CN215949597U

CN215949597U - Steam inlet system of low-pressure cylinder of nuclear power station

Info

Publication number: CN215949597U
Application number: CN202121421933.XU
Authority: CN
Inventors: 徐应军; 吴孟雄; 魏恒
Original assignee: China General Nuclear Power Corp; CGN Power Co Ltd; Daya Bay Nuclear Power Operations and Management Co Ltd; Lingdong Nuclear Power Co Ltd; Guangdong Nuclear Power Joint Venture Co Ltd; Lingao Nuclear Power Co Ltd
Current assignee: China General Nuclear Power Corp; CGN Power Co Ltd; Daya Bay Nuclear Power Operations and Management Co Ltd; Lingdong Nuclear Power Co Ltd; Guangdong Nuclear Power Joint Venture Co Ltd; Lingao Nuclear Power Co Ltd
Priority date: 2021-06-24
Filing date: 2021-06-24
Publication date: 2022-03-04
Anticipated expiration: 2031-06-24

Abstract

The utility model belongs to the technical field of steam turbines of nuclear power plants, and particularly relates to a low-pressure cylinder steam inlet system of a nuclear power plant. The low-pressure cylinder steam inlet system of the nuclear power station comprises a steam turbine low-pressure cylinder, a steam inlet pipeline, a waveform expansion joint and a plugging shield; the low-pressure cylinder of the steam turbine comprises a low-pressure outer cylinder and a low-pressure inner cylinder arranged in the low-pressure outer cylinder; the waveform expansion joint comprises an expansion joint, an inner flange and an outer flange sleeved on the inner flange; one end of the inner flange is connected with a steam inlet pipeline, and the other end of the inner flange is connected with a low-pressure inner cylinder; one end of the outer flange is hermetically connected with the plugging protective cover, and the other end of the outer flange is connected with the low-pressure outer cylinder; one end of the plugging protective cover far away from the outer flange is hermetically connected with the outer wall of the steam inlet pipeline. According to the utility model, the blocking shield is hermetically connected between the upper surface of the outer flange and the outer wall of the steam inlet pipeline, so that the negative pressure environment in the low-pressure outer cylinder is maintained, and the accidents of shutdown and shutdown caused by the deterioration of the negative pressure environment in the low-pressure outer cylinder are avoided.

Description

Steam inlet system of low-pressure cylinder of nuclear power station

Technical Field

The utility model belongs to the technical field of steam turbines of nuclear power plants, and particularly relates to a low-pressure cylinder steam inlet system of a nuclear power plant.

Background

The steam turbine is used as a core component of power generation equipment of the nuclear power station, and after the steam is expanded primarily in a high-pressure cylinder of the steam turbine to do work, the steam enters a low-pressure cylinder of the steam turbine to continue to expand to do work, so that the function of power generation is completed. The low-pressure cylinder comprises an inner cylinder and an outer cylinder, and the outer cylinder is mainly used for the functions of steam exhaust and flow guide, inner cylinder support and steam output of the low-pressure cylinder; the inner tub is installed inside the outer tub, and mainly plays a role of introducing steam. Hot steam output by a steam-water separation reheater of the nuclear power station enters an inner cylinder of a low-pressure cylinder through a low-pressure cylinder communicating pipe, after the hot steam is expanded by blades in the inner cylinder to do work, most of the hot steam is discharged into a condenser through a steam discharge guide pipe of an outer cylinder.

Since the inner and outer cylinders are in operation, relative movement occurs between the inner and outer cylinders, and the connection between the inner and outer cylinders is made by a wave shaped expansion joint which allows for expansion displacement of the inner cylinder relative to the outer cylinder. However, in the long-term use process of the low-pressure cylinder, the waveform expansion joint is difficult to avoid the accident of leakage; and because the wave-shaped expansion joint is arranged in the low-pressure cylinder, the leakage point is difficult to block.

Disclosure of Invention

The utility model provides a low-pressure cylinder steam inlet system of a nuclear power station, aiming at the problems of plugging of a leakage point of a waveform expansion joint and the like in the long-term use process of a low-pressure cylinder in the prior art.

In view of the above technical problems, an embodiment of the present invention provides a steam inlet system for a low pressure cylinder of a nuclear power station, including a low pressure cylinder of a steam turbine, a steam inlet pipeline, a waveform expansion joint and a plugging shield; the low-pressure cylinder of the steam turbine comprises a low-pressure outer cylinder and a low-pressure inner cylinder arranged in the low-pressure outer cylinder;

the wave-shaped expansion joint comprises an expansion joint, an inner flange and an outer flange; the outer flange is sleeved on the outer side wall of the expansion joint; the inner flange is arranged in the expansion joint and connected with the inner side wall of the expansion joint, and the inner flange and the outer flange are coaxially arranged; one end of the inner flange is connected with the steam inlet pipeline, and the other end of the inner flange is connected with the low-pressure inner cylinder; one end of the outer flange is hermetically connected with the plugging protective cover, and the other end of the outer flange is connected with the low-pressure outer cylinder; and one end of the plugging protective cover, which is far away from the outer flange, is hermetically connected with the outer wall of the steam inlet pipeline.

Optionally, the blocking shield comprises an annular vertical plate and an annular sealing plate connected to the annular vertical plate; one end of the annular vertical plate, which is far away from the annular sealing plate, is provided with an annular flange, and the annular vertical plate is connected with the outer flange through the annular flange; the annular sealing plate is connected with the outer wall of the steam inlet pipeline in a sealing mode.

Optionally, the steam inlet system of the low-pressure cylinder of the nuclear power plant further comprises a first bolt and a first mounting flange mounted on the low-pressure outer cylinder; the outer flange is provided with a first mounting hole, and the first mounting flange is provided with a second mounting hole; the nut of the first bolt is abutted against the outer flange, and the screw of the first bolt penetrates through the first mounting hole and is inserted into the second mounting hole;

the annular flanging is provided with a third mounting hole, the low-pressure cylinder steam inlet system of the nuclear power station further comprises a fastening nut, and the fastening nut is provided with a threaded through hole and a containing hole communicated with the threaded through hole; the nut of the first bolt penetrates through the third mounting hole and extends into the accommodating hole, the first bolt is far away from the screw rod of the first mounting flange and is in threaded connection with the threaded through hole, and the annular flanging is tightly pressed on the outer flange through the fastening nut.

Optionally, the containment shield comprises a first semicircular shield and a second semicircular shield connected to the first semicircular shield.

Optionally, the steam inlet system of the low-pressure cylinder of the nuclear power plant further comprises a first sealing member arranged between the plugging shield and the outer flange.

Optionally, the steam inlet system of the low-pressure cylinder of the nuclear power plant further comprises a sealing assembly, and one end, far away from the outer flange, of the blocking shield is in sealing connection with the outer wall of the steam inlet pipeline through the sealing assembly.

Optionally, the sealing assembly comprises a sealing tape, a piece of tinfoil paper and a sealing glue arranged between the plugging shield and the steam inlet pipeline; the tin foil paper is connected to the outer walls of the blocking shield and the steam inlet pipeline; the sealing adhesive tape is connected with the tinfoil paper, the plugging protective cover and the outer wall of the steam inlet pipeline.

Optionally, the occlusion shield is provided with a suspension loop.

Optionally, the steam inlet system of the low-pressure cylinder of the nuclear power plant further comprises a second bolt, a second mounting flange mounted on the low-pressure inner cylinder, and a third mounting flange mounted on the steam inlet pipeline; the mounting structure is characterized in that a fourth mounting hole is formed in the third mounting flange, a fifth mounting hole is formed in the inner flange, a sixth mounting hole is formed in the second mounting flange, one end of a second bolt is abutted to the third mounting flange, and the other end of the second bolt sequentially penetrates through the fourth mounting hole, the fifth mounting hole and is inserted into the sixth mounting hole.

Optionally, an expansion gap is provided between the second bolt and the inner wall of the blocking shield.

In the utility model, the waveform expansion joint comprises an expansion joint, an inner flange and an outer flange; the outer flange is sleeved on the outer side wall of the expansion joint; the inner flange is arranged in the expansion joint and connected with the inner side wall of the expansion joint, and the inner flange and the outer flange are coaxially arranged; one end of the inner flange is connected with the steam inlet pipeline, and the other end of the inner flange is connected with the low-pressure inner cylinder; one end of the outer flange is hermetically connected with the plugging protective cover, and the other end of the outer flange is connected with the low-pressure outer cylinder; and one end of the plugging protective cover, which is far away from the outer flange, is hermetically connected with the outer wall of the steam inlet pipeline. When the low-pressure inner cylinder performs expansion motion relative to the low-pressure outer cylinder for a long time, the expansion joint leaks, the plugging protective cover is connected between the upper surface of the outer flange and the outer wall of the steam inlet pipeline in a sealing mode, namely the plugging protective cover is used for plugging a leakage hole in the expansion joint, so that the negative pressure environment in the low-pressure outer cylinder is maintained (the low-pressure outer cylinder is communicated with a condenser of a nuclear power station, and the negative pressure environment is also the negative pressure environment of the condenser), and the accidents of shutdown and shutdown caused by the deterioration of the negative pressure environment in the low-pressure outer cylinder are avoided. And the plugging protective cover seals and plugs the waveform expansion joint from the outside, so that the plugging protective cover is convenient to mount.

Drawings

The utility model is further illustrated with reference to the following figures and examples.

FIG. 1 is a schematic diagram of a low-pressure cylinder steam inlet system of a nuclear power plant according to an embodiment of the utility model;

fig. 2 is a front view of an annular flange of the plugging shield according to an embodiment of the present invention;

FIG. 3 is a front view of a fastening nut provided in accordance with one embodiment of the present invention;

fig. 4 is a side view of a fastening nut provided in accordance with an embodiment of the present invention.

The reference numerals in the specification are as follows:

1. a low-pressure cylinder of the steam turbine; 11. a low pressure outer cylinder; 111. a first mounting flange; 12. a low-pressure inner cylinder; 121. A second mounting flange; 2. an inlet steam line; 21. a third mounting flange; 3. a wave-shaped expansion joint; 31. an expansion joint; 32. an inner flange; 33. an outer flange; 4. plugging the protective cover; 41. annular flanging; 5. a first bolt; 6. a second bolt; 7. a seal assembly; 8. fastening a nut; 81. a threaded through hole, 82, a receiving hole; A. an axis of symmetry.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and are not intended to limit the utility model.

It is to be understood that the terms "upper", "lower", "left", "right", "front", "rear", "middle", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be construed as limiting the present invention.

As shown in fig. 1, the steam inlet system of the low pressure cylinder of the nuclear power plant according to an embodiment of the present invention includes a steam turbine low pressure cylinder 1, a steam inlet pipeline 2, a corrugated expansion joint 3, and a blocking shield 4; the steam turbine low-pressure cylinder 1 comprises a low-pressure outer cylinder 11 and a low-pressure inner cylinder 12 installed in the low-pressure outer cylinder 11; it is understood that the low pressure inner cylinder 12 is located inside the low pressure outer cylinder 11, and the low pressure outer cylinder 11 may function to support the low pressure inner cylinder 12; further, the low-pressure inner cylinder 12 is communicated with the low-pressure outer cylinder 11, and a negative pressure environment is formed in the low-pressure outer cylinder 11 (since the low-pressure outer cylinder 11 is communicated with a condenser of a nuclear power plant, the negative pressure environment is also the negative pressure environment of the condenser). Specifically, one end of the steam inlet pipeline 2, which is far away from the inner flange 32, is communicated with a steam-liquid separation regenerator, and an outlet of the low-pressure outer cylinder 11 is communicated with a condenser; therefore, the steam output by the gas-liquid separation regenerator enters the low-pressure inner cylinder 12 through the steam inlet pipeline 2, and after performing expansion work in the low-pressure inner cylinder 12, the steam passes through the low-pressure outer cylinder 11 and is input into the condenser.

The wave-shaped expansion joint 3 comprises an expansion joint 31, an inner flange 32 and an outer flange 33; the outer flange 33 is sleeved on the outer side wall of the expansion joint 31; the inner flange 32 is installed in the expansion joint 31 and connected with the inner side wall of the expansion joint 31, and the inner flange 32 and the outer flange 33 are coaxially arranged; one end of the inner flange 32 is connected with the steam inlet pipeline 2, and the other end of the inner flange 32 is connected with the low-pressure inner cylinder 12; one end of the outer flange 33 is hermetically connected with the blocking shield 4, and the other end of the outer flange 33 is connected with the low-pressure outer cylinder 11; one end of the blocking shield 4 far away from the outer flange 33 is connected with the outer wall of the steam inlet pipeline 2 in a sealing way. It is understood that the upper surface of the inner flange 32 is connected to the steam inlet pipe 2, the lower surface of the inner flange 32 is connected to the low-pressure inner cylinder 12, the lower surface of the outer flange 33 is connected to the low-pressure outer cylinder 11, and the upper surface of the outer flange 33 is connected to the blocking shield 4.

In the utility model, the wave-shaped expansion joint 3 comprises an expansion joint 31, an inner flange 32 and an outer flange 33; the outer flange 33 is sleeved on the outer side wall of the expansion joint 31; the inner flange 32 is installed in the expansion joint 31 and connected with the inner side wall of the expansion joint 31, and the inner flange 32 and the outer flange 33 are coaxially arranged; one end of the inner flange 32 is connected with the steam inlet pipeline 2, and the other end of the inner flange 32 is connected with the low-pressure inner cylinder 12; one end of the outer flange 33 is hermetically connected with the blocking shield 4, and the other end of the outer flange 33 is connected with the low-pressure outer cylinder 11; one end of the blocking shield 4 far away from the outer flange 33 is connected with the outer wall of the steam inlet pipeline 2 in a sealing way. When the low-pressure inner cylinder 12 expands and moves relative to the low-pressure outer cylinder 11 for a long time, the expansion joint 31 leaks, and the blocking and protecting cover 4 is connected between the upper surface of the outer flange 33 and the outer wall of the steam inlet pipeline 2 in a sealing manner, that is, the blocking and protecting cover 4 blocks the leakage hole on the expansion joint 31, so that the negative pressure environment in the low-pressure outer cylinder 11 is maintained, and the accidents of shutdown and pile stopping caused by the deterioration of the negative pressure environment in the low-pressure outer cylinder 11 are avoided. The plugging cover 4 seals and plugs the corrugated expansion joint 3 from the outside, and facilitates the installation of the plugging cover 4.

In one embodiment, as shown in fig. 1 and 2, the plugging shroud 4 comprises an annular riser and an annular tear strip attached to the annular riser; one end of the annular vertical plate, which is far away from the annular sealing plate, is provided with an annular flange 41, and the annular vertical plate is connected with the outer flange 33 through the annular flange 41; the annular sealing plate is connected with the outer wall of the steam inlet pipeline 2 in a sealing mode. Preferably, the annular vertical plate and the annular sealing plate are of an integrally formed structure. Specifically, the annular sealing plate is bent toward the inside of the annular vertical plate, and the annular flange 41 is bent toward the outside of the annular vertical plate. In this embodiment, the plugging shield 4 has a simple structure, low manufacturing cost and convenient installation.

In one embodiment, as shown in fig. 1, the steam inlet system of the low-pressure cylinder of the nuclear power plant further comprises a first bolt 5 and a first mounting flange 111 mounted on the low-pressure outer cylinder 11; a first mounting hole is formed in the outer flange 33, and a second mounting hole is formed in the first mounting flange 111; the nut of the first bolt 5 abuts against the outer flange 33, and the screw of the first bolt passes through the first mounting hole and is inserted into the second mounting hole; it is to be understood that the first and second mounting holes are threaded through holes. Specifically, the nut of the first bolt 5 abuts against the outer flange 33, and the screw rod below the first bolt 5 passes through the first mounting hole and then is in threaded connection with the second mounting hole; that is, the first bolts 5 connect the outer flange 33 to the first mounting flange 111. Illustratively, the first bolt comprises a nut and a screw, the screw is mounted on the nut, and two ends of the screw extend out of the nut.

As shown in fig. 3 and 4, a third mounting hole is formed in the annular flange 41, the steam inlet system of the low-pressure cylinder of the nuclear power station further includes a fastening nut 8, and a threaded through hole 81 and a receiving hole 82 communicated with the threaded through hole 81 are formed in the fastening nut 8; the nut of the first bolt 5 passes through the third mounting hole and extends into the receiving hole 82, the screw rod of the first bolt far away from the first mounting flange is in threaded connection with the threaded through hole 81, and the fastening nut 8 presses the annular flange 41 onto the outer flange 33. As can be understood, the nut of the first bolt 5 abuts against the outer flange 33, and after the nut of the first bolt 5 passes through the third mounting hole of the annular flange 41, the nut is in threaded connection with the threaded through hole 81 of the fastening nut 8 (that is, the screw above the bolt is in threaded connection with the threaded through hole 81 of the fastening nut 8); that is, the fastening nut is screw-coupled to the screw above the first bolt 8 and presses the annular flange 41 against the upper surface of the outer flange 33. In this embodiment, the first bolt 5 does not need to be detached, and the plugging protection cover 4 can be installed on the outer flange 33, so that the installation convenience of the plugging protection cover 4 is further improved.

In one embodiment, as shown in fig. 1, the containment shield 4 comprises a first semicircular shield and a second semicircular shield connected to the first semicircular shield. It can be understood that the plugging shield 4 is divided into a first semicircular shield and a second semicircular shield, and the plugging shield 4 is conveniently sleeved on the steam inlet pipeline. Specifically, after the first semicircular shield and the second semicircular shield are respectively sleeved on the steam inlet pipeline 2 from two sides, the first semicircular shield and the second semicircular shield are connected through processes such as welding, screw connection and the like; that is, the installation of the plugging shroud 4 can be completed without disassembling the steam inlet pipe 2.

In an embodiment, as shown in fig. 1, the steam inlet system of the low-pressure cylinder of the nuclear power plant further includes a first sealing member (not shown) disposed between the plugging shroud 4 and the outer flange 33. It will be appreciated that the first seal seals the junction of the outer flange 33 and the annular flange 41, preventing leakage from the junction of the outer flange 33 and the annular flange 41 inside the containment shield 4; and the first sealing element includes, but is not limited to, a high temperature resistant sealant, a sealing rubber strip, etc.

In an embodiment, as shown in fig. 1, the steam inlet system of the low-pressure cylinder of the nuclear power plant further comprises a sealing assembly 7, and one end of the plugging shield 4, which is far away from the outer flange 33, is in sealing connection with the outer wall of the steam inlet pipeline 2 through the sealing assembly 7. Preferably, the sealing assembly 7 comprises a sealing tape, a tin foil and a sealing glue arranged between the plugging shield 4 and the steam inlet pipeline 2; the tin foil paper is connected to the outer walls of the blocking shield 4 and the steam inlet pipeline 2; the sealing adhesive tape is connected with the tinfoil paper, the blocking protective cover 4 and the outer wall of the steam inlet pipeline 2. Specifically, after the sealant is coated on the outer wall of the steam inlet pipeline 2, the plugging shield 4 is sleeved on the steam inlet pipeline 2, the annular flange 41 of the plugging shield 4 is in sealed connection with the outer flange 33 through the first sealing element, and the annular sealing plate of the plugging shield 4 is in sealed connection with the outer wall of the steam inlet pipeline 2 through the sealant; wrapping the outer walls of the blocking shield 4 and the steam inlet pipeline 2 with the tinfoil paper, wherein the tinfoil paper is required to wrap the joint of the outer wall of the steam inlet pipeline 2 and the annular sealing plate; and finally, adhering the tin foil paper to the blocking shield 4 and the steam inlet pipeline 2 by using the sealing adhesive tape, wherein the sealing adhesive tape is required to wrap the joint of the outer wall of the steam inlet pipeline 2 and the annular sealing plate. In this embodiment, a multilayer sealing structure is provided between the plugging shield 4 and the outer wall of the steam inlet pipeline 2, so that the sealing performance of the plugging shield 4 is further ensured. Moreover, the tin foil paper can isolate the temperature of the steam inlet pipeline 2, so that the viscosity of the sealing adhesive tape is ensured.

Further, the lower end of the blocking shield 4 is hard-connected with the outer flange 33 by the fastening nut 8 and sealed by a first sealing member disposed between the first mounting flange 111 and the outer flange 33; this first seal can absorb vibrations, displacements, etc. occurring in the low-pressure outer cylinder 11. The upper end of the blocking shield 4 is in flexible connection with the outer wall of the steam inlet pipeline 2 through a sealing assembly 7, and the sealing assembly 7 can absorb vibration, displacement and the like of the low-pressure inner cylinder 12; the sealing cover 4 has good sealing performance.

In one embodiment, the occlusion shield 4 is provided with a lug (not shown). It can understand, the hangers sets up on the surface of annular sealing plate, just first semicircle guard shield with all be equipped with on the second semicircle guard shield the hangers, in this embodiment, the design of hangers has promoted the convenient degree of this shutoff guard shield 4 of taking.

In one embodiment, as shown in fig. 1, the low-pressure cylinder steam inlet system of the nuclear power plant further comprises a second bolt 6, a second mounting flange 121 mounted on the low-pressure inner cylinder 12, and a third mounting flange 21 mounted on the steam inlet pipeline 2; the third mounting flange 21 is provided with a fourth mounting hole, the inner flange 32 is provided with a fifth mounting hole, the second mounting flange 121 is provided with a sixth mounting hole, one end of the second bolt 6 is abutted to the third mounting flange 21, and the other end of the second bolt 6 sequentially penetrates through the fourth mounting hole, the fifth mounting hole and is inserted into the sixth mounting hole. Preferably, the fourth mounting hole, the fifth mounting hole and the sixth mounting hole are all threaded through holes. In this embodiment, the steam inlet pipeline 2 and the low-pressure inner cylinder 12 can be connected to two opposite sides of the inner flange 32 through the second bolt 6, so that the installation convenience of the low-pressure cylinder steam inlet system of the nuclear power station is improved.

In one embodiment, as shown in fig. 1, an expansion gap is provided between the second bolt 6 and the inner wall of the plugging shield 4. The height of the expansion gap is 0.4mm to 1.0mm (e.g., 0.4mm, 0.6mm, 0.8mm, 1.0mm, etc.), and it is understood that the expansion gap does not prevent the low pressure inner cylinder 12 from expanding. When a large negative pressure occurs in the blocking shield 4, the annular sealing plate is connected to the first bolt 5 in a low position due to the negative pressure, so that the blocking shield 4 is restricted from further deformation, and the strength and the sealing performance of the blocking shield 4 are ensured.

The above description is only an example of the steam inlet system of the low pressure cylinder of the nuclear power plant, and should not be construed as limiting the present invention, and any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-pressure cylinder steam inlet system of a nuclear power station is characterized by comprising a steam turbine low-pressure cylinder, a steam inlet pipeline, a waveform expansion joint and a plugging shield; the low-pressure cylinder of the steam turbine comprises a low-pressure outer cylinder and a low-pressure inner cylinder arranged in the low-pressure outer cylinder;

2. The steam inlet system of the nuclear power plant low pressure cylinder according to claim 1, wherein the plugging shield comprises an annular vertical plate and an annular sealing plate connected to the annular vertical plate; one end of the annular vertical plate, which is far away from the annular sealing plate, is provided with an annular flange, and the annular vertical plate is connected with the outer flange through the annular flange; the annular sealing plate is connected with the outer wall of the steam inlet pipeline in a sealing mode.

3. The nuclear power plant low pressure cylinder steam admission system of claim 2 further comprising a first bolt and a first mounting flange mounted on the low pressure outer cylinder; the outer flange is provided with a first mounting hole, and the first mounting flange is provided with a second mounting hole; the nut of the first bolt is abutted against the outer flange, and the screw of the first bolt penetrates through the first mounting hole and is inserted into the second mounting hole;

4. The nuclear power plant low pressure cylinder steam admission system of claim 1, wherein the containment shield comprises a first semicircular shield and a second semicircular shield connected to the first semicircular shield.

5. The nuclear power plant low pressure cylinder steam admission system of claim 1, further comprising a first seal disposed between the containment shroud and the outer flange.

6. The steam inlet system of the nuclear power plant low-pressure cylinder as claimed in claim 1, further comprising a sealing assembly, wherein one end of the blocking shield, which is far away from the outer flange, is connected with the outer wall of the steam inlet pipeline in a sealing mode through the sealing assembly.

7. The steam inlet system of the nuclear power plant low pressure cylinder as claimed in claim 6, wherein the sealing assembly comprises a sealing tape, a tin foil and a sealant disposed between the plugging shield and the steam inlet pipe; the tin foil paper is connected to the outer walls of the blocking shield and the steam inlet pipeline; the sealing adhesive tape is connected with the tinfoil paper, the plugging protective cover and the outer wall of the steam inlet pipeline.

8. The system of claim 1, wherein the plugging shield is provided with a lug.

9. The nuclear power plant low pressure cylinder steam admission system of claim 1, further comprising a second bolt, a second mounting flange mounted on the low pressure inner cylinder, and a third mounting flange mounted on the steam admission line; the mounting structure is characterized in that a fourth mounting hole is formed in the third mounting flange, a fifth mounting hole is formed in the inner flange, a sixth mounting hole is formed in the second mounting flange, one end of a second bolt is abutted to the third mounting flange, and the other end of the second bolt sequentially penetrates through the fourth mounting hole, the fifth mounting hole and is inserted into the sixth mounting hole.

10. The nuclear power plant low pressure cylinder steam admission system of claim 9, wherein an expansion gap is provided between the second bolt and the inner wall of the containment shield.