CN201302852Y - Coaxial cable used for galvanometer of nuclear power plant reactor - Google Patents

Abstract

The utility model relates to the coaxial cable technology and aims to provide a coaxial cable for a reactor galvanometer in a nuclear power plant. A columnar body; an inner semiconductive extruded cladding made of semiconductive fluoroplastic is also provided between the inner conductor and the insulating layer. The utility model uses polyimide to isolate the inner sheath to isolate the outer conductor from the shielding layer, so that the external electromagnetic interference current is separated from the current of the outer conductor of the coaxial cable, which really plays the role of shielding and isolation; at the same time, it adopts a fully enclosed steel alloy shielding , Most of the external magnetic flux is confined on the steel sheath of the cable, and only a small part enters the shielded space, which improves the anti-electromagnetic interference level of the cable.

Description

Coaxial cable for reactor galvanometer in nuclear power plant

technical field

The utility model relates to a coaxial cable technology, in particular to a coaxial cable for a nuclear power plant reactor galvanometer.

Background technique

Atomic power stations generally use light water moderated reactors to generate electricity, and in this form of electricity generation, the utilization rate of natural uranium is only 2%. Considering the shortage of energy resources in the world, in order to effectively utilize nuclear resources such as uranium, countries around the world are stepping up research, development and application of fast breeder reactors and new conversion reactors to generate electricity. The surrounding environment of this type of reactor is different from that of the light water moderated reactor. Generally, the cables used in this environment should meet the following basic requirements: 1. Radiation dose resistance: 3×10 ¹⁰ Rad. 2. Temperature resistance: generally 50-200 °C, about 400 °C under abnormal conditions.

In the vicinity of nuclear reactors, a coaxial cable is often used, placed in the reactor core, connected to the neutron meter, used to detect the neutron flux. When in use, connect one end of the cable to the ionization chamber or probe, and the other end to the neutron measuring instrument. Among them, the inner conductor of the coaxial cable is connected with the inner ceramic plate of the probe, and the outer conductor is connected with the outer shell of the probe. Because the surface of the tile is coated with a layer of radioactive material, the radioactive material is bombarded by neutrons to produce fission and ionization, and the measured signal of micro-current or micro-voltage is generated, and then introduced into the neutron detector through the inner conductor. Strictly speaking, it is introduced into the preamplifier part of the instrument first, and the neutron flux is detected after amplification processing. Such cables should generally be able to meet the above basic temperature and radiation dose tolerance requirements. However, due to the harsh environment and the accuracy requirements of the measurement system, the coaxial cables designed and used in the past have the following shortcomings and deficiencies:

(1) Most of the cables used in this environment in the past used inorganic insulated cables, which had poor bending performance, extremely inconvenient laying, and high prices.

(2) Inorganic insulation is used, even if vacuum processing is used, air gaps must remain in the insulation. Under neutron bombardment and ray irradiation, the air will be activated and ionized to generate current, which will interfere with the measurement of the detection current and affect the accuracy and precision of the measurement.

(3) Susceptible to electromagnetic interference, affecting the stability of the transmitted signal.

In the galvanometer system, the excitation power supply is generally assembled with the flow sensor. Therefore, the coaxial cable responsible for transmission will inevitably be disturbed by the electromagnetic field of the excitation cable, thereby affecting the stability of the transmitted signal. In view of this situation, it is clearly stipulated in engineering installation and application that the coaxial cable and the excitation cable must be strictly separated, and cannot be laid in the same pipe, cannot be laid in parallel, cannot be twisted together, and should be laid separately through the pipe , in order to carry out effective electromagnetic isolation, the cost of installation and laying is relatively high, and it is inconvenient to use.

(4) There is a lot of noise inside the cable, which affects the resolution and accuracy of the signal.

In practical applications, when the coaxial cable is subjected to shock, vibration, bending, and external temperature changes, the internal friction of the cable will generate noise, which will be sandwiched in the signal and output together, which will inevitably affect the resolution and accuracy of the transmitted signal. This effect is more prominent when the galvanometer is used for micro-accurate metering of harsh reactors with solid-liquid-gas three-phase flow media, which will easily cause large measurement errors and inaccurate measurements.

In view of the defects and deficiencies in the above-mentioned cables, a new type of coaxial cable for reactor galvanometers in nuclear power plants is needed.

Utility model content

The utility model aims at the product performance defect of the traditional coaxial cable, and provides a coaxial cable for a nuclear power plant reactor galvanometer in order to overcome the deficiencies in the prior art.

Its main design ideas are as follows:

1. The structure design and material selection of cable shielding layer with high anti-interference ability;

2. Low noise structure design and material selection inside the cable;

3. The overall flexible design of the cable.

Aiming at the characteristics of the coaxial cable used in the nuclear power plant reactor galvanometer and its operating environment requirements, taking into account the internal noise level of the cable, the level of anti-electromagnetic interference, the difficulty of process realization and the manufacturing cost and other factors, the utility model is realized through the following technical solutions of.

A coaxial cable for a reactor galvanometer in a nuclear power plant. Its structure includes an inner conductor, an insulating layer, an outer conductor, and a sheath from the inside to the outside, and is coated into a columnar body from the outside to the inside; Features an inner semiconductive extruded cladding made of semiconductive fluoroplastic.

As an improvement, an outer semiconductive extruded cladding layer is also provided between the insulating layer and the outer conductor.

As a further improvement, the insulating layer is an insulating layer formed by extruding thermoplastic polyimide.

As a further improvement, the outer surface of the outer conductor is provided with an isolation inner sheath formed by extrusion.

As a further improvement, the outer surface of the isolation inner sheath is longitudinally annularly covered with a shielding layer.

As a further improvement, the outer semiconductive extruded cladding layer is preferably made of semiconductive fluoroplastic, and is longitudinally annularly coated on the outer surface of the insulating layer.

As a further improvement, the isolation inner sheath is preferably an isolation inner sheath made of insulating grade thermoplastic polyimide.

As a further improvement, the shielding layer is preferably longitudinally wrapped and welded by an alloy steel strip into a cylindrical tubular shape, and covered on the outer surface of the isolation inner sheath.

As a further improvement, the sheath is made of sheath-grade thermoplastic polyimide.

As a further improvement, the inner conductor is an inner conductor made of silver-plated copper wire or nickel-plated copper wire.

Compared with the prior art, the coaxial cable for the nuclear power plant reactor galvanometer of the present utility model mainly has the following advantages:

(1) High anti-electromagnetic interference ability

Polyimide is used to isolate the inner sheath to isolate the outer conductor from the shielding layer, so that the external electromagnetic interference current is separated from the current of the outer conductor of the coaxial cable, and it really plays the role of shielding isolation.

At the same time, fully enclosed steel alloy shielding is adopted, most of the external magnetic flux is limited on the steel sheath of the cable, and only a small part enters the shielded space, which improves the anti-electromagnetic interference level of the cable. At the same time, the cable is strengthened to reduce the electromotive force caused by the vibration of the cable and improve the accuracy and reliability of the cable transmission signal.

(2) Excellent low noise performance

Since the generation of static charge is proportional to the friction section between the insulating layer and the conductor, the static charge generated between the outer conductor and the insulating layer is much greater than that between the insulating layer and the inner conductor. In this way, in the past, the suppression of electrostatic charge generally adopts the method of adopting organic coating or wrapping on the surface of the insulating layer. In this cable design, the following three aspects are considered comprehensively.

The insulation layer is made of thermoplastic polyimide solid insulation, which avoids the generation of air-activated ionization current in foam insulation or inorganic insulation and affects the measurement results.

A thin layer of semi-conductive fluoroplastic is extruded outside the insulating layer, which is beneficial to reduce the frictional electrification noise between the outer conductor and the insulating layer, and can reduce the original noise of the cable by two to three orders of magnitude.

A thin layer of semi-conductive fluoroplastic is extruded between the inner conductor and the insulation layer, which is beneficial to reduce the frictional electric noise between the inner conductor and the insulation. At the same time, compared with the previous method of using organic coating or wrapping, it is more conducive to reducing and eliminating the gas gap between the inner conductor and the insulation.

(3) Good bending performance and low engineering comprehensive cost

Compared with the previous design of cables with inorganic insulation or rigid outer conductor, this cable design uses organic insulation, flexible outer conductor and semi-flexible steel alloy shielding layer, which greatly improves the overall bending performance of the cable and facilitates cable laying.

Due to the excellent shielding design, in the actual engineering installation, the cables do not need to be laid through metal pipes, which can reduce the overall cost of the project.

In summary, the coaxial cable used for the nuclear power plant reactor galvanometer of the utility model solves the problem of poor anti-electromagnetic interference ability of the traditional coaxial cable from the technical design, reduces the internal noise of the cable, and makes up for the defects of the traditional similar cable and deficiencies; meet the resolution, accuracy, precision and other requirements of the precise measurement of the trace neutron flux in the nuclear reactor.

Description of drawings

Fig. 1 is the structural representation of the specific embodiment of the utility model;

Fig. 2 is the production process flowchart of the specific embodiment of the utility model.

In the figure: 1-inner conductor; 2-inner semiconductor extruded cladding; 3-insulation layer; 4-outer semiconductor extruded cladding; 5-outer conductor; 6-isolated inner sheath; 7-steel alloy shielding layer; 8- jacket.

Detailed ways

In conjunction with the accompanying drawings, the utility model will be further described.

A coaxial cable for a reactor galvanometer in a nuclear power plant, the structure of which includes an inner conductor 1, an insulating layer 3, an outer conductor 5, and a sheath 8 from inside to outside, and is coated into columns from outside to inside; An inner semiconductive extruded cladding layer 2 made of semiconductive fluoroplastic is arranged between the layers 3 .

An outer semi-conductive extruded cladding 4 is provided between the insulating layer 3 and the outer conductor 5; the outer surface of the outer conductor 5 is provided with an isolated inner sheath 6 formed by extruding; the outer surface of the isolated inner sheath 6 is longitudinally and annularly covered with a shielding layer ; The outer semiconductive extruded cladding layer 4 is preferably made of semiconductive fluoroplastic, and its longitudinal annular coating is on the outer surface of the insulating layer 3 .

The following is a brief description of the composition, structure and process requirements of the coaxial cable used for the galvanometer of the nuclear power plant reactor according to Figure 1 and Figure 2:

(1) Inner conductor 1

In order to prevent oxidation during high temperature use, it is generally advisable to use silver-plated copper wire or nickel-plated copper wire as the inner conductor 1, which improves the heat resistance and corrosion resistance of the conductor. In this embodiment, a silver-plated copper wire is used as the inner conductor 1 .

(2) Inner semi-conductive extruded cladding 2

A thin layer of semi-conductive fluoroplastic is extruded outside the inner conductor 1, which is beneficial to reduce frictional electrical noise between the inner conductor 1 and the insulating layer 3. At the same time, compared with the conventional organic coating or wrapping method, it is more beneficial to reduce and eliminate the gas gap between the inner conductor 1 and the insulating layer 3 .

(3) Insulation layer 3

The insulating layer 3 is formed by extrusion of relatively pure thermoplastic polyimide with better heat resistance and radiation resistance, which reduces the gap with the inner conductor 1; the insulating layer 3 adopts solid insulation to avoid foaming insulation or The generation of air-activated ionization current in inorganic insulation affects the measurement results.

(4) Outer semi-conductive extruded cladding 4

A thin layer of semi-conductive fluoroplastic is extruded outside the insulating layer 3, which is beneficial to reduce the frictional electrification noise between the outer conductor 5 and the insulating layer 3, and can reduce the original noise of the cable by two to three orders of magnitude.

(5) Outer conductor 5

The outer conductor 5 is braided with silver-plated copper wire. The braided layer is tightly covered on the outer surface of the outer semiconductive extruded cladding layer 4 .

(6) Isolation inner sheath 6

The outer conductor 5 is extruded and covered with an isolation inner sheath 6, and the isolation inner sheath 6 is made of insulating grade thermoplastic polyimide.

(7) Steel alloy shielding layer 7

The high magnetic permeability alloy corrugated steel strip is used for longitudinal cladding welding, and the steel alloy sheath should form a continuous corrugated cylindrical tube. The high magnetic permeability alloy steel strip is a strong magnetic material, and it is shielded by a fully enclosed steel alloy. Most of the external magnetic flux is limited on the steel sheath of the cable, and only a small part enters the shielded space, which improves the anti-electromagnetic interference level of the cable. At the same time, the cable is strengthened to reduce the electromotive force caused by the vibration of the cable. At the same time, the softness of the cable as a whole is improved by using the corrugated steel strip.

(8) Sheath 5

Outside the steel alloy shielding layer 7, protective layer-level thermoplastic polyimide is used for protection.

Finally, it should also be noted that the above examples are only specific implementation examples of the present utility model. Obviously, the present utility model is not limited to the above implementation examples, and many variations are possible. All deformations that a person skilled in the art can derive or associate directly from the content disclosed in the utility model shall be considered as the protection scope of the utility model.

Claims (10)

1. A coaxial cable for a nuclear power plant reactor galvanometer, whose structure includes an inner conductor, an insulating layer, an outer conductor, and a sheath from the inside to the outside, and is coated into a columnar body from the outside to the inside; it is characterized in that the inner conductor An inner semiconductive extruded cladding layer made of semiconductive fluoroplastic is arranged between the insulation layer and the insulating layer. 2. The coaxial cable for nuclear power plant reactor galvanometer according to claim 1, characterized in that an outer semi-conductive extruded cladding is also provided between the insulating layer and the outer conductor. 3. The coaxial cable for nuclear power plant reactor galvanometer according to claim 1, wherein the insulating layer is an insulating layer formed by extruding thermoplastic polyimide. 4. The coaxial cable for nuclear power plant reactor galvanometer according to claim 1, characterized in that, the outer surface of the outer conductor is provided with an isolation inner sheath formed by extruding. 5. The coaxial cable for nuclear power plant reactor galvanometer according to claim 1, characterized in that, the outer surface of the isolation inner sheath is longitudinally and circularly covered with a shielding layer. 6. The coaxial cable for nuclear power plant reactor galvanometer according to claim 2, characterized in that, the outer semiconductive extruded cladding is preferably made of semiconductive fluoroplastics, and its longitudinal The ring is wrapped on the outer surface of the insulating layer. 7. The coaxial cable for nuclear power plant reactor galvanometer according to claim 4, characterized in that the isolation inner sheath is preferably an isolation inner sheath made of insulating grade thermoplastic polyimide. 8. The coaxial cable for nuclear power plant reactor galvanometer according to claim 5, characterized in that, the shielding layer is preferably welded longitudinally with an alloy steel strip into a cylindrical tubular shape, and is covered on the outer surface of the isolation inner sheath. 9. The coaxial cable for nuclear power plant reactor galvanometer according to claim 1, wherein the sheath is made of sheath grade thermoplastic polyimide. 10. The coaxial cable for nuclear power plant reactor galvanometer according to claim 1, wherein the inner conductor is made of silver-plated copper wire or nickel-plated copper wire.

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