JPS59128501A - Radiant ray proof optical fiber - Google Patents

Abstract

PURPOSE:To reduce transmission loss and lowering of mechanical strength even when used in high concentration of neutron by covering the outer circumferential face of an optical fiber bare conductor with a metallic coating layer, a protecting layer and a metallic member successively. CONSTITUTION:Outer circumferential face of an optical fiber bare conductor 1 is covered with a metallic coating layer 2. Outer circumferential face of the layer 2 is coated with a protecting layer 3 that protects the bare conductor 1 from radiant rays especially neutron. Outside of the layer 3 is coated with a metallic member 4 that protects the layer 3. The layer 2 is a metallic layer having about 5-30mum thickness deposited by vacuum vapor deposition (sputtering, chemical vapor phase deposition, dipping) method. Generally, it protects the conductor 1 from moisture generated by decomposition of covering material made of organic material caused by irradiation of radiant rays. For the layer 3, substances that absorb thermoneutron such as Li, B, Cd, Hf, etc., or substances that decelerate neutron such as H, Be, C, N, O, etc. or their compounds are desirable. The conductor 5 can be inserted into an Al tube, etc. as the metallic member 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber having excellent radiation resistance.

Optical fiber has many advantages such as low loss, wide bandwidth, and resource saving.
Due to the characteristics of LfF, its uses are gradually expanding,
It is also becoming widely used in nuclear reactor construction. Among these applications, when optical fibers are used in atmospheres with strong radiation, especially high neutron density, such as in nuclear reactors, the glass forming the bare optical fibers can be exposed to radiation, especially neutron attack for a short period of time. In addition, if the optical fiber is coated with organic matter, the organic matter is decomposed by radiation and produces moisture, which is absorbed by the surface of the bare optical fiber. There are problems such as promoting the growth of defects and causing the optical fiber to break in a short period of time, so the idea for 7t was not made in consideration of the above circumstances f'L7! j thing.

We provide highly radiation-resistant optical fibers that have excellent long-term reliability and minimal increase in transmission loss and minimal deterioration in mechanical strength even when used in environments with high radiation, especially neutron density, such as inside nuclear reactors. The purpose is to

Hereinafter, the present invention will be described in detail with reference to the drawings.

The figure shows one example of the radiation-resistant optical fiber of the present invention, and reference numeral 1 in the figure is a bare optical fiber mainly made of quartz (S10□). The outer peripheral surface of this bare optical fiber l is coated with a metal coating layer 2, and the outer peripheral surface of this metal coating layer 2 is coated with a protective layer 3 that protects the bare optical fiber 1 from radiation, especially neutrons. The outer side of the protective layer 3 is coated with a metal member 4 that protects the protective layer 3.

The metal coating layer 2 is formed to a thickness of 5 to 30 μm by vacuum evaporation, sputtering, chemical vapor deposition, dipping, etc.
A dense metal layer of m is formed on the outer peripheral surface of a bare optical fiber l. Primarily, this metal coating layer 2 is applied to radiation as shown in #, and for this first purpose, St, Sn, Al1, G
e, In, W, Ni, Bi, Be, Cu,
Although various metals such as Ag and Pb can be used, it is desirable that this metal coating layer 2 also have the ability to protect the bare optical fiber l from radiation. 1 Used for reflective materials, etc.
Be, which has a high ability to absorb γ-rays, or Bx, Pb, which has a high ability to absorb γ-rays.
It is appropriate to use metals such as Bl, P, among others.
It is a suitable material that has a low melting point and can be easily coated by dipping.

The protective layer 3 provided on the outer peripheral surface of the metal coat layer 2 is
lB106% Substances with superior ability to absorb thermal neutrons such as Hf, substances with superior ability to slow down neutrons such as H, Be, C, N, O, or compounds of these substances, or Although it is made of materials containing these substances and compounds, when considering workability and safety during the production of radiation-resistant optical fibers, organic substances, graphite (
C), boron carbide (B4C), boron nitride (B,,
It is appropriate to use Nl or the like. A suitable manufacturing method for forming the protective layer 3 is to use C1B on plastic.
4C.

There is a method of mixing BN etc. and coating the surface of the metal coat layer 2 by extrusion molding, or a method of dispersing C1 organic matter, B4C, and BN in a binder such as water glass and coating it on the outer peripheral surface of the metal coat layer 2. A coating method is used.

The thickness of the protective layer 3 depends on the radiation resistance performance required of the radiation-resistant optical fiber of the present invention, the material forming the protective layer 3, the method of coating the protective layer 3, etc., but in general, It is approximately 0.5 to 1 ovL.

The protective layer 3 is protected and held by the metal member 4.

The metal member 4 wraps a wire 5 made of a bare optical fiber l, a metal coat layer 2, and a protective layer 3. The method for forming the metal member 4 is to wrap the wire 5 in a metal tube such as aluminum. A method of inserting the metal tube into the metal member 4 and using the metal tube as the metal member 4.

A method of covering the wire 5 with metal may be considered.

The bare optical fiber l protected by the protective layer 3 can be protected by the protective layer 3 even if exposed to radiation such as neutron beams.
Since the energy of the neutrons is reduced to a certain bm', deterioration and damage to the optical fiber and bare wire l are reduced. Furthermore, even if the material forming the protective layer 3 is decomposed by radiation such as neutrons and produces moisture, the bare optical fiber 1 is protected by the metal coating layer 2, so surface defects of the bare optical fiber 1 will be removed by moisture. Since there is no growth, the lifetime of the optical fiber is not shortened because of this.

Hereinafter, the present invention will be specifically explained with reference to Examples.

[Example 1] A metal coating layer 2 made of Bl 2 was formed to a thickness of 15 μm on the surface of a bare optical fiber 1 having a core diameter of 50 μm and an outer diameter IZfS#+ by a dipping method.

Next, a solution in which B4C, a neutron absorbing substance, was suspended in a water glass aqueous solution as a binder at a weight ratio of water glass/B4C-2/1 was applied to the surface of the metal coating layer 2 by brushing, and the solution was dried. Then bake at 200-300℃. This operation was repeated several times to form the protective layer 3 until the outer diameter became 1.5+m, and the protective layer 3 was sealed in an M pipe as a metal member 4 having an outer diameter of 3y and an inner diameter of 1.51LIE.

When this radiation-resistant optical fiber was used for 5 years as a VC for measurement and control equipment in a nuclear reactor, three of the standard fiber coated fibers were broken in 5 water, and the transmission loss was so large that it became unusable. On the other hand, all of the radiation-resistant optical fibers were usable.

Example pixel fi20000, an image fiber made of quartz material with an outer diameter of 2u was used as the bare optical fiber 1, and Bt was used as the bare optical fiber 1.
The metal coating layer 2 consisting of
It was coated with a thickness of μm. B on the surface of this metal coat layer 2
Sixth nylon 6 mixed with 20vrt of N was coated by extrusion molding, and the outer diameter was set to 5n. This was enclosed in a repipe E7 with an outer diameter of 8mm and an inner diameter of 5u.

This radiation-resistant optical fiber was used in a nuclear reactor with a monitoring equipment.There were only 9 cases of one fiber being broken underwater. Since the outer circumferential surface is coated with a metal coating layer and a protective Nj1 metal member in sequence, there is little increase in transmission loss even when used in an atmosphere with a high density of radiation, especially neutrons, such as inside a nuclear reactor. It becomes a superior n-order optical fiber with long-term reliability and little deterioration in strength.

[Brief explanation of drawings]

The figure is a partially cross-sectional perspective view showing the radiation-resistant optical fiber of the present invention. 1... Bare optical fiber, 2... Metal coat layer, 3... Protective layer, 4... Metal member.

Claims (3)

[Claims] (1) A metal coating layer is provided on the outer peripheral surface of the bare optical fiber to protect the bare optical fiber, a protective layer that absorbs and decelerates neutrons is provided on the outer peripheral surface of this metal coating layer, and the outside of this protective layer is A radiation-resistant optical fiber characterized in that a metal member is provided to protect the above-mentioned protective layer. (2) The metal forming the metal coating layer is bismuth (Bz)
The radiation-resistant optical fiber according to claim 1, characterized in that it is lead (Pbl). (3) The material forming the protective layer is graphite (C),
111. The radiation-resistant optical fiber according to claim 111 or 2, wherein the radiation-resistant optical fiber is a phosphorescent substance mixed with at least one species.