pipes (21) and bent heat pipes (22) are arranged in cooperation with the axial heat pipe channels and the radial heat pipe extraction channels, so that a plurality of heat pipes (2) are arranged in each axial heat pipe channel in the core fuel element (10), and thus the heat exchange effect of a single core fuel element (10) is improved, thereby improving the overall heat exchange efficiency of the heat pipe cooled reactor.

Description

Core fuel element and heat pipe cooled reactor with radially leading heat pipes Technical Field

[0001] The present invention relates to the field of heat exchange design, in particular to a reactor core fuel element and a heat pipe cooling reactor with radially leading heat pipes. Background Art

[0002] With the widespread application of nuclear energy technology, the demand for heat pipe-cooled reactors is growing towards higher power. However, current heat pipe reactors all use a scheme where straight heat pipes are inserted and extended along the axial direction of the reactor core. Whether inserted from one side (as shown in Figure 1), staggered from both sides (as shown in Figure 2), or inserted in opposite directions (as shown in Figure 3), each axial heat pipe channel in the core can only accommodate one or two heat pipes. Due to the limited heat exchange capacity of a single heat pipe, it is difficult to provide sufficient cooling effect. This greatly limits the power of heat pipe-cooled reactors and hinders the smooth development of high-power heat pipe reactors. Summary of the Invention

[0003] In view of the defects in the prior art, an object of the present invention is to provide a heat pipe cooled reactor with radially extending heat pipes.

[0004] According to the present invention, a core fuel element is provided, which is used to form a core fuel, and the core fuel is used to form a heat pipe cooled reactor;

[0005] The core fuel element is divided into a core fuel element segments along the axis; a is greater than 2;

[0006] Each core fuel element segment is provided with one or more axial heat pipe channels; the axial heat pipe channels in adjacent core fuel element segments correspond to each other, and the corresponding axial heat pipe channels are interconnected;

[0007] Except for the core fuel element segments located at the head and tail ends, each core fuel element segment is further provided with a radial heat pipe lead-out channel in the radial direction. The number of core fuel element segments provided with the radial heat pipe lead-out channels is a-2. The axial heat pipe channels in the core fuel element segment correspond to the radial heat pipe lead-out channels in the core fuel element segment on a one-to-one basis, and the corresponding axial heat pipe channels are connected to the radial heat pipe lead-out channels.

[0008] The axial heat pipe channel and the radial heat pipe outlet channel both contain the heat pipe;

[0009] Each heat pipe has one end located in the axial heat pipe channel and the other end located outside the core fuel element.

[0010] Preferably, each core fuel element segment is provided with an axial heat pipe channel; the axial heat pipe channels in adjacent core fuel element segments are sequentially connected to form an axial heat pipe channel in the core fuel element;

[0011] A heat pipe is provided in each core fuel element segment.

[0012] Preferably, the heat pipe includes a straight heat pipe and a bent heat pipe;

[0013] A straight heat pipe is provided in the axial heat pipe channel in the core fuel element segments at both ends; one end of the straight heat pipe is installed in the axial heat pipe channel in the core fuel element segment, and the other end extends out of the axial heat pipe channel;

[0014] Bent heat pipes are arranged in the axial heat pipe channels in the core fuel element channels of the remaining core segments; one end of the bent heat pipe is located in the axial heat pipe channel, and the other end extends toward the radial heat pipe lead-out channel and to the outside of the radial heat pipe lead-out channel.

[0015] Preferably, the number of the core fuel element segments is 5, namely, a first core fuel element segment, a second core fuel element segment, a third core fuel element segment, a fourth core fuel element segment, and a fifth core fuel element segment; the 5 core fuel element segments are arranged in sequence;

[0016] A straight heating pipe is arranged in each of the first core fuel element segment and the fifth core fuel element segment;

[0017] A bent heat pipe is arranged in each of the second core fuel element segment, the third core fuel element segment and the fourth core fuel element segment.

[0018] Preferably, the number of heat pipes in a core fuel element is N. At a given heat pipe operating temperature, when the average heat pipe heat transfer efficiency in the channel is equal to the boiling limit heat transfer efficiency, N is optimal. At this time, the heat transfer efficiency of the heat pipe channel of the core fuel element is the highest.

[0019] According to the present invention, a heat pipe cooled reactor with radially led-out heat pipes includes a core fuel, which is composed of a plurality of core fuel elements arranged in parallel; the core fuel element is the core fuel element described above.

[0020] Preferably, the heat pipe cooled reactor does not have the following axial position section: the bent heat pipes in the section are all radially led out at the section.

[0021] Preferably, the bent heat pipes derived from the same axial position are derived in a layered stacking mode.

[0022] Preferably, the layered stacking mode is: from a side view angle, the outlets of multiple radial heat pipe outlet channels at the same axial position are arranged in layers, each layer is arranged with several radial heat pipe outlet channels, and the layers are stacked.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention utilizes core fuel elements to form core fuel, and then utilizes the core fuel to form a heat pipe cooling reactor, wherein radial heat pipe lead-out channels are provided in the core fuel elements; the present invention arranges straight heat pipes and bent heat pipes in combination with axial heat pipe channels and radial heat pipe lead-out channels, so that multiple heat pipes can be arranged in each axial heat pipe channel in the core fuel elements, thereby improving the heat exchange effect of a single core fuel element, thereby improving the overall heat exchange efficiency of the heat pipe cooling reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0026] FIG1 is a schematic structural diagram of a unilateral insertion solution in the prior art;

[0027] FIG2 is a schematic structural diagram of a two-side staggered insertion scheme in the prior art;

[0028] FIG3 is a schematic structural diagram of a two-side insertion scheme in the prior art;

[0029] FIG4 is a structural view of a reactor core fuel element according to the present invention;

[0030] FIG5 is a schematic diagram of the cross-sectional structure of the core fuel at an axial position according to the present invention;

[0031] FIG6 is a schematic structural diagram of a heat pipe-cooled reactor according to the present invention, which mainly illustrates the arrangement of the heat pipes;

[0032] FIG7 is a schematic structural diagram of a heat pipe cooled reactor according to the present invention in a layered stacking mode;

[0033] Figure 8 is a schematic diagram of the heat pipe structure;

[0034] Figure 9 is a schematic diagram of the relationship between the heat transfer limit of the heat pipe and the heat pipe operating temperature

[0035] Figure 10 is a schematic diagram showing the relationship between the heat transfer efficiency of the heat pipe channel and the number of inserted heat pipes.

[0036] The figure shows:

[0037] DETAILED DESCRIPTION

[0038] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0039] The present invention provides a core fuel element, wherein the core fuel element 10 is used to form a core fuel 1, and the core fuel 1 is used to form a heat pipe cooled reactor;

[0040] The core fuel element 10 is divided into a core fuel element segments 11 along the axis; a is greater than 2;

[0041] Each core fuel element segment 11 is provided with one or more axial heat pipe channels. Preferably, as shown in FIG4 , each core fuel element segment 11 is provided with only one axial heat pipe channel. Each core fuel element segment 11 is provided with one heat pipe 2, i.e., the number a of core fuel element segments 11 is the same as the number of heat pipes 2 in the core fuel element 10. The axial heat pipe channels in adjacent core fuel element segments 11 correspond one to one, and the corresponding axial heat pipe channels are interconnected; that is, the axial heat pipe channels in adjacent core fuel element segments 11 are interconnected in sequence to form a single axial heat pipe channel in the core fuel element 10.

[0042] In addition to the core fuel element segments 11 at both ends, each core fuel element segment 11 also has radial heat pipe lead-out channels radially defined. That is, the core fuel element segment 11 located between the core fuel element segments 11 at both ends has radial heat pipe lead-out channels radially defined. The number of core fuel element segments 11 with radial heat pipe lead-out channels is a-2. The axial heat pipe channels in a core fuel element segment 11 correspond one-to-one to the radial heat pipe lead-out channels in that core fuel element segment 11, and the corresponding axial heat pipe channels are connected to the radial heat pipe lead-out channels.

[0043] The heat pipes 2 are both housed in the axial heat pipe channel and the radial heat pipe outlet channel; one end of each heat pipe 2 is located in the axial heat pipe channel and the other end is located outside the core fuel element 10 .

[0044] The heat pipes 2 include straight heat pipes 21 and bent heat pipes 22. The axial heat pipe channels in the core fuel element segments 11 at both ends are provided with only straight heat pipes 21. One end of the straight heat pipe 21 is installed in the axial heat pipe channel in the core fuel element segment 11, and the other end extends out of the axial heat pipe channel. The axial heat pipe channels in the remaining core segments 11 are provided with only bent heat pipes 22. One end of the bent heat pipe 22 is located in the axial heat pipe channel, and the other end extends toward the radial heat pipe lead-out channel and beyond the radial heat pipe lead-out channel, thereby extending out of the core fuel element 10.

[0045] In a preferred embodiment, referring to FIG4 and FIG6 , the number of the core fuel element segments 11 is five, namely a first core fuel element segment 111, a second core fuel element segment 112, a third core fuel element segment 113, a fourth core fuel element segment 114, and a fifth core fuel element segment 115; the five core fuel element segments 11 are arranged in sequence;

[0046] A straight heat pipe 21 is arranged in each of the first core fuel element block 111 and the fifth core fuel element block 115; a bent heat pipe 22 is arranged in each of the second core fuel element block 112, the third core fuel element block 113 and the fourth core fuel element block 114.

[0047] That is, for the core fuel element 10, two straight heat pipes 21 are arranged on both sides of a single axial heat pipe channel of the core fuel element 10, and three bent heat pipes 22 are arranged inside the axial heat pipe channel. A portion of the bent heat pipe 22 is arranged axially in the axial heat pipe channel, and the other portion is bent and led out of the core fuel element 10 along the radial heat pipe lead-out channel of the core fuel element 10. One straight heat pipe 21, three bent heat pipes 22, and one straight heat pipe 21 are arranged in sequence, and the evaporation sections of the above five heat pipes fill the axial heat pipe channel of the core fuel element 10 in sequence. The heat of the core fuel element 10 is led out from the evaporation section of the heat pipe to the condensation section of the heat pipe. The heat in the straight heat pipe 21 is led out axially, and the bent heat pipe 22 turns to be led out radially at the core fuel element segment. In this way, for the core fuel element 10, more than two heat pipes can be continuously arranged in the axial heat pipe channel of a complete core fuel element 10, and the number of heat pipes can be increased or decreased according to the core power, effectively increasing the total number of heat pipes in the stack and ensuring the effective implementation of a high-power heat pipe stack.

[0048] The number of heat pipes 2 in a core fuel element 10 is N. At a given heat pipe operating temperature, in a heat pipe channel, the total heat transfer amount increases as the number of heat pipes increases, while the boiling heat transfer limit of the heat pipe decreases as the number of heat pipes increases. When the average heat pipe heat transfer efficiency in the channel is equal to the boiling limit heat transfer efficiency, N is optimal, and the heat transfer efficiency of the heat pipe channel of the core fuel element is the highest. Specifically, as shown in FIG9 , in an axial heat pipe channel of a core fuel element 10 of a given power and length, when a heat pipe is inserted, generally speaking, the heat transfer power of the heat pipe is limited by the corresponding heat transfer limit at its operating temperature, as shown by the solid line in FIG9 , such as the entrainment limit, the capillary limit, etc. Under the premise that the material temperature and operating conditions permit, the heat pipe operating temperature can be increased to increase the heat transfer limit, thereby ultimately increasing the heat pipe heat transfer efficiency.

[0049] At a given heat pipe operating temperature, the heat transfer power of a single heat pipe is limited by the corresponding heat transfer limit. It should be noted that, with the exception of the boiling limit, which is directly proportional to the length of the heat pipe's evaporator section, all other limits are either independent of or inversely proportional to the length of the heat pipe's evaporator section. Since, under most heat pipe operating conditions, the heat pipe temperature does not reach the region dominated by the boiling limit, two or more heat pipes can be placed within a single axial heat pipe channel of the core fuel element 10. While the evaporator sections of these heat pipes are shortened relative to those of a single heat pipe, their corresponding heat transfer limits can be slightly increased. This means that the average heat transfer efficiency of multiple heat pipes can be greater than that of a single heat pipe, thereby improving the channel's overall heat transfer efficiency.

[0050] However, it should be noted that the number n of multiple heat pipes will be limited by the boiling limit. As mentioned above, since the boiling limit is proportional to the length of the evaporation section, when the evaporation section is repeatedly reduced, as shown by the dotted line in Figure 9, the boiling limit will quickly drop to a value lower than other limit values ​​at the same operating temperature. That is, at this time, the heat transfer limit is dominated by the boiling limit, so that the average single heat transfer of multiple heat pipes in the same channel reaches the limit. At this time, if more heat pipes are added, since the heat flux per unit length has reached the extreme value (boiling limit / channel length), the increased number of heat pipes obtained by reducing the length of the evaporation section of a single heat pipe will not increase the total channel heat transfer. That is, at this time, as shown in Figure 10, the optimal value of N is reached.

[0051] The present invention also provides a heat pipe cooled reactor with radially led-out heat pipes, the heat pipe cooled reactor including a core fuel 1, which is composed of a plurality of core fuel elements 10 arranged in parallel; in different core fuel elements 10, the number a of core fuel element segments 11 is not exactly the same, and the core fuel elements 10 are the core fuel elements described above.

[0052] The heat pipes 2 in Figure 6 can carry heat from the core fuel 1 out of the core fuel 1 and transfer it to the energy conversion device. Because the number of heat pipes 2 used for system cooling has increased by more than 2.5 times (in Figure 3, the number of heat pipes 2 in the axial heat pipe channel of a single core fuel element is two; as shown in Figures 4 and 6, the number of heat pipes 2 in the axial heat pipe channel of a single core fuel element in the present invention is five), the heat transfer from a single core fuel element 10 will increase by 2.5 times. Stronger core output power corresponds to a stronger core neutron flux, thus providing a stronger core proliferation capability. The increased number of heat pipes in the core effectively ensures the safe operation of the core.

[0053] In a preferred embodiment, when implementing a radial heat pipe extraction scheme in a nuclear reactor using heat pipe cooling, for the core fuel 1, in order to ensure that neutrons can move smoothly throughout the core, if all the bent heat pipes 22 in the core fuel 1 are radially extracted at the same axial position, it will become difficult to arrange the nuclear fuel at that location, which may cause the nuclear reaction to stop. In order to solve the above problem, it can be considered to extract the heat pipes in all heat pipe channels in the core fuel 1 at different axial positions, so as to ensure that when extracting at any axial position, there will always be some heat pipe channels at the same axial position that do not radially extract the heat pipes, so that the corresponding nuclear fuel can still ensure neutron circulation and nuclear reaction; that is, in the heat pipe cooled reactor, there is no axial position section where the bent heat pipes 22 in this section are all radially extracted at this section.

[0054] In a preferred embodiment, the bent heat pipes 22 derived from the same axial position are derived in a layered stacking mode. The layered stacking mode is that, from the side view angle shown in FIG7 , the outlets of multiple radial heat pipe lead-out channels at the same axial position are arranged in layers, with each layer being provided with several radial heat pipe lead-out channel outlets, and the layers are stacked. As shown in FIG5 , this schematic diagram only shows the heat pipes in the axial heat pipe channels corresponding to the outermost and second outermost fuel elements in 1 / 6 of the core fuel 1, and illustrates the layered stacking diagram for radial extraction. The remaining inner layers are also sequentially layered and stacked.

[0055] Since it is difficult to fill the nuclear fuel at the corresponding position when the heat pipe is radially exported, the overall nuclear fuel in the core may decrease, affecting the nuclear criticality and burnup time of the core. Therefore, in a preferred example, the enrichment of the fissile material of the nearby nuclear fuel in the radial export area needs to be increased accordingly to ensure the criticality and effective burnup time of the entire stack.

[0056] As shown in Figure 8, heat pipes transfer heat through natural circulation within the tubes. By placing the evaporator section within the core fuel and the adiabatic and condenser sections outside the core fuel, the working fluid in the heat pipe, such as alkali metals such as lithium, sodium, and potassium, evaporates in the evaporator section to form steam. Driven by expansion and natural convection, the steam moves toward the low-temperature, high-density condenser section. A low-temperature heat absorber is located outside the condenser section of the heat pipe. After releasing heat in the condenser section, the high-temperature steam condenses into a liquid phase and returns to the steam section through natural convection and capillary wicking. In this way, the heat pipe can effectively transfer heat from the reactor core without external power. Therefore, the heat pipes within the reactor operate independently during the heat transfer process, without interfering with each other.

[0057] Multiple heat pipes are inserted into each axial heat pipe channel within the core fuel element 10. During reactor operation, fission reactions in the core fuel release heat that heats the evaporator section of the heat pipe, raising the temperature of the evaporator section. Natural circulation then transfers this heat to the insulation and condenser sections of the external heat pipe. The condenser section of the external heat pipe can be connected to an energy conversion device, which converts the heat in the heat pipe into electrical energy or thermal energy for transmission to end users.

[0058] In summary, the core operating power of the present invention is higher: since the core fuel element 10 adopts a radially led heat pipe cooling method, the heat exchange capacity of the core is enhanced. Therefore, under the same core fuel structure, this method increases the core power by >n / 2 times, where n is the number of heat pipes arranged in a single axial heat pipe channel for the core fuel element 10. The core of the present invention has a stronger proliferation capacity: the power in the core is high, the neutron flux is strong, the probability of fissile nuclides absorbing neutrons to undergo capture reactions is higher, and the rate of fissile nuclides produced is faster. The present invention is safer: under the same core structure, the number of heat pipes that transfer heat to the core fuel is increased. In the event of a heat pipe failure accident, the accident redundancy is greater, there are more heat pipes to transfer heat in the core, and the core fuel 1 is safer. The present invention has a wide range of applications: under the same core structure, a higher power power supply can meet the needs of multiple schemes.

[0059] This invention breaks away from the existing design of straight heat pipes 21 in the core cooling system. Instead, it employs curved heat pipes 22 extending radially from the core fuel element 10. This significantly improves the overall heat transfer efficiency within a single axial heat pipe channel within the core fuel element 10, given the heat transfer efficiency of a single heat pipe. During normal core operation, all heat pipes contribute to cooling. Compared to conventional heat pipe stack designs, this design maintains the same number of coolant channels. The cooling system's heat pipe count and heat transfer capacity are >n / 2 times greater than those of existing heat pipe stack designs, where n is the number of heat pipes arranged within a single axial heat pipe channel for the core fuel element 10.

[0060] The present invention leads some of the heat pipes 2 outside the fuel core 1, thereby making it possible to arrange more than two heat pipes through the axial heat pipe channels of the core fuel elements 10, which originally could be penetrated by one or two heat pipes, by radially leading the heat pipes from between the segments. Thus, multiple (>2) heat pipes can be arranged according to power requirements, effectively improving the overall heat exchange capacity of the heat pipes, thereby increasing the effective power of the heat pipe-cooled reactor.

[0061] In the description of this application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and 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, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0062] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A core fuel element, characterized in that, The core fuel element (10) is used to form the core fuel (1), and the core fuel (1) is used to form a heat pipe cooled reactor; The core fuel element (10) is divided into a core fuel element segments (11) along the axis; a is greater than 2; One or more axial heat pipe channels are provided in each core fuel element segment (11); the axial heat pipe channels in adjacent core fuel element segments (11) correspond to each other one by one, and the corresponding axial heat pipe channels are connected; Except for the core fuel element segments (11) at both ends, each core fuel element segment (11) is also provided with a radial heat pipe extraction channel in the radial direction, and the number of core fuel element segments (11) provided with the radial heat pipe extraction channel is a - 2; the axial heat pipe channels in the core fuel element segment (11) correspond to the radial heat pipe extraction channels in the core fuel element segment (11) one by one, and the corresponding axial heat pipe channels are connected to the radial heat pipe extraction channels; Both the axial heat pipe channels and the radial heat pipe extraction channels accommodate the heat pipes (2); One end of each heat pipe (2) is located in the axial heat pipe channel, and the other end is located outside the core fuel element (10).

2. The core fuel element according to claim 1, characterized in that, One axial heat pipe channel is provided in each core fuel element segment (11); the axial heat pipe channels in adjacent core fuel element segments (11) are connected in sequence to form an axial heat pipe channel in the core fuel element (10); One heat pipe (2) is provided in each core fuel element segment (11).

3. The core fuel element according to claim 2, characterized in that, The heat pipe (2) includes a straight heat pipe (21) and a bent heat pipe (22); Straight heat pipes (21) are provided in the axial heat pipe channels in the core fuel element segments (11) at both ends; one end of the straight heat pipe (21) is installed in the axial heat pipe channel in the core fuel element segment (11), and the other end extends out of the axial heat pipe channel; Bent heat pipes (22) are provided in the axial heat pipe channels in the remaining core fuel element segments (11); one end of the bent heat pipe (22) is located in the axial heat pipe channel, and the other end extends towards the radial heat pipe extraction channel and extends outside the radial heat pipe extraction channel.

4. The core fuel element according to claim 1, characterized in that, The number of the core fuel element segments (11) is 5, which are the first core fuel element segment (111), the second core fuel element segment (112), the third core fuel element segment (113), the fourth core fuel element segment (114), and the fifth core fuel element segment (115); the 5 core fuel element segments (11) are arranged in sequence; One straight heat pipe (21) is arranged in each of the first core fuel element segment (111) and the fifth core fuel element segment (115); One bent heat pipe (22) is arranged in each of the second core fuel element segment (112), the third core fuel element segment (113), and the fourth core fuel element segment (114).

5. The core fuel element according to claim 1, characterized in that, The number of heat pipes (2) in a core fuel element (10) is N. At a given operating temperature of the heat pipe, N is optimal when the average heat transfer efficiency of the heat pipe in the channel is equal to the boiling limit heat transfer efficiency, and at this time, the heat transfer efficiency of the heat pipe channel of the core fuel element is the highest.

6. A heat pipe cooled reactor with radially led-out heat pipes, characterized in that, It includes core fuel (1), and the core fuel (1) is composed of a plurality of core fuel elements (10) arranged in parallel; the core fuel element (10) is the core fuel element according to any one of claims 1-5.

7. The heat pipe cooled reactor with radially led-out heat pipes according to claim 6, wherein There is no such axial position cross-section in the heat pipe cooled reactor: in this cross-section, all the bent heat pipes (22) are led out radially at this cross-section.

8. The heat pipe cooled reactor with radially extended heat pipes according to claim 6, characterized in that, The bent heat pipes (22) led out at the same axial position are led out in a layered superposition mode.

9. The heat pipe cooled reactor with radially led-out heat pipes according to claim 6, characterized in that, The layered superposition mode is: from the perspective of a side view, the outlets of a plurality of radial heat pipe lead-out channels at the same axial position are arranged in layers, and each layer is provided with the outlets of several radial heat pipe lead-out channels, and they are stacked between layers.

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