JPS5817440B2 - Method and equipment for cleaning fuel bundles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention cleans and removes limescale adhering to the outer surface of a fuel bundle (fuel bundle) in which a large number of nuclear reactor fuel rods are arranged and bundled in a lattice pattern. The present invention relates to a fuel bundle cleaning method and cleaning device that can centrifugally separate clear water and solid content and recover limescale as solid content.

The main cause of radiation exposure associated with maintenance and inspection work of nuclear reactor systems is that corrosion products in the reactor water are transferred to the sub-reactor system and adhere or deposit on the inner surfaces of equipment piping, resulting in an increase in the radiation dose rate in the working environment. It is believed that this is to increase the

Furthermore, most of these radioactive corrosion products are loosely attached to the surface of the fuel rods as water scales (mainly composed of Fe203), and when this flakes off, it becomes an important source of radioactive corrosion products in the reactor-subsystem. It is thought that it is a supply source.

For this reason, removing scale from fuel rods is very effective in reducing the radiation dose rate of equipment piping in the reactor-subsystem, but removing scale from fuel rods is difficult for waste with high radioactivity levels. At the same time with generation, atoms.

This is an extremely difficult task, as it must be done without damaging the reactor or fuel rods.

The present invention has been made in view of these points, and it is possible to clean the nuclear reactor and fuel rods without damaging them.

An object of the present invention is to provide a method for cleaning a fuel bundle that can be cleaned without spreading radioactive contamination or generating radioactive secondary waste, and an apparatus for carrying out the cleaning method.

In the present invention, the fuel bundle is produced from a nuclear reactor.

When the fuel bundle is taken out and immersed in the fuel pool where water is stored and the channel cover is removed, the relatively low pressure from the outer circumference of the fuel bundle is 5 kg/
Limescale is removed by spraying water of less than i, and the removed limescale is directly twisted, separated from clear water in a centrifugal separator installed in the feed pool, and disposed of as solid matter. The fuel bundle is cleaned by storing it in a container and then discarding it.

In the present invention, a cleaning tower that surrounds the fuel bundle and prevents cleaning waste liquid from diffusing into the fuel pool, a spray nozzle header disposed in the cleaning tower and provided with a spray nozzle for cleaning, and A waste liquid transfer unit that collects the washed limescale and transfers it to a centrifugal separation unit, a centrifugal separation unit that separates the cleaning waste liquid into clear water and solids, and a centrifugal separation unit that collects the washed water scale and transfers it to a centrifugal separation unit. A cladding tank containing the fuel is installed in the fuel pool so that it is well shielded from water.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an example of a fuel bundle cleaning device according to the present invention.

In the figure, reference numeral 11 is a cleaning tower, and a fuel bundle 12
and the spray nozzle header 13.

This cleaning tower 11 is installed perpendicularly to the bottom surface B of the fuel pool below the water level of the fuel pool so as to be sufficiently shielded by water.

The spray nozzle header 13 has a rectangular ring shape having a rectangular through hole 14 that matches the shape of the fuel bundle 12, as shown in its upper plane in FIG.

A plurality of spray nozzles 15 are provided on the inner circumference of the through hole 14 so that pressurized water can be uniformly injected into the fuel bundle 12.

The spray nozzle header 13 connects the inside of the cleaning tower 11 to the cleaning tower 1.
The rudder 13 is disposed so as to be movable in the longitudinal direction of the spray nozzle, and the movement of the ladder 13 to the spray nozzle is performed by a drive section.

As shown in FIGS. 1 and 3, one driving section of the spray nozzle header 13 is an electric motor 16 placed on the floor F above the fuel pool. Gear part 17 that changes the transmission direction, gear part 1
Universal joint 19 that transmits the rotational force from 7 to the feed screw rod 18
, a feed screw rod 18 screwed into a nut portion 20 provided at one end of the spray nozzle header 13, and a guide rod 21 disposed within the cleaning tower 11 so as to pass through the other end of the spray nozzle header 13. There is.

The feed threaded rod 18 has a threaded portion that is at least longer than the longitudinal length of the fuel bundle 12 in order to linearly move the spray nozzle header 13 from above the fuel bundle 12 to a position below the fuel bundle 12 .

A water supply section is connected to the ladder 13 to the spray nozzle, and pressurized water (fuel bundle outer surface pressure of 5 kg or less) is injected from the spray nozzle 15.

If the pressure water becomes high pressure (5 ky/i or more), there is a risk of damaging the fuel bundle 12.

As shown in FIG. 1, the water supply section consists of a pump 22 placed on the floor F of the fuel pool, a flexible pipe 23 connecting the discharge side of the pump 22 and the spray nozzle header 13, and the fuel pool. It consists of a suction pipe 24 that extends below the water surface and is connected to the suction side of the pump 22.

Reference numeral 25 denotes a waste liquid transfer section that transfers the washing waste liquid generated in the washing tower 11 to a centrifugal separation section 26, which will be described later, and connects the washing tower 11 and the centrifugal separation section 26.

The waste liquid transfer section 25 is constructed by protruding a submersible pump 28 into a pipe 27 that connects the washing tower 11 and the centrifugal separation section 26 .

The centrifugal separator 26 is a separator, such as a centrifuge or cyclone separator, that can separate and recover the solid content in the cleaning waste liquid by centrifugal force without generating secondary waste, and collects the separated clear water. It has an opening 29 for discharging into the fuel pool and an outlet nozzle 31 for transferring the solids to the next cladding receiver 30.

The cladding tank 30 is connected to the outlet nozzle 31 of the centrifugal separator 26 and rests on the bottom surface B of the fuel pool, and this connection is made by a remotely removable joint 32.

FIG. 4 is a partial sectional view showing this connection state.

A push rod 33 is fixed in the outlet nozzle 31 of the separating section 26 so that its tip protrudes from the outlet nozzle 31 in the axial direction.

On the other hand, an inlet nozzle 35 having the same diameter as the outlet nozzle 31 is protruded from the cladding tank 30, and a spring 35 is provided in the cladding tank 30 directly below the inlet nozzle 35 by a support plate 36.
1 is arranged, and a disk-shaped valve seat 3 is provided at the upper end of the spring 37.
4 is placed.

The tip ends of the outlet nozzle 31 of the separating section 26 and the inlet nozzle 35 of the cladding tank 30 are still in contact with each other, and a gasket seal 38 is attached to the abutting part.

When the centrifugal separator 26 and the cladding tank 30 are separated, the valve seat 34 is pressed upward by the spring 37, sealing the lower end of the inlet nozzle 35 and preventing water from entering the cladding tank 30. Inflow and outflow of solids from inside the cladding tank 30 are prevented.

Next, when the centrifugal separator 26 and the cladding tank 30 are combined, the tip of the push rod 33 pushes the valve seat 34 downward against the spring 37, opening the inlet nozzle 35 and opening the outlet nozzle. 31 and the inlet nozzle 35 are sealed by a gasket seal 38, and the separation part 2
6 to the cladding tank 30 is formed with airtightness.

FIG. 5 is a sectional view showing another embodiment of the fuel bundle cleaning device according to the present invention.

In this embodiment, the drive unit that relatively moves the spray nozzle header in the longitudinal direction of the fuel bundle is performed by a self-propelled trolley, and a jet ejector system is used in the waste liquid transfer unit instead of a submersible pump. .

Reference numeral 41 denotes a cleaning tower, which is disposed laterally with respect to the bottom surface B of the fuel pool.

On the inlet side of this cleaning tower 41, a square ring-shaped spray nozzle header 42, which is provided with a spray nozzle and has a similar shape to that shown in FIG. ing.

This spray nozzle header 42 has a pipe 43 from the discharge side of the pump 22 placed on the floor surface B of the fuel pool.
is connected, and water sucked up from the suction pipe 24 on the suction side is sprayed from the spray nozzle.

Reference numeral 44 is a self-propelled trolley, and a remote-controllable electric motor 4
5, the wheels 46 are rotationally driven via a suitable transmission means so as to be able to move in the longitudinal direction within the washing tower 41.

A pair of supports 47 for mounting the fuel bundle 12 are fixed to the upper part of the self-propelled trolley 44 at intervals corresponding to the longitudinal length of the fuel bundle 12 to be mounted. ing.

A waste liquid transfer section 48 is disposed between the washing tower 41 and the centrifugal separation section 26, and in this embodiment, a jet ejector system is used.

That is, a pump 49 is placed on the floor surface B of the fuel pool, and the pump 49 sucks in pool water through a suction pipe 50 and increases the pressure.
The cleaning waste liquid can be transferred to the centrifugal separation section 26 by injecting it through a discharge pipe 52 inserted into a connecting pipe 51.

The centrifugal separator 26 and the cladding tank 30 are connected by a remotely removable joint 32, as in the previous embodiment.

The operation of the fuel bundle cleaning device according to the present invention having such a configuration will be explained.

First, in the embodiment shown in FIG.
2 is suspended from the top of the cleaning tower 11 with the channel cover removed so as to pass through the through hole 14 of the spray nozzle/ladder 13, and the receiver at the bottom of the cleaning tower is placed on the seat 53.

The upper tie plate of fuel bundle 12 is then supported by a remotely controllable gripping mechanism such as an air cylinder.

In this case, depending on the size of the fuel rods, the pressure of the spray water, etc., additional support for the center of the fuel bundle 12 may be added.

Next, the electric motor 16 is driven to rotate the feed screw rod 18, and the screw feed action with the nut portion 20 of the spray nozzle header 13 screwed thereon causes the spray nozzle header 1 to rotate.
3 in the longitudinal direction of the washing tower 11.

Po at the same time. The pump 22 is driven to suck and pressurize pool water, send it to the spray nozzle header 13, and spray it from the spray nozzle 15.

In this way, while spraying pressurized water from the spray nozzle 15, the rotation direction of the electric motor 16 is changed, etc., and the spray nozzle header is installed.

By reciprocating the fuel bundle 13, pressurized water is uniformly injected onto the outer surface of the fuel bundle 12, and water scale adhering to the outer surface is removed.

In the embodiment shown in FIG.
The self-propelled trolley 44 is mounted and fixed on the column 47 of No. 4, and by driving the electric motor 45, the self-propelled trolley 44 is reciprocated with a constant longitudinal force of the washing tower 41.

At the same time, the pump 22 is driven to increase the pressure of the pool water and send it to the spray nozzle from the spray nozzle 2'42:
Inject.

As a result, limescale adhering to the outer surface of the fuel bundle 12 is removed.

The lime scale thus removed in the washing tower becomes washing waste liquid together with the injected water, and is transferred to the centrifugal separation section 26 by the waste liquid transfer section.

. In the embodiment shown in FIG. 1, this washing waste liquid is transferred by driving the submersible pump 28, and in the embodiment shown in FIG. 51, along with cleaning waste liquid.

This is carried out by flowing the liquid to the centrifugal separation section 26.

The cleaning waste liquid transferred to the centrifugal separation unit 26 is separated into clear water and solids by centrifugal force, and the clear water is transferred to the opening 29.
is discharged into the fuel pool, and the solids are discharged from the outlet nozzle 3
1 to a cladding tank 30 where it settles and accumulates.

The cladding tank 30 filled with solids can be removed from the centrifugal separator 26 by disconnecting the remote detachable joint 32.
It is separated from the fuel and transported outside the fuel pool to be disposed of.

Then, a new cladding tank is again connected to the centrifugal separator 26 for exchange.

As described above, the fuel bundle cleaning device according to the present invention can perform tasks ranging from fuel bundle cleaning to waste treatment.
All can be done in a well-shielded fuel pool with water, reducing radiation exposure associated with cleaning operations.

In addition, processing of cleaning waste liquid is carried out in the immediate vicinity of the place where it is generated.
The radioactive waste contained in the removed limescale is directly packed into a disposal container in the fuel pool without being taken out of the fuel pool, which prevents the spread of radioactive contamination and the generation of radioactive secondary waste. do not have.

Additionally, the fuel bundles are removed from the reactor and cleaned by injecting water at relatively low pressure in a fuel pool without causing damage to the reactor or fuel rods.

In the embodiment of the present invention, as methods for moving the spray nozzle header relative to the longitudinal direction of the fuel bundle, there are two methods: moving the spray nozzle header using a feed threaded rod, and a method in which the spray nozzle header is fixed and the fuel bundle is moved relative to the longitudinal direction of the fuel bundle. Although a method of moving the spray nozzle header or fuel bundle using a self-propelled trolley was used, it is also possible to move the spray nozzle header or the fuel bundle using a wire hoisting method.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a fuel bundle cleaning device according to the present invention, FIG. 2 is a top plan view of a spray nozzle header, and FIG. 3 is a longitudinal sectional view showing an example of a drive section of the spray nozzle header.
FIG. 4 is a partial cross-sectional view showing the state of connection between the centrifugal separator and the cladding tank, and FIG. 5 is a longitudinal cross-sectional view showing another embodiment of the fuel bundle cleaning device according to the present invention. 11.41...Cleaning tower, 12...Fuel bundle, 13.42...Spray nozzle header, 15...Spray nozzle, 16...・
・Electric motor, 18... Threaded rod, 20...
Nut part, 22.49... Pump, 25.48
...Waste liquid transfer section, 26 ... Centrifugal separation section, 30 ... Crud receiving tank, 32 ...
...Remote detachable joint, 44...Tear-travel type trolley.

Claims (1)

[Claims] 1. A fuel bundle is immersed in water, and pressurized water is injected onto the outer surface of the fuel bundle under water at a pressure of 5 kgΔ or less to adhere to the outer surface of the fuel bundle. The washed waste liquid containing the removed scale is directly transferred to a centrifugal separation section to separate clear water and solids in water, and the centrifuged solids are stored in a container in water. A method for cleaning a nuclear reactor fuel bundle comprising: 2. An elongated cylindrical cleaning tower, a ring-shaped spray nozzle header provided with a spray nozzle that injects pressurized water to the inner periphery of the cleaning tower, and a fuel bundle to be cleaned with this spray nozzle header. a drive unit that relatively moves the spray nozzle in the longitudinal direction; a water supply unit that supplies pressurized water to the spray nozzle of the spray nozzle header; a centrifugal separation unit that separates the cleaning waste liquid into clear water and solids; and the cleaning tower. and a waste liquid transfer section that connects the washing tower with the centrifugal separation section and transfers the washing waste liquid from the washing tower to the centrifugal separation section, and a cladding tank that accommodates the solids separated in the centrifugal separation section, A cleaning device for a nuclear fuel bundle, characterized in that a cleaning tower, a spray nozzle header, a centrifugal separation section, a waste liquid transfer section, and a cladding tank are submerged in water. 3. Claim 2, characterized in that the spray nozzle header is arranged to be movable longitudinally within the cleaning tower, and the fuel bundle to be cleaned is fixed within the cleaning tower.
Fuel bundle cleaning device as described in Section 1. 4. The fuel bundle cleaning device according to claim 2, wherein the spray nozzle header is fixed within the cleaning tower so that the fuel bundle to be cleaned can be moved longitudinally within the cleaning tower. L