JPH0313891A - Stud hole plug of nuclear reactor vessel - Google Patents

Abstract

PURPOSE:To make plug handling work easy by arranging an intermediate ring capable of axial movement between an upper mutually-screwable structure and a lower structure to set a circular flexible sealant between its ring and the lower structure so as to abut on the plug-attached face of a stud hole. CONSTITUTION:A plug 1 is constituted of upper and lower structures 1a, 1c and an intermediate ring 1b to penetrate the ring 1b to extend by the use of a male screw projection of the lower face of the structure 1a so as to screw with a female screw projection. A cut part of the projection of the structure 1c can be engaged with the projection of the ring 1b to protect the ring 1b from being rotated so as to rotate the structure 1a alone. And a circular flexible sealant 1d provided between the ring 1b and the structure 1c is sandwiched in a compressed condition to insert a coil spring 1e in each circular groove of the lower face of the ring 1b and the upper face of the structure 1c so as to protect the sealant 1d from being compressed. Thereby, the plug 1 is inserted in a stud hole 4d to compress the sealant 1d by the use of the rotation of the structure 1a so as to fit on the plug-attached face 4c.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a plug for a stud hole in a nuclear reactor vessel, that is, a plug that is installed in a screw hole, that is, a stud hole after removing a stud bolt of a nuclear reactor vessel. It is.

[Prior Art] As shown in FIG. 6, in a nuclear reactor installed in a reactor cavity 7, a plurality of stud bolts 5 are normally attached to the upper N3 on the upper flange 4a of the reactor vessel 4 is installed to seal the reactor vessel 4. When opening the upper cover 3 of the reactor vessel 4 during periodic inspections of the reactor, etc., after removing the stud bolt 5 screwed into the reactor vessel flange 4a, remove the stud bolt 5 for the same stud bolt 5. In order to protect the hole 4d with waterproofing, it is customary to attach a plug with an O-ring to the upper part of the stud hole using a special tool. Further, this plug must be removed from the reactor vessel 4 after the upper M3 is reattached to the reactor vessel 4 and before being fixed with the stud bolt 5.

Figures 7 and 8 show the stud pole 4 shown in Figure 6.
d shows a plan view and a partially cutaway cross-sectional view of a conventional plug 2 inserted into a plug 2, in which an O-ring 2a fits into a groove formed on the circumferential surface of the substantially cylindrical plug 2. Moreover, one screw hole 2b is formed in the center of the circular upper surface, and a plurality of bottle holes 2C are formed around the screw hole 2b.

Such attachment and removal of the plug 2 to the stud hole 4d is not only done to prevent foreign matter from falling into the reactor vessel, but also from the perspective of reducing radiation exposure to workers.
Although the stud bolts 5 (FIG. 6) are of course removed, the process is carried out with the upper cover 3 placed on the reactor vessel 4.

That is, as shown in FIG. 9, the upper M3 is the stud bolt 5.
(FIG. 6) is placed on the reactor vessel 4 in a removed state. Insert the plug 2 into the stand hole 4 of the reactor vessel 4.
d, first insert the bottle part 6e of the plug handling tool 6 into the bottle hole 2C of the lug 2, and then turn the butterfly nut 6c at the top of the rod 6b to tighten the tip of the rod 6b. It is necessary to screw into the screw hole 2b of the plug 2 and assemble the plug handling tool 6 and the plug 2. Thereafter, the plug 2 with the O ring 2a installed in advance is inserted into the upper part of the stud hole 4d through the illustrated through hole in the upper cover 3 using the plug handling tool 6, and the O ring 2a of the plug 2 and the stud hole 4d of the upper flange 4a are inserted. The stud hole 4d was sealed by closely contacting the plug mounting wall surface 4c formed in the stud hole 4d.

[Problems to be Solved by the Invention] However, when inserting the plug 2 into the stud hole 4d in this way, the operator
Since the O-ring 2a of the plug 2 is slid along the plug mounting wall surface 4C and inserted to a predetermined position while grasping the O-ring 2a, there is a possibility that the O-ring 2a may be damaged and the sealing function may be adversely affected.

Moreover, in the above-mentioned plug, the stud hole 4d
When inserting the plug 2 into the stud hole 4d, the air is compressed because there is no escape route for the air in the stud hole 4d, and the plug 2 cannot be inserted by just pressing it lightly, making the insertion work extremely forceful. Also, when removing the plug,
Workability was similarly poor because the ring 2a and the plug mounting wall surface 4c were in close contact with each other with strong force.

As described above, with the conventional plug, there is a possibility that the O-ring may be damaged, and the workability of installing and removing the plug is poor, and it takes a relatively long time.

Therefore, it is an object of the present invention to not only not affect the sealing function, but also to reduce radiation exposure.
To provide a plug for a stud hole in a reactor vessel that is easy to remove.

[Means for Solving the Problems] For the above-mentioned purposes, the plug of the present invention, which is inserted into a stud hole of a reactor vessel in a sealing relationship, has a lower structure, a lower structure that is screwed into the lower structure, and a lower structure that is screwed into the lower structure. , an intermediate ring disposed between the lower structure and the upper structure to be movable in the axial direction with respect to the lower structure; and between the circumferential surfaces of the intermediate ring and the lower structure, the intermediate ring is disposed between the lower structure and the upper structure. and an annular flexible sealing material arranged so as to be compressed when moving toward the lower structure and abut against a plug mounting wall surface of the stud hole.

In a preferred embodiment, the upper surface of the plug superstructure is provided with threaded and bottle holes similar to conventional plugs to allow use of existing plug handling tools.

For example, when inserting the plug of the present invention into a stud hole, first attach the plug of the present invention to a plug handling tool 9 Then, operate the plug handling tool to place the plug in a predetermined position in the stud hole. However, at this time, the sealing material is not substantially compressed in the axial direction and does not protrude outward in the radial direction from the circumferential surface of the plug.
The sealing material does not slide along the wall surface of the stud hole, and the air within the stud hole is not compressed.

After setting in the default position, when the upper structure is rotated by operating the plug handling tool, the upper structure advances toward the lower structure, and at the same time, the intermediate ring also advances in the same direction, so that the sealing material is axially It bulges outward in the radial direction and abuts against the wall of the stud hole in a sealing relationship.

When removing the plug attached to the stud hole,
This procedure is easily performed without damaging the sealing material.

[Embodiments] Next, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which the same reference numerals indicate the same or corresponding parts.

1 and 2 show a partially broken sectional view and a plan view of a stud hole plug 1 according to the present invention.

As shown in these figures, the plug 1 has a three-part structure consisting of an upper structure 1a, an intermediate ring tb, and a lower structure 1c that are fitted together.

On the upper surface of the superstructure 1a, there is one screw hole 1j in the center and one screw hole 1j around it so that it can be connected to the existing practicum 6 described in connection with FIG. Multiple pieces (
In the embodiment, four (4) bottle holes 1 are formed. As with conventional plugs, the plug 1 is attached and removed through the screw hole 1j.

In addition, in this embodiment, a plug handling tool 6 is inserted into the bottle hole 1k.
The structure is such that only the upper structure 1a can be rotated by inserting the bottle part 6e and turning the handle part 6a of the plug handling tool 6.

That is, as can be understood from FIG. 1, from the lower surface of the upper structure la, a protrusion having a male thread on the outer peripheral surface extends downwardly through the intermediate ring 1b, while the lower structure IC
From the upper surface of the ring, a protrusion having a female thread inside thereof extends upward almost through the intermediate ring 1b, and the male thread is screwed into the female thread.

In order to ensure smooth rotation of the upper structure 1a, in the embodiment, two spherical seats 1g are formed on the interface between the upper structure 1a and the intermediate ring 1b. Further, as can be understood from FIGS. 1 and 2, four notches 11 spaced apart in the circumferential direction are formed on the upper peripheral edge of the protrusion of the lower structure IC, and an intermediate ring 11) There is a notch 11 on the inner peripheral edge of the
protrusions 1h as stoppers spaced at the same angular intervals as
extends inward in the radial direction, and the protrusion 1h is connected to the notch 1.
It is designed to fit into 1. With such a structure, it is possible to prevent the rotation of the intermediate ring 1b while allowing its axial movement, and to rotate only the upper structure 1a.

The combination of the notch 11 and the protrusion 1h is the intermediate ring 1.
b is prevented from rotating, but is allowed to move in the axial direction. Therefore, the intermediate ring 1b and the lower structure 'j
An annular flexible sealing material 1d between the circumferential surfaces of the JIA 1c is held between them in a compressed state. Further, annular grooves are formed in the lower surface of the intermediate ring 1b and the upper surface of the lower IC, and a coil spring 1e, for example, is inserted into the annular grooves, and when the plug 1 is inserted, This prevents the sealing material 1d from being excessively compressed by the weight of the intermediate ring 1b. Also, when removing plug 1,
Since it is necessary to return the sealing material 1d to the state when the plug 1 was inserted, the coil spring le also has the role of pushing up the intermediate ring 1b. The sealing material 1d has a function of sealing between the plug 1 and the plug mounting wall surface 4C of the stud hole 4d, as will be described later.

Furthermore, the outer periphery of the protrusion of the lower structure 1c and the intermediate ring 1b
An O-ring 1f is provided between the inner periphery of the reactor cavity 7 and the water 9 inside the reactor cavity 7.
(See FIG. 5) is prevented from entering the stud hole 4d through the space between the upper structure 1a and the intermediate ring 1b.

To assemble the plug 1 of the present invention described above, first, the O-ring 1f and the coil spring 1e are attached to the lower structure 1c, and the intermediate ring 1b is inserted so that its protrusion 1h fits into the notch 11 of the lower structure 1c. After attaching it to the lower structure 1c,
The male threaded portion of the upper structure 1a is screwed into the female threaded portion of the lower structure 1c. This screwing is adjusted so that the sealing material 1d, which is then pushed between the intermediate ring 1b and the lower structure 1c, is not excessively compressed and protrudes from around the plug 1 (see FIG. 3). It is best to perform this work in advance in another location that will not be exposed to radiation.

Next, using the plug handling tool 6 shown in FIG. 9, the plug 1 adjusted as described above is inserted into the stud hole 4d. As described above, the plug handling tool 6 includes a handle portion 6a, a rod 6b, an upper butterfly nut 6c, a lower butterfly nut 6d, a bottle portion 6e, a guide vibro r, and the like. The plug handling tool 6 can be used by turning the upper butterfly nut 6c fixed to the rod 6b.
b represents the handle portion 6a, the pin portion 6e, and the guide vibro f.
By moving the handle part 6a in the axial direction, the bottle part 6e is rotated via a guide vibro.

The lower butterfly nut 6d is free, and the rod 6b can be fixed by tightening it against the handle portion 6a.

Therefore, with the pin part 6e of the plug handling tool 6 fitted into the pin hole 1k of the plug 1, if you loosen the lower butterfly nut 6d and turn the upper butterfly nut 6c in a predetermined direction, the tip of the rod 6b will be inserted into the plug hole 1k. The plug 1 is screwed into the screw hole 1j formed in the upper structure 1a of the plug 1 by the plug handling tool 6.
is maintained. Next, the held plug 1 is
As shown in the figure, it is inserted into the predetermined position of the stud hole 4d (the plug handling tool 6 is not shown in FIG. 3). At this time, the sealing material 1d has not yet protruded from the circumferential surface of the plug 1, so that the sealing material 1d is not damaged and can be easily inserted.

After inserting the plug 1, rotate the handle part 6a to the right as shown in Fig. 4 (in Fig. 4, the plug handling tool 6a
), only the lower structure 1a of the plug 1 rotates and advances toward the lower structure 1c, and the sealing material 1d between the intermediate ring 1b and the lower structure IC is compressed in the axial direction. The plug bulges outward in the radial direction and comes into close contact with the plug mounting wall surface 4c of the stud hole 4d in a sealed state.

In this way, the installation of the plug 1 into the stud hole 4d is completed.

After installation is complete, remove the lower butterfly nut 6d of the plug handling tool 6.
, and turn the upper butterfly nut 6C in the opposite direction to allow the rod 6b to escape from the screw hole 2b of the plug 1, and to separate the plug handling tool 6 from the plug 1.

FIG. 5 shows a state in which the top cover 3 is removed after the plugs 1 are inserted into all the stud holes 4d as described above. These plugs 1 can be removed by placing the upper cover 3 on the reactor vessel 4 and then using the above-mentioned plug handling tool 6 in the reverse procedure.

[Effects of the Invention] As described above, the plug according to the present invention is configured so that the sealing material does not protrude outward in the radial direction from the circumferential surface of the plug when the plug is inserted into or pulled out from the stud hole. Not only does the sealing function of the
It is extremely easy to attach and detach from the stud hole.
It can greatly contribute to reducing the radiation exposure of workers.

Additionally, since the air in the stud hole is not compressed during insertion, the top surface of the plug can be flush with the top flange surface of the reactor vessel, making it easier to decontaminate the top flange surface. Become.

Moreover, in the preferred embodiment, the screw hole and bottle hole are formed on the top surface of the upper part of the plug, as in the past, so that the plug can be inserted into the stud hole using an existing plug handling tool. Can be attached and detached.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway elevational view of an embodiment of the plug according to the present invention, FIG. 2 is a partially cutaway plan view of the plug of FIG. 1, and FIG. Figures 1 and 4 show the plugs shown in Figures 1 and 2 immediately after they are inserted into the stud holes, and Figure 4 shows the plugs shown in Figures 1 and 2 before being compressed. A diagram corresponding to FIG. 1 after the sealing material has been compressed, and FIG. 5 show a state in which the reactor vessel top cover has been removed after the plug of the present invention has been inserted into the stud hole formed in the upper flange of the reactor vessel. FIG. 6 is a cross-sectional view showing how the reactor vessel and its top cover are connected by stud bolts, FIG. 7 is a plan view of a conventional plug, and FIG. FIG. 9 is a partially cutaway elevational view of the plug shown in the figure, and FIG. 9 is a sectional view for explaining the operation of the plug handling tool.

Claims (1)

[Claims] A plug inserted into a stud hole of a reactor vessel in a sealing relationship, the plug comprising: a lower structure, an upper structure threadedly engaged with the lower structure, and between the lower structure and the upper structure;
an intermediate ring disposed to be movable in the axial direction with respect to the lower structure; and between the intermediate ring and the circumferential surface of the lower structure;
and an annular flexible sealing material arranged so as to be compressed when the intermediate ring moves toward the lower structure and come into contact with a plug mounting wall surface of the stud hole. Hall plug.