JPS6226718B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel exchange device for loading new fuel assemblies into a nuclear reactor using liquid metal as a coolant and for taking spent fuel assemblies out of the reactor.

As shown in Figure 1, a single-rotation plug fixed arm type liquid metal cooled fast breeder reactor has a reactor core 2 loaded with a large number of fuel assemblies in a reactor vessel 1, and a coolant 3 stored therein. A shield plug 4 is attached to the top of the furnace vessel 1 and serves as a lid. The stiffening plug 4 consists of a fixed plug 5 which is always fixed and a rotating plug 6 which is eccentrically mounted and can rotate.
On the rotating plug 6, a core upper mechanism 7 for holding a control rod drive mechanism and a pantograph arm type fuel exchange device 8 for exchanging fuel assemblies are eccentrically mounted. Liquid metal coolant 3 enters through the inlet nozzle 9 and passes through the core 1 to the outlet nozzle 1
It is starting to flow from 0.

The furnace vessel 1 is protected by a guard cell 1a, and the nozzles 9 and 10 are protected by guard pipes 9a and 10a.

Further, the core 2 is supported by a support mechanism 2a. Although not shown in the drawings, the support mechanism 2a is provided with a guide pipe into which the entrance nozzle of the fuel assembly is inserted and fixed, and the coolant flows through the guide pipe.

A single rotation plug fixed arm type fuel exchange device is constructed as shown in FIG. That is, the fuel exchange device main body 11 is taken out of the furnace vessel during power operation, and is inserted into the furnace during fuel exchange and attached to the rotating housing 12 that is always installed on the rotating plug 6.

Gripper 13 that grabs and releases fuel
is folded after being inserted into the furnace, and opened via the pantograph arm 15 by lowering the arm 14.
It is attached to a gripper guide tube 17 which is attached from the rotating housing 12 via a fixed arm 16.

Further, rotational force is transmitted to the rotating housing from the swing drive device 18 through the bevel gear 19, and the rotating housing rotates. The rotary housing 12 is rotatably supported by a ball bearing 20 . This rotation of the rotating housing causes the fuel exchange device main body 11 mounted inside to rotate. Therefore, during fuel exchange, the tip 21 of the gripper 13 can be moved to any address by a combination of the rotation of the rotary plug 6 and the rotation of the rotary housing 12, so that any core fuel can be handled.

FIG. 3 is a schematic cross-sectional view showing the operating range of the refueling device within the reactor vessel 1.

As the rotary plug 6 rotates within the reactor vessel 1, the locus of the rotation center O of the refueling device rotary housing 12 becomes as shown by a small circle A indicated by a two-dot chain line. In fact, since the rotary housing 12 can rotate at any position A , the range reached by the gripper guide cylinder 17 at the tip of the fuel exchange device 12 is as shown by the great circle B indicated by the two-dot chain line. Therefore, in the area indicated by hatching C , it is conceivable that the gripper guide tube 17 and the furnace vessel 3 will interfere, leading to a major accident.

Conventionally, interference prevention in this type of fuel exchange device has been done by detecting the rotation position signal of the rotary plug 6 and the rotation position signal of the fuel exchange device 8 with a rotation angle detector, or by using a certain predetermined mode. This was done using a device that had a circuit built in such a way that it would only work in the However, all such devices indirectly control the rotation signal of the drive device, so if the rotation signal becomes abnormal due to noise or other influences, the actual position of the fuel exchange device in the furnace and the rotation It is conceivable that the position signal may be different from the actual position of the fuel exchanger gripper guide cylinder, and since no other means of detection has been considered, there is a risk that the actual position of the gripper guide tube of the fuel exchanger may become unknown.

The present invention has been made to solve the above problems, and its purpose is to attach an ultrasonic transmitter/receiver to the gripper at the tip of a pantograph arm rotating inside a nuclear reactor, and to generate ultrasonic waves in the direction of rotation of the gripper. To provide a fuel exchange device which can directly prevent interference between a gripper and an obstacle by oscillating a sound wave, measuring time by receiving the reflected wave, and constantly detecting the distance to the wall of a reactor vessel. There is a particular thing.

That is, the present invention provides a pantograph arm type fuel exchange device that grips or releases a large number of fuel assemblies loaded in a core part of a nuclear reactor vessel and exchanges the fuel assemblies. An ultrasonic generator/receiver is installed on the side surface of the outer cylinder of the gripper to emit ultrasonic waves in the rotating direction of the gripper and to receive the reflected waves, and a circuit is installed to measure the ultrasonic emission/reception time. This is a fuel exchange device characterized by:

Hereinafter, one embodiment of the apparatus according to the present invention will be described with reference to FIGS. 4 to 7.

FIG. 4 shows the entire structure of the fuel exchange device according to the present invention.

At least one ultrasonic transmitter 41 is attached to the side surface of the gripper 13 of the fuel exchange device 8.

Signals from the ultrasonic generator/receiver pass through the gripper 13 into the fuel exchanger main body 11 via an MI cable 42 and are connected to an external signal processing device 43 and display device 44. At this time, the MI cable 42 is spirally routed along the folding arm 14 and the folding operation shaft 45.
The pantograph arm 15 can be opened and closed without any problem.

FIG. 5 is an enlarged cross-sectional view showing how the ultrasonic wave generator/receiver is attached within the gripper, surrounded by the two-dot chain line D in FIG. 4.

Ultrasonic generator/receivers 41 are attached to both sides of the gripper outer cylinder 51 in a direction perpendicular to the pantograph arm 15.

The ultrasonic wave emitter/receiver 41 is attached so as not to protrude from the gripper outer cylinder 51 in order to protect the acoustic wave generating surface.

Further, the gripper claw 52 is opened and closed about the pin 56 as the claw opening/closing rod 53 is moved up and down by the vertical movement of the claw opening/closing arm 55. Therefore, the ultrasonic wave generator/receiver is installed at a position that does not interfere with opening and closing of the gripper.

In addition, a window 54 is opened in a portion of the gripper guide tube 17, which becomes a path for ultrasonic waves when the gripper rotates, so as not to interfere with transmission and reception.

FIG. 6 is an enlarged sectional view showing the attached state of the ultrasonic transmitter/receiver surrounded by the two-dot chain line E in FIG.

Ultrasonic transmitter/receiver/transmitter mounting base 6 on the gripper outer cylinder 51
1, and the ultrasonic transmitter/receiver housing 62 is fixed to this mounting base 61 with bolts.

The ultrasonic transmitter/receiver is covered on the outside by a housing 62 and a case 64 made of a material that is compatible with liquid metal such as stainless steel, and the vibrations from the transducer 65 that transmits and receives ultrasonic waves are The MI cable 4 is converted into an electrical signal through the electrode 66 and the signal line 67.
2 to a signal processing device outside the reactor.

The case 64 and the MI cable 42 are sealed by welding. Therefore, there is no problem in using an ultrasonic transmitter/receiver in liquid metal.

In addition, 68 is a spring interposed between the terminal 69 and the electrode 66 and the electrode 66 and the vibrator 65.
and are pressed closely together.

Next, the effects of the above fuel exchange device will be explained.
As shown in FIG. 7, the fuel exchange device configured in this manner has an ultrasonic wave generator/receiver 41 attached to the pantograph arm 15 in a direction perpendicular to the pantograph arm. ), ultrasonic waves are always oscillated. The ultrasonic waves thus oscillated hit obstacles such as the walls of the reactor vessel 1 and are reflected. The reflected wave is also received by an ultrasonic transmitter/receiver, and by measuring the time from transmission to reception, the distance from the gripper outer cylinder 51 to an obstacle such as the wall of the reactor vessel 1 can be accurately determined. I can do it. Therefore, by setting a limit value based on the time from transmission to reception, it is possible to always stop at a constant distance from obstacles, and interference can be prevented.

Further, the present invention has the effect that interference can be prevented by always maintaining a constant distance, regardless of the operation of the fuel exchange device and the situation of obstacles in the reactor. Furthermore, it is also an effective means to install a reflector on the wall of the reactor vessel in order to increase the signal level of the received waves.

As explained above, unlike conventional devices, the fuel exchange device according to the present invention can directly measure the distance to an obstacle and prevent interference.

Furthermore, since multiple ultrasonic wave generators and receivers are simply attached to a conventional gripper, the structure is simple and highly reliable. Furthermore, there is no problem in using it in combination with the conventional one, and by doing so, it is possible to more completely prevent interference.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view schematically showing a liquid metal cooled fast breeder reactor to which a conventional fuel exchange device is applied, partially from the side, and Figure 2 is a partially side view of the pantograph arm type fuel exchange device shown in Figure 1. 3 is a plan view for explaining the operating range of the fuel exchange device in the furnace shown in FIG. 1, and FIG. 4 is a partial view of an embodiment of the fuel exchange device according to the present invention. 5 is an enlarged sectional view showing section D in FIG. 4 in detail, FIG. 6 is an enlarged sectional view showing section E in FIG. 5, and FIG. 7 is an enlarged sectional view showing section E in FIG. 4. FIG. 3 is a plan view showing the operation of the fuel exchange device in the furnace. 1... Reactor vessel, 2... Reactor core, 3... Liquid metal coolant,
6...Rotating plug, 8...Fuel exchange device, 11...Fuel exchange device main body, 12...Rotating housing, 13...Gripper, 14...Folding arm, 15...Pantograph arm, 16...Fixed arm, 17...Gripper guide cylinder, 18... Swing drive device, 19... Bevel gear, 20... Ball bearing, 41... Ultrasonic transmitter/receiver, 42
...MI cable, 43...Signal processing device, 44...Display device, 45...Folding operation shaft, 51...Gripper outer cylinder, 52...Gripper claw, 53...Claw opening/closing rod, 54...Gripper inner cylinder window, 55...Claw opening/closing arm , 61... Mounting base, 62... Housing, 64... Case, 65... Piezoelectric vibrator, 66... Electrode, 67... Signal line.

Claims (1)

[Scope of Claims] 1. In a pantograph arm type fuel exchange device that grasps or releases a large number of fuel assemblies loaded in a core part of a nuclear reactor vessel and exchanges the fuel assemblies, the pantograph arm Ultrasonic waves are emitted on the outer cylinder side of the gripper connected to the tip in the rotating direction of the gripper, and an ultrasonic wave generator/receiver is attached to receive the reflected waves, and the ultrasonic wave generation/reception time is measured. A fuel exchange device characterized by being provided with a circuit. 2. The fuel exchange device according to claim 1, wherein the housing of the ultrasonic generator/receiver is detachably fixed to a mounting base provided on the gripper outer cylinder.