WO2021073272A1

WO2021073272A1 - Radiation-resistant small-cross-section high-voltage direct-current cable for nuclear power plant and manufacturing method therefor

Info

Publication number: WO2021073272A1
Application number: PCT/CN2020/111930
Authority: WO
Inventors: 金华东; 狄洪杰; 梁福才
Original assignee: 江苏上上电缆集团有限公司
Priority date: 2019-10-15
Filing date: 2020-08-27
Publication date: 2021-04-22
Also published as: CN110690008A

Abstract

A manufacturing method for a radiation-resistant small-cross-section high-voltage direct-current cable for a nuclear power plant, the nominal cross-sectional area range of a conductor of the cable is 4 to 10 mm ². The cable has a structure comprising: a conductor, an inner semi-conductive shielding layer, an insulation layer, an outer semi-conductive shielding layer, a metal shielding layer, a polyimide film layer and a sheath in sequence from inside to outside. The manufacturing steps of the cable comprise: (1) manufacturing a conductor; (2) wrapping a semi-conductive shielding material and an insulation material outside the conductor in a double-layer extruding manner; (4) wrapping a metal shielding layer outside an outer semi-conductive shielding layer; (5) wrapping a polyimide film outside a metal mesh in an overlapping wrapping manner; and (6) evenly and tightly extruding a low-smoke zero-halogen flame-retardant sheath material outside a cable core in a continuous vulcanization manner, and cooling same, the sheath material being a thermosetting low-smoke zero-halogen flame-retardant EVA mixture, and the oxygen index thereof being not less than 30%. The cable manufactured by using the method can meet design requirements and has a high pass rate.

Description

Radiation-resistant small-section high-voltage DC cable for nuclear power station and manufacturing method thereof

Technical field

The technical solution belongs to the technical field of cables for nuclear power plants, and specifically relates to a radiation-resistant small-section high-voltage direct current cable for nuclear power plants and a manufacturing method thereof.

Background technique

After the Fukushima nuclear power plant incident in Japan, the construction of domestic and foreign nuclear power plants has focused more on the guarantee of safety and redundancy. The safer and more environmentally friendly third- and fourth-generation nuclear power technologies have been widely used. The cables for nuclear power plants and the cables for nuclear power plants have ushered in new developments. development of.

The working conditions in the containment of third- and fourth-generation nuclear power plants are more severe than those of previous second-generation power plants, and the working conditions after a nuclear safety accident are even worse. For example, high-dose irradiation, high temperature, high pressure, high acid and high alkali solution, etc., in this environment, the cable needs to perform its specific function. At the same time, due to the unpredictable time of the accident, the cable also needs to have the ability to simulate thermal aging and radiation aging. That is, no matter in normal operating conditions or accident conditions, the cables can normally transmit current and signals during the 60-year life of the nuclear power plant.

In addition, for some special inspection equipment in nuclear power plants, the power input is in the form of high-voltage direct current. Laying and using in the congested and narrow space of nuclear power plant not only requires the cable to have low-smoke, halogen-free and flame-retardant properties, but also requires the cable to have aging resistance, radiation resistance, high temperature resistance, high pressure resistance, good flexibility, small outer diameter, high voltage output, etc. Features.

Summary of the invention

In order to solve the above-mentioned problems in the prior art, this technical solution proposes:

A method for manufacturing a radiation-resistant small cross-section high-voltage DC cable for nuclear power plants. The nominal cross-section of the cable conductor ranges from 4 to 10 mm ^2. The structure of the cable is: the structure of the cable is: from the inside to the outside, the conductor and the inner half are in order. Conductive shielding layer, insulating layer, outer semi-conductive shielding layer, metal shielding layer, polyimide film layer and sheath;

The manufacturing steps of the cable include:

1) Manufacturing conductor:

Choose tinned copper as the conductor material;

Bundle a high-strength aramid filament and multiple metal monofilaments made of tin-plated copper to form a conductor;

The metal monofilament is divided into multiple layers from the inside to the outside; two adjacent metal monofilaments in each metal monofilament are closely attached to each other; in two adjacent metal monofilaments, the inner and outer metal monofilaments are closely attached ; The stranding direction of the metal monofilament is left, and the stranding pitch of the metal monofilament is not more than 16 times the outer diameter after the stranding;

2) The semi-conductive shielding material and insulating material are wrapped around the conductor by double-layer extrusion and cooled to form an inner semi-conductive shielding layer and insulating layer; the semi-conductive shielding material is a semi-conductive insulating shielding material, and the insulating material is a resistive material. Fire ethylene propylene rubber insulation material;

For semi-conductive shielding material: from the feeding direction to the discharging direction, the temperature zone of the extruder is: zone one 68～73℃, zone two 76～81℃, zone three 88～94℃, zone four 96～100 ℃;

For insulating materials: from the feeding direction to the discharging direction, the temperature zone of the extruder is: 60～70℃ in the first zone, 65～75℃ in the second zone, 70～80℃ in the third zone, 75～85℃ in the fourth zone;

The first zone of the rubber extruder is the feeding section, the second and third zones are the plasticizing section, and the fourth zone is the homogenizing section;

From the feeding direction to the discharging direction, the temperature zone of the extruder's nose is: 80～90℃ in the first zone, 75～85℃ in the second zone; among them, the first zone is the nose section and the second zone is the neck section;

When insulating material is extruded, the saturated steam pressure is maintained at 1.5～1.7MPa, and the water level is controlled between 20%～30%;

3) The semi-conductive shielding tape is wrapped around the insulating layer to form an outer semi-conductive shielding layer by overlapping wrapping, the wrapping overlap rate is not less than 15%, and the thickness of the semi-conductive shielding tape is 0.12mm～0.15mm;

4) Wrap the metal shielding layer on the outer semi-conductive shielding layer;

5) The polyimide film is wrapped around the metal mesh by overlapping wrapping, the wrapping overlap rate is not less than 25%, and the thickness of the polyimide film is 0.025mm～0.05mm;

6) Adopt continuous vulcanization method to uniformly and tightly squeeze the low-smoke halogen-free flame-retardant sheath material outside the cable core and cool it;

The sheath material is a thermosetting, low-smoke, halogen-free, flame-retardant EVA mixture, and its oxygen index is not less than 30%; a sheath die sleeve is equipped on the extruder machine-reading head; the diameter of the sheath die sleeve is larger than the outer diameter of the cable core; When the material reaches the direction of discharging, the temperature distribution of each zone of the extruder is: zone 1 50～60℃, zone 2 55～65℃, zone 3 60～70℃, zone 4 65～75℃, among which, zone 1 is In the feeding section, the second and third zones are the plasticizing section, and the fourth zone is the homogenizing section;

From the feeding direction to the discharging direction, the temperature zone of the extruder head is: 65～80℃ in the first zone, 70～90℃ in the second zone, 70～80℃ in the third zone; among them, the first zone is the head section and the second zone. It is the neck section of the machine, and the three zones are the die mouth section;

During extrusion, the saturated steam pressure is maintained at 1.4～1.6MPa, and the water level is controlled at 20%～25%.

The better solution is:

In the step 2):

For semi-conductive shielding materials: the temperature zone of the extruder's body is: zone one 70°C, zone two 78°C, zone three 91°C, zone four 98°C;

For insulating materials: the temperature zone of the extruder's body is: 65°C in the first zone, 70°C in the second zone, 75°C in the third zone, and 80°C in the fourth zone; the temperature zone of the extruder's head is: 85°C in the first zone, and two Zone 80℃; the saturated steam pressure is maintained at 1.6MPa during insulation extrusion;

In the step 6): the temperature zone of the rubber extruder is: 55°C in the first zone, 60°C in the second zone, 65°C in the third zone, and 70°C in the fourth zone; ℃, 80℃ in the second zone and 75℃ in the third zone; the saturated steam pressure is maintained at 1.5MP during sheath extrusion.

In the step 3): the semi-conductive shielding tape is prefabricated from a semi-conductive shielding material, and the nominal thickness of the semi-conductive shielding tape is 0.12 mm.

In the step 4), the tin-plated metal wire is braided outside the outer semiconductive shielding layer to form a metal mesh; the braiding coverage is not less than 80%; the nominal diameter of the tin-plated metal wire is 0.12 mm to 0.20 mm. The best braided wire for tinned metal wire is 0.15mm.

It can also be said that in the step 4), the copper metal tape is wrapped over the outer semiconductive shielding layer, and the wrapping overlap rate is not less than 15%; the nominal thickness of the copper metal tape is 0.1mm-0.12mm.

In the step 5): the thickness of the polyimide film is 0.025 mm.

In the step 6), the core diameter of the sheath mold sleeve = the outer diameter of the cable core + 0.5 mm.

A radiation-resistant high-voltage DC cable with a small cross-section for nuclear power plants, which is made by the above method;

The nominal cross-section range of cable conductor is 4～10mm ² .

The structure of the cable is: from the inside to the outside, it is a conductor, an inner semi-conductive shielding layer, an insulating layer, an outer semi-conductive shielding layer, a metal shielding layer, a polyimide film layer and a sheath;

The structure of the conductor is as follows: a high-strength aramid filament (breaking strength not less than 1269N) and a plurality of tinned copper monofilament bundles constitute the conductor; the aramid filament is at the axis of the conductor; the monofilament is self-contained It is divided into multiple layers from the inside to the outside; the bundle direction of the monofilament is left; the bundle pitch of the monofilament is not more than 16 times the bundled outer diameter;

The inner semi-conductive shielding layer and the insulating layer are composed of a double-layer co-extruded semi-conductive shielding material and insulating material;

The outer semi-conductive shielding layer is composed of overlapping wrapped semi-conductive shielding tape, and the wrapping overlap rate is not less than 15%; the thickness of the semi-conductive shielding tape is 0.12mm～0.15mm;

The polyimide film layer is composed of overlapping and wrapping polyimide films; the thickness of the polyimide film is 0.025mm～0.05mm, and the wrapping overlap rate is not less than 25%.

The design principle of this technical solution is explained as follows:

A radiation-resistant, small-section, high-voltage DC cable for nuclear power plants. Its structure is as follows: a high-strength aramid wire and multiple tin-plated copper metal monofilaments are bundled to form a conductor; the conductor is extruded with semi-conductive shielding material and insulation Material; the insulating layer is wrapped with a semi-conductive shielding tape to form the wire core; the wire core is wrapped with a metal shielding layer (wire braided mesh or wrapped metal tape) and polyimide film to form a cable core; the cable core is wrapped with low-smoke and halogen-free Flame-retardant materials constitute the cable sheath. Polyimide film has the characteristics of high insulation performance, high temperature resistance, radiation resistance, and aging resistance, which improves the service life of the cable. The polyimide film has a thickness of 0.025 mm, and the wrapping overlap rate is not less than 25%.

Semi-conductive shielding material and insulating material are tightly packed on the surface of the conductor. The semi-conductive shielding material is XPB-30A. The material of the insulation layer is ethylene-propylene rubber insulation, with a life span of 60 years, nuclear radiation resistance, low smoke, halogen-free, non-toxic, flame retardant and thermosetting properties.

The insulating layer is wrapped with a layer of semi-conductive shielding tape by overlapping wrapping. The requirements of the semi-conductive shielding material are: certain conductivity, aging resistance, low smoke, halogen-free, flame retardant and other characteristics.

The outer semi-conductive shielding layer adopts a metal shielding layer (tinned metal wire is woven into a metal mesh, and the material of the metal woven mesh is required to be: high conductivity, corrosion resistance, high mechanical strength and tensile strength).

A polyimide film is used as an auxiliary insulating layer to wrap the polyimide film outside the woven wire mesh by overlapping wrapping. The polyimide film material is: high temperature resistance above 600℃, long-term use temperature range -200～300℃, high insulation performance. The main function of this layer is to assist the outer sheath layer to resist high-dose gamma and beta radiation together, and to retain a certain insulation resistance and ensure the normal transmission of current under high temperature and high pressure accident conditions.

The sheath is uniformly and tightly squeezed out of the cable core; the sheath material of the sheath is: nuclear radiation resistance, low smoke, halogen-free, non-toxic, oil-resistant, flame-retardant and thermosetting. The sheath can further block the transmission of harsh environments such as high temperature, high pressure, high dose gamma and beta rays to the insulation.

Through the specific design of materials and structure, the cable can be used on some inspection equipment of third and fourth generation nuclear power plants. It is suitable for EPR, AP1000, CAP1600, Hualong No. 1 nuclear power plant containment, outside the containment, and conventional islands. Use of specific inspection equipment in the area.

The above cables encountered problems in actual production:

Due to the small cross-section of the cable, the insulation extrusion process is very easy to break, so a new conductor structure design is adopted.

Using traditional production methods or experience to achieve three-layer co-extrusion on such a small cross-section cable is impossible to achieve, so the two-layer co-extrusion process is adopted, and then the wrapping method is used to achieve the function of insulation and shielding. This is a new type of cable that cannot be produced by the traditional production process, and the structure of the cable does not meet the conventional requirements. To this end, the present invention proposes a manufacturing method dedicated to the cable.

A method for manufacturing the above-mentioned cable for a nuclear power plant, the steps include:

1) Choose a high-strength aramid wire and multiple tinned copper metal monofilaments as the conductor material; combine a high-strength aramid wire and multiple tinned copper metal monofilaments to form a conductor: The metal monofilament is divided into multiple layers from the inside to the outside; two adjacent metal monofilaments in each layer of metal monofilament are closely attached to each other; in two adjacent layers of metal monofilament, the inner and outer metal monofilaments are closely attached The bonding direction of the metal monofilament is left; the bonding pitch of the metal monofilament is not more than 16 times the outer diameter after bonding; and a high-strength aramid filament is supplemented to improve the tensile strength of the conductor.

2) Use the double-layer co-extrusion method to wrap the semi-conductive shielding material and insulating material on the surface of the conductor, and cool it down:

In the conventional cable production process, the three-layer structure of the inner and outer semi-conductive shielding layer and insulating layer of the cable generally adopts single-layer extrusion or three-layer co-extrusion. However, this cable adopts double-layer co-extrusion + wrapping technology, the semi-conductive shielding layer can homogenize the electric field strength, and the insulating layer plays an effective electrical isolation role to ensure the good running performance of the cable.

The insulating layer can meet the following properties:

Mechanical properties: tensile strength ≥7.0MPa, elongation at break ≥200%

Flame retardant performance: meet the requirements of GB/T18380.12 for single core flame retardant

Electrical performance: 20℃ insulation resistance constant ≥10000MΩ.km

3) The semi-conductive shielding tape is wrapped around the insulation by overlapping wrapping, and the wrapping overlap rate is not less than 15%. The thickness of the semi-conductive shielding material is 0.12mm～0.15mm. This layer of semi-conductive shielding can also homogenize the electric field strength and ensure the distribution of the electric field strength of the cable.

The high-voltage resistance and partial discharge performance of the cable are greatly improved compared with the original performance after the semi-conductive shielding material is overlapped and wrapped around the insulation. The partial discharge of the cable has dropped significantly, from 50pC to 20pC. The ability of the cable to pass the DC withstand voltage is improved, and the cable can withstand the 60kV DC withstand voltage test for 15 minutes without breakdown after adding overlapping wrapping semi-conductive shielding materials.

The mechanical properties of the cable: tensile strength ≥9.0MPa, elongation at break ≥200%; flame-retardant performance: meet the requirements of GB/T18380.12 for a single cable to be flame-retardant. The cable prepared by this method can meet the design requirements, and at the same time, the pass rate can reach more than 99%.

Description of the drawings

Figure 1 is a schematic diagram of a radial cross-section of the cable of this embodiment,

In the picture: high-strength aramid 1, tinned copper metal monofilament 2, inner semi-conductive shielding layer 3, insulating layer 4, outer semi-conductive shielding layer 5, tinned metal woven mesh 6, polyimide film layer 7, Sheath 8.

Detailed ways

The technical solution is further described below in conjunction with specific embodiments as follows:

As shown in Figure 1, a radiation-resistant small cross-section high-voltage DC cable for nuclear power plants: a high-strength aramid wire and multiple tin-plated copper metal monofilaments are bundled to form a conductor; the conductor is wrapped with semi-conductive shielding materials and insulating materials Form the core; the insulating surface wraps the semi-conductive shielding material to form the outer semi-conductive shielding layer; the outer semi-conductive shielding layer uses high-speed braiding equipment to weave the metal wire into a metal mesh to wrap the surface of the core; the polyimide is wrapped by wrapping The film is wrapped on the surface of the metal mesh to form the cable core; the cable core is wrapped with a low-smoke, halogen-free flame-retardant sheath material;

The lay length of the tin-plated copper metal monofilament bundle is not more than 16 times the outer diameter of the conductor after the bundle, and a high-strength aramid wire improves the tensile strength of the conductor. The insulating layer and the inner and outer semi-conductive shielding layers can ensure the ability of the cable to withstand high voltage shocks. The insulated wire core is wrapped with metal wire woven mesh and polyimide film, which can lead the cable to a larger short-circuit current protection system in the event of a fault. At the same time, the polyimide film has high insulation performance, high temperature resistance, radiation resistance, The characteristics of aging resistance improve the service life of the cable. The sheath material requirements for cables are: nuclear radiation resistance, low smoke, halogen-free, non-toxic, oil-resistant, flame-retardant and thermosetting. The sheath is evenly and tightly squeezed out of the cable core.

Specifically, the insulating material uses ethylene-propylene rubber insulating material, the inner and outer semi-conductive shielding layers are used as auxiliary insulating layers, and the sheath material is a thermosetting EVA mixture.

The manufacturing method of the above-mentioned cable is explained as follows:

The manufacturing steps of the cable include:

1) Manufacturing conductor:

Choose tinned copper as the conductor material;

2) The semi-conductive shielding material and insulating material are wrapped around the conductor by a double-layer extrusion method, and cooled to form an inner semi-conductive shielding layer and an insulating layer; in this example, the semi-conductive shielding material is a semi-conductive insulating shielding material XPB -30A, the insulating material is flame-retardant ethylene propylene rubber insulating material;

4) Wrap the metal shielding layer on the outer semi-conductive shielding layer;

example 1:

1) Choose a high-strength aramid wire and multiple tinned copper metal monofilaments as the conductor material; combine a high-strength aramid wire and multiple tinned copper metal monofilaments to form a conductor: The metal monofilament is divided into multiple layers from the inside to the outside; two adjacent metal monofilaments in each layer of metal monofilament are closely attached to each other; in two adjacent layers of metal monofilament, the inner and outer metal monofilaments are closely attached The bonding direction of the metal monofilament is left; the bonding pitch of the metal monofilament is not more than 16 times the outer diameter after bonding; a high-strength aramid filament improves the tensile strength of the conductor.

Take the conductor radial cross-sectional area of 4mm ² to illustrate. The bundled equipment is a fully automatic stranding machine from Niehofer, Germany. The conductor structure is completed by a total of 3 layers of bundles. It is arranged in a 1+6+12 structure, and one is placed in the center. 6320 high-strength aramid yarns, 3 to 4 metal wires are placed in 18 holes in the outer layer to be bundled, the bundle direction is left, the bundle pitch is 40±3mm, the traction grade is 8, and the bundle is bundled. The pitch is not more than 16 times the outer diameter after beaming.

2) Wrap the inner semi-conductive shielding material and the ethylene-propylene rubber insulating material outside the conductor by squeezing,

Extrusion adopts the German Trest continuous vulcanization production line. When extruding the bag, the temperature zone of the extruder is: 60～70℃ in the first zone, 65～75℃ in the second zone, 70～80℃ in the third zone, and 75 in the fourth zone. ～85℃; The temperature zone of the extruder's head is: 80～90℃ in the first zone, 75～85℃ in the second zone; the saturated steam pressure is maintained at 1.5～1.7MPa during insulation extrusion;

The traction speed is 18-22m/min, and the eccentricity is not more than 20%.

3) The semi-conductive shielding tape is wrapped on the surface of the insulating layer by overlapping wrapping, and the wrapping overlap rate is not less than 15%. The thickness of the semi-conductive shielding tape is 0.12mm～0.15mm.

4) The tinned metal wire is woven into a metal mesh by weaving and covers the surface of the core. The braiding coverage is not less than 80%. The nominal diameter of tinned metal wire is 0.12mm～0.20mm.

5) The polyimide film is wrapped around the metal mesh by overlapping wrapping, and the wrapping overlap rate is not less than 25%. The thickness of the polyimide film is 0.025mm～0.05mm.

6) A layer of low-smoke halogen-free flame-retardant sheath is uniformly and tightly extruded outside the cable core by continuous vulcanization, and cooled:

The sheath adopts an extruder and is equipped with a sheath die sleeve on the machine head; the core diameter of the sheath die sleeve = the outer diameter of the cable core + 0.5mm.

From the feeding direction to the discharging direction, the temperature distribution of each zone of the extruder is: Zone 1 50～60℃, Zone 2 55～65℃, Zone 3 60～70℃, Zone 4 65～75℃, of which: 1 Zone is the feeding section, Zone 2 and Zone 3 are the plasticization section, and Zone 4 is the homogenization section;

From the feeding direction to the discharging direction, the temperature zone of the extruder head is: 65～80℃ in the first zone, 70～90℃ in the second zone, 70～80℃ in the third zone;

The sheath traction speed is 15m/min, and the eccentricity is not more than 20%.

Example 2:

The difference from Example 1 is only in step 3): the semi-conductive shielding material is extruded outside the surface of the insulated core by means of extrusion, with a nominal thickness of 1.0 mm.

Example 3:

The difference from Example 1 is only in the step 4): the copper metal tape is wrapped on the surface of the insulated wire core by overlapping wrapping, and the wrapping overlap rate is not less than 15%. The nominal thickness of copper metal strip is controlled within 0.1mm～0.12mm.

Among them, Example 1 has the highest yield rate of cables, reaching 99.3%, Example 2 reaching 98.7%, and Example 3 reaching 98.9%. It can be seen from this result that for the outer semi-conductive shielding layer, the process of wrapping the semi-conductive shielding tape in Example 1 is 0.6% higher than the process of extruding the semi-conductive shielding material in Example 2. And Example 3 also adopts the process of wrapping semi-conductive shielding tape, and its yield rate is also higher than that of Example 2.

For Examples 1 and 3, the main difference is the metal braid and the metal belt. From the bending performance of the cable, the structure of Example 1 is naturally due to the structure of Example 3. Since the cable structure has inner and outer semi-conductive shielding layers, and a metal wire mesh with a suitable structure, its shielding performance can meet the requirements of use.

The cable was prepared using the method of Example 1 for testing. In this cable, the tinned metal wire braided wire is 0.15mm, the thickness of the polyimide film is 0.025mm, and the nominal thickness of the semi-conductive shielding tape is 0.12mm.

Step 2) Parameters:

Step 6) Parameters: The temperature zone of the extruder's body is: 55°C in the first zone, 60°C in the second zone, 65°C in the third zone, and 70°C in the fourth zone; the extruder's head temperature zone is: 75°C in the first zone, The second zone is 80°C and the third zone is 75°C; the saturated steam pressure is maintained at 1.5MP when the jacket is extruded.

The test results show:

1) Good low-smoke and halogen-free performance

After a third-party type test, the finished cables have passed GB/T 17651 "Determination of Smoke Density of Cable Burning under Specific Conditions" and GB/T 17650 "Test Method for Gas Extracted from the Combustion of Cable Materials".

2) Good electrical performance

After a third-party type test, the finished cables passed the AC withstand voltage test of 21kV*5 minutes and the DC withstand voltage test of 60kV*15 minutes.

3) Nuclear radiation resistance

After a third-party type inspection, the finished cable's gamma-ray radiation dose has reached 1000kGy

4) Heat aging resistance

After a third-party type test, the finished cable has a heat-resistant aging life of more than 60 years.

5) Flame retardant properties

After a third-party type test, the finished cable meets the vertical burning test of a single cable specified in GB/T18380.12.

Claims

A method for manufacturing a radiation-resistant small cross-section high-voltage DC cable for nuclear power plants, which is characterized in that the nominal cross-sectional area of the conductor of the cable is 4-10mm 2 , and the structure of the cable is: from the inside to the outside, the conductor and the inner half are in order. Conductive shielding layer, insulating layer, outer semi-conductive shielding layer, metal shielding layer, polyimide film layer and sheath;

The manufacturing steps of the cable include:

1) Manufacturing conductor:

Choose tinned copper as the conductor material;

Bundle a high-strength aramid filament and multiple metal monofilaments made of tin-plated copper to form a conductor;

The metal monofilament is divided into multiple layers from the inside to the outside; two adjacent metal monofilaments in each metal monofilament are closely attached to each other; in two adjacent metal monofilaments, the inner and outer metal monofilaments are closely attached ; The stranding direction of the metal monofilament is left, and the stranding pitch of the metal monofilament is not more than 16 times the outer diameter after the stranding;

2) The semi-conductive shielding material and insulating material are wrapped around the conductor by double-layer extrusion and cooled to form an inner semi-conductive shielding layer and insulating layer; the semi-conductive shielding material is a semi-conductive insulating shielding material, and the insulating material is a resistive material. Fire ethylene propylene rubber insulation material;

For semi-conductive shielding material: from the feeding direction to the discharging direction, the temperature zone of the extruder is: zone one 68～73℃, zone two 76～81℃, zone three 88～94℃, zone four 96～100 ℃;

For insulating materials: from the feeding direction to the discharging direction, the temperature zone of the extruder is: 60～70℃ in the first zone, 65～75℃ in the second zone, 70～80℃ in the third zone, 75～85℃ in the fourth zone;

The first zone of the rubber extruder is the feeding section, the second and third zones are the plasticizing section, and the fourth zone is the homogenizing section;

From the feeding direction to the discharging direction, the temperature zone of the extruder's nose is: 80～90℃ in the first zone, 75～85℃ in the second zone; among them, the first zone is the nose section and the second zone is the neck section;

When insulating material is extruded, the saturated steam pressure is maintained at 1.5～1.7MPa, and the water level is controlled between 20%～30%;

3) The semi-conductive shielding tape is wrapped around the insulating layer to form an outer semi-conductive shielding layer by overlapping wrapping, the wrapping overlap rate is not less than 15%, and the thickness of the semi-conductive shielding tape is 0.12mm～0.15mm;

4) Wrap the metal shielding layer on the outer semi-conductive shielding layer;

5) The polyimide film is wrapped around the metal mesh by overlapping wrapping, the wrapping overlap rate is not less than 25%, and the thickness of the polyimide film is 0.025mm～0.05mm;

6) Adopt continuous vulcanization method to uniformly and tightly squeeze the low-smoke halogen-free flame-retardant sheath material outside the cable core and cool it;

The sheath material is a thermosetting, low-smoke, halogen-free, flame-retardant EVA mixture, and its oxygen index is not less than 30%;

Equipped with a sheath die sleeve on the reading head of the extruder; the diameter of the sheath die sleeve is larger than the outer diameter of the cable core; from the feeding to the discharging direction, the temperature distribution of each zone of the extruder is: 50-60 in one zone ℃, 55～65℃ in the second zone, 60～70℃ in the third zone, 65～75℃ in the fourth zone, among them, the first zone is the feed section, the second and third zones are the plasticization section, and the fourth zone is the homogenization section;

From the feeding direction to the discharging direction, the temperature zone of the extruder head is: 65～80℃ in the first zone, 70～90℃ in the second zone, 70～80℃ in the third zone; among them, the first zone is the head section and the second zone. It is the neck section of the machine, and the three zones are the die mouth section;

During extrusion, the saturated steam pressure is maintained at 1.4～1.6MPa, and the water level is controlled at 20%～25%.
The method for manufacturing a radiation-resistant small cross-section high-voltage DC cable for nuclear power plants according to claim 1, characterized in that in step 2):

For semi-conductive shielding materials: the temperature zone of the extruder's body is: zone one 70°C, zone two 78°C, zone three 91°C, zone four 98°C;

For insulating materials: the temperature zone of the extruder's body is: 65°C in the first zone, 70°C in the second zone, 75°C in the third zone, and 80°C in the fourth zone; the temperature zone of the extruder's head is: 85°C in the first zone, and two Zone 80℃; the saturated steam pressure is maintained at 1.6MPa during insulation extrusion;

In the step 6): the temperature zone of the rubber extruder is: 55°C in the first zone, 60°C in the second zone, 65°C in the third zone, and 70°C in the fourth zone; ℃, 80℃ in the second zone and 75℃ in the third zone; the saturated steam pressure is maintained at 1.5MP during sheath extrusion.
The method for manufacturing a radiation-resistant small cross-section high-voltage DC cable for nuclear power plants according to claim 1, characterized in that in step 3): the semi-conductive shielding tape is prefabricated from a semi-conductive shielding material, and the semi-conductive shielding tape is nominally The thickness is 0.12mm.
The method for manufacturing a radiation-resistant small cross-section high-voltage DC cable for nuclear power plants according to claim 1, characterized in that in step 4), tinned metal wires are braided outside the outer semi-conductive shielding layer to form a metal mesh; the braiding coverage is not Less than 80%; the nominal diameter of tinned metal wire is 0.12mm～0.20mm.
The method for manufacturing a radiation-resistant small cross-section high-voltage DC cable for nuclear power plants according to claim 1, characterized in that in step 4), the copper metal tape is overlapped on the outer semiconductive shielding layer, and the overlap rate of the wrapping is not less than 15%; the nominal thickness of the copper metal strip is 0.1mm～0.12mm.
The method for manufacturing a radiation-resistant small-section high-voltage DC cable for nuclear power plants according to claim 4, characterized in that in the step 4): the tinned metal wire braided wire is 0.15 mm.
The method for manufacturing a radiation-resistant small cross-section high-voltage DC cable for nuclear power plants according to claim 1, characterized in that in step 5): the thickness of the polyimide film is 0.025 mm.
The method for manufacturing a radiation-resistant small cross-section high-voltage DC cable for nuclear power plants according to claim 1, characterized in that in step 6), the core diameter of the sheath mold sleeve = the outer diameter of the cable core + 0.5 mm.
A radiation-resistant small-section high-voltage DC cable for nuclear power plants, which is characterized by being produced by any method of claims 1-8;

The nominal cross-section range of the conductor is 4～10mm 2

The structure of the cable is: from the inside to the outside, it is a conductor, an inner semi-conductive shielding layer, an insulating layer, an outer semi-conductive shielding layer, a metal shielding layer, a polyimide film layer and a sheath;

The structure of the conductor is as follows: a high-strength aramid filament and a plurality of tinned copper monofilaments are bundled to form the conductor; the aramid filament is at the axis of the conductor; the monofilament is divided into multiple layers from the inside to the outside ; The bundled direction of the monofilament is left; the bundled pitch of the monofilament is not more than 16 times of the bundled outer diameter;

The breaking strength of the aramid yarn is not less than 1269N;

The inner semi-conductive shielding layer and the insulating layer are composed of a double-layer co-extruded semi-conductive shielding material and insulating material;

The outer semi-conductive shielding layer is composed of overlapping wrapped semi-conductive shielding tape, and the wrapping overlap rate is not less than 15%; the thickness of the semi-conductive shielding tape is 0.12mm～0.15mm;

The polyimide film layer is composed of overlapping and wrapping polyimide films; the thickness of the polyimide film is 0.025mm～0.05mm, and the wrapping overlap rate is not less than 25%.