JPH0727060B2 - A device that applies a turning force to the shield plug - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus used for withdrawing a shield plug inserted in a lower extension tube of a pressure tube of a pressure tube reactor. . More specifically, when the shield plug held by the ball latch mechanism in the pressure pipe lower extension pipe is pulled out by releasing the ball latch mechanism, when the ball latch mechanism cannot be released smoothly, The present invention relates to a device for applying a rotational force to a shield plug to enable smooth release of a ball latch mechanism.

<Prior Art> As is well known, pressure tube reactors support a large amount of fuel assemblies and coolant in pressure tubes of appropriate thickness to support the pressure associated with high-temperature and high-pressure coolant. By doing so, the core is constructed. At the end of the lower extension pipe of the pressure pipe, a plug called a seal plug prevents leakage of high temperature and high pressure coolant, and a shielding plug is inserted above the seal plug to shield radiation. Has become. The shield plug is connected to the fuel assembly at its upper end, and is inserted into the pressure pipe together with the fuel assembly.

As shown in FIG. 4, the shield plug 10 is held in the pressure pipe lower extension pipe 20 by a ball latch mechanism. That is, the ball 12 fitted in the ball mounting hole 11 of the shield plug 10 is pressed outward in the radial direction of the shield plug by the latch body 14 which is always elastically pressed downward by the spring 13, and is machined on the inner wall of the extension pipe 20. It is in a state that it is fitted in the recessed groove 21 formed by the
20 Can be held in place.

When exchanging the fuel assembly in the pressure pipe, it is necessary to pull out the shield plug from below the lower extension pipe of the pressure pipe by releasing the ball latch mechanism of the shield plug using the fuel exchanger. FIG. 5 is a diagram for explaining the operation of the fuel exchange machine. The tip of the fuel exchange machine grab 30 introduced from the lower end of the pressure pipe lower extension pipe 20 is inserted from the opening 15 of the shield plug lower end 15 (FIG. 5A), A piston that moves axially up and down within the grab when the grab is properly fitted to the shield plug by the ball latch mechanism of 30
The latch body 14 of the shield plug is pushed up by raising (Fig. 5B). The sixth step of releasing the ball latch mechanism of the shield plug by pushing up the rack body 14
Shown in the figure. FIG. 6A shows a state in which the shield plug 10 is held by the ball latch mechanism, and the ball 12 is inserted into the extension pipe recess groove 21 by the latch body 14 which is elastically pressed downward by the spring 13 (see FIG. 4). Pressed. FIG. 6B shows the state where the latch body 14 is pushed up by the piston of the grab of the refueling machine, and the recess groove 16 machined on the outer wall of the latch body is at the same level as the ball 12.
In this state, due to the taper effect of the extension pipe recess groove 21, the balls 12 are pushed inward in the radial direction of the shield plug,
As shown in FIG. C, as a result of the balls 12 being housed in the latch body recess grooves 16, the ball latch mechanism is released. By lowering the fuel exchanger in this state, it is possible to extract the fuel assembly together with the shielding plug from the pressure pipe, and it is possible to perform fuel exchange.

<Problems to be Solved by the Invention> As described above, when the ball latch mechanism of the shield plug is released, the balls 12 are pushed inward in the shield plug radial direction by the taper effect of the recess groove 21 of the pressure pipe lower extension pipe. It depends on just that. However, when the plant is operated under high temperature and high pressure for a long time, the parts 11a and 11b of the ball mounting hole 11 of the shielding plug shown in FIG. It is conceivable that the ball 12 may become stuck at the portion 21a of. In such a case, the conventional refueling machine does not have a mechanism for pulling the balls 12 inward in the shield plug radial direction, so the taper effect does not work due to the recess groove 21, and as a result, the ball latch of the shield plug does not function. It becomes impossible to release the mechanism smoothly.

Therefore, an object of the present invention is to fix the ball in the ball latch mechanism of the shield plug as described above without changing the structure of the conventional shield plug and the fuel exchanger and without affecting the normal operation of the plant. An object of the present invention is to provide a device that can easily and reliably cancel a phenomenon.

<Means for Solving Problems> When a ball sticking phenomenon occurs in the ball latch mechanism of the shield plug, the ball may be forcibly rotated by some means.

In this invention, it is an object of the present invention to provide a device that applies a rotational force to the shield plug so as to forcibly rotate the ball by rotating the shield plug in the circumferential direction.

That is, a device for applying a rotational force to a shield plug according to the present invention will be described with reference to FIG. 1 showing an embodiment of the present invention, in which an axial vertical movement of a piston 31 of a conventionally used refueling machine grab 30 is rotated. Ball screw that transforms into motion
40, a rotating disc 50 horizontally arranged above the ball screw and rotated by the rotating force of the ball screw, and a ball horizontally arranged above and below the rotating disc so as to sandwich the rotating disc and having a diameter larger than that of the rotating disc. It is composed of holding discs 60, 61 and a plurality of balls 70 rotatably placed on the outer periphery of the rotating disc between the ball holding discs. The ball holding disc 60.61 has a diameter capable of fitting in the lower opening of the shield plug, and the outer periphery of the rotating disc 50 pushes the ball 70 radially outward of the rotating disc by the rotation of the rotating disc. It has a shape that can be put out.

<Action> The ball screw 40 allows the piston 31 of the refueling machine grab 30 to be
The up-and-down movement in the axial direction of is converted into a rotational movement in the direction perpendicular to the axis, and this rotational force is then transmitted to the rotary disc 50. Therefore, with the ball holding disc 60.61 and the rotating disc 50 fitted in the bottom opening of the shielding plug, the piston 31 of the fuel exchanger grab 30 is
Is raised and the ball screw 40 is operated, the rotating disc 50
Can rotate to push the ball 70 outward in the radial direction of the rotating disk. When the ball 70 is pushed out and comes into pressure contact with the inner wall of the shield plug lower end portion, the rotational force of the rotating disk 50 is transmitted to the shield plug lower end portion via the ball 70, and the shield plug can be rotated.

Thus, the ball 12 of the ball latch mechanism of the shield plug
Even when (Fig. 4) is fixed, these balls 12 rotate in the ball mounting holes 11 as the shield plug rotates, and as a result, the fixation of the balls 12 can be released.

<Embodiment> FIG. 1 is a view for explaining a preferred embodiment of the device of the present invention, showing a state in which the device of the present invention is fitted in the opening 15 of the shield plug lower end, and the broken line in the figure 1 shows a refueling machine grab 30 with the device attached.

This device uses a ball screw 4 that converts vertical movement into rotational movement.
0, a rotating disc 50 horizontally arranged above the ball screw, and ball holding discs 60, 6 arranged in parallel above and below the rotating disc so as to sandwich the rotating disc and having a diameter larger than that of the rotating disc.
1. It has a plurality of balls 70 rotatably placed on the outer circumference of the rotating disk between these ball holding disks.

As shown in FIG. 2, the ball screw 40 has a screw shaft 41 and a nut 42, which are equivalent to male threads, each having a thread groove.
A ball screw having a structure in which balls 43 for rolling bearings are arranged in a row in a coil-shaped space formed by facing one screw groove and having such a structure is well known. The screw shaft 41 and the nut 42 mutually perform linear movement and rotational movement, as in the case of an ordinary slide screw. Screw shaft
When the nut 42 is rotated with respect to 41, the ball 43 rolls in the coiled space and circulates through a circulation path 44 provided in the nut 42. Such a ball screw 40 generally has good screw efficiency, can reduce backlash, and can maintain high precision for a long time. Lubrication has the advantages that it does not require as much attention as a slide screw and that it is less worn by dust.

At the lower end of the screw shaft 41 of the ball screw,
A piston receiving portion 45 (FIG. 1) having a shape that fits into the head portion of the piston 31 inside the piston 30 is formed.

As shown in FIG. 3, the outer circumference 51 of the rotating disc 50 is a ball when the rotating disc 50 is rotated in one direction (arrow).
70 is pushed outward in the radial direction of the rotating disc, and is pressed against the inner wall of the shield plug lower end portion 15 shown by the phantom line, so that when the rotating disc 50 is rotated in the opposite direction, this pressure contact is released. It has a shape with many locally eccentric portions.

The numeral 80 in FIG. 1 is a cylindrical frame for attaching the device of the present invention to the refueling machine glove 30.
The lower end 80b of the frame body, which is fixed to the lower surface of the ball holding disc 61 in the device of the present invention, is supported by the shoulder portion 32 formed on the outer periphery of the fuel exchanger glove 30. Therefore, the ball holding disc 61 does not rotate. The shoulder portion 32 is a shoulder portion (see FIG. 5A) that is conventionally formed on the glove 30 to support the lower edge of the shield plug when the glove 30 is fitted in the lower opening of the shield plug. is there.

The operation of the device of the present invention is as follows. After this device is mounted on the refueling machine grab 30 as shown in FIG. 1, the glove is raised to allow the ball 70 to reach a predetermined position within the opening 15 of the shield plug lower end 15. In the illustrated example, when the fuel exchanger grab is directly inserted into the shield plug lower end opening at the time of fuel exchange (FIG. 5), the shield plug lower end 15 opening into which the ball 33 of the ball latch mechanism on the fuel exchanger grab 30 side fits. The ball 70 of the device of the present invention is fitted into the recess groove 17 of the inner wall.

Then, when the glove piston 31 is raised, the ascending force of the piston is converted into a rotational force by the ball screw 40 and transmitted to the rotating disc 50. When the rotating disk 50 rotates in the direction of the arrow in FIG. 3, the ball 70 is pushed outward in the radial direction of the rotating disk while rotating, and presses against the inner wall of the lower end 15 of the shield plug, that is, the surface of the recess groove 17.

If you further raise the grab piston 31 at this point,
The rotating disk 50 further rotates, and the rotational force is transmitted to the shield plug 10 via the ball 70.

When the shield plug rotates, a rotational force is applied to the ball 12 of the ball latch mechanism of the shield plug. As a result, the restraint force at the fixing points 11a, 11b, 21a of the ball shown in FIG. 6B is released, so that the ball 12 is prevented by the taper effect of the pressure pipe lower extension pipe recess groove 21 as shown in FIG. 6C. It is housed in the latch body recess groove 16 and the ball latch mechanism of the shielding plug can be released.

The shape of the outer circumference 51 of the rotating disk 50 is not necessarily limited to the shape shown in FIG. 3, and for example, the outer peripheral surface of the rotating disk is tapered so as to taper upward. It can also be formed into a curved shape. As a result, the balls arranged on the outer periphery can be pushed out to the outer periphery in the radial direction of the rotating disc by raising the rotating disc while rotating.

<Effects of the Invention> Since the device of the present invention is configured as described above, the following effects can be obtained.

i) By mechanically rotating the ball of the ball latch mechanism of the shield plug through the rotation of the entire shield plug, the ball fixation can be effectively released.

ii) Since the load can be applied to the balls arranged on the outer circumference of the rotating disk not only in the vertical direction but also in the circumferential direction, the load can be efficiently transmitted.

iii) Since the drive motor, power supply, control circuit, etc. are unnecessary, the structure is simple and the reliability of the device is high.
It can be manufactured at low cost and has a high certainty of its operating function.

iv) It can be dealt with only by installing the device of the present invention without making a great change in the structure of the shield plug or the fuel exchanger grab.

v) It has no effect on the normal operation of the plant.

[Brief description of drawings]

1 is a sectional view showing an embodiment of the device of the present invention; FIG. 2 is a partially cutaway perspective view showing the structure of a ball screw used in the device of the present invention; and FIG. 3 is a rotating disk of the device of the present invention. 1 is a sectional view taken along line III-III; FIG. 4 is a sectional view showing a ball latch mechanism of a shielding plug inserted in a pressure tube lower extension pipe; FIGS. 5A and 5B are fuel. FIG. 6A, FIG. 6B and FIG. 6C are cross-sectional views for explaining the operation of the exchange; 10 ... Shielding plug, 15 ... Shielding plug lower end, 20 ... Pressure pipe lower extension pipe, 30 ... Fuel exchange grab, 31 ... Piston, 40 ...
Ball screw, 50… Rotating disk, 51… Rotating disk outer circumference, 60,61
... ball holding disc, 70 ... ball.

Claims (1)

[Claims] 1. A ball screw for converting axial up and down movement of a piston of a grab of a fuel exchange machine into rotational movement in a direction perpendicular to the axis, and a rotating disk horizontally arranged above the ball screw and rotated by a rotational force of the ball screw. And a ball holding disc having a diameter larger than that of the rotating disc, which is horizontally arranged above and below the rotating disc so as to sandwich the rotating disc, and is rotatably placed on the outer periphery of the rotating disc between the ball holding discs. A plurality of balls, the ball holding disc having a diameter capable of fitting in the lower opening of the shield plug, and the outer peripheral portion of the rotating disc being rotated by the rotation of the rotating disc in the radial direction of the rotating disc. It has a shape that allows the ball to be pushed outwards.
A device for imparting a rotational force to a shield plug, wherein the rotational force of the rotating disk is transmitted to the shield plug when the ball is pushed out and pressed against the inner wall of the lower end portion of the shield plug.