JPH03181897A - Dismantling method of radioactively contaminated fluid pump - Google Patents

Abstract

PURPOSE:To prevent radioactive contamination of working atmosphere for pump dismantlement and to intend improvement of working efficiency by sealing and by isolating a space between parts with a non-permeating and flexible cylindrical body against radioactively contaminating fluids. CONSTITUTION:A space between periphery of an opening part 23 of a pump casing 17 and an outer circumference of a pump cover 19, is sealed by a cylindrical body 25. Then, a wire 26 is hooked to hang up the cover 19 and an inner part 18, and to separate them from the casing 17, and, after that, a connecting part of the cylindrical body 25 which maintains the sealing, is made to shrink for closing the body and being isolated. In this way, by effecting sealing among parts and separating them with the non-permeating and flexible cylindrical body 25 against radioactively contaminating fluids, no leakage and dispersion of the radioactively contaminating substances occur, and there is no need of a local isolation room surrounding the working space, or a local ventilation device, and also there is no need to wear working masks and protection clothings as well, and consequently working efficiency can be much improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for dismantling a pump for pumping radioactively contaminated fluid in nuclear power generation, etc., and more specifically, the present invention relates to a method for dismantling a pump for pumping radioactively contaminated fluid in nuclear power generation, etc. Regarding how to disassemble the pump.

[Conventional technology]

Pumps for radioactively contaminated fluids, such as cooling water recirculation pumps for boiling water reactors, are periodically dismantled for inspection, their internal parts are checked, and repairs are made as necessary.

The conventional procedure for disassembly is to first stop the flow in the piping with a stop valve, etc., then remove the pump drive section from the pump body, and then remove the pump cover and pump casing, which support part of the inner part. In many cases, the bolts that connect the inner parts are removed, and a part of the inner part is lifted up with a crane or the like along with the cover to separate it from the casing. At that time, the radioactive contaminated fluid remaining in the pump body may evaporate directly from the pump body into the air, or drip or evaporate from a part of the inner that is lifted and moved, leaking or diffusing into the room and becoming radioactive. Produces pollution. For this reason, a partially closed room equipped with a local exhaust system has been set up in the area where such demolition is to be carried out, and dismantling work is carried out inside the room by workers wearing full-face masks and protective clothing.

[Problem to be solved by the invention]

However, this conventional demolition method requires the installation of a closed room and its re-dismantling, which increases man-hours and costs, and also reduces work efficiency due to work space limitations and the wearing of full-face masks. There were problems, and improvements were strongly desired.

Therefore, the present invention aims to solve the problems with the conventional disassembly methods, and to provide a new disassembly method that reduces man-hours and costs and has high work efficiency.

[Means to solve the problem]

To achieve the above object, the disassembly method of the present invention is a method for disassembling a pump for a radioactively contaminated fluid, and when separating the parts constituting the pump body, the parts to be separated are kept in contact with the fluid. It is characterized in that the parts are separated while being sealed with a permeable and flexible cylindrical body, and then the cylindrical part that connects the separated parts is closed and separated.

[For production]

In the disassembly method of the present invention, the parts to be separated are separated while being sealed with the fluid-impermeable and flexible cylindrical body, so that the externally exposed parts of the separated parts are sealed by the cylindrical body. , there will be no leakage or dispersion of radioactive contaminants to the outside. The parts separated in this way are then separated by closing the cylindrical part of the part that connects the parts, so that the connection by the cylindrical body is released and the parts are completely separated, and the separated parts of the cylindrical body are separated. Leakage is prevented by the closure.

Each component separated from the pump body in this way is separated in such a manner that its externally exposed portion is sealed with a cylindrical body that does not transmit radioactively contaminated fluid, so that the working environment is not contaminated with radioactively contaminated substances.

〔Example〕

Next, an example in which the disassembly method of the present invention is applied to dismantling a cooling water recirculation pump for a boiling water reactor will be described.

FIG. 7 is a diagram schematically showing a boiling water reactor and its cooling water recirculation pump. The heat generated in the core 2 of the reactor 1 heats and evaporates the cooling water 3, and the water separator 4 in the upper part
It passes through a steam dryer 5 and is taken out from an evaporation outlet 6 at the upper end of the furnace.

On the other hand, the cooling water supplied from the plurality of water supply lowers around the outer periphery of the reactor and the cooling water separated from the steam-water separator 4 are supplied to a plurality of jet pumps driven by the drive flow from the recirculation channel 8 provided outside the reactor. After being sent downward from the vicinity of the core by 9, it ascends within the core.

The recirculation flow path 8 includes a common recirculation pump 10, stop valves 11 before and after it, a main pipe 12 that connects them, a header 13 that surrounds the reactor 1, and a plurality of branch pipes that supply driving flow to each jet pump 9. It consists of I4.

To disassemble the recirculation pump lO for periodic inspection or the like, first close the stop valves 11 at the front and rear of the pump, and then remove the drive section 16 from the pump body 15. At the same time, remove the bolts (not shown) attached to the flange of the pump cover. Next, in the pump main body 15, the parts to be separated are sealed with respect to the cooling water using an impermeable and flexible cylindrical body. The material of the cylinder may be a synthetic resin sheet such as polyethylene, polyvinyl chloride, polyester, fluororesin (Teflon R, etc.), polystyrene, or a synthetic rubber sheet such as styrene-butadiene rubber or silicone rubber, but preferably transparent or A translucent soft film is best.

The pump body 15 is connected to the pump casing 17. The pump body 15 is shown in FIG. Inner part 18. The pump cover 19 is a main component, and the inner part 18 further includes an impeller 20, an underwater bearing 21, and a drive shaft 22.

The inner part 18 is adapted to be inserted into and removed from the casing through an axial opening 23 of the pump casing 17, and its drive shaft 22 passes through the pump cover 19 connected to the upper part and extends upwardly. It is extended to allow connection with the output shaft of the removed drive unit.

Further, the pump cover 19 is bolted to the pump casing 17 at its lower flange portion. Note that FIG. 1 shows the state in which these bolts have been removed.

In FIG. 1, the distance between the periphery of the axial opening 23 of the pump casing 17 and the lower outer periphery of the pump cover 19, and the distance between the periphery of the drive shaft through hole at the top of the pump cover 19 and the upper outer periphery of the drive shaft 22 are shown. It is sealed with a cylindrical body 25. The periphery of these cylindrical bodies 25 is attached and fixed to the sealing part of parts such as the pump casing by adhesive or adhesive via sealing tape, and its length is determined when the parts are separated a predetermined distance from each other as will be described later. , of sufficient length to maintain a seal therebetween.

As shown in Figure 1, each cylinder 25
After sealing, as shown in FIG. is fastened, and the inner part 18 is lifted up a predetermined distance along with the pump cover 19 upward as shown by the arrow to separate it from the pump casing 17. At this time, the seal between the pump casing 17 and the pump cover 19 is maintained by the cylindrical body 25 that connects them.

The hook portion 24 is made of an eye bolt, and its lower portion is removably screwed into a screw hole on the upper surface of the pump cover and the upper surface of the drive shaft 22.

Next, as shown in FIG. 3, the portion of the cylindrical body 25 connecting the pump casing 17 and the pump cover 19 is reduced and closed, and separated. As a method of closing and separating, for example, as shown in the partially enlarged view of FIG. 3A, a simple method is to tightly wrap a certain length of vinyl tape 27 to close it, and then separate it by cutting the middle part. be. Alternatively, instead of wrapping the vinyl tape 27, a method may be used in which the closed portion is held between heated holding tools and the inner wall surfaces of the cylinder are thermally welded.

Next, as shown in FIG. 4, with the pump cover 19 lifted, the impeller 20 of the inner part 18 is connected to the drive shaft
At the same time, it is lowered downward from the inner part 18 as shown by the arrow and separated.

After placing the impeller 20 in the container 31, the chain 29 is removed. At that time, pump cover 19
The seal of the through hole is maintained by a small diameter cylinder 25 that connects the periphery of the through hole and the upper outer periphery of the drive shaft 22. Therefore, the cylindrical body 25 should have a sufficient length to cover the predetermined distance by which the drive shaft 22 is separated from the pump cover 19.

On the other hand, the seal between the separated impeller 20 and drive shaft 22 and the pump cover 19 is maintained by the upper closed and separated cylinder 25 with a large diameter in FIG. Therefore, the cylindrical body 25 must have a sufficient length to cover the required distance for separating the drive shaft 22 from the pump cover 19 in the state shown in FIG. 3.

Next, as shown in FIG.
A cylindrical body 25 with a small inner diameter connects the upper parts of 2.
Both parts are integrally closed and separated. Fifth
Figure A is an example of performing such occlusion separation in a manner similar to Figure 3A.

Finally, as shown in FIG. 6, the pump cover 19 and the remaining part of the inner part 18, which had been suspended by a crane or the like, are lowered into the container 30 as shown by the arrows and placed thereon, and then the wire 26 is By removing the main parts of the pump body, the separation is completed with the openings through which radioactive contaminants leak or diffuse to the outside sealed by the cylinder.

〔Effect of the invention〕

Since the disassembly method of the present invention has the above configuration, it has the following effects.

1) Unlike the conventional method, there is no need for a local closed room surrounding the work space and its local exhaust system, so the number of man-hours and costs are significantly reduced.

2) There is no need to wear a special full-face mask or protective clothing for work, so work efficiency is high.

3) Since the contaminated waste is only a thin cylinder, the amount of contaminated waste is extremely small.

4) Opportunities for worker exposure to radiation are significantly reduced.

[Brief explanation of drawings]

1 to 6 are process diagrams of the disassembly procedure when applied to the recirculation pump shown in FIG. 7 as an example of the disassembly method of the present invention, and FIGS. 3A and 5A are respectively FIGS. 3 and 5. A partially enlarged view of Figure 5, and Figure 7 is a schematic diagram of a boiling water reactor and its recirculation pump. Main body 17...Pump casing 19...Pump cover 21...Underwater bearing 23...Axial opening 25...Cylinder body 27...Vinyl tape 29...Chain 31...Container 16 ...Drive part 18...Inner part 20...Impeller 22...Drive shaft 24...Holding part 26...Wire 28...Holding part 30...Container

Claims (1)

[Claims] In a method of dismantling a radioactively contaminated fluid pump,
When separating the parts constituting the pump body 15 from each other, the parts to be separated are sealed against the fluid with a flexible cylindrical body 25, and then the separated parts are separated. A method for dismantling a fluid pump with radioactive contamination, the method comprising closing and separating the connected cylindrical portions.