JPS6011536Y2 - Coaxial cable for reactor nuclear measurement - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a coaxial cable, and particularly to a coaxial cable for atomic species/nuclei measurement that has excellent heat resistance, flame retardancy, and radiation resistance.

Coaxial cables for atomic species/nuclei measurements are not only radiation resistant, but also durable for 0 hours at 160 to 170℃ and 3 hours at 420℃.
Severe heat resistance and flame retardance are required.

For this reason, coaxial cables for atomic species and nuclear measurements conventionally used for this purpose use crosslinked polyethylene as an insulator between the inner conductor and the outer conductor.

However, even in a coaxial cable for nuclear measurement having such a configuration, when the cross-linked polyethylene is heated to 150°C or higher, the volume expansion of the cross-linked polyethylene becomes large and the coaxial cable expands in the length direction and radial direction. try to escape.

Of these, the escape in the radial direction is suppressed by the outer conductor, and the degree of close contact with the outer conductor increases due to the expansion in the radial direction, so that escape in the length direction is also not possible.

Therefore, there was a risk that the inner conductor would eventually begin to swim, and that an accident would eventually occur in which contact would occur between the inner conductor and the outer conductor.

The purpose of this invention is to provide a coaxial cable for nuclear measurement of atomic species that has excellent heat resistance, flame retardancy, and radiation resistance without causing short circuit accidents. In a coaxial cable where the polyethylene insulator and the outer conductor are more effective, a copolymer of ethylene and tetrafluoroethylene with a thickness of 0.3wn or more and 0.6mm or less is placed between the inner conductor and the crosslinked polyethylene insulator. layer (hereafter T
It is characterized by the provision of an ETFE layer (ETFE layer).

Examples will be described below.

Figure 1 shows an embodiment of the present invention, in which the internal conductor is
TFE layer 2. After covering the crosslinked polyethylene layer 3, an outer conductor 4 is provided, on which ETFE is applied as a jacket.
Layer 5 is coated.

When manufacturing a coaxial cable with such a structure, extrusion or tape wrapping and heat sealing is used to form the ETFE layer 2 on the inner conductor 1, and the crosslinked polyethylene layer 3 is formed by extrusion. A chemical crosslinking method or a crosslinking method using electron beam irradiation is used to crosslink polyethylene, and the ETFE layer 5 of the jacket is
It is formed by the same method as TFE layer 2.

The thickness of the ETFE layer is preferably 0.371771 or more,
This thickness is 0.2571r! This is based on experimental results that 100% short-circuit prevention is not possible when the thickness is 0.3 mm or more, whereas 100% short-circuit prevention is possible when the thickness is 0.3 mm or more.

In the coaxial cable configured in this way, short circuits can be prevented even at high temperatures.

This consists of the crosslinked polyethylene shown in Figure 2 and ETFE.
This is clear from the temperature characteristic diagram of tensile strength.

The horizontal axis in Figure 2 is temperature (℃), and the vertical axis is tensile strength (℃).
/mJ), A is crosslinked polyethylene, B is E
It shows the characteristics of TFE.

As is clear from this figure, in the case of crosslinked polyethylene A, the tensile strength becomes almost 0 when the temperature rises to about 150°C, but in the case of ETFE layer B, the tensile strength is 1.0 kg/rrIA. ing.

That is, this heat resistance can prevent short circuits between the inner conductor and the outer conductor.

In addition, all insulating layers between the inner conductor and outer conductor are made of E.
If TFE is used, the entire cable will be hard, but in this example, the insulator layer is made of cross-linked polyethylene and ETFE.
Since it is a layer made of solid wood, it has an appropriate hardness and good flexibility.

Furthermore, all insulating layers between the inner conductor and outer conductor are
When TFE is used, the price of ETFE is more than 0 times that of polyethylene, so it is expensive, but it is economical because it uses a layer made of crosslinked polyethylene and ETFE.

The preferred thickness is 0.3 to 0.6 mm, which can prevent short circuits 100% and does not impose a large economic burden.

Since ETFE has flame retardancy and radiation resistance, the coaxial cable can be made flame retardant and radiation resistant.

ETFE layer and ETFE used as jacket
The properties of the layer can be further improved if the layer is crosslinked by electron beam irradiation.

In this case, the absorbed dose is preferably 30 Mrad or less.

As described above, the present invention provides a coaxial cable for measuring four atomic nuclei that does not cause short-circuit accidents and has excellent heat resistance, flame retardance, and radiation resistance properties, and is an industrially effective dog.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the coaxial cable for nuclear measurement of nuclear reactors according to the present invention, and FIG. 2 is a characteristic diagram showing the temperature characteristics of the tensile strength of ETFE in comparison with that of crosslinked polyethylene. 1...Internal conductor, 2...ETFE layer,
3...Crosslinked polyethylene layer, 4...Outer conductor, 5...ETFE layer.

Claims (1)

[Scope of utility model registration request] In a coaxial cable consisting of an inner conductor, a cross-linked polyethylene insulator provided on the outer periphery of the inner conductor, and an outer conductor, there is a thickness of 0.377177 between the inner conductor and the insulator.
1. A coaxial cable for measuring atomic species and nuclei, comprising a copolymer layer of ethylene and tetrafluoroethylene of 1 or more and 0.6wn or less.