JPS6345559B2 - - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a fuel exchange device for a nuclear reactor such as a fast breeder reactor, which is capable of absorbing thermal expansion that affects the opening and closing of a gripper-equipped pandagraph that grips fuel.

Technical Background of the Invention A pandagraph type fuel exchange device is used in a nuclear reactor such as a fast breeder reactor, an example of which is shown in FIGS. 1 and 2.

First, a rotary plug 1 is rotatably provided in the upper part of the reactor vessel, and a cylindrical rotary housing 2 that is supported so as to be able to rotate in any direction and move vertically is mounted through the plug. . The rotating housing 2 has a lift housing 3 inserted therethrough as necessary, and has the function of rotating the fuel exchange device and holding down the fuel around the fuel to be exchanged. The lift housing 3 has a cylindrical shape, and is equipped with a pantograph 4 consisting of a link mechanism at its lower end, and a gripper mechanism 5 for gripping and releasing fuel 19 at the tip of its arm. Further, at the upper end, a drive unit 6 is connected to the drive unit 6, which incorporates the opening/closing mechanisms of the panda graph 4 and the gripper mechanism 5, a fuel position sensing mechanism, etc., and is rotatably supported by the cover 7 via a bearing 9. . The cover 7 is guided on the inner surface of the cask casing 8 via guide rollers 10 in a non-rotatable but movable manner and is suspended from a wire rope of a hoisting device 11 above, whereby the lifting and lowering of the cover 7 and the lifting housing 3 are controlled.

The rotary housing 2 is mounted on a guide sleeve 12 fitted into the through hole 1a of the rotary plug 1, and a sleeve-shaped body 14 is installed above through a bearing 13. Two turning mechanisms 15 and a hold-down mechanism 16 are provided. Further, there is a door valve 17 at the upper end of the body 14, and a cask casing 8
It can be connected to the door valve 18 at the lower end.

When exchanging fuel, the cask casing 8 housing the elevating housing 3 is brought onto the rotating housing, the door valves 17 and 18 are connected, and the inside of the cask casing 8 is replaced with an inert gas such as Ar gas. Thereafter, by lowering and inserting the elevating housing 3 into the rotary housing 2, the elevating housing 3 is coupled to rotate integrally with the rotary housing 2. The lower end of the lifting housing 3 is introduced into the furnace and the pantograph 4 is opened. Then, the gripper mechanism 5 is adjusted to the required fuel 19 position by combining the rotation angles of the rotary plug 1 and the rotary housing 2, grips this fuel 19, and holds the hoisting device 1.
It is pulled out from the reactor core 20 by hoisting. Next, after replacing the fuel with new fuel at a predetermined location, the fuel is returned to the original position, new fuel is inserted, and the claws of the gripper mechanism 5 are opened and released.
After that, fold pantograph 4 in the opposite direction as above,
The lifting housing 3 is pulled up and housed in the cask casing 8, and the door valves 17 and 18 are separated.
Transport it to a designated location and perform maintenance and inspection.

The structural concept of the above fuel exchange device using the pantograph mechanism is shown in FIG.

A folding link 42 is pivotally attached to the middle part of the arm 41 of the pantograph 4, and is connected to an opening/closing rod 44 via an elevator 43 guided by a groove 3a provided in the elevator housing 3. The drive unit 6 includes a pantograph opening/closing mechanism 53, and a bevel gear 49 is mounted via a torque detector 47 and a gear box 48 provided on the output shaft of a reducer 46 directly connected to a drive motor 45. The bevel gear 49 meshes with a bevel gear 51 mounted on a ball screw 50, and the rotation of the ball screw 50 is converted into linear motion by a ball nut 52. The upper end of the opening/closing rod 44 is connected to this ball nut 52. Reference numeral 60 indicates a position detector for detecting the open/close position.

Problems with the Background Art In the opening/closing control of the pantograph of the conventionally used fuel exchange device as described above, there is no particular problem in both position cutting and load cutting when the pantograph is opened. The following problems arise with load cutting.

In other words, in general, in the case of a fast breeder reactor, the sodium temperature inside the reactor during fuel exchange is approximately 200°C, and if position cutting is performed with the same stroke as at room temperature, the folding link 42, arm 41, and opening/closing rod 44 will thermally expand. Because of this, the folding becomes insufficient and it becomes difficult to pass through the rotary housing 2 and pull it out of the furnace. On the other hand, in the case of load cutting, if the arm 41 is completely folded and the load is detected by colliding with a part of the lifting housing 3, the folding itself is completely carried out regardless of the temperature. If the thermally expanded arm 41 etc. cool down and contract after being stored in the cask casing 8, a large thermal contraction force will be generated in the opening/closing rod 44 and the pantograph opening/closing mechanism 53, which may lead to damage and accidents. . One possible way to prevent this is to open the pantograph 4 slightly after it is stored in the cask casing 8, but in reality, various interlock circuits are built into the control circuit, and handling operations are difficult. It is not perfect as it is well thought that it will become complicated and people will forget to operate it.

Purpose of the Invention The present invention was devised in view of the above-mentioned problems. Even if thermal contraction occurs due to a drop in temperature, the shrinkage is absorbed by the spring, and large stress is not applied to the opening/closing rod or pantograph opening/closing mechanism. To provide a fuel exchange device for a fast breeder nuclear reactor that eliminates

SUMMARY OF THE INVENTION In order to achieve the above object, in the present invention, a part of the opening/closing rod is separated vertically and connected through a telescopic part. The retractable part is equipped with a spring that is always reduced to the minimum length, and its retracting force is set to slightly exceed the weight of the pantograph. That is, the opening/closing rod acts as a single rod that does not extend when simply opening/closing the pantograph. After the pantograph is completely stored and the load is removed, when heat shrinks in each part due to cooling, the elastic part expands and absorbs the shrinkage. Therefore, the opening/closing rod and a series of devices to which it is connected, such as the pantograph opening/closing mechanism, are only subjected to stress equal to the slight extension of the spring, and stress that would forcefully extend the opening/closing rod cannot be prevented. can.

On the other hand, the load of pulling out and carrying the fuel gripped by the gripper mechanism is applied to the opening/closing rod, and the spring force of the telescopic part cannot withstand this load. A stopper is provided on the elevating housing so as to receive the lower end of the elevating housing. Loads such as the weight of fuel are received by the stopper and do not act on the expandable portion. The spring storage force of the telescopic part can be set to the minimum,
Stress during heat shrinkage can also be minimized.
The stopper is made vertically adjustable so that the optimal pantograph opening position can be selected.

Furthermore, a disc spring is interposed between the telescopic lower end and the stopper or between the telescopic part and the end of the opening/closing rod, so that when the telescopic part descends together with the opening/closing rod and comes into contact with the stopper, the entire load is received by the stopper. Alleviates the impact of

Embodiment of the Invention An embodiment of the invention will be described below with reference to the drawings.
Figure 3 shows the main parts. The configuration, mechanism, and operation of other parts for fuel exchange are the same as those shown in FIGS. 1 and 2, so the same reference numerals are given and explanations thereof will be omitted.

Separate the lower part of the opening/closing rod 44 and remove the lower rod 4.
4a, an enlarged portion 44b is provided at the separated end, and a limiting plate 54 is attached slightly above. The lower end of a spring case 56 is connected to the upper end of the lower rod 44a. This spring case 56 is open at the top, and has an inner flange portion 56a at the open end.
will be provided. The lower end of the opening/closing rod 44 is inserted into the spring case 56, and the telescopic spring 55 is elastically loaded between the inner flange portion 56a and the enlarged portion 44b. Due to the elasticity of the telescopic spring 55, the relative position between the opening/closing rod 44 and the lower rod 44a is reduced, and the upper end of the spring case 56 and the limiting plate 54 are
touch and contract to the minimum. Spring 5 at this time
5 is set to a force that exceeds the weight of pantograph 4. In this way, the opening/closing rod 44 and the lower rod 4
4a are integrally coupled.

When the panda graph 4 is opened or closed, this spring case 56 descends together with the opening/closing rods 44, 44a.
A stopper 58 is attached to the elevating housing 3 so as to come into contact with the lower end of the spring case 56 when the pantograph 4 is in the fully open position. A disc spring 57 is interposed on the upper surface of the stopper 58. Further, the stopper 58 is mounted so that its vertical position can be adjusted using a screw 59 and a lock nut 59a.

The system is constructed as described above, and its operation will be described next.

When the pantograph is opened, the drive motor 45 is rotated to lower the opening/closing rod 44, and the lower part of the spring case 56 comes into contact with the stopper 58, and the opening/closing mechanism 5
The load is cut off using the torque detector 47 of No. 3. In this case, the disc spring 57 acts as a buffer and the load can be cut off without any shocking increase in load. When exchanging fuel in this state, a load of several tons is applied to the lower rod 44a when the fuel is extracted, but the lower end of the spring case 56 is supported on the stopper 58 and bears this load, so that the spring 55 is not affected. do not have.

Conversely, when fuel is inserted, a force is applied to the lower rod 44a from below, but the upper end of the spring case 56 comes into contact with the restriction plate 54 to bear the load. Therefore, the telescopic spring 55 is used for fuel insertion,
Since there is no need to bear the pulling force and it is sufficient to store enough strength to withstand the weight of the pantograph, the spring case can be constructed with a relatively compact size.

Next, when folding the pantograph, the opening/closing rod 4 is rotated by the reverse rotation of the drive motor 45.
4 and 44a, and the pantograph 4 is folded and completely accommodated in the elevating housing 3 and comes into contact with a part of it. Since the load increases here, this is detected by the torque detector 47 of the opening/closing mechanism 53, and the load is cut off. In this case as well, the spring 55 provides a buffer,
There is no shocking load increase. Further, in this case, if the position detector 60 is used for control, the reliability will be improved.

After folding, the elevating housing 3 is stored in the cask casing 8, and even if the arm 41, folding link 42, opening/closing rod 44, etc. are cooled and contracted there, all of the contraction is compressed by the elastic spring 55. Therefore, excessive heat shrinkage force is not applied to the pantograph opening/closing mechanism 53, opening/closing rod 44, etc.

Effects of the Invention As described above, the nuclear reactor refueling device according to the present invention has a telescopic section that is normally compressed with a stored force greater than the force required to open and close the pantograph, in the middle of the opening/closing rod that opens and closes the pantograph. This device is equipped with a stopper that catches the lower end of the telescopic section when the pantograph is fully open, allowing it to cope with heat contraction and fuel withdrawal/insertion without increasing the spring force of the telescopic section. The pantograph can be completely stored in the elevating housing by cutting, and there is no need to open the pantograph completely after storing it in the cask casing, making the device easy to handle, highly reliable, and compact. can.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view showing the conventional structure of a fuel exchange device for a fast breeder reactor, Fig. 2 is a conceptual diagram of the configuration of a pantograph opening/closing mechanism, and Fig. 3 is a schematic diagram showing an embodiment of the fuel exchange device of the present invention. FIG. 1... Rotating plug, 2... Rotating housing, 3
... Lifting housing, 4... Pantograph, 5...
... Gripper mechanism, 6... Drive unit, 8... Cask casing, 11... Hoisting device, 17, 18...
... Door valve, 41 ... Arm, 42 ... Folding link, 43 ... Elevator, 44 ... Opening/closing rod,
47...torque detector, 53...pantograph opening/closing mechanism, 54...limiting plate, 55...spring,
56...Spring case, 57...Disc spring, 5
8...Stotsupa.

Claims (1)

[Scope of Claims] 1. A rotary housing rotatably mounted on a rotary plug provided at the top of the reactor vessel, an elevating housing that moves up and down within the housing, a pantograph with a gripper installed at the bottom of the elevating housing, and an elevating housing. A part of the opening/closing rod that connects the pantograph and the pantograph opening/closing mechanism is provided with an extendable part that is contracted by a predetermined spring force. A refueling device for a nuclear reactor, characterized in that an adjustable stopper is installed in the elevating housing and is interposed therein and is adapted to catch the lower end of an extendable part that descends together with an opening/closing rod when a pantograph is opened. 2. The fuel exchange device for a fast breeder nuclear reactor according to claim 1, characterized in that a disc spring for cushioning is interposed between the extendable part and the stopper or between the opening/closing rod and the extendable part.