A loop vacuum device and method for upper internals backseat condition

Abstract

This invention specifically relates to a primary loop vacuuming device and method for the upper reactor internals in the repositioned state, belonging to the field of nuclear reactor body maintenance. The device includes: a vacuuming cylinder for accommodating the upper reactor internals and its top control rod drive rod; a sealing assembly for using the device's own weight to compress and form initial contact stress, achieving an initial seal between the device and the core pressure vessel flange; an exhaust assembly connected to the inner cavity of the vacuuming cylinder for evacuating the primary loop; during the vacuuming process, the vacuuming pressure and the initial contact stress are superimposed to achieve further sealing between the device and the core pressure vessel flange; and a lifting assembly for lifting and guiding the device along a guide post inside the core pressure vessel to seat on the core pressure vessel flange. The method uses the device to perform primary loop vacuuming in the upper reactor internals in the repositioned state. This invention realizes primary loop vacuuming operations in the upper reactor internals in the repositioned state.

Description

Technical Field

[0001] This invention relates to the field of nuclear reactor body maintenance technology, specifically to a primary loop vacuum pumping device and method under the condition of upper reactor internal components reseating. Background Technology

[0002] During the overhaul of the M310 unit, the primary loop needs to be purged to reduce the air content in the steam generator U-tube to an acceptable threshold to ensure the normal conduct of subsequent tests. Primary loop purging typically includes static purging and dynamic purging. Static purging is achieved by gravity filling the primary loop with water to purge the pressure vessel, main pump, and pressurizer; dynamic purging is achieved by starting the main pump to expel air from the steam generator U-tube.

[0003] However, some M310 units, when using only gravity filling, cannot completely purge the air from the primary circuit. Therefore, it is necessary to briefly start the main pumps sequentially to assist in purging. After the main pumps start, the main system pressure drops rapidly, which adversely affects the service life of the main pumps.

[0004] Currently, some M310 units have adopted a primary loop vacuum venting system to assist dynamic venting, reducing the number of main pump starts. This vacuum system mainly consists of a sealed reactor dummy top and a vacuum platform. However, the sealed reactor dummy top was not designed with the upper in-core components in mind. Due to the limited volume of the sealed reactor dummy top, one of the necessary prerequisites for its field application is that the upper in-core components cannot be located in the reactor core. This results in significant room for optimization along the critical path from the end of the containment integrity test to fuel loading during the unit's ten-year overhaul.

[0005] Meanwhile, to meet the applicable requirements under different operating conditions, the vacuuming device needs to perform primary loop vacuuming in a radioactive environment of 30 mSv / h and with the refueling tank filled with 1700 ppm boric acid solution. It also requires strengthening the radiation resistance of the sealing components, controlling their compression set, and strictly limiting harmful elements such as mercury, lead, cadmium, and magnesium. Furthermore, the connection efficiency between the vacuuming device and the vacuuming pipeline in a radioactive environment must be fully considered to control and reduce the collective radiation dose received by personnel during the installation phase.

[0006] In summary, existing vacuum pumping devices cannot meet the requirement of vacuuming the primary loop while the upper internal components are in the reseating state. Summary of the Invention

[0007] The purpose of this invention is to solve the problem that existing vacuuming devices require the upper in-core components to be not located in the reactor core, which makes it impossible to perform primary loop vacuuming operations in the repositioned state, thus restricting the optimization of critical paths during major overhauls. This invention provides a primary loop vacuuming device and method for the upper in-core components in the repositioned state. This vacuuming device combines sealing, shielding, pressure bearing, and foreign object prevention functions, enabling primary loop vacuuming operations in the repositioned state of the upper in-core components, improving the quality and efficiency of vacuuming operations, and providing a pathway for optimizing critical paths during major overhauls.

[0008] To achieve the above objectives, in one aspect, the present invention provides a primary loop vacuum pumping device in the reseating state of the upper in-core components, comprising: The vacuum cylinder includes an upper cover, an upper cylinder, a lower cylinder, and a lower flange that are fixedly connected in sequence, forming a sealed cavity for accommodating the upper in-core components and the control rod drive rod on top of them that are seated back in the reactor core pressure vessel; the sealing surface of the lower flange is provided with at least one dovetail groove for installing sealing components. A sealing assembly, installed in the dovetail groove, is used to achieve an initial seal between the device and the core pressure vessel flange surface by relying on the compression of the device's own weight after the device is seated. The exhaust assembly is mounted on the upper cover and communicates with the inner cavity of the vacuum cylinder through a ball valve. It is used to connect to an external vacuum platform to perform vacuuming of the primary loop. During the vacuuming process, the vacuuming pressure is superimposed with the initial contact stress to achieve further sealing between the device and the flange face of the reactor core pressure vessel. The lifting assembly includes lifting lugs disposed on the upper cover and guide plates disposed circumferentially on the outside of the vacuum cylinder; the lifting lugs are used to connect external lifting equipment; the guide plates are configured to cooperate with guide columns inside the reactor core pressure vessel to guide the device to sit on the flange surface of the reactor core pressure vessel along the guide columns inside the reactor core pressure vessel.

[0009] As one possible approach, the sealing assembly is made of EPDM rubber with added reinforcing carbon black, metal sulfides and graphene, and its structure is a "one-piece O-ring" structure composed of inner and outer sealing rings.

[0010] As one possible implementation, the lower flange is gear-shaped, with multiple gear-shaped protrusions arranged circumferentially on its outer diameter, and the opening width of the gear-shaped protrusions matches the size of the main bolts of the reactor core pressure vessel. The sealing surface of the lower flange is provided with two dovetail grooves for fixing the sealing assembly. The opening position of the dovetail grooves avoids the sealing line and leakage hole of the core pressure vessel flange. The stop height of the lower flange is set to be less than the boss height of the main bolt hole of the reactor core pressure vessel to ensure that the device and the flange sealing surface of the reactor core pressure vessel achieve a soft contact seal through the sealing assembly.

[0011] As one possible implementation, the exhaust assembly includes at least one set of stainless steel pipes, with at least two sets of ball valves connected in series on each set of stainless steel pipes; in the non-operating state, the ball valves are in the closed state to ensure the sealing of the device; the stainless steel pipes are connected to the inner cavity of the vacuum cylinder; the interfaces of the stainless steel pipes are in the form of quick connectors, used to connect to the core water level gauge and the external vacuum platform through flexible hoses to perform vacuuming of the primary loop.

[0012] As one possible implementation, the lifting lug is welded to the upper cover via a support plate; there are four support plates, which are evenly distributed around the upper cover and welded to it, with the lifting lug located in the middle of the four support plates.

[0013] As one possible implementation, the upper cover, upper cylinder, and lower cylinder are all made of stainless steel; the upper cover, upper cylinder, lower cylinder, and lower flange are all fixedly connected by welding to form an integrated sealed cavity structure, which does not require on-site assembly; the internal height of the vacuum cylinder is designed to accommodate the upper in-core components and the control rod drive rod on top of them that are seated back in the reactor core pressure vessel, and to maintain a preset safe distance from the head of the control rod drive rod.

[0014] As one possible implementation, the device also includes a ladder, which is fixedly installed on the outer wall of the vacuum cylinder to facilitate workers to go up and down the device for maintenance and inspection.

[0015] As one possible implementation, the device also includes a tray, which is a square plate structure with a circular recessed plane at the center for accommodating the lower part of the device, and guide blocks and pads evenly distributed around its circumference. The pad is detachable, and the pallet can be adapted to the transportation, hoisting, storage or testing conditions of the device by removing and installing the pad; when the device is stored or transported, the pad is installed to provide stable support; when the device is tested, the pad is removed so that the device sits in the circular concave plane of the pallet, simulating the support state of the flange face of the reactor core pressure vessel. The guide block and pad are fixed to the pallet by pressure plates and bolts; lifting rings are evenly distributed at the four corners of the pallet.

[0016] To achieve the above objectives, in a second aspect, the present invention also provides a method for primary loop vacuuming under the reseating state of the upper reactor internals, using the aforementioned primary loop vacuuming device under the reseating state of the upper reactor internals to perform primary loop vacuuming under dry conditions with no water in the reactor core, comprising the following steps: Connect the external hoisting equipment to the lifting lugs of the device; hoist the device above the reactor core, aligning the guide plate with the guide column inside the reactor core pressure vessel; The device is guided to sit on the flange surface of the reactor core pressure vessel by the guide plate cooperating with the guide column inside the reactor core pressure vessel. After the device is seated, its own weight compresses the sealing assembly, forming initial contact stress and achieving initial sealing between the device and the flange surface of the reactor core pressure vessel. Connect the exhaust assembly to an external vacuuming platform, start the vacuuming platform, and extract the gas from the inner cavity of the vacuuming cylinder and the primary loop connected to it until the required vacuum level is reached; during this process, the vacuuming pressure and the initial contact stress are superimposed to achieve further sealing between the device and the flange face of the reactor core pressure vessel.

[0017] To achieve the above objectives, in a third aspect, the present invention also provides a method for primary loop vacuuming under the reseating state of the upper reactor internals, using the aforementioned primary loop vacuuming device under the reseating state of the upper reactor internals to perform primary loop vacuuming under wet conditions where the reactor core contains water, comprising the following steps: Connect the external hoisting equipment to the lifting lugs of the device; hoist the device above the reactor core, aligning the guide plate with the guide column inside the reactor core pressure vessel; Before the device comes into contact with the water surface, the ball valve on the venting assembly is remotely opened using a long-handled tool; The device is guided to sit on the flange face of the reactor core pressure vessel by the cooperation of the guide plate and the guide column inside the reactor core pressure vessel. During the sitting process, the gas in the inner cavity of the vacuum cylinder is compressed and discharged through the opened ball valve, while water begins to enter the inner cavity of the vacuum cylinder. After the device is seated, the self-weight of the device compresses the sealing assembly, forming initial contact stress and achieving initial sealing between the device and the flange face of the reactor core pressure vessel. After the device is fully seated and stable, use a long-handled tool to remotely close all ball valves. At this time, the inner cavity of the vacuum cylinder is filled with water and is in a sealed state. Connect the exhaust assembly to an external vacuuming platform, start the vacuuming platform, and extract the water and gas from the inner cavity of the vacuuming cylinder and the primary loop connected to it until the required vacuum level is reached; during this process, the vacuuming pressure and the initial contact stress are superimposed to achieve further sealing between the device and the flange face of the reactor core pressure vessel.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects: Optimized Critical Path: This device can perform primary loop vacuuming directly while the upper reactor internals are reseated, overcoming the limitation that existing dummy reactor top covers can only be used after the upper reactor internals are removed. This feature avoids the additional time consumption caused by complex operations such as repeated filling and draining, and repeated hoisting of reactor internals and water gates during the ten-year overhaul critical path, significantly optimizing the critical path from the end of the containment overall seal test to the pre-fuel loading stage.

[0019] Suitable for various refueling pool conditions: This device allows for remote operation of the ball valve on the top cover for internal pressure balancing and drainage. When the device is used when the reactor core contains water, controlling the opening and closing of the ball valve effectively balances the internal pressure. Before hoisting, the ball valve on the pipeline is opened to release gas from the device during hoisting and to drain water after the internal air is purged. Once fully in place, the valve is closed remotely, enabling installation when the reactor core contains water. The device material is not corroded by boric acid solution, and its surface cleanliness meets the "Cleanliness and Cleanliness Requirements for Nuclear Steam Supply Systems and Related System Equipment," and it is easy to clean. Therefore, the device can be used under various conditions, including low-level filling and draining, primary loop drainage without refueling pool drainage, and primary loop vacuuming when the refueling pool is full.

[0020] Integrated Functions, Safe and Reliable: This device integrates multiple functions including sealing, shielding, pressure bearing, and foreign object protection. The integrated cylindrical structure provides physical shielding and protection for the internal upper stack components. Self-weight sealing is achieved through the soft contact between the device's integrated O-ring sealing assembly and the pressure vessel flange. The sealing assembly possesses excellent radiation aging resistance and low compression set. Building upon the excellent aging resistance, radiation resistance, heat resistance, chemical resistance, steam resistance, and hydrophobicity of EPDM rubber, it further enhances the sealing assembly by adding reinforcing carbon black, metal sulfides, and graphene, limiting harmful elements such as mercury, lead, cadmium, and magnesium, and improving the material's strength. This further determines the minimum residual compression of the sealing assembly, ensuring high sealing performance and high reliability during vacuuming.

[0021] Easy to operate and highly adaptable: The quick-connect design of the exhaust assembly simplifies the connection between the device and the vacuum line, enabling rapid pre-vacuuming. Furthermore, the accompanying pallet facilitates transportation, hoisting, storage, and testing, meeting the requirements of various working environments.

[0022] Improved efficiency and reliability: The application of this device creates more favorable conditions for vacuum breaking, improves operational reliability, and increases the efficiency of the primary loop vacuuming critical path by 20%. Simultaneously, the device optimizes the drainage method of the refueling water tank in the safe unloading mode and provides new storage space and channels for draining boric acid water from the PTR refueling water tank. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of a primary loop vacuum pumping device in the reseating state of an upper in-core component according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the upper cover structure of a primary loop vacuum pumping device in the reseating state of an upper in-core component according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a tray of a primary loop vacuum device in the reseating state of an upper stack internal component according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the sealing assembly of a primary loop vacuum pumping device in the reseating state of an upper in-core component according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the lower flange of a primary loop vacuum pumping device in the reseating state of an upper in-core component according to an embodiment of the present invention.

[0024] In the diagram, 1-lifting lug; 2-support plate; 3-exhaust assembly; 4-upper cover; 5-upper cylinder; 6-lower cylinder; 7-guide plate; 8-lower flange; 9-ladder; 10-pallet; 11-guide block; 12-pressure plate; 13-pad plate; 14-lifting ring; 15-sealing assembly. Detailed Implementation

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0026] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0027] In the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0028] The terms “upper,” “lower,” “left,” “right,” “front,” “back,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are only for the convenience of description and simplification, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0029] The terms “include,” “comprising,” or any other variation thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments.

[0031] Example 1 like Figures 1 to 5 As shown, this embodiment provides a primary loop vacuum pumping device (hereinafter referred to as the device) in the upper reactor internal components reseating state, comprising: The vacuum cylinder includes a fixedly connected upper cover 4, upper cylinder 5, lower cylinder 6 and lower flange 8, forming a sealed cavity for accommodating the upper in-core components and the control rod drive rod on top of them that are seated back in the reactor core pressure vessel; the sealing surface of the lower flange 8 is provided with at least one dovetail groove for installing the sealing assembly 15. The sealing assembly 15 is installed in the dovetail groove and is used to form an initial contact stress by relying on the compression of the device's own weight after the device is seated, so as to achieve an initial seal between the device and the flange face of the reactor core pressure vessel. The exhaust assembly 3 is mounted on the upper cover 4 and is connected to the inner cavity of the vacuum cylinder through a ball valve. It is used to connect to an external vacuum platform to achieve vacuuming of the primary loop. During the vacuuming process, the vacuuming pressure is superimposed with the initial contact stress to achieve further sealing between the device and the flange face of the reactor core pressure vessel. The lifting assembly includes a lifting lug 1 disposed on the upper cover 4 and a guide plate 7 disposed circumferentially on the outside of the vacuum cylinder; the lifting lug 1 is used to connect external lifting equipment; the guide plate 7 is configured to cooperate with the guide post inside the reactor core pressure vessel to guide the guide post inside the reactor core pressure vessel to sit on the flange surface of the reactor core pressure vessel. Ladder 9 is fixedly installed on the outer wall of the vacuum cylinder to facilitate workers to go up and down the device for maintenance and inspection. The tray 10 is a square plate structure with a circular recessed plane in the center for accommodating the lower part of the device, and guide blocks 11 and pads 13 are evenly distributed around its circumference.

[0032] In this embodiment, the lifting lug 1 is welded to the upper cover 4 via the support plate 2. Specifically, the lifting lug 1 is welded to the support plate 2, and the support plate 2 is welded to the upper cover 4. There are 4 support plates 2, which are evenly distributed around the upper cover 4 and welded together. The lifting lug 1 is located in the middle of the 4 support plates 2. This structure can effectively disperse the concentrated stress generated during the hoisting process, prevent the device from deforming or being damaged due to excessive local stress, and achieve stable hoisting of the device. The guide plates 7 are welded to the outer circumferential surface of the vacuum cylinder, and their number and position correspond one-to-one with the guide columns inside the reactor core pressure vessel.

[0033] In this embodiment, the upper cover 4, the upper cylinder 5, and the lower cylinder 6 are all made of acid-resistant stainless steel. The upper cover 4, upper cylinder 5, lower cylinder 6 and lower flange 8 are all fixedly connected by welding to form an integrated sealed cavity structure, which does not require on-site assembly; among them, the upper cylinder 5 and the lower cylinder 6 are welded, the upper cover 4 is welded to the top of the upper cylinder 5, and the lower flange 8 is welded to the bottom of the lower cylinder 6. The internal height of the vacuum cylinder is designed to accommodate the upper in-core components that are seated back in the core pressure vessel and the control rod drive rod on top of them, while maintaining a preset safe distance from the head of the control rod drive rod.

[0034] In this embodiment, the lower flange 8 is gear-shaped, and multiple gear-shaped protrusions are arranged circumferentially on its outer diameter. The opening width of the gear-shaped protrusions matches the size of the main bolts of the reactor core pressure vessel. This structure can effectively avoid the situation where the horizontality is poor due to improper placement of the bolt hole plugs on the reactor pressure vessel cylinder flange after the device is placed. At the same time, it is used to fix the device with the pallet 10 during transportation, storage and test conditions. Two dovetail grooves for fixing the sealing assembly 15 are provided on the sealing surface of the lower flange 8. The opening position of the dovetail grooves avoids the sealing line and leakage hole of the core pressure vessel flange. The height of the stop of the lower flange 8 is set to be less than the height of the boss of the main bolt hole of the reactor core pressure vessel to ensure that a soft contact seal is achieved between the device and the flange sealing surface of the reactor core pressure vessel through the sealing assembly 15.

[0035] In this embodiment, the exhaust assembly 3 includes three sets of stainless steel pipes, and two sets of ball valves are connected in series on each set of stainless steel pipes; in the non-working state, the ball valves are in the closed state to ensure the sealing of the device. The stainless steel pipe is connected to the inner cavity of the vacuum cylinder; the stainless steel pipe interface adopts the form of quick coupling, which is used to connect the core water level gauge and the external vacuum platform through the hose, so that the inside of the device can quickly reach the condition of breaking the vacuum. Before hoisting the device, open the ball valve on the stainless steel pipe to release the gas inside the device during the hoisting process and drain the water after the air inside the device is purged. After the device is fully in place, use a long pole tool to remotely close the ball valve, thereby enabling the device to be installed when there is water in the reactor core, and at the same time, it can prepare for the separate drainage of the primary circuit.

[0036] In this embodiment, the pad 13 is detachable. By removing and installing the pad 13, the pallet 10 can be adapted to the transportation, hoisting, storage or testing conditions of the device. When storing or transporting the device, the pad 13 is installed to provide stable support. When testing the device, the pad 13 is removed so that the device sits in the circular concave plane of the pallet 10, simulating the support state of the core pressure vessel flange. Guide block 11 and pad 13 are fixed to pallet 10 by pressure plate 12 and bolts; lifting rings 14 are evenly distributed at the four corners of pallet 10.

[0037] In this embodiment, the sealing component 15 is made of EPDM rubber with added reinforcing carbon black, metal sulfides and graphene. Its structure is a "one-piece O-ring" structure composed of inner and outer sealing rings. The "one-piece O-ring" sealing ring is a double-acting sealing element with its own elastic sealing ability. The radial or axial contact stress generated by the pre-compression during initial installation is superimposed with the vacuum pressure to achieve the sealing function. The sealing assembly 15 is installed in the dovetail groove of the lower flange 8. During operation, the sealing assembly 15 is compressed by the gravity of the device itself, causing it to deform, thereby achieving a soft contact seal between the device and the flange sealing surface of the reactor core pressure vessel.

[0038] This embodiment also provides a method for primary loop vacuuming under the reseating state of the upper in-core components. The method utilizes the aforementioned primary loop vacuuming device under the reseating state of the in-core components to perform primary loop vacuuming under dry operating conditions with no water in the reactor core, and includes the following steps: Connect the external lifting equipment to the lifting lug 1 of the device using slings or lifting tools; lift the device above the reactor core so that the guide plate 7 is aligned with the guide column inside the reactor core pressure vessel; Guided by the cooperation of the guide plate 7 and the guide column inside the reactor core pressure vessel, the device is slowly lowered; the device relies on its own weight to sit on the flange surface of the reactor core pressure vessel along the core guide column; after the device is seated, the self-weight of the device compresses the sealing component 15 installed in the dovetail groove of the lower flange 8, so that it generates sufficient elastic deformation and forms a reliable initial sealing contact stress. Connect the hose to the external vacuum platform via a quick connector, start the vacuum platform to perform vacuuming and exhaust, extract the gas from the internal cavity of the device and the primary loop connected to it until the required vacuum level is reached; during the vacuuming process, the vacuuming pressure and the initial contact stress are superimposed to achieve a stronger self-tightening seal between the device and the reactor core pressure vessel.

[0039] This embodiment also provides a method for primary loop vacuuming under the reseating state of the upper in-core components. The method utilizes the aforementioned primary loop vacuuming device under the reseating state of the in-core components to perform primary loop vacuuming under wet conditions where the reactor core contains water. The method includes the following steps: Connect the external lifting equipment to the lifting lug 1 of the device using slings or lifting tools; lift the device above the reactor core so that the guide plate 7 is aligned with the guide column inside the reactor core pressure vessel; Before the device comes into contact with the water surface, use a long-handled tool to remotely open the ball valve on the venting assembly 3; Guided by the cooperation of the guide plate 7 and the guide column inside the reactor core pressure vessel, the device is slowly lowered; the device relies on its own weight to slowly fall into the water along the core guide column and sit on the flange surface of the reactor core pressure vessel; during the lowering process, the gas inside the device is compressed and discharged through the opened ball valve, while water begins to enter the inner cavity of the vacuum cylinder; after the device sits, the device's own weight compresses the sealing component 15 installed in the dovetail groove of the lower flange 8, causing it to generate sufficient elastic deformation and form a reliable initial sealing contact stress; After the device is fully seated and stable, use a long-handled tool to remotely close all ball valves. At this time, the vacuum cylinder is filled with water and is in a sealed state. Connect the quick connector of the exhaust assembly 3 to the external vacuum platform, start the vacuum platform, and extract the water and gas from the inner cavity of the device and the primary loop connected to it until the required vacuum level is reached; during the vacuuming process, the vacuuming pressure and the initial contact stress are superimposed to achieve a stronger self-tightening seal between the device and the reactor core pressure vessel.

[0040] The sealing component 15 is made of EPDM rubber, which has excellent radiation resistance and aging resistance, and can work stably for a long time in the special environment of a nuclear reactor. The "integrated O-ring" structure design is a double-acting seal with its own elastic sealing capability. It is installed in the double dovetail groove on the lower flange face of the vacuum device cylinder. The radial or axial contact stress generated by the pre-compression during initial installation, combined with the vacuum pressure, achieves the sealing function.

[0041] The exhaust assembly 3 is ingeniously designed. The upper cover 4 is equipped with the exhaust assembly 3, which, through three sets of stainless steel pipes and two sets of ball valves on each set, ensures that the device can balance internal pressure under different operating conditions. The interface uses quick-connect couplings, allowing for rapid connection to the core water level gauge and vacuum platform, quickly achieving the pre-vacuum state and significantly saving preparation time. Compared to traditional vacuum devices, it can establish a stable vacuum environment much faster.

[0042] The design of the device pallet allows it to be adapted to different operating conditions such as device transportation, storage, hoisting, and periodic testing by installing and removing pads, which improves the versatility and adaptability of the pallet and reduces the cost of using and maintaining the device.

[0043] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A primary loop vacuum pumping device for upper reactor internal components in a reseating state, characterized in that, include: The vacuum cylinder includes an upper cover (4), an upper cylinder (5), a lower cylinder (6), and a lower flange (8) that are fixedly connected in sequence, forming a sealed cavity for accommodating the upper in-core components and the control rod drive rod at the top of the reactor core pressure vessel; the sealing surface of the lower flange (8) is provided with at least one dovetail groove for installing the sealing assembly (15). The sealing component (15) is installed in the dovetail groove and is used to form a preliminary contact stress by relying on the self-weight compression of the primary loop vacuum device after the primary loop vacuum device is seated, thereby achieving a preliminary seal between the primary loop vacuum device and the core pressure vessel flange surface. The exhaust assembly (3) is set on the upper cover (4) and is connected to the inner cavity of the vacuum cylinder through a ball valve. It is used to connect to the external vacuum platform to vacuum the primary loop. During the vacuuming process, the vacuuming pressure and the initial contact stress are superimposed to achieve further sealing between the primary loop vacuuming device and the core pressure vessel flange. The hoisting assembly includes a lifting lug (1) disposed on the upper cover (4) and a guide plate (7) disposed circumferentially on the outside of the vacuum cylinder; the lifting lug (1) is used to connect external hoisting equipment; the guide plate (7) is configured to cooperate with the guide column inside the core pressure vessel to guide the primary loop vacuum device to sit on the flange surface of the core pressure vessel along the guide column inside the core pressure vessel.

2. The primary loop vacuum pumping device in the reseating state of the upper internal components according to claim 1, characterized in that, The sealing component (15) is made of EPDM rubber with added reinforcing carbon black, metal sulfides and graphene, and its structure is an integrated O-shaped structure composed of inner and outer sealing rings.

3. The primary loop vacuum pumping device in the reseating state of the upper internal components according to claim 2, characterized in that, The lower flange (8) is gear-shaped, and its outer diameter is circumferentially arranged with multiple gear-shaped protrusions. The opening width of the gear-shaped protrusions matches the size of the main bolts of the reactor core pressure vessel. The sealing surface of the lower flange (8) is provided with two dovetail grooves for fixing the sealing assembly (15). The opening position of the dovetail grooves avoids the sealing line and leakage hole of the core pressure vessel flange. The stop height of the lower flange (8) is set to be less than the boss height of the main bolt hole of the reactor core pressure vessel, so as to ensure that the primary loop vacuum device and the flange sealing surface of the reactor core pressure vessel achieve soft contact sealing through the sealing assembly (15).

4. The primary loop vacuum pumping device in the reseating state of the upper internal components according to claim 1, characterized in that, The exhaust assembly (3) includes at least one set of stainless steel pipes, and at least two sets of ball valves are connected in series on each set of stainless steel pipes; in the non-working state, the ball valves are in the closed state to ensure the sealing of the primary loop vacuum device; the stainless steel pipes are connected to the inner cavity of the vacuum cylinder; the interface of the stainless steel pipes is in the form of a quick connector, which is used to connect the core water level gauge and the external vacuum platform through a hose to perform vacuuming of the primary loop.

5. The primary loop vacuum pumping device in the reseating state of the upper internal components according to claim 1, characterized in that, The lifting lug (1) is welded to the upper cover (4) via a support plate (2); there are 4 support plates (2), which are evenly distributed around the upper cover (4) and the lifting lug (1) is located in the middle of the 4 support plates (2).

6. The primary loop vacuum pumping device in the reseating state of the upper reactor internal components according to claim 1, characterized in that, The upper cover (4), the upper cylinder (5), and the lower cylinder (6) are all made of stainless steel. The upper cover (4), the upper cylinder (5), the lower cylinder (6), and the lower flange (8) are all fixedly connected by welding to form an integrated sealed cavity structure, which does not require on-site assembly. The internal height of the vacuum cylinder is designed to accommodate the upper in-core components and the control rod drive rod on top of them that are seated in the reactor core pressure vessel, and to maintain a preset safe distance from the head of the control rod drive rod.

7. The primary loop vacuum pumping device in the reseating state of the upper reactor internal components according to claim 1, characterized in that, It also includes a ladder (9), which is fixedly installed on the outer wall of the vacuum cylinder to facilitate the maintenance and inspection of the primary vacuum device by the staff.

8. The primary loop vacuum pumping device in the reseating state of the upper internal components according to any one of claims 1-7, characterized in that, It also includes a tray (10), which is a square plate structure with a circular recessed plane in the center for accommodating the lower part of the primary vacuum device, and guide blocks (11) and pads (13) are evenly distributed around it. The pad (13) is detachable. By removing and installing the pad (13), the tray (10) can be adapted to the transportation, hoisting, storage or testing conditions of the primary loop vacuum device. When storing or transporting the primary loop vacuum device, the pad (13) is installed to provide stable support. When testing the primary loop vacuum device, the pad (13) is removed so that the primary loop vacuum device sits in the circular concave plane of the tray (10) to simulate the support state of the core pressure vessel flange. The guide block (11) and the pad (13) are fixed to the tray (10) by the pressure plate (12) and bolts; the four corners of the tray (10) are evenly distributed with lifting rings (14).

9. A method for evacuating the primary loop under the reseating state of upper reactor internal components, characterized in that, Using the primary loop vacuum pumping device described in any one of claims 1-8 under the reseating state of the upper in-core components, performing primary loop vacuum pumping under dry conditions with no water in the reactor core includes the following steps: Connect the external hoisting equipment to the lifting lug (1) of the primary loop vacuum device; hoist the primary loop vacuum device to the top of the reactor core, so that the guide plate (7) is aligned with the guide column inside the reactor core pressure vessel; Through the cooperation of the guide plate (7) and the guide column in the core pressure vessel, the primary loop vacuum device is guided to sit on the flange surface of the core pressure vessel along the guide column in the core pressure vessel; after the primary loop vacuum device is seated, the self-weight of the primary loop vacuum device compresses the sealing component (15), forming initial contact stress, and realizing the initial seal between the primary loop vacuum device and the flange surface of the core pressure vessel. Connect the exhaust assembly (3) to the external vacuum platform, start the vacuum platform, and extract the gas from the inner cavity of the vacuum cylinder and the primary loop connected to it until the required vacuum level is reached; during this process, the vacuum pressure and the initial contact stress are superimposed to achieve further sealing between the primary loop vacuum device and the flange of the reactor core pressure vessel.

10. A method for evacuating the primary loop under the reseating state of upper reactor internal components, characterized in that, Using the primary loop vacuum pumping device described in any one of claims 1-8 under the reseating state of the upper in-core components, performing primary loop vacuum pumping under wet conditions where the reactor core contains water includes the following steps: Connect the external hoisting equipment to the lifting lug (1) of the primary loop vacuum device; hoist the primary loop vacuum device to the top of the reactor core, so that the guide plate (7) is aligned with the guide column inside the reactor core pressure vessel; Before the primary vacuum device comes into contact with the water surface, the ball valve on the exhaust assembly (3) is remotely opened using a long-handled tool; Through the cooperation of the guide plate (7) and the guide column inside the reactor core pressure vessel, the primary loop vacuum pumping device is guided to sit on the flange surface of the reactor core pressure vessel along the guide column inside the reactor core pressure vessel; during the sitting process of the primary loop vacuum pumping device, the gas in the inner cavity of the vacuum pumping cylinder is compressed and discharged through the opened ball valve, while water begins to enter the inner cavity of the vacuum pumping cylinder; after the primary loop vacuum pumping device is seated, the self-weight of the primary loop vacuum pumping device compresses the sealing assembly (15), forming initial contact stress, and realizing the initial seal between the primary loop vacuum pumping device and the flange surface of the reactor core pressure vessel. After the primary vacuum device is fully seated and stable, use a long-handled tool to remotely close all ball valves. At this time, the inner cavity of the vacuum cylinder is filled with water and is in a sealed state. Connect the exhaust assembly (3) to the external vacuuming platform, start the vacuuming platform, and extract the water and gas in the inner cavity of the vacuuming cylinder and the primary loop connected to it until the required vacuum level is reached; during this process, the vacuuming pressure and the initial contact stress are superimposed to achieve further sealing between the primary loop vacuuming device and the core pressure vessel flange.

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