Nuclear reactor control rod and control rod assembly

Abstract

The present application relates to a kind of reactor control rod and control rod assembly.The reactor control rod includes sequentially connected upper absorption unit, middle absorption unit and lower absorption unit;The upper absorption unit includes upper cladding and upper absorber arranged in the upper cladding, the middle absorption unit includes middle cladding and middle absorber arranged in the middle cladding, and the lower absorption unit includes lower cladding and lower absorber arranged in lower cladding;The upper absorber is supported by the middle cladding, and the middle cladding is supported by the lower cladding.By setting middle cladding, the reactor control rod is divided into three units, the upper absorber is supported by the middle cladding, the middle cladding is supported by the lower cladding, the compressive stress suffered by the lower absorber is reduced, and the extrusion creep in axial direction is slowed down.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel technology, and more specifically, to a reactor control rod and a control rod assembly. Background Technology

[0002] Current pressurized water reactors mostly use control rods, which consist of a cladding, upper plug, lower plug, first elastic element, and absorber. During service, the control rods need to move up and down frequently within the fuel assembly guide tube, especially the lower part of the absorber. At this time, the absorber may swell significantly after being exposed to neutron irradiation; at the same time, the absorber undergoes axial compressive creep due to the compression of the first elastic element and its own weight. Under these two effects, the radial dimension of the absorber continuously increases.

[0003] Furthermore, current control rod absorbers mostly employ a one-piece solid cylindrical design. Excessive swelling and creep of the absorber can cause it to continuously push the control rod cladding outwards after contact with the absorber. When the cladding diameter reaches a certain level, it can affect the free movement of the control rod within the guide tube, potentially leading to exceeding the drop time limit or even preventing the control rod assembly from being fully inserted into the reactor core. Several rod jamming incidents caused by excessive control rod swelling have already occurred in the industry, posing a significant challenge to the safe operation of reactors.

[0004] To address the aforementioned issues, Chinese Patent Application No. CN200680026862.5 discloses a control rod for a pressurized water reactor. The control rod has an absorber rod disposed within a sleeve, and the absorber rod has at least one recess on at most a portion of its circumferential surface in at least one lower section, thereby creating a free space within the sleeve surrounding the absorber rod.

[0005] However, the recessed design does not reduce the pressure from the first elastic element on the lower absorber or the weight on the upper absorber, resulting in significant compressive creep. Furthermore, because the neutron flux is worse at the lower part of the absorber than at the upper part, its expansion and swelling are more severe. Therefore, this prior art, which involves creating a recess on the outside of the absorber, has limited effect in mitigating the increase in the radial dimension of the absorber. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an improved reactor control rod and control rod assembly, which addresses the shortcomings of the prior art.

[0007] The technical solution adopted by this invention to solve its technical problem is:

[0008] This application provides a reactor control rod, comprising an upper absorber unit, a middle absorber unit, and a lower absorber unit connected in sequence; characterized in that the upper absorber unit includes an upper cladding and an upper absorber disposed within the upper cladding, the middle absorber unit includes a middle cladding and a middle absorber disposed within the middle cladding, and the lower absorber unit includes a lower cladding and a lower absorber disposed within the lower cladding; the upper absorber is supported by the middle cladding, and the middle cladding is supported by the lower cladding.

[0009] In some embodiments, the outer wall surface of the lower absorber is provided with a plurality of straight ribs spaced apart in the circumferential direction.

[0010] In some embodiments, the lower absorber is hollow inside.

[0011] In some embodiments, the central shell is cylindrical in shape and includes a main body, an upper connecting part, and a lower connecting part. The upper connecting part and the lower connecting part are located at opposite ends of the central shell. The outer diameter of the upper connecting part and the lower connecting part is smaller than the outer diameter of the main body, and the inner diameter of the upper connecting part and the lower connecting part is equal to the inner diameter of the main body.

[0012] In some embodiments, the central absorber is axially disposed within the central shell, and there is a gap between the sidewall of the central absorber and the inner wall of the central shell.

[0013] In some embodiments, the upper casing is tubular, the upper absorber is axially disposed inside the upper casing, and there is a gap between the side wall of the upper absorber and the inner wall of the upper casing.

[0014] In some embodiments, the upper connecting portion is embedded in the lower end of the upper shell, the diameter of the upper absorbent is greater than the inner diameter of the upper connecting portion and smaller than the outer diameter of the upper connecting portion; the outer diameter of the upper shell is equal to the outer diameter of the body portion, and the inner diameter of the upper shell is equal to the outer diameter of the upper connecting portion.

[0015] In some embodiments, the lower casing is tubular, the lower absorber is axially disposed within the lower casing, and there is a gap between the outer wall of the lower absorber and the inner wall of the lower casing.

[0016] In some embodiments, the lower connecting portion is embedded within the lower casing, the diameter of the middle absorber is larger than the inner diameter of the lower absorber, the outer diameter of the body portion is equal to the outer diameter of the lower casing, and the outer diameter of the lower connecting portion is equal to the inner diameter of the lower casing.

[0017] In some embodiments, the reactor control rod further includes an upper plug, and the upper absorber unit further includes a first elastic element; the first elastic element is disposed in the upper cladding and connects the upper plug and the upper absorber, and the upper plug is installed on the upper end of the upper cladding.

[0018] In some embodiments, the reactor control rod further includes a lower end plug, and the lower absorber unit further includes a second elastic member; the second elastic member is disposed in the lower cladding and connects the lower end plug and the lower absorber, and the lower end plug is installed at the lower end of the lower cladding.

[0019] The present invention also provides a reactor control rod assembly, comprising a plurality of reactor control rods, wherein at least one of the plurality of reactor control rods employs the reactor control rod described above.

[0020] The reactor control rods and control rod assemblies of the present invention have the following beneficial effects:

[0021] By setting a central cladding, the reactor control rods are divided into three units. The central cladding supports the upper absorber, and the lower cladding supports the central cladding, which reduces the compressive stress on the lower absorber and slows down its axial extrusion creep. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0023] Figure 1 This is a plan view of the reactor control rods in a preferred embodiment of the present invention;

[0024] Figure 2 yes Figure 1 A schematic cross-sectional view of the reactor control rods along the AA direction is shown.

[0025] Figure 3 yes Figure 2 A detailed view of node B of the reactor control rod shown.

[0026] Figure 4 yes Figure 2 A schematic diagram of the structure of the central cladding 21 of the reactor control rods shown;

[0027] Figure 5 yes Figure 4 A plan view of the central cladding 21 of the reactor control rods shown;

[0028] Figure 6 yes Figure 5 A schematic cross-sectional view along the AA direction of the middle cladding 21 of the reactor control rods shown.

[0029] Figure 7 yes Figure 2 A schematic diagram of the structure of the lower absorber 32 of the reactor control rod shown;

[0030] Figure 8 yes Figure 7 A schematic plan view of the lower absorber 32 of the reactor control rod shown;

[0031] Figure 9 yes Figure 8 A schematic cross-sectional view along line AA of the lower absorber 32 of the reactor control rod shown.

[0032] in, Figures 1 to 9 The correspondence between the reference numerals and component names in the attached drawings is as follows: upper absorption unit 1, middle absorption unit 2, lower absorption unit 3, upper end plug 4, lower end plug 5, upper shell 11, upper absorber 12, first elastic element 13, middle shell 21, middle absorber 22, upper connecting part 211, body part 212, lower connecting part 213, lower shell 31, lower absorber 32, and second elastic element 33. Detailed Implementation

[0033] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0034] In the following description, it should be understood that the orientations or positional relationships indicated by terms such as "front," "rear," "up," "down," "left," "right," "longitudinal," "horizontal," "vertical," "horizontal," "top," "bottom," "inner," "outer," "head," and "tail" are based on the orientations or positional relationships shown in the accompanying drawings, and are constructed and operated in a specific orientation. They are only for the convenience of describing this technical solution and do not indicate that the device or component referred to must have a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0035] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. When an component is referred to as being "on" or "below" another component, the component can be located "directly" or "indirectly" on the other component, or there may be one or more intermediary components. The terms "first," "second," "third," etc., are only for the convenience of describing this technical solution and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0036] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0037] Figure 1 The diagram illustrates reactor control rods in some embodiments of the present invention. These control rods can be used to regulate reactor power and control coolant temperature fluctuations, rapidly introduce negative reactivity under accident conditions, and enable emergency reactor shutdown to ensure nuclear safety. The reactor control rod may include an upper absorber unit 1, a middle absorber unit 2, a lower absorber unit 3, an upper plug 4, and a lower plug 5. The upper absorber unit 1, middle absorber unit 2, and lower absorber unit 3 are connected sequentially to absorb neutrons from the reactor. The upper plug 4 is installed at the upper end of the upper absorber unit 1, and the lower plug 5 is installed at the lower end of the lower absorber unit 3, together sealing the internal space of the reactor control rod.

[0038] like Figure 2As shown, in some embodiments, the upper absorption unit 1 may include an upper casing 11, an upper absorber 12, and a first elastic element 13. The upper casing 11 may be tubular, with its upper end connected to the upper plug 4 and its lower end connected to the middle absorption unit 2, serving to protect its internal space and the components disposed therein. The upper absorber 12 may be columnar, axially disposed within the upper casing 11, with its lower end abutting against the middle absorption unit 2, serving to absorb neutrons from the reactor. A gap exists between the sidewall of the upper absorber 12 and the inner sidewall of the upper casing, providing permissible space for the radial expansion of the upper absorber 12. The first elastic element 13 may be a gas spring, with one end connected to the upper plug 4 and the other end connected to the upper end of the upper absorber 12, providing reserved space for the axial expansion of the upper absorber 12. In some embodiments, the upper casing 11 and the upper absorber 12 are coaxially disposed.

[0039] Combination Figure 3 As shown, in some embodiments, the central absorber unit 2 may include a central cladding 21 and a central absorber 22. The central cladding 21 supports the upper cladding 11 and the upper absorber 12, and protects its internal space. The central cladding 21 and the upper cladding 11 may be welded together. The central absorber 22 may be columnar and is used to absorb neutrons from the reactor. It is axially disposed within the central cladding 21, and there is a gap between the sidewall of the central absorber 22 and the inner sidewall of the central cladding 21, which provides permissible space for the radial expansion of the central absorber 22. In some embodiments, the central cladding 21 and the central absorber 22 are coaxially arranged.

[0040] See also Figures 4 to 6 In some embodiments, the middle shell 21 may be cylindrical and may include an upper connecting portion 211, a body portion 212, and a lower connecting portion 213 connected in sequence. The upper connecting portion 211 is used to connect with the upper shell 11 and support the upper absorbent body 12. Specifically, the upper connecting portion 211 is embedded in the upper shell 11, located at the upper end of the body portion 212, and its outer diameter is smaller than the outer diameter of the body portion 212 and equal to the inner diameter of the upper shell 11. The inner diameter of the upper connecting portion 211 is equal to the inner diameter of the body portion 212 and smaller than the diameter of the upper absorbent body 12, so that the lower end of the upper absorbent body 12 can be supported by the middle shell 21. The body portion 212 is used to support the upper shell 11, and the outer diameter of the body portion 212 is equal to the outer diameter of the upper shell 11. The lower connecting portion 213 is used to be embedded in the lower absorption unit 3. It is located at the lower end of the body portion 212, and the outer diameter of the lower connecting portion 213 is smaller than the outer diameter of the body portion 212. In some embodiments, the upper connecting portion 211, the body portion 212, and the lower connecting portion 213 are coaxially arranged.

[0041] In some embodiments, the lower absorber unit 3 may include a lower cladding 31, a lower absorber 32, and a second elastic member 33. The lower cladding 31 may be tubular, protecting the lower absorber 32 inside and providing support for the middle cladding 21. The lower cladding 31 and the middle cladding 21 may be connected together by welding. The outer diameter of the lower cladding 31 is equal to the outer diameter of the middle cladding 21, and the inner diameter of the lower cladding 31 is adapted to the outer diameter of the lower connecting portion 213. The lower absorber 32 is used to absorb neutrons from the reactor and is axially disposed within the lower cladding 31. There is a gap between the outer wall of the lower absorber 32 and the inner wall of the lower cladding 31, which provides permissible space for the radial expansion of the lower absorber 32. The upper end of the lower absorber 32 abuts against the lower end of the middle absorber 22. The second elastic element 33 can be a gas cavity spring, which is disposed inside the lower casing 31 and connects the lower absorber 32 to the lower end plug 5. It provides a space for the deposited layers that fall off the absorber, so that these deposited layers do not accumulate at the lower end of the absorber, thereby further improving the anti-swelling performance of the reactor control rod.

[0042] See also Figures 7 to 9 In some embodiments, the lower absorber 32 may be cylindrical and hollow internally. Specifically, the lower absorber 32 has a central through-hole extending from the upper end face to the lower end face, and is cylindrical in shape. This reduces the radial outward swelling of the lower absorber 32, lowers its temperature, and reduces axial compression creep and swelling. In some embodiments, the inner diameter of the lower absorber 32 is smaller than the diameter of the middle absorber 22 so that the lower absorber 32 can provide support for the middle absorber 22. Multiple straight ribs may be circumferentially spaced on the outer wall of the lower absorber 32, providing permissible space for radial swelling. In some embodiments, the lower shell 31 and the lower absorber 32 are coaxially arranged.

[0043] For example Figure 1 and Figure 2 As shown, in some embodiments, the upper plug 4 can be welded to the upper end of the upper shell 11, and in some embodiments, the lower plug 5 can be welded to the lower end of the lower shell 31. The shapes and sizes of the upper plug 4 and the lower plug 5 are adapted to the upper shell 11 and the lower shell 31, respectively.

[0044] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They do not limit the scope of protection of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A reactor control rod, comprising an upper absorber unit (1), a middle absorber unit (2), and a lower absorber unit (3) connected in sequence; characterized in that, The upper absorption unit (1) includes an upper shell (11) and an upper absorber (12) disposed within the upper shell (11); the middle absorption unit (2) includes a middle shell (21) and a middle absorber (22) disposed within the middle shell (21); the lower absorption unit (3) includes a lower shell (31) and a lower absorber (32) disposed within the lower shell (31); the upper absorber (12) is supported by the middle shell (21), and the middle shell (21) is supported by the lower shell (31); It also includes an upper plug (4), and the upper absorption unit (1) further includes a first elastic element (13); the first elastic element (13) is disposed in the upper shell (11) and connects the upper plug (4) and the upper absorber (12), and the upper plug (4) is installed on the upper end of the upper shell (11); It also includes a lower end plug (5), and the lower absorption unit (3) further includes a second elastic element (33); the second elastic element (33) is disposed in the lower shell (31) and connects the lower end plug (5) and the lower absorption body (32), and the lower end plug (5) is installed at the lower end of the lower shell (31).

2. The reactor control rod according to claim 1, characterized in that, The outer wall of the lower absorber (32) is provided with a plurality of straight ribs spaced apart in the circumferential direction.

3. The reactor control rod according to claim 1, characterized in that, The lower absorber (32) is hollow inside.

4. The reactor control rod according to claim 1, characterized in that, The central shell (21) is cylindrical in shape and includes a main body (212), an upper connecting part (211), and a lower connecting part (213). The upper connecting part (211) and the lower connecting part (213) are located at both ends of the central shell (21). The outer diameter of the upper connecting part (211) and the lower connecting part (213) is smaller than the outer diameter of the main body (212), and the inner diameter of the upper connecting part (211) and the lower connecting part (213) is equal to the inner diameter of the main body (212).

5. The reactor control rod according to claim 1, characterized in that, The central absorber (22) is axially disposed inside the central shell (21), and there is a gap between the side wall of the central absorber (22) and the inner wall of the central shell (21).

6. The reactor control rod according to claim 1, characterized in that, The upper shell (11) is tubular, and the upper absorber (12) is axially disposed inside the upper shell (11). There is a gap between the side wall of the upper absorber (12) and the inner wall of the upper shell (11).

7. The reactor control rod according to claim 4, characterized in that, The upper connecting part (211) is embedded in the lower end of the upper shell (11). The diameter of the upper absorber (12) is greater than the inner diameter of the upper connecting part (211) and smaller than the outer diameter of the upper connecting part (211). The outer diameter of the upper shell (11) is equal to the outer diameter of the body part (212), and the inner diameter of the upper shell (11) is equal to the outer diameter of the upper connecting part (211).

8. The reactor control rod according to claim 1, characterized in that, The lower shell (31) is tubular, and the lower absorber (32) is axially disposed inside the lower shell (31). There is a gap between the outer wall of the lower absorber (32) and the inner wall of the lower shell (31).

9. The reactor control rod according to claim 4, characterized in that, The lower connecting part (213) is embedded in the lower shell (31), the diameter of the middle absorber (22) is larger than the inner diameter of the lower absorber (32), the outer diameter of the body part (212) is equal to the outer diameter of the lower shell (31), and the outer diameter of the lower connecting part (213) is equal to the inner diameter of the lower shell (31).

10. A reactor control rod assembly comprising a plurality of reactor control rods, characterized in that, At least one of the plurality of reactor control rods is a reactor control rod as described in any one of claims 1 to 9.

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