Target rod for irradiation production of < 60 > Co in pressurized water reactor and target piece comprising same

Abstract

The invention relates to the technical field of nuclear reactors, and provides a target rod for irradiation production of 60Co in a pressurized water reactor in order to solve the problems of irradiation production of 60Co in the pressurized water reactor and improvement of the specific activity of the 60Co produced by irradiation of the pressurized water reactor, the target rod comprises an outer target rod cladding and a plurality of target piece boxes arranged in the target rod cladding, the target piece box comprises a target piece box cladding and a target core block arranged in the target piece box cladding, and the target core block comprises a cobalt core block and a zirconium alloy core block which are sequentially stacked at intervals in the axial direction of the target piece box cladding; the method can be applied to the pressurized water reactor, the specific activity of < 60 > Co produced by irradiation of the cobalt core block in the pressurized water reactor is improved, and the activity requirement of a cobalt source is met.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear reactors, and in particular to a method for producing irradiation in a pressurized water reactor. 60 A Co target rod and a target piece containing the same. Background Art

[0002] 60 Co is a beta- - Decaying nuclides, emitting beta - and gamma rays, beta - The maximum energy of the ray is 0.315MeV, and the energies of gamma rays are 1.3325MeV and 1.1732MeV. 60 Co is a good source of gamma radiation and is widely used in industry and medicine.

[0003] International production 60 The main countries producing Co isotopes are Canada, the Russian Federation and the Argentine Republic. China has been producing Co by irradiation at two heavy water reactors at Qinshan Nuclear Power Plant since 2008. 60 Co. For example, a Chinese patent with publication number CN107710333A discloses a method for producing radioactive isotopes using a heavy water nuclear power plant, in which a target is inserted into a heavy water moderator through a guide tube in a port in a reactive mechanism deck of a heavy water reactor, and the target is irradiated during operation of the reactor, thereby converting the target into a radioactive isotope. A Chinese patent with publication number CN114758810A discloses a device for producing isotopes by online irradiation using a heavy water reactor detector channel, through which an isotope production target can be placed in a redundant flux detector channel in a flux detector assembly in a heavy water reactor, and the device can be flexibly assembled and disassembled, and the reactor does not need to be permanently changed, and multiple isotopes can be produced online without affecting the normal operation of the reactor.

[0004] The above-mentioned existing technologies all propose methods for producing isotopes by irradiation for heavy water reactors. However, the heavy water reactor units in Canada and the Russian Federation will face decommissioning and overhaul, which will lead to 60 The annual production of Co isotopes has declined and cannot meet the needs of the international market. And because the core structure and operation mode of PWRs are quite different from those of HWRs, the above method is not applicable to PWRs. In addition, the average thermal neutron flux density in HWRs is about 2*10 14 n / cm 2 / s level, which is higher than the average thermal neutron flux density in a pressurized water reactor (about 4*10 13 n / cm 2 / s level), in order to make the isotope yield of PWR irradiation target production as high as possible, it is necessary to further optimize the target design.

[0005] Therefore, in order to fill the gap in the domestic and even international markets, it is urgent to expand 60 However, the domestic heavy water reactor irradiation resources are limited, and heavy water reactors alone cannot meet the 60 Co production needs. Compared with heavy water reactors, domestic commercial pressurized water reactors have more units, stable operation, sufficient irradiation resources, and large-scale production. 60 The potential of Co.

[0006] For example, some research has been conducted in China on the production of isotopes by pressurized water reactor irradiation. 14 C and other isotopes. 14 C production, when used, AlN powder is encapsulated in a stainless steel target box, several target boxes are arranged axially and placed in a stainless steel cladding tube, the total height of all target boxes is the same as the active section of the fuel assembly, and the two ends are fixed with clamping parts to form a target rod. For example, for the production of other isotopes, there is also a ceramic target material encapsulated in a stainless steel cladding tube, the target material height is also the same as the active section of the fuel assembly, and the two ends are also fixed with clamping parts to form a target rod. Several target rods and choke rods together with the upper support plate, spring, guide cylinder and clamping rod are combined into a target, and the target is placed in the empty guide tube of the fuel assembly for isotope irradiation production.

[0007] Compared with domestic pressurized water reactor irradiation production 14 Most isotopes such as C are different, and irradiation production 60 The target material of Co is generally 59 Co metal pellets, after irradiation, are generally not post-processed, but are directly assembled into cobalt sources after being disassembled from the target. Therefore, all pellets should be 60 The specific activity of Co is as high as possible to meet the activity requirements of the cobalt source. 14 Most isotopes, such as C, generally need to be reprocessed after leaving the reactor to make other products, such as raw materials for radiopharmaceuticals. 14 The production of most isotopes such as C mainly considers the total activity when leaving the pile, and there is no strict requirement for the specific activity in the target material.

[0008] However, the thermal neutron flux density of a PWR is about 1 / 5 of that of a HWR. The same cobalt target will have a thermal neutron flux density of 1 / 5 of that of a HWR after the same irradiation time. 60 The specific activity of Co is relatively low and cannot meet the requirements of industrial or medical fields for the activity of cobalt sources. Therefore, it is necessary to design a target solution that can be used in pressurized water reactors and improve the efficiency of irradiation production in pressurized water reactors. 60 Co specific activity meets the activity requirements of cobalt source. Summary of the invention

[0009] The object of the present invention is to provide a method for producing irradiation in a pressurized water reactor. 60 Co target rod, which can be used in pressurized water reactors and improve the cobalt pellets produced by pressurized water reactor irradiation. 60 Co specific activity meets the activity requirements of cobalt source.

[0010] The embodiments of the present invention are implemented by the following technical solutions:

[0011] Irradiation production in a pressurized water reactor 60 The target rod of Co comprises an outer target rod cladding and a plurality of target box arranged in the target rod cladding.

[0012] The target box comprises a target box shell and a target core block arranged in the target box shell. The target core block comprises a cobalt core block and a zirconium alloy core block which are sequentially stacked and spaced along the axial direction of the target box shell.

[0013] Furthermore, the target box further comprises a pair of target box end plugs disposed in the target box shell, and the pair of target box end plugs are respectively located at the head and tail ends of the target core block.

[0014] Furthermore, the target core blocks are symmetrically distributed with the axial midpoint of the target box shell as the symmetry axis.

[0015] Furthermore, the density of the cobalt core block is 8.80±0.05 g / cm 3 .

[0016] Furthermore, the target rod cladding and the target box cladding are both filled with helium.

[0017] Furthermore, the target rod further comprises a pair of zirconium alloy positioning blocks symmetrically arranged in the target rod casing, and the pair of zirconium alloy positioning blocks are respectively located at the head and tail ends of the plurality of target boxes after placement.

[0018] Furthermore, the target rod further comprises a pair of target rod end plugs symmetrically arranged in the target rod casing, and the pair of target rod end plugs are respectively located at the head and tail ends of the pair of target rods.

[0019] Furthermore, the target box and the zirconium alloy positioning block are symmetrically distributed with the axial midpoint of the target rod cladding as the symmetry axis.

[0020] Irradiation production in a pressurized water reactor 60 The target of Co comprises a plurality of the above-mentioned target rods, wherein the plurality of target rods are distributed in a radially centrally symmetrical manner in the fuel assembly.

[0021] Furthermore, an even number of the target rods is provided, specifically, 4, 8, 12, 16, 20 or 24, and the axial height of the target rods is consistent with the height of the active section of the fuel assembly.

[0022] Furthermore, the target also includes a clamping component, and a plurality of choke rods fastened to a connecting plate of the clamping component through nuts and pins; the plurality of target rods are fastened to the connecting plate of the clamping component through nuts and pins.

[0023] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects:

[0024] The present invention is based on the use of pressurized water reactor irradiation production 60 Co and improve 60 For the purpose of Co specific activity, a 59 Co cobalt core blocks and zirconium alloy core blocks are arranged axially at intervals. The zirconium alloy core blocks themselves have weak neutron absorption capacity and thus have a large neutron flux density, which increases the neutron flux density of the cobalt core blocks adjacent to them, thereby weakening the spatial self-screening effect between the adjacent cobalt core blocks. When the energy spectrum in the cobalt core blocks remains basically unchanged, 59 Co undergoes (n,γ) reaction to generate 60 The cross section of Co is basically unchanged, and the increase of neutron flux density makes 59 Co undergoes (n,γ) reaction to generate 60 The reactivity of Co increases, which effectively improves the irradiation efficiency of the cobalt pellets in the core; at the same time, it can effectively increase the number of cobalt pellets in all cobalt pellets after irradiation of the irradiated target in a commercial pressurized water reactor for a specific time. 60 Specific activity of Co. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 A schematic diagram of the structure of a target rod provided in Example 1 of the present invention;

[0027] Figure 2 A schematic diagram of the structure of a target box provided in Example 1 of the present invention;

[0028] Figure 3 This is a schematic diagram of the structure of the target provided in Example 1 of the present invention.

[0029] Icons: 1-target rod, 11-target rod end plug, 12-target rod cladding, 13-positioning block, 14-target box, 141-target box end plug, 142-target box cladding, 143-zirconium alloy core block, 144-cobalt core block, 2-choke plug rod, 3-pressing component. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0031] Example 1

[0032] Irradiation production in a pressurized water reactor 60 The target rod of Co comprises an outer target rod cladding and a plurality of target box arranged in the target rod cladding.

[0033] The target box comprises a target box shell, a target core block arranged in the target box shell, and a pair of target box end plugs, wherein the pair of target box end plugs are respectively located at the head and tail ends of the target core block and are used to fix the position of the target box, and the outer diameter of the target box end plug is consistent with the outer diameter of the target box; the target core block comprises 59 The Co cobalt pellets and the zirconium alloy pellets, that is, the cobalt pellets and the zirconium alloy pellets are arranged in an "ABA" form in the axial direction until the entire target box is covered in the axial direction. In order to minimize the absorption of neutrons, the target box end plugs and the target box cladding materials are both made of zirconium alloy.

[0034] The present invention is based on the use of pressurized water reactor irradiation production 60 Co and improve 60 For the purpose of Co specific activity, a 59 Co cobalt core blocks and zirconium alloy core blocks are arranged axially at intervals. The zirconium alloy core blocks themselves have weak neutron absorption capacity and thus have a large neutron flux density, which increases the neutron flux density of the cobalt core blocks adjacent to them, thereby weakening the spatial self-screening effect between the adjacent cobalt core blocks. When the energy spectrum in the cobalt core blocks remains basically unchanged, 59 Co undergoes (n,γ) reaction to generate 60 The cross section of Co is basically unchanged, and the increase of neutron flux density makes 59 Co undergoes (n,γ) reaction to generate 60 The reactivity of Co increases, which effectively improves the irradiation efficiency of the cobalt pellets in the core; at the same time, it can effectively increase the number of cobalt pellets in all cobalt pellets after irradiation of the irradiated target in a commercial pressurized water reactor for a specific time. 60 Specific activity of Co.

[0035] In an embodiment, the target core blocks are symmetrically distributed with the axial midpoint of the target box shell as the symmetry axis.

[0036] In the embodiment, the density of the cobalt pellet is 8.80±0.05 g / cm 3 .

[0037] In an embodiment, the target rod further comprises a pair of positioning blocks arranged in the target rod shell, the pair of positioning blocks are respectively located at the head and tail ends of the target box; and are used to fix the position of the target box, and the outer diameter of the positioning blocks is consistent with the outer diameter of the target box.

[0038] In an embodiment, the target rod further comprises a pair of target rod end plugs disposed in the target rod cladding, and the pair of target rod end plugs are respectively located at both ends of a pair of positioning blocks; in order to minimize the absorption of neutrons, the materials of the target rod end plugs, the target rod cladding and the positioning blocks are all zirconium alloy.

[0039] In an embodiment, the target rod cladding and the target box cladding are both filled with helium for heat transfer and deformation prevention.

[0040] In an embodiment, the target box is centrally arranged in the axial middle area of ​​the target rod, that is, corresponding to the area with higher neutron flux density in the commercial pressurized water reactor, which will also make 59 Co undergoes (n,γ) reaction to generate 60 The increased reactivity of Co effectively improves the irradiation efficiency of the cobalt core blocks in the core.

[0041] Example 2

[0042] This embodiment provides a method for producing irradiation in a pressurized water reactor. 60 The Co target comprises the above-mentioned target rod, and a plurality of target rods are distributed in a radially centrally symmetrical manner in the fuel assembly.

[0043] More specifically, an even number of target rods are provided, and the axial height of the target rods is consistent with the height of the active section of the fuel assembly.

[0044] Example 3

[0045] This embodiment takes the CNP650 core of Qinshan Second Nuclear Power Plant as an example to further illustrate the specific implementation method of the present invention. The CNP650 core of Qinshan Second Nuclear Power Plant is composed of 121 groups of AFA3GAA fuel assemblies, and the refueling cycle of the CNP650 core is 18 months, and one refueling cycle corresponds to one irradiation cycle;

[0046] 1. Select 8 new fuel assemblies in the CNP650 core and arrange the irradiated targets of the present invention to form target assemblies. Each irradiated target comprises 8 target rods. The positions of the target rods in the assembly are as follows: Figure 1 As shown, 8 radially symmetrical ones are selected. To meet the requirements of cobalt source activity in industry or medical fields, the target assembly needs to be irradiated in the pile for 3 cycles;

[0047] 2. The axial height of the target rod is consistent with the height of the active section of the AFA3GAA fuel assembly, that is, 3657.60mm. The outer diameter of the target rod cladding is 9.50mm, the thickness is 0.57mm, and the height of the upper and lower plugs of the target rod is 10.00mm. 14 target boxes are loaded into the target rod, and the size of each target box is Φ8.00×212.13mm. There is a positioning cylinder at each end of the target rod, with a size of Φ8.00×333.89mm.

[0048] 3. The target box size is Φ8×212.13mm, the target box cladding thickness is 0.64mm, the target box upper and lower plugs are both 4.2mm high, of which the height to be plugged into the cladding tube is 2.2mm. The target box is loaded with 6 cobalt pellets and 6 zirconium alloy pellets (cobalt pellets and zirconium alloy pellets are arranged alternately), the size of the cobalt pellet is Φ3.11×8.37mm, the size of the zirconium alloy pellet is Φ3.11×25.11mm, and the density of the cobalt pellet is 8.80±0.05g / cm 3 .

[0049] The above production 60 The irradiation target of Co isotope was carried out in the CNP650 core of Qinshan Second Nuclear Power Plant. Eight groups of target assemblies were unloaded after irradiation for three cycles in the reactor. The average burnup of the target assemblies can reach 50515MWd / tU. 60 The average specific activity of Co can reach 66.4Ci / g. 60 The total output of Co is 1.08 million times.

[0050] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Irradiation production in a pressurized water reactor 60 Co target rod, characterized in that It includes an outer target rod cladding and a plurality of target boxes arranged in the target rod cladding. The target box comprises a target box shell and target core blocks arranged in the target box shell. The target core blocks comprise cobalt core blocks and zirconium alloy core blocks which are sequentially spaced apart along the axial direction of the target box shell.

2. Irradiation production in a pressurized water reactor according to claim 1 60 Co target rod, characterized in that The target box further comprises a pair of target box end plugs arranged in the target box shell, and the pair of target box end plugs are respectively located at the head and tail ends of the target core block.

3. Irradiation production in a pressurized water reactor according to claim 2 60 Co target rod, characterized in that The target core blocks are symmetrically distributed with the axial midpoint of the target box shell as the symmetry axis.

4. Irradiation production in a pressurized water reactor according to claim 1 60 Co target rod, characterized in that The density of the cobalt pellet is 8.80±0.05 g / cm 3 .

5. Irradiation production in a pressurized water reactor according to claim 1 60 Co target rod, characterized in that The target rod further comprises a pair of zirconium alloy positioning blocks symmetrically arranged in the target rod casing, and the pair of zirconium alloy positioning blocks are respectively located at the head and tail ends of the plurality of target boxes after placement.

6. Irradiation production in a pressurized water reactor according to claim 5 60 Co target rod, characterized in that The target rod further comprises a pair of target rod end plugs symmetrically arranged in the target rod casing, and the pair of target rod end plugs are respectively located at the head and tail ends of the target rod.

7. Irradiation production in a pressurized water reactor according to claim 5 60 Co target rod, characterized in that The target box and the zirconium alloy positioning block are symmetrically distributed with the axial midpoint of the target rod cladding as the symmetry axis.

8. Irradiation production in a pressurized water reactor according to claim 1 60 Co target rod, characterized in that The target rod cladding and the target box cladding are both filled with helium.

9. Irradiation production in a pressurized water reactor 60 A target for Co, comprising the target rod according to any one of claims 1 to 8, wherein a plurality of the target rods are distributed in a radially centrally symmetrical manner in a fuel assembly.

10. Irradiation production in a pressurized water reactor according to claim 9. 60 Co target, characterized in that An even number of target rods are provided, and the axial height of the target rods is consistent with the height of the active section of the fuel assembly.

Images