Nuclear power plant liquid effluent discharge double-layer pipeline structure and preparation method

Abstract

The invention discloses a nuclear power plant liquid effluent discharge double-layer pipeline structure and a preparation method thereof.The double-layer pipeline structure 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 invention relates to the field of nuclear sewage discharge, and in particular to a connection structure of a double-layer pipe for discharging liquid effluent from a nuclear power plant and a preparation method thereof. Background Art

[0002] During the operation of nuclear power plants, a large amount of liquid effluent is generated, which contains trace amounts of radioactive substances. In order to ensure environmental safety, these liquid effluents need to be treated before being discharged. At present, the discharge pipes of liquid effluents from nuclear power plants are mostly single-layer structures, which are prone to corrosion and leakage during long-term use, not only affecting the discharge effect, but also causing environmental pollution. A few discharge pipes are double-layer structures, and the outer pipe is prone to damage the anti-corrosion coating on the inner wall of the outer pipe during welding, further causing corrosion and leakage of the outer pipe. With the development of new energy laws, the country has gradually invested more resources in the development and construction of nuclear power plants. Therefore, it is urgent to develop a connection method and structure for the discharge pipes of liquid effluents from nuclear power plants. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a connection structure of a double-layer pipe for discharging liquid effluent from a nuclear power plant and a preparation method thereof.

[0004] The present invention provides a connection structure of a double-layer pipe for discharging liquid effluent from a nuclear power plant and a preparation method thereof, which adopts the following scheme: A double-layer pipeline structure for discharging liquid effluent from a nuclear power plant comprises an inner layer pipeline spliced ​​in the length direction, an outer layer pipeline spliced ​​in the length direction and an outer pipe connector arranged on the outer layer pipeline, an anti-corrosion coating is arranged on the inner wall of the outer layer pipeline, and two adjacent outer layer pipelines are spliced ​​and connected by welding through two adjacent outer pipe connectors.

[0005] Through the above technical solution, by using the outer pipe connector as a transition structure for welding, direct welding operations on the outer pipe body are avoided, thereby protecting the integrity of the inner wall anti-corrosion coating. The welding heat mainly acts on the outer pipe connector rather than the outer pipe body, significantly reducing the risk of heat damage to the anti-corrosion coating. At the same time, the inner pipe adopts a splicing structure and can be installed and maintained in sections. The splicing welding of the outer pipe further improves the sealing and pressure resistance of the overall structure. The double protection mechanism ensures the safety of radioactive liquid transportation.

[0006] As a preferred embodiment of the present invention, the outer pipe connector is a protective sleeve, the protective sleeve is connected to the outer layer pipe, and when two adjacent outer layer pipes are spliced, the two adjacent protective sleeves are connected by welding.

[0007] Through the above technical solution, by using a protective sleeve as an outer pipe connector, precise thermal isolation is achieved during the outer pipe welding process. The protective sleeve is pre-welded and fixed to the outer pipe. During welding, the heat is concentrated in the docking area between the protective sleeves to prevent the outer pipe body from being heated and causing carbonization failure of the anti-corrosion coating. The circumferential welding process of the protective sleeve forms a continuous sealed weld, which not only ensures the connection strength, but also reduces the temperature rise of the inner wall of the outer pipe through physical isolation. While ensuring the structural strength, this design controls the heat-affected range of the anti-corrosion coating within the safety threshold, significantly extending the anti-corrosion life of the outer pipe.

[0008] As a preferred embodiment of the present invention, the protective sleeve includes a shaft sleeve portion coaxially arranged with the outer pipe and a shaft end portion connected to the shaft sleeve portion, the shaft end portion is fixedly connected to the outer pipe, a cavity is formed between the protective sleeve and the outer pipe, and a layer of anti-corrosion material is filled in the cavity.

[0009] Through the above technical solution, the anti-corrosion material (such as epoxy resin) filled in the cavity can penetrate into the tiny gap between the outer pipe and the protective sleeve, forming a chemical bonding layer to prevent 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 pipe, which can buffer the stress caused by temperature changes and prevent the weld of the protective sleeve from cracking. This design further improves the anti-penetration and anti-corrosion performance of the weld area through the synergistic effect of "mechanical isolation + chemical protection".

[0010] As a preferred embodiment of the present invention, the inner layer pipe is made of HDPE material, and two adjacent inner layer pipes are connected by an electric hot melt ring.

[0011] Through the above technical solution, the HDPE inner layer pipe is combined with the electric hot melt ring connection technology to achieve zero leakage sealing of the radioactive liquid transportation pipeline. HDPE material has excellent radiation resistance and chemical corrosion resistance. The electric hot melt ring melts and fuses the adjacent pipe end faces through resistance heating to form a seamless connection at the molecular level. The sealing performance of the electric hot melt connection is more than 3 times that of the mechanical connection, which is particularly suitable for harsh working conditions that are subjected to long-term radioactive liquid flushing.

[0012] As a preferred embodiment of the present invention, the outer pipe connector is a connecting flange, and the connecting flange is connected to the outer layer pipe. When two adjacent outer layer pipes are spliced, the two adjacent connecting flanges are locked by bolts and connected by welding.

[0013] Through the above technical solution, the mechanical seal of the flange is achieved through the bolt pre-tightening force, and the initial positioning of the pipeline is completed; then the circumferential seam welding is performed to form a secondary sealing barrier. Bolted connection can compensate for pipeline installation deviation, and welding eliminates possible micro gaps in the flange interface.

[0014] As a preferred embodiment of the present invention, a support frame roller assembly is further provided between the inner layer pipe and the outer layer pipe.

[0015] Through the above technical solution, the support frame roller assembly forms a slidable support point on the outer wall of the inner pipe, allowing the outer pipe to move smoothly along the axial direction during installation to avoid hard friction and damage to the anti-corrosion coating. At the same time, the circumferential uniform distribution design of the roller ensures that the inner and outer pipes maintain precise coaxiality to prevent local stress concentration caused by eccentricity.

[0016] As a preferred embodiment of the present invention, two adjacent outer layer pipes are butted against each other via a stepped groove, and adjacent sides of the two outer layer pipes are provided with a first step and a second step respectively, and the gap between the two steps is smaller than 0.5 mm.

[0017] Through the above technical solution, the stepped groove butt joint structure realizes high-precision assembly welding. The cooperation between the first step and the second step forms a labyrinth sealing interface, which controls the butt joint gap within 0.5mm and significantly reduces the volume of the welding pool. At the same time, the stepped structure plays a self-positioning role in the welding process, making the weld formation more uniform.

[0018] The present invention also discloses a method for preparing the above-mentioned double-layer pipeline structure for discharging liquid effluent from a nuclear power plant, comprising the following steps: Step S1, inner layer pipe welding: insert two adjacent inner layer pipes into the electric hot melt ring, start the on-site electric hot melt equipment to connect the two adjacent inner layer pipes into a whole; Step S2, butt joint of outer layer pipes: two adjacent outer layer pipes are butt jointed by translation through the support frame roller assembly, each outer layer pipe is welded and connected with an outer pipe connector, and an anti-corrosion coating is provided on the inner wall of each outer layer pipe, and after the two outer layer pipes are butt jointed, they are simultaneously passed to ensure that the two adjacent outer pipe connectors are butt jointed; Step S3, fixing the outer layer pipe: complete the preparatory work before welding, start the welding equipment, and make the automatic welding machine perform circumferential welding along the butt joint position of two adjacent outer pipe connectors, clean up after welding, and perform non-destructive testing.

[0019] Through the above technical solution, the welding strategy of "first inside and then outside, isolated in steps" is adopted to complete the electric hot-melt sealing connection of the inner HDPE pipe first to form a leak-free lining; ② Through the precise positioning of the support frame roller assembly, the outer pipe maintains a uniform gap with the inner pipe during the translational docking process to avoid mechanical friction causing scratches on the anti-corrosion coating; the welding operation is limited to the docking area of ​​the outer pipe connector, and the heat cannot be fully transferred to the outer pipe body during welding, ensuring that the inner wall anti-corrosion coating is not thermally degraded.

[0020] As a preferred embodiment of the present invention, the outer pipe connecting piece is a protective sleeve, and an automatic welding machine performs circumferential welding along the butt joints between the protective sleeves and the protective sleeves, and cleans up after welding. After non-destructive testing, a filling device is used to fill the cavity between two adjacent protective sleeves and two adjacent outer pipes with anti-corrosion material.

[0021] Through the above technical scheme, a dynamic anti-corrosion barrier is constructed through the synergistic effect of protective sleeve welding and cavity filling. After the protective sleeve is circumferentially welded, the liquid anti-corrosion material is evenly filled into the cavity between the protective sleeve and the outer layer of the pipeline using a pressure injection process. After solidification, a composite protective layer with both sealing and flexibility is formed. A triple protection mechanism is achieved: the filling material fits tightly to the metal surface, effectively sealing the microscopic defects that may occur in the heat-affected zone of welding; the elastic material layer absorbs the thermal expansion and contraction stress of the pipeline through deformation to avoid coating peeling caused by temperature changes; the filling layer forms a continuous protective interface with the original anti-corrosion coating to block the diffusion path of the corrosive medium. This process significantly improves the anti-permeability and mechanical durability of the pipeline connection parts, and is particularly suitable for the long-term protection needs of the high humidity and highly corrosive environment of nuclear power plants.

[0022] As a preferred embodiment of the present invention, the outer pipe connector is a connecting flange, the connecting flange is connected to the outer layer pipe, two adjacent outer layer pipes are fixed, and two adjacent connecting flanges are locked by bolts and connected by welding.

[0023] Through the above technical solution, through the composite design of flange connection and welding, the flange bolts are used to achieve rapid pre-tightening and positioning, which greatly shortens the pipeline alignment time; full penetration welds are welded on the basis of mechanical connection to form a redundant sealing structure, which significantly improves the long-term reliability of the pipeline system in the complex operating environment of the nuclear power plant.

[0024] In summary, the present invention includes at least one of the following beneficial technical effects: 1. The present invention constructs a multi-level anti-corrosion system of "body protection + structural isolation + active filling". The anti-corrosion coating on the inner wall of the outer pipe serves as the basic protective layer, and the welding isolation design of the outer pipe connector (protective sleeve / flange) effectively blocks welding heat conduction to avoid high-temperature failure of the coating; the protective sleeve cavity is filled with anti-corrosion material to form a secondary sealing layer, which dynamically compensates for micro-gaps caused by temperature deformation or mechanical vibration. Through the synergistic effect of physical isolation, chemical anti-corrosion and dynamic sealing, this system significantly improves the long-term stability of the pipeline in a highly corrosive and high-radiation environment, and fundamentally solves the problem of corrosion leakage caused by welding damage in traditional double-layer pipelines.

[0025] 2. The present invention adopts a step-by-step construction strategy for the inner and outer layer pipelines. The inner layer HDPE pipeline is connected by melting to achieve molecular-level sealing, and the outer layer is assembled quickly and accurately through prefabricated connectors. The support frame roller assembly ensures the centering accuracy of the inner and outer layer pipelines to avoid installation damage; this design enables the pipeline system to have both construction efficiency and operational reliability, which fully meets the strict sealing requirements of nuclear facilities for radioactive medium transportation pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic axial cross-sectional view of a double-layer pipeline structure for discharging liquid effluent from a nuclear power plant according to the present invention.

[0027] Figure 2 It is a radial cross-sectional schematic diagram of a double-layer pipeline structure for discharging liquid effluent from a nuclear power plant according to the present invention.

[0028] Figure 3 The figure is a schematic cross-sectional view of the outer pipe of the double-layer pipe structure for discharging liquid effluent from a nuclear power plant according to the present invention.

[0029] Figure 4 It is a schematic axial cross-sectional view of a double-layer pipe structure for discharging liquid effluent from a nuclear power plant according to Example 2 of the present invention.

[0030] Description of reference numerals: 1. first inner layer pipeline; 2. second inner layer pipeline; 3. first outer layer pipeline; 4. second outer layer pipeline; 5. anti-corrosion coating; 6. first protective cover; 7. second protective cover; 8. Support frame roller assembly; 81. First fixed plate; 82. Second fixed plate; 83. Pulley; 9. Electric hot melt ring; 10. Anti-corrosion material layer; 11. Second flange; 12. First flange; 31. First step groove; 32. Second step groove. DETAILED DESCRIPTION

[0031] The following is combined with Figure 1-4 The present invention is described in further detail.

[0032] Embodiment 1: See attached Figure 1 To the attached Figure 3 This embodiment discloses a double-layer pipe structure for discharging liquid effluent from a nuclear power plant, comprising a first inner pipe 1, a second inner pipe 2, a first outer pipe 3, and a second outer pipe 4. The first inner pipe 1 and the second inner pipe 2 are made of HDPE, and the first inner pipe 1 and the second inner pipe 2 are connected by an electric hot melt ring 9 to form an inner pipe for conveying liquid effluent.

[0033] A support frame roller assembly 8 is fixed on the inner wall of the first inner layer pipe 1, and the support frame roller assembly 8 includes two semicircular ring fixing plates, namely a first fixing plate 81 and a second fixing plate 82, and pulleys 83 are fixed on the first fixing plate 81 and the second fixing plate 82. The support frame roller assembly 8 is used for positioning and guiding when installing the first outer layer pipe 3 and the second outer layer pipe 4.

[0034] The first outer layer pipe 3 and the second outer layer pipe 4 are made of carbon steel, and the first step 31 and the second step 32 are respectively provided on the adjacent sides of the two outer layer pipes, and the gap between them is less than 0.5 mm. The first outer layer pipe 3 and the second outer layer pipe 4 are respectively spliced ​​by the first step 31 and the second step 32 to form the outer layer pipe, and the inner wall of the first outer layer pipe 3 and the second outer layer pipe 4 is provided with an anti-corrosion coating 5.

[0035] The first outer layer pipe 3 and the second outer layer pipe 4 are respectively provided with outer pipe connectors for fixing the first outer layer pipe 3 and the second outer layer pipe 4. In this embodiment, the first outer layer pipe 3 is provided with a first protective sleeve 6, and the second outer layer pipe 4 is provided with a second protective sleeve 7. The first protective sleeve 6 and the second protective sleeve 7 are a symmetrical structure, both of which include a shaft sleeve portion coaxially arranged with the first outer layer pipe 3 or the second outer layer pipe 4 and an axial end portion connected to the shaft sleeve portion. The axial end portion of the first protective sleeve 6 is welded to the first outer layer pipe 3 to fix the first protective sleeve 6 on the first outer layer pipe 3, and the axial end portion of the second protective sleeve 7 is welded to the second outer layer pipe 4 to fix the second protective sleeve 7 on the second outer layer pipe 4. After the first outer layer pipe 3 and the second outer layer pipe 4 are spliced ​​by the first step 31 and the second step 32, the first protective sleeve 6 and the second protective sleeve 7 are abutted against each other, and the first protective sleeve 6 and the second protective sleeve 7 are fixed by welding, thereby completing the fixation of the first outer layer pipe 3 and the second outer layer pipe 4. The first protective cover 6 and the second protective cover 7 are pre-welded to the first outer layer pipe 3 and the second outer layer pipe 4. The first protective cover 6 and the second protective cover 7 can allow the heat during on-site welding to be transferred to the first outer layer pipe 3 and the second outer layer pipe 4, and the temperature is not high enough to destroy the anti-corrosion coating 5 on the inner wall of the first outer layer pipe 3 and the second outer layer pipe 4.

[0036] A cavity is formed between the first protective cover 6, the second protective cover 7, the first outer layer pipe 3 and the second outer layer pipe 4, and the cavity is filled with an anti-corrosion material layer 10 to play a sealing and buffering role. In this embodiment, an overflow hole is opened on the first protective cover 6, and an injection hole is opened on the second protective cover 7 to facilitate the injection and filling of the anti-corrosion material.

[0037] This embodiment also discloses a method for preparing the above-mentioned double-layer pipeline structure for discharging liquid effluent from a nuclear power plant, comprising the following steps: Inner layer pipe welding: insert the first inner layer pipe 1 and the second inner layer pipe 2 into the electric hot melt ring 9, start the on-site electric hot melt equipment to connect the first inner layer pipe 1 and the second inner layer pipe 2 into a whole, and install the support frame roller assembly 8 on the first inner layer pipe 1 and the second inner layer pipe 2 respectively. The support frame roller assembly 8 can be before or after the first inner layer pipe 1 and the second inner layer pipe 2 are connected.

[0038] Outer pipe docking step: The first outer pipe 3 and the second outer pipe 4 pre-welded with the first protective cover 6, the second protective cover 7 and coated with the anti-corrosion coating 5 are respectively sleeved on the docked first inner pipe 1 and the second inner pipe 2 through the support frame roller assembly 8, so that the first outer pipe 3 and the second outer pipe 4 are spliced ​​with the first step 31 and the second step 32, and at the same time, the first protective cover 6 and the second protective cover 7 are ensured to be docked.

[0039] Outer tube welding steps: complete the preparatory work before welding, start the welding equipment, and make the automatic welding machine perform circumferential welding along the joint position of the first protective cover 6 and the second protective cover 7, clean up after welding, and perform non-destructive testing.

[0040] Filling anti-corrosion material step: Use filling equipment to fill the cavity formed between the first protective cover 6, the second protective cover 7 and the first outer layer pipe 3 and the second outer layer pipe 4 with anti-corrosion material. During filling, the anti-corrosion material is injected through the injection hole on the second protective cover 7 to finally form an anti-corrosion material layer 10.

[0041] Embodiment 2: Reference Figure 4 The rest of the present embodiment is the same as that of the embodiment 1, except that, in the present embodiment, the first outer layer pipe 3 and the second outer layer pipe 4 are welded with the first flange 12 and the second flange 11. After the first outer layer pipe 3 and the second outer layer pipe 4 are spliced ​​together through the first step 31 and the second step 32, the first flange 12 and the second flange 11 are connected by bolts, and then the automatic welding machine is used to perform circumferential welding along the butt joint position of the first flange 12 and the second flange 11, and cleaning and non-destructive testing are performed after welding.

[0042] The above are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A double-layer pipeline structure for discharging liquid effluent from a nuclear power plant, characterized in that: It includes an inner pipe spliced ​​in the length direction, an outer pipe spliced ​​in the length direction and an outer pipe connector arranged on the outer pipe. An anti-corrosion coating is arranged on the inner wall of the outer pipe. After two adjacent outer pipes are spliced, they are connected by welding through two adjacent outer pipe connectors.

2. A double-layer pipe structure for discharging liquid effluent from a nuclear power plant according to claim 1, characterized in that: The outer pipe connector is a protective sleeve, which is connected to the outer layer pipe. When two adjacent outer layer pipes are spliced, the two adjacent protective sleeves are connected by welding.

3. A double-layer pipe structure for discharging liquid effluent from a nuclear power plant according to claim 2, characterized in that: The protective sleeve includes a shaft sleeve portion coaxially arranged with the outer pipe and a shaft end portion connected to the shaft sleeve portion, the shaft end portion is fixedly connected to the outer pipe, a cavity is formed between the protective sleeve and the outer pipe, and an anti-corrosion material layer is filled in the cavity.

4. A double-layer pipeline structure for discharging liquid effluent from a nuclear power plant according to claim 1, characterized in that: The inner layer pipes are made of HDPE material, and two adjacent inner layer pipes are connected by an electric hot melt ring.

5. A double-layer pipe structure for discharging liquid effluent from a nuclear power plant according to claim 1, characterized in that: The outer pipe connector is a connecting flange, which is connected to the outer layer pipe. When two adjacent outer layer pipes are spliced, the two adjacent connecting flanges are locked by bolts and connected by welding.

6. A double-layer pipe structure for discharging liquid effluent from a nuclear power plant according to claim 1, characterized in that: A support frame roller assembly is also arranged between the inner layer pipe and the outer layer pipe.

7. A double-layer pipe structure for discharging liquid effluent from a nuclear power plant according to claim 1, characterized in that: Two adjacent outer pipes are butt-jointed via a stepped groove, and adjacent sides of the two outer pipes are provided with a first step and a second step respectively, and the gap between them is less than 0.5 mm.

8. A method for preparing a double-layer pipe structure for discharging liquid effluent from a nuclear power plant, characterized in that: The following steps are involved: Step S1, inner layer pipe welding: insert two adjacent inner layer pipes into the electric hot melt ring, start the on-site electric hot melt equipment to connect the two adjacent inner layer pipes into a whole; Step S2, butt joint of outer layer pipes: two adjacent outer layer pipes are butt jointed by translation through the support frame roller assembly, each outer layer pipe is welded and connected with an outer pipe connector, and an anti-corrosion coating is provided on the inner wall of each outer layer pipe, and after the two outer layer pipes are butt jointed, they are simultaneously passed to ensure that the two adjacent outer pipe connectors are butt jointed; Step S3, fixing the outer layer pipe: complete the preparatory work before welding, start the welding equipment, and make the automatic welding machine perform circumferential welding along the butt joint position of two adjacent outer pipe connectors, clean up after welding, and perform non-destructive testing.

9. The method for preparing a double-layer pipe structure for discharging liquid effluent from a nuclear power plant according to claim 8, characterized in that: The outer pipe connector is a protective sleeve. The automatic welding machine performs circumferential welding along the butt joints between the protective sleeves. After welding, cleaning is performed. After nondestructive testing, the cavity between two adjacent protective sleeves and two adjacent outer pipes is filled with anti-corrosion materials using a filling device.

10. The method for preparing a double-layer pipe structure for discharging liquid effluent from a nuclear power plant according to claim 8, characterized in that: The outer pipe connector is a connecting flange, which is connected to the outer layer pipe. Two adjacent outer layer pipes are fixed, and two adjacent connecting flanges are locked by bolts and connected by welding.

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