JPS5958245A - Shock absorber - Google Patents

Abstract

PURPOSE:To absorb a shock by means of elastic deformation due to characteristic of spring and plastic deformation of each pipe of small diameter by forming an absorption part through winding a metallic pipe of small diameter in a coil- like shape. CONSTITUTION:Absorption members 20a, 20b of a shock absorber are formed by winding metallic pipes 17a, 17b of small diameter in coil-like shape. Thus, shock is absorbed by means of elastic deformation due to the overall characteristic of spring of absorption members and plastic deformation of each pipe of small diameter. As occasion arises, absorption members 20a, 20b formed with metallic pipes 17a, 17b of small diameter with rigidity different from each other are provided axially in continuation and also, a cylindrical stopper part 23 preventing deformation beyond a break strain of the pipes 17a, 17b of small diameter is fitted outside.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a shock absorber, and more particularly, to a shock absorber suitable for keeping a pupil at the lower end of a control rod or a hearth in a +BVR nuclear reactor.

[Technical background of the invention and its problems] In general, in nuclear reactors, neutron absorbing materials? The nuclear fission reaction within the reactor is controlled by inserting and withdrawing the filled control rods into the reactor core.

There are various types of control rod drive mechanisms, but for example, there is one in which the control rod is suspended by a wire rope and the control rod is raised and lowered by winding and letting out the wire rope.

FIG. 1 is a schematic configuration diagram of the wire lobe type control rod drive device, in which a plurality of control rod insertion holes 3 are formed in the reactor core 2 supported on the hearth part 1 (the number of control rod insertion holes 3 is shown in the figure). A control rod guide tube 5 suspended from the guide tube support member 4 is located at the upper part π of each control rod insertion hole 3 on the same axis as one axis of each control rod insertion hole 3. are located in each.

By the way, the control rods 61-I are inserted into each control rod insertion hole 3 of the reactor core 2, and the wire lobes 8 are inserted through the seven connecting fittings.
The upper part of the wire lobe 8 is rotatably supported by bearings 9, 9, and the gear mechanism 11 is connected to the f drive motor 10.
It is wound and mounted on the drum 12 through which it is moved. Further, a position detector 13 is connected to the gear mechanism 11 to detect the position of the control rod 6 by changing the rotation angle.

Therefore, the drum 12v is rotated by the drive motor IOK to wind up or lower the wire lobe 8.
As a result, the control rod 6 is moved up and down, and the control rod 6 is positioned at an appropriate position (3) in the control rod insertion hole 3 of the reactor core 2, thereby controlling the nuclear reaction inside the reactor. .

However, in such a device π, if some unforeseen event f or j occurs, such as a breakage accident of the wire lobe 8, the control rod 6 is inserted into the control rod insertion hole 3 of the reactor core 2. The internal core may fall and collide with the hearth part IK, and the impact energy may damage the control rod 6 and the hearth part 1. Therefore, when the control rod falls, the control rod As a damage prevention measure, as shown in Fig. 1 of the conventional vehicle, the lower end of the control rod 6 is exposed to the impact energy when it falls. A shock absorber 14 is attached to absorb the shock.

The shock absorber 14 is composed of a cylindrical molded bellows, as shown in FIG. . This is because when the surrounding air inside the reactor is in high temperature He gas, etc., water,
This is based on the fact that it is impossible to use liquids such as oil.

(4) By the way, the position of the control rod when the wire lobe is severed due to an unforeseen situation is, of course, not fixed, and the fall will start from any position within the control rod's movable distance (5130 m, if you fill it). be done.

Therefore, the shock absorber 14 and the control rod 6
Even if the product falls from the highest position (for example, 5200 mm from the hearth), the impact energy should be set so that the impact force is less than the allowable load of the control rod and the hearth. The ability to absorb is necessary. Further, since the diameter of the control rod insertion hole of the shock absorber is determined in the overall design f of the nuclear reactor, there are restrictions on dimensions such as the maximum outer diameter and length.

Therefore, the conventional molded bellows type shock absorber is designed to keep the impact load on the control rod and the hearth below the allowable value W even if the control rod falls from the highest position as described above. The required plate thickness must be two to three times greater than the maximum plate thickness of molded bellows tubes having the same outside diameter that are currently manufactured.

However, in general, formed bellows pipes are made by corrugated drawing on thin-walled pipes. However, it is extremely difficult to form pipes that are thicker than the outer diameter, such as conventional shock absorbers, and requires the development of new manufacturing equipment and technology, resulting in extremely high production costs. There are disadvantages such as high cost.

[Purpose of the invention]

In view of these points, it is an object of the present invention to provide a shock absorber which has the same impact energy absorption capacity as the conventional one and which can be easily and inexpensively manufactured using existing technical capabilities.

[Summary of the Invention] In the present invention, a small diameter pipe made of metal is wound in a coil shape to form a buffer part 4, and impact energy is generated by plastic deformation of each small diameter pipe. It is characterized by being designed to absorb.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 4 to 7.

Figure 4 shows control rod insertion holes 3 provided in the core 2 of a nuclear reactor.
FIG. 2 is a longitudinal side view of a shock absorber 16 according to the present invention mounted on the lower end of a control rod 6 which is disposed so as to be able to rise and fall within the reactor; It consists of 17 small-diameter pipes made of metal (e.g., Hastelloy-XR) that can withstand K (approx. is fixed, and an upper end plate 19 is fixed to the upper end, and the upper end plate 19 is attached to the lower end of the control rod 6. In addition, the outer diameter of the small diameter pipe 17, the thickness of 5 turns, and the number of turns of the small diameter pipe 17 should be such that it has the ability to absorb impact energy so that the impact load is below the allowable impact load of the control rod and the hearth even if the case falls from a certain position. The dimension with the control rod 6 has been determined, but the control rod 6? When the control rod 6 falls due to cutting of a hanging wire lobe, etc., it will be elastically deformed due to the spring characteristics of the small diameter pipe 17 wound in a coiled shape after falling from a relatively low position. The impact energy from the fall will be absorbed.

On the other hand, when the control rod 6 falls from a high position, the lower end plate 18 of the shock absorber 16 comes into contact with the hearth part 1 (7), and then due to the falling impact QK of the control rod 6, the small diameter When the pipes 17 are brought into close contact with each other, the pipe itself becomes a crushed shape and line as shown in Fig. 5, and the impact energy is absorbed by the overall plastic deformation of the pipe, and the impact energy is transferred to the control rod and the hearth. The impact load must be kept within the allowable impact load of 1M.

FIGS. 6 and 7 are views showing other embodiments of the present invention ψ11, in which , T:rl ii part is the buffer member of army 1"a
and a second loose member 20b171'.

That is, when the lower end plate 18 and the annular intermediate mounting board 21 are compressed and deformed under a low-altitude atmosphere such as when the output of the furnace is stopped, the buffering capacity is the highest. A small-diameter metal vibrator 17a with a relatively thin plate and having such rigidity that it can be plastically deformed by exerting the force
Hand-attached. The distance f between the intermediate mounting board 21 and the upper end plate 19 is - the first buffer member 20 a
The wall thickness is one table thicker than that of the small-diameter pipe 17a, and it is a high l black (8) such as when operating the furnace output. , a small-diameter vibrator 17b%' with a plate thickness that has the rigidity to exhibit the maximum buffering capacity and plastic deformation, and a second shock absorbing member 20b wound in a coiled form on the same axis as the first shock absorbing member 20a. It is inserted into the Ota,
The lower end plate 181 is fitted into the first buffer member 20a, and a cylindrical stopper 22 of an appropriate height is attached to prevent the buffer member 20a from being damaged or deformed to a strain of 8 or more. ,
Additionally, a cylindrical stopper is attached to the upper half of the upper end plate I9f of the eave and the buffer member 20b to prevent it from deforming beyond the breaking strain of the buffer member 20b of tA2. .

Therefore, the first and second buffer members 20 a are operated under a low-temperature variable atmosphere such as when exchanging fuel.

If the control rod 6 falls in a state where the small diameter pipes 17a and 17b that make up the 2Ob structure have a high yield stress and high energy absorption capacity, or even if the control rod 6 is in a high temperature 4 environment, the control rod 6
If the control rod falls from a low position and the falling energy is small, then the small diameter pipe 17a (9) of the first buffer member 20a with low rigidity is caused by the fall of the control rod.
^Only the pressure is 7.
The control rod is subjected to plastic deformation, and the energy of the control rod falling is effectively absorbed.

On the other hand, in the high temperature atmosphere 1 during output operation, the first and second >a if+ members: 5J a, 20b
? The yield stress of the small-diameter pipes 17a and 17b decreases, resulting in a low energy absorption capacity. If the rod is connected to each F L f intestine, + or low crystallinity - if the control rod falls from a high position,
Figure 71 shows the supporting member of the reinforced southern part of the pipe 1) a) A yields and compresses σ and the curved shape 4, furthermore f the second buffer member with high rigidity The small diameter pipe 17b of 20h is also deformed, and the energy of the fall of the control is absorbed, and the impact of the 4tl-l nil rod and the hearth is
It's important to keep the cargo to within 100 lbs of weight.

In addition, when the tension member 20a and the force C are deformed to the design value 1, the stopper 22. If the metal part comes into contact with the intermediate mounting board 21, further deformation will be prevented, and both parts will be damaged and their fragments will be scattered, or the broken part will dig into the core wall and cause damage to the core.
This prevents problems such as the loss of the festival (10).

In this way, according to this embodiment, even if the yield stress of the buffer member changes due to a change in the furnace temperature, the optimal buffer capacity can be exerted by plastic deformation of one or both of the members having different rigidities. It is extremely effective when applied to equipment such as control rods that are subject to temperature changes, and is not affected by the falling height of the control rod. ability? and provides a stable buffering effect. It goes without saying that three or more buffer members with different buffer capacities may be installed in series, and the number of buffer members, the diameter of the small pipe, the wall thickness, and the shape of the coil may be adjusted according to the expected accident event. Configurations such as the number of turns when winding, shape, arrangement, etc. can be changed as appropriate.

Furthermore, in both of the above embodiments, the shock absorber'
l? Although the control rod is shown attached to the lowermost end of the control rod, it may be installed upright on the hearth of the control rod insertion hole. Furthermore, it can also be applied to equipment other than nuclear reactors.〇(11) [Effects of the Invention] The above-described method f1 of the present invention constitutes a buffer section by winding a small diameter metal pipe in a coil shape. However, since the impact energy is absorbed by the plastic deformation of each small diameter pipe, the impact energy can be sufficiently absorbed even in cases where the maximum outer diameter and height are limited, such as in shock absorbers for control salaries. you can get
Moreover, it can be easily manufactured using the technology and equipment currently in common use, and the cost can be significantly reduced compared to conventional shock absorbers. In addition, when multiple shock absorbing members with different shock absorbing capacities are connected, it is possible to reduce the fall energy due to a single difference in the falling position, and the physical properties of the shock absorbing members may change due to changes in the environmental wetness. of buffering capacity due to! Even when the shock absorber is in effect, it is possible to always obtain a stable shock absorbing effect under a wide range of conditions due to the interaction of each shock absorbing member.

[Brief explanation of the drawing]

(12) Figure 1 is a schematic configuration diagram of the control rod drive mechanism of the nuclear reactor;
Figure 2 shows wIa of a conventional shock absorber for control rods.
1u6 side view, FIG. 3 is an explanatory diagram of the same operation as above, FIG. 4 is a longitudinal cross-sectional side view of the shock absorber of the present invention, FIG. 5 is an explanatory diagram of the same operating state, and FIG. 6 is an illustration of another embodiment of the present invention. 7 is an explanatory view of the same operation as above. 2... Core, 3... Control rod insertion hole, 6... Control rod, 16... Shock absorber, 1.7.17a,
17 b... Small diameter pipe, 18... Lower end plate, 1
9... Upper end plate, 20a... First (7'l buffer member, 20b... Second buffer member. Representative Kiyoshi Inomata (13)
-26: Act 1 Figure l Tame 2 Figure Tame 3 Figure i Figure Mo 5 Figure Yan, 6 Figure Yu 7 Figure

Claims (1)

[Scope of Claims] 1. Shock absorber 2, characterized in that a shock absorber is constructed by winding small diameter metal pipes into a coil shape, and absorbs impact energy through plastic deformation of each small diameter pipe. A buffer section is constructed by axially arranging a plurality of small-diameter vibrators made of metal, each having a different rigidity, and a plurality of heating member members each having a different buffering capacity, each of which is wound in a coil shape and arranged in series. The shock absorber according to claim 1, characterized in that: 3. A cylindrical stopper part is fitted on the outer periphery of the buffer part to prevent deformation exceeding the breaking strain of the small-diameter pipe coil. - The shock absorber port 4 according to claim 1 or 2 is installed at the lower end of a control rod in a nuclear reactor. The shock absorber according to any of item 3. 5. Is it installed upright on the hearth of the reactor? Features. A shock absorber according to any one of claims 1 to 3.