Irradiation target for the production of isotopes and isotope production reactor

Abstract

The application discloses an irradiation target for producing isotopes and an isotope production reactor, the irradiation target comprising an outer cladding, the outer cladding being a cylinder structure, the cylinder structure comprising a plurality of wing paths converging at a point; the plurality of wing paths are arranged at equal intervals with the converging point as the center, and a plurality of target layers are arranged at equal intervals in the plurality of wing paths along the axial direction of the outer cladding; the target layer comprises a plurality of irradiation beads arranged at equal intervals in each wing path along the cross-sectional direction of the outer cladding. Based on the irradiation target, the application further provides a reactor, the reactor adding the irradiation target between fuel assemblies, the irradiation target containing a plurality of irradiation beads, compared with the prior art, the application increases the storage capacity of uranium fuel in the irradiation target through the irradiation beads, more effectively utilizes thermal neutrons, improves the isotope production capacity, and solves the problem of low isotope production capacity in general research reactors or experimental reactors.

Description

Technical Field

[0001] This application relates to the field of medical isotope production reactor technology, and more particularly to an irradiation target for isotope production and an isotope production reactor equipped with the irradiation target. Background Technology

[0002] In recent years, nuclear medicine has rapidly become more widespread, with the number of visits increasing significantly year by year. This has led to an increasingly tight supply of medical isotopes, the core material basis of nuclear medicine. The production of medical isotopes mainly comes from reactors and accelerators. Reactor-based isotope production primarily involves irradiating a target with neutrons within the reactor's irradiation channels. Compared to accelerator-based isotope production, reactor-based production offers advantages such as higher yield and higher specific activity.

[0003] There are two main methods for producing isotopes using reactor-irradiated targets. One method involves neutron-induced fission of fissile nuclides (nuclear fuel), obtaining the target isotope from the fission fragments. The other method involves neutron capture of a lead nuclide, activating the lead nuclide to obtain the target isotope. Both methods utilize the extremely high neutron flux within the reactor. Relatively speaking, the fission method yields higher isotope production and specific activity, making it more valuable for medical applications.

[0004] While conventional nuclear fuels can also produce target isotopes through fission, the half-lives of these isotopes are generally short (typically a few hours to tens of hours), resulting in a short irradiation cycle for the target. Within such a short irradiation cycle, the fuel reaches a shallow burnup depth, leading to fuel waste if conventional nuclear fuel is used. Furthermore, the high fast neutron flux in the central region of nuclear fuel is unfavorable for fission production of isotopes. The large amount of fission heat generated by conventional fuels also poses a challenge to the safe operation of the reactor. Therefore, targets used for isotope production typically require specialized and targeted designs.

[0005] Currently, most research or experimental reactors worldwide that can be used for isotope production primarily serve tasks such as material irradiation and neutron beam extraction, and have few reserved channels for isotope production (or are single-channel designs), resulting in limited isotope production.

[0006] Chinese patent CN202111491938.4 discloses a neutron hospital reactor specifically designed for medical applications. The reactor includes a core housed in a water tank, both inside and outside of which are filled with light water coolant. The core comprises fuel assemblies and control rods, and is surrounded by a graphite reflector layer. An operating bridge is located at the top of the water tank, and a target / fuel assembly handling mechanism is mounted on the bridge. This mechanism is connected to the core via a target handling conduit. Target irradiation grids are positioned at the four corners of the core, and isotope production targets are placed within these grids. The size of each target irradiation grid matches the size of the fuel assemblies. Each grid is divided into four equal parts with a cross-section resembling a grid, and four isotope production targets are positioned within each grid. The fuel assemblies are rectangular prism-shaped, with plate-shaped fuel elements inserted within them.

[0007] The neutron hospital reactor disclosed in the aforementioned patent document can be equipped with a total of 16 targets for isotope production. Although this increases the number of targets in the reactor to some extent, the isotope production targets used are still traditional cylindrical targets, and the targets are installed at the four corners of the reactor core. The overall utilization rate of fission neutrons is not high, and the overall isotope production still needs to be improved.

[0008] Therefore, traditional research or experimental reactors that can be used for isotope production have few reserved channels for isotope production and low neutron utilization, resulting in limited isotope production. There is an urgent need to design a reactor core design specifically for isotope production in order to improve isotope yield and meet the isotope needs of the medical and health fields. Summary of the Invention

[0009] This application provides an irradiation target and an isotope production reactor for producing isotopes, in order to solve the problem of low isotope production in existing reactors.

[0010] To achieve the above objectives, this application provides the following technical solution:

[0011] This application provides an irradiation target for isotope production, comprising an outer shell, the outer shell being a cylindrical structure extending vertically, the cylindrical structure including multiple ducts converging at a point; the multiple ducts being equally spaced around the converging point; along the axial direction of the outer shell, several target layers are equally spaced within the multiple ducts; each target layer includes multiple irradiation microspheres equally spaced within each duct along the cross-sectional direction of the outer shell; the gaps between adjacent irradiation microspheres, and between the irradiation microspheres and the outer shell, are filled with helium gas;

[0012] After multiple wing passages converge, several short wings are formed around the convergence point, and a region for setting up fuel assemblies is formed between two adjacent short wings; the length of one of the short wings is less than the radial diameter of the fuel assembly.

[0013] Furthermore, in the above technical solution, the cylindrical structure includes two wing channels that intersect at a point; the two wing channels are perpendicular to each other, forming a cylindrical structure with a cross-shaped cross-section, and several target layers are equally spaced within the two wing channels along the axial direction of the outer shell; the target layer includes multiple irradiation spheres equally spaced within the two wing channels along the cross-sectional direction of the outer shell; after the two wing channels intersect, four short side wings are formed with the intersection point as the center, and a fuel assembly is disposed between two adjacent short side wings.

[0014] Furthermore, one of the target layers includes a plurality of irradiated spheres arranged in a single row at equal intervals in one of the wing channels, and a plurality of irradiated spheres arranged in a single row at equal intervals in another of the wing channels; the interval between two adjacent irradiated spheres in each wing channel is equal.

[0015] Furthermore, the spacing between two adjacent target layers is equal to the spacing between two adjacent irradiated spheres in each duct.

[0016] Furthermore, the outer shell is a steel outer shell; along the cross-sectional direction of the outer shell, the lengths of any two short wings are the same.

[0017] Furthermore, the irradiated microsphere is made of uranium oxide; the irradiated microsphere contains nuclear fuel, which is U-235 with a concentration of ≤20%.

[0018] On the other hand, based on the aforementioned irradiation target for isotope production, this application provides an isotope production reactor, the isotope production reactor including a core and a core reflector surrounding the core; the core includes a central fuel assembly, and a plurality of irradiation targets and a plurality of fuel assemblies surrounding the central fuel assembly.

[0019] Furthermore, in the above technical solution, multiple irradiation targets are evenly arranged in multiple rings at equal intervals around the central fuel assembly, and the irradiation targets and the fuel assembly are arranged at intervals.

[0020] Furthermore, the two winglets intersect to form four fan-shaped regions with an included angle of 90°, and each fan-shaped region is provided with one of the fuel assemblies.

[0021] Furthermore, after the two winglets intersect, four short wings are formed with the intersection point as the center, and the length of one of the short wings is less than the radial diameter of the fuel assembly.

[0022] Furthermore, the axial height of the irradiated target is higher than the height of the active region in the reactor core.

[0023] Furthermore, the reactor core is placed in a reactor pool filled with coolant, and a target drive mechanism is provided above the reactor pool to move the irradiation target up and down, so that the irradiation target can be inserted into or removed from the reactor core.

[0024] Furthermore, one of the irradiation targets corresponds to one of the target drive mechanisms.

[0025] Compared with the prior art, this application has the following advantages:

[0026] 1. This application provides an irradiation target for isotope production. The irradiation target includes an outer shell, which is a cylindrical structure. The cylindrical structure includes at least two ducts that intersect at a point. The two ducts are perpendicular to each other, forming a cross-shaped cylindrical structure. Along the axial direction of the outer shell, several target layers are equally spaced within the two ducts. Each target layer includes multiple irradiated spheres equally spaced within the two ducts along the cross-sectional direction of the outer shell. The gaps between adjacent irradiated spheres and between the irradiated spheres and the outer shell are filled with helium gas. Therefore, the irradiation target provided by this application includes multiple irradiated spheres, which increases the total amount of nuclear fuel stored in the irradiation target, more effectively utilizes thermal neutrons, and increases the isotope production rate.

[0027] 2. Based on the irradiation target for isotope production provided in this application, this application also provides an isotope production reactor. The reactor includes a core, a central fuel assembly, and multiple irradiation targets and multiple fuel assemblies arranged around the central fuel assembly. The irradiation targets and fuel assemblies are spaced apart, with a consistent spacing between any two adjacent irradiation targets. This application increases the spacing between fuel assemblies based on the core arrangement of a general research reactor and arranges irradiation targets with a cross-shaped cross-section between the fuel assemblies. The spacing between fuel assemblies is larger than that of traditional low-power research reactors using similar assemblies, thereby introducing more moderators, enhancing neutron moderation in the assembly gaps, and resulting in a softer neutron spectrum that is beneficial for increasing the yield of medical isotopes.

[0028] 3. In the reactor provided by this application, the cross-shaped irradiation target is arranged between the fuel assemblies, which can provide positive reactivity. After the irradiation target is removed from the core, the reactivity of the core can be reduced. It can participate in the core reactivity control together with the control rods, that is, it provides an additional reactivity control protection. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing this application; for example, based on the technical concepts disclosed in this application and the exemplary drawings, those skilled in the art are able to easily make conventional adjustments or further optimizations to the addition / reduction / classification, specific shapes, positional relationships, connection methods, and size ratios of certain units (components).

[0030] Figure 1 This is a schematic diagram of the planar structure of an irradiation target for producing isotopes provided in this application in one embodiment. The diagram also shows the positional relationship between the irradiation target and the fuel assembly disposed around it.

[0031] Figure 2 This is a schematic planar structure diagram of a partial structure of a reactor core provided in this application in one embodiment;

[0032] Figure 3 This is a schematic diagram of the arrangement of multiple target layers on a horizontal plane in an irradiation target provided in this application in one embodiment;

[0033] Figure 4 This is a schematic diagram of the multi-layer target material provided in this application arranged vertically adjacent to each other in a vertical plane in one embodiment of the irradiation target.

[0034] Explanation of reference numerals in the attached figures:

[0035] 1. Outer shell; 2. Irradiated sphere; 3. Fuel assembly; 4. Irradiated target; 5. Moderator channel; 6. Target layer; 7. Air duct; 8. Central fuel assembly. Detailed Implementation

[0036] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] In the description of this application: unless otherwise stated, "a plurality of" means two or more. The terms "first," "second," "third," etc., in this application are intended to distinguish the objects referred to and do not have any special meaning in terms of technical connotation (e.g., they should not be construed as an emphasis on importance or order). Expressions such as "comprising," "including," and "having" also mean "not limited to" (certain units, components, materials, steps, etc.).

[0038] The terms used in this application, such as "upper," "lower," "left," "right," and "middle," are generally used to facilitate intuitive understanding by referring to the accompanying drawings, and are not absolute limitations on the positional relationships in the actual product. Changes in these relative positional relationships, without departing from the technical concept disclosed in this application, should also be considered within the scope of this application.

[0039] Example 1

[0040] Existing irradiation reactors are mainly used for material irradiation. The number of irradiation targets in the reactor core is limited. In addition, because the targets in the irradiation channels are metal foils, the amount of metallic uranium is low, resulting in low isotope production.

[0041] To address the problems existing in the prior art, this application provides an irradiation target and an isotope production reactor for isotope production. The irradiation target is inserted into an irradiation channel within the reactor. The irradiation target utilizes the high neutron flux field within the reactor to initiate a nuclear fission reaction in the target material, thereby separating and extracting the target isotope from the fission products. The reactor provided in this application has a larger core target capacity, which can increase isotope yield and improve economic efficiency.

[0042] The structure of an irradiation target for isotope production provided in this embodiment is described in detail below:

[0043] This embodiment provides an irradiation target for isotope production, see [link to documentation]. Figure 1 The system includes an outer shell 1, which is a cylindrical structure extending vertically. The cylindrical structure includes two converging ducts 7. The two ducts 7 are perpendicular to each other, forming a cross-shaped cylindrical structure. Along the axial direction of the outer shell 1, several target layers 6 are evenly spaced within the two ducts 7. Each target layer 6 includes multiple irradiated microspheres 2, evenly spaced within the two ducts 7 along the cross-sectional direction of the outer shell 1. The gaps between adjacent irradiated microspheres 2, and between the irradiated microspheres 2 and the outer shell 1, constitute a moderator channel 5, which is filled with helium. That is, a small gap is left between the outer shell and the irradiated microspheres. This small gap can be used to encapsulate fission products such as fission gases, while also allowing for irradiation expansion of the target material. This small gap is filled with helium, which enhances heat transfer between the microspheres and the inner shell.

[0044] In the aforementioned irradiation target, with the intersection point as the center, the two air ducts form four fan-shaped areas with an included angle of 90°. These fan-shaped areas are used to install fuel assemblies. See also Figure 3 , 4Each target layer comprises multiple irradiated spheres arranged in a single row at equal intervals in one duct and multiple irradiated spheres arranged in a single row at equal intervals in another duct. The spacing between any two adjacent irradiated spheres in each duct is equal. Furthermore, the spacing between any two adjacent target layers is equal to the spacing between any two adjacent irradiated spheres in each duct. This arrangement is primarily to ensure that the spacing between any two adjacent irradiated spheres (vertically, horizontally, or longitudinally) remains consistent within space, thus preventing the formation of localized hotspots during irradiation.

[0045] The outer casing of the irradiation target provided in this embodiment is made of steel. The irradiation spheres described above can be made of uranium oxide. The irradiation spheres contain nuclear fuel, specifically U-235 with a concentration ≤20%.

[0046] In a specific arrangement example, multiple irradiated spheres can be arranged in the outer shell of the target with a cross-shaped cross section. Specifically, nine irradiated spheres can be arranged along the cross-sectional direction of the outer shell (i.e., on the horizontal plane), and a total of 45 target layers can be arranged along the axial direction of the outer shell (i.e., in the vertical direction). The outer shell contains a total of 9 × 45 = 405 irradiated spheres.

[0047] The target provided in this application has a cross-shaped cross-section and contains a number of irradiated spheres for isotope production. This outer shell is like a basket containing a number of spheres. The more irradiated spheres there are, the more nuclear fuel can be stored in the target. Thermal neutrons can be used more effectively in the reaction, thus increasing the isotope yield. This solves the problem of low isotope yield in general research reactors or experimental reactors.

[0048] Example 2

[0049] Based on the irradiation target for isotope production provided in Embodiment 1, this embodiment provides an isotope production reactor, which includes a core and a core reflector surrounding the core; see also Figure 2 The reactor core includes a central fuel assembly 8, and multiple irradiation targets 4 and multiple fuel assemblies 3 surrounding the central fuel assembly 8. The axial height of the irradiation targets is higher than the height of the active region of the reactor core. The reactor core is placed in a reactor pool filled with coolant. A target drive mechanism is located above the reactor pool to move the irradiation targets up and down, allowing them to be inserted into or removed from the reactor core. Target replacement is accomplished by lifting the irradiation target upwards using the target drive mechanism. Each irradiation target corresponds to one target drive mechanism, and each irradiation target is equipped with an independent drive device for independent adjustment or replacement.

[0050] The irradiation target provided in Example 1 is installed in the reactor core. Multiple irradiation targets are evenly arranged in multiple rings around the central fuel assembly. The irradiation targets and fuel assemblies are arranged at intervals, and the spacing between any two adjacent irradiation targets is consistent. After the two wing channels intersect, four fan-shaped areas with an included angle of 90° are formed. Each fan-shaped area is equipped with a fuel assembly. After the two wing channels intersect, four short wings are formed around the intersection point. The length of one short wing is less than the radial diameter of the fuel assembly to prevent jamming when the irradiation target moves.

[0051] See Figure 2 The diagram shows 12 irradiation targets 4 in the reactor core.

[0052] The fuel assemblies in the reactor provided in this application are the same as those in a common low-power research reactor. The core assembly still uses square fuel assemblies, which are composed of fuel plates. However, this application increases the gaps between fuel assemblies based on the common research reactor core arrangement, and arranges cross-shaped irradiation targets, as provided in Example 1, between the fuel assemblies. In the reactor provided in this application, the fuel assembly spacing is larger than that of traditional low-power research reactors using similar assemblies, thereby introducing more moderators and enhancing neutron moderation in the assembly gaps. The softer neutron spectrum is beneficial for increasing the yield of medical isotopes.

[0053] Cross-shaped irradiation targets can be distributed in multiple locations within the reactor core. Each target contains tiny irradiation spheres containing low-enriched uranium (U-235 concentration ≤ 20%). Major medical isotopes, such as Mo-99 and I-131, are obtained by inducing fission reactions in U-235 through neutron irradiation in the reactor. These cross-shaped targets can be lifted or inserted into the core by a target drive mechanism, allowing for flexible target replacement or control of reactor reactivity in emergency situations.

[0054] This application incorporates a cross-shaped irradiation target between fuel assemblies. The irradiation target contains isotope production spheres (i.e., irradiation spheres), which can increase the amount of uranium fuel stored in the target and solve the problem of low isotope production in general research or experimental reactors.

[0055] In the reactor provided by this application, the cross-shaped irradiation target is arranged between the fuel assemblies, which can provide positive reactivity. After the irradiation target is removed from the core, the core reactivity can be reduced. It can participate in the core reactivity control together with the control rods, that is, it provides an additional reactivity control protection.

[0056] The technical features of the above embodiments can be combined in any way (as long as there is no contradiction in the combination of these technical features). For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; these embodiments not explicitly written should also be considered to be within the scope of this specification.

[0057] The present application has been described in a relatively specific and detailed manner above through general descriptions and specific embodiments. It should be understood that, based on the technical concept of the present application, several conventional adjustments or further innovations can be made to these specific embodiments; however, as long as they do not depart from the technical concept of the present application, the technical solutions obtained by these conventional adjustments or further innovations also fall within the protection scope of the claims of the present application.

Claims

1. An irradiation target for producing isotopes, characterized in that, The device includes an outer shell, which is a cylindrical structure extending vertically. The cylindrical structure includes multiple ducts that converge at a single point. The multiple ducts are equally spaced around the convergence point. Along the axial direction of the outer shell, several target layers are equally spaced within each of the multiple ducts. Each target layer includes multiple irradiated microspheres equally spaced within each duct along the cross-sectional direction of the outer shell. Helium gas is filled in the gaps between adjacent irradiated microspheres and between the irradiated microspheres and the outer shell. After multiple wing passages converge, several short wings are formed around the convergence point, and a region for setting up fuel assemblies is formed between two adjacent short wings; the length of one of the short wings is less than the radial diameter of the fuel assembly.

2. The irradiation target for isotope production according to claim 1, characterized in that, The cylindrical structure includes two wing channels that intersect at a point; the two wing channels are perpendicular to each other, forming a cylindrical structure with a cross-shaped cross-section. Along the axial direction of the outer shell, several target layers are equally spaced within the two wing channels; each target layer includes multiple irradiation microspheres equally spaced within the two wing channels along the cross-sectional direction of the outer shell. After the two winglets intersect, four short wings are formed with the intersection point as the center, and fuel assemblies are arranged between adjacent short wings.

3. The irradiation target for isotope production according to claim 1, characterized in that, The target layer includes a plurality of irradiated spheres arranged in a single row at equal intervals in one of the wing passages, and a plurality of irradiated spheres arranged in a single row at equal intervals in another of the wing passages; the interval between two adjacent irradiated spheres in each wing passage is equal; The spacing between two adjacent target layers is equal to the spacing between two adjacent irradiated spheres in each duct.

4. The irradiation target for isotope production according to claim 1, characterized in that, The outer shell is made of steel; along the cross-sectional direction of the outer shell, the lengths of any two of the short wings are the same.

5. The irradiation target for isotope production according to claim 1, characterized in that, The irradiated spheres are made of uranium oxide. The irradiated microspheres contain nuclear fuel, which is U-235 with a concentration of ≤20%.

6. An isotope production reactor, characterized in that, The reactor includes an irradiation target for isotope production as described in any one of claims 1-5; the isotope production reactor includes a core and a core reflector surrounding the core; the core includes a central fuel assembly, and a plurality of the irradiation targets and a plurality of fuel assemblies surrounding the central fuel assembly.

7. The isotope production reactor according to claim 6, characterized in that, Multiple irradiation targets are evenly arranged in multiple rings around the central fuel assembly at equal intervals, with the irradiation targets and the fuel assembly arranged at intervals. The two winglets intersect to form four fan-shaped regions with an included angle of 90°, and each fan-shaped region is equipped with one of the fuel assemblies; After the two winglets intersect, four short wings are formed with the intersection point as the center, and the length of one of the short wings is less than the radial diameter of the fuel assembly; The axial height of the irradiated target is higher than the height of the active region in the reactor core.

8. The isotope production reactor according to claim 7, characterized in that, The reactor core is placed in a reactor pool filled with coolant. A target drive mechanism is provided above the reactor pool to move the irradiation target up and down, so that the irradiation target can be inserted into or removed from the reactor core. One of the irradiation targets corresponds to one of the target drive mechanisms.

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