Rod falling buffering device and method for control rod assembly

Abstract

The invention provides a rod falling buffering device and method for a control rod assembly, the device comprises a driving rod and a guide cylinder, and the driving rod and the control rod assembly connected with the bottom are used for being inserted into an inner cavity of the guide cylinder and a fuel assembly for emergency shutdown; the guide cylinder is provided with a buffer section, the buffer section is provided with a first matching cavity and a second matching cavity in the axial direction, and the cross section size of the first matching cavity in the axial direction of the buffer section is larger than that of the second matching cavity in the axial direction of the buffer section; the driving rod is sequentially provided with a first matching section and a second matching section in the axial direction of the driving rod, the first matching section is matched with the first matching cavity, the second matching section is matched with the second matching cavity, and the size of the cross section of the first matching section in the axial direction of the driving rod is larger than that of the cross section of the second matching section in the axial direction of the driving rod; wherein when a shutdown instruction is received and the first matching section reaches the top of the first matching cavity and continues to move downwards, the first matching section extrudes the water body in the first matching cavity so as to provide upward buffering force for the first matching section.

Description

Technical Field

[0001] The present invention relates to the technical field of reactor shutdown control, and in particular to a control rod assembly drop buffer device and method. Background Art

[0002] The control rod assembly acts as a neutron absorber. During an emergency shutdown of the reactor, the rods are quickly dropped into the core to achieve a safe shutdown of the reactor.

[0003] In actual rod drop, the final stage of rapid rod drop is very fast, which can easily generate significant impact loads on the fuel assembly. To prevent damage to the fuel assembly, a buffer section with a small gap is usually installed at the bottom of the guide tube where the control rod assembly and fuel assembly meet to achieve hydraulic cushioning.

[0004] However, for small pressurized water reactors, the core height is relatively small, which limits the height of the buffer section and makes it impossible to achieve the buffering effect required by the design.

[0005] Based on this, the inventors of the present application propose a control rod assembly drop buffer device and method, in order to solve one or more of the above-mentioned technical problems. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defect in the prior art that the buffer section of a small pressurized water reactor is limited in height and cannot achieve the buffer effect required by the design requirements, and to provide a control rod assembly drop buffer device and method.

[0007] The present invention solves the above technical problems through the following technical solutions:

[0008] A first aspect of the present invention provides a control rod assembly drop buffer device for a small pressurized water reactor, characterized in that the device includes a drive rod and a guide cylinder, wherein the drive rod and the control rod assembly connected to the bottom are used to insert the fuel assembly along the inner cavity of the guide cylinder to perform an emergency shutdown;

[0009] The guide cylinder has a buffer section, and the buffer section has a first matching cavity and a second matching cavity along its axial direction. The cross-sectional dimension of the first matching cavity along the axial direction of the buffer section is larger than the cross-sectional dimension of the second matching cavity along the axial direction of the buffer section.

[0010] The drive rod is provided with a first matching section and a second matching section in sequence along its axial direction, the first matching section is adapted to the first matching cavity, the second matching section is adapted to the second matching cavity, and the cross-sectional dimension of the first matching section along the axial direction of the drive rod is larger than the cross-sectional dimension of the second matching section along the axial direction of the drive rod; wherein,

[0011] When the shutdown command is received and the first mating section reaches the top of the first mating cavity and continues to descend, the first mating section squeezes the water in the first mating cavity to provide an upward buffering force for the first mating section.

[0012] According to one embodiment of the present invention, the length of the second fitting section along the axial direction of the guide cylinder is at least greater than the length of the first fitting cavity along the axial direction of the guide cylinder;

[0013] When the second mating section is mated with the second mating cavity, an action chamber is formed between the top of the second mating section and the first mating section and the guide cylinder, and the squeezed water acts upward on the bottom of the first mating section in the action chamber.

[0014] According to one embodiment of the present invention, the driving rod includes a main body section, the first mating section and the second mating section, and the first mating section and the second mating section are coaxially arranged with the main body section;

[0015] The cross-sectional dimensions of the first mating segment and the second mating segment along the axial direction of the main body segment are greater than the cross-sectional dimension of the main body segment along the axial direction thereof.

[0016] According to one embodiment of the present invention, the main body section is integrally provided with the first mating section and the second mating section.

[0017] According to one embodiment of the present invention, the first mating segment is connected to one end of the second mating segment via a first boss, and the cross-sectional dimension of the first boss decreases along the direction from the first mating segment to the second mating segment;

[0018] A second boss is provided at one end of the second mating segment facing away from the first mating segment, and the cross-sectional dimension of the second boss decreases gradually along the direction facing away from the second mating segment.

[0019] According to one embodiment of the present invention, the first boss has a first annular inclined surface, and the circumferential dimension of the first boss near one end of the first mating section corresponds to the circumferential dimension of the first mating cavity;

[0020] The second boss has a second annular inclined surface, and the circumferential dimension of the second boss close to the second fitting section corresponds to the circumferential dimension of the second fitting cavity.

[0021] According to one embodiment of the present invention, a first buffer groove is provided at one end of the first matching cavity away from the second matching cavity, and the cross-sectional dimension of the first buffer groove increases gradually in a direction away from the second matching cavity;

[0022] The first matching cavity and the second matching cavity are connected via a second buffer groove, and the cross-sectional dimension of the second buffer groove increases gradually in a direction away from the second matching cavity.

[0023] According to one embodiment of the present invention, the driving rod and the guide cylinder cooperate to form at least one level of rod drop buffer;

[0024] Each level of the rod drop buffer includes a group of the first matching segment and the first matching cavity, and a group of the second matching segment and the second matching cavity.

[0025] A second aspect of the present invention further provides a rod drop buffering method, using the control rod assembly rod drop buffering device as described above, the buffering method comprising:

[0026] Receive shutdown signal;

[0027] The control drive rod and the control rod assembly connected to its bottom end are controlled to slide axially along the guide cylinder; wherein, the drive rod undergoes at least one level of buffering during the axial sliding along the guide cylinder, so that the drive rod is decelerated to a target rod drop speed.

[0028] The positive progress effect of the present invention is:

[0029] The rod drop buffer device of the control rod assembly of the present invention is provided with a first matching cavity and a second matching cavity in the buffer section of the guide cylinder and a corresponding first matching section and a second matching section on the drive rod. Therefore, after receiving the emergency shutdown command, when the first matching section reaches the top of the first matching cavity and continues to descend, the bottom of the first matching section squeezes the water in the first matching cavity, and the squeezed water reacts to the bottom of the first matching section, thereby providing an upward thrust for the first matching section, thereby slowing down the falling speed of the drive rod, meeting the rod drop buffer demand of the small pressurized water reactor whose buffer section is short and cannot meet the control requirements, and effectively solving the rod drop buffer problem of the control rod assembly of the small pressurized water reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and other features, properties and advantages of the present invention will become more apparent through the following description in conjunction with the accompanying drawings and embodiments, in which:

[0031] Figure 1 This is a schematic structural diagram of a control rod assembly drop buffer device according to the present invention;

[0032] Figure 2 for Figure 1 Schematic diagram of the structure of the middle drive rod;

[0033] Figure 3 for Figure 1 Schematic diagram of the structure of the middle guide cylinder;

[0034] Figure 4 Schematic diagram of the cooperation between the driving rod and the guide cylinder at the first position of the rod drop;

[0035] Figure 5 Schematic diagram of the cooperation between the driving rod and the guide cylinder at the second position of the rod drop;

[0036] Figure 6 This is a schematic diagram of the driving rod of the present invention being fitted in the guide cylinder at the third position of the rod drop.

[0037] 1. Driving rod; 11. First mating section; 12. Second mating section; 13. Main section; 14. First boss; 141. First annular slope; 15. Second boss; 151. Second annular slope;

[0038] 2. Guide cylinder; 21. Buffer section; 22. First matching cavity; 23. Second matching cavity; 24. First buffer groove; 25. Second buffer groove; 26. Action chamber. DETAILED DESCRIPTION

[0039] The present invention is further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description herein. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0041] Please refer to Figures 1 to 6 The present invention proposes a control rod assembly drop buffer device for a small pressurized water reactor. The buffer device specifically includes a drive rod 1 and a guide tube 2. The drive rod 1 and the control rod assembly connected to the bottom are used to insert the fuel assembly along the inner cavity of the guide tube 2 to shut down the reactor in an emergency.

[0042] Specifically, in each stage of rod drop buffering, the guide cylinder 2 has a buffer section 21, and the buffer section 21 has a first matching cavity 22 and a second matching cavity 23 along its axial direction. The cross-sectional dimension of the first matching cavity 22 along the axial direction of the buffer section 21 is larger than the cross-sectional dimension of the second matching cavity 23 along the axial direction of the buffer section 21.

[0043] The insertion end of the drive rod 1 is provided with a first mating section 11 and a second mating section 12 in sequence along its axial direction. The first mating section 11 is adapted to the first mating cavity 22, and the second mating section 12 is adapted to the second mating cavity 23. The cross-sectional dimension of the first mating section 11 along the axial direction of the drive rod 1 is greater than the cross-sectional dimension of the second mating section 12 along the axial direction of the drive rod 1.

[0044] When an emergency shutdown command is received and the first mating section 11 reaches the top of the first mating cavity 22 and continues to descend, the first mating section 11 squeezes the water in the first mating cavity 22 to provide an upward buffering force for the first mating section 11 .

[0045] It can be seen that the small pressurized water reactor is a compact design of the pressurized water reactor. The core height of the small pressurized water reactor is smaller than that of the normal pressurized water reactor. When the rod is dropped to stop the reactor, the height of the hydraulic buffer section 21 at the bottom of the fuel assembly guide tube is limited, and it is difficult to achieve the buffering effect required by the design. A large impact load is easily generated between the control rod assembly and the fuel assembly.

[0046] Based on this, the present invention makes structural improvements to the drive rod 1 and the guide cylinder 2, thereby forming at least one level of rod drop buffer during the cooperation process of the drive rod 1 and the guide cylinder 2, thereby slowing down the fall of the drive rod 1, overcoming the influence of the traditional buffer structure being restricted by the core height, and effectively solving the problem of poor rod drop buffer effect of the small pressurized water reactor control rod assembly.

[0047] Please refer to Figures 1 to 3 The length of the second mating segment 12 along the axial direction of the guide cylinder 2 is at least greater than the length of the first mating cavity 22 along the axial direction of the guide cylinder 2. When the second mating segment 12 is mated with the second mating cavity 23, an active chamber 26 is formed between the top of the second mating segment 12, the first mating segment 11, and the guide cylinder 2. The squeezed water in the active chamber 26 acts upward on the bottom of the first mating segment 11.

[0048] That is, as the drive rod 1 falls, when the second mating section 12 reaches the upper end of the second mating cavity 23, the lower end of the first mating section 11 also reaches near the top of the first mating cavity 22. However, because the axial length of the second mating section 12 along the guide cylinder 2 is at least greater than the axial length of the first mating cavity 22 along the guide cylinder 2, the first mating section 11 does not engage with the first mating cavity 22 at this time. As the second mating section 12 continues to descend, the first mating section 11 gradually engages with the first mating cavity 22 and compresses the water at the bottom of the first mating cavity 22. The compressed water then pushes upward against the bottom of the first mating section 11, thereby reducing the falling speed of the drive rod 1 and meeting the rod drop buffering requirements of the small pressurized water reactor control rod assembly.

[0049] Moreover, the circumferential dimension of the first matching segment 11 is larger than the circumferential dimension of the second matching cavity 23 , so the top of the second matching cavity 23 will lock the first matching segment 11 to prevent the driving rod 1 from excessively descending.

[0050] Please continue to refer to Figure 1 The driving rod 1 includes a main body section 13, a first mating section 11 and a second mating section 12. The first mating section 11 and the second mating section 12 are coaxially arranged with the main body section 13; the cross-sectional dimensions of the first mating section 11 and the second mating section 12 along the axial direction of the main body section 13 are larger than the cross-sectional dimensions of the main body section 13 along its axial direction.

[0051] That is, the first mating segment 11 and the second mating segment 12 are disposed on the main body segment 13, and the radial dimensions of the first mating segment 11, the second mating segment 12, and the main body segment 13 decrease in sequence. Therefore, in the event of an emergency shutdown, after the first mating segment 11 reaches the first mating cavity 22, it compresses the bottom space of the first mating cavity 22, squeezing the water. The squeezed water acts upward on the first mating segment 11, cushioning its descent. This reduces the descent speed of the drive rod 1 and satisfies the rod drop cushioning requirements of the small pressurized water reactor control rod assembly.

[0052] In one embodiment, the main body segment 13 is integrally provided with the first mating segment 11 and the second mating segment 12 .

[0053] That is, the integrated processing of the driving rod 1 can improve the manufacturing accuracy, simplify the production process, and further improve the reliability of the driving rod 1 .

[0054] In some other embodiments, the first mating segment 11 and the second mating segment 12 may also be sleeved, that is, the first mating end and the second mating segment 12 are sleeved onto the target position of the main segment 13 and then welded or threaded together. The specific connection method between the main segment 13 and the first mating segment 11 and the second mating segment 12 is not limited herein.

[0055] Optionally, the first mating segment 11 is connected to one end of the second mating segment 12 through a first boss 14, and the cross-sectional dimension of the first boss 14 decreases along the direction from the first mating segment 11 to the second mating segment 12; the second mating segment 12 is provided with a second boss 15 at one end away from the first mating segment 11, and the cross-sectional dimension of the second boss 15 decreases along the direction away from the second mating segment 12.

[0056] It can be seen that the cross-sectional dimensions of the first mating cavity 22 and the second mating cavity 23 along the axial direction of the guide cylinder 2 are circular, and correspondingly, the cross-sectional dimensions of the first mating segment 11 and the second mating segment 12 along the axial direction of the drive rod 1 are also circular.

[0057] The first boss 14 is provided to smoothly connect the first mating section 11 and the second mating section 12 , and the second boss 15 serves as a guide for the second mating section 12 and the second mating cavity 23 to prevent the driving rod 1 from abutting against the inner wall of the guide cylinder 2 .

[0058] Specifically, the first boss 14 has a first annular bevel 141, and the circumferential dimension of the first boss 14 near one end of the first mating segment 11 corresponds to the circumferential dimension of the first mating cavity 22; the second boss 15 has a second annular bevel 151, and the circumferential dimension of the second boss 15 near the second mating segment 12 corresponds to the circumferential dimension of the second mating cavity 23.

[0059] In this arrangement, when the second mating segment 12 is mated with the second mating cavity 23, the water is relatively blocked downward (not completely blocked). As the first mating segment 11 reaches the top of the first mating cavity 22 and continues to descend, the first mating segment 11 also relatively blocks the first mating cavity 22 (not completely blocked). As the first mating segment 11 descends, it compresses the area between the bottom of the first mating segment 11 and the top of the second mating segment 12. The compressed water forms an upward reaction force and acts on the bottom of the first mating segment 11, thereby reducing the falling speed of the drive rod 1.

[0060] Furthermore, a first buffer groove 24 is provided at one end of the first mating cavity 22 away from the second mating cavity 23, and the cross-sectional size of the first buffer groove 24 increases in the direction away from the second mating cavity 23; the first mating cavity 22 and the second mating cavity 23 are connected by a second buffer groove 25, and the cross-sectional size of the second buffer groove 25 increases in the direction away from the second mating cavity 23.

[0061] Because the drive rod 1 is relatively long, to prevent the drive rod 1 from bending during its downward movement and abutting against the inner wall of the guide cylinder 2, thereby causing it to become stuck, the first buffer groove 24 is used to guide the first boss 14, thereby facilitating the axial movement of the first mating section 11 along the first mating cavity 22. Similarly, the second buffer groove 25 is used to guide the second boss 15, thereby facilitating the axial movement of the second mating section 12 along the second mating cavity 23.

[0062] In one embodiment, the driving rod 1 and the guide cylinder 2 cooperate to form at least one level of rod drop buffer, and each level of rod drop buffer includes a group of first matching segments 11 and first matching cavities 22 and a combination of second matching segments 12 and second matching cavities 23.

[0063] In some other embodiments, the driving rod 1 and the guide cylinder 2 may cooperate to form at least two levels of rod-dropping buffers, and adjacent levels of rod-dropping buffers may be provided continuously or at intervals, which is not limited here.

[0064] That is, a single-stage, two-stage or multi-stage rod drop buffer can be set according to actual needs to ensure that the drive rod 1 meets the rod drop terminal velocity requirement, overcoming the influence of the traditional buffer structure being restricted by the core height, and effectively solving the rod drop buffer problem of the control rod assembly of a small pressurized water reactor.

[0065] The rod drop process is described as follows:

[0066] Please refer to Figure 4 , Figure 4 The diagram shows the cooperation between the driving rod 1 and the guide cylinder 2 at the first falling position. At this time, the bottom end of the second cooperation section 12 has not yet reached the top of the first cooperation cavity 22.

[0067] As the driving rod 1 continues to fall, the driving rod 1 reaches Figure 5 At the second position shown, the bottom end of the second matching section 12 has reached the top of the second matching cavity 23. At this time, the second matching section 12, the first matching cavity 22 and the first matching section 11 form an active chamber 26. As the second matching section 12 continues to move downward, the first matching section 11 squeezes the water in the active chamber 26, and the squeezed water flows upward (as shown in FIG. Figure 5 The first engaging section 11 is provided with a first projection 14 and a second engaging section 12. The first engaging section 11 is provided with a first projection 14 and a second engaging section 12 is provided with a first projection 14 and a second engaging section 12.

[0068] Figure 6 The driving rod 1 is shown in the extreme position, but in actual use, the driving rod 1 is generally not allowed to reach such an extreme position. Figure 6 Instead of the position shown in the figure, multi-level buffering is used to ensure that the bottom of the first matching section 11 does not reach the top of the second matching cavity 23, thereby avoiding a rigid impact between the driving rod 1 and the driving rod 1 when it falls rapidly.

[0069] The present invention further provides a rod drop buffering method, which is implemented using the control rod assembly rod drop buffering device as described above. The buffering method includes:

[0070] Obtaining shutdown signal;

[0071] The control driving rod and the control rod assembly connected to its bottom end are controlled to slide axially along the guide cylinder; wherein, the driving rod passes through at least one level of buffering during the axial sliding along the guide cylinder to slow down the falling speed of the control rod assembly.

[0072] That is, when the command to stop the stack and drop the rods is received, the drive rod and the control rod assembly connected to its lower end fall freely under the action of gravity. When the rod drops to the final stage, it enters the buffer section and, through one or more stages of buffering, squeezes the water in the area, thereby forming an upward reaction force on the first matching section, causing the drive rod to slow down and finally reach the required rod drop speed.

[0073] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "install", "connect", "connect", "fix" and so on should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can also be a mechanical connection. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0074] This application uses specific terms to describe the embodiments of this application. For example, "one embodiment," "an embodiment," and / or "some embodiments" refer to a certain feature, structure, or characteristic associated with at least one embodiment of this application. Therefore, it should be emphasized and noted that "one embodiment," "an embodiment," or "an alternative embodiment" mentioned twice or multiple times in different locations in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application may be appropriately combined.

[0075] Although the present invention is disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modifications, equivalent variations, and modifications made to the above embodiments in accordance with the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A control rod assembly drop buffer device for a small pressurized water reactor, characterized in that: The device comprises a drive rod and a guide cylinder, wherein the drive rod together with a control rod assembly connected to the bottom is used to insert the fuel assembly along the inner cavity of the guide cylinder to perform an emergency shutdown; The guide cylinder has a buffer section, and the buffer section has a first matching cavity and a second matching cavity along its axial direction. The cross-sectional dimension of the first matching cavity along the axial direction of the buffer section is larger than the cross-sectional dimension of the second matching cavity along the axial direction of the buffer section. The drive rod is provided with a first matching section and a second matching section in sequence along its axial direction, the first matching section is adapted to the first matching cavity, the second matching section is adapted to the second matching cavity, and the cross-sectional dimension of the first matching section along the axial direction of the drive rod is larger than the cross-sectional dimension of the second matching section along the axial direction of the drive rod; wherein, When the shutdown command is received and the first mating section reaches the top of the first mating cavity and continues to descend, the first mating section squeezes the water in the first mating cavity to provide an upward buffering force for the first mating section.

2. The control rod assembly drop buffer device according to claim 1, characterized in that: The length of the second fitting section along the axial direction of the guide cylinder is at least greater than the length of the first fitting cavity along the axial direction of the guide cylinder; When the second mating section is mated with the second mating cavity, an action chamber is formed between the top of the second mating section and the first mating section and the guide cylinder, and the squeezed water acts upward on the bottom of the first mating section in the action chamber.

3. The control rod assembly drop buffer device according to claim 1, characterized in that: The driving rod includes a main body section, the first mating section and the second mating section, and the first mating section and the second mating section are coaxially arranged with the main body section; The cross-sectional dimensions of the first mating segment and the second mating segment along the axial direction of the main body segment are greater than the cross-sectional dimension of the main body segment along the axial direction thereof.

4. The control rod assembly drop buffer device according to claim 3, characterized in that: The main body section is integrally provided with the first mating section and the second mating section.

5. The control rod assembly drop buffer device according to claim 1, characterized in that: The first mating section is connected to one end of the second mating section via a first boss, and the cross-sectional dimension of the first boss decreases along the direction from the first mating section to the second mating section; A second boss is provided at one end of the second mating segment facing away from the first mating segment, and the cross-sectional dimension of the second boss decreases gradually along the direction facing away from the second mating segment.

6. The control rod assembly drop buffer device according to claim 5, characterized in that: The first boss has a first annular inclined surface, and the circumferential dimension of the first boss near one end of the first fitting section corresponds to the circumferential dimension of the first fitting cavity; The second boss has a second annular inclined surface, and the circumferential dimension of the second boss close to the second fitting section corresponds to the circumferential dimension of the second fitting cavity.

7. The control rod assembly drop buffer device according to claim 6, characterized in that: A first buffer groove is provided at one end of the first matching cavity away from the second matching cavity, and the cross-sectional dimension of the first buffer groove increases gradually in the direction away from the second matching cavity; The first matching cavity and the second matching cavity are connected via a second buffer groove, and the cross-sectional dimension of the second buffer groove increases gradually in a direction away from the second matching cavity.

8. The control rod assembly drop buffer device according to claim 1, characterized in that: The driving rod and the guide cylinder cooperate to form at least one level of rod drop buffer; Each level of the rod drop buffer includes a group of the first matching segment and the first matching cavity, and a group of the second matching segment and the second matching cavity.

9. A rod drop buffering method, characterized in that: The control rod assembly drop buffer device according to any one of claims 1 to 8 is used, wherein the buffering method comprises: Receive shutdown signal; The control drive rod and the control rod assembly connected to its bottom end are controlled to slide axially along the guide cylinder; wherein, the drive rod undergoes at least one level of buffering during the axial sliding along the guide cylinder, so that the drive rod is decelerated to a target rod drop speed.

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