JPS6345558B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a hold-down device for a fuel exchanger that extracts and loads fuel from above a nuclear reactor core.

First, the configuration of a conventional fuel exchanger will be described with reference to FIG. In FIG. 1, 1 is a reactor core composed of a large number of fuel assemblies 2, 3 is a rotary plug in the upper part of the reactor, 4 is a primary coolant in the reactor, and 5 is a fuel exchanger. The fuel exchanger 5 can be roughly divided into an exchanger body 6
and a hold-down device 7. The main body 6 is equipped with a gripper 9 attached to its lower end via an offset arm 8. During operation, the gripper 9 is pulled into the furnace, and the main body is placed on a door valve 10 installed on the rotary plug 3. Thrust bearing 1
It is rotatably supported via 1. On the other hand, the hold-down device 7 includes a hold-down tube 12 that is drawn into the furnace through the rotary plug 3, and a hold-down tube that is connected to the hold-down tube 12 and installed inside the drive device casing 13 on the rotary plug. It is composed of a rotation drive mechanism 14, a hold-down elevating drive mechanism 15, and a hold-down arm 26 formed at the lower end of the hold-down tube 12. The main body 6 and the hold-down tube 12 are connected via a rotation prevention mechanism (not shown) so that they rotate together. The rotational drive mechanism 14 rotates the hold-down tube 12 together with the exchanger main body 6 around its axis via a gear mechanism driven by a motor. On the other hand, the elevating drive mechanism 15 is driven by a motor to move the hold-down tube 12 up and down in the vertical direction of arrow A via a ball screw mechanism. With this configuration, the rotating plug 3
Due to the rotation of and the rotation of the hold-down tube 12,
Position the gripper 9 to a predetermined handling fuel 2a,
Fuel is pulled out and loaded by operating the gripper 9.
In this case, the hold-down cylinder 12 is lowered to the dotted line position and the hold-down arm 26 handles the fuel 2.
The surrounding fuel 2b adjacent to a is held down to prevent the surrounding fuel from floating up when the handled fuel is pulled out during fuel exchange.

In addition to the above-mentioned hold-down function, this hold-down device has a function that allows it to safely support the exchanger main body 6 even when a large earthquake load is applied, and the hold-down tube 12 is designed to be a fairly heavy object. Become. For this reason, the hold-down lifting drive mechanism 15 is particularly large, and the rotary plug 3
It is extremely difficult to install the device in a narrow space on the top surface of the device. In addition, the inertia associated with the lifting and lowering of the hold-down tube 12, which is a heavy object, is also large, so if the hold-down tube 12 collides with the core 1 when lowering due to an operational error, it will damage the fuel, which is a core component. There is an extremely high risk of doing so.

This invention has been made in consideration of the above points, and its purpose is to provide a hold-down device for a fuel exchanger that allows the hold-down elevating drive system to be made smaller and has less risk of damaging the core fuel. .

According to the present invention, this purpose is to use a gripper connected to the exchanger body via an offset arm, to draw out fuel from above the reactor core by operating the gripper,
A guide cylinder is inserted into the furnace through the shield plug of the furnace to guide and support the main body of the pantograph fuel exchanger for loading, a rotating drive mechanism for the guide cylinder for positioning the gripper, and a guide cylinder. a hold-down arm movably surrounding the gripper and disposed inside the lower part of the guide cylinder as separate independent parts for preventing floating of surrounding fuel adjacent to the handled fuel; and a hold-down arm installed on the guide cylinder and mounted on the guide cylinder. This is achieved by configuring it with an elevating drive mechanism that raises and lowers.

Embodiments of the present invention will be described below based on the drawings.

In FIGS. 2 and 3, the same reference numerals as in FIG. 1 indicate the same members. According to the present invention, the hold-down device 7 includes a guide tube 16 that guides and supports the fuel exchanger main body 6, a guide tube rotation drive mechanism 17 similar to the rotation drive mechanism 14 in FIG. 1, and a guide tube 16 as an independent component. It consists of a relatively lightweight cylindrical hold-down arm 18 and an elevating drive system for the hold-down arm 18, the details of which will be described later. The guide cylinder 16 is not driven up and down like the hold-down cylinder 12 in FIG.
The gripper 9 rotates around the center of the axis by the motor drive, and positions the gripper 9 of the exchanger main body. On the other hand, the hold-down arm 18 has lower tips of two operating shafts 20' that are connected in parallel within the guide tube 16 to the lower part of the operation shaft 20 of the hold-down arm that passes through the guide tube 16 in the vertical direction and is guided. An elevator drive motor 21 is supported by
It is connected to the ball screw mechanism 22 via a ball screw mechanism 22.
With this configuration, the guide cylinder 16 is moved to the hold-down arm 18 by the motor drive of the rotational drive mechanism 17.
The gripper 9 rotates around the axis together with the fuel exchanger main body 6, and the gripper 9 rotates in conjunction with the rotation of the rotary plug 3.
positioning. Also, the motor 21 of the lifting drive system
As a result, only the hold-down arm 18 moves up or down in the direction of arrow A between the solid line and the dotted line position depending on the rotational direction of the motor 21 while the guide cylinder 16 remains in the same position. That is, after positioning for fuel exchange, the hold down arm 18
By lowering the gripper 9 to the upper surface of the core 1, it is possible to prevent adjacent surrounding fuel from floating up when the gripper 9 is operated via the offset arm 8 to pull out a predetermined amount of handled fuel from the core 1. Further, since the lifting drive motor 21 is mounted on the guide tube, the hold-down arm 18 can be lifted and lowered regardless of the rotational position of the guide tube 16.

The gripper 9 is operated by an operating mechanism within the exchanger body 6 to move up or down within the hold-down arm 18.

As mentioned above, compared to the conventional hold-down device, the present invention has a hold-down arm configured as a separate part from the guide cylinder for supporting the guide of the main body of the fuel exchanger, and when performing hold-down during fuel exchange, it is difficult to carry heavy objects. The guide tube is excluded from the lifting and lowering movement, and only the hold-down arm, which is a lightweight object, is moved up and down. Therefore, the elevating drive mechanism can be made small, and the equipment on the furnace can be easily arranged even though the upper surface of the rotating plug is narrow. Moreover, the most significant feature is that during hold-down, only the lightweight hold-down arm descends to the top of the core, and the inertia associated with its lifting and lowering is small. Even if the fuel assembly collides with the fuel assembly, the impact force exerted on the fuel assembly is small, and the risk of fuel damage is also reduced, making it possible to obtain a hold-down device with a compact overall structure and high safety.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing the structure of a conventional fuel exchanger, FIG. 2 is a longitudinal sectional view of an embodiment of the present invention, and FIG. 3 is a sectional view taken along the arrow in FIG. 1: Core, 2: Fuel assembly, 2a: Fuel handled,
2b: Ambient fuel, 3: Shiyahei rotating plug, 5:
Fuel exchanger, 6: Exchanger body, 7: Hold-down device, 9: Gripper, 16: Guide cylinder, 17:
Rotation drive mechanism, 18: Hold down arm, 2
0, 20': Operation axis, 21: Lifting drive motor, 2
2: Ball screw mechanism.

Claims (1)

[Claims] 1 A gripper is connected to the exchanger body via an offset arm, and a pantograph type fuel exchanger body is pulled out and loaded from above the reactor core by the gripper operation. a guide tube retracted inward, a rotational drive mechanism for the guide tube for positioning the gripper, and a guide tube movable as a separate independent component, surrounding the gripper and disposed inside the lower part of the guide tube adjacent to the handled fuel. A hold down arm for preventing surrounding fuel from floating up, an operating shaft connected to the hold down arm, and a lifting drive mechanism mounted on a guide tube and raising and lowering the hold down arm via the operating shaft. Features a hold-down device for nuclear reactor fuel exchange machines.