Space nuclear reactor shield

Abstract

The embodiment of the present application provides a space nuclear reactor shield arranged on one side of a space nuclear reactor body and used for shielding a neutron and photon radiation field from the reactor body. The shield comprises: a beryllium shielding layer used for reflecting and shielding the neutron from the reactor body; a tungsten shielding layer connected to the outer side of the beryllium shielding layer, coaxially arranged with the beryllium shielding layer, and used for shielding the photon; a boron carbide shielding layer connected to the outer side of the beryllium shielding layer, coaxially arranged with the beryllium shielding layer, and used for absorbing the neutron and reducing secondary photons generated by the neutron in the shield; and a lithium hydride shielding layer connected to one end of the beryllium shielding layer and coaxially arranged with the beryllium shielding layer, and used for shielding the neutron from the reactor body. The shield in the embodiment of the present application can reasonably use the efficient neutron shielding material lithium hydride, and can avoid the irradiation swelling problem of lithium hydride.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of nuclear reactor technology, specifically to a space nuclear reactor shield. Background Technology

[0002] Space nuclear reactors typically consist of a reactor body, shielding, and radiators. The shielding is used to prevent structural materials and equipment from overheating, activating, and degrading due to radiation. Radiation shielding in space nuclear reactors primarily needs to consider neutron and gamma-ray shielding. Currently, commonly used shielding materials for space nuclear reactors include lithium hydride and tungsten. Lithium hydride offers good shielding against fast neutrons and is lightweight, while tungsten is a commonly used and highly efficient gamma-ray shielding material.

[0003] However, the biggest limiting factor for lithium hydride as a neutron shielding material is the irradiation swelling problem under the combined effects of temperature and photon dose fields. Irradiation swelling can lead to the fracture of the lithium hydride shield, shortening its lifespan and affecting its shielding effectiveness. Summary of the Invention

[0004] According to one embodiment of the present invention, a shielding body for a space nuclear reactor is provided. The space nuclear reactor includes a reactor body and a shielding body. The shielding body includes: a beryllium shielding layer for reflecting and shielding neutrons from the reactor body; a tungsten shielding layer connected to the outside of the beryllium shielding layer, coaxially arranged with the beryllium shielding layer, for shielding photons from the reactor body and secondary photons within the shielding body; a boron carbide shielding layer connected to the outside of the beryllium shielding layer, coaxially arranged with the beryllium shielding layer, for absorbing neutrons from the reactor body and reducing secondary photons generated by neutrons within the shielding body; and a lithium hydride shielding layer connected to one end of the beryllium shielding layer, coaxially arranged with the beryllium shielding layer, for shielding neutrons from the reactor body.

[0005] In embodiments of the present invention, the outer ring of the front end of the shield is made of beryllium with a lower density, while the inner ring of the front end of the shield is made of boron carbide and tungsten, thus avoiding the radiation swelling problem that occurs when lithium hydride is used at the front end of the shield. Simultaneously, the rear end of the shield uses lithium hydride, while the front end uses non-lithium hydride, allowing the lithium hydride at the rear end to avoid the radiation swelling region under the combined photon and temperature fields, and also contributing to the reduction of the overall mass of the shield. Attached Figure Description

[0006] Other objects and advantages of the invention will become apparent from the following description of embodiments of the invention with reference to the accompanying drawings, and will help to provide a comprehensive understanding of the invention.

[0007] Figure 1 This is a schematic diagram of the structure of a space nuclear reactor shield according to an embodiment of the present invention.

[0008] Figure 2 This is a schematic diagram of the structure of a space nuclear reactor according to an embodiment of the present invention.

[0009] It should be noted that the accompanying drawings are not necessarily drawn to scale, but are shown only in a schematic manner without affecting the reader's understanding.

[0010] Explanation of reference numerals in the attached figures:

[0011] 100. Shielding body; 10. Beryllium shielding layer; 20. Tungsten shielding layer; 21. First tungsten shielding layer; 22. Second tungsten shielding layer; 30. Lithium hydride shielding layer; 40. Boron carbide shielding layer;

[0012] 200. Reactor body; 210. Reactor core active zone; 220. Bottom reflector layer; 230. Top reflector layer; 240. Side reflector layer. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only one embodiment of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the described embodiments of this application without creative effort are within the scope of protection of this application.

[0014] It should be noted that, unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by a person with ordinary skill in the art to which this application pertains. Where the terms "first," "second," etc., are used throughout the text, they are used only to distinguish similar objects and should not be construed as indicating or implying their relative importance, order of precedence, or implicitly specifying the number of technical features indicated. It should be understood that the data described by "first," "second," etc., can be interchanged where appropriate. Where "and / or" appears throughout the text, it means including three parallel solutions. Taking "A and / or B" as an example, it includes solution A, or solution B, or a solution that satisfies both A and B. Furthermore, for ease of description, spatial relative terms such as "above," "below," "top," "bottom," etc., may be used here, only to describe the spatial positional relationship between one device or feature as shown in the figure and other devices or features. It should be understood that this also includes different orientations in use or operation besides those shown in the figure.

[0015] In space nuclear reactors, shielding is used to protect against radiation from the reactor to other equipment and structural materials. The choice of shielding material determines parameters such as shielding performance, shielding quality, and structural performance. However, lithium hydride, a commonly used neutron shielding material, is prone to radiation swelling under the combined influence of temperature and photon fields, leading to a deterioration in its shielding effectiveness. Therefore, embodiments of the present invention provide a shielding system to avoid the radiation swelling problem of lithium hydride. The shielding system in these embodiments is used in space nuclear reactors, wherein the space nuclear reactor comprises a reactor body and a shielding system.

[0016] Figure 1 A schematic diagram of the structure of a space nuclear reactor shielding according to an embodiment of the present invention is shown. Figure 1 As shown, the shielding body 100 includes a beryllium shielding layer 10, a tungsten shielding layer 20, a lithium hydride shielding layer 30, and a boron carbide shielding layer 40. The beryllium shielding layer 10 is used to reflect and shield neutrons from the reactor core. The beryllium shielding layer 10 is connected to the outside of the tungsten shielding layer 20, which is coaxially arranged with the beryllium shielding layer 10. The tungsten shielding layer 20 is used to shield photons from the reactor core and secondary photons generated within the shielding body 100. The beryllium shielding layer 10 is connected to the outside of the boron carbide shielding layer 40, which is coaxially arranged with the beryllium shielding layer 10. The boron carbide shielding layer 40 is used to absorb neutrons from the reactor core and can reduce secondary photons generated within the shielding body 100. The lithium hydride shielding layer 30 is connected to one end of the beryllium shielding layer 10 and is coaxially arranged with the beryllium shielding layer 10, used to shield neutrons from the reactor core.

[0017] When using the shield 100 in this embodiment of the invention, the shield 100 is disposed on one side of the space nuclear reactor body to shield neutron and photon radiation fields from the reactor body. The end containing the beryllium shielding layer 10 is positioned close to the reactor body, while the end containing the lithium hydride is positioned away from the reactor body.

[0018] In some embodiments, the beryllium shielding layer 10 is made of beryllium alloy. In this embodiment, beryllium is mainly used as the shielding layer material at the front end of the shield 100. Beryllium has a low density, which can reduce the weight of the shield 100. In addition, beryllium has a large neutron scattering cross section, which is suitable for slowing down and reflecting neutrons, thereby reducing the number of neutrons passing through the front end of the shield 100. Furthermore, beryllium has good physical properties and does not have the problem of radiation swelling.

[0019] In this embodiment, the rear end of the shield 100 is entirely made of lithium hydride as the shielding material. Since the front end of the shield 100 is provided with a beryllium shielding layer 10, a tungsten shielding layer 20, and a boron carbide shielding layer 40, it provides a certain degree of shielding against neutrons and photons. This significantly reduces the neutron and photon doses in the region where the lithium hydride shielding layer 30 is located, far from the reactor core. This ensures that the combination of temperature and photon dose fields in the lithium hydride region completely avoids the area that causes lithium hydride irradiation swelling. Furthermore, lithium hydride has extremely low density and the highest fast neutron shielding efficiency, allowing the shield 100 in this embodiment to shield against fast neutrons in this region with minimal mass loss.

[0020] It should be noted that, in the embodiments of the present invention, the front end of the shield 100 is the end closer to the stack body, and the rear end of the shield 100 is the end farther away from the stack body.

[0021] like Figure 1 As shown, in some embodiments, the tungsten shielding layer 20 includes a first tungsten shielding layer 21 and a second tungsten shielding layer 22. The first tungsten shielding layer 21 is located at the end of the shielding body 100 furthest from the lithium hydride shielding layer 30, and is used to shield photons from the reactor core. The second tungsten shielding layer 22 is connected between the beryllium shielding layer 10 and the lithium hydride shielding layer 30, and is used to shield photons from the reactor core and secondary photons from the front end of the shielding body 100.

[0022] In this embodiment, the first tungsten shielding layer 21 can shield high-intensity photons from the core fission reaction, such as transient photons and slow-release photons, thereby effectively reducing the photon shielding load at the rear end of the shield 100. The second tungsten shielding layer 22 can further shield photons and secondary photons from the reactor body, thereby meeting the photon dose requirements of the reactor load, while ensuring that the lithium hydride at the rear end of the shield 100 avoids the irradiation swelling region.

[0023] like Figure 1 As shown, in this embodiment, the boron carbide shielding layer 40 is connected between the first tungsten shielding layer 21 and the second tungsten shielding layer 22. It is used to absorb neutrons from the reactor core and can reduce secondary photons generated by neutrons within the shield 100. In this embodiment, the boron carbide shielding layer 40 is used to absorb neutrons from the reactor core, while simultaneously reducing secondary photons caused by neutron capture reactions, thereby further reducing the photon shielding load at the rear end of the shield 100.

[0024] Boron carbide has a slightly higher density than beryllium, enabling it to shield against neutrons and photons without significantly increasing the mass of the shield by 100. Furthermore, boron carbide can withstand high-temperature and high-radiation environments, and its application in space nuclear reactors presents virtually no radiation swelling issues.

[0025] In this embodiment, a boron carbide shielding layer 40 is provided between the first tungsten shielding layer 21 and the second tungsten shielding layer 22. By using boron carbide, which has a smaller mass than tungsten, to absorb neutrons and reduce secondary photons, the thickness and radius of the tungsten shielding layer 20 can be reduced, thereby reducing the use of heavy shielding material tungsten and further reducing the overall mass of the shielding body 100, which is beneficial for the application of the shielding body 100 in space nuclear reactors.

[0026] In some embodiments, the diameter of the shield 100 gradually increases along the axial direction from the beryllium shield 10 to the lithium hydride shield 30. The closer to the reactor core, the smaller the radiation range of the reactor core, and the smaller the required shielding range; while the farther away from the reactor core, the larger the required shielding range.

[0027] In this embodiment, the diameter of the front end of the shield 100 near the reactor body is set to be smaller than that of the rear end of the shield 100, which can effectively reduce the volume of the shield 100 and thus effectively reduce its mass. The shield 100 accounts for a large proportion of the total mass of the space nuclear reactor system, so optimizing the structure of the shield 100 and reducing its mass is of great significance.

[0028] Specifically, the radius of the end of the beryllium shielding layer 10 furthest from the lithium hydride shielding layer 30 is the same as the radius of the reactor body. This allows for neutron shielding of the front region of the shielding body 100 while minimizing the volume of the beryllium shielding layer 10, thus reducing the mass of the shielding body 100. Furthermore, the radius of the end of the beryllium shielding layer 10 furthest from the lithium hydride shielding layer 30 in this embodiment can be adjusted according to the radius of the reactor body, making it suitable for different space nuclear reactors.

[0029] Furthermore, the radius of the beryllium shielding layer 10 gradually increases along the axial direction from the first tungsten shielding layer 21 to the second tungsten shielding layer 22, thereby achieving shielding of the front end region of the shielding body 100 while ensuring that the beryllium shielding layer 10 has a small volume. In some embodiments, the beryllium shielding layer 10 is a hollow frustum shape, and the tungsten shielding layer 20 and the boron carbide shielding layer 40 are disposed in the hollow accommodating space of the beryllium shielding layer 10.

[0030] Similarly, the radius of the lithium hydride shielding layer 30 gradually increases along the axial direction from the front end to the rear end of the shielding body 100, thereby achieving shielding of the rear end region of the shielding body 100 while ensuring a small volume of the lithium hydride shielding layer 30. Specifically, the lithium hydride shielding layer 30 is also frustum-shaped. Furthermore, at the contact point between the lithium hydride shielding layer 30 and the beryllium shielding layer 10, the radius of the beryllium shielding layer 10 is the same as the radius of the lithium hydride shielding layer 30.

[0031] Furthermore, the height of the beryllium shielding layer 10 can be adjusted so that the temperature and photon dose in the area where the lithium hydride shielding layer 30 is located can avoid the irradiation swelling range of lithium hydride. It should be noted that the irradiation swelling range mentioned in this embodiment refers to both the temperature range and the photon dose range. For example, when the temperature of lithium hydride is below 600K, a cumulative photon irradiation dose greater than 0.5 Grads will cause severe irradiation swelling; when the temperature of lithium hydride is above 600K, it will hardly cause any swelling.

[0032] Specifically, the height of the beryllium shielding layer 10 is the minimum height that allows lithium hydride to avoid the irradiation swelling region. This allows for the minimization of the volume of the beryllium shielding layer 10 while preventing lithium hydride irradiation swelling, thereby reducing the mass of the shield 100. For example, when lithium hydride is below 600K, the height of the beryllium shielding layer 10 can be the minimum height that reduces the photon dose in the region where the lithium hydride shielding layer 30 is located to below 0.5 Grads.

[0033] In this embodiment, the height of the lithium hydride shielding layer 30 can be determined according to the neutron flux requirements to meet the shielding requirements of other equipment and materials in the space nuclear reactor system, and to prevent structural materials and instruments from being irradiated and causing performance degradation.

[0034] Furthermore, the radii of the first tungsten shielding layer 21, the second tungsten shielding layer 22, and the boron carbide shielding layer 40 are consistent along their axial direction and correspond to the core active region of the space nuclear reactor. In this embodiment, the radii of the first tungsten shielding layer 21, the second tungsten shielding layer 22, and the boron carbide shielding layer 40 can be determined according to the photon dose to suit different space nuclear reactors. Specifically, the first tungsten shielding layer 21, the second tungsten shielding layer 22, and the boron carbide shielding layer 40 are all cylindrical.

[0035] like Figure 1 As shown, in some embodiments, the radius of the first tungsten shielding layer 21 is smaller than the radius of the second tungsten shielding layer 22. Since the first tungsten shielding layer 21 is relatively close to the reactor body, the radius of the first tungsten shielding layer 21 can be significantly reduced, thereby blocking some photons from the reactor body with a smaller mass cost and significantly reducing the mass of the heavy shielding material.

[0036] Furthermore, the thickness of the first tungsten shielding layer 21 is less than the thickness of the second tungsten shielding layer 22. In this embodiment, a double-layer heavy shielding tungsten layer with a thinner front and thicker back is used to achieve the best shielding effect.

[0037] In this embodiment, the front end of the shield 100 adopts a combination design of low-density beryllium, boron carbide and double-layer tungsten materials. Compared with the traditional lithium hydride and tungsten plate design, it effectively avoids the complex irradiation swelling problem of lithium hydride at the front end of the shield 100 under the combination of strong photon field and temperature field.

[0038] Furthermore, compared to shielding designs that only use lithium hydride and tungsten plates, the shielding body 100 in this embodiment of the invention can significantly reduce the radius of the tungsten shielding layer, greatly reduce the mass of the heavy shielding material, and the shielding body 100 as a whole has a total shielding mass that is comparable to or even less than that of the lithium hydride and tungsten plate design.

[0039] In addition, the rear end of the shield 100 adopts a lithium hydride light shielding design, which avoids the radiation swelling range under the combination of photon field and temperature field. The overall weight of the shield 100 is comparable to or even less than that of the design scheme with only lithium hydride and tungsten plate, and has both feasibility and quality advantages.

[0040] It should be noted that the heavy shielding material mentioned in this invention refers to a material containing atoms with a large atomic number; the light shielding material refers to a material containing atoms with a small atomic number, which can rapidly slow down neutrons.

[0041] In some embodiments, the shielding body 100 further includes a housing, in which the beryllium shielding layer 10, tungsten shielding layer 20, lithium hydride shielding layer 30, and boron carbide shielding layer 40 are all located, and the housing covers the outer surfaces of the beryllium shielding layer 10, tungsten shielding layer 20, and lithium hydride shielding layer 30. In this embodiment, the housing is provided on the outer surface of the shielding body 100, which ensures both the structural integrity of the shielding body 100 and meets the overall structural strength requirements.

[0042] Furthermore, the outer surfaces of the beryllium shielding layer 10, the lithium hydride shielding layer 30, and the boron carbide shielding layer 40 are respectively provided with shells. In this embodiment, the outer surfaces of each shielding layer are covered with shells, which facilitates the fixed connection between the shielding layers and further ensures the integrity of the structure. Specifically, after the outer surfaces of each shielding layer are covered with shells, the shielding layers can be connected using connectors (e.g., rivets) to assemble the shielding body 100.

[0043] In some embodiments, the shell is made of titanium alloy. Specifically, titanium alloy plates are connected to the outer surfaces of the front and rear ends of the shield 100, while titanium alloy cladding is provided on the sides of the shield 100. Titanium alloy has high mechanical strength and its density is only about half that of stainless steel. Compared to stainless steel used in traditional space nuclear reactors, titanium alloy is lighter while still meeting structural strength requirements, thus reducing the weight of the shield 100 and the reactor structure.

[0044] Embodiments of the present invention also provide a space nuclear reactor. Figure 2 A schematic diagram of a space nuclear reactor according to an embodiment of the present invention is shown.

[0045] like Figure 2As shown, the space nuclear reactor in this embodiment includes a reactor body 200 and a shield 100. The shield 100 is the same as in any of the above embodiments. The shield 100 is disposed on one side of the reactor body 200 along the axial direction, and there is a gap between the reactor body 200 and the shield 100. In the shield 100, the beryllium shielding layer 10 is close to the reactor body 200, while the lithium hydride shielding layer 30 is far from the reactor body 200.

[0046] The reactor core 200 includes a core active region 210, a bottom reflector 220, a top reflector 230, and side reflectors 240. The bottom reflector 220 is located on top of the core active region 210, the top reflector 230 is located on top of the core active region 210, and the side reflectors 240 surround the sides of the core active region 210. Each reflector can reduce neutron leakage in the core or regulate the reactor's reactivity, maintaining the reactor's normal operation.

[0047] In this embodiment, the shield 100 is disposed at the rear end of the reactor body 200 and spaced a certain distance from the reactor body 200 to prevent the radiation dose received by the instruments, equipment, or structural materials at the rear end of the reactor body 200 from exceeding the threshold, thus ensuring that the radiation dose of the loads in the system meets the requirements. The rear end of the reactor body 200 refers to the end where the instruments, equipment, and structural materials are arranged. Figure 2 In the space nuclear reactor shown, the shield 100 is located on top of the reactor body 200.

[0048] In this embodiment, the radius of the beryllium shielding layer 10 near the core active region 210 is the same as the radius of the side reflector layer 240 in the reactor body 200, thereby covering the irradiation area of ​​the reactor body 200 and effectively shielding neutrons from the reactor body 200.

[0049] In this embodiment, the space nuclear reactor uses a shield 100, which can make reasonable use of the most efficient neutron shielding material, lithium hydride, and can avoid the radiation swelling problem of lithium hydride, while also taking into account the requirements of reasonable structure and light weight.

[0050] Regarding the embodiments of the present invention, it should also be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other to obtain new embodiments.

[0051] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A space nuclear reactor shielding body, characterized in that, The space nuclear reactor includes a reactor body and the shielding body; the shielding body includes: A beryllium shielding layer, which is used to reflect and shield neutrons from the reactor body; A tungsten shielding layer, wherein a beryllium shielding layer is connected to the outside of the tungsten shielding layer, the tungsten shielding layer and the beryllium shielding layer are coaxially arranged, and the tungsten shielding layer is used to shield photons from the reactor body and secondary photons from the shielding body; A boron carbide shielding layer, wherein the beryllium shielding layer is connected to the outside of the boron carbide shielding layer, the boron carbide shielding layer and the beryllium shielding layer are coaxially arranged, and the boron carbide shielding layer is used to absorb neutrons from the reactor body and reduce the secondary photons generated by the neutrons in the shielding body; A lithium hydride shielding layer is connected to one end of the beryllium shielding layer, and the lithium hydride shielding layer and the beryllium shielding layer are coaxially arranged to shield neutrons from the reactor body; Wherein, the end where the beryllium shielding layer is located is close to the stack body, and the end where the lithium hydride shielding layer is located is far away from the stack body; The tungsten shielding layer includes: The first tungsten shielding layer is located at the end of the shielding body away from the lithium hydride shielding layer, and is used to shield photons from the stack body. A second tungsten shielding layer is connected between the beryllium shielding layer and the lithium hydride shielding layer to shield photons and secondary photons from the stack body; The boron carbide shielding layer is connected between the first tungsten shielding layer and the second tungsten shielding layer.

2. The shielding body according to claim 1, characterized in that, The diameter of the shielding body gradually increases along the axial direction from the beryllium shielding layer to the lithium hydride shielding layer.

3. The shielding body according to claim 1, characterized in that, The radius of the first tungsten shielding layer is smaller than the radius of the second tungsten shielding layer.

4. The shielding body according to claim 3, characterized in that, The thickness of the first tungsten shielding layer is less than the thickness of the second tungsten shielding layer.

5. The shielding body according to claim 1, characterized in that, The radius of the end of the beryllium shielding layer away from the lithium hydride shielding layer is the same as the radius of the stack body.

6. The shielding body according to claim 1, characterized in that, The radius of the beryllium shielding layer gradually increases along the axial direction from the first tungsten shielding layer to the second tungsten shielding layer.

7. The shielding body according to claim 1, characterized in that, The outer surface of the shield is provided with a shell, and the beryllium shielding layer, tungsten shielding layer, boron carbide shielding layer and lithium hydride shielding layer are all located inside the shell.

8. The shielding body according to claim 1, characterized in that, The outer surfaces of the beryllium shielding layer, the lithium hydride shielding layer, and the boron carbide shielding layer are each provided with a shell.

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