A reactor bottom structure for a research reactor and a method of installing the same

Abstract

The present application relates to the technical field of nuclear reactor structure, and particularly relates to a reactor bottom structure for research reactor and a mounting method, which is mounted in a lower chamber and comprises: an anti-seismic support structure fixed on the bottom surface of the lower chamber, a blowdown pipeline system fixed on the anti-seismic support structure, a ventilation and cooling structure fixed on the top surface of the lower chamber, and a control rod drive mechanism installed upside down; a stator coil in the control rod drive mechanism is arranged in a cylinder in the ventilation and cooling structure, a pressure shell in the control rod drive mechanism is arranged in the anti-seismic support structure, an anti-seismic plate in the anti-seismic support structure is fixed on the pressure shell, and a drain connection pipe arranged at the bottom end of the control rod drive mechanism is connected with the blowdown pipeline system. The reactor bottom structure has compact structure size and provides limiting and cooling for the control rod drive mechanism, and the reactor bottom structure is further provided with the blowdown pipeline system, which regularly discharges radioactive waste to reduce the irradiation dose of the lower chamber.

Description

Technical Field

[0001] This invention relates to the field of nuclear reactor structure technology, and more specifically, to a reactor bottom structure for research reactors and its installation method. Background Technology

[0002] The reactor top structure is one of the important components of the current mainstream pressurized water reactor. It is located at the top of the reactor and its main functions include: (1) providing limits for the control rod drive mechanism (CRDM) to limit excessive deformation of the drive mechanism under seismic conditions in order to maintain its normal function; (2) providing cooling for the CRDM to ensure that the temperature of the CRDM does not exceed the limit.

[0003] However, in some research reactors, the core is located at the bottom of the pressure vessel, requiring ample space above for operations such as sample loading / unloading and refueling. To avoid impacting the operating space above the core, the CRDM cannot be placed at the top of the reactor. Therefore, unlike mainstream pressurized water reactors, the CRDM in these research reactors is located at the bottom of the reactor. Consequently, the top structure used in mainstream pressurized water reactors to protect the CRDM is no longer suitable for these research reactors. Furthermore, to save space, the CRDMs in these research reactors are arranged in layers, with the stator coils of the upper and lower layers staggered to achieve a compact arrangement. However, this layered arrangement results in inconsistent CRDM heights, and existing structures cannot accommodate CRDMs with both heights.

[0004] Furthermore, the reactor bottom space of the aforementioned research reactor is limited, and the size of the transport passage is also restricted, which places strict requirements on the dimensions of the reactor bottom structure. In addition, the research reactor needs to periodically discharge radioactive waste generated inside the reactor from the bottom of the pressure vessel, requiring a dedicated wastewater discharge pipeline system to be installed at the reactor bottom.

[0005] Therefore, a new reactor bottom structure is needed to meet the unique layout, space requirements, and wastewater discharge needs of the aforementioned research reactor CRDM. Summary of the Invention

[0006] The purpose of this invention is to provide a reactor bottom structure and installation method for research reactors, which solves the problems of difficulty in meeting the safety requirements, installation space requirements and wastewater discharge requirements under the unique CRDM layout of research reactors.

[0007] This invention is achieved through the following technical solution:

[0008] In a first aspect, a reactor bottom structure for research reactors is provided, installed inside the reactor under chamber, comprising: an anti-seismic support structure fixed to the bottom surface of the reactor under chamber, a sewage pipe system fixed to the anti-seismic support structure, a ventilation and cooling structure fixed to the top surface of the reactor under chamber, and an inverted control rod drive mechanism.

[0009] The stator coil in the control rod drive mechanism is disposed in the cylinder of the ventilation and cooling structure. The pressure-resistant shell in the control rod drive mechanism is disposed inside the seismic support structure. The seismic plate in the seismic support structure is fixed on the pressure-resistant shell. The drainage pipe at the bottom of the control rod drive mechanism is connected to the sewage pipeline system.

[0010] Furthermore, the seismic support structure also includes an upper casing, a middle casing, a lower casing, support legs, support columns, support ring plates, limiting blocks, and adjusting screws. The upper casing, middle casing, and lower casing are fixedly mounted on the support columns to form the main frame. The support legs are fixedly mounted on the lower casing. The support ring plates are fixedly mounted on the upper casing. The limiting blocks are fixedly mounted on the support ring plates. The adjusting screws are fixedly mounted on the limiting blocks. The adjusting screws adjust the gap between themselves and the seismic support plates by rotating them.

[0011] Furthermore, the upper, middle, and lower circumferential tubes and the supporting ring plate are all two-lobed structures, and the two lobes of the upper, middle, and lower circumferential tubes are connected by a lobed connecting plate; the two lobes of the supporting ring plate are connected by the limiting support block.

[0012] Furthermore, a transition plate is provided between the support leg and the bottom surface of the stack chamber.

[0013] Furthermore, the ventilation and cooling structure also includes a flange and an exhaust port pipe. The exhaust port pipe is located on one side of the flange connecting cylinder and is connected to an external ventilation system. There is a gap between the cylinder and the stator coil in the control rod drive mechanism.

[0014] Furthermore, both the flange and the cylinder are of a segmented structure; the flange is also provided with flange stiffeners, and the diameter of the flange is larger than the diameter of the top opening of the stacked chamber; the outer side of the cylinder is also provided with cylinder stiffeners.

[0015] Furthermore, the sewage pipeline system includes upper and lower sewage pipelines, a drainage ring pipe, and a main drainage outlet pipe; each sewage pipeline includes a primary valve, a secondary valve, and a drainage branch pipe; the outlet of the primary valve is connected to the inlet of the secondary valve through a drainage branch pipe, the outlet of the secondary valve is also connected to the inlet of the drainage ring pipe through a drainage branch pipe, and the outlet of the drainage ring pipe is connected to the main drainage outlet pipe; the inlet of the primary valve is connected to the drainage pipe in the control rod drive mechanism, and the number of primary valves is the same as the number of control rod drive mechanisms.

[0016] Furthermore, the secondary valves in the upper sewage pipes are installed on the valve fixing plates of the upper casing, while the secondary valves in the lower sewage pipes are installed on the valve fixing plates of the middle casing.

[0017] Furthermore, the drainage ring pipe is configured as a two-section structure that matches the two-lobed structure of the upper or middle casing, and the drainage ring pipe is fixed on the support column below the secondary valve in the lower sewage pipeline.

[0018] Secondly, a method for installing a reactor bottom structure is provided, the method comprising the following steps:

[0019] Install the control rod drive mechanism on the bottom head of the reactor pressure vessel;

[0020] The ventilation and cooling structure is transported in segments to the under-stack compartment and installed on the top surface of the under-stack compartment, and then the segments are connected to each other.

[0021] The anti-vibration plate is fixed to the pressure-resistant shell of the control rod drive mechanism;

[0022] Connect the primary valve in the sewage pipeline system to the drain pipe of the control rod drive mechanism;

[0023] The seismic support structure is transported in segments to the under-stack chamber; the two segments of the lower casing are connected together, and the legs and support columns are fixed to the lower casing; the secondary valves are fixed to the valve fixing plates of the upper and middle casings, and the middle and upper casings are fixed to the support columns in sequence; then the support ring plate is fixedly installed on the upper casing.

[0024] Fix the drainage ring pipe in the sewage pipeline system to the support column below the secondary valve in the lower sewage pipeline, and connect all the pipelines in the sewage pipeline system to complete the installation.

[0025] The technical solution of the present invention has at least the following advantages and beneficial effects:

[0026] The reactor bottom structure disclosed in this invention features a compact size and provides containment and cooling for the CRDM. It also includes a wastewater discharge system to periodically discharge radioactive waste, reducing the radiation dose to the underreaming chamber. The seismic support structure and ventilation / cooling structure are designed separately, significantly reducing equipment height and facilitating installation and transportation within the confined space of the underreaming chamber. The wastewater discharge system enhances safety with two valves, ensuring pressure boundary integrity even in the event of a primary valve leak. Furthermore, the layered design and the use of a drainage loop to connect multiple branches greatly simplify piping layout and facilitate the installation and disassembly of complex piping systems in confined spaces. The ventilation / cooling structure, by segmenting the structure, allows for individual segment transportation, installation, and disassembly, significantly reducing the space requirements for the ventilation / cooling structure. Attached Figure Description

[0027] Figure 1It is a diagram showing the layout of the stack bottom structure in the sub-cells;

[0028] Figure 2 This is a schematic diagram of the two halves of the seismic support structure and sewage pipeline system.

[0029] Figure 3 This is the main view of the seismic support structure;

[0030] Figure 4 This is a top view of the seismic support structure;

[0031] Figure 5 This is a cross-sectional view of the seismic support structure (AA).

[0032] Figure 6 This is the main view of the ventilation and cooling structure;

[0033] Figure 7 This is a top view of the ventilation and cooling structure;

[0034] Figure 8 This is a sectional view of the ventilation and cooling structure (BB).

[0035] Figure 9 This is the main view of the sewage pipeline system;

[0036] Figure 10 This is a top view of the sewage pipeline system;

[0037] Figure 11 This is a CC sectional view of the sewage pipeline system;

[0038] Figure 12 This is a schematic diagram of a single pipe in the sewage pipeline system;

[0039] Figure 13 This is a flowchart of the installation method for the stack base structure;

[0040] Icons: 1-Underreamed cell, 2-Sewage piping system, 3-Seismic support structure, 4-Ventilation and cooling structure, 5-Control rod drive mechanism, 6-Bottom head of reactor pressure vessel, 7-Upper casing, 8-Support column, 9-Middle casing, 10-Lower casing, 11-Leg, 12-Transition plate, 13-Connecting plate bolt, 14-Nut, 15-Valve fixing plate, 16-Split connecting plate, 17-Limiting block, 18-Block bolt, 19-Support ring plate, 20-Adjusting screw, 21-Top fixing bolt, 22-Seismic plate, 23-Flange, 24-Exhaust outlet pipe, 25-Cylinder, 26-Flange stiffener, 27-Cylinder stiffener, 28-Primary valve, 29-Secondary valve, 30-Drainage branch pipe, 31-Drainage ring pipe, 32-Drainage outlet main pipe. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0042] Example 1

[0043] like Figures 1-12 As shown, a reactor bottom structure for research reactors is provided, which is installed inside the reactor under chamber 1. It includes: an anti-seismic support structure 3 fixed to the bottom surface of the reactor under chamber 1, a sewage pipe system 2 fixed to the anti-seismic support structure 3, a ventilation and cooling structure 4 fixed to the top surface of the reactor under chamber 1, and an inverted control rod drive mechanism 5. The stator coil of the control rod drive mechanism 5 is disposed in the cylinder 25 of the ventilation and cooling structure 4, the pressure shell of the control rod drive mechanism 5 is disposed inside the anti-seismic support structure 3, the anti-seismic plate 22 of the anti-seismic support structure 3 is fixed to the pressure shell, and the drainage pipe at the bottom end of the control rod drive mechanism 5 is connected to the sewage pipe system 2.

[0044] In the specific implementation process, the reactor bottom structure used in this study is as follows: Figure 1 As shown, the control rod drive mechanism 5 is installed upside down at the bottom of the reactor. To save space, the control rod drive mechanism 5 is arranged in two layers. By staggering the stator coils of the two layers of control rod drive mechanisms 5, the control rod drive mechanisms 5 can be arranged closely together. The reactor bottom structure is installed inside the subreactor compartment 1. The seismic support structure 3 is fixed to the bottom surface of the subreactor compartment 1, the wastewater discharge system 2 is fixed to the seismic support structure 3, and the ventilation and cooling structure 4 is fixed to the top surface of the subreactor compartment 1. The cylindrical 25 part of the ventilation and cooling structure 4 surrounds the stator coils of the control rod drive mechanism 5 (the main heat-generating part of the control rod drive mechanism 5) inside. The drain pipe at the bottom of the control rod drive mechanism 5 is connected to the wastewater discharge system 2. Wastewater inside the reactor is discharged through the control rod drive mechanism 5 and then through the wastewater discharge system 2. The seismic support structure 3 encloses the pressure shell of the control rod drive mechanism 5 inside. The seismic plate 22 on the seismic support structure 3 is fixed to the pressure shell. The seismic support structure 3 controls the displacement of the control rod drive mechanism by limiting the displacement of the seismic plate 22, thereby preventing excessive displacement under seismic conditions.

[0045] Specifically, such as Figures 2-5As shown, the seismic support structure 3 is mainly composed of an upper casing 7, a middle casing 9, a lower casing 10, support legs 11, and support columns 8. Six support columns 8 are welded together to connect the upper casing 7, the middle casing 9, and the lower casing 10 into a single unit, and three support legs 11 are welded to the lower casing 10. The upper casing 7, the middle casing 9, and the lower casing 10 are all divided into two parts, connected as a whole by segment connecting plates 16, connecting plate bolts 13, and nuts 14. Therefore, the seismic support structure 3 can be divided into two parts during transportation and installation (e.g., ...). Figure 2 As shown), to accommodate the narrow space of the under-stack compartment 1. The seismic support structure 3 is fixed to the bottom surface of the under-stack compartment 1 by the support legs 11 and the top fixing bolts 21. A transition plate 12 is provided between the support legs 11 and the bottom surface of the under-stack compartment 1. The thickness of the transition plate 12 can be processed and adjusted on site to compensate for the height error of the bottom surface of the under-stack compartment 1.

[0046] The anti-seismic plate 22 is fixed to the pressure shell of the control rod drive mechanism 5, with one anti-seismic plate 22 corresponding to one control rod drive mechanism 5. The support ring plate 19 is welded to the upper casing 7. The support ring plate 19 is divided into two halves, which are welded to the two halves of the upper casing 7 respectively. The limiting block 17 is fixed to the support ring plate 19 by the block bolt 18. The limiting block 17 also connects the two halves of the support ring plate 19 into a whole. The adjusting screw 20 is fixed to the limiting block 17. The gap between the adjusting screw 20 and the anti-seismic plate 22 can be adjusted by rotating the adjusting screw 20. A certain gap should be maintained between the adjusting screw 20 and the anti-seismic plate 22 to allow the control rod drive mechanism 5 to shift outward due to the thermal expansion of the bottom head of the pressure vessel when the reactor is hot. At the same time, the gap value needs to be limited to prevent excessive deformation of the control rod drive mechanism 5 under seismic conditions.

[0047] Specifically, such as Figures 6-8As shown, the ventilation and cooling structure 4 mainly consists of a flange 23, an exhaust port pipe 24, and a cylinder 25, which are connected by welding. The flange 23, exhaust port pipe 24, and cylinder 25 are composed of a large circular plate and flange stiffeners 26, with the large circular plate forming the main structure of the flange 23. The large circular plate should be able to cover the top opening of the under-stall chamber 1 to form a closed ventilation channel. Since the diameter of the top opening of the under-stall chamber 1 is relatively large, a long portion of the large circular plate is suspended, thus requiring flange stiffeners 26 to enhance the rigidity of the flange 23. The main body of the flange 23 (i.e., the large circular plate) can be divided into four segments, which are connected by bolts. The cylinder 25 surrounds the control rod drive mechanism 5 to form a ventilation channel. The gap between the cylinder 25 and the control rod drive mechanism 5 should be controlled to prevent excessively large gaps from causing most of the cooling air to flow out from the edges instead of entering the internal control rod drive mechanism 5. The cylinder 25 is also divided into four sections, which are connected by bolts. Since the cylinder is prone to deformation after being divided, cylindrical stiffening plates 27 are installed on the outside of the cylinder to enhance its rigidity. Two exhaust port pipes 24 are installed on the flange 23, which are connected to the external ventilation system. Cooling air is drawn through the control rod drive mechanism 5 to cool it.

[0048] Specifically, such as Figures 9-12 As shown, the inlet of the sewage pipeline system 2 is a primary valve 28, which is welded to the drain pipe on the control rod drive mechanism 5. The number of primary valves 28 is the same as the number of control rod drive mechanisms 5. Secondary valves 29 are fixed on valve fixing plates 15 on the upper casing 7 and the middle casing 9. The primary valves 28 and secondary valves 29 are connected by drain branch pipes 30. The number of secondary valves 29 is the same as the number of control rod drive mechanisms 5. The outlet of each secondary valve 29 is connected to the drain ring pipe 31 through the drain branch pipe 30. The wastewater inside the reactor flows through the control rod drive mechanism 5, through the primary valves 28 and secondary valves 29, and is collected through the drain ring pipe 31, finally flowing to the external sewage system through the main drain outlet pipe 32.

[0049] The sewage pipeline system 2 is arranged in two layers to accommodate the layered arrangement of the control rod drive mechanism 5. The primary valve 28 of the upper pipeline is welded to the upper control rod drive mechanism 5, and the secondary valve 29 is installed on the valve fixing plate 15 of the upper casing 7. The primary valve 28 of the lower pipeline is welded to the lower control rod drive mechanism 5, and the secondary valve 29 is installed on the valve fixing plate 15 of the middle casing 9. The drainage ring pipe 31 is configured as a two-section structure matching the two-part structure of the upper casing 7 or the middle casing 9. The drainage ring pipe 31 is fixed to the support column 8 below the secondary valve 29 in the lower sewage pipeline. It should be noted that the secondary valves 29 in both the upper and lower sewage pipelines are connected to the drainage ring pipe 31 via drainage branch pipes 30.

[0050] The reactor bottom structure disclosed in the above embodiments has a compact structural size and provides containment and cooling for the CRDM. The reactor bottom structure also includes a wastewater discharge system 2 to periodically discharge radioactive waste to reduce the radiation dose to the underreaming chamber 1. The seismic support structure 3 and the ventilation and cooling structure 4 are designed separately, significantly reducing the equipment height and facilitating installation and transportation within the confined space of the underreaming chamber 1. The wastewater discharge system 2 enhances safety through the use of two valves; even if the primary valve 28 leaks, the secondary valve 29 can still maintain the integrity of the pressure boundary. Furthermore, the wastewater discharge system 2 is layered and uses a drainage loop 31 to connect and aggregate multiple branches, greatly simplifying the pipeline layout and enabling the installation and disassembly of complex pipeline systems in confined spaces. The ventilation and cooling structure 4, by dividing the structure into segments, can also be transported, installed, and disassembled individually, significantly reducing the space requirements for the ventilation and cooling structure 4.

[0051] Example 2

[0052] like Figure 13 As shown, a method for installing a reactor bottom structure is provided, the method including the following steps:

[0053] The control rod drive mechanism 5 is installed on the bottom head 6 of the reactor pressure vessel;

[0054] The ventilation and cooling structure 4 is transported to the under-stack compartment 1 in segments and installed on the top surface of the under-stack compartment 1. The segments are then connected to each other.

[0055] The anti-vibration plate 22 is fixed to the pressure-resistant shell of the control rod drive mechanism 5;

[0056] Connect the primary valve 28 in the sewage pipeline system 2 to the drainage pipe of the control rod drive mechanism 5;

[0057] The seismic support structure 3 is transported in segments to the under-stack chamber 1; the two segments of the lower casing 10 are connected together, and the support legs 11 and the support columns 8 are fixed to the lower casing 10; the secondary valve 29 is fixed to the valve fixing plates 15 of the upper casing 7 and the middle casing 9, and the middle casing 9 and the upper casing 7 are fixed to the support columns 8 in sequence; then the support ring plate 19 is fixedly installed on the upper casing 7.

[0058] Fix the drainage ring pipe 31 in the sewage pipeline system 2 to the support column 8 below the secondary valve 29 in the lower sewage pipeline, and connect each pipeline in the sewage pipeline system 2 to complete the installation.

[0059] When multiple reactor bottom structural components adopt a split design, the above installation method can be used to complete the installation of the reactor bottom structure in a relatively small reactor bottom compartment. Although the structure adopts a split design, it still has high strength through the setting of reinforcing ribs and other structures, which can ensure the safety of the reactor in the event of an earthquake.

[0060] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A reactor bottom structure for research purposes, characterized in that, Installed inside the under-stack compartment (1), including: an anti-seismic support structure (3) fixed to the bottom surface of the under-stack compartment (1), a sewage pipe system (2) fixed to the anti-seismic support structure (3), a ventilation and cooling structure (4) fixed to the top surface of the under-stack compartment (1), and an inverted control rod drive mechanism (5). The stator coil in the control rod drive mechanism (5) is set in the cylinder (25) in the ventilation and cooling structure (4), the pressure shell in the control rod drive mechanism (5) is set inside the anti-vibration support structure (3), the anti-vibration plate (22) in the anti-vibration support structure (3) is fixed on the pressure shell, and the drain pipe at the bottom of the control rod drive mechanism (5) is connected to the sewage pipe system (2). The seismic support structure (3) includes an upper casing (7), a middle casing (9), a lower casing (10), a support leg (11), a support column (8), a support ring plate (19), a limiting block (17), and an adjusting screw (20). The upper casing (7), the middle casing (9), and the lower casing (10) are fixedly mounted on the support column (8) to form the main frame. The support leg (11) is fixedly mounted on the lower casing (10). The support ring plate (19) is fixedly mounted on the upper casing (7). The limiting block (17) is fixedly mounted on the support ring plate (19). The adjusting screw (20) is fixedly mounted on the limiting block (17). The adjusting screw (20) is adjusted by rotating to adjust the gap between itself and the seismic plate (22). The upper circumferential tube (7), the middle circumferential tube (9), the lower circumferential tube (10), and the supporting ring plate (19) are all two-part structures. The two parts of the upper circumferential tube (7), the middle circumferential tube (9), and the lower circumferential tube (10) are connected by a split connecting plate (16). The two parts of the supporting ring plate (19) are connected by a limiting block (17). The ventilation and cooling structure (4) includes a flange (23) and an exhaust port pipe (24). The exhaust port pipe (24) is located on one side of the flange (23) connecting to the cylinder (25), and the exhaust port pipe (24) is connected to the external ventilation system. Both the flange (23) and the cylinder (25) are split structures. The sewage pipeline system (2) includes upper and lower sewage pipelines, a drainage ring pipe (31) and a drainage outlet main pipe (32); each sewage pipeline includes a primary valve (28), a secondary valve (29) and a drainage branch pipe (30); wherein, the secondary valve (29) in the upper sewage pipeline is installed on the valve fixing plate (15) of the upper casing (7), and the secondary valve (29) in the lower sewage pipeline is installed on the valve fixing plate (15) of the middle casing (9); The drainage ring pipe (31) is configured as a two-section structure that matches the two-part structure of the upper casing (7) or the middle casing (9). The drainage ring pipe (31) is fixed on the support column (8) below the secondary valve (29) in the lower sewage pipeline.

2. The reactor bottom structure for research reactors as described in claim 1, characterized in that, A transition plate (12) is also provided between the support leg (11) and the bottom surface of the stack chamber (1).

3. The reactor bottom structure for research reactors as described in claim 1, characterized in that, There is a gap between the cylinder (25) and the stator coil in the control rod drive mechanism (5).

4. The reactor bottom structure for research reactors as described in claim 3, characterized in that, Flange (23) is also provided with flange stiffener (26), and the diameter of flange (23) is larger than the diameter of the top opening of the stacked chamber (1); cylindrical stiffener (27) is also provided on the outside of the cylinder (25).

5. A reactor bottom structure for research reactors as described in claim 1, characterized in that, The outlet of the primary valve (28) is connected to the inlet of the secondary valve (29) via a drainage branch pipe (30). The outlet of the secondary valve (29) is also connected to the inlet of the drainage ring pipe (31) via the drainage branch pipe (30). The outlet of the drainage ring pipe (31) is connected to the main drainage outlet pipe (32). The inlet of the primary valve (28) is connected to the drainage pipe in the control rod drive mechanism (5). The number of primary valves (28) is the same as the number of control rod drive mechanisms (5).

6. A method for installing a reactor bottom structure for a research reactor, applied to the reactor bottom structure for a research reactor as described in any one of claims 1-5; characterized in that, The method includes the following steps: The control rod drive mechanism (5) is installed on the bottom head (6) of the reactor pressure vessel; The ventilation and cooling structure (4) is transported in segments to the under-stack chamber (1) and installed on the top surface of the under-stack chamber (1), and then the segments are connected to each other. The anti-vibration plate (22) is fixed to the pressure-resistant shell of the control rod drive mechanism (5); Connect the primary valve (28) in the sewage pipeline system (2) to the drain pipe of the control rod drive mechanism (5); The seismic support structure (3) is transported in segments to the under-stack chamber (1); the two segments of the lower casing (10) are connected together, and the legs (11) and the support columns (8) are fixed on the lower casing (10); the secondary valve (29) is fixed on the valve fixing plates (15) of the upper casing (7) and the middle casing (9), and the middle casing (9) and the upper casing (7) are fixed on the support columns (8) in sequence; then the support ring plate (19) is fixed on the upper casing (7); Fix the drainage ring pipe (31) in the sewage pipeline system (2) to the support column (8) below the secondary valve (29) in the lower sewage pipeline, and connect each pipeline in the sewage pipeline system (2) to complete the installation.

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