JP2006064561A - Execution method of activated concrete cutting work - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an execution method of an activated concrete cutting work capable of reducing the amount of a radiation discharged into the sea or the like as the whole work, and having less effect on the general public. <P>SOLUTION: This execution method of the activated concrete cutting work has a wet cutting process S1 for cutting the activated concrete, while injecting cooling water into a cutting part; a solid/liquid separation treatment process S2 for separating cutting waste liquid 1 including activated concrete sludge generated at the wet cutting process S1 time into a solid portion 3 including a radioactive material and a filtrate 2 wherein the radioactive material is dissolved; and a neutralization treatment process S3 for neutralizing the filtrate 2 into a neutralized filtrate 4. In the method, the filtrate 2 generated in the solid/liquid separation treatment process S2 is used as the cooling water at the wet cutting process S1 time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for constructing activated concrete cutting work for cutting activated concrete and removing radioactive substances from a cutting waste liquid containing activated concrete sludge.

  When demolishing a concrete structure, a wire saw cutting method is often used. In the dismantling work using the wire saw cutting method, water is used as a coolant during cutting, so that a slurry-like cutting waste liquid in which concrete sludge and water are mixed is generated. In the dismantling work of a general concrete structure, the cutting waste liquid is discharged into rivers and oceans after processing suspended matter (SS), hydrogen ion concentration (pH) and the like in accordance with general environmental discharge standards.

  When dismantling a concrete structure of a facility that handles radioactive substances such as nuclear power plants, since the concrete has been activated, radioactive waste is contained in the cutting waste liquid generated in the cutting operation. The radioactive substances in the cutting waste liquid include particulate nuclides (particulate nuclides) present in large quantities and nuclides dissolved in water (soluble nuclides). Therefore, the cutting waste liquid generated in the cutting operation must be discharged after performing a predetermined treatment after removing the radioactive substance.

  On the other hand, facilities for treating radioactive liquid waste are usually installed in nuclear facilities (see, for example, Patent Document 1). This can remove radioactive substances in the waste liquid, but the waste liquid from cutting concrete is significantly different from the waste liquid generated during facility operation and is produced in a larger amount than the waste liquid generated during facility operation. Therefore, it is difficult to treat the cutting waste liquid with the above equipment.

Conventionally, a method has been proposed for treating cutting waste liquid generated when activated concrete is cut. In this method, first, a solid-liquid separation process (dehydration process) is performed by removing the solid content of the cutting waste liquid using a filter press to obtain a filtrate, and then the filtrate from which the solid content has been removed by the solid-liquid separation process. This is a method of performing a neutralizing treatment step (for example, see Patent Document 2). According to this method, after the solid-liquid separation process to remove the solid content of the waste liquid to obtain a filtrate, the neutralization process for lowering the pH of the filtrate is performed, so that the radioactive substance (particulate nuclides) in the cutting waste liquid is not dissolved. ) As solids. And it can be made the property which does not have a bad influence on a general environment by neutralizing the filtrate from which the radioactive substance was fully removed.
Japanese Patent Laid-Open No. 9-230095 JP 2002-333696 A

  However, when the cutting waste liquid is processed by the above-described conventional processing method, particulate nuclides present in a large amount in the cutting waste liquid can be removed by 99.99% or more, but the soluble nuclides dissolved in water Only about 15% can be removed and it remains in the filtrate after the treatment. In the construction method of activated concrete cutting work with the conventional treatment method, even if the radioactive concentration of the filtrate discharged to the ocean etc. is very small, if a large amount of cutting waste liquid is generated throughout the construction, it will be released to the ocean etc. There is a problem that the total amount of radioactivity produced increases. Therefore, in the case of large-scale construction using a large amount of cooling water, the total amount of radioactivity released to the ocean or the like increases, which may affect the general public.

  The present invention takes the above-mentioned conventional problems into consideration, and reduces the amount of radioactivity released to the ocean as a whole construction, and the construction of activated concrete cutting work that can reduce the impact on the general public It aims to provide a method.

  The invention described in claim 1 includes a wet cutting step of cutting activated concrete while injecting cooling water into a cut portion, and a cutting waste liquid containing activated concrete sludge generated during the wet cutting step, and a solid content containing a radioactive substance. And a solid-liquid separation treatment step for separating the radioactive substance into a filtrate, and a neutralization treatment step for neutralizing the filtrate into a neutralized filtrate. The filtrate produced in the separation treatment step is used again as cooling water in the wet cutting step.

  Due to these characteristics, by reusing the filtrate as cooling water, the filtrate in which the radioactive substance is dissolved is in a state (saturated state) in which a certain amount of radioactive substance is dissolved and no longer dissolves (saturated state). Even if the wet cutting process is performed using the filtrate as cooling water, the radioactive substance is not dissolved in the filtrate. Further, since the filtrate is reused as cooling water, the neutralized filtrate that is neutralized and finally discharged becomes a small amount as a whole of the activated concrete cutting work.

  According to the method for cutting activated concrete according to the present invention, by reusing the filtrate as cooling water, the filtrate in which the radioactive material is dissolved becomes saturated and the radioactive material is dissolved in the wet cutting process. The neutralized filtrate that is neutralized and eventually discharged becomes a small amount of the activated concrete cutting work as a whole, so the radioactive concentration of the filtrate (neutralized filtrate) increases, but the discharged radiation The total amount of performance can be reduced. As a result, it is possible to reduce the influence on the general public due to the activation concrete cutting work.

  Hereinafter, an embodiment of a construction method of activation concrete cutting work according to the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing an embodiment of the waste liquid treatment method of the present invention, FIG. 2 is a schematic view of a filter press apparatus used in dehydration treatment, and FIG. 3 is a block diagram of a neutralization apparatus used in neutralization treatment.

  As shown in FIG. 1, the activation concrete cutting construction method includes a wet cutting step S1 for cutting the activated concrete while injecting cooling water into the cut portion, and an activated concrete sludge generated during the wet cutting step S1. A solid-liquid separation process (dehydration process) step S2 for separating the cutting waste liquid 1 into a solid content 3 containing a radioactive substance and a filtrate 2 in which the radioactive substance is dissolved, and neutralizing the filtrate 2 into a neutralized filtrate 4 And neutralizing treatment step S3.

  First, in the wet cutting step S1, the activated concrete is cut by a generally known wire saw cutting method. The cooling water initially poured into the cut portion is fresh water 5, and the clean water 5 and concrete sludge generated during cutting are mixed to produce slurry-like cutting waste liquid 1. The concrete sludge generated at the time of cutting contains a radioactive substance. The cutting waste liquid 1 containing this concrete sludge contains a radioactive substance, has a high solid content, and dissolves calcium hydroxide contained in cement. High pH due to influence.

  Next, in the solid-liquid separation processing step S <b> 2, the cutting waste liquid 1 is dehydrated by the filter press device 10 (see FIG. 2) and separated into the solid content 3 and the filtrate 2. As shown in FIG. 2, the filter press device 10 is provided between the clamping plate 11, the receiving plate 12 provided at a position facing the clamping plate 11, and the clamping plate 11 and the receiving plate 12. A plurality of filter plates 13. The fastening plate 11 is provided so as to be able to advance and retreat with respect to the receiving plate 12. A filter chamber 14 is formed between the filter plates 13, and a flow path 15 through which the cutting waste liquid 1 passes is provided so as to pass through the respective centers of the filter plates 13. Further, the filter plates 13 are connected by a connecting member 16.

In order to separate the cutting waste liquid 1 into the solid content 3 and the moisture 2 using the filter press device 10, as shown in FIG. 2 (a), the fastening plate 11 and the receiving plate 12 are brought close to each other, and a plurality of filtrations are performed. While tightening the plates 13, the cutting waste liquid 1 is pumped to the filter chamber 14 through the flow path 15.
Then, the concrete sludge contained in the cutting waste liquid 1 is collected on the filter cloth as the solid content 3. On the other hand, the moisture of the cutting waste liquid 1 is discharged out of the filter chamber 14 as the filtrate 2. Thus, the cutting waste liquid 1 is separated into the solid content 3 and the filtrate 2. As shown in FIG. 2B, the solid content 3 in the filter chamber 14 is discharged by separating the fastening plate 11 and the receiving plate 12 and opening the filter chamber 14. At this time, the solid content 3 can be easily handled.

  Among the radioactive substances contained in the cutting waste liquid 1, the particulate nuclides are contained in the solid content 3 separated using the filter press device 10, and therefore the radioactive substance dissolved in water is contained in the filtrate 2. Only (soluble nuclides) remain.

  Next, the above-described wet cutting step S1 is performed using the filtrate 2 generated in the above-described solid-liquid separation treatment step S2 as cooling water. Specifically, the filtrate 2 discharged to the outside of the filter chamber 14 is guided to the cut portion, and the activated concrete is continuously cut while pouring the filtrate 2 into the cut portion. At this time, a small amount of fresh water is added to the filtrate 2 poured into the cut portion in order to supplement the loss due to the soaking into the activated concrete. Of course, it is not necessary to add fresh water if the amount of loss is very small.

Next, a solid-liquid separation processing step S2 is performed in which the cutting waste liquid 1 generated in the wet cutting step S1 using the filtrate 2 as cooling water is separated into the solid content 3 and the filtrate 2 by the filter press device 10.
Thus, the above-described steps are repeated, and the activated concrete is cut by reusing the filtrate 2. At this time, by repeating the reuse of the filtrate 2, the filtrate 2 containing the soluble nuclide becomes saturated.

  Here, the test data which can confirm that the filtrate 2 containing a soluble nuclide will be in a saturated state will be described. FIG. 4 is a graph showing an example of the relationship between the solid content concentration and the radioactivity concentration of the cutting waste liquid containing the soluble nuclide C-14 (carbon 14) and the filtrate. As shown in FIG. 4, the cutting waste liquid before the solid-liquid separation (dehydration) step S2 increases the radioactivity concentration as the solid concentration increases, but the solid-liquid separation is performed on the cutting waste liquid of each solid concentration. When processing step S2 is performed, the radioactivity concentration of the separated filtrate is hardly changed. According to this test data, when a certain amount of radioactive material dissolves, the soluble nuclide-derived substances (carbonates, carbon dioxide, etc.) cannot be completely dissolved in water and become saturated. Considered to have been removed. Therefore, when the saturated filtrate 2 is used as cooling water, the radioactive substance is not dissolved in the saturated filtrate 2.

  Next, after the activated concrete has been cut, a neutralization treatment step S3 is performed. In the neutralization treatment step S3, the filtrate 2 produced by the solid-liquid separation treatment step S2 using the filter press device 10 is neutralized by a neutralization device 20 as shown in FIG. Specifically, the filtrate 2 having a high pH due to the influence of calcium hydroxide elution contained in the cement is neutralized using carbon dioxide gas. The neutralization device 20 includes a line mixer 21, a pump 22 that sends the filtrate 2 to the mixer 21, and a carbon dioxide supply device 23 that pumps carbon dioxide to the mixer 21. In the present embodiment, the carbon dioxide supply device 23 is a carbon dioxide cylinder. In the mixer 21, the filtrate 2 is neutralized by mixing the filtrate 2 and a large amount of carbon dioxide gas.

  By neutralizing the filtrate 2 using carbon dioxide gas, the neutralized filtrate 4 is obtained to such an extent that the pH does not adversely affect the general environment (in the range of the marine discharge reference value pH 5.0 to 9.0). Further, in the normal neutralization treatment using carbon dioxide gas, dissolved calcium in the filtrate 2 reacts with the carbon dioxide gas to generate calcium carbonate precipitates and increase floating substances. However, as in this embodiment, the filtrate 2 And a large amount (predetermined amount or more) of carbon dioxide gas is forcibly mixed and reacted with the line mixer 21 to re-dissolve calcium carbonate as calcium bicarbonate, and the suspended solids can be reduced to about 100 mg / liter, Satisfies the standard value of 200 mg / liter for release into the general environment.

  Thus, the neutralized filtrate 4 treated through the solid-liquid separation treatment step S2 and the neutralization treatment step S3 has the suspended matter (SS) below the reference value, the hydrogen ion concentration (pH) below the reference value, And after reducing the amount of radioactivity, it is discharged into the general environment (the ocean etc.).

Here, as in the conventional construction method, the case where the wet cutting step S1 is performed by continuously pouring the fresh water 5 from the beginning to the end, and the fresh water 5 is initially used as in the construction method according to the above-described invention. The case where water is poured into the cutting portion and then the wet cutting step S1 is performed by reusing the filtrate 2 is compared.
FIG. 5 is an example in which the conventional construction method and the construction method according to the present invention are compared with respect to the radioactivity concentration of the neutralized filtrate 4 to be discharged, the amount of the neutralized filtrate 4 to be discharged, and the amount of radioactivity to be discharged. It is a table | surface which shows. As shown in FIG. 5, in the construction method of the present invention, the radioactive concentration of the neutralized filtrate 4 finally discharged is increased by about 4 times compared to the conventional construction method, but the neutralized filtrate 4 discharged is discharged. As a result, the amount of radioactivity released is about one-half that of the conventional method. From this result, it can be confirmed that in the construction method according to the present invention, more radioactive substances were removed than in the conventional construction method.

  According to the construction method of the activated concrete cutting construction having the above-described configuration, the filtrate 2 in which the radioactive substance is dissolved becomes saturated as shown in FIG. 4 by reusing the filtrate 2 as cooling water. As a result, the radioactive material does not dissolve during the wet cutting process, and the neutralized filtrate 4 that is neutralized and finally discharged becomes a small amount as a whole of the activated concrete cutting work. For this reason, as shown in FIG. 5, although the radioactive concentration of the filtrate 2 (neutralized filtrate 4) increases, the whole quantity of the released radioactivity can be decreased. As a result, it is possible to reduce the influence on the general public due to the activation concrete cutting work.

  As mentioned above, although embodiment of the construction method of the activation concrete cutting construction concerning this invention was described, this invention is not limited to above-described embodiment, In the range which does not deviate from the meaning, it can change suitably. is there. For example, in the above-described embodiment, the filter press apparatus 10 is used when the cutting waste liquid 1 is separated from the filtrate 2 and the solid content 3, but the water and solid content of the waste liquid containing sludge are sufficiently separated. Any device is possible. On the other hand, by using the filter press device 10, high solid-liquid separation performance can be obtained, and handling of the solid content after the dehydration treatment can be facilitated.

  In the embodiment described above, carbon dioxide gas is used in the neutralization step S3. However, other acids such as hydrochloric acid and sulfuric acid may be used in the present invention. However, carbon dioxide gas is safer than when hydrochloric acid / sulfuric acid is used, and moreover, corrosive gas is produced when hydrochloric acid is used for neutralization, and precipitates that do not dissolve when sulfuric acid is used. Since the amount of suspended solids may increase due to the generation of carbon dioxide, the amount added must be controlled. However, with carbon dioxide, if you add more than the prescribed amount (the amount necessary to convert dissolved calcium to calcium bicarbonate) Since the addition amount management is often very easy, work efficiency can be improved.

It is a flowchart figure for demonstrating embodiment of the construction method of the activated concrete cutting construction which concerns on this invention. It is a figure which shows the apparatus which performs the solid-liquid separation process for demonstrating embodiment of the construction method of the activation concrete cutting construction which concerns on this invention. It is a block diagram which shows the apparatus which performs the neutralization process process for describing embodiment of the construction method of the activation concrete cutting construction which concerns on this invention. It is a graph showing the relationship between solid content concentration and radioactivity concentration for demonstrating embodiment of the construction method of the activation concrete cutting construction which concerns on this invention. It is the table | surface which compared the construction method which concerns on embodiment of the construction method of the activation concrete cutting construction which concerns on this invention, and the conventional construction method.

Explanation of symbols

1 Cutting waste liquid 2 Filtrate 3 Solid content 4 Neutralized filtrate S1 Wet cutting process S2 Solid-liquid separation process S3 Neutralization process

Claims (1)

A wet cutting step of cutting the activated concrete while injecting cooling water into the cutting part;
A solid-liquid separation treatment step for separating cutting waste liquid containing activated concrete sludge generated during the wet cutting step into a solid content containing a radioactive substance and a filtrate in which the radioactive substance is dissolved;
In the construction method of the activated concrete cutting work comprising a neutralization treatment step to neutralize the filtrate to neutralize the filtrate,
An activation method for activated concrete cutting work, wherein the filtrate produced by the solid-liquid separation process is used as cooling water in a wet cutting process.

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