Double-layer pipeline structure for discharging liquid effluent of nuclear power plant

Abstract

The utility model discloses a nuclear power plant liquid effluent discharge double-layer pipeline structure which comprises an inner-layer pipeline spliced in the length direction, an outer-layer pipeline spliced in the length direction and an outer pipe connecting piece arranged on the outer-layer pipeline, and an anti-corrosion coating is arranged on the inner wall of the outer-layer pipeline. And the two adjacent outer-layer pipelines are welded and connected through the two adjacent outer pipe connecting pieces after being spliced. By adopting the outer pipe connecting piece as a welding transition structure, direct welding operation on the outer layer pipeline body is avoided, so that the integrity of the inner wall anti-corrosion coating is protected. Welding heat mainly acts on the outer pipe connecting piece instead of the outer-layer pipeline body, and the risk that the anti-corrosion coating is damaged by heat is remarkably reduced. Meanwhile, the inner-layer pipeline is of a splicing structure and can be installed and maintained in a segmented mode, the sealing performance and the anti-pressure capacity of the whole structure are further improved through splicing and welding of the outer-layer pipeline, and the safety of radioactive liquid conveying is guaranteed through a double-protection mechanism.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nuclear waste water discharge, in particular to a connecting structure of a double-layer pipeline for liquid effluent discharge of a nuclear power plant. BACKGROUND

[0002] A large amount of liquid effluent containing trace amounts of radioactive substances is generated during the operation of a nuclear power plant. In order to ensure environmental safety, these liquid effluents need to be discharged after treatment. At present, the discharge pipeline of the liquid effluent of the nuclear power plant is mostly single-layer structure, which is prone to corrosion, leakage and other problems during long-term use, which not only affects the discharge effect, but also may cause environmental pollution. A small number of discharge pipelines are double-layer structure, and the outer pipeline is prone to damage to the anticorrosive coating of the inner wall of the outer pipeline during welding, further causing corrosion, leakage and other problems of the outer pipeline. With the development of new energy law, the state has gradually invested more resources to develop and build nuclear power plants, so it is urgent to develop a connection method and structure for the liquid effluent discharge pipeline of the nuclear power plant. SUMMARY

[0003] In order to solve the above problems, the present application provides a connecting structure of a double-layer pipeline for liquid effluent discharge of a nuclear power plant.

[0004] The present application provides a connecting structure of a double-layer pipeline for liquid effluent discharge of a nuclear power plant and a preparation method thereof, which adopts the following scheme:

[0005] A double-layer pipeline structure for liquid effluent discharge of a nuclear power plant, comprising an inner pipeline spliced in the length direction, an outer pipeline spliced in the length direction, and an outer pipe connecting piece arranged on the outer pipeline, an anticorrosive coating is arranged on the inner wall of the outer pipeline, and the adjacent two outer pipelines are spliced and welded by the adjacent two outer pipe connecting pieces.

[0006] Through the above technical scheme, by adopting the outer pipe connecting piece as a transition structure for welding, the integrity of the inner wall anticorrosive coating is protected by avoiding direct welding operation on the outer pipeline body. The welding heat mainly acts on the outer pipe connecting piece rather than the outer pipeline body, which significantly reduces the risk of heat damage to the anticorrosive coating. At the same time, the inner pipeline adopts a splicing structure, which can be installed and maintained in sections, and the splicing and welding of the outer pipeline further improves the sealing performance and pressure resistance of the overall structure, and the double protection mechanism ensures the safety of radioactive liquid transportation.

[0007] As a preferred embodiment of the present application, the outer pipe connecting piece is a protective sleeve, the protective sleeve is connected with the outer pipeline, and the adjacent two protective sleeves are connected by welding when the adjacent two outer pipelines are spliced.

[0008] By the technical scheme, the protection sleeve is used as the outer pipe connecting piece to realize precise heat isolation in the outer pipeline welding process. The protection sleeve is pre-welded and fixed with the outer pipeline, and heat is concentrated in the butt joint area between the protection sleeves during welding, so that the outer pipeline body is prevented from being heated to cause carbonization failure of the anticorrosive coating. The girth welding process of the protection sleeve forms a continuous sealing weld, which not only guarantees the connecting strength, but also reduces the temperature rise of the inner wall of the outer pipeline through physical isolation. The design controls the heat affected zone of the anticorrosive coating within a safety threshold while guaranteeing the structural strength, and significantly prolongs the corrosion resistance life of the outer pipeline.

[0009] As a preferred embodiment of the present application, the protection sleeve comprises a sleeve part coaxially arranged with the outer pipeline and a shaft end part connected with the sleeve part, the shaft end part is fixedly connected with the outer pipeline, and a cavity is formed between the protection sleeve and the outer pipeline, and the cavity is filled with an anticorrosive material layer.

[0010] Through the technical scheme, the anticorrosive material (such as epoxy resin) filled in the cavity can permeate into the tiny gap between the outer pipeline and the protection sleeve to form a chemical bonding layer, thereby preventing external corrosive media from invading through the heat affected zone of the weld. At the same time, the thermal expansion coefficient of the filling material matches that of the metal pipeline, which can buffer the stress caused by temperature change and prevent the protection sleeve weld from cracking. The design further improves the penetration resistance and corrosion resistance of the weld area through the synergistic effect of "mechanical isolation + chemical protection".

[0011] As a preferred embodiment of the present application, the inner pipeline is made of HDPE material, and two adjacent inner pipelines are connected through an electric heating fusion ring.

[0012] Through the technical scheme, the HDPE material inner pipeline combined with the electric heating fusion ring connection technology realizes zero-leakage sealing of the radioactive liquid conveying pipeline. The HDPE material has excellent radiation resistance and chemical corrosion resistance, and the electric heating fusion ring melts and fuses the end faces of adjacent pipelines through resistance heating to form a seamless connection at the molecular level. The sealing performance of the electric heating fusion connection is more than 3 times higher than that of mechanical connection, and is particularly suitable for harsh working conditions that long-term bear radioactive liquid erosion.

[0013] As a preferred embodiment of the present application, the outer pipe connecting piece is a connecting flange, the connecting flange is connected with the outer pipeline, and when two adjacent outer pipelines are spliced, the connecting flanges of the two adjacent outer pipelines are locked through bolts, and are welded.

[0014] Through the technical scheme, the mechanical sealing of the flange is realized through the bolt pre-tightening force to complete the preliminary positioning of the pipeline; and then the girth welding is performed to form a secondary sealing barrier. The bolt connection can compensate for the installation deviation of the pipeline, and the welding eliminates the possible micro gap at the flange interface.

[0015] As a preferred embodiment of the present application, a support frame roller assembly is further arranged between the inner layer pipeline and the outer layer pipeline.

[0016] Through the above technical solution, the support frame roller assembly forms a slidable support point on the outer wall of the inner layer pipeline, allowing the outer layer pipeline to move smoothly in the axial direction during installation, avoiding hard friction damage to the corrosion-resistant coating. At the same time, the circumferential uniform distribution design of the roller ensures that the inner and outer layer pipelines maintain precise coaxiality to prevent local stress concentration caused by eccentricity.

[0017] As a preferred embodiment of the present application, the two adjacent outer layer pipelines are connected by a stepped groove butt joint, and the first and second steps on the two adjacent sides of the two outer layer pipelines are arranged to have a gap of less than 0.5 mm.

[0018] Through the above technical solution, the stepped groove butt joint structure realizes high-precision assembly and welding. The cooperation of the first and second steps forms a labyrinth sealing interface, which controls the butt joint gap to be within 0.5 mm, significantly reducing the volume of the welding pool. At the same time, the stepped structure plays a self-positioning role during welding, making the weld formation more uniform.

[0019] The present application also discloses a preparation method of the above-mentioned double-layer pipeline structure for liquid effluent discharge in a nuclear power plant, comprising the following steps:

[0020] Step S1, inner layer pipeline welding: inserting two adjacent inner layer pipelines into an electric heating melting ring, and starting a field electric heating melting device to connect the two adjacent inner layer pipelines into a whole;

[0021] Step S2, outer layer pipeline butt joint: translating and butt joining two adjacent outer layer pipelines through a support frame roller assembly, each outer layer pipeline being welded and connected with an outer pipe connecting piece, and each outer layer pipeline inner wall being provided with a corrosion-resistant coating, and the two outer layer pipelines being butt joined while ensuring that the two adjacent outer pipe connecting pieces are butt joined;

[0022] Step S3, outer layer pipeline fixation: completing the preparation work before welding, starting the welding device, and making the automatic welding machine perform girth welding along the butt joint position of the two adjacent outer pipe connecting pieces, and then cleaning and non-destructive testing after welding.

[0023] Through the above technical solution, the welding strategy of "first inner layer then outer layer, step-by-step isolation" is adopted, the electric heating melting sealing connection of the inner layer HDPE pipeline is first completed to form a leak-free inner lining; the precise positioning of the support frame roller assembly ensures that the outer layer pipeline maintains a uniform gap with the inner layer pipeline during translation and butt joining, avoiding mechanical friction that may scratch the corrosion-resistant coating; the welding operation is limited to the butt joint area of the outer pipe connecting piece, and the heat cannot be completely conducted to the outer layer pipeline body during welding, ensuring that the inner wall corrosion-resistant coating is not thermally degraded.

[0024] As a preferred embodiment of the present application, the outer pipe connector is a protective sleeve, and the automatic welding machine performs circumferential welding along the protective sleeve and the butt joint position of the protective sleeve, and after welding, cleaning and non-destructive testing, the cavity between the two adjacent protective sleeves and the outer layer pipes is filled with anticorrosive material by using a filling device.

[0025] Through the above technical solution, a dynamic anticorrosion barrier is constructed through the synergistic effect of protective sleeve welding and cavity filling. After the circumferential welding of the protective sleeve is completed, the liquid anticorrosive material is uniformly filled into the cavity between the protective sleeve and the outer layer pipe by using a pressure injection process, and a composite protective layer with sealing and flexibility is formed after solidification. A triple protection mechanism is realized: the filling material closely adheres to the metal surface, effectively sealing the micro defects that may occur in the heat affected zone; the elastic material layer absorbs the stress caused by thermal expansion and contraction of the pipe through deformation, avoiding peeling of the coating caused by temperature changes; the filling layer and the original anticorrosive coating form a continuous protective interface, blocking the diffusion path of the corrosive medium. This process significantly improves the permeability and mechanical durability of the pipe connection part, and is particularly suitable for long-term protection needs in the high-humidity and strong-corrosion environment of nuclear power plants.

[0026] As a preferred embodiment of the present application, the outer pipe connector is a connecting flange, the connecting flange is connected with the outer layer pipe, the two adjacent outer layer pipes are fixed, and the two adjacent connecting flanges are locked by bolts and welded.

[0027] Through the above technical solution, through the composite design of flange connection and welding, the flange bolt is used to realize quick pre-tightening positioning, which greatly shortens the pipe centering adjustment time; on the basis of mechanical connection, full penetration welding is performed, forming a redundant sealing structure, which significantly improves the long-term reliability of the pipe system in the complex operating environment of nuclear power plants.

[0028] In summary, the present application has at least one of the following beneficial technical effects:

[0029] 1. The present application constructs a multi-level anticorrosion system of "body protection + structural isolation + active filling". The anticorrosive coating on the inner wall of the outer layer pipe serves as the basic protective layer, and the welding isolation design of the outer pipe connector (protective sleeve / flange) effectively blocks the heat conduction of welding, avoiding the high-temperature failure of the coating; the protective sleeve cavity is filled with anticorrosive material to form a secondary sealing layer, dynamically compensating for the micro gaps caused by temperature deformation or mechanical vibration. Through the synergistic effect of physical isolation, chemical corrosion and dynamic sealing, the system significantly improves the long-term stability of the pipe in a strong corrosive and high radiation environment, and fundamentally solves the problem of corrosion leakage caused by welding damage in traditional double-layer pipes.

[0030] 2, The application adopts inner and outer pipeline step-by-step construction strategy, the inner layer HDPE pipeline realizes molecular level sealing through fusion connection, the outer layer realizes rapid and accurate assembly through prefabricated connecting piece. The support frame roller assembly ensures the inner and outer pipeline centering accuracy, avoids installation damage; the design makes the pipeline system have construction efficiency and operation reliability at the same time, completely meets the strict sealing requirements of nuclear facilities on radioactive medium conveying pipeline. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is an axial cross section schematic view of the nuclear power plant liquid effluent discharge double-layer pipeline structure of the application.

[0032] Figure 2 It is a radial cross section schematic view of the nuclear power plant liquid effluent discharge double-layer pipeline structure of the application.

[0033] Figure 3 It is an outer pipeline cross section schematic view of the nuclear power plant liquid effluent discharge double-layer pipeline structure of the application.

[0034] Figure 4 It is an axial cross section schematic view of the nuclear power plant liquid effluent discharge double-layer pipeline structure of the embodiment 2 of the application.

[0035] The reference signs are explained as follows: 1 first inner layer pipeline; 2, second inner layer pipeline; 3, first outer layer pipeline; 4, second outer layer pipeline; 5, anticorrosive coating; 6, first protective sleeve; 7, second protective sleeve;

[0036] 8, support frame roller assembly; 81, first fixed plate; 82, second fixed plate; 83, pulley; 9, electric heating ring; 10, anticorrosive material layer; 11, second flange plate; 12, first flange plate; 31, first stepped groove; 32, second stepped groove. DETAILED DESCRIPTION

[0037] The application is further explained below in combination with the accompanying Figures 1-4 The application is further explained below in combination with the accompanying

[0038] Embodiment 1:

[0039] The application is further explained below in combination with the accompanying Figure 1 The application is further explained below in combination with the accompanying Figure 3 The embodiment discloses a nuclear power plant liquid effluent discharge double-layer pipeline structure, which comprises a first inner layer pipeline 1, a second inner layer pipeline 2, a first outer layer pipeline 3 and a second outer layer pipeline 4. The first inner layer pipeline 1 and the second inner layer pipeline 2 are made of HDPE, and the first inner layer pipeline 1 and the second inner layer pipeline 2 are connected by an electric heating ring 9 to form an inner layer pipeline for conveying liquid effluent.

[0040] The support frame roller assembly 8 is fixed on the inner wall of the first inner layer pipeline 1, and comprises two half circular ring fixed plates, i.e. a first fixed plate 81 and a second fixed plate 82, and pulleys 83 are fixed on the first fixed plate 81 and the second fixed plate 82. The support frame roller assembly 8 is used for positioning and guiding when the first outer layer pipeline 3 and the second outer layer pipeline 4 are installed.

[0041] The first outer layer pipeline 3 and the second outer layer pipeline 4 are made of carbon steel, and a first step 31 and a second step 32 are respectively arranged on the adjacent sides of the two outer layer pipelines, and the gap between the first step 31 and the second step 32 is less than 0.5 mm. The first outer layer pipeline 3 and the second outer layer pipeline 4 are spliced by the first step 31 and the second step 32 to form the outer layer pipeline, and an anticorrosive coating 5 is arranged on the inner wall of the first outer layer pipeline 3 and the second outer layer pipeline 4.

[0042] The first outer layer pipeline 3 and the second outer layer pipeline 4 are respectively provided with outer pipe connecting pieces for fixed connection. In the embodiment, a first protective sleeve 6 is arranged on the first outer layer pipeline 3, and a second protective sleeve 7 is arranged on the second outer layer pipeline 4. The first protective sleeve 6 and the second protective sleeve 7 are a symmetrical structure, and both include a sleeve part coaxially arranged with the first outer layer pipeline 3 or the second outer layer pipeline 4 and a shaft end part connected with the sleeve part. The shaft end part of the first protective sleeve 6 is welded with the first outer layer pipeline 3 to fix the first protective sleeve 6 on the first outer layer pipeline 3, and the shaft end part of the second protective sleeve 7 is welded with the second outer layer pipeline 4 to fix the second protective sleeve 7 on the second outer layer pipeline 4. After the first outer layer pipeline 3 and the second outer layer pipeline 4 are spliced by the first step 31 and the second step 32, the first protective sleeve 6 abuts against the second protective sleeve 7, and the first protective sleeve 6 and the second protective sleeve 7 are fixed by welding, so as to complete the fixation of the first outer layer pipeline 3 and the second outer layer pipeline 4. The first protective sleeve 6 and the second protective sleeve 7 are pre-welded on the first outer layer pipeline 3 and the second outer layer pipeline 4, and the temperature of the heat transferred from the first protective sleeve 6 and the second protective sleeve 7 to the first outer layer pipeline 3 and the second outer layer pipeline 4 when the first protective sleeve 6 and the second protective sleeve 7 are welded on site is not enough to damage the anticorrosive coating 5 on the inner wall of the first outer layer pipeline 3 and the second outer layer pipeline 4.

[0043] The first protective sleeve 6 and the second protective sleeve 7 form a cavity with the first outer layer pipeline 3 and the second outer layer pipeline 4, and an anticorrosive material layer 10 is filled in the cavity to play a sealing and buffering role. In the embodiment, the first protective sleeve 6 is provided with an overflow hole, and the second protective sleeve 7 is provided with an injection hole, so as to facilitate the injection and filling of the anticorrosive material.

[0044] The embodiment also discloses a preparation method of the nuclear power plant liquid effluent discharge double-layer pipeline structure.

[0045] Inner layer pipeline welding: the first inner layer pipeline 1 and the second inner layer pipeline 2 are inserted into the electric heating melting ring 9, the on-site electric heating melting equipment is started to connect the first inner layer pipeline 1 and the second inner layer pipeline 2 into a whole, and the support roller assembly 8 is installed on the first inner layer pipeline 1 and the second inner layer pipeline 2 respectively, and the support roller assembly 8 can be before or after the butt joint of the first inner layer pipeline 1 and the second inner layer pipeline 2.

[0046] Outer layer pipeline butt joint step: the first outer layer pipeline 3 and the second outer layer pipeline 4, which are welded with the first protective sleeve 6 and the second protective sleeve 7 and brushed with the anticorrosive coating 5, are respectively sleeved on the butt-jointed first inner layer pipeline 1 and the second inner layer pipeline 2 through the support roller assembly 8, so that the first outer layer pipeline 3 and the second outer layer pipeline 4 are spliced through the first step 31 and the second step 32, and the butt joint of the first protective sleeve 6 and the second protective sleeve 7 is ensured.

[0047] Outer pipe welding step: the preparation work before welding is completed, the welding equipment is started, the automatic welding machine is made to perform girth welding along the butt joint position of the first protective sleeve 6 and the second protective sleeve 7, and cleaning and non-destructive testing are performed after welding.

[0048] Filling anticorrosive material step: the cavity formed between the first protective sleeve 6, the second protective sleeve 7 and the first outer layer pipeline 3 and the second outer layer pipeline 4 is filled with anticorrosive material by using a filling device, the anticorrosive material is injected through the injection hole on the second protective sleeve 7 during filling, and finally the anticorrosive material layer 10 is formed.

[0049] Example 2:

[0050] Reference Figure 4 The rest of this embodiment is the same as that of example 1, except that in this embodiment, the first outer layer pipeline 3 and the second outer layer pipeline 4 are welded with the first flange plate 12 and the second flange plate 11, after the first outer layer pipeline 3 and the second outer layer pipeline 4 are spliced through the first step 31 and the second step 32, the first flange plate 12 and the second flange plate 11 are connected through bolts, and then the automatic welding machine is made to perform girth welding along the butt joint position of the first flange plate 12 and the second flange plate 11, and cleaning and non-destructive testing are performed after welding.

[0051] The above are preferred embodiments of the present application, which do not limit the protection scope of the present application, so that: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A nuclear power plant liquid effluent discharge double-wall pipe structure, characterized by: The outer pipe connecting piece is a protective sleeve, the protective sleeve is connected with the outer layer pipe, and when the two adjacent outer layer pipes are spliced, the two protective sleeves are connected through welding.

2. A double containment piping structure for liquid effluent discharge from a nuclear power plant according to claim 1, characterized in that: The protective sleeve includes a sleeve part coaxially arranged with the outer layer pipe and a shaft end part connected with the sleeve part, the shaft end part is fixedly connected with the outer layer pipe, a cavity is formed between the protective sleeve and the outer layer pipe, and a layer of anticorrosive material is filled in the cavity.

3. A double containment piping structure for liquid effluent discharge from a nuclear power plant according to claim 2, characterized in that: The inner layer pipe is made of HDPE material, and the two adjacent inner layer pipes are connected through an electric heating melting ring.

4. A double containment piping system for liquid effluent from a nuclear power plant according to claim 1, wherein: The outer pipe connecting piece is a connecting flange, the connecting flange is connected with the outer layer pipe, and when the two adjacent outer layer pipes are spliced, the two connecting flanges are locked through bolts and are connected through welding.

5. A double containment piping system for liquid effluent discharge from a nuclear power plant as defined in claim 1 wherein: A supporting frame roller assembly is further arranged between the inner layer pipe and the outer layer pipe.

6. A double containment piping system for liquid effluent from a nuclear power plant according to claim 1, wherein: The two adjacent outer layer pipes are connected through stepped bevel butt joint, and the two outer layer pipes are respectively provided with a first step and a second step on one side and the gap between the first step and the second step is less than 0.5 mm.

7. A double containment piping system for liquid effluent discharge from a nuclear power plant according to claim 1, wherein: ​

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