JP2832203B2 - Hydraulic shock absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) Spent nuclear fuel in a nuclear power plant is processed by being housed in a transport container called a cask. Loading of the spent nuclear fuel into the cask is performed in the water in the pool filled with water. TECHNICAL FIELD The present invention relates to an impact buffering device for relaxing an impact on the bottom of a pool and preventing damage when the cask is dropped or erroneously dropped or suspended in a pool.

(Prior Art) Conventionally, as a shock absorber installed in a pool in a nuclear power plant, a hydraulic shock absorber using water in the pool as a working fluid is known. This hydraulic shock absorber is composed of an upper plate that is directly under the water in the pool and receives an impact load due to the drop of the cask; a lower plate that is on the bottom of the pool and supports the impact load; When the upper plate and the lower plate approach each other, the piston in the cylinder moves and contracts, and a plurality of cylinder devices that discharge water in the hydraulic chamber through the orifice into the pool, and each of these cylinders And a restoring spring which is inserted around the outer periphery of the device and biases the upper plate upward so as to constantly maintain the upper plate at a predetermined height position.

In this hydraulic shock absorber, the cylinder device and the restoring spring are united, and such a cylinder device is provided between the upper plate and the lower plate and stands almost equally spaced. If the cask falls on the upper plate for some reason, the restoring spring is compressed and the upper plate is lowered, and the cylinder device contracts, the piston moves in the cylinder, and the water in the hydraulic chamber is discharged through the orifice. Release into the pool via At this time, the impact is damped by the flow resistance of the water.

However, the cask is normally suspended slowly on the shock absorber. At this time, the cylinder device contracts with the restoring spring to support the cask at the stroke end. When the loading of the spent nuclear fuel into the cask in the pool is completed, the cask is lifted again and transported to a predetermined location. When the cask is lifted from above the upper plate, the upper plate is pushed up by the restoring spring, and the cylinder device is also extended and restored. The shock absorber repeats such an operation.

(Problems to be Solved by the Invention) In the conventional shock absorber described above, when the cask is displaced from the center of the shock absorber in the process of contracting the cylinder device by the weight of the cask, the cask tilts together with the upper plate. When the upper plate is inclined, the sliding portion of the cylinder device sticks, and there is a problem that the expansion and contraction operation cannot be performed smoothly.

Accordingly, an object of the present invention is to provide a hydraulic shock absorber capable of minimizing the inclination of the upper plate and preventing the stick of the sliding portion of the cylinder device.

(Means for Solving the Problems) In the present invention, in order to solve the above problems, the cylinder device 3 and the restoring spring 4 are separated, and the cylinder device 3 is
The hydraulic spring was arranged so as to be concentrated around the center where the cask C was placed, and the restoring spring 4 was arranged outside the cylinder device 3 so as to surround it.

(Operation) In the shock absorbing device of the present invention, when the cask C falls on the upper plate 1 for some reason, the restoring spring 4 is compressed, the upper plate 1 descends, and the cylinder device 3 contracts, The pistons (cylinders 7, 8) descend in the cylinder 1 and discharge the water in the hydraulic chambers 9, 10 into the pool through the orifices 7a, 8a. The impact is damped by the flow resistance of the water at this time. Further, for example, when the cask C is suspended at a position deviated from the center of the upper plate 1 and the upper plate 1 is subjected to a tilting force together with the cask C, the restoring spring 4 concentrated on the outer portion of the upper plate 1 is moved to this position. Oppose. Therefore, the inclination of the upper plate 1 is prevented, and the stick of the cylinder device 3 is prevented. Since the restoring spring 4 is located at a position away from the center of the upper plate 1, the restoring spring 4 exerts a counterforce in a direction to correct the inclination of the upper plate 1 with a large moment. Further, since the cylinder device 3 is centrally arranged at the center, it is possible to avoid the influence of the slight inclination of the upper plate 1.

(Embodiment) An embodiment of the present invention will be described with reference to FIGS. 1 is a front view of the shock absorbing device, FIG. 2 is a plan view of the shock absorbing device, and FIG. 3 is a vertical front view taken along the line III-III in FIG. 2, showing the left half in a contracted state.

The shock absorbing device 30 of this embodiment includes an upper plate 1 which is underwater in a pool and directly receives an impact load due to a drop of a cask C, and a lower plate 2 which is on a bottom B of the pool and supports the impact load. And a cylinder device 3 provided between the upper plate 1 and the lower plate 2, and a restoring spring 4 also provided between the upper plate 1 and the lower plate 2.

The guide column 5 erected from the four corners of the lower plate 2
The upper plate 1 can freely move up and down with respect to the lower plate 2.

The four cylinder devices 3 are provided concentrated in the center. That is, as shown in FIG.
A first cylinder 6 fixed to the lower plate 2 so as to close the lower end, a second cylinder 7 slidably inserted into the first cylinder 6 up and down, and a slide in the second cylinder 7 And a third cylinder 8 freely inserted. The second cylinder 7 operates as a piston with respect to the first cylinder 6, and the third cylinder 8 operates as a piston with respect to the second cylinder 7. Vertical orifice grooves 7a, 8a are formed on the side surfaces of the second cylinder 7 and the third cylinder 8, respectively, and the hydraulic chambers 9, 10 formed in each cylinder communicate with the outside. The lid 8b at the upper end of the third cylinder 8 is suspended from the upper plate 1 by suspension bolts 11. That is, the suspension bolt 11 penetrates loosely through the hole 1b formed in the center of the suspension plate 1a fixed to the upper plate 1, and is prevented from coming off by the stopper plate 11a. Thus, when the upper plate 1 and the lower plate 2 approach each other under an impact load, the cylinder device 3
It contracts while discharging the water in 9, 10 through the orifice grooves 7a, 8a into the pool.

The restoring springs 4 are arranged in a rectangle of five each so as to surround four surroundings of the four cylinder devices, and are concentratedly arranged outside.
The restoring spring 4 is formed by vertically combining two different diameters 4a and 4b, and is expanded and contracted in the axial direction by three guide cylinders 12, 13, and 14 which are telescopically combined in a telescopic manner. Guided. And the restoration spring 4
Between the upper plate 1 and the lower plate 2, the upper plate 1 is urged upward so as to always keep the upper plate 1 at a predetermined height position.

The shock absorber 30 of this embodiment is installed at the bottom B of a cooling water pool in a nuclear power plant. A cask C is placed on the shock absorber 30 and the cask C is stored with spent nuclear fuel. The cask C is suspended on the shock absorber 30 and lifted after the spent nuclear fuel is loaded. If the cask C falls on the upper plate 1 for any reason during the operation of lifting and lifting, the restoring spring 4 is activated. While being compressed, the upper plate 1 descends, the cylinder device 3 contracts, and the second cylinder 7 descends in the first cylinder 6, and the third cylinder 8 descends in the second cylinder 7, and the hydraulic pressure chamber 9, Ten
The water inside is discharged into the pool through the orifices 7a and 8a. The impact is damped by the flow resistance of the water at this time. Further, when the cask C is suspended at a position shifted from the center of the upper plate 1 and receives a force for tilting the upper plate 1 together with the cask C,
A restoring spring 4 concentrated on the outer side of the upper plate 1 opposes this. Therefore, the inclination of the upper plate 1 is prevented, and the stick of the cylinder device 3 is prevented. Restoring spring 4
Is located at a position away from the center of the upper plate 1 and exerts a counterforce in a direction to correct the inclination of the upper plate 1 with a large moment. Further, since the cylinder device 3 is centrally arranged at the center, it is possible to avoid the influence of the slight inclination of the upper plate 1. Even if the upper plate 1 is slightly inclined, since the suspension bolts 11 of the cylinder device 3 move relatively in the holes 1b of the suspension plate 1a, the axis of the cylinder device 3 does not shift.

(Effect of the Invention) As described above, in the present invention, the cylinder device 3 and the restoring spring 4 are separated, and the cylinder device 3 is centrally arranged near the center where the cask C is placed. Since the hydraulic shock absorber is arranged outside the device 3 so as to surround the device 3, the cask C is displaced from the center of the shock absorber 10 in the process of the cylinder device 3 being contracted by the weight of the cask C, and the upper plate 1 Even if a force for inclining the upper plate 1 is given, the restoring spring 4 arranged in the periphery opposes this, so that the upper plate 1 is hard to be inclined. Accordingly, the axial center of the cylinder device is not displaced, and the stick phenomenon of the sliding portion is prevented from being generated, so that the effect of smoothly performing the expansion and contraction operation is achieved.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a front view of an impact buffer, FIG. 2 is a plan view of the impact buffer, FIG.
The figure is a vertical sectional front view taken along the line III-III in FIG. 2, and the left half is shown in a contracted state. 1 Upper plate 2 Lower plate 3 Cylinder device 4 Restoring spring 6 Cylinder 7, 8 Cylinder (piston) 7a, 8a Orifice 9, 10 Hydraulic chamber B Pool Bottom C …… Cask

Claims (1)

(57) [Claims] 1. An upper plate directly receiving an impact load due to a drop of the cask in water in a pool in which a cask for storing spent nuclear fuel is submerged, and the impact load on a bottom of the pool. When the upper plate and the lower plate approach each other under the impact load, the piston in the cylinder moves and contracts, and the water in the internal hydraulic chamber is pooled through the orifice. A plurality of cylinder devices for discharging the inner plate, and between the upper plate and the lower plate, a plurality of restoring springs for urging the upper plate upward in order to always hold the upper plate at a predetermined height position. In the shock absorbing device, the plurality of cylinder devices are centrally disposed near a center where the cask is placed, and the plurality of restoring springs are disposed outside the plurality of cylinder devices so as to surround the plurality of cylinder devices. Hydraulic shock absorbing device according to claim.