A truncated antimony-beryllium neutron source rod and reactor core for large power reactors

Abstract

The present invention discloses a truncated antimony-beryllium neutron source rod and a reactor core for a large-scale power reactor, comprising a neutron source rod cladding, a pressing tube and a neutron source core block. The neutron source core block is arranged inside the neutron source rod cladding; the top end of the neutron source core block is connected to one end of the neutron source rod cladding through the pressing tube, and the bottom end of the neutron source core block is connected to the other end of the neutron source rod cladding through the pressing tube; the pressing tube is used to limit the axial displacement of the neutron source core block along the neutron source rod cladding; the central height of the neutron source core block is consistent with the central height of the sensitive area of the out-of-reactor detector, and the relationship between the total length of the neutron source core block and the total length of the sensitive area of the out-of-reactor detector is: h2 - h1 ≤ 50 cm, where h2 is the total length of the neutron source core block and h1 is the total length of the sensitive area of the out-of-reactor detector. The present invention is applicable to the secondary neutron source assembly of a large-scale nuclear power reactor, can reduce the emission amount of the tritium source term in the nuclear reactor environment, and helps to extend the service life and reliability of the neutron source rod.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear reactor design, and particularly relates to a truncated antimony-beryllium neutron source rod and a reactor core for a large power reactor. Background Art

[0002] During the refueling and startup of a reactor, it is necessary to monitor the core fission reaction rate and its changes to prevent the reactor from reaching an uncontrollable prompt critical state. The current monitoring method is to arrange off-core nuclear instrumentation at a certain position outside the core, and monitor the neutrons from the core to the off-core nuclear instrumentation to monitor the core fission reaction rate and its changes.

[0003] For current large nuclear power reactors, in the first cycle, an off-core source range detector is used for monitoring. The detector is far from the core, and a primary neutron source assembly is introduced into the core. Its core is generally a californium source (Cf-252). Starting from the second cycle, a secondary neutron source assembly is used, and its core is an antimony-beryllium source (Sb-Be), which is used to increase the neutron fluence rate and counting rate at the detector. In the current design, the principle of neutron release by the Sb-Be source is as follows: Sb absorbs neutrons and is activated to produce Sb-124, which decays and releases γ rays. Since the energy of the γ rays released by Sb-124 is near the (γ, n) reaction resonance peak of Be, the reaction probability is high, and neutrons with higher intensity are generated. Moreover, the generated neutrons have low energy, are easy to produce fission reactions near the neutron source, but have weak penetration ability, and it is difficult for the fuel in the region far from the neutron source to undergo neutron fission reactions and it is not easy to directly penetrate to the off-core detector to generate signals. Since the generated neutrons are difficult to directly reach the off-core detector, compared with high-energy primary neutron sources, the fission neutron fraction of the antimony-beryllium source is more likely to reach a high proportion during startup. Therefore, the antimony-beryllium source can be arranged as close as possible to the core periphery to improve the detector response.

[0004] In order to increase the neutron source intensity of the Sb-Be alloy neutron source for the secondary neutron source, the Sb-Be core blocks arranged in traditional large nuclear power reactors are relatively long, with a total length generally about 250 - 300 cm, which is adapted to the total length of the fuel core blocks (generally about 360 - 400 cm). At the same time, in order to increase the neutron source intensity per unit length, the Sb-Be alloy contains only two elements, Sb and Be, and its material strength is low, and the component reliability is not high.

[0005] The Be in the Sb-Be alloy neutron source placed in the reactor reacts with neutrons to generate tritium and helium. Tritium can penetrate through the cladding of the neutron source rod and be released into the coolant, becoming an important source of tritium release in the reactor environment. Helium accumulates in the gas gap of the Sb-Be neutron source assembly, increasing the gas gap pressure, which may lead to gas gap overpressure. The amount of helium generated directly affects the service life of the Sb-Be neutron source. The amounts of tritium and helium generated are directly related to the loading of the Be core blocks.

[0006] However, the purpose of setting up the Sb-Be neutron source is to increase the neutron injection rate and counting rate at the detector. The sensitive area length of the source range detector arranged outside the pile is generally about 50 cm. For a neutron source rod with a total length of Sb-Be core block of about 250 cm, the key role is played by the neutrons released by the Sb-Be core blocks at roughly the same elevation as the sensitive area of ​​the source range detector. The neutrons released by the Sb-Be core blocks at other positions have little effect on the radiation level at the source range detector. Summary of the invention

[0007] The present invention aims to provide a truncated antimony-beryllium neutron source rod and a core for a large power reactor, and specifically to provide an antimony-beryllium (Sb-Be) core block with a shorter total length and less beryllium (Be) usage, which is suitable for a secondary neutron source assembly of a large nuclear power reactor. The present invention can reduce the emission of tritium sources in the nuclear reactor environment and help to extend the life and reliability of the neutron source rod.

[0008] The present invention is achieved through the following technical solutions:

[0009] In a first aspect, the present invention provides a truncated antimony beryllium neutron source rod for a large power reactor, the neutron source rod comprising a neutron source rod cladding, a compression tube and a neutron source core block, wherein the neutron source core block is arranged in the neutron source rod cladding; the top end of the neutron source core block is connected to one end of the neutron source rod cladding through the compression tube, and the bottom end of the neutron source core block is connected to the other end of the neutron source rod cladding through the compression tube; the compression tube is used to limit the axial displacement of the neutron source core block along the neutron source rod cladding;

[0010] The center height of the neutron source core block is consistent with the center height of the sensitive area of ​​the out-of-core detector, and the relationship between the total length of the neutron source core block and the total length of the sensitive area of ​​the out-of-core detector is: h2-h1≤50cm, h2 is the total length of the neutron source core block, and h1 is the total length of the sensitive area of ​​the out-of-core detector.

[0011] Neutron source pellets are used to provide additional neutrons for the ex-core detector response.

[0012] The truncated antimony beryllium neutron source rod designed by the present invention is designed such that the center of the neutron source core block in the rod is as close to the center height of the source range detector sensitive area as possible, and the total length of the neutron source core block is slightly less than the total length of the source range detector sensitive area plus 50 cm, which reduces the total length of the neutron source core block. In addition to being used for arranging the compression components (such as the compression tube), the reduced length can also leave a large amount of space to accommodate the gas generated by the irradiation of the neutron source core block and reduce the gas pressure growth rate. The present invention can reduce the tritium source emission of the nuclear reactor environment, reduce the amount of helium produced, and is conducive to extending the life of the neutron source rod.

[0013] Further, the neutron source rod further includes a gasket disposed between the neutron source pellet and the pressing tube for protecting the neutron source pellet to a certain extent.

[0014] Further, the neutron source pellet is an antimony-beryllium (Sb-Be) neutron source pellet.

[0015] Further, the neutron source pellet is a hollow neutron source pellet with a hole in the center.

[0016] Further, the material of the neutron source pellet is made of a ternary alloy containing antimony-beryllium (Sb-Be).

[0017] In the above technical solutions, on the premise of reducing the source strength requirement per unit volume, the layout of the secondary neutron source is optimized to further reduce the neutron source strength requirement; in order to adapt to the reduction of the neutron source strength requirement, further consideration is given to reducing the usage amount of beryllium (Be). One way is to make the antimony-beryllium (Sb-Be) alloy into a hollow form, and the other way is to use a metal block made of a ternary alloy such as Sb-Be-Fe to reduce the usage amount of Be, and the strength of the metal block can also be improved.

[0018] Further, the ternary alloy includes Fe-Sb-Be alloy or Ti-Sb-Be alloy.

[0019] Further, the neutron source pellet is manufactured by a low-cost method such as forging or casting from a ternary alloy material.

[0020] Further, the pressing tube is of a hollow structure, and holes are provided in the tube wall of the pressing tube.

[0021] In a second aspect, the present invention further provides a reactor core for a large power reactor. The reactor core includes the truncated antimony-beryllium neutron source rod for a large power reactor described above; the truncated antimony-beryllium neutron source rod for a large power reactor is arranged in the outermost fuel assembly of the reactor core to reduce the source strength requirement for the neutron source; a detector outside the reactor core is arranged outside the reactor core; the truncated antimony-beryllium neutron source rod for a large power reactor is used to provide additional neutrons for the response of the detector outside the reactor core.

[0022] Further, the cladding of the neutron source rod isolates the neutron source pellet from the coolant of the reactor core.

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

[0024] 1. A truncated antimony-beryllium neutron source rod for a large-scale power reactor according to the present invention, compared with the traditional neutron source rod used in a large-scale nuclear power reactor, under the same subcritical core state, the neutron fluence rate and counting rate of the out-of-core detector are roughly equivalent, but the total length of the neutron source core blocks used is significantly reduced, and the loading of antimony-beryllium (Sb-Be) is significantly reduced, which can reduce the emission of tritium source terms in the nuclear reactor environment, reduce the production of helium gas, reduce the production of helium gas in the neutron source core blocks (Sb-Be core blocks), is beneficial to extending the service life of the neutron source rod, improves the performance and reliability of the neutron source rod components by using a ternary alloy, and reduces the processing cost.

[0025] 2. A truncated antimony-beryllium neutron source rod for a large-scale power reactor according to the present invention, the neutron source rod uses a single-layer cladding, and no structure is provided after the core block is provided with a central hole. After setting, the source strength of the neutron source is appropriately reduced, and the weight of tritium production is appropriately reduced, but the volume inside the neutron source rod increases, which can accommodate more helium gas released during use, improve the helium gas capacity, and provide support for increasing the service life of the rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings:

[0027] Figure 1 It is a schematic structural diagram of a truncated antimony-beryllium neutron source rod for a large-scale power reactor according to Embodiment 1 of the present invention.

[0028] Figure 2 It is a schematic structural diagram of a truncated antimony-beryllium neutron source rod for a large-scale power reactor according to Embodiment 2 of the present invention.

[0029] Figure 3 It is a schematic structural diagram of a truncated antimony-beryllium neutron source rod for a large-scale power reactor according to Embodiment 3 of the present invention.

[0030] Figure 4 It is a schematic structural diagram of a core for a large-scale power reactor according to Embodiment 4 of the present invention.

[0031] Reference numerals and corresponding component names:

[0032] 1 - Neutron source rod cladding, 2 - Compression tube, 3 - Gasket, 4 - Neutron source core block, 5 - Out-of-core detector, 6 - Hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the embodiments and the drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and do not limit the present invention.

[0034] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known structures, circuits, materials, or methods have not been specifically described in order to avoid obscuring aspects of the present invention.

[0035] Throughout the specification, references to "one embodiment", "an embodiment", "an example", or "an example" mean that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present invention. Thus, the phrases "one embodiment", "an embodiment", "an example", or "an example" appearing throughout the specification are not necessarily all referring to the same embodiment or example. Additionally, the particular features, structures, or characteristics may be combined in any suitable combination and / or sub-combination in one or more embodiments or examples. Further, those of ordinary skill in the art will understand that the diagrams provided herein are for illustrative purposes only and are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] In the description of the present invention, the orientation or positional relationship indicated by terms such as "front", "rear", "left", "right", "upper", "lower", "vertical", "horizontal", "high", "low", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is 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 thus should not be construed as limiting the scope of protection of the present invention.

[0037] A truncated antimony-beryllium neutron source rod for a large power reactor according to the present invention has the center of the neutron source core block 4 in the rod as consistent as possible with the center height of the sensitive area of the source range detector. The total length of the neutron source core block 4 is slightly not longer than the length of the sensitive area of the source range detector plus 50 cm. This reduces the total length of the neutron source core block 4. The reduced length, in addition to being used for arranging the pressing assembly (such as the pressing tube 2), can also leave a large amount of space to accommodate the gas generated by the neutron source core block 4 being irradiated, reducing the gas pressure growth rate; optimizing the arrangement of the secondary neutron source to further reduce the neutron source intensity requirement; in order to adapt to the reduced neutron source intensity requirement, further reducing the loading of Be in the neutron source core block 4, using a hollow form of the neutron source core block 4, or using a metal block made of a ternary alloy (such as Sb-Be-Fe).

[0038] Compared with the traditional neutron source rods used in large nuclear power reactors, for the neutron source rod proposed by the present invention, under the same subcritical core state, the neutron fluence rate and counting rate of the out-of-core detectors are roughly equivalent. However, the total length of the neutron source core block 4 used is significantly reduced, and the Sb-Be loading is greatly decreased. This can reduce the tritium source term emissions in the nuclear reactor environment, reduce the helium production, facilitate the extension of the neutron source rod's lifespan, and improve the reliability of the neutron source rod components.

[0039] Example 1

[0040] As Figure 1 As shown, a truncated Sb-Be neutron source rod for a large power reactor according to the present invention includes a neutron source rod cladding 1, a compression tube 2, and a neutron source core block 4. The neutron source core block 4 is disposed inside the neutron source rod cladding 1; the top end of the neutron source core block 4 is connected to one end of the neutron source rod cladding 1 through the compression tube 2, and the bottom end of the neutron source core block 4 is connected to the other end of the neutron source rod cladding 1 through the compression tube 2; the compression tube 2 is used to limit the axial displacement of the neutron source core block 4 along the neutron source rod cladding 1.

[0041] The central height of the neutron source core block 4 is kept consistent with the central height of the sensitive area of the out-of-core detector 5, and the relationship between the total length of the neutron source core block 4 and the total length of the sensitive area of the out-of-core detector 5 is: h2 - h1 ≤ 50 cm, where h2 is the total length of the neutron source core block 4 and h1 is the total length of the sensitive area of the out-of-core detector 5.

[0042] The neutron source core block 4 is used to provide additional neutrons for the response of the out-of-core detector 5.

[0043] As a further implementation, the neutron source rod further includes a gasket 3, which is disposed between the neutron source core block 4 and the compression tube 2 and is used to provide a certain protection for the neutron source core block 4.

[0044] As a further implementation, the neutron source core block 4 is an Sb-Be neutron source core block.

[0045] As a further implementation, after shortening the length of the neutron source core block 4, the compression tube 2 on the upper part of the neutron source core block 4 is lengthened and is of a hollow structure, and holes are opened on the tube wall of the compression tube 2 to further reduce the material usage of the compression tube and increase the internal space volume of the secondary neutron source assembly.

[0046] After shortening the length of the neutron source core block 4, the secondary neutron source assembly (i.e., a truncated Sb-Be neutron source rod for a large power reactor) can be arranged in the outermost fuel assembly in the core, which can reduce the requirement for the neutron source strength.

[0047] After the implementation of the embodiments of the present invention, compared with the traditional neutron source rods used in large nuclear power reactors, under the same subcritical core state, the neutron fluence rate and counting rate of the out-of-core detectors are roughly equivalent. The total length of the antimony-beryllium (Sb-Be) neutron source pellets used is significantly reduced, the Sb-Be loading is greatly decreased, the production amount of tritium source term and helium is reduced, the helium accommodation capacity of the secondary neutron source is improved, the pressure increase is reduced, the helium production amount is decreased, which is beneficial to extending the service life of the neutron source rod. The reduction of the pressure increase can also reduce the partial pressure of tritium, thereby reducing the permeation amount of tritium through the cladding.

[0048] Example 2

[0049] As Figure 2 shown, the difference between this embodiment and Embodiment 1 is that the neutron source pellet 4 adopts a hollow neutron source pellet with a hole 6 opened in the center.

[0050] In this embodiment, the hollow neutron source pellet is an Sb-Be binary alloy, but the structure is a hollow structure with a central hole 6, reducing the Be loading.

[0051] The secondary neutron source rod of this embodiment (i.e., a truncated Sb-Be neutron source rod for large power reactors) is arranged in the outermost layer of fuel assemblies in the core. In the position in the assembly, it can not only ensure that the secondary neutron source can receive sufficient neutron irradiation, but also ensure that the source range detector can receive sufficient neutrons, and the fission neutron fraction in the counting meets the monitoring requirements, as Figure 4 shown.

[0052] After the implementation of the embodiments of the present invention, compared with the traditional neutron source rods used in large nuclear power reactors, under the same subcritical core state, the neutron fluence rate and counting rate of the out-of-core detectors are roughly equivalent. The total length of the antimony-beryllium (Sb-Be) neutron source pellets used is significantly reduced, the Sb-Be neutron source pellet is of a hollow structure, the Be loading is reduced, the production amount of tritium source term and helium is reduced, the helium accommodation capacity of the secondary neutron source is improved, the pressure increase is reduced, the helium production amount is decreased, which is beneficial to extending the service life of the neutron source rod. The reduction of the pressure increase can also reduce the partial pressure of tritium, thereby reducing the permeation amount of tritium through the cladding.

[0053] Example 3

[0054] As Figure 3 shown, the difference between this embodiment and Embodiment 1 is that the material of the neutron source pellet 4 is made of a ternary alloy containing antimony-beryllium (Sb-Be), and the structure is a solid cylinder, reducing the Be loading. Specifically, the ternary alloy includes Fe-Sb-Be alloy or Ti-Sb-Be alloy. The ternary alloy core pellet material containing antimony-beryllium (Sb-Be) no longer uses powder metallurgy to manufacture, but is manufactured by low-cost methods such as forging or casting.

[0055] The secondary neutron source assembly of this embodiment (i.e., a truncated antimony-beryllium neutron source rod for a large power reactor) is arranged in the outermost layer of fuel assemblies in the reactor core. Its position in the assembly can ensure that the secondary neutron source can receive sufficient neutron irradiation, and at the same time, ensure that the source range detector can receive enough neutrons, and the fission neutron fraction in the count meets the monitoring requirements, such as Figure 4 shown.

[0056] After the implementation of the embodiment of the present invention, compared with the traditional neutron source rod used in a large nuclear power reactor, under the same subcritical core state, the neutron fluence rate and count rate of the out-of-core detector are roughly the same. The total length of the antimony-beryllium (Sb-Be) neutron source core block used is greatly reduced. The antimony-beryllium (Sb-Be) neutron source core block material is a ternary alloy, the Be loading is reduced, the tritium source term generation and helium generation are reduced, the helium accommodation capacity of the secondary neutron source is improved, the pressure increase is reduced, and the helium generation is reduced, which is beneficial to extending the life of the neutron source rod. The reduction of the pressure increase can also reduce the partial pressure of tritium, thereby reducing the permeation amount of tritium through the cladding. The ternary alloy material has higher strength, increasing the reliability of the component; the ternary alloy material can be manufactured by low-cost methods such as forging or casting, reducing the manufacturing cost.

[0057] Example 4

[0058] As Figure 4 shown, the difference between this embodiment and Embodiment 1 is that this embodiment provides a reactor core for a large power reactor, which includes a truncated antimony-beryllium neutron source rod for a large power reactor described in Embodiment 1, Embodiment 2, and Embodiment 3; the truncated antimony-beryllium neutron source rod for a large power reactor is arranged in the outermost layer of fuel assemblies in the reactor core, reducing the required source strength of the neutron source; there is an out-of-core detector 5 arranged outside the reactor core; the truncated antimony-beryllium neutron source rod for a large power reactor is used to provide additional neutrons for the response of the out-of-core detector 5.

[0059] As a further implementation, the neutron source rod cladding 1 isolates the neutron source core block 4 from the coolant of the reactor core.

[0060] The truncated antimony-beryllium neutron source rod for a large power reactor described in this embodiment is arranged in the outermost layer of fuel assemblies in the reactor core. Its position in the assembly can ensure that the secondary neutron source can receive sufficient neutron irradiation, and at the same time, ensure that the source range detector can receive enough neutrons, and the fission neutron fraction in the count meets the monitoring requirements.

[0061] Figure 4 In

[0062] The specific embodiments described above further elaborate on the objective, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A truncated antimony-beryllium neutron source rod for a large power reactor, characterized in that, The neutron source rod includes a neutron source rod cladding (1), a pressing tube (2), and a neutron source pellet (4). The neutron source pellet (4) is disposed inside the neutron source rod cladding (1). The top end of the neutron source pellet (4) is connected to one end of the neutron source rod cladding (1) through the pressing tube (2), and the bottom end of the neutron source pellet (4) is connected to the other end of the neutron source rod cladding (1) through the pressing tube (2). The pressing tube (2) is used to limit the axial displacement of the neutron source pellet (4) along the neutron source rod cladding (1). The central height of the neutron source pellet (4) is consistent with the central height of the sensitive area of the out-of-core detector (5), and the relationship between the total length of the neutron source pellet (4) and the total length of the sensitive area of the out-of-core detector (5) is: h2 - h1 ≤ 50 cm, where h2 is the total length of the neutron source pellet (4) and h1 is the total length of the sensitive area of the out-of-core detector (5).

2. The truncated antimony-beryllium neutron source rod for a large power reactor according to claim 1, wherein The neutron source rod further includes a gasket (3). The gasket (3) is disposed between the neutron source pellet (4) and the pressing tube (2) and is used to protect the neutron source pellet (4).

3. A truncated antimony-beryllium neutron source rod for a large power reactor according to claim 1, characterized in that, The neutron source pellet (4) is an antimony-beryllium neutron source pellet.

4. A truncated antimony-beryllium neutron source rod for a large power reactor according to claim 3, characterized in that, The neutron source pellet (4) is a hollow-type neutron source pellet with a hole (6) opened in the center.

5. A truncated antimony-beryllium neutron source rod for a large power reactor according to claim 3, characterized in that, The material of the neutron source pellet (4) is made of a ternary alloy containing antimony and beryllium.

6. The truncated antimony-beryllium neutron source rod for large power reactors according to claim 5, characterized in that, The ternary alloy includes an Fe-Sb-Be alloy or a Ti-Sb-Be alloy.

7. A truncated antimony-beryllium neutron source rod for a large power reactor according to claim 6, characterized in that, The neutron source pellet (4) made of the ternary alloy is manufactured by forging or casting.

8. A truncated antimony-beryllium neutron source rod for a large power reactor according to claim 1, characterized in that, The pressing tube (2) is of a hollow-type structure, and holes are opened in the tube wall of the pressing tube (2).

9. A core for a large power reactor, characterized in that, The reactor core includes a truncated antimony-beryllium neutron source rod for a large power reactor as described in any one of claims 1 to 8. The truncated antimony-beryllium neutron source rod for a large power reactor is arranged in the outermost fuel assembly of the reactor core. An out-of-core detector (5) is arranged outside the reactor core. The neutron source pellet (4) of the truncated antimony-beryllium neutron source rod for a large power reactor is used to provide additional neutrons for the response of the out-of-core detector (5).

10. A core for a large power reactor according to claim 9, characterized in that, The neutron source rod cladding (1) isolates the neutron source pellet (4) from the coolant of the reactor core.

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