An insulated cable for nuclear reactors and a process for producing the same

Abstract

The application relates to an insulating cable for a nuclear reactor and a production process thereof, and belongs to the technical field of nuclear-grade cables. The cable at least comprises a composite core and an outer insulating sheath, and the weight part components of the insulating sheath comprise: 100 parts of methyl vinyl silicone rubber, 18-25 parts of modified lead monoxide, 15-20 parts of fumed silicon dioxide, 4.5-6 parts of hydroxyl silicone oil, 1.7-2.2 parts of heat-resistant agent, 1.2-1.8 parts of peroxide vulcanizing agent and 0.8-1.1 parts of release agent; the modified lead monoxide is made of lead monoxide loaded with an interface modifier, the interface modifier is bidirectionally connected between the silicone rubber and the lead monoxide through chelation and crosslinking, a rigid gradient transition is formed by a branched skeleton structure, a hindered phenol is introduced between the interfaces, accurate protection is carried out on weak positions in the sheath, aging between the interfaces is inhibited, and the stability of the insulating sheath in a radiation-thermal oxygen combined aging environment is improved.

Description

Technical Field

[0001] This invention belongs to the field of nuclear-grade cable technology, specifically relating to an insulated cable for nuclear reactors and its manufacturing process. Background Technology

[0002] Compared to ordinary industrial environments, cables in nuclear facilities may be subjected to higher temperatures, gamma or X-ray radiation, oxidizing atmospheres, and periodic mechanical disturbances during their service life. Furthermore, maintenance and replacement are not only difficult but also increase downtime and personnel exposure risks. Therefore, maintaining sheath integrity, insulation stability, and mechanical flexibility throughout the cable's design life is crucial for ensuring the safe and stable operation of the nuclear reactor.

[0003] The sheath, located on the outermost layer of the cable, serves to protect against external heat, moisture, radiation, and mechanical damage. Silicone rubber, with its Si-O-Si main chain structure, possesses good heat resistance, ozone resistance, electrical insulation, and low-temperature flexibility. Despite its relatively high cost, it remains an important candidate material for the sheath of high-temperature cables used in nuclear power plants. However, the oxidation process of silicone rubber accelerates significantly under long-term radiation and thermo-oxidative environments, leading to a significant decrease in the strength and toughness of the sheath. Once the sheath cracks, heat, moisture, and radiation can more easily penetrate into the cable, reducing the service life of the insulation layer.

[0004] To reduce radiation penetration into the cable interior, high atomic number fillers such as lead, bismuth, and tungsten can be added to the silicone rubber sheath. Among these, lead monoxide has advantages such as high density, strong mass attenuation capability for X-rays and gamma rays, and the ability to be dispersed into powder. When ionized photons enter the lead monoxide-containing sheath, they lose energy through photoelectric absorption and Compton scattering. However, research has found that ionizing radiation can also generate secondary electrons and local energy deposition near high atomic number particles. Especially at lower photon energies, the polymer near the particle surface is more easily concentrated. As a result, the original interface defects and local radiation oxidation are superimposed, often manifesting as a sudden increase in crosslinking density around lead monoxide and preferential initiation of microcracks, which further develops into particle debonding and sheath surface pulverization. Consequently, the introduction of lead monoxide does not significantly improve the stability of silicone rubber. Summary of the Invention

[0005] In order to solve the technical problems mentioned in the background art, the purpose of this invention is to provide an insulated cable for nuclear reactors and its manufacturing process.

[0006] The objective of this invention can be achieved through the following technical solutions: An insulated cable for nuclear reactors includes at least a composite core and an insulating sheath covering the outside of the composite core; the insulating sheath is made of vulcanized silicone rubber, which includes the following components by weight: 100 parts of methyl vinyl silicone rubber, 18-25 parts of modified lead monoxide, 15-20 parts of fumed silica, 4.5-6 parts of hydroxyl silicone oil, 1.7-2.2 parts of heat resistant agent, 1.2-1.8 parts of peroxide vulcanizing agent, and 0.8-1.1 parts of release agent.

[0007] The specific surface area of ​​fumed silica is preferably 150-250 m² / g. 2 / g, used to reinforce the sheath; hydroxyl silicone oil as a structure control agent to reduce the structuring of fumed silica during the mixing process; the preferred peroxide vulcanizing agent is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0008] The modified lead monoxide is prepared by chelating and loading activated lead monoxide with an interface modifier. The average particle size of the lead monoxide is preferably 1-3 μm, which provides a high specific surface area while avoiding the problems of difficult safe handling and severe sticking of nanoparticles. The activation treatment preferably employs a combination of vacuum drying and oxygen plasma treatment. Vacuum drying removes adsorbed water and low-molecular-weight contaminants from the lead monoxide surface, while oxygen plasma cleans the surface and increases its surface energy, exposing more coordinatingly unsaturated lead sites. This facilitates the proximity and stable adsorption of the tertiary amine coordination centers of the interface modifier.

[0009] The preparation method of the interface modifier is as follows: Step A1, Synthesis of the hydroxyl-terminated branched intermediate: Tetrahydroxypropylethylenediamine, triethylamine, and anhydrous tetrahydrofuran were premixed and cooled to below 5°C under dry nitrogen protection. Methylvinyldichlorosilane was diluted with anhydrous tetrahydrofuran and slowly added dropwise, with the system temperature controlled not to exceed 10°C during the addition. After the addition was completed, the temperature was raised to 35-45°C and reacted for 5-8 hours. After the reaction was completed, the triethylamine hydrochloride was removed by filtration and the solvent was removed under reduced pressure to obtain the hydroxyl-terminated branched intermediate.

[0010] Furthermore, the molar ratio of tetrahydroxypropylethylenediamine to methylvinyldichlorosilane is 2-2.2:1; excess tetrahydroxypropylethylenediamine is substituted with methylvinyldichlorosilane to form branched compounds with hydroxyl groups at the ends.

[0011] Step A2, Synthesis of Interface Modifier: 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid was dissolved in anhydrous toluene, thionyl chloride and N,N-dimethylformamide were added, and the mixture was reacted at 50-65℃ for 4-6 h under dry nitrogen protection. Excess thionyl chloride was removed under reduced pressure, and after cooling, a mixed solution of hydroxyl-terminated branched intermediate, triethylamine, 4-dimethylaminopyridine and anhydrous tetrahydrofuran was slowly added. The mixture was then reacted at 60-75℃ for 12-18 h. After the reaction was completed, the mixture was filtered to remove salts. The filtrate was concentrated under reduced pressure and dissolved in a mixture of anhydrous ethyl acetate and anhydrous tetrahydrofuran. The product was purified by passing it through a neutral alumina short column, the solvent was removed under reduced pressure, and the product was dried under vacuum to obtain the interface modifier.

[0012] Furthermore, the molar ratio of the hydroxyl content of the hydroxyl-terminated branched intermediate, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, and thionyl chloride is 1:1.05-1.1:1.4-1.8; after activation by thionyl chloride, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid is substituted with the hydroxyl-terminated branched intermediate to introduce a terminally hindered phenolic structure.

[0013] The modified lead monoxide is prepared by dissolving an interface modifier in ethyl acetate, adding activated lead monoxide for dispersion, stirring and loading at 50-60℃, centrifuging to separate the precipitate, and then drying to obtain modified lead monoxide.

[0014] Preferably, the loading of the interface modifier is 2.5-3.5 wt% of the activated lead monoxide. If the loading is below this range, the surface coverage will be insufficient, and if the loading is above this range, the free modifier will increase, which may affect the sulfidation and electrical properties.

[0015] A manufacturing process for an insulated cable used in a nuclear reactor includes the following steps: Step S1: Add methyl vinyl silicone rubber to a mixer for plasticizing, add fumed silica and hydroxyl silicone oil and mix at 60-80℃ for the first time, then add modified lead monoxide and heat resistant agent and mix at 90-100℃ for the second time. After that, cool the rubber compound to below 50℃, add peroxide vulcanizing agent and release agent in a two-roll mill, and obtain silicone rubber sheath material after thin passing. Step S2: Extrude the silicone rubber sheath material onto the outside of the composite core at an extrusion temperature of 80-90℃. After extrusion, continuously vulcanize through a hot air vulcanization channel at 220-240℃, and then vulcanize again at 175-190℃. After cooling and inspection, the insulated cable for nuclear reactors is obtained.

[0016] The beneficial effects of this invention are: This invention is based on a lead monoxide-silicone rubber radiation-resistant sheath system. It introduces an interface modifier to treat lead monoxide, establishing a bidirectional connection between lead monoxide and silicone rubber through multi-point chelation-vulcanization crosslinking. Specifically, multiple tertiary amine nitrogen atoms in the interface modifier possess lone pairs of electrons, allowing them to simultaneously coordinate with lead sites on the lead monoxide surface. The vinyl groups retained at the molecular center co-crosslink with methyl vinyl silicone rubber during peroxide vulcanization, thus creating advantages distinct from existing interface materials. Lead monoxide particles no longer exist solely in the sheath through physical encapsulation. Under this bidirectional connection, the interfacial voids and particle shedding are significantly reduced after irradiation and thermal cycling. Furthermore, the interface modifier introduces a hindered phenolic structure into the interface between silicone rubber and lead monoxide. The hindered phenol can provide hydrogen atoms to peroxide free radicals, converting the active free radicals into relatively stable products and terminating the chain reaction. It can precisely act on the weak points in the sheath to provide targeted protection, inhibit the aging between interfaces, and alleviate the debonding of lead monoxide. In addition, the interface modifier is constructed by a substitution reaction of tetrahydroxypropylethylenediamine and methylvinyldichlorosilane to form a branched skeleton structure, which forms a gradient transition layer between the rigid lead monoxide and the silicone rubber crosslinking network, effectively transferring and dispersing stress, enhancing the silicone rubber while reducing toughness loss, and mitigating the debonding of lead monoxide particles through stress dispersion. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1: Preparation of insulated cables for nuclear reactors. The specific implementation process is as follows: 1) Preparation of interface modifiers Step A1: Add 0.1 mol tetrahydroxypropylethylenediamine, 0.1 mol triethylamine, and 300 mL anhydrous tetrahydrofuran to a dry reaction flask and stir. Purge with dry nitrogen gas for protection and cool in an ice-water bath until the temperature drops below 5°C. Dissolve 0.05 mol methylvinyldichlorosilane in 100 mL anhydrous tetrahydrofuran and add it slowly dropwise, controlling the temperature not to exceed 10°C during the addition process. After complete addition, stir the reaction in a constant temperature water bath at 35°C for 8 hours. After the reaction is complete, filter the mixture, wash the filter cake with anhydrous tetrahydrofuran, combine the filtrates, and remove the solvent tetrahydrofuran under reduced pressure to obtain a hydroxyl-terminated branched intermediate with a hydroxyl value of 485 mg KOH / g.

[0019] Step A2: Add 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid to a dry reaction flask, add 350 mL of anhydrous toluene at room temperature and stir to dissolve. Then add thionyl chloride and 50 mL of N,N-dimethylformamide, purge with dry nitrogen for protection and heat to 50 °C for 6 h. After the reaction is complete, reduce the pressure to 10 kPa and remove excess thionyl chloride by rotary evaporation, then cool to room temperature. Take the hydroxyl-terminated intermediate prepared above, add triethylamine with an equimolar amount of hydroxyl content and 0.2 molar amounts of 4-dimethylaminopyridine, and simultaneously add 250 mL of anhydrous tetrahydrofuran and stir to dissolve. Slowly add the mixture to the reaction solution, and after complete addition, heat to 60 °C and react for 18 h. During the reaction, the obtained hydroxyl-terminated intermediate is used as the reference value. The hydroxyl content was quantified, and the hydroxyl content of the hydroxyl-terminated intermediate and the molar ratio of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid and thionyl chloride were controlled at 1:1.05:1.4. After the reaction was completed, the triethylamine hydrochloride was removed by filtration, and the filtrate was concentrated under reduced pressure to about one-third of its original volume. It was dissolved in a mixture of anhydrous ethyl acetate / anhydrous tetrahydrofuran at a volume ratio of 4:1 and purified by passing it through a neutral alumina short column to remove residual acid-binding agents, catalysts and acidic impurities. The product was collected and the solvent was removed under reduced pressure. After vacuum drying, the interface modifier was obtained.

[0020] 2) Preparation of modified lead monoxide Lead monoxide (all using ultrafine powder with D50 of 1.2 μm) was vacuum dried at 120℃ for 2 h, with a spreading thickness not exceeding 3 mm. It was then plasma-treated for 15 min under oxygen conditions of 100 W and 60 Pa to obtain activated lead monoxide. An interface modifier was dissolved in ethyl acetate to prepare a 1 wt% solution. The activated lead monoxide was added at a solid-liquid mass ratio of 1:3.2 and ultrasonically dispersed for 5 min. The solution was then heated to 50℃ and stirred for 3 h. After centrifugation to separate the precipitate, it was dried to obtain modified lead monoxide with an interface modifier loading of 3.2 wt%.

[0021] 3) Preparation of insulated cables for nuclear reactors Ingredients: By weight, 100 parts of methyl vinyl silicone rubber (using raw rubber with a molecular weight of approximately 600,000 and a vinyl molar fraction of 0.12%); 18 parts of modified lead monoxide (prepared as in the examples); and 15 parts of fumed silica (with a specific surface area of ​​approximately 200 m²). 2 / g of raw materials; 6 parts of hydroxyl silicone oil, with a hydroxyl mass fraction of about 8%; 1.7 parts of heat resistant agent, using nano iron oxide; 1.2 parts of peroxide vulcanizing agent, using 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (i.e., bis(2,5-dimethyl)hexane); 0.8 parts of release agent, using zinc stearate.

[0022] Step S1: Add methyl vinyl silicone rubber to a mixer for plasticizing, add fumed silica and hydroxyl silicone oil and mix at 70°C for 50 minutes, then add modified lead monoxide and heat resistant agent and mix at 90°C for 20 minutes. After the rubber compound is cooled to 50°C, add peroxide vulcanizing agent and release agent in a two-roll mill and pass through the mill 4 times to obtain silicone rubber sheath material. Step S2: Select a general four-core composite core (copper stranded wire as conductor, mica tape wrapped around the outside, and plastic insulation layer extruded on the surface to make four insulated cores; the four insulated cores are cabled with glass fiber filler rope, and glass fiber tape is wrapped around the outside). Extrude the sheath material onto the outside of the composite core at 80°C using a cold-feed extruder. After extrusion, continuously vulcanize through a 220°C hot air vulcanization channel for 8 minutes, and then vulcanize again at 175°C for 3.5 hours. After cooling and inspection, the insulated cable for nuclear reactors is obtained.

[0023] Example 2: Preparation of insulated cables for nuclear reactors. The specific implementation process is as follows: 1) Preparation of interface modifiers Step A1: Add 0.11 mol tetrahydroxypropylethylenediamine, 0.15 mol triethylamine, and 400 mL anhydrous tetrahydrofuran to a dry reaction flask and stir. Purge with dry nitrogen gas for protection and cool in an ice-water bath until the temperature drops below 5°C. Dissolve 0.05 mol methylvinyldichlorosilane in 100 mL anhydrous tetrahydrofuran and add it slowly dropwise, controlling the temperature not to exceed 10°C during the addition process. After complete addition, stir the reaction in a constant temperature water bath at 45°C for 5 hours. After the reaction is complete, filter the mixture, wash the filter cake with anhydrous tetrahydrofuran, combine the filtrates, and remove the solvent tetrahydrofuran under reduced pressure to obtain a hydroxyl-terminated branched intermediate with a hydroxyl value of 530 mg KOH / g.

[0024] Step A2: Add 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid to a dry reaction flask, add 420 mL of anhydrous toluene at room temperature and stir to dissolve. Then add thionyl chloride and 60 mL of N,N-dimethylformamide, purge with dry nitrogen for protection and heat to 65 °C for 4 h. After the reaction is complete, reduce the pressure to 10 kPa and remove excess thionyl chloride by rotary evaporation, then cool to room temperature. Take the hydroxyl-terminated intermediate prepared above, add triethylamine with an equimolar amount of hydroxyl content and 0.3 molar amounts of 4-dimethylaminopyridine, and simultaneously add 300 mL of anhydrous tetrahydrofuran and stir to dissolve. Slowly add the mixture to the reaction solution, and after complete addition, heat to 75 °C and react for 12 h. During the reaction, the obtained hydroxyl-terminated intermediate is used as the reference value. The hydroxyl content was quantified, and the hydroxyl content of the hydroxyl-terminated intermediate and the molar ratio of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid and thionyl chloride were controlled to be 1:1.1:1.8. After the reaction was completed, the triethylamine hydrochloride was removed by filtration, and the filtrate was concentrated under reduced pressure to about one-third of its original volume. It was dissolved in a mixture of anhydrous ethyl acetate / anhydrous tetrahydrofuran at a volume ratio of 4:1 and purified by passing it through a neutral alumina short column to remove residual acid-binding agents, catalysts and acidic impurities. The product was collected and the solvent was removed under reduced pressure. After vacuum drying, the interface modifier was obtained.

[0025] 2) Preparation of modified lead monoxide Lead monoxide (all using ultrafine powder with D50 of 1.2 μm) was vacuum dried at 120℃ for 2 h, with a spreading thickness not exceeding 3 mm. It was then plasma-treated for 15 min under oxygen conditions of 100 W and 60 Pa to obtain activated lead monoxide. An interface modifier was dissolved in ethyl acetate to prepare a 1 wt% solution. The activated lead monoxide was added at a solid-liquid mass ratio of 1:4.5 and ultrasonically dispersed for 5 min. The solution was then heated to 60℃ and stirred for 2 h. After centrifugation to separate the precipitate, the solution was dried to obtain modified lead monoxide with an interface modifier loading of 2.8 wt%.

[0026] 3) Preparation of insulated cables for nuclear reactors Ingredients: By weight, 100 parts methyl vinyl silicone rubber, 22 parts modified lead monoxide, 18 parts fumed silica, 5.2 parts hydroxyl silicone oil, 2.0 parts heat resistant agent, 1.5 parts peroxide vulcanizing agent, and 0.9 parts release agent.

[0027] Step S1: Add methyl vinyl silicone rubber to a mixer for plasticizing, add fumed silica and hydroxyl silicone oil and mix at 80°C for 30 minutes, then add modified lead monoxide and heat resistant agent and mix at 100°C for 15 minutes. After the rubber compound is cooled to 50°C, add peroxide vulcanizing agent and release agent in a two-roll mill and pass through 5 times to obtain silicone rubber sheath material. Step S2: Select a general four-core composite wire core, and use a cold-feed extruder to extrude the sheath material onto the outside of the composite wire core at 80-90℃. After extrusion, continuously vulcanize through a 240℃ hot air vulcanization channel for 5 minutes, and then vulcanize again at 190℃ for 3 hours. After cooling and inspection, the insulated cable for nuclear reactors is obtained.

[0028] Example 3: Preparation of insulated cables for nuclear reactors. The specific implementation process is as follows: 1) Preparation of interface modifiers Step A1: Add 0.105 mol tetrahydroxypropylethylenediamine, 0.12 mol triethylamine, and 350 mL anhydrous tetrahydrofuran to a dry reaction flask and stir. Purge with dry nitrogen gas for protection and simultaneously cool using an ice-water bath until the temperature drops below 5°C. Dissolve 0.05 mol methylvinyldichlorosilane in 100 mL anhydrous tetrahydrofuran and slowly add it dropwise, controlling the temperature not to exceed 10°C during the addition process. After complete addition, stir the reaction at a constant temperature of 40°C for 7 hours. After the reaction is complete, filter the mixture, wash the filter cake with anhydrous tetrahydrofuran, combine the filtrates, and remove the solvent tetrahydrofuran under reduced pressure to obtain a hydroxyl-terminated branched intermediate with a hydroxyl value of 515 mg KOH / g.

[0029] Step A2: Add 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid to a dry reaction flask, add 380 mL of anhydrous toluene at room temperature and stir to dissolve. Then add thionyl chloride and 55 mL of N,N-dimethylformamide, purge with dry nitrogen for protection and heat to 560 °C for 5 h. After the reaction is complete, reduce the pressure to 10 kPa and remove excess thionyl chloride by rotary evaporation, then cool to room temperature. Take the hydroxyl-terminated intermediate prepared above, add triethylamine with an equimolar amount of hydroxyl content and 0.2 molar amounts of 4-dimethylaminopyridine, and simultaneously add 300 mL of anhydrous tetrahydrofuran and stir to dissolve. Slowly add the mixture to the reaction solution, and after complete addition, heat to 65 °C and react for 15 h. During the reaction, use the obtained hydroxyl-terminated intermediate as the control. The hydroxyl content was quantified, and the hydroxyl content of the hydroxyl-terminated intermediate and the molar ratio of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid and thionyl chloride were controlled to be 1:1.1:1.6. After the reaction was completed, the triethylamine hydrochloride was removed by filtration, and the filtrate was concentrated under reduced pressure to about one-third of its original volume. It was dissolved in a mixture of anhydrous ethyl acetate / anhydrous tetrahydrofuran at a volume ratio of 4:1 and purified by a neutral alumina short column to remove residual acid-binding agent, catalyst and acidic impurities. The product was collected and the solvent was removed under reduced pressure. After vacuum drying, the interface modifier was obtained.

[0030] 2) Preparation of modified lead monoxide Lead monoxide (all using ultrafine powder with D50 of 1.2 μm) was vacuum dried at 120℃ for 2 h, with a spreading thickness not exceeding 3 mm. It was then plasma-treated for 15 min under oxygen conditions of 100 W and 60 Pa to obtain activated lead monoxide. An interface modifier was dissolved in ethyl acetate to prepare a 1 wt% solution. The activated lead monoxide was added at a solid-liquid mass ratio of 1:4 and ultrasonically dispersed for 5 min. The solution was then heated to 55℃ and stirred for 2.5 h. After centrifugation to separate the precipitate, the solution was dried to obtain modified lead monoxide with an interface modifier loading of 2.5 wt%.

[0031] 3) Preparation of insulated cables for nuclear reactors Ingredients: By weight, 100 parts methyl vinyl silicone rubber, 25 parts modified lead monoxide, 20 parts fumed silica, 4.5 parts hydroxyl silicone oil, 2.2 parts heat resistant agent, 1.8 parts peroxide vulcanizing agent, and 1.1 parts release agent.

[0032] Step S1: Add methyl vinyl silicone rubber to a mixer for plasticizing, add fumed silica and hydroxyl silicone oil and mix at 80°C for 40 minutes, then add modified lead monoxide and heat resistant agent and mix at 100°C for 18 minutes. After the rubber compound is cooled to 50°C, add peroxide vulcanizing agent and release agent to a two-roll mill and pass through it 5 times to obtain silicone rubber sheath material. Step S2: Select a general four-core composite wire core, and use a cold-feed extruder to extrude the sheath material onto the outside of the composite wire core at 90°C. After extrusion, continuously vulcanize through a 230°C hot air vulcanization channel for 6 minutes, and then vulcanize again at 185°C for 3.5 hours. After cooling and inspection, the insulated cable for nuclear reactors is obtained.

[0033] Comparative Example 1: Silicone rubber sheath material and cable were prepared according to Example 2. Modified lead monoxide was not added to the sheath material, but 0.18 parts of antioxidant 1010 were added. The remaining components and processes were kept the same.

[0034] Comparative Example 2: Silicone rubber sheath material and cable were prepared in accordance with Example 2, but the modified lead monoxide was replaced with unmodified lead monoxide of equal mass and particle size, and 0.18 parts of antioxidant 1010 were added. The remaining components and processes were kept the same.

[0035] Comparative Example 3: Cables were prepared according to Example 2, but the interface modifier was replaced with vinyltriethoxysilane, and activated lead monoxide was treated with 3% of the mass of lead monoxide. 0.18 parts of antioxidant 1010 were added, and the remaining components and processes remained the same.

[0036] To verify the protective function of the cable insulation sheath, samples were taken and the following tests were performed: Radiation-thermal composite aging: Initial tensile strength and elongation at break were tested according to GB / T 2951.11-2008 standard. The irradiation process followed IEC 60544-2:2012, using 60Co gamma rays in air at a dose rate of 1 kGy / h to a cumulative dose of 800 kGy. After irradiation, thermal aging was performed at 150℃ for 168 h according to GB / T 2951.12-2008, followed by room temperature adjustment for 24 h, and then tested again. The retention rates of tensile strength and elongation at break were calculated as the ratios of the values ​​after composite aging to the initial values, respectively. Specific test results are shown in Table 1. Table 1

[0037] As can be seen from the test results in Table 1, the modified lead monoxide exhibits higher strength and toughness compared to lead monoxide introduced directly or through surface treatment. This may be related to the synergistic effect of crosslinking and toughening of the branched structure by the interface modifier. Furthermore, after radiation and heat aging treatment, the performance index retention rate is significantly higher than that of the comparative sample, demonstrating excellent stability.

[0038] Interface stability: The composite aged sheath sample was subjected to liquid nitrogen embrittlement and gold sputtering. The interface around lead monoxide was observed using a scanning electron microscope. The ratio of the area of ​​voids around the particles to the projected area of ​​the particles was calculated through image analysis and recorded as the interface porosity. Another 2.0 g of composite aged sample was placed in 100 mL of anhydrous ethanol and sonicated at 200 W for 30 min. After filtration and drying, the mass loss related to particle detachment was calculated based on the weight loss. The specific test results are shown in Table 2. Table 2

[0039] As can be seen from the test results in Table 2, after radiation-thermal-oxidative composite aging, the sheath in the comparative example showed high interfacial porosity, high ultrasonic quality loss, and obvious particle aging and debonding.

[0040] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0041] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. An insulated cable for a nuclear reactor, comprising at least a composite core and an insulating sheath covering the outside of the composite core, characterized in that, The insulating sheath is made of vulcanized silicone rubber, with 18-25 phr of modified lead monoxide added to its components; specifically: Modified lead monoxide is prepared by chelating and loading activated lead monoxide with an interface modifier. The preparation method of the interface modifier is as follows: Step A1: Tetrahydroxypropylethylenediamine, triethylamine and anhydrous tetrahydrofuran are premixed and cooled to below 5°C under dry nitrogen protection. A diluted solution of methyl vinyl dichlorosilane is slowly added while controlling the system temperature to be no higher than 10°C. After addition, the mixture is reacted at 35-45°C for 5-8 hours. After purification, a hydroxyl-terminated branched intermediate is obtained. Step A2: Dissolve 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid in anhydrous toluene, add thionyl chloride and N,N-dimethylformamide, and react at 50-65℃ for 4-6 h under dry nitrogen protection. Remove excess thionyl chloride, cool, and slowly add a mixed solution of hydroxyl-terminated branched intermediate, triethylamine, 4-dimethylaminopyridine, and anhydrous tetrahydrofuran. Then react at 60-75℃ for 12-18 h. After purification, obtain the interface modifier.

2. The insulated cable for a nuclear reactor according to claim 1, characterized in that, The molar ratio of tetrahydroxypropylethylenediamine to methylvinyldichlorosilane is 2-2.2:

1.

3. An insulated cable for a nuclear reactor according to claim 2, characterized in that, The hydroxyl content of the hydroxyl-terminated intermediate, the molar ratio of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid and thionyl chloride is 1:1.05-1.1:1.4-1.

8.

4. An insulated cable for a nuclear reactor according to claim 3, characterized in that, Activated lead monoxide is prepared by sequentially vacuum drying and oxygen plasma treatment of lead monoxide; the loading of interface modifier in modified lead monoxide is 2.5-3.5 wt%.

5. An insulated cable for a nuclear reactor according to claim 4, characterized in that, The average particle size of lead monoxide is 1-3 μm.

6. An insulated cable for a nuclear reactor according to claim 4, characterized in that, The insulating sheath comprises the following components by weight: 100 parts methyl vinyl silicone rubber, 18-25 parts modified lead monoxide, 15-20 parts fumed silica, 4.5-6 parts hydroxyl silicone oil, 1.7-2.2 parts heat resistant agent, 1.2-1.8 parts peroxide vulcanizing agent, and 0.8-1.1 parts release agent.

7. A manufacturing process for an insulated cable for a nuclear reactor according to any one of claims 1-6, characterized in that, Includes the following steps: Step S1: Methyl vinyl silicone rubber is plasticized, fumed silica and hydroxyl silicone oil are added for a first mixing, modified lead monoxide and heat resistant agent are added for a second mixing, the mixed rubber compound is cooled to below 50°C, and then peroxide vulcanizing agent and mold release agent are added for open mixing. After thin passing, silicone rubber sheath material is obtained. Step S2: Extrude the silicone rubber sheath material onto the outside of the composite core, and perform two vulcanization molding processes to form an insulating sheath. After cooling and inspection, the insulated cable for nuclear reactors is obtained.

8. The manufacturing process of an insulated cable for a nuclear reactor according to claim 7, characterized in that, In the two-stage vulcanization process, the temperature of the first vulcanization is 220-240℃, and the temperature of the second vulcanization is 175-190℃.

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