JPH07107808B2 - Dosimeter composite cable - Google Patents

Description

The present invention relates to an electric wire / cable used in a radiation environment.

[Prior Art] Under a radiation environment, for example, electric wires and cables laid in a nuclear power plant are exposed to radiation under various conditions. Since the electric wires and cables are generally laid in a complicated and long route, it is very difficult to replace them once over the entire length. As a matter of course, if a part of the electric wire / cable is significantly deteriorated by radiation, it may lose its function as an electric wire / cable, leading to a serious disaster.

Therefore, it has been strongly demanded in related industries to know the distribution of radiation exposure amount over the entire length of electric wires / cables.

But this was previously thought to be impossible. The reason is, firstly, there is no suitable radiation dosimeter that can cover a long section like electric wires and cables, and secondly, the effect of radiation is remarkably different due to the difference in shields and positions. The main reason is that the radiation dose to the actual wire / cable does not always match the radiation dose measured by the dosimeter because it is different.

For the former, for example, a cobalt glass dosimeter, a polymethylmethacrylate (PMMA) dosimeter, etc. can be attached to the wire / cable for measurement, and the purpose can be achieved to some extent. However, these dosimeters have a length of at most 5-10 cm, and the wire and
It is difficult to apply along the cable. In addition, even if a long cobalt glass dosimeter or PMMA dosimeter is manufactured, it cannot be made to follow a continuously complicated wire or cable because of lack of flexibility.

The latter can be corrected to some extent by calculation, but it is not the actual value. In addition, these dosimeters have relatively large fading during long periods of measurement, which can last for several months or longer,
It is extremely difficult to know the accurate radiation dose distribution in principle.

[Problems to be Solved by the Invention] As described above, in the conventional technique, it is extremely difficult to measure the radiation dose distribution along the electric wire / cable, and it has not been actually measured. It can be said that this was due to lack of appropriate technical means despite strong demand from the industry.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a wire / cable including a novel dosimeter that can sufficiently meet the needs of the industry.

[Means for Solving the Problem] According to the present invention, a dosimeter unit composed of an amino acid dosimeter element having a polymer as a binder and a heat detecting member is connected to an electric wire / cable portion with a window opening bridge portion, and has a sectional shape. It is a dosimeter composite cable characterized by being formed into a gourd shape.

[Operation] Therefore, the dosimeter can accurately measure the radiation dose distribution without being affected by the heat of the power cable, and can easily separate the required dosimeter from the cable. Become.

[Example] An amino acid dosimeter using a polymer as a binder is a known one as disclosed in, for example, JP-A-61-97585 and JP-A-61-57878. In this case, alanine is used as the amino acid, but it is not limited to alanine.

Amino acid dosimeter composite cables can be easily manufactured by, for example, kneading rubber or resin with amino acids using a mixing roll or the like, and extruding as a uniform composition on the electric wire / cable insulator or sheath. Is possible. It can also be achieved by extruding a kneaded composition of rubber or resin and amino acid into a long string, and then twisting or twisting the dosimeter string as a part of the wire or cable. it can.
The shape of the cord is not particularly limited, and may be rod-shaped, columnar, tube-shaped, or sheet-shaped.

To obtain the radiation exposure distribution of electric wires / cables,
The exposure dose of radiation can be easily measured by cutting out the amino acid dosimeter portion of the electric wire / cable in the target section and using an electron spin resonance apparatus (ESR) by the means disclosed in the above patent application publication.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a dosimeter composite cable, and FIG. 2 is a side view showing a part thereof. That is, this dosimeter composite cable is composed of a dosimeter section 6, an electric wire / cable section 7, and a bridge section 8 connecting them.

The electric wire / cable portion 7 is formed, for example, by integrating three core wires covered with the insulator 4 on the conductor 3 by the twisted sheath 5, but this is not limited to a three-core electric wire / cable, but a two-core wire. Alternatively, a 4-core electric wire / cable may be used.

The dosimeter unit 6 is made of polyethylene [Z-26 manufactured by Ube Industries, Ltd.
5] Alanine [Wako Pure Chemical Industries, Ltd. special grade] is added to 100 parts by weight of 20
0 part by weight and 0.1 part by weight of 4-hydroxymethyl-2,6-di-tert-butylphenol are mixed in a mixing roll at a temperature of 120.
A dosimeter 1 kneaded at ℃ to make a uniform composition is formed into a rod shape by extrusion, etc. If necessary, a thermo label 2 is manufactured in a tape shape to detect the temperature, and this is put around the dosimeter 1. It is formed by pasting. The dosimeter section 6 and the electric wire / cable section 8 form a gourd-shaped bridge section 8 having a window opening 9, and these are integrated into a sheath 5
Formed by extrusion coating.

Therefore, since the dosimeter section 6 is formed apart from the electric wire / cable section 7 by the bridge section 8 having the window 9 opened in the longitudinal direction, an accurate radiation dose can be obtained without being affected by the heat generation of the power cable. The dose can be measured.
Further, since the dose is measured, even if the dosimeter unit 6 is cut off from the dosimeter composite cable, the cable unit 7 is not affected at all.

By the way, the alanine dosimeter 1 has a temperature characteristic as shown in FIG. That is, the dose response is somewhat dependent on the temperature during radiation irradiation, and tends to increase as the temperature increases. This temperature coefficient in the range of -40 ℃ to 50 ℃ is + 0.29% based on the temperature of 25 ℃ in the case of 1KGy.
/ ° C. The dose response after irradiation is very stable at room temperature (about 1% per year for a 1KGy irradiation element), but the higher the dose, the higher the storage temperature and humidity.
(Reference Radiation Process Symposium (1987.11.16,1
7)) On the other hand, when the power cable is energized at the maximum allowable current, the sheath temperature will exceed 50 ° C. When the self-heat of such a power cable exceeds 50 ° C., it becomes impossible to determine whether the dosimeter 1 is exposed to γ rays or the temperature as described above. Therefore, the dosimeter composite cable has a structure in which the dosimeter unit 6 and the cable unit are separated by the window opening bridge 8.

In addition, there are many steam pipes at nuclear power plants, and cables running near them will be affected. For this reason, in this dosimeter composite cable, the thermometer label 2 is formed in a tape shape on the dosimeter section 6 and wound around the dosimeter 1. Needless to say, a separator tape may be further added to prevent heat history when extrusion-coating the sheath 5 for moisture prevention.

Next, the effect of this dosimeter composite cable will be described. Dosimeter composite cable 15 shown in FIGS. 1 and 2
Arrange the length of m arbitrarily around the ⁶⁰ C ₀ -γ-ray source, and cut out only the dosimeter unit 6 every 50 cm into a length of 3 cm after 6 months,
A total of 31 devices were obtained along the length direction and used as samples. The relative amount of free radicals in each sample was determined by using an electron spin resonance system (ESR). The measurement conditions of the electron spin resonance device at this time are the modulation frequency
100kHz, Mod.2G, Power 4mW, room temperature measurement. The actual dose was further determined by comparison with a dose-free radical relative amount reference line.

The results are shown in FIG. The radiation dose distribution along the cable length direction is clearly visible.

In particular, when the cable generates heat from the power cable, it is necessary to consider the temperature correction for the dosimeter. However, this dosimeter composite cable has a cable unit 7 main body as shown in FIGS. 1 and 2. Since the dosimeter unit 6 is formed apart from the above, the influence of the temperature of the cable body can be ignored. Further, since the thermo label 2 is attached for heat detection, it is possible to detect the temperature at the same time and the correction thereof is easy. Further, the dosimeter can be easily separated from the required position.

[Advantages of the Invention] As described above, when the dose composite cable of the present invention is used, the radiation dose along the length direction of the electric wire / cable in the radiation environment does not require any large-scale preparation in advance. It becomes possible to measure extremely easily. Therefore, the effect is extremely large in the industry both economically and in terms of safety measures.

[Brief description of drawings]

1 and 2 are a sectional view and a side view of a dosimeter composite cable showing an embodiment of the present invention, FIG. 3 is a graph showing a measurement result of a dose distribution in a cable length direction, and FIG. 5 is a graph for explaining the influence of the temperature of the dosimeter. 1 ... Amino acid dosimeter 2 ... Heat detection member 3 ... Conductor 4 ... Insulator 5 ... Sheath 6 ... Dosimeter section 7 ... Wire / cable section 8 ... Bridge section 9 ... Window opening section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-58-94705 (JP, A) JP-A-61-57878 (JP, A) JP-A 61-97585 (JP, A) JP-A 62- 299781 (JP, A) Actually opened 48-49565 (JP, U) Actually opened 60-126916 (JP, U) Actually opened 62-10686 (JP, U) Actually opened 62-69320 (JP, U) Actual Kai 1-117010 (JP, U) Special Table 3-503085 (JP, A)

Claims (2)

[Claims] 1. A cross-sectional shape is formed into a gourd shape by connecting a dosimeter section consisting of an amino acid dosimeter element using a polymer as a binder and a heat detecting member to an electric wire / cable section with a window opening bridge section. Dosimeter composite cable. 2. The dosimeter composite cable according to claim 1, wherein the amino acid is alanine.