JPH1039090A - Method and system for reducing radiation at the time of work at lower mirror part of vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the workability by fixing a magnet to a seal pipe arranged around a piping through hole and deflecting the upward radiation in the seal pipe by a field generated from the magnet thereby reducing the radiation leaking into the upper space. SOLUTION: A seal pipe 11 is arranged to surround the piping through a hole 2 at the lower mirror part 1 of a vessel a vessel through pipe 3 and a stub tube 4 while a sealing material is arranged at the contact part between the lower end of the seal pipe 11 and the inner face of the lower mirror part 1 of the vessel. Consequently, a sealing part 13 is formed and an atmosphere isolated from cooling water W for reactor is brought about in the seal pipe 11. The seal pipe 11 is fixed, to the outer circumferential surface thereof at a position lower than the level of the reactor cooling water W, with a pair of magnets 12 having N and S poles. The upward radiation in the inner space of the seal pipe 11 is deflected gradually to the direction intersecting the line of magnetic force perpendicularly. It is deviated from the seal pipe 11 and attenuated while intersecting the water W. Consequently, the radiation to be radiated directly upward can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for reducing radiation during operation of a lower mirror section of a container.

[0002]

2. Description of the Related Art As shown in FIG. 2, for example, Japanese Utility Model Application Laid-Open No. 06-033137 discloses a container penetrating pipe (a lower mirror portion) 1 through a pipe penetrating hole 2 in a reactor pressure vessel. A stub tube 4 is erected at the inner bottom of the lower mirror unit 1 so that the penetrating tube 3 penetrates and extends the container penetrating tube 3 upward. 3 describes a technique for integrating the outer peripheral surface with a welded portion 5.

[0003] In such a vessel penetrating pipe 3, when exchanging or repairing the vessel penetrating pipe 3 and the welded portion 5, it is desirable to reduce the radiation exposure by making the corresponding portion underwater. If the working environment is set in water, the workability is likely to be impaired.

[0004] Techniques for improving the workability include:
For example, it is effective to surround the stub tube 4 with a long seal pipe to isolate it from the reactor cooling water and to make the inside of the seal pipe an air atmosphere.

[0005]

However, when the inside of the seal pipe is made to have an air atmosphere, the amount of radiation leaking upward through the pipe hole of the seal pipe becomes large, and the radiation exposure dose is sufficiently controlled. Is required.

The present invention has been made in view of such circumstances, and aims to achieve the following objects. To reduce the amount of radiation leakage to the upper space. Improve workability. Facilitate installation for radiation leakage countermeasures and reduce installation and removal labor.

[0007]

When working in the lower mirror portion of the container, a seal pipe is arranged around the pipe through hole to create an air atmosphere in a state where the pipe through hole is isolated from water, and the seal pipe is provided. By attaching a magnet to the magnet and deflecting the radiation going upward through the inside of the seal pipe by the generated magnetic field and guiding it in the direction crossing the water, the radiation is attenuated, and the radiation is directly radiated upward. This suppresses the occurrence of a phenomenon. The magnet is usually mounted on the outer peripheral surface of the seal pipe so that the vertical position can be adjusted, and the emission direction of the radiation is adjusted by the vertical adjustment as necessary.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a method and an apparatus for reducing radiation during operation of a lower mirror section of a container according to the present invention. In FIG. 1, H is a working device, reference numeral 11 is a seal pipe, 12 is a magnet, and 13 is a seal portion.

In the seal pipe 11, when various operations are performed in the lower mirror section (lower mirror section) 1 of the container,
A seal pipe 11 is arranged so as to surround the pipe penetration hole 2, the vessel penetration pipe (penetration pipe) 3, and the stub tube 4, and the lower end of the seal pipe 11 and the vessel lower mirror 1
The seal portion 13 is formed by arranging a seal material at a contact portion with the inner surface of the seal pipe 11 to make the inside of the seal pipe 11 an air atmosphere in a state of being isolated from water (reactor cooling water W).

That is, the upper opening of the seal pipe 11 is
By setting the length so as to be higher than the liquid level of the water W, the pipe penetration hole 2, the container penetration pipe 3, the stub tube 4, the welding portion 5, etc., located inside the seal pipe 11 Is set to be an air atmosphere.

[0013] The seal pipe 11 houses therein working equipment H for performing machining and welding work of the stub tube 4 and the like, and additionally has a level lower than the liquid level of the reactor cooling water W. For example, a pair of magnets 12 having an N pole and an S pole are attached to the outer peripheral surface of the position using bolts, nuts, bands, or the like.

The magnet 12 is, for example, a permanent magnet, and a magnetic flux φ generated by an N pole and an S pole as shown by a broken line in FIG. 1 crosses the internal space (tube hole) of the seal pipe 11. It is set to be in a state.

If it is assumed that there is radiation going upward in the internal space of the seal pipe 11, the radiation components (α-rays and β-rays) are different as shown in FIG. Is deflected (actually, it is gradually deflected in a direction perpendicular to the line of magnetic force), and a phenomenon occurs in which it is attenuated by coming off the seal pipe 11 and crossing the water W. That is, when the radiation traveling upward in the internal space of the seal pipe 11 is an α-ray and a β-ray, the radiation is deflected by the opposing magnetic field of the magnet 12 and guided to cross underwater, so that the radiation is emitted. This suppresses the occurrence of a phenomenon that is directly radiated upward, and reduces the amount of radiation reaching upward.

[Other Embodiments] The method and apparatus for reducing radiation during operation of the lower mirror section of the container according to the present invention include the following techniques. a) The magnet 12 is an electromagnet. b) The magnet 12 is attached to the seal pipe 11 so that the vertical position can be adjusted, and if necessary, the radiation direction can be adjusted by adjusting the vertical position. c) The magnet 12 is attached to the seal pipe 11 and is attached to and detached from the lower mirror 1 in an integrated state. d) The magnet 12 is attached to the inner peripheral surface of the seal pipe 11.

[0015]

According to the method and the apparatus for reducing radiation during the operation of the lower mirror section of the container according to the present invention, the following effects can be obtained. (1) A seal pipe is arranged around the pipe penetration hole in the lower mirror part of the container, and the inside is isolated from the water to make the working environment an air atmosphere.
By imparting a deflection to the radiation with a magnetic field and guiding the radiation in a direction crossing the water, it is possible to reduce the radiation radiation amount to the upper space serving as the working environment. (2) The work environment in the upper space can be improved and the workability can be improved by guiding the radiation to the water and attenuating the radiation. (3) By supporting the magnet on the seal pipe,
It is possible to easily install a magnet for preventing radiation leakage. (4) The integration of the seal pipe and the magnet can reduce the labor for installation and removal thereof. (5) By attaching the magnet to the seal pipe so that the vertical position can be adjusted, it is possible to adjust the direction of radiation emission, and it is possible to reduce the radiation dose according to the work place and environment.

[Brief description of the drawings]

FIG. 1 is a front sectional view, partially omitted, showing an embodiment of a radiation reducing method and an apparatus therefor according to the present invention when working on a lower mirror section of a container.

FIG. 2 is a front sectional view, partially omitted, showing an example of a mounting structure example of a pipe penetrating a lower part of a conventional reactor pressure vessel.

[Explanation of symbols]

 H Work equipment 1 Container lower mirror part (container wall, lower mirror part) 2 Pipe penetration hole 3 Container penetration pipe (penetration pipe) 4 Stub tube 5 Welded part 11 Seal pipe 12 Magnet 13 Seal part W Water (reactor cooling water) ) Φ magnetic flux

Claims (3)

[Claims] 1. A step of disposing a seal pipe (11) around a pipe penetrating hole (2) to provide an air atmosphere in a state where the pipe penetrating hole is isolated from water;
2) attaching a second magnetic field, wherein the generated magnetic field deflects upward radiation through the interior of the seal pipe and guides the radiation in a direction crossing the water. . 2. A seal pipe (11) arranged around the lower mirror part (1) for isolating a pipe penetration hole (2) from water to provide an air atmosphere, and a seal pipe arranged in the middle of the seal pipe. A magnet (12) that deflects radiation in a direction away from the seal pipe by a magnetic field (φ) formed inside the pipe
A radiation reducing device at the time of operation of the lower mirror section of the container, comprising: The magnet (12) is provided with a seal pipe (11).
3. The radiation reducing device according to claim 2, wherein the upper and lower positions are attached to the outer peripheral surface of the lower surface so as to be adjustable.