Low-flow-resistance frame type control rod assembly

Abstract

The invention discloses a low-flow-resistance frame type control rod assembly and belongs to the technical field of nuclear. The control rod assembly mainly comprises an upper connecting base, a lower connecting base and a supporting pipe, the supporting pipe is fixedly connected with the upper connecting base and the lower connecting base through connecting rib plates arranged at the two ends respectively, and axial gaps are formed between the upper end face of a pipe body and the lower end face of the upper connecting base and between the lower end face of the pipe body and the upper end face of the lower connecting base. The axial gap provides a flow passage for the coolant. The low-flow-resistance frame type control rod assembly can effectively reduce the flow resistance of a coolant during axial flow, improve the balance of flow distribution of a pool type reactor core and improve the safety of the reactor.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nuclear technology, and particularly relates to a low-flow-resistance frame type control rod assembly. BACKGROUND

[0002] The control rod assembly is an important safety assembly in the reactor core, and plays an important role in the safety and stability of the reactor operation process. In the pool-type reactor, the control rod assembly usually adopts a frame structure with a square cross section and uses hafnium as a neutron absorber. The control rod assembly is connected below the following fuel assembly. By driving the control rod assembly to move axially in the core guide tube, the power regulation and start-stop of the reactor are realized. During the operation of the control rod assembly, the coolant flows along the axial direction thereof. The flow resistance coefficient and flow rate of the control rod assembly directly affect the key thermal-hydraulic parameters such as the flow distribution of the reactor core. The existing control rod assembly mainly considers preventing interference caused by the irradiation deformation of the hafnium plate during the design stage, and does not fully consider the flow resistance performance, resulting in a high flow resistance coefficient of the control rod assembly, affecting the uniformity of the core flow distribution, and causing the risk of local high temperature of the control rod assembly. Therefore, providing a control rod assembly with an optimized flow resistance coefficient has a positive significance for improving the safety and reliability of the pool-type reactor. SUMMARY

[0003] The application aims to provide a low-flow-resistance frame type control rod assembly to reduce the flow resistance coefficient of the control rod assembly.

[0004] According to an embodiment of the application, a low-flow-resistance frame type control rod assembly is provided, which comprises an upper connecting seat, a lower connecting seat, a support tube, an absorber, and a connecting hook, wherein the support tube is arranged between the upper connecting seat and the lower connecting seat, the absorber is arranged around the support tube, and the connecting hook is arranged below the lower connecting seat. The support tube comprises a tube body and a connecting rib plate. The connecting rib plate is arranged at both ends of the tube body and extends along the axial direction of the tube body. The tube body is connected to the upper connecting seat and the lower connecting seat through the connecting rib plate. An axial gap is arranged between the upper end surface of the tube body and the lower end surface of the upper connecting seat, and an axial gap is arranged between the lower end surface of the tube body and the upper end surface of the lower connecting seat. The axial gaps provide a flow channel for the coolant.

[0005] In the control rod assembly, the support tube is connected to the upper connecting seat and the lower connecting seat through the connecting rib plate. The axial gap formed by the connecting rib plate increases the area of the flow channel for the coolant, which can effectively reduce the flow resistance coefficient of the control rod assembly in the axial direction.

[0006] Further, in some embodiments, the axial gap is not less than 0.5 mm.

[0007] Furthermore, in some embodiments, each end of the pipe body is provided with four connecting ribs, and the four connecting ribs are distributed at equal intervals around the circumference of the pipe body.

[0008] Furthermore, in some embodiments, the connecting stiffener includes a flow guiding surface, which forms an obtuse angle with the surface of the pipe body and an angle of 100°-175° with the axis of the pipe body.

[0009] Furthermore, in some embodiments, the upper connecting seat and the lower connecting seat are respectively provided with guide ports, and the guide ports are connected to the axial gap.

[0010] Furthermore, in some embodiments, the absorber is configured as a rectangular cylindrical structure formed by a first hafnium plate, a second hafnium plate, a third hafnium plate, and a fourth hafnium plate in sequence, and the upper connecting seat and the lower connecting seat are respectively provided with supporting surfaces, and the absorber falls within the projection range of the supporting surface along the axial direction of the supporting tube.

[0011] Furthermore, in some embodiments, the connecting hook is fixedly connected to the first hafnium plate and the third hafnium plate by bolts.

[0012] Furthermore, in some embodiments, the first hafnium plate and the third hafnium plate are sandwiched between the second hafnium plate and the fourth hafnium plate.

[0013] Furthermore, in some embodiments, adjacent hafnium plates in the absorber are connected by a sliding fastener, which is embedded in the hafnium plate and does not exceed the surface height of the hafnium plate.

[0014] Furthermore, in some embodiments, when the low flow resistance frame control rod assembly is installed in the reactor, it is connected to the connecting hook along with the fuel assembly and abuts against the lower connecting seat axially. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a low flow resistance frame-type control rod assembly in one embodiment;

[0016] Figure 2 for Figure 1 Schematic diagram of the AA section structure;

[0017] Figure 3 This is a schematic diagram of the upper connecting seat structure in one embodiment;

[0018] Figure 4 This is a schematic diagram of the upper and lower connecting seat structure in one embodiment;

[0019] Figure 5 This is a schematic diagram of the lower structure of a pair of proportional control rod assemblies.

[0020] Meaning of reference signs:

[0021] 1 - upper connecting seat; 2 - support pipe; 3 - lower connecting seat; 4 - connecting hook; 5 - positioning plate; 6 - first positioning plate; 7 - third positioning plate; 8 - second positioning plate; 9 - fourth positioning plate; 10 - pipe body; 11 - rib plate; 12 - upper connecting seat absorber connecting position; 13 - lower connecting seat absorber connecting position; 14 - support surface; 15 - sliding buckle; 16 - axial gap; 17 - flow guide opening; 18 - lower end; 19 - screw; 20 - flow guide surface.

[0022] The purpose of the above drawings is to make a detailed description of the present application so that those skilled in the art can understand the technical concept of the present application, and is not intended to limit the present application. In order to express concisely, the above drawings only schematically draw the structures related to the technical features of the present application, and do not strictly draw the complete structures and all details according to the actual proportions. DETAILED DESCRIPTION

[0023] The present application will be further described in detail below with specific examples in conjunction with the drawings.

[0024] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The phrase "in one embodiment" appearing in various locations in the specification does not necessarily refer to the same embodiment, nor is it limited to a single or alternative embodiment. Those skilled in the art will appreciate that embodiments of the present application can be combined with other embodiments without structural conflict.

[0025] In the description herein, unless otherwise explicitly specified and limited, the technical terms "mounting", "connection", "connection" and the like should be broadly understood, for example, it can be movable connection, or fixed connection or integral. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0026] In the description herein, the terms indicating the orientation or position relationship such as "upper", "lower", "left", "right", "transverse", "longitudinal", "height", "length", "width" and the like are intended to accurately describe the embodiments and simplify the description, and are not intended to limit the parts or structures involved to have a specific orientation, to be installed or operated in a specific orientation, and cannot be understood as limiting the embodiments herein.

[0027] In the description herein, the terms "first", "second" and the like are only used to distinguish different objects, and cannot be understood as indicating relative importance or limiting the number, specific order or primary and secondary relationship of the described technical features. In the description herein, the meaning of "multiple" is at least two.

[0028] The pool type reactor is one of the most common structural forms in the current research reactor, and the control rod assembly in the pool type reactor generally adopts a frame structure with a square cross section, adopts hafnium plate as a neutron absorber, and simultaneously connects a following fuel assembly below the control rod assembly, drives the control rod assembly and the following fuel assembly to move axially in a reactor core guide cylinder through a control rod drive mechanism, and realizes the start and stop of the reactor, power regulation in operation, and emergency shutdown in accident conditions by maintaining or changing the position of the neutron absorber of the control rod assembly relative to the active region of the reactor core. In some accident conditions, such as earthquake conditions, the core bottom plate and the lower grid will transmit the load to the core to cause the control rod guide cylinder and the control rod assembly to vibrate and further cause deformation risk, thereby affecting the structural integrity and insertability of the control rod assembly. Meanwhile, in the prior art, the structural design of the control rod assembly mainly considers optimizing the assembly and connection forms of various parts to prevent the hafnium plate from being deformed and interfering after being irradiated, and the flow resistance coefficient and other characteristics of the control rod assembly are not fully considered. The present application finds that the coolant flow resistance coefficient in the control rod assembly has a significant influence on the thermal hydraulic performance of the core flow distribution, for example, for the following fuel assembly arranged below the control rod assembly, the flow distribution state in the gap between different fuel plates in the assembly will be significantly affected by the flow resistance characteristics of the control rod assembly. The existing control rod assembly has a small flow cross section and a high coolant flow resistance coefficient, which affects the uniformity of the core flow distribution and may cause local temperature of the control rod assembly to be too high. If the structural material on the cross section is reduced, the strength of the control rod assembly will be reduced, which is not conducive to the reliability in earthquake and other accident conditions.

[0029] In order to overcome the above-mentioned deficiencies of the prior art, embodiments of the present application provide a low-flow-resistance frame type control rod assembly, as shown in Figure 1 , which comprises an upper connecting seat 1, a lower connecting seat 3, a support tube 2, an absorber and a connecting hook 4. The support tube 2 is arranged between the upper connecting seat 1 and the lower connecting seat 3, the absorber is arranged around the support tube 2, and the connecting hook 4 is arranged at the bottom of the lower connecting seat 3. In the control rod assembly, in combination with Figure 3 and Figure 4 , the support tube 2 comprises a tube body 10 and a connecting rib plate 11, the connecting rib plate 11 is arranged at both ends of the tube body 10 and extends along the axial direction of the tube body 10. The tube body 10 is connected with the upper connecting seat 1 and the lower connecting seat 3 through the connecting rib plate 11, and an axial gap 16 is arranged between the tube body and the upper connecting seat 1 and the lower connecting seat 3, respectively. The axial gap 16 provides a flow channel for the coolant, and the coolant can flow along the axial direction of the control rod assembly through the axial gap 16, thereby reducing the flow resistance of the coolant without reducing the structural strength on the cross section of the control rod assembly. In a preferred embodiment, the axial width d of the axial gap 16, i.e. the distance between the end face of the tube body 10 and the lower end face of the upper connecting seat 1 / the upper end face of the lower connecting seat 3, is not less than 0.5 mm.

[0030] In the preferred embodiment, four connecting ribs 11 are arranged at each end of the tube body 10, and are equidistantly distributed in the circumferential direction of the tube body 10. For a control rod assembly with a square cross section, the connecting ribs 11 extend along the diagonal direction of the square cross section in the cross section. Further, the connecting ribs 11 include a flow guide surface 20, which is inclined at an obtuse angle relative to the surface of the tube body 10 (i.e. the direction of the tube body 10's generatrix), and forms an angle of 100°-175° with the axis of the tube body 10. This can reduce the flow resistance of the axial flow of the coolant while relieving stress concentration and improving mechanical strength. In the preferred embodiment, the thickness of the connecting ribs is not less than 2 mm, and the specific wall thickness can be determined according to the results of thermal-hydraulic calculation.

[0031] In the preferred embodiment, in combination with Figure 3 and Figure 4 , the upper connecting seat 1 and the lower connecting seat 3 are respectively provided with flow guide openings 17, which are in the form of grooves and extend through the wall of the upper connecting seat 1 / lower connecting seat 3 in the transverse direction, and are in communication with the axial gap 16. The space formed by the axial gap 16 and the flow guide openings 17 serves as a flow channel for the coolant, further reducing the flow resistance without affecting the structural strength.

[0032] As shown in Figure 2 , the cross section of the absorber is in the form of a rectangular cylindrical structure, which is formed by the first cladding plate 6, the second cladding plate 8, the third cladding plate 7 and the fourth cladding plate 9 connected in sequence. The upper connecting seat 1 is provided with an upper connecting seat absorber connecting site 12, and the upper end of the cladding plate is fixedly connected to the upper connecting seat absorber connecting site 12 and the support surface 14. The lower connecting seat 3 is provided with a lower connecting seat absorber connecting site 13 and a support surface 14, and the lower end of the cladding plate is fixedly connected to the lower connecting seat absorber connecting site 13. In the cross section, the projection of the absorber on the support surface 14 in the axial direction of the support tube 2 falls within the range of the support surface 14, i.e. the cross-sectional area of the support surface 14 is greater than that of the absorber. When the control rod assembly is subjected to vibration, the transverse load is borne by the support surface 14, so as to avoid deformation of the cladding plate due to the transverse load.

[0033] In combination with Figure 1The connecting hook 4 is fixedly connected to the first clamping plate 6 and the third clamping plate 7 through the screw 19, and the connecting hook 4 and the lower connecting seat 3 are not directly rigidly connected, so as to further reduce unnecessary connecting structure, increase the distance from the control rod assembly axis, and optimize the flow resistance coefficient and the coolant flow distribution between the follower fuel assemblies. The first clamping plate 6 and the third clamping plate 7 are clamped between the second clamping plate 8 and the fourth clamping plate 9, and the two ends of the first clamping plate 6 and the third clamping plate 7 are respectively abutted to the surfaces of the second clamping plate 8 and the fourth clamping plate 9, so as to help the second clamping plate 8 and the fourth clamping plate 9 to share the transverse load. The adjacent clamping plates are connected through the slide buckle 15, the surface of the clamping plate is slotted, the slide buckle 15 is embedded in the slot on the surface of the clamping plate, so that the slide buckle 15 does not exceed the surface height of the clamping plate, so as to avoid occupying the coolant flow area and further reduce the flow resistance.

[0034] When the control rod assembly is installed in the reactor, the follower fuel assembly is connected to the connecting hook 4 and abuts to the bottom of the lower connecting seat 3 in the axial direction, and when the control rod assembly falls rapidly, the impact load is borne by the lower connecting seat 3 and is conducted upward through the support tube 2, so as to avoid that the clamping plates arranged around the support tube 2 bear the impact load and are deformed.

[0035] The local structure of the lower end of the control rod in a comparative example is shown in Figure 5 The connecting hook 4 is fixedly connected to the support tube 2 through the screw 19, which increases the thickness of the connecting structure and occupies the space for coolant flow. During the operation, the coolant can only flow through the narrow gap on the side of the lower end head 18, which leads to the significant deterioration of the flow resistance of the control rod assembly.

[0036] According to the calculation, the overall flow resistance coefficient of the control rod assembly and the follower fuel assembly in the comparative example reaches 39%, and the minimum flow uneven distribution factor between the plates in the follower fuel assembly is 0.78; while the overall flow resistance coefficient of the control rod assembly and the follower fuel assembly in the embodiment of the application is optimized to 30%, and the minimum flow uneven distribution factor between the plates in the follower fuel assembly is optimized to 0.918, and on this basis, the maximum deformation amount allowed by the anti-seismic performance of the control rod assembly provided in the embodiment reaches 1.63 mm.

[0037] The low-flow-resistance frame type control rod assembly provided by the embodiment of the present application has a flow resistance coefficient of the control rod assembly not more than 1 / 3 of the overall flow resistance coefficient of the control rod assembly and the following fuel assembly under normal operation conditions; the following fuel assembly plate flow uneven distribution factor can be optimized to 0.918-1.206; and the deformation amount of the top and bottom of the control rod assembly in the guide tube corresponding to the nodes is not more than 1.63 mm when the earthquake displacement time history of the core bottom plate and the lower grid plate position is input. The low-flow-resistance frame type control rod assembly provided by the present application effectively improves the flow resistance performance of the control rod assembly, improves the balance of the pool type reactor core flow distribution, improves the structural strength of the control rod assembly, improves the structural integrity and insertability of the control rod assembly under the conditions of earthquakes and other accidents, and improves the overall safety of the pool type reactor.

[0038] The above embodiments are intended to further illustrate the present application in conjunction with the accompanying drawings, so that those skilled in the art can understand the technical concept of the present application. Within the scope of the present application, the structures of the parts involved are optimized or equivalently replaced, and the embodiments in different embodiments are combined without structural and principle conflicts, all of which fall within the protection scope of the present application.

Claims

1. A low-flow-resistance frame-type control rod assembly, comprising an upper connecting seat, a lower connecting seat, a support tube, an absorber, and a connecting hook, wherein the support tube is disposed between the upper connecting seat and the lower connecting seat, the absorber is arranged around the support tube, and the connecting hook is disposed below the lower connecting seat, characterized in that, The support tube includes a tube body and connecting ribs. The connecting ribs are disposed at both ends of the tube body and extend along the axial direction of the tube body. The tube body is connected to the upper connecting seat and the lower connecting seat respectively through the connecting ribs. An axial gap is provided between the upper end face of the tube body and the lower end face of the upper connecting seat, and an axial gap is provided between the lower end face of the tube body and the upper end face of the lower connecting seat. The axial gaps provide a flow channel for the coolant.

2. The low flow resistance frame-type control rod assembly according to claim 1, characterized in that, The axial clearance is not less than 0.5 mm.

3. The low flow resistance frame-type control rod assembly according to claim 1 or 2, characterized in that, Each end of the pipe body is provided with four connecting ribs, which are distributed at equal intervals around the circumference of the pipe body.

4. The low flow resistance frame-type control rod assembly according to claim 1 or 2, characterized in that, The connecting stiffener includes a flow guiding surface, which forms an obtuse angle with the surface of the pipe body and an angle of 100°-175° with the axis of the pipe body.

5. The low flow resistance frame-type control rod assembly according to claim 1 or 2, characterized in that, The upper connecting seat and the lower connecting seat are respectively provided with flow guide ports, and the flow guide ports are connected to the axial clearance.

6. The low flow resistance frame-type control rod assembly according to claim 1 or 2, characterized in that, The absorber is configured as a rectangular cylindrical structure formed by a first hafnium plate, a second hafnium plate, a third hafnium plate, and a fourth hafnium plate in sequence. The upper connecting seat and the lower connecting seat are respectively provided with supporting surfaces, and the absorber falls within the projection range of the supporting surface along the axial direction of the supporting tube.

7. The low flow resistance frame-type control rod assembly according to claim 6, characterized in that, The connecting hook is fixedly connected to the first hafnium plate and the third hafnium plate by bolts.

8. The low flow resistance frame-type control rod assembly according to claim 6, characterized in that, The first hafnium plate and the third hafnium plate are sandwiched between the second hafnium plate and the fourth hafnium plate.

9. The low flow resistance frame-type control rod assembly according to claim 8, characterized in that, The adjacent hafnium plates in the absorber are connected by a sliding fastener, which is embedded in the hafnium plate and does not exceed the surface height of the hafnium plate.

10. The low flow resistance frame-type control rod assembly according to claim 6, characterized in that, When the low flow resistance frame control rod assembly is installed in the reactor, it is connected to the connecting hook along with the fuel assembly and abuts against the lower connecting seat axially.

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