JPH0141235B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a channel box disassembly apparatus for removing attached parts of a fuel assembly channel box used in a boiling water nuclear reactor or the like.

[Technical background of the invention and its problems]

An example of a fuel assembly used in a boiling water reactor is the one shown in Figure 1, in which a large number of fuel rods b are arranged vertically inside a square cylindrical metal channel box a. A handle c for hanging is fixed to the upper end thereof, and a lower tie plate d is fixed to the lower end thereof. Usually, a set of four fuel assemblies is loaded into one cell of the reactor core.

In addition, a channel clip e is attached to the corner of the upper end of each channel box a by a screw f to ensure a predetermined gap between adjacent channel boxes. Chinnel spacers g are attached to the side surface of the upper end of box a.

All of these metal accessories protrude from the outside of channel box a, so when storing spent fuel channel boxes together in a storage pool, for example, each channel box becomes bulky and requires a large storage space. Become. Therefore, in nuclear power plants where the amount of spent fuel is likely to increase in the future, it is an important issue to save storage space by reducing the volume of spent channel boxes as much as possible.

[Purpose of the invention]

The present invention has been made based on the above-mentioned circumstances, and its object is to disassemble a fuel assembly channel box, which enables the removal of accessory parts such as channel clips and channel spacers, and reduces the storage space for used channel boxes. The goal is to provide equipment.

A second purpose is to inhale and purify the metal melt generated when disassembling the accessory parts, thereby preventing contamination of the pool water.

[Summary of the invention]

That is, the first invention provides a support that vertically supports a channel box of a fuel assembly in pool water, a base that is removably placed on the upper end of the channel box, and a base that is attached to the base,
The electric discharge machine is equipped with a machining electrode that faces apart from metal accessories such as channel clips and channel spacers, and by sending discharge sparks between the machining electrode and the accessory parts, these accessories can be machined. This is a disassembly device for a fuel assembly channel box, which removes these accessories from the channel box by melting at least a portion of the fuel assembly channel box.

Furthermore, a second invention has the constituent features of the first invention, and is also equipped with a purification mechanism that sucks in and purifies the metal melt generated during electrical discharge machining, thereby making it possible to prevent pool water from being contaminated. It is.

[Embodiments of the invention]

A first embodiment of the present invention will be described below with reference to FIGS. 2 to 4.

In FIG. 2, reference numeral 1 denotes a fuel storage pool in a boiling water nuclear reactor, and pool water is stored in this fuel storage pool 1 for purposes such as radiation shielding or heat removal. Further, 2A is a channel box accessory removal device, which is constructed as follows.

That is, a container 3 as an example of a support is vertically installed in the pool 1. This container 3 has a container shape with an open top and is adapted to vertically support the channel box a. Further, a processing machine unit 4A is detachably installed at the upper end of the channel box a. This processing machine unit 4A includes a base 5 placed on the upper end of a channel box a, and electric discharge machines 7a, 7b etc. mounted horizontally on this base 5 by brackets 6a, 6b, and cables. The fuel exchanger 9 is suspended by a fuel exchanger 9, and can freely move vertically and horizontally underwater. In addition, the above base 5
A hole 10 is formed in the hole 10 so that it can fit into the handle c of the channel box.

Furthermore, an air cylinder mechanism 12 is attached to a corner portion of the lower surface of the base 5. The rod 13 of the cylinder mechanism 12 can be expanded and contracted in the horizontal direction, and a movable support 14 provided at its tip can be moved toward and away from the side surface of the channel box a. Further, a fixed support 15 is fixed to the base 5 at a position facing the movable support 14.

Further, the electric discharge machines 7a and 7b have machining electrodes 16a and 16b (only one of which is shown) at positions facing away from the channel spacers g and g of the channel box a, and these machining electrodes 16a and 16b
An appropriate gap is formed between the channel spacers g and the channel spacers g to allow discharge sparks to fly. Power supply, operation control, etc. for these electrical discharge machines 7a and 7b are performed by an operation panel 18 via a cable 17.

Further, a purification mechanism 20 is provided for purifying melted metal generated during electrical discharge machining. This purification mechanism 20 consists of a purifier main body 21 installed in the pool water, a water pipe 22, etc., and the suction end of the water pipe 22 is provided at a position near the processing electrodes 16a, 16b, for example, on the base 5. Inlet 23
a, 23b. Further, a pump, a filter, etc. are housed in the purifier main body 21, and the purifier body 21 is configured to return purified water to the pool water.

To remove the channel spacers g, g using the device 2A of this embodiment configured as described above,
First, the spent fuel channel box a is inserted into the container 3 using the fuel exchanger 9. Next, the processing machine unit 4 is placed at the upper end of channel box a.
The base 5 of A is suspended and fitted and supported, and the rod 13 of the cylinder mechanism 12 is extended to hold the channel box a between the movable support 14 and the fixed support 15.

Then, the operation panel 18 controls the electrical discharge machines 7a and 7b.
is driven to generate discharge sparks between the machining electrodes 16a, 16b and the channel spacers g, g to melt them little by little. At this time, the purifier main body 2
1 to suck in the melted material caused by electrical discharge machining,
The water after purification is returned to the pool water.

By the above operation, channel spacers g and g are
Two can be removed at the same time.

Next, a second embodiment of the device 2B of the present invention will be described with reference to FIGS. 5 and 6. This embodiment apparatus is equipped with a processing machine unit 4B for removing the channel clip e, but the basic configuration is the same as that of the first embodiment apparatus 2A.
Common parts will be described with the same reference numerals. That is, 5 is a base, and this base 5 is formed with a hole 10 having a shape into which a handle c can be inserted, and a movable support using a cylinder mechanism 12 similar to the above is provided on the lower surface of the base 5. 14
A fixed support 15 is provided.

Further, the electric discharge machines 7a and 7b are equipped with a bracket 6.
The machining electrodes 16a, 16b are provided in positions facing the channel clips e or corner plates h.

Further, a purification mechanism similar to the purification mechanism 20 of the first embodiment shown in FIG. 2 is connected to the processing machine unit 4B, and its suction port is connected to the processing electrode 16a,
It opens at a position near 16b so that the dissolved material can be inhaled.

The second embodiment device 2B having the above configuration fixes the processing machine unit 4B to the upper end of the channel box a in the same way as the first embodiment device 2A, and then drives the electrical discharge machines 7a and 7b to create the channel creel e. can be removed.

The processing machine unit 4A of both these embodiments,
By alternately using 4B, channel spacers g, g and channel clip e can be removed, so there is no protrusion on the outer surface of channel box a, and therefore the storage space when storing channel box a is reduced. This is something that can be achieved.

Moreover, during electric discharge machining, the operation of the purification mechanism 20 prevents dissolved substances from dispersing into the water, so that a predetermined water quality can be maintained. Also,
All of the above demolition work can be done remotely underwater, which is effective in terms of measures against radiation exposure for workers, and by employing electric discharge machines 7a and 7b, automation and high efficiency of the work can be achieved. That is.

The volume of the channel box a after removing the accessory parts can be further reduced by crushing it with a press or dividing it by cutting it diagonally.

As described above, in the first aspect of the present invention, a base is placed on a channel box held on a support in a pool, and metal accessories such as channel clips and channel spacers are attached by an electric discharge machine fixed to the base. It is designed to allow parts to be removed, and these attached parts can be automatically removed by remote control underwater in the pool, preventing workers from being exposed to radiation during dismantling work, and increasing work efficiency. . Since the protrusions on the outer surface of the channel box can be removed, the volume of the used channel box is reduced, the storage space can be reduced, and the space of the fuel pool etc. can be used effectively.

Moreover, according to the second invention, since a purification mechanism is provided in addition to the first invention, it is possible to obtain the same effects as the first invention, and by employing the purification mechanism. Since it is possible to purify the melted substances generated during electrical discharge machining, it is possible to prevent contamination of pool water.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a fuel assembly, Fig. 2 is a schematic diagram showing the usage state of the first embodiment of the device of the present invention, and Fig. 3 is a perspective view of a fuel assembly.
4 is a plan view of the same device, FIG. 4 is a side view, FIG. 5 is a plan view showing a second embodiment of the device of the present invention, and FIG. 6 is a side view of the same device. a... Channel box, e... Channel clip (metal accessory), g... Channel spacer (metal accessory), 1... Pool, 2A, 2B
...Attachment parts removal device. 3...Container (support),
5... Base, 7a, 7b... Electric discharge machine, 16a,
16b... Processing electrode, 20... Purification mechanism.

Claims (1)

[Scope of Claims] 1. A support that is provided in pool water and vertically supports a channel box of a fuel assembly, a base that is removably placed on the upper end of the channel box, and a support that is attached to the base. , an electric discharge machine having machining electrodes spaced and opposed to metal attachment parts provided on the outer surface of the channel boxes to maintain a distance between adjacent channel boxes. Channel box disassembly equipment. 2. A support that is installed in the pool water and vertically supports the channel box of the fuel assembly, a base that is removably placed on the upper end of the channel box, and a support that is attached to the base and provided on the outer surface of the channel box. This electric discharge machine has machining electrodes spaced apart from each other in a metal accessory part to maintain the distance between adjacent channel boxes, and the electric discharge machine sucks and purifies the metal melt generated during electric discharge machining. A disassembly device for a fuel assembly channel box, characterized in that it is equipped with a purification mechanism that cleans the fuel assembly.