JP2008012794A - Method and apparatus for reducing volume of sponge media - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently pack sponge media contaminated with radioactive substances in a cylinder which is a discard container with regard to a method for reducing the volume of the sponge media. <P>SOLUTION: In a method for reducing the volume the sponge media, when the volume of the sponge media 10 is reduced by compressing/heating the sponge media 10, aqueous urethane in a mass ratio of 5-20% of the mass of the sponge media 10 is added to the sponge media 10, and a required load is applied to reduce its volume. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sponge medium (as a blasting material used to peel off a coating film on an inner wall by periodically draining a large water tank (such as a suppression chamber) in a nuclear power plant and peeling off the coating film on the inner wall. The present invention relates to a sponge media volume reducing method for efficiently packing a blast material medium) into a metal container as a radioactive pollutant, and an apparatus used therefor.

  Conventionally, it is common to use a steel grid as a blasting material to peel off the coating on the inner wall of a large tank in a nuclear power plant. However, in this method, the blasting material has a strong rebound and the operator must be heavily equipped. In addition, the visibility is poor due to dust, the working environment is deteriorated, and the working efficiency is lowered. Therefore, in recent years, a blast material in which a polishing material such as granular alumina or steel is incorporated in a sponge such as urethane foam is often used. The sponge media is flattened when it collides with the workpiece, and the blast material collides at a high speed to exert a blasting effect, and at the same time, suppresses the scattering of a fine coating film and dust. Further, since the sponge media is flattened, there is little rebounding, the operator can be lightly equipped, and the workpiece can be easily cured.

When the sponge media is used for blasting of nuclear equipment, it is contaminated with radioactive materials. Therefore, it is necessary to collect the contaminated sponge media, pack it in a metal container, and dispose it.
In such a case, conventionally, for example, as a waste processing method, it is put into a waste container which is a compression chamber and compression-molded by a heat compression volume reduction machine, and the volume of the waste is reduced to a lightweight volume-reduction molded product. There is a known method (see Patent Document 1).
Japanese Patent Laid-Open No. 2003-164836

  However, the conventional methods for subtracting waste are those that can be reused as plastic (synthetic fiber), paper, garbage, and other resources (recycling into garbage), and are the radioactive materials targeted by the present invention. It is not impossible to reuse as waste fuel etc. like contaminated sponge media. Therefore, there is a need for a volume reduction method that can efficiently dispose of waste that is contaminated with radioactive materials and cannot be reused, such as the sponge media. The sponge media volume reduction method and apparatus according to the present invention have been proposed in order to solve such problems.

  The gist of the present invention for solving the above-mentioned problems of the sponge media volume reduction method according to the present invention is to reduce the volume of the sponge media by compressing and heating the sponge media. In other words, water-based urethane is added at a mass ratio of 5% to 20% to reduce the volume by applying a required load.

The heating temperature is 100 ° C. to 120 ° C .;
Heating time is 50 minutes to 150 minutes;
Sponge media is placed in a cylinder having a low and low cylindrical body, and when a load is applied to the sponge media with the piston for the cylinder, a through hole is provided in the piston, and an opening ratio by the through hole is 40% to 80%. %,
Is included.

The gist of a volume reduction device for sponge media according to the present invention is that an electric furnace is provided with a cylinder having a low and low cylindrical body, a piston for the cylinder, and a part of a piston rod connected to the piston. One end portion of the piston rod protrudes upward from a through hole provided in the upper portion of the electric furnace, and a load means and a displacement meter are connected to one end portion of the protruding piston rod.
Furthermore, the one end part of the heat-resistant piping of the vacuum apparatus which makes the inside of this cylinder a negative pressure is connected with the said cylinder from the outside of an electric furnace.

  According to the method and apparatus for reducing the volume of sponge media of the present invention, when the sponge media contaminated with a radioactive substance is put into a cylinder and compressed, the water-based urethane as a binder for the sponge media is reduced by 5% to 20% by mass ratio. In addition, by compressing, the volume reduction rate (%) comparing the volumes before compression and after compression / curing is most effective. Therefore, it becomes possible to store a lot of sponge media in the container and discard them, and it is possible to reduce the disposal cost of the substances contaminated with radioactive substances.

Also, when heat-treating the sponge media and the aqueous urethane of the binder, if the heating temperature is 100 ° C. or less, the water content of the aqueous urethane does not evaporate, so the whole is not cured. If the temperature exceeds 120 ° C., a part of the sponge material urethane may be decomposed to generate harmful substances. As a result, the volume reduction rate of sponge media is most effective.
Furthermore, during the heating time, the volume reduction rate of the sponge media is effective for 50 minutes or more, but when heated for a long time, part of the sponge material urethane decomposes and the generation of harmful substances Therefore, 150 minutes is the limit.

  The hole area ratio of the cylinder piston is necessary to promote water evaporation of the water-based urethane as a binder, and the volume reduction ratio is most effective when the hole area ratio is 40% to 80%.

  The sponge media volume reducing device according to the present invention makes it possible to pack more sponge media contaminated with radioactive substances in a metal container. Furthermore, by making the inside of the cylinder negative pressure with a vacuum device, the load of reducing the volume of sponge media with the piston is reduced, and the time required for volume reduction is greatly shortened (about 1/3).

  As shown in FIGS. 1 to 2, the sponge media volume reducing apparatus 1 according to the present invention includes a cylinder 3 having a low and low cylindrical body (as an example, a diameter of about 500 mm), and a cylinder for the cylinder 3. Pistons 4 a and 4 b and a piston rod 5 a connected to the pistons 4 a and 4 b via a pressing jig 6 are provided, and one end portion 5 b of the piston rod 5 a is provided at the top of the electric furnace 2. The pressing device 8 is connected by a connecting member 9 via a load meter 7 to one end portion 5b of the protruding piston rod 5a.

  As shown in FIG. 2A, the pistons 4a, 4b are metal disk-like flat plates having a desired thickness, and are provided with through holes 4c. As shown in FIG. 4, the opening ratio (also referred to as the opening ratio, (the total area of the through-hole 4c / the area of the disc-shaped flat plate) × 100%) by the through-hole 4c is the range where the volume reduction rate is the best. 40% to 80%.

Here, the volume reduction rate is a comparison of the volumes of the sponge media 10 that is an object to be compressed by the cylinder 3 before compression and after compression / curing. As shown in FIG. 5, assuming that the height H of the state in which the sponge media 10 is placed in the cylinder 3, the height h 1 of the compressed sponge media 10, and the height h 2 of the heat-cured sponge media 10, Since the cross-sectional area is constant, even if compared by height (H, h1, h2),
Volume reduction rate (%) = compression heating strain rate (%) = (h1 / H) × (h2 / h1) = h2 / H. Here, (h1 / H) is a compression ratio after compression with respect to the sponge media 10 before compression, and (h2 / h1) is a return rate after heating and curing with respect to the height at which the sponge media 10 is compressed. .

  The pistons 4 a and 4 b are configured to transmit a compressive load by a flat pressing jig 6, and one end portion 5 b of the piston rod 5 a protrudes upward from a through hole 2 a at the top of the electric furnace 2. . The one end 5 b is connected to the push rod 8 a of the pressing device 8 by a connecting member 9. A load meter 7 with a displacement meter 7a is provided in the middle of the push rod 8a.

  As shown in FIG. 2 (B), the pressing jig 6 is a metal ring-shaped ring body, which is integrated with the center portion by a cross-shaped connecting portion (rim), so that moisture can escape upward. Thus, a large gap is provided. As shown in FIGS. 1 and 3, the pressing device 8 that presses the pressing jig 6 includes, for example, a screw rod body 8b that is fixed and raised from a base 12, and a lifting plate 8c that is screwed to the screw rod body 8b. The lift plate 8c is moved up and down by rotating the screw rod body 8b, and the push rod 8a suspended from the lift plate 8c is connected to the piston rod 5a. .

  Further, as shown in FIGS. 1 and 3, one end of a heat-resistant pipe 11 a of a vacuum device (not shown) for making a negative pressure in the cylinder 3 is connected to the cylinder 3 from the outside of the electric furnace 2. Has been. The mechanical configuration of the pressing device 8 is not limited to that shown in the drawings, and other known techniques for pressing may be employed as long as the pressing means achieves the object of the present invention.

  Using the sponge media reducing device 1, for example, the sponge media 10 collected and used as a blasting material for peeling off the coating film on the inner wall of a large water tank in a nuclear power plant and contaminated with radioactive substances can be used as a container for disposal. A method of compressing and packing the cylinder 3 will be described.

  First, for example, 5% to 20% of water-based urethane as a curing agent is added to the mass of the sponge media 10 made of foamed polyurethane, which is used and recovered as a blast material.

  The water-based urethane serves as a binder for bonding sponges, which are blast material carriers, and its components are 35% polyurethane and 65% water by weight. This is highly safe for the human body even in a closed space work such as a paint film peeling work in a large water tank in the nuclear power plant.

  As shown in FIG. 6, in order to obtain the optimum binder ratio with respect to the sponge media 10, for example, the heating temperature is 100 ° C., the heating time is 60 minutes, the compression force is 1 kN, and the height (original thickness) of the sponge media 10 As a result of obtaining the volume reduction rate of the sponge media 10 under a certain condition of 50 mm, the water-based urethane is 5 to 20% in mass ratio ((binder mass / mass of sponge media 10) × 100%). It is what.

  As for the heating temperature, as shown in FIG. 7, for example, the heating time is 60 minutes, the compression force is 1 kN, the binder ratio is 20%, and the height (original thickness) of the sponge media 10 is 50 mm. Under the conditions, the volume reduction rate of the sponge media 10 is obtained by changing the heating temperature. In such a case, when the heating temperature is about 80 ° C., the moisture in the binder does not evaporate sufficiently, so that it takes time to cure the sponge media 10 and the volume reduction rate does not improve. Then, as the heating temperature further rises, the volume reduction rate is improved, and the volume reduction rate is best at 20% from 100 ° C. or higher. Thereafter, if the heating temperature exceeds 120 ° C., a part of the sponge material urethane may be decomposed to generate harmful substances such as NOx. Therefore, the heating temperature range is set to 100 ° C. to 120 ° C.

  As for the heating time (minutes), as shown in FIG. 8, for example, the heating temperature is 100 ° C., the compression force is 1 kN, the binder ratio is 20%, the height (original thickness) of the sponge media 10 is 50 mm, Under certain conditions, the evaporation of moisture in the binder proceeds by heating, and the curing of the binder proceeds. Therefore, the curing is advanced enough to maintain the volume reduction rate at 20%. If the heating time exceeds 150 minutes, a part of the sponge material urethane may be decomposed to generate harmful substances such as NOx, so the heating time range is 50 minutes to 150 minutes. To do.

  Under the above conditions, the cylinder 3 is filled with sponge media 10 mixed with water-based urethane at a mass ratio of 5% to 20%, and as shown in FIG. While the inside of the cylinder 3 is set to a negative pressure from the outside of the furnace 2, the pressing device 8 is operated, the screw rod body 8b is rotated in a predetermined direction, and the elevating plate 8c is lowered. The load is confirmed with a load meter 7 and the amount of descent is confirmed with a displacement meter 7a.

  The elevating plate 8c is lowered, and the piston rod 5a is pushed down by the push rod 8a suspended thereby, and the sponge media 10 is pushed by the pistons 4a and 4b through the pushing jig 6 at about 1 kN. . Then, the compressed sponge media 10 in the cylinder 3 is heated by setting the heating temperature of the electric furnace 2 to 100 ° C. to 120 ° C. The heating time is 50 minutes to 150 minutes. Thereby, a lot of sponge media 10 can be packed in the cylinder 3. In addition, although it pressed by 1 kN in this apparatus, it cannot be overemphasized that a volume reduction rate will become smaller if it presses with a bigger load. Even in this case, the water-based urethane mass ratio, temperature, time conditions, and the like are almost the same.

  For example, if the volume reduction rate is 20% with respect to the original volume of the sponge media 10, the volume is compressed to 1/5. Thus, when the sponge media 10 is packed in a metal container and discarded, the packing is completed with a smaller number of metal containers than in the past. As a result, the number of steps for packing the sponge media 10 is reduced and the cost is reduced.

It is a front view which shows schematic structure of the sponge media volume reduction apparatus 1 which concerns on this invention. FIG. 4 is a perspective view (A) of pistons 4a and 4b and a perspective view (B) of a pushing jig 6 in the sponge media volume reducing device 1 of the present invention. It is a perspective view of the sponge media volume reduction apparatus 1 of the same invention. It is a characteristic curve figure which shows the relationship between the aperture ratio of a piston, and the volume reduction rate of sponge media. It is explanatory drawing which shows the method for reducing the sponge media according to the present invention. It is a characteristic curve figure which shows the relationship between a binder ratio and the volume reduction rate of sponge media. It is a characteristic curve figure which shows the relationship between heating temperature and the volume reduction rate of sponge media. It is a characteristic curve figure which shows the relationship between a heating time and the volume reduction rate of sponge media.

Explanation of symbols

1. Sponge media volume reduction method and device,
2 electric furnace,
3 cylinders,
4a, 4b piston, 4c through hole,
5a piston rod, 5b one end,
6 Pushing jig,
7 Load cell, 7a Displacement meter,
8 Pressing device, 8a Pushing rod,
8b screw rod body, 8c lifting plate,
9 Connecting members,
10 Sponge media,
11a Heat-resistant piping.

Claims (6)

When reducing the volume of the sponge media by compressing and heating the sponge media, add 5% to 20% by mass of water-based urethane to the mass of the sponge media, and reduce the volume by applying the required load. thing,
Sponge media volume reduction method characterized by. The heating temperature is 100 ° C. to 120 ° C.,
The method for reducing the volume of sponge media according to claim 1. Heating time is 50 minutes to 150 minutes,
The volume reduction method for sponge media according to claim 1 or 2. Sponge media is placed in a cylinder having a low and low cylindrical body, and when a load is applied to the sponge media with the piston for the cylinder, a through hole is provided in the piston, and the opening ratio by the through hole is 40% to 80%. %
The sponge media volume reduction method according to any one of claims 1 to 3. In the electric furnace, a cylinder having a low and low cylindrical body, a piston for the cylinder, and a part of a piston rod connected to the piston are provided, and one end of the piston rod is disposed at an upper portion of the electric furnace. It is projected upward from the provided through hole, and a load means and a displacement meter are connected to one end of the projecting piston rod.
Sponge media volume reduction device characterized by. One end of the heat-resistant piping of the vacuum device that creates a negative pressure in the cylinder is connected to the cylinder from the outside of the electric furnace,
The sponge media volume reducing device according to claim 5.

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