A fuel assembly for producing isotopes in a nuclear reactor

Abstract

The invention relates to the technical field of isotope production in nuclear power plants, and specifically discloses a fuel assembly for producing isotopes in a nuclear reactor, comprising an outer cladding, an upper seal, a lower seal, a mother material and a UO2 pellet block, wherein the outer cladding is a tubular structure, the upper seal and the lower seal are respectively arranged at two ends of the outer cladding, the mother material and the UO2 pellet block are both arranged inside the outer cladding, and the mother material and the UO2 pellet block are arranged in a nested manner; the invention compensates for the influence of the mother material absorbing neutrons on the reactivity of the fuel rod by adjusting the enrichment and size of the UO2 pellet block, greatly reduces the influence of the target on the reactivity and power peak factor of the nuclear power plant core, ensures that the thermal performance does not change significantly, and ensures the safety of the nuclear power plant; realizes the mutual independence of the UO2 fuel rod and the mother material rod, disassembles the mother material rod for producing isotopes after irradiation in the nuclear power plant and transports it to a hot chamber for separation and purification, greatly reduces the difficulty of separation and purification between the mother material and UO2.

Description

Technical Field

[0001] The invention relates to the technical field of isotope production in nuclear power plants, in particular to a fuel assembly used for producing isotopes in nuclear reactors. Background Art

[0002] Radioisotopes are widely used in biomedicine, industry, and agricultural production. In medicine, isotopes are mainly used for imaging, diagnosis, and treatment. Industrial applications mainly include process control and optimization, measurement and automation, quality control, and various tests. Agricultural applications mainly include isotope radiation breeding technology and isotope tracing technology. At present, there are two main ways to produce radioisotopes: research reactors and cyclotrons. The production of radioisotopes in research reactors has great advantages in production scale, stability, and production efficiency, and has become the most important means of producing radioisotopes. In addition, since research reactors can provide neutrons with different energy spectra and a large irradiation space, especially with reserved irradiation channels, isotope production in research reactors has the advantages of little impact on reactors, high safety, a wide variety of irradiated samples, simple target preparation, and simple irradiation operation. Therefore, research reactors are generally used to produce radioisotopes. For example, the United States uses ATR research reactors and HFIR research reactors to produce Pu-238 isotopes, Canada uses NRU research reactors to produce isotopes such as Co-60, C-14 and Tc-99m, and Russia uses Ruslan research reactors to produce isotopes such as C-14, Co-60 and Ir-192.

[0003] Since the research reactors, radioisotope R&D and production facilities built earlier have been in service for many years, as their service life expires, many research reactors at home and abroad have gradually begun to shut down, and the irradiation resources of research reactors that produce isotopes have begun to become scarce resources. Therefore, it is necessary to find a new isotope production method to replace the production of isotopes in research reactors. Using nuclear power plants (including pressurized water reactors and heavy water reactors) to produce radioisotopes has become a new option for isotope production. However, since radioisotope materials have a certain neutron absorption capacity, directly making them into fuel rods and placing them in nuclear power plants will affect the neutron flux distribution of the power plant, resulting in the safety performance and power generation performance of the power plant being affected.

[0004] CN201711297364 "A device for producing Pu-238 by irradiation using a commercial pressurized water reactor" discloses a method and device for producing Pu-238 by using a commercial pressurized water reactor. The device is a fuel assembly arranged in the core of a commercial pressurized water reactor, containing Np-237 target rods, and a water cavity to replace one or more fuel rods in the fuel assembly, to obtain Np-237 irradiated target grid elements for the production of Pu-238. The disadvantage of this scheme is that the parent material (Np-237) of the target will strongly absorb neutrons, which will affect the normal power generation and economy of the nuclear power plant. In order to reduce this effect, it is necessary to increase the enrichment of U-235 in other fuel rods in the fuel assembly, which will cause the power peak factor of the local fuel rod to further increase, affecting the safety of the nuclear power plant. Summary of the invention

[0005] The object of the present invention is to provide a fuel assembly for producing isotopes in a nuclear reactor to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a fuel assembly for producing isotopes in a nuclear reactor, comprising an outer cladding, an upper seal, a lower seal, a parent material and UO 2 The core block, the outer shell is a tubular structure, the upper seal and the lower seal are respectively arranged at the two ends of the outer shell, the parent material, UO 2 The core blocks are all arranged inside the outer shell, and the parent material, UO 2 The core blocks are arranged in a nested manner.

[0007] Preferably, the UO 2 The core block is set as a ring structure with a central opening, and the parent material is set as a thin-diameter core block or core rod; 2 The core blocks are stacked in the outer shell to form an annular core block stack or core tube, and the parent material is arranged in the UO 2 The inner side of the core block ring.

[0008] Preferably, the parent material is set as an annular core block, and the UO 2 The core block is a solid core block; the parent material is stacked in the outer shell into an annular core block stack or core tube, UO 2 The core block is arranged in cooperation with the inner side of the parent material ring.

[0009] Preferably, the parent material, UO 2 An inner shell is arranged between the core blocks.

[0010] Preferably, the parent material is a material containing a parent material nuclide with a thermal neutron macroscopic absorption cross section of less than 1 barn, or a high thermal conductivity dispersion.

[0011] Preferably, the material having a thermal neutron macroscopic absorption cross section of less than 1 barn includes, but is not limited to, the following nuclear-grade materials: aluminum alloy, zirconium alloy, magnesium alloy, aluminum oxide, zirconium oxide, magnesium oxide, silicon dioxide, zirconium carbide, and silicon carbide.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] 1. The target of the present invention is adjusted by UO 2 The enrichment and size of the pellets compensate for the influence of the neutron absorption of the parent material on the reactivity of the fuel rods, so that the fuel rods containing the production isotope targets have equivalent reactivity to the fuel rods in the original position, thereby greatly reducing the influence of the targets on the reactivity and power peak factor of the nuclear power plant core, and ensuring that the thermal performance does not change significantly, thus ensuring the safety of the nuclear power plant; in addition, during the operation of the nuclear power plant, isotope production can be achieved by simply replacing the fuel rods, and the overall structural design and size of the fuel assembly have not changed. The outer dimensions of the isotope target are also exactly the same as those of the fuel rod cladding tube, and have very good compatibility with the existing fuel assemblies of the nuclear power plant in terms of structure and interface, thus greatly simplifying the safety analysis of the fuel assembly;

[0014] 2. UO is also implemented 2 The fuel rods and the parent material rods are independent of each other. The irradiated parent material rods for producing isotopes can be directly disassembled in the nuclear power plant and transported to the hot chamber for separation and purification, which greatly reduces the risk of parent material and UO 2 The difficulty of separation and purification;

[0015] 3. Designing a low neutron absorption cross-section, high thermal conductivity dispersion containing the nuclides of the parent material into the parent material can improve the processing and forming performance of the parent material, increase the thermal conductivity, reduce the temperature of the parent material, improve the capacity to contain radioactive products, and facilitate subsequent separation and purification. While maintaining the geometric shape, it can also disperse the nuclides of the parent material, thereby reducing the self-screening effect and improving the efficiency of isotope production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the present invention;

[0017] Figure 2 The ring UO of the present invention 2 Schematic diagram of the core block structure;

[0018] Figure 3 It is a schematic diagram of the annular base material of the present invention;

[0019] Numbers in the figure: 1, outer shell; 2, upper seal; 3, lower seal; 4, inner shell; 5, parent material; 6, UO 2 Core block. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be noted that the terms "vertical", "up", "down", "horizontal", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying 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 the present invention.

[0022] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] See also Figure 1-3 The present invention provides a technical solution: a fuel assembly for producing isotopes in a nuclear reactor, comprising an outer cladding 1, an upper seal 2, a lower seal 3, a parent material 5 and UO 2 The core block 6, the outer shell 1 is a tubular structure, the upper seal 2 and the lower seal 3 are respectively arranged at the two ends of the outer shell 1, the parent material 5, UO 2 The core blocks 6 are all arranged inside the outer shell 1, and the parent material 5, UO 2 The core blocks 6 are arranged in a nested manner.

[0024] Furthermore, the UO 2 The core block 6 is set as a ring structure with a central opening, and the parent material 5 is set as a thin-diameter core block or core rod; 2 The core blocks 6 are stacked in the outer shell 1 to form an annular core block stack or core tube, and the parent material 5 is arranged in the UO 2 The core block 6 has an annular inner side.

[0025] Furthermore, the parent material 5 is configured as an annular core block, and the UO 2 The core block 6 is a solid core block; the parent material 5 is stacked in the outer shell 1 into an annular core block stack or core tube, UO 2 The core block 6 is arranged in cooperation with the inner side of the parent material 5 in an annular shape.

[0026] Furthermore, the base material 5, UO 2 An inner shell 4 is arranged between the core blocks 6 .

[0027] Furthermore, the matrix material 5 is configured as a material containing a nuclide of the matrix material 5 with a thermal neutron macroscopic absorption cross section of less than 1 barn, or a high thermal conductivity dispersion.

[0028] Furthermore, the material having a thermal neutron macroscopic absorption cross section of less than 1 barn includes, but is not limited to, the following nuclear-grade materials: aluminum alloy, zirconium alloy, magnesium alloy, aluminum oxide, zirconium oxide, magnesium oxide, silicon dioxide, zirconium carbide, and silicon carbide.

[0029] Embodiment 1

[0030] The radioisotope material NpO 2 The mother material 5 is prepared into a 3mm thick annular core block, the outer diameter of the mother material 5 is 12mm, and the inner diameter is 5.7mm, and is loaded into the outer shell 1 of the zirconium alloy. 2 It is prepared by mixing with Zr powder, the volume fraction of Zr powder is not less than 30%, the density after pressing is about 80%, and the density can reach more than 95% by sintering.

[0031] UO 2 The pellet 6 was prepared as a solid pellet with a diameter of 5.5 mm, and the enrichment of U-235 was increased to 25.8%. 2 The pellet 6 is placed in the radioisotope material NpO 2 In the annular base material 5 core block, the specific form is as follows Figure 3 shown.

[0032] Base material 5 and UO 2 The core blocks 6 are independent of each other and can be directly disassembled in the nuclear power plant. 2 And transport it to the hot chamber for separation and purification, the difficulty of separation is greatly reduced, and NpO 2 High utilization rate and high efficiency in producing Pu-238.

[0033] Embodiment 2

[0034] Using ring UO 2 Core block 6 is designed with a ring-shaped UO with a wall thickness of 2.5 mm. 2 The core block 6 has an outer diameter of 12 mm and an inner diameter of 7 mm, and the U-235 enrichment is increased to 30%, and is loaded into the outer shell 1.

[0035] NpO 2 Base material 5 is made of NpO 2Mixed with SiC powder to prepare a 5.5mm diameter base material 5, the volume fraction of SiC powder is not less than 30%, the density after pressing is about 80%, and the density can reach more than 95% after sintering. 2 The parent material 5 is loaded into the zirconium alloy inner cladding 4 to prepare a thin-diameter rod. The outer diameter of the inner cladding 4 is 6.85 mm and the inner diameter is 5.7 mm.

[0036] The prepared NpO 2 The parent material 5 is placed in the ring UO 2 In the core block 6, Figure 2 As shown. 2 and NpO 2 Independent of each other and can be separated directly.

[0037] Embodiment 3

[0038] The radioisotope material TeO 2 The parent material 5 is prepared into a ring-shaped core block with a wall thickness of 2 mm, an outer diameter of 11.2 mm, and an inner diameter of 7.2 mm, and is loaded into the outer shell 1 of the zirconium alloy. The parent material 5 core block is made of TeO 2 It is prepared by mixing with alumina powder, the volume fraction of alumina powder is not less than 40%, the density after pressing is about 85%, and the density can reach more than 95% after sintering.

[0039] UO 2 The pellet 6 was prepared as a solid pellet with a diameter of 5.7 mm, and the enrichment of U-235 was increased to 46.7%. 2 The core block 6 is placed in the zirconium alloy inner cladding 4 to prepare a thin diameter rod. The zirconium alloy inner cladding is 46.8 mm and the inner diameter is 5.7 mm. 2 The pellet 6 is placed in the radioisotope material TeO 2 In the annular core block, the specific form is as follows Figure 3 shown.

[0040] UO 2 Pellets 6 and TeO 2 The parent materials 5 are independent of each other and can be directly disassembled in the nuclear power plant. 2 The parent material 5 is transported to the hot chamber for separation and purification, and the difficulty of separation is greatly reduced.

[0041] Embodiment 4

[0042] Using ring UO 2 Core block 6 is designed to select a ring-shaped UO with a wall thickness of 1 mm. 2 The core block 6 has an outer diameter of 8.2 mm and an inner diameter of 6 mm, and the U-235 enrichment is increased to 82%, and is loaded into the outer shell 1 of the zirconium alloy.

[0043] Yb 2 O 3 The fine-diameter core block or core rod with a diameter of 5.8 mm is prepared by mixing with ZrC powder as the base material 5, the volume fraction of ZrC powder is not less than 45%, the density after pressing is about 82%, and the density can reach more than 95% by sintering.

[0044] The prepared Yb 2 O 3 The core block or core rod is placed in the ring UO 2 In the core block 6, Figure 2 As shown. 2 and Yb 2 O 3 Independent of each other, they can be separated directly after irradiation.

[0045] One or more targets are used as combustion rods to form a combustion assembly. The targets described in Embodiments 1 to 4 can replace fuel rods with the same reaction characteristics in the fuel assembly. The fuel rods containing the matrix material 5 can be distributed in multiple fuel assemblies of the reactor.

[0046] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A fuel assembly for producing isotopes in a nuclear reactor, characterized in that: The invention comprises an outer shell (1), an upper seal (2), a lower seal (3), a mother material (5) and a UO2 pellet (6); the outer shell (1) is a tubular structure; the upper seal (2) and the lower seal (3) are respectively arranged at two ends of the outer shell (1); the mother material (5) and the UO2 pellet (6) are both arranged inside the outer shell (1); the mother material (5) and the UO2 pellet (6) are arranged in a nested manner; the mother material (5) is arranged as a high thermal conductivity-based dispersion containing a material having a thermal neutron macroscopic absorption cross section of a nuclide of the mother material (5) of less than 1 barn.

2. A fuel assembly for producing isotopes in a nuclear reactor according to claim 1, characterized in that: The UO2 core block (6) is configured as an annular structure with a central opening, and the parent material (5) is configured as a thin-diameter core block or a core rod; the UO2 core blocks (6) are stacked in the outer shell (1) to form an annular core block stack or a core tube, and the parent material (5) is arranged in cooperation with the inner side of the annular shape of the UO2 core block (6).

3. A fuel assembly for producing isotopes in a nuclear reactor according to claim 1, characterized in that: The mother material (5) is configured as an annular core block, and the UO2 core block (6) is a solid core block; the mother material (5) is stacked in the outer shell (1) into an annular core block stack or core tube, and the UO2 core block (6) is arranged in cooperation with the inner side of the annular core of the mother material (5).

4. A fuel assembly for producing isotopes in a nuclear reactor according to claim 1, characterized in that: An inner cladding (4) is provided between the parent material (5) and the UO2 core block (6).

5. A fuel assembly for producing isotopes in a nuclear reactor according to claim 1, characterized in that: The materials having a thermal neutron macroscopic absorption cross section of less than 1 barn include, but are not limited to, the following nuclear-grade materials: aluminum alloy, zirconium alloy, magnesium alloy, aluminum oxide, zirconium oxide, magnesium oxide, silicon dioxide, zirconium carbide, and silicon carbide.

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