Radiation-resistant cable for nuclear power platform and preparation method thereof

Abstract

The invention relates to the field of nuclear cable manufacturing, in particular to a radiation-resistant cable for a nuclear power platform and a preparation method of the radiation-resistant cable. According to the nuclear cable, the five-layer structural design of conductor-insulation-shielding-polyimide film-sheath is adopted, the overlapping wrapping technology of the polyimide film is combined, and the comprehensive performance of the cable in the extreme environment of a nuclear power platform is comprehensively improved. The low-smoke halogen-free flame-retardant ethylene-propylene rubber is adopted as an insulating material, and through the cooperation of an EPDM / POE blending system and the ternary composite flame retardant, the insulating property is stable under the condition of ensuring radiation, and the flame retardant property is excellent. The sheath material is added with the intumescent flame retardant and the polysilazane modifier, so that the cable has no crack at the low temperature of-40 DEG C, the bending radius can be controlled to be less than 5 times of the outer diameter, and the cable is adaptive to the layout of a narrow cabin. Through the synergistic effect of material innovation and structural design, the balance of flame retardant property, mechanical property, radiation resistance, low temperature resistance, aging resistance and small-space applicability of the nuclear cable is realized.

Description

Technical Field

[0001] This invention relates to the field of nuclear cable manufacturing, specifically to a radiation-resistant cable for nuclear power platforms and its preparation method. Background Technology

[0002] With the continuous development of nuclear power technology and the increasing demands for environmental protection, nuclear power platforms are being used more and more widely as mobile small nuclear power plants at sea. They represent an organic combination of small nuclear reactors and marine engineering, providing safe and efficient energy supply for offshore oil extraction and remote islands, and can also be used in high-powered ships and seawater desalination. However, the operating environment of nuclear power platforms is characterized by extremely compact space, high radiation doses, and sudden increases in temperature and pressure during accident conditions, placing stringent requirements on cable systems. Traditional cable materials are prone to aging under strong radiation environments, leading to performance degradation and even safety hazards such as short circuits. Furthermore, harmful heavy metals such as lead, barium, and cadmium contained in traditional cable materials (such as polyvinyl chloride) may gradually leach out during cable use, polluting the environment.

[0003] Currently, some cables are used in land-based nuclear power plants, but they still have some shortcomings and are difficult to directly adapt to the special needs of nuclear power platforms. The harsh environment of nuclear power platforms places extremely stringent and special requirements on cable materials. Such cables need to have excellent radiation resistance, low smoke halogen-free flame retardant properties, good mechanical properties and environmental adaptability, while also taking into account the service life and safety of the materials.

[0004] Currently, some technical solutions exist to address these issues, but all have limitations. For example, after high-dose irradiation, the volume resistivity decreases; the flame retardant performance is poor, failing to meet the Class A standard for bundled flame retardancy; and the oil resistance and abrasion resistance are insufficient, leading to corrosion and wear on the sheath surface after use in high-salt-spray marine environments. Existing nuclear cable materials all have significant performance shortcomings, making it difficult to achieve a good balance between high-dose irradiation resistance, high flame retardant rating, long-term high-temperature stability, compact space application (flexibility), excellent environmental aging resistance (such as salt spray resistance, corrosion resistance, and abrasion resistance), and full life-cycle reliability.

[0005] Therefore, there is an urgent need to develop a new type of cable material with excellent comprehensive performance for nuclear power platforms to overcome the shortcomings of existing technologies, meet the comprehensive requirements of harsh marine environments, and improve the operational safety and reliability of nuclear power platforms. Summary of the Invention

[0006] To address the aforementioned problems in existing technologies, this invention provides a radiation-resistant cable using low-smoke halogen-free flame-retardant ethylene propylene rubber as insulation material and EVA-based low-smoke halogen-free flame-retardant polyolefin as sheath material. Through synergistic innovation in structure and materials, a balance is achieved between flame-retardant performance, mechanical properties, radiation resistance, low-temperature resistance, aging resistance, and suitability for confined spaces.

[0007] The present invention provides a radiation-resistant cable for a nuclear power platform, comprising a core structure and a sheath layer. The core structure includes a conductor, an insulation layer, a shielding layer, and a polyimide film layer. The sheath layer includes an EVA sheath layer and a polyolefin sheath layer. Furthermore, the insulating layer is a low-smoke halogen-free flame-retardant ethylene propylene rubber, including ethylene propylene diene monomer (EPDM) rubber, ethylene-octene copolymer, aluminum hydroxide, magnesium hydroxide, lignin-based flame retardant, phenyl silicone rubber, silane coupling agent, antioxidant, crosslinking agent, and nano titanium dioxide. Furthermore, the polyimide film layer has a thickness of 40-60 μm.

[0008] Furthermore, the outer sheath layer (polyolefin sheath layer) is a low-smoke, halogen-free, flame-retardant, cross-linked polyolefin outer sheath; Furthermore, the conductor is a silver-plated soft copper conductor or a tin-plated soft copper conductor, and is wrapped with an insulating layer, a shielding layer and a polyimide film layer in sequence.

[0009] In some embodiments, the diameter of the single wire of the silver-plated soft copper conductor is 0.12-0.15 mm; and / or, the diameter of the single wire of the tin-plated soft copper conductor is 0.15-0.20 mm; In some preferred embodiments, the conductor is made of 19 strands regularly stranded (stretch pitch 12-15 times the conductor outer diameter), and the conductor DC resistance is ≤0.018Ω / m (20℃). In some implementations, the conductor surface is treated as follows: silver plating thickness ≥ 2 μm (tin plating thickness ≥ 3 μm).

[0010] Furthermore, the insulation layer has a thickness of 0.6-1.2 mm, the shielding layer has a thickness of 0.4-0.8 mm, the polyimide film layer has a thickness of 40-60 μm, the EVA sheath layer has a thickness of 1.2-1.8 mm, and the polyolefin sheath layer has a thickness of 0.2-0.4 mm. By adjusting the thickness ratio of each layer, the cable achieves a compact structure while ensuring strength, making it suitable for applications on nuclear power platforms.

[0011] Further, the insulating layer material specifically includes the following components: 100 parts of ethylene propylene diene monomer (EPDM) rubber, 13-20 parts of ethylene-octene copolymer (POE), 105-120 parts of aluminum hydroxide (ATH), 40-60 parts of magnesium hydroxide (MDH), 16-22 parts of lignin-based flame retardant, 40-60 parts of phenyl silicone rubber (MPVQ), 5.5-7.5 parts of silane coupling agent, 1.5-2.5 parts of antioxidant, 3.5-5 parts of crosslinking agent, and 10-15 parts of nano-titanium dioxide.

[0012] In some embodiments, the EPDM rubber contains 7% ENB; this is used to enhance aging resistance and reduce the rate of thermal aging degradation.

[0013] In some embodiments, the ethylene-octene copolymer contains 25% octene to improve low-temperature flexibility and enhance low-temperature bending performance (-40°C).

[0014] In some embodiments, the aluminum hydroxide has a particle size of 1-3 μm and a surface modified with silane; it serves as the main flame retardant and also has a smoke-suppressing effect; the magnesium hydroxide has a particle size of 0.5-1 μm and a surface modified with stearic acid; it serves as a synergistic flame retardant and improves high-temperature stability. In some embodiments, the lignin-based flame retardant is prepared by compounding alkali lignin and APP, wherein the mass ratio of alkali lignin to APP is 1:2; this enhances the flame retardant synergy and improves the density of the char layer. In some embodiments, the phenyl silicone rubber contains 15% phenyl content; a radiation modifier is used to inhibit molecular chain breakage caused by radiation.

[0015] In some embodiments, the antioxidant is antioxidant 1010; the crosslinking agent is dicumyl peroxide (DCP); which promotes resin crosslinking and enhances mechanical strength.

[0016] In some embodiments, the surface of the nano-titanium dioxide is modified with silane, and the particle size is 10-30 nm; preferably 20 nm.

[0017] Furthermore, the shielding layer is made of tin-plated copper wire braid with a braiding density of ≥90% to suppress electromagnetic interference.

[0018] In some embodiments, the tin-plated copper wire (single wire diameter 0.15-0.18 mm, tin layer thickness ≥ 2 μm). In some embodiments, the braiding process of the tin-plated copper wire is as follows: a 24-spindle braiding machine is used, the braiding density is ≥92% (actual measurement 93-94%), and the braiding pitch is 12-15mm; In some embodiments, the thickness of the tin-plated copper wire is 0.5-0.6 mm (controlled by adjusting the number of copper wires and the braiding density to ensure shielding attenuation ≥60 dB@1 GHz).

[0019] Furthermore, the method for preparing the insulating layer material includes the following steps: S1 involves mixing EPDM rubber and ethylene-octene copolymer in a set ratio, then adding an antioxidant and mixing thoroughly. S2 is blended with aluminum hydroxide, magnesium hydroxide, nano-titanium dioxide and lignin-based flame retardant in a twin-screw extruder at 180-220°C. S3 adds phenyl silicone rubber and a crosslinking agent to the mixture and continues to blend at 170-190℃ to obtain an insulating compound.

[0020] In some embodiments, the EVA sheath layer is made of EVA-based low-smoke halogen-free flame-retardant polyolefin material, with an EVA content of 30-35%.

[0021] Furthermore, the polyimide film layer is made of polyimide resin with a thickness of 40-60 μm. Through an overlapping wrapping process, the overlap rate is controlled at 25-35%, which further improves the radiation resistance of the cable.

[0022] In some embodiments, the polyimide film is made of homopolymer polyimide resin (glass transition temperature 320°C). In some embodiments, the polyimide film has a thickness of 50±5μm, a width of 25-30mm, and a tensile strength ≥200MPa.

[0023] Furthermore, the EVA sheath layer is made of EVA-based low-smoke halogen-free flame-retardant polyolefin material, with an EVA content of 30-35%, and also contains polysilazane modifier, intumescent flame retardant, flame retardant synergist, nano-calcium carbonate and methyl vinyl silicone rubber, with the amount of nano-calcium carbonate added being 3-5% and the amount of methyl vinyl silicone rubber added being 3-5%.

[0024] Furthermore, the EVA sheath layer comprises the following components: 100 parts EVA, 20-25 parts ethylene-butyl ether copolymer, 5-6.5 parts polysilazane modifier, 22-27 parts intumescent flame retardant, 1-2 parts flame retardant synergist, 5.5-6.5 parts nano calcium carbonate, 5.5-7.0 parts methyl vinyl silicone rubber, 0.3-0.5 parts antioxidant, and 0.7-1.2 parts lubricant.

[0025] In some preferred embodiments, the EVA contains 33% VA and has a melt flow index of 2.5 g / 10 min; as a base resin, it provides flexibility and adhesion.

[0026] In some embodiments, the ethylene-butyl ether copolymer contains 18% butyl ether; this improves low-temperature resistance and oil resistance. In some embodiments, the polysilazane modifier contains 45% silicon, which enhances radiation resistance and thermal stability.

[0027] In some embodiments, the intumescent flame retardant is a mixture of APP / PER / MEL, wherein the mass ratio of APP / PER / MEL is 3:1:1; forming an intumescent char layer to enhance the flame retardant effect.

[0028] In some embodiments, the flame retardant synergist is zinc borate, which enhances the stability of the char layer and solves the problems of cracking and dripping under long-term burning.

[0029] In some embodiments, the nano-calcium carbonate has a particle size of 50-80 nm and a surface modified with titanate; this enhances wear resistance and reduces wear.

[0030] The methyl vinyl silicone rubber contains vinyl groups in its molecular structure, making it compatible with EVA and possessing excellent radiation resistance and high temperature resistance.

[0031] In some embodiments, the antioxidant is a mixture of antioxidant 168 and antioxidant 1010; the two work synergistically to inhibit thermal aging.

[0032] In some embodiments, the lubricant is ethylene bis-stearamide (EBS); it improves processing fluidity and prevents extrusion sticking to the mold.

[0033] Furthermore, the polyolefin outer sheath has a thickness of 0.2-0.4 mm, which further enhances the cable's heat resistance and mechanical strength; In one embodiment, the polyolefin outer sheath layer comprises: 100 parts linear low-density polyethylene, 35-38 parts EVA, 80-90 parts aluminum hydroxide, 35-45 parts magnesium hydroxide, 2.5-3.0 parts crosslinking agent, 0.5-0.9 parts antioxidant, and 0.4-0.8 parts ultraviolet absorber. This component of the polyolefin outer sheath exhibits excellent flame-retardant properties, with an oxygen index ≥32%, meeting the low-smoke halogen-free standard.

[0034] In some embodiments, the linear low-density polyethylene has a melt index of 1.8 g / 10 min; as the base resin for the outer sheath layer, it provides mechanical strength. The EVA contains 28% VA and has a melt index of 3.0 g / 10 min; it enhances flexibility and flame retardant compatibility. The aluminum hydroxide has a particle size of 2-4 μm and is surface-modified with silane. The magnesium hydroxide has a particle size of 1-2 μm and is surface-modified with stearic acid.

[0035] In some embodiments, the crosslinking agent is triallyl isocyanurate (TAIC), which promotes slight crosslinking of the material; In some embodiments, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a 1:1 mass ratio, which inhibits thermo-oxidative aging and extends service life; In some embodiments, the ultraviolet absorber is UV-531; this enhances UV resistance and is suitable for the open-air environment of offshore platforms.

[0036] Beneficial effects: Compared with the prior art, the beneficial effects of the present invention are at least as follows: (1) This invention uses low-smoke halogen-free flame-retardant ethylene propylene rubber as the insulating material. By adding composite flame retardants and radiation modifiers, the radiation resistance of the cable is significantly improved. After 2800 kGy extreme irradiation, the volume resistivity remains at 3×10⁻⁶. 13 With an insulation strength of Ω·cm or higher, the insulation performance remains stable, meeting the usage requirements of nuclear power platforms in high-radiation environments. (2) The insulating material of the present invention adopts an EPDM / POE blend system. Through the synergistic effect of the ternary composite flame retardant, a stable flame retardant network structure is formed. The carbonization height is below 0.9. At the same time, it has good low smoke and halogen-free characteristics, which effectively improves the flame retardant level of the cable and ensures the safety of the compartment. (3) The sheath material of the present invention is made of EVA-based low-smoke halogen-free flame-retardant polyolefin. By adding intumescent flame retardant and polysilazane modifier, good flame retardant effect and mechanical properties are achieved. It does not crack at a low temperature of -40℃, and the bending radius can be controlled to be less than 5 times the outer diameter, which can meet the layout requirements of narrow compartments; (4) The present invention adopts a five-layer structure design of “conductor-insulation-shielding-polyimide film-sheath”. Through the overlapping wrapping process of polyimide film, a dense radiation protection barrier is formed, which reduces the actual radiation dose received by the insulation layer by 30%, effectively improving the overall radiation resistance of the cable. (5) The sheath material of the present invention enhances wear resistance and oil resistance by adding nano calcium carbonate and methyl vinyl silicone rubber and other additives, adapts to the harsh conditions of high humidity and high salt spray in marine environment, and extends the service life of the cable; the low smoke halogen-free flame retardant cross-linked polyolefin outer sheath not only meets the requirements of low smoke halogen-free, but also further enhances the heat resistance and mechanical strength of the cable, making it more suitable for the use environment of nuclear power platform. Attached Figure Description

[0037] The accompanying drawings are provided to further illustrate the present application and form part of the specification. They are used together with the embodiments of the present application to explain the application and do not constitute a limitation thereof. In the drawings: Figure 1 A schematic diagram of the structure of the radiation-resistant cable for the nuclear power platform of this invention; Figure 1In the middle, 1. conductor, 2. insulation layer, 3. filler, 4. wrapping layer, 5. shielding layer, 6. polyimide layer, 7. EVA sheath layer, 8. polyolefin outer sheath. Detailed Implementation

[0038] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification. Many specific details are set forth in the following description to provide a thorough understanding of the present invention; however, the present invention may also be implemented in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0039] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and instruments described are commercially available unless otherwise specified.

[0040] The test methods for each performance indicator in the embodiment are shown in the table below: Some of the raw materials used in the embodiments of this invention: Nano titanium dioxide (particle size 20nm, surface modified with silane); In some embodiments, the nano-titanium dioxide is 20nm in size, physically entangled with EPDM and POE molecular chains to compensate for high filling defects and improve tensile strength ≥8.0MPa; in terms of synergistic flame retardancy, it can catalyze the carbonization of lignin-based flame retardants, adsorb ATH / MDH decomposition products, improve the stability of the char layer and the smoke suppression effect, and improve the light transmittance of the cable; in terms of enhancing radiation resistance, the surface groups can capture radiation free radicals and form Si-O-Ti bonds with MPVQ silicon oxide chains to construct an auxiliary crosslinking network, which can improve the tensile strength after irradiation.

[0041] In some embodiments, the polyimide film is a homopolymer polyimide resin with a glass transition temperature of 320°C; it has a thickness of 52 μm, a width of 25-30 mm, and a tensile strength ≥200 MPa. The wrapping process uses a single-screw wrapping machine at a speed of 8-10 m / min, with tension controlled at 5-8 N and an overlap rate of 31%. Radiation protection performance test at this overlap rate: after irradiation with 2800 kGy, the film's transmittance attenuation rate is ≤15%, and it reduces the actual radiation dose received by the inner insulating layer by 30% (from 2800 kGy to 1990 kGy).

[0042] In one embodiment of the present invention, the cable structure of the present invention is as follows: Figure 1 As shown: The cable's outer diameter is 12.2mm; the center consists of a 19-strand stranded silver-plated soft copper conductor 1 (attached). Figure 1 The number of conductors (not representing the actual number) is 0.15mm in diameter per wire, with a total diameter of 3.8mm and a 2μm thick silver plating layer. It is the core conductive component of the cable. Insulation layer 2: Tightly wraps the conductor, 0.9mm thick, made of low-smoke halogen-free flame-retardant ethylene propylene rubber, with a ring-shaped cross-section, concentric with the conductor. Filler material 3 is located between the wrapping layer 4 and the insulation layer 2. Shielding layer 5 is located outside the wrapping layer 4, 0.55mm thick, woven from tin-plated copper wire (0.16mm) with a braiding density of 93%, forming a mesh structure, covering the surface of the insulation layer. Polyimide film layer 6: Wrapped around the outside of the shielding layer 5, 52μm thick, with an overlap rate of 31%, forming a continuous and dense ring barrier. EVA sheath layer 7 is extruded around the outside of the polyimide film layer 6, 1.5mm thick, made of EVA-based low-smoke halogen-free flame-retardant polyolefin, and tightly bonded to the film layer. The outermost polyolefin sheath layer 8 is located on the outermost layer, with a thickness of 0.3mm, and is made of low-smoke halogen-free flame-retardant cross-linked polyolefin.

[0043] In some implementations, when the cable contains more than two bundles of conductors, filler and wrapping are required; if the cable contains only a single bundle of conductors, filler and wrapping are not required.

[0044] In some embodiments, the overall structural parameters of the cable obtained by the present invention are as follows: Conductor: 19 strands, stranding pitch 12-15 times outer diameter; insulation layer thickness 0.8-1.0mm, extrusion temperature 185-215℃, traction speed 6-8m / min; shielding layer thickness 0.5-0.6mm, 24-spindle braiding machine, braiding density 93-94%, pitch 12-15mm; polyimide film layer thickness 50±5μm, wrapping speed 8-10m / min, tension 5-8N, overlap rate 30±2%; sheath layer thickness 1.4-1.6mm, extrusion temperature 175-205℃, traction speed 5-7m / min; outer sheath thickness 0.3mm, extrusion temperature 180-210℃, traction speed 5-6m / min; minimum bending radius ≤ 6 times outer diameter.

[0045] Examples 1-6 The embodiments and comparative examples of the cable material for the nuclear cable insulation layer of this invention are shown in Table 1; The preparation method includes the following steps: (1) Premixing: Put POE and EPDM into a high-speed mixer (model GH-500), mix at low speed (500r / min) for 3min, then add antioxidant 1010 and mix at high speed (1500r / min) for 5min. The mixing temperature is controlled at 60-70℃ to ensure uniform dispersion of resin. (2) Blending extrusion: The premixed material is fed into a twin-screw extruder (model TE-75, length-to-diameter ratio 40:1), the screw speed is 320 r / min, and the temperature is controlled in stages: feeding section: 185-195℃; melting section: 205-215℃; homogenization section: 210-220℃; Then aluminum hydroxide, magnesium hydroxide, and lignin-based flame retardant are added and mixed in the melting and homogenizing sections for 8-10 minutes. (3) Modification and granulation: Phenyl silicone rubber and crosslinking agent DCP are added at the end of the homogenization section by side feeding, and the mixture is continued to be mixed at 170-190℃ for 3-4 min. After extrusion, the mixture is cooled by water (water temperature 20-25℃) and granulated (granulation speed 300r / min, particle size 3×3mm) to obtain insulating rubber granules. (4) Insulating tube forming: The insulating rubber granules are fed into a single screw extruder (model SJ-65). The extrusion temperature is divided into sections: barrel zone 1: 185℃, zone 2: 195℃, zone 3: 205℃; die head temperature: 210℃. Vacuum sizing (vacuum degree -0.06MPa), traction speed 7m / min, cooling water temperature 25-30℃, cooling time 15-20s are used to obtain an inner diameter that matches the conductor (e.g., 10mm). 2 The conductor is compatible with insulating tubular materials with an inner diameter of 4.0 mm and a thickness of 0.9 mm.

[0046] Table 1. Raw material ratios for insulation materials in the examples and comparative examples: Comparative Examples 1-3 The preparation process is as described in the example. The performance test results of the examples and comparative examples are shown in Table 2. Table 2. Insulation material performance tests of the examples and comparative examples. As shown in Table 2, the insulating materials prepared in Examples 1 to 6 of this invention exhibit excellent comprehensive performance, meeting the stringent requirements of nuclear power platforms. They demonstrate outstanding flame retardant safety, with a carbonization height (0.6-0.9 mm) far exceeding the standard. Simultaneously, they possess excellent low-temperature toughness (50-58% elongation at break at -35℃), ensuring the physical stability of the cable in extreme environments. Even after 2800 kGy strong radiation, the volume resistivity remains stable. While Examples 2 and 5 initially show less prominent volume resistivity, the resistivity change is small after 2800 kGy irradiation aging, still meeting performance requirements after irradiation, thanks to the synergistic effect between key components.

[0047] Comparative Examples 1-4 fail to achieve a balance in overall performance. Comparative Example 1 exhibits poor toughness, with an elongation at break of only 210%, and this elongation decreases significantly at low temperatures, failing to meet the requirements of the harsh environment of nuclear power platforms. Comparative Example 2 shows a significantly lower flame-retardant performance compared to the examples, with a carbonization height 35%-100% higher. Comparative Examples 3 / 4 show a substantial deterioration in carbonization height and a significant increase in volume resistivity after aging, indicating that the addition of nano-titanium dioxide plays a role in flame retardancy and radiation resistance. Furthermore, when the addition amount reaches a certain range (greater than 8 parts), the overall performance of the insulation material is significantly improved.

[0048] In summary, this invention, through optimized formulation design, achieves a high level of balance and synergy among multiple key properties of the insulating material, including flame retardancy, radiation resistance, low-temperature toughness, and mechanical strength. Its overall performance far surpasses that of the comparative example, fully demonstrating its reliability in the specific application scenario of nuclear power platforms.

[0049] Example 7 Preparation of EVA-based low-smoke halogen-free flame-retardant polyolefin (sheath layer) The sheath layer is made of EVA-based low-smoke halogen-free flame-retardant polyolefin material, specifically including EVA (VA 33%): 100 parts, ethylene-butyl ether copolymer (EBAR): 22.5 parts, polysilazane modifier: 5.5 parts, intumescent flame retardant (APP / PER / MEL=3:1:1): 26 parts, flame retardant synergist: 1.5 parts, nano calcium carbonate (50-80nm): 5.8 parts, methyl vinyl silicone rubber: 6.2 parts, antioxidant 168 + antioxidant 1010 (1:1): 0.35 parts, lubricant EBS: 0.85 parts.

[0050] The preparation process includes the following steps: (1) Low-speed mixing: Put EVA and EBAR into a high-speed mixer (GH-500) and mix at low speed (600r / min) for 4 minutes. The temperature is controlled at 50-60℃ to avoid resin melting. (2) Additives and high-speed mixing: Add polysilazane modifier, intumescent flame retardant, nano calcium carbonate, methyl vinyl silicone rubber, antioxidant 168 and lubricant EBS in sequence, mix at high speed (1800r / min) for 8min, and control the mixing endpoint temperature at 80-85℃ to ensure that the additives uniformly coat the resin. (3) Twin-screw compounding extrusion: The mixture is fed into a twin-screw extruder (TE-75, length-to-diameter ratio 40:1), the screw speed is 350 r / min, and the temperature is divided into sections: feeding section: 175-185℃, melting section: 195-205℃, homogenization section: 200-210℃; The blending residence time is 7-9 min, and after extrusion, it is subjected to air-cooled hot cutting (air temperature 40-50℃, cutting speed 350 r / min, particle size 2.5×2.5 mm) to obtain sheathed rubber granules; The sheath layer of this component has excellent mechanical properties; tensile strength of 13.8 MPa; elongation at break of 225%; no cracks or whitening after bending (6 times outer diameter) after freezing at -35℃ for 24h; tensile strength change rate of 5.2% after heat aging at 120℃ for 240h.

[0051] Example 8: Overall fabrication of radiation-resistant cables for nuclear power platforms Equipment used: stranding machine, braiding machine, wrapping machine, extruder (SJ-65, SJ-50), online thickness gauge, radiation resistance testing device.

[0052] (1) Conductor: 10mm 2 Silver-plated soft copper conductor (0.15mm single wire, 19 strands twisted together, 3.8mm in diameter). (2) Insulating tube: The insulating tube prepared in Example 1 (inner diameter 4.0 mm, thickness 0.9 mm) was used. (3) Shielding layer material: tin-plated copper wire (0.16mm, tin layer thickness 2μm); (4) Polyimide film: 52μm thick, 28mm wide; (5) Sheathing particles: Sheathing particles prepared in Example 7; (6) Outer sheath granules: Low-smoke halogen-free flame-retardant cross-linked polyolefin granules; Formula: 55 parts linear low-density polyethylene (LLDPE, melt index 1.8 g / 10 min); 20 parts EVA (VA content 28%, melt index 3.0 g / 10 min); 45 parts aluminum hydroxide (particle size 2-4 μm, surface silane modified); 20 parts magnesium hydroxide (particle size 1-2 μm, surface stearic acid modified); 1.5 parts cross-linking agent TAIC (trimethylene isocyanurate); 0.4 parts antioxidant 1010+168 (mass ratio 1:1); 0.2 parts ultraviolet absorber (UV-531). The outer sheath thickness is 0.3 mm, further enhancing the cable's heat resistance and mechanical strength, with an oxygen index ≥32%.

[0053] Preparation steps: 1) Conductor-insulating layer: The silver-plated soft copper conductor is inserted into the insulating tube and then coated twice using an extrusion process (SJ-65 extruder) to ensure that the insulation layer is tightly bonded to the conductor; 2) Braided shielding layer: The insulated wire core is placed into a 24-spindle braiding machine (model ZB24) and braided with 2 parallel strands (12 tinned copper wires per strand), with a braiding density of 93% and a braiding pitch of 14mm. 3) Wrapping polyimide film layer: Place the shielded wire core into a single screw wrapping machine (model RB-100), wrapping speed 9m / min, tension 7N, overlap rate 31%, to ensure that the film is not exposed or wrinkled, and dry it with hot air after wrapping (60℃×5min). 4) Extruding the sheath layer: The wrapped wire core is fed into the SJ-65 extruder to extrude the sheath granules. Temperature segmentation: Barrel zone 1: 175℃, zone 2: 185℃, zone 3: 195℃; Die head temperature: 200℃; Traction speed: 6m / min, vacuum sizing, cooling water temperature: 30℃, sheath thickness controlled at 1.5mm; 5) Extruding the outer sheath: The sheathed cable is fed into an SJ-50 extruder to extrude a low-smoke, halogen-free, flame-retardant cross-linked polyolefin outer sheath. Temperature zones: Barrel zone 1: 180℃, zone 2: 190℃, zone 3: 200℃; die head temperature: 205℃; traction speed: 5.5m / min; cooling water temperature: 25℃; outer sheath thickness controlled at 0.3mm (deviation ±0.02mm). 6) Crosslinking and curing: Place the finished cable in a hot air aging chamber (120℃×4h) for crosslinking and curing to ensure that the crosslinking degree of the outer sheath is ≥70%.

[0054] Performance testing of the manufactured cable: Outer diameter 12.2mm (including conductor 3.8mm + insulation 0.9mm×2 + shielding 0.55mm×2 + film 0.052mm×2 + sheath 1.5mm×2 + outer sheath 0.3mm×2); Minimum bending radius 4.5 times outer diameter (no cracks after bending at -40℃); Bundling flame retardant performance Class A (carbonization height 0.8m); Salt spray resistance (5% NaCl × 1000h): No corrosion; tensile strength change rate: 4.5%. The tensile strength reduction rate after heat aging at 150℃ for 1000h was 11.2%.

[0055] In summary, this invention comprehensively improves the overall performance of cables in the extreme environment of nuclear power platforms through the synergistic effect of material innovation and structural design. This invention uses low-smoke halogen-free flame-retardant ethylene propylene rubber as the insulation material, and through the synergistic effect of an EPDM / POE blend system and a ternary composite flame retardant, it ensures stable insulation performance (the volume resistivity remains at 3×10⁻⁶ after 2800 kGy extreme irradiation). 13While achieving a flame retardancy of over Ω.cm (carbonization height controlled below 0.9mm) and low-smoke halogen-free characteristics, the cable also exhibits excellent flame retardancy (carbonization height controlled below 0.9mm). The sheath material uses EVA-based low-smoke halogen-free flame-retardant polyolefin, with the addition of intumescent flame retardants and polysilazane modifiers, ensuring the cable remains crack-free at -40℃ and its bending radius can be controlled below 5 times the outer diameter, making it suitable for confined compartment layouts. The five-layer structure design of "conductor-insulation-shield-polyimide film-sheath," combined with the overlapping wrapping process of polyimide film, forms a dense radiation shield, reducing the actual radiation dose received by the insulation layer by 30%. The sheath material, combined with the low-smoke halogen-free flame-retardant cross-linked polyolefin outer sheath, enhances the cable's heat resistance and mechanical strength, thus fully meeting the stringent requirements of nuclear power platforms for high safety, high reliability, and long service life.

[0056] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A radiation-resistant cable for a nuclear power platform, characterized in that, It includes a core structure and a sheath layer. The core structure includes a conductor, an insulating layer, a shielding layer, and a polyimide film layer. The sheath layer includes an EVA sheath layer and a polyolefin sheath layer. The insulating layer is a low-smoke, halogen-free, flame-retardant ethylene propylene rubber, including EPDM rubber, ethylene-octene copolymer, aluminum hydroxide, magnesium hydroxide, lignin-based flame retardant, phenyl silicone rubber, silane coupling agent, antioxidant, crosslinking agent, and nano titanium dioxide. The polyimide film layer has a thickness of 40-60 μm.

2. The radiation-resistant cable for nuclear power platforms according to claim 1, characterized in that, The insulating layer specifically comprises the following components: 100 parts of EPDM (ethylene propylene diene monomer) rubber; 13-20 parts of ethylene-octene copolymer (POE); Aluminum hydroxide (ATH) 105-120 parts; Magnesium hydroxide (MDH) 40-60 parts; 16-22 parts of lignin-based flame retardant; Phenyl silicone rubber MPVQ 40-60 parts; 5.5-7.5 parts of silane coupling agent; Antioxidant 1.5-2.5 parts; Crosslinking agent 3.5-5 parts; 10-15 parts of nano titanium dioxide.

3. The radiation-resistant cable for nuclear power platforms according to claim 1, characterized in that, The thickness of the insulating layer is 0.6-1.2 mm, the thickness of the shielding layer is 0.4-0.8 mm, the thickness of the polyimide film layer is 40-60 μm, the thickness of the EVA sheath layer is 1.2-1.8 mm, and the thickness of the polyolefin sheath layer is 0.2-0.4 mm. And / or, the EVA sheath layer is made of EVA-based low-smoke halogen-free flame-retardant polyolefin material, with an EVA content of 30-35%.

4. The radiation-resistant cable for nuclear power platforms according to claim 1, characterized in that, The surface of the nano-titanium dioxide is modified with silane, and the particle size is 10-30 nm.

5. The radiation-resistant cable for nuclear power platforms according to claim 1, characterized in that, The lignin-based flame retardant is prepared by compounding alkali lignin and APP in a mass ratio of 1:

2.

6. The radiation-resistant cable for nuclear power platforms according to claim 1, characterized in that, The aluminum hydroxide has a particle size of 1-3 μm and a surface modified with silane; And / or, The magnesium hydroxide has a particle size of 0.5-1 μm and is surface-modified with stearic acid.

7. The radiation-resistant cable for nuclear power platforms according to claim 1, characterized in that, The shielding layer is made of tin-plated copper wire braided with a braiding density of ≥90% and a thickness of 0.5-0.6mm.

8. The radiation-resistant cable for nuclear power platforms according to claim 1, characterized in that, The polyimide film layer is processed by an overlapping wrapping process, with an overlap rate of 25-35%.

9. The radiation-resistant cable for nuclear power platforms according to claim 1, characterized in that, The method for preparing the insulating layer material includes the following steps: S1 involves mixing EPDM rubber and ethylene-octene copolymer in a set ratio, then adding an antioxidant and mixing thoroughly. S2 is blended with aluminum hydroxide, magnesium hydroxide, nano-titanium dioxide and lignin-based flame retardant in a twin-screw extruder at 180-220°C. S3 adds phenyl silicone rubber and a crosslinking agent to the mixture and continues to blend at 170-190℃ to obtain an insulating compound.

10. The radiation-resistant cable for nuclear power platforms according to claim 1, characterized in that, The EVA sheath layer comprises the following components: 100 parts EVA, 20-25 parts ethylene-butyl ether copolymer, 5-6.5 parts polysilazane modifier, 22-27 parts intumescent flame retardant, 1-2 parts flame retardant synergist, 5.5-6.5 parts nano calcium carbonate, 5.5-7.0 parts methyl vinyl silicone rubber, 0.3-0.5 parts antioxidant, and 0.7-1.2 parts lubricant; And / or, the polyolefin outer sheath layer comprises the following components: 100 parts linear low-density polyethylene, 35-38 parts EVA, 80-90 parts aluminum hydroxide, 35-45 parts magnesium hydroxide, 2.5-3.0 parts crosslinking agent, 0.5-0.9 parts antioxidant, and 0.4-0.8 parts ultraviolet absorber.

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