JPS58100313A - Laminated sheath electric cable for atomic power generation plant - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laminated sheathed electric cable for a nuclear power plant, and more particularly to a laminated sheathed electric cable using a radiation-resistant crosslinked polyolefin as a resin laminated to a metal tape.

Cables used in light water reactor nuclear power plants are constantly exposed to heat and radiation, and in addition, in the event of a loss of coolant accident,
It must maintain its function as a cable even when exposed to high-temperature steam in a boiling water reactor (BWR) or to high-temperature steam and a chemical solution consisting of boric acid or caustic soda in a pressurized water reactor (PWR). .

Therefore, the insulation and sheath materials used in these cables must have heat resistance, radiation resistance, water vapor resistance, and the like. Furthermore, a high degree of flammability is required in case of a fire accident.

By the way, conventionally, in order to make the insulating material and the sheath material compatible with these objectives, a method has been taken in which the additives added to the polymeric material as a paste and the amount thereof are selected.

However, in a cable configuration in which the insulating material and sheath material are composed only of polymeric materials, the mechanical properties of these polymeric materials deteriorate significantly when exposed to thermal deterioration, gamma ray irradiation, and high-temperature steam, and A problem arises in that electrical characteristics such as breakdown voltage are significantly reduced.

The present invention has been made in view of the above, and its purpose is to significantly suppress the deterioration of electrical characteristics such as AC breakdown voltage even when exposed to heat, radiation, and high-temperature steam containing chemical liquids. The object of the present invention is to provide a laminated sheathed electric cable for nuclear power plants that can be used in nuclear power plants.

A feature of the present invention is that radiation-resistant water-crosslinked silane grafted polyolefin obtained by adding at least one of a silane compound, an aromatic compound, or a complex compound and a radical generator to a polyolefin and causing a heating reaction is laminated onto a metal tape. The electrical cable has a shielding layer made of laminated tape.

In the present invention, the reason why radiation-resistant water-crosslinked silane craft polyolefin was used as the resin to be laminated to the metal tape is that resins generally used for laminated sheathed electric cables have poor radiation resistance, and the adhesive strength after irradiation is poor. This is to prevent this from occurring, since if the temperature drops to an extremely high temperature and the insulation material is exposed to high-temperature water vapor, the water vapor will reach the insulating material through the sheath material, significantly reducing the electrical characteristics.

Here, polyolefin refers to an olefin poly or a copolymer containing an olefin, such as polyethylene, ethylene, vinyl acetate copolymer, copolymer of ethylene/acrylic acid or its ester, ethylene/propylene (
or diene monomer) copolymers, ethylene-α-olefin copolymers, ethylene-butylene copolymers, herodinated polyolefins, and those obtained by graft polymerization of vinyl chloride monomers.

In addition, the silane compound has hydrolyzable organic groups such as
Aliphatically unsaturated hydrocarbon groups containing alkoxy groups such as methoxy, ethoxy, and butoxy groups, and which are reactive with free radical sites generated in the polymer; Compounds are preferred, representative examples of which are silane, vinyltrimethoxysilane,
Examples include vinyltriethoxysilane and vinyltriacetoxysilane.

Aromatic compounds include antioxidants such as phenol, amine, sulfur, and phosphorus, and aromatic oils used as operating oils for rubber, such as 2.5-Di
-Tertiary butylhydroquinone, N,%-1 phenyl-P-
Examples include phenylenediamine and propylfluorancel.

Examples of the heterocyclic compound include triazine derivatives, 2
．． Mention may be made of 2,4-trimethyl-1,2-dihydroquinoline.

In addition, as a radical generator, dicumyl peroxide, benzoyl peroxide, 2,5-dimethyl-2,5-:
) (5-butyl, peroxy)hequin-3, azo compounds such as azobisisobutyronitrile and dimethylazoisobutyrate.

In the progress of the chemical reaction in the present invention, as a siloxane condensation catalyst, dibutyl tin dilaurate, dibutyl tin dioctaate, lead naphthenate, etc., ethylamine, dibutylamine, hexylamine, etc. are generally used as a siloxane condensation catalyst. Organic bases are used. However, care must be taken because if the crosslinking density becomes too high due to the addition of a condensation catalyst, the adhesive strength with the metal tape will decrease.

Furthermore, the cross-linked polyolefin may include antioxidants, metal damage inhibitors, and ray absorbers that do not inhibit the effects of the present invention.
Various additives such as coloring agents may be used.

Metals that can be used in the present invention include metals from periodic table tb, nb■,
Metals of the ■, ■, and ■ groups. Preferred metals are iron,
These include aluminum, zinc, tin, copper, lead, etc. and alloys of these metals such as brass and steel. It is preferred that the metal surface be carefully cleaned to remove grease, dirt, and other organic residues.

The method for producing a laminate tape according to the present invention includes a lamination method,
This can be done by any method such as painting or a combination of both. For example, in the lamination method, polyolefin is continuously laminated onto a metal tape using an extruder or a coating machine.In addition, pellets, powder, etc. can also be used instead of a film-like material.

Next, examples of the present invention and comparative examples for reference will be described.

Example 1 Density a934f/cII, melting index K Of710mi
n medium density polyethylene, 1.5 parts by weight of vinylmethoxysilane, 15 parts by weight of dicumyl peroxide, 3 parts by weight of propylfluoranthene, poly-2,2,4-trimethyl- Add α1 part by weight of 12-dihydroquinoline and mix with a Henschel mixer to 70%
Stir impregnated for 5 minutes at 40°C and 23°C by extruder.
Soft aluminum (thickness:
2) The laminated tape was extruded to a thickness of 0.05 cm and used to produce an electric cable (conductor! SX! L5-) consisting of an ethylene autofluoropylene rubber insulation and a chlorosulfonated polyethylene outer protective layer.

Dense flJ 2 Density α88t/cd, Weld index ゛21f/10m1n
For 100 parts by weight of ethylene propylene copolymer (ethylene content 8゜l1b), 2 parts by weight of vinylmethquinonelan, 0.2 parts by weight of dicumyl peroxide,
Propyl 7keolanthene t-2 parts by weight, poly-2,2,
0.1 part by weight of 4-trimethyl 1,2-dihydroquinoline was added, stirred and impregnated in a Henschel mixer at 0°C for 5 minutes. 0.21111) upper K
Extruded to a thickness of O5wi, this laminated tape was used to make an electric cable (conductor 3x5.5-) consisting of ethylene/propylene rubber insulation and chloroprene outer protective layer.
was produced.

Back fa example 3 Density α88~α89 f/d, melting index 3~5F/IQ
min (190°C) low crystalline polyolefin resin 10
0 parts by weight, 2 parts by weight of vinyl trimethoxine, 2 parts by weight of dicumyl peroxide, 2 parts by weight of tripropylfluoranthene, poly-2,2,4-trimethyl-1,2-dihydro After adding 0.1 weight of quinoline and stirring and impregnating it at 70°C for 5 minutes using a Henschel mixer, O, The laminated tape was extruded to the thickness of OS cod, and an electric cable (conductor 3 x 5.5-) consisting of ethylene propylene rubber insulation and chlorinated polyethylene outer protective layer was manufactured using this laminated tape.

Comparative Example 40 ■ A polyolefin copolymer containing a reactive carboxyl group was extruded onto softened aluminum (thickness 0.2 wm) to a thickness of 0.05 ■ using an extruder at 250°C using a T-die, and this laminate was An electric cable (conductor 3xs, sj) consisting of ethylene fluoropylene rubber insulation and a chlorosulfonated polyethylene outer protective layer was manufactured using tape.

Note that since aluminum tape is generally used as the metal in laminated sheathed electric cables, aluminum tape was used as the metal tape in both Examples and Comparative Examples. FIG. 1 is a sectional view showing an embodiment of the laminated sheathed electric cable of the present invention. In FIG. 1, 100 is a cable core, 1 is a conductor, and 2 is an insulator. 1
o is a laminate tape that covers the three cable cores vertically, 3 is a metal tape, and 4 is a laminate resin layer. 5 indicates an outer protective layer of synthetic resin.

Next, the adhesive strength of the laminate tapes obtained in each of the above-mentioned Examples and Comparative Examples and the AC breakdown voltage of an electric cable using the same were investigated. Figure 2 is an explanatory diagram of the method for testing the adhesive strength of laminated tapes, where 6 is an aluminum tape and 7Fi laminated resin layer is pulled in the direction shown by the arrow at a pulling speed of 100 m/min in the state shown in the figure. The tensile force was measured. The conditions at that time were initial thermal deterioration at 121°C for 7 days, followed by further gamma ray irradiation (200°C).
Mrad) and then four after coolant exposure. The coolant exposure was made to have the relationship between temperature and time shown in Figure 3. Note that chemical spraying was performed at the same time for the first 24 hours. Further, the AC breakdown voltage of the cable was measured at a boost rate of 500 V/see.

The cable conditions when measuring AC breakdown voltage were the same as above. Table 11g1 shows the results.

Table 1 As can be seen from the results in Table 1, in the comparative example, thermal deterioration→
After irradiation with gamma rays, the adhesive strength of the laminated tape decreases significantly, and it loses its functionality as a laminated tape when subsequently exposed to coolant. Therefore, the AC breakdown voltage of the cable is x
It has significantly decreased below OTV. On the other hand, Examples 1 to 3 all exhibit radiation resistance and exhibit extremely good electrical characteristics even after exposure to coolant.

In addition, in order to increase the flexibility of the electric cable, the laminated tape may be wound horizontally or may be of a corrugated type, but the effect will not change.

As explained above, according to the present invention, there is an effect that deterioration of electrical characteristics such as AC breakdown voltage can be significantly suppressed even when exposed to heat, radiation, and high-temperature steam containing chemical liquid.

[Brief explanation of drawings]

Figure 1- is a cross-sectional view showing one embodiment of the laminated sheathed electric cable for nuclear power plants of the present invention, Figure 2 is an explanatory diagram of the method for testing the adhesive strength of laminated tape, and Figure 3 is the temperature in the intermediate coolant exposure test. It is a figure showing a profile. 100... Cable core, 1... Conductor, 2... Insulator, 10... Laminated tape, 3... Metal tape, 4 ... Laminate resin layer, 5 ... External protective layer.

Claims (1)

[Claims] 1. In a laminated sheathed electric cable using a laminate tape obtained by laminating a resin on a metal tape as a shielding layer, the resin laminated to the metal tape includes polyolefin and one or more of a silane compound, an aromatic compound, or a heterocyclic compound. An electric cable for a nuclear power plant, characterized in that it uses a radiation-resistant water-crosslinked silanglat polyolefin obtained by heating and reacting with a radical generator.