JP2006127858A - Radiation-resistant cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation-resistant cable with excellent flexibility and low cost, even if it is a cable with large outer diameter of exceeding ϕ5mm. <P>SOLUTION: The radiation-resistant cable 10, exposed to radioactive rays of 10 MGy or more, has a plurality of wire cores 13 each with an insulation coating 12 of polyether ether ketone around a conductor 11 twisted to form a stranded wire 14, around which 14 an outer covering 19 structured of metal braided wires is fitted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radiation-resistant cable used in an environment exposed to radiation of 10 MGy or more.

  When a high-energy proton beam strikes the atomic nucleus that constitutes a material, the atomic nucleus breaks, generating secondary particles such as neutrons, protons, pions, neutrinos, and muons. Using a powerful neutron beam generated in this way, the nuclear transmutation method shortens long-lived nuclei with a long half-life to process radioactive waste, and unknown fine structures of proteins and enzymes. There is a plan to elucidate and use it for the development of pharmaceuticals and foods.

  The core facility of this project is a proton accelerator for generating high-intensity and high-energy proton beams. This proton accelerator is usually composed of a linear accelerator (linac) and a synchrotron.

  In the synchrotron, in order to accelerate protons, it is necessary to make the inside of a tubular beam duct, which is a passage of protons, a vacuum state. As this evacuation means, a vacuum pump, particularly a turbo molecular pump (hereinafter referred to as TMP) that is clean and can obtain a high degree of vacuum is used. For example, as shown in FIG. 5, the TMP includes a TMP main body 51, a TMP controller 52, a TMP repeater 53, and a connector box unit 54. The TMP controller 52 and the TMP repeater 53, and the TMP controller 52 and the connector box unit 54 are connected via connection cables 55a and 55b, respectively. Further, the TMP main body 51 and the TMP repeater 53, and the TMP main body 51 and the connector box section 54 are connected via connection cables 56a and 56b, respectively. Each wire core group (not shown) of the connection cables 56 a and 56 b is electrically connected to each wire core group 58 a and 58 b in the internal wiring of the TMP main body 51. The TMP main body 51 and the connection cables 56a and 56b are installed inside the synchrotron main tunnel (shaded area in FIG. 5) 58 surrounded by the shielding wall 57. The interior 58 of the synchrotron main tunnel is a radiation region.

  The connection cables 55a, 55b and 56a, 56b are provided with an electromagnetic shielding layer composed of a braid of a good conductor around a stranded wire portion obtained by twisting a plurality of wire cores having an insulator coating around the conductor. An exterior (sheath) is provided outside the shielding layer. The connection cables 55a and 55b are not required to have high radiation resistance because they are not exposed to high-level radiation, and both the insulation of the wire core and the exterior of the cable are made of a polyethylene-based material (hereinafter referred to as PE). The

  On the other hand, the connection cables 56a and 56b are required to have high radiation resistance because they are exposed to high-level radiation. Further, the connection cables 56a and 56b are required to have high flame resistance. For example, high flame retardancy is required to pass a vertical tray combustion test based on JIS C 3521 (IEEE383). Further, it is important that the connection cables 56a and 56b do not contain a halogen element (halogen-free) like polyvinyl chloride (PVC) in order to prevent generation of halogen gas or dioxin during combustion.

  As a coaxial cable with excellent radiation resistance and heat resistance (flame resistance), the insulation coating is composed of polyimide extrusion coating, and the sheath (exterior) is extrusion coating of polyimide or polyetheretherketone (hereinafter referred to as PEEK) There has been proposed a heat- and radiation-resistant cable composed of (see, for example, Patent Document 1). Moreover, as a coaxial cable excellent in heat resistance (flame resistance), there is an insulated wire in which an insulator coating made of PEEK is provided on a conductor (see, for example, Patent Document 2).

JP-A-7-130219 JP-A-5-225832

  By the way, in the case of a large-diameter cable whose outer diameter exceeds φ5 mm, there is a problem that it is very difficult to form a sheath by extrusion coating of polyimide or PEEK. In this case, although a sheath can be formed by winding a tape material made of polyimide (or PEEK), there is a problem that flexibility is deteriorated and cost is increased.

  The object of the present invention created in view of the above circumstances is to provide a radiation-resistant cable that has good flexibility and is inexpensive even for a large-diameter cable having an outer diameter exceeding 5 mm. is there.

  In order to achieve the above object, the radiation-resistant cable according to the present invention is a cable that is exposed to radiation of 10 MGy or more, and forms a wire core having a polyether ether ketone insulator coating around a conductor, and the wire A sheath (sheath) composed of a metal braided wire is provided around the core.

  The radiation-resistant cable according to the present invention is a cable that is exposed to radiation of 10 MGy or more, and a plurality of wire cores having a polyether ether ketone insulator coating are twisted around a conductor to form a stranded portion. The outer sheath (sheath) formed of a metal braided wire is provided around the stranded portion.

  Furthermore, the radiation-resistant cable according to the present invention is a cable exposed to radiation of 10 MGy or more, and forms a twisted pair by twisting a wire core having a polyether ether ketone insulator coating around a conductor. , A plurality of types of twisted wire units are formed using at least one pair of twisted wires, each twisted wire unit is bundled to form a twisted wire portion, and a metal braided wire is formed around the twisted wire portion. The exterior (sheath) is provided.

  Here, the exterior (sheath) is preferably composed of a braided wire made of stainless steel.

  Further, the specific gravity of the polyether ether ketone constituting the insulator coating is preferably 1.28 or more.

  Furthermore, it is preferable to provide an inclusion of a polyimide-based material inside the exterior and / or in the stranded portion, and a more preferable inclusion is an aramid fiber.

  Moreover, you may provide the insulation protective layer comprised with a polyimide-type material, for example, a polyimide tape etc., or a polyether ether ketone-type material, for example, a polyether ether ketone tape, around the exterior (sheath).

  ADVANTAGE OF THE INVENTION According to this invention, the outstanding effect that a radiation resistant cable which satisfies radiation resistance, high flame retardance, and halogen-free, and has favorable flexibility can be obtained.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of the invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a cross-sectional view of a radiation-resistant cable according to a preferred embodiment of the present invention.

  As shown in FIG. 1, the radiation resistant cable 10 according to the present embodiment is a cable that is exposed to radiation of 10 MGy or more, preferably less than 10 to 30 MGy, more preferably 10 to 20 MGy. Specifically, a wire core 13 having a PEEK insulator coating 12 is formed around the conductor 11, an electromagnetic shielding layer 17 composed of a braid of a good conductor is provided around the wire core 13, and the electromagnetic shielding is performed. An outer sheath (sheath) 19 composed of a metal braided wire is provided around the layer 17.

  More specifically, the radiation resistant cable 10 has a stranded wire portion 14 in which a stranded wire body formed by twisting a plurality of wire cores 13 (three in FIG. 1) is fixed with a polyimide tape 15, and the twisted wire portion 14. An electromagnetic shielding layer 17, an insulating layer 18 made of polyimide tape, and an exterior 19 are provided around the wire portion 14 in this order. Moreover, the inclusion 16 of a polyimide-type material is provided inside the stranded portion 14 (the gap between the stranded wire body and the polyimide tape 15).

  The sheath 19 is a sheath and is preferably not a magnetic shielding layer but a braided wire made of stainless steel that is robust and excellent in corrosion resistance. As the stainless steel, SUS316 (JIS standard) is preferable, and SUS316 material for nuclear power (so-called SUS316NG material) is more preferable.

  In addition, an insulation protective layer for insulating and protecting the exterior 19 may be provided around the exterior 19 by appropriately winding a polyimide tape or a PEEK tape as necessary. The exterior 19, that is, a braided wire made of metal (stainless steel), may have a surface that rises due to deterioration over time. However, by providing this insulating protective layer, safety during handling of the radiation-resistant cable 10 can be further increased, and unnecessary earth current can be prevented from leaking from the exterior 19 to the surroundings.

  The PEEK constituting the insulator coating 12 is represented by the following chemical formula (1).

The specific gravity of PEEK increases as the crystallinity increases, and the strength increases with the crystallinity. The crystallinity required for the insulator coating 12 made of PEEK is not particularly specified, but a specific gravity of 1.28 or more (upper limit is 1.401) is particularly preferable. The “specific gravity” here refers to the specific gravity d ₂₃ measured at a temperature of 23 ° C.

  Examples of the material constituting the inclusions 16 include aramid fibers in addition to polyimide materials. By providing the inclusions 16 of aramid fibers that are excellent in flexibility, the flexibility of the entire radiation-resistant cable can be further increased.

  The good conductor constituting the electromagnetic shielding layer 17 is not particularly limited, and those normally used as a shielding layer for cables can be applied, and examples thereof include Sn-plated annealed copper wire.

  The conductor 11 may be either a single wire material or a stranded wire material. The constituent material of the conductor 11 is not particularly limited, and those normally used as a conductor for a power supply line or a signal supply line can be applied. Ni-plated annealed copper wire, Ag-plated annealed copper wire, Sn-plated wire An annealed copper wire etc. are mentioned.

  Next, the operation of the present embodiment will be described.

  PEEK is a halogen-free material with excellent heat resistance and a material with excellent radiation resistance. Here, polyimide is a material having the same characteristics as PEEK. However, in the radiation resistant cable 10 according to the present embodiment, PEEK is used instead of polyimide as a constituent material of the insulator coating 12 provided around the conductor 11. The reason is described below.

  Fig. 3 shows the relationship between the absorbed dose and tensile strength of PEEK, and the absorbed dose and elongation. Fig. 4 shows the relationship between absorbed dose and tensile strength of polyimide, and absorbed dose and elongation (Reference: Results of Radiation Tests. At Cryogenic Temparacha on Some Selected Organic Materials for the LHC (European Organization for Nuclear Research (CERN)), 1996 July 4, 1996, 96-05, p.16-18).

  As shown in FIG. 4, the polyimide has a tensile strength (line 41 with a black circle in FIG. 4) of about 130 to 180 MPa and elongation (in FIG. 4) when the absorbed dose ranges from 0 to 50 MGy at room temperature. (3) The line 42) connecting the marks is about 9 to 30%. Polyimide has a tensile strength (line 43 with a circle in FIG. 4) of about 170 to 280 MPa and elongation (marked with a square in FIG. 4) when the absorbed dose is in the range of 77K and 0 to 120MGy. Line 44) is about 5 to 10%.

  Further, as shown in FIG. 3, PEEK has a tensile strength (line 31 connecting black circles in FIG. 3) of about 40 to 100 MPa and elongation (FIG. 3) when the absorbed dose is in the range of 0 to 50 MGy at room temperature. Among them, the line 32) connecting the ■ marks is about 0.8 to 160%. PEEK has a tensile strength (line 33 with a circle in FIG. 3) of about 130 to 180 MPa and elongation (marked with a □ in FIG. 3) when the absorbed dose is in the range of 77K and 0 to 120MGy. Line 34) is about 5-8%.

  As can be seen from FIGS. 3 and 4, the tensile strength and elongation of polyimide and PEEK are substantially the same in the range of 77 K and absorbed dose in the range of 0 to 120 MGy. However, in the range of room temperature and absorbed dose in the range of 0 to 20 MGy, the tensile strength of polyimide is higher than that of PEEK, and conversely, the elongation of PEEK is larger than that of polyimide. That is, at room temperature and in an environment where the absorbed dose is 0 to 20 MGy, the PEEK insulator coating has a better elongation than the polyimide insulator coating, and the PEEK elongation is about 20 to 160%. Therefore, an electric wire having a PEEK insulator coating has better handling properties when being laid and routed than a wire having a polyimide insulator coating.

  Moreover, in the curvature part of an insulated wire, when the elongation of the insulator coating is larger, the insulating layer is less likely to be cracked or cracked when bent, and the bending resistance is improved. Although there is no provision for the elongation required for insulated wires after irradiation, the UL1581 standard requires ETFE insulated wires to have an elongation of 75% or more after heating, and the elongation is 50% or more. If there is, it is said that no cracking will occur even if the wire is rounded to about twice the outer diameter. Furthermore, in the process of manufacturing an insulated wire, when a conductor is covered with a resin insulator coating using a normal extrusion process, an elongation of at least about 50% is required. Here, the bending resistance (elongation) after irradiation of PEEK varies depending on the specific gravity of PEEK, and is greatly improved by using PEEK having a specific gravity of 1.28 or more. The reason why PEEK having a specific gravity of 1.28 or more is preferable is that the properties of tensile strength, cut-through strength, and AC breakdown voltage change greatly when the specific gravity is 1.28, and each characteristic is greatly improved. Therefore, by using PEEK having a specific gravity of 1.28 or more, radiation resistance, flex resistance, and flame retardancy are further improved. Specifically, in the case of a PEEK with a specific gravity of less than 1.28, as shown in FIG. 3, the elongation is less than about 50% in the range of absorbed dose of 10 to 20MGy, but the PEEK with a specific gravity of 1.28 or more. When is used, an elongation rate of 50% or more can be secured in the range of absorbed dose of 30 MGy or less.

  As described above, in the radiation-resistant cable 10 according to the present embodiment, the insulator coating 12 is made of PEEK, preferably PEEK having a specific gravity of 1.28 or more.

  Further, according to the radiation resistant cable 10 according to the present embodiment, since the constituent material of the sheath (sheath) 19 is made of metal, the radiation resistance can be achieved even in a high radiation environment exceeding the absorbed dose of 10 MGy or more. Is good. For example, the cable sheath excellent in radiation resistance and corrosion resistance can be obtained by using stainless steel as the constituent material of the outer casing 19. Further, since the exterior 19 is formed of a flexible metal braided wire, even if the radiation resistant cable 10 has a large diameter such that the outer diameter exceeds 5 mm, its flexibility is good and it is bent. The handling is good when laying and handling. Furthermore, the radiation exposure amount of the insulator coating 12 can be reduced by the exterior 19.

  As described above, in the radiation resistant cable 10 according to the present embodiment, the insulation coating 12 is made of PEEK, and the exterior 19 is made of a metal braided wire, so that the absorbed dose is 10 MGy or more in a high radiation environment. , The radiation resistance and bending resistance of the wire core are high, high flame retardancy and halogen-free are satisfied, and the flexibility of the entire cable is good.

  The radiation resistant cable 10 according to the present embodiment is suitable as a connection cable for a synchrotron turbomolecular pump, but the application range is not particularly limited thereto. For example, the present invention can also be applied to cables exposed to high-level radiation having an absorbed dose of 10 MGy or more, other accelerators (for example, linac), nuclear power equipment, power cables such as medical equipment using radiation, and signal cables. It can also be applied to a large-diameter bending-resistant cable that requires flame resistance and halogen-free.

  Next, another embodiment of the present invention will be described with reference to the accompanying drawings.

  A cross-sectional view of a radiation resistant cable according to another preferred embodiment of the present invention is shown in FIG. In addition, the same code | symbol is attached | subjected to the member similar to FIG. 1, and description is abbreviate | omitted about these members.

  As shown in FIG. 2, the radiation resistant cable 20 according to the present embodiment is formed by bundling multiple types (four types in FIG. 2) of twisted wire units 23 a to 23 d with a polyimide tape 27. A wire portion 24 is formed, and an electromagnetic shielding layer 17, an insulating layer 18 composed of a polyimide-based material tape, and an outer sheath (sheath) 19 are sequentially provided around the stranded wire portion 24.

  The stranded wire portion 24 includes an inner layer stranded wire portion 24a composed of stranded wire units 23a, 23b, and 23c, and an outer layer stranded wire portion 24b composed of a stranded wire unit 23d.

  The inner layer stranded wire portion 24a fixes a unit group formed by twisting together a pair of stranded wire units 23a, a pair of stranded wire units 23b, and one stranded wire unit 23c with a polyimide tape 26, and this unit group and the polyimide tape The inclusions 16 of the polyimide material are provided in the gaps with respect to H.26.

  The outer layer stranded wire portion 24b is provided with an insulating layer 27 made of polyimide tape around a group of twelve stranded wire units 23d concentrically stranded around the inner layer stranded wire portion 24a. The inclusion 16 of polyimide material is provided in the gap between the group of the above and the insulating layer 27.

  Each twisted wire unit 23a has an insulating layer 25 composed of polyimide tape in order around a unit main body portion in which four twisted wires 29 obtained by twisting two wire cores 13 shown in FIG. An electromagnetic shielding layer 17 is provided. In the gap between the unit main body and the insulating layer 25, an inclusion 16 made of a polyimide material is provided.

  Each stranded wire unit 23b is provided with an insulating layer 25 and an electromagnetic shielding layer 17 in order around a unit main body portion in which two twisted wires 29 are twisted together. In the gap between the unit main body and the insulating layer 25, an inclusion 16 made of a polyimide material is provided.

  The stranded wire unit (wire core) 23 c has the same configuration as the wire core 13 shown in FIG. 1, and has a PEEK insulator coating 22 around the conductor 21. Further, each stranded wire unit 23 d is configured by a twisted wire 29.

  In the present embodiment, the number of wire cores of the stranded wire unit 23a is 8, the number of wire cores of the stranded wire unit 23b is 4, the number of wire cores of the wire core 23c is 1, and the number of wire cores of the stranded wire unit 23d is 1. The case of two wires has been described, but the number of wire cores is not particularly limited to this, and is appropriately selected as necessary.

  In the present embodiment, the inner layer stranded wire portion 24a is a pair of stranded wire units 23a, a pair of stranded wire units 23b, and a single wire core 23c, and the outer layer stranded wire portion 24b is 12 wires. Although the case where it is constituted by the stranded wire unit 23d has been described, the number of types of units and the number of each unit are not particularly limited thereto, and are appropriately selected as necessary.

  The radiation resistant cable 20 according to the present embodiment has a larger diameter than the radiation resistant cable 10 according to the previous embodiment shown in FIG. 1, but the exterior 19 is formed of a metal braided wire. Therefore, it has sufficient flexibility, and is excellent in handling property at the time of laying and handling with bending.

  Also in the radiation resistant cable 20 according to the present embodiment, the same effects as the radiation resistant cable 10 according to the previous embodiment can be obtained.

  As described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various other things are assumed.

  Next, although this invention is demonstrated based on an Example, this invention is not limited to this Example.

  PEEK insulation with an outer diameter of 1.68 mm is formed by forming a PEEK (specific gravity: 1.28 or more) insulator coating around a conductor formed by twisting 19 Ni-plated annealed copper wires with an outer diameter of φ0.2 mm. An electric wire (wire core) was produced (Sample 11).

  The sample 11 was irradiated with radiation (γ rays) to evaluate the radiation resistance. The target absorbed dose was 10 MGy (actually 11.8 MGy), 30 MGy, and 50 MGy (actually 45.4 MGy). The sample 11 after irradiating each absorbed dose of γ-rays was observed for appearance and withstand voltage test. The withstand voltage test was performed according to IEEJ Technical Report (Part II) No. 139. Specifically, after the sample 11 was wound around a stainless steel mandrel having a diameter of 34 mm (20 times the outer diameter of the covered wire), an AC voltage of 1.1 kV was passed for 5 minutes, and a sample in which dielectric breakdown did not occur was evaluated as good. The test voltage was determined according to the thickness of the insulator coating, and was 3.2 kV per 1 mm thickness, that is, 3.2 kV × [0.34 mm / 1.00 mm] = 1.1 kV.

  In the sample 11 after irradiating the absorbed dose of 10MGy (hereinafter referred to as 10MGy irradiation), no damage such as cracks was observed on the surface. In sample 11 after irradiation with gamma rays with an absorbed dose of 30 MGy (or 50 MGy) (hereinafter referred to as after 30 MGy (or 50 MGy) irradiation), some cracks were observed on the surface. This is considered to indicate that the elongation of PEEK deteriorates due to curing accompanying irradiation. On the other hand, the dielectric breakdown did not occur in the sample 11 after irradiating each absorbed dose of γ rays.

  That is, it can be confirmed that the sample 11 has a radiation resistance of 10 to 50 MGy in terms of withstand voltage. In addition, it was confirmed that the sample 11 had good elongation, that is, good bending resistance when the absorbed dose ranged from 10 to 30 MGy.

  In this example, the radiation resistance was evaluated for the wire core comprising the insulator coating using a PEEK material having a specific gravity of 1.28 or more. If the absorbed dose is about 10 to 20 MGy, the specific gravity is less than 1.28. Even a wire core in which an insulator coating is formed using the PEEK material has sufficient radiation resistance and bending resistance.

1 is a cross-sectional view of a radiation resistant cable according to a preferred embodiment of the present invention. It is a cross-sectional view of a radiation resistant cable according to another preferred embodiment of the present invention. It is a figure which shows the relationship between absorbed dose and tensile strength of PEEK, absorbed dose, and elongation. It is a figure which shows the relationship between the absorbed dose and tensile strength of a polyimide, and an absorbed dose and elongation. It is a layout view of a turbo molecular pump in a synchrotron.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Radiation resistant cable 11 Conductor 12 Insulator coating 13 Wire core 14 Stranded wire part 19 Exterior

Claims (9)

  A cable that is exposed to radiation of 10 MGy or more, and a wire core having a polyether ether ketone insulator coating is formed around a conductor, and an outer sheath composed of a metal braided wire is formed around the wire core. A radiation resistant cable characterized by being provided.   A cable that is exposed to radiation of 10 MGy or more, and a twisted wire portion is formed by twisting a plurality of wire cores having a polyether ether ketone insulator coating around a conductor, and a metal is formed around the twisted wire portion. A radiation-resistant cable, characterized in that an exterior composed of a braided wire made of metal is provided.   A cable that is exposed to radiation of 10 MGy or more, and a twisted wire is formed by twisting a wire core having a polyether ether ketone insulator coating around a conductor, and at least one twisted wire is used. Two or more types of stranded wire units are formed, each stranded wire unit is bundled to form a stranded wire portion, and an exterior made of a metal braided wire is provided around the stranded wire portion. Radiation cable.   The radiation-resistant cable according to any one of claims 1 to 3, wherein the outer sheath is made of a braided wire made of stainless steel.   The radiation-resistant cable according to any one of claims 1 to 4, wherein the polyether ether ketone constituting the insulator coating has a specific gravity of 1.28 or more.   The radiation-resistant cable according to any one of claims 1 to 5, wherein an inclusion of a polyimide-based material is provided inside the outer sheath and / or in the stranded portion.   The radiation-resistant cable according to claim 6, wherein the inclusion is an aramid fiber.   The radiation-resistant cable according to any one of claims 1 to 7, wherein an insulation protective layer made of a polyimide-based material is provided around the exterior. The radiation resistant cable according to any one of claims 1 to 7, wherein an insulating protective layer made of a polyether ether ketone material is provided around the outer sheath.

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