JP2012229984A - Activated concrete processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an activated concrete processing method capable of efficiently removing critical nuclide: Co and Eu from an activated concrete.SOLUTION: A method includes: a crushing process 2 for crushing the activated concrete 1; a first cleaning process 3 for soaking the crushed concrete S1 obtained in the crushing process 2 in a treatment liquid W1 to extract cobalt and europium contained in the crushed concrete S1; a solid-liquid separation process 4 for conducting a solid-liquid separation on the crushed concrete S2 and a treatment liquid W2 after the first cleaning process 3; and a recovery process 5 for recovering the cobalt and europium together with noncritical nuclide from the treatment liquid separated in the solid-liquid separation process 4. In the first cleaning process 3, the treatment liquid W1 is the nitric acid whose temperature is at 70°C or above and 150°C or below and the crushed concrete S1 is immersed in the treatment liquid W1 for 3 or more and 30 or less hours.

Description

  The present invention relates to a method for treating activated concrete, in which a determined nuclide is removed from activated concrete and the activated concrete is processed.

2. Description of the Related Art Conventionally, in a nuclear facility such as a nuclear power plant, a structural frame is constructed of concrete because it has sufficient strength and is excellent in radiation shielding.
And since the concrete of such nuclear facilities is exposed to radiation and activated, there is a need for storage management as radioactive waste when the facility is replaced (decommissioned).
For this reason, in recent years, the processing method of activation concrete has been proposed (for example, refer nonpatent literature 1).

By the way, although various elements are contained in concrete, the determinative nuclide to be activated is Co (cobalt) and Eu (europium). The concrete also contains nondeterminable nuclides such as Fe (iron) and Al (aluminum).
In the method for treating activated concrete of Non-Patent Document 1, the concrete is dissolved and heated with an acidic treatment liquid such as nitric acid, and the metals (Co, Eu, Fe, Al, etc.) extracted in the treatment liquid are recovered. Yes.

  In the process of recovering the metal in the processing liquid, an alkali is added to the processing liquid to neutralize it, and the precipitated metal is recovered as a hydroxide. Here, Fe, Al, etc. are precipitated as hydroxides when the treatment liquid is pH 3-5, and Co, Eu is precipitated as hydroxides when the treatment liquid is pH 7-8. The pH of the liquid is raised stepwise, Fe, Al, etc. are recovered at the pH 3-5 stage, and Co, Eu are recovered at the pH 7-8 stage.

“Development of the world's first radioactivity reduction technology for activated concrete”, [online], March 2, 2010, Shimizu Corporation, [Search on March 25, 2011], Internet <URL: http: // / Www. shimz. co. jp / news_release / 2010/770. html>

  However, in the method for treating activated concrete according to Non-Patent Document 1, when recovering non-determined nuclides such as Fe and Al, the determined nuclides Co and Eu are dissolved in the treatment liquid. There is a possibility that Co, Eu adheres to Al, etc. For this reason, it is necessary to wash or dehydrate the recovered Fe, Al, etc., and this work requires labor and cost.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for treating activated concrete that can efficiently remove Co and Eu, which are determined nuclides, from activated concrete.

  In order to achieve the above object, a method for treating activated concrete according to the present invention includes a pulverizing step of pulverizing activated concrete, and a determination that the pulverized product obtained in the pulverizing step is immersed in a treatment liquid and contained in the pulverized product. A first washing step for extracting nuclide cobalt and europium, a solid-liquid separation step for solid-liquid separation of the pulverized product and the treatment liquid after the first washing step, and a treatment liquid separated in the solid-liquid separation step In the first cleaning step, the treatment liquid is nitric acid of 70 ° C. or higher and 150 ° C. or lower, and the pulverized product is added to the treatment liquid for 30 hours or longer. It is characterized by soaking for less than an hour.

In the first cleaning step, the treatment liquid is nitric acid having a temperature of 70 ° C. or higher and 150 ° C. or lower. By immersing the pulverized material in the treatment liquid for 3 hours or longer and 30 hours or less, cobalt and europium contained in the pulverized material can be obtained. Stable extraction can be performed.
Also, in the recovery process, it is necessary to remove cobalt and europium adhering to nondetermined nuclides compared to the conventional method of separately recovering cobalt and europium and nondetermined nuclides from the treatment liquid separated in the solid-liquid separation process. Therefore, cobalt and europium can be reliably and efficiently recovered in a single process, and labor required for work can be reduced, thereby reducing costs.

In the method for treating activated concrete according to the present invention, the pulverized product obtained in the pulverization step is converted into a first pulverized product having a predetermined particle size and a second pulverized product having a predetermined particle size or less. A classification step for classification, and a second washing step for extracting cobalt and europium contained in the second pulverized product by immersing the second pulverized product obtained in the classification step in a treatment solution that is nitric acid. The first pulverized product obtained in the classification step is treated in the first washing step and the solid-liquid separation step, and the treatment liquid separated in the solid-liquid separation step and the treatment solution after the second washing step May be processed in the recovery step.
In the present invention, activated concrete is classified into a first pulverized product having a predetermined particle size and a second pulverized product having a predetermined particle size or less, and the second pulverized product is treated in the second washing step. As a result, the temperature of the treatment liquid can be lowered in the second washing step as compared to the first washing step, and the time for immersing the second pulverized product in the treatment liquid can be shortened.
In the recovery step, the treatment liquid separated in the solid-liquid separation step and the treatment liquid after the second washing step may be treated together, or separately, and cobalt and europium, which are determinable nuclides in the treatment liquid, are treated. It may be collected by precipitation.

In addition, the method for treating activated concrete according to the present invention includes an aggregate cement separation step of dividing the second pulverized product obtained in the classification step into aggregate and cement powder, and the aggregate or the It is preferable to process the aggregate and cement powder in the steps after the second washing step.
In the present invention, the first pulverized product is mainly an aggregate pulverized product, and the second pulverized product is divided into aggregate and cement powder, and thus the aggregate and cement powder are reused. In this case, it is not necessary to separate the aggregate and the cement powder after the treatment, and workability is good.
Further, for example, when the radiation dose of the cement powder is lower than a predetermined value, the second cleaning process and the recovery process may not be performed, and the labor required for the processing can be reduced.

In the method for treating activated concrete according to the present invention, the pulverized product obtained in the pulverization step may be classified according to particle size, and the first washing step may be performed for each of the pulverized product thus separated.
In the present invention, the pulverized product obtained in the pulverization step is classified according to particle size, and the first washing step is performed for each pulverized product, thereby immersing in the nitric acid temperature of the treatment liquid and nitric acid for each particle size. Therefore, there is no waste in the treatment time and nitric acid heat retention, the treatment time can be shortened, and the cost can be reduced.

  According to the present invention, it is possible to stably extract cobalt and europium contained in the pulverized activated concrete, and in the recovery process, cobalt and europium, non-determined nuclides, and the like from the treatment liquid separated by the solid-liquid separation process. Compared with the conventional method of separately recovering cobalt, there is no need to remove cobalt and europium adhering to non-determined nuclides, so cobalt and europium can be reliably and efficiently recovered in one step. The labor required for the work can be reduced and the cost can be reduced.

It is a flowchart which shows the processing method of the activated concrete by 1st embodiment of this invention. It is a flowchart which shows the processing method of the activated concrete by 2nd embodiment of this invention.

(First embodiment)
Hereinafter, the processing method of the activated concrete by embodiment of 1st invention is demonstrated based on FIG.
The method for treating activated concrete according to the first embodiment relates to a method for treating activated concrete generated as solid waste due to, for example, renovation or dismantling of a nuclear facility such as a nuclear power plant.

  As shown in FIG. 1, the method for treating activated concrete according to the first embodiment is obtained by pulverizing step 2 for pulverizing activated concrete (waste concrete lump) 1 generated in a nuclear facility or the like, and pulverizing step 2. First pulverized product S1 obtained by immersing the pulverized activated concrete S1 in the treatment liquid W1 to extract the metal components of the pulverized product S1 into the treatment liquid W1, and the pulverized product S2 and the treatment liquid after the first washing step 3 Solid-liquid separation step 4 for separating W2, recovery step 5 for recovering metal components from the treatment liquid W3 separated in the solid-liquid separation step 4, and drying step for drying the pulverized product S2 separated in the solid-liquid separation step 4 6 is provided.

(Crushing process 2)
First, in the pulverization step 2, the activated concrete 1 is pulverized to a particle size of 8 mm or less using a pulverizer. At this time, it is desirable to pulverize the activated concrete 1 in a flake form so that a pulverized product S1 having a surface area as large as possible can be obtained by using a pulverizer such as a roll crusher. At this time, it is confirmed with a sieve or the like that the particle size of the pulverized product S1 is 8 mm or less.
At this time, as long as the particle size of the pulverized material S1 is 8 mm or less, the respective particle sizes may be uneven.

(First cleaning step 3)
Subsequently, a first cleaning step 3 for cleaning the pulverized material S1 is performed.
In the first cleaning step 3, first, the pulverized product S1 is charged into the reaction layer, and the treatment liquid W1 is supplied to the reaction layer. Nitric acid is used for the treatment liquid W1. The concentration of nitric acid is 30% by weight or more and 70% by weight or less.
Then, the processing liquid W1 is kept at about 120 ° C., and the pulverized material S1 is immersed in the processing liquid W1 for about 24 hours. By immersing the pulverized material S1 in the processing liquid W1, the metal component contained in the pulverized material S1 is extracted into the processing liquid W1.
The metal components extracted into the treatment liquid W1 are determined nuclides such as Co (cobalt) and Eu (europium), and non-determined nuclides such as Fe (iron) and Al (aluminum).
The pulverized product from which the metal component has dissolved and removed after the first cleaning step 3 is referred to as pulverized product S2, and the processing liquid from which the metal component has been extracted is referred to as processing liquid W2.

(Solid-liquid separation step 4)
Then, the solid-liquid separation process 4 which isolate | separates the ground material S2 and the process liquid W2 after the 1st washing | cleaning process 3 is performed.
The pulverized product S2 and the treatment liquid W2 are easily separated into solid and liquid using a filter, screen, basket, or the like made of Teflon (registered trademark), and the pulverized product S2 that is a solid content is again subjected to the first washing step as necessary. 3 and the processing liquid W2 that is a liquid component is sent to the recovery step 5.
At this time, in the first washing step 3, the pulverized product S1 is placed in a Teflon (registered trademark) filter, screen, basket, or the like, soaked in the processing layer W1 of the reaction layer, and in the solid-liquid separation step 4, By removing the Teflon (registered trademark) filter, screen or basket from the reaction layer together with the pulverized product S2, the pulverized product S2 and the treatment liquid W2 can be separated.
In addition, you may reuse the process liquid W2 after the solid-liquid separation process 4 for the 1st washing | cleaning process 3 which makes object the other pulverized material S1. In this case, the recovery step 5 is performed on the processing liquid W2 that has been reused and separated again in the solid separation step 4.

(Recovery process 5)
Then, the collection process 5 which collects a metal component from the processing liquid W2 after the solid-liquid separation process 4 is performed.
In the recovery step 5, the determined nuclides Co and Eu are recovered together with non-determined nuclides such as Fe and Al.

In the recovery step 5, the strongly acidic treatment liquid W2 after the solid-liquid separation step 4 is neutralized with alkali such as aqueous ammonia or sodium hydroxide solution, or cement powder when concrete is crushed, and the pH value is 7 Process liquid W3 of ~ 8.
When the treatment liquid W2 becomes a weak acid region having a pH value of 3 to 5 at the stage of neutralization, non-determined nuclides such as Fe and Al become hydroxides and precipitate. Then, when the pH value of the treatment liquid W2 becomes 7 to 8, the determined nuclides Co and Eu become hydroxides and precipitate.

Then, the treatment liquid W3 having a pH value of 7 to 8 and the metal component precipitated is subjected to solid-liquid separation using a filter press, and the precipitated determined nuclides such as Co and Eu hydroxides and non-determined nuclides such as Fe and Al. Collect the hydroxide. These recovered hydroxides are sent to the metal component drying step 6 to be dried and then disposed as radioactive waste.
Further, the treatment liquid W3 that has become high-salt water is diluted and discharged.
In the case of solid-liquid separation, a centrifugal dehydrator or a multi-disc dehydrator may be used in addition to the filter press.

(Drying step 7)
Before and after the recovery step 5, the solid pulverized product S2 obtained in the solid-liquid separation step 4 is dried before being disposed as general waste, and a drying step 7 is performed.
The pulverized product S2 is dried with a dryer and adjusted to a predetermined moisture content or less. The radiation dose of the crushed material S3 after drying is measured to confirm that the determined nuclide has been reliably removed, and then the crushed material S3 is disposed of as general waste.
Note that when the pulverized material S2 is recycled, the drying step 7 may not be performed.

    Therefore, according to the activation concrete processing method of the first embodiment, in the first cleaning step 3, by using nitric acid as the processing liquid W1, stable extraction of the metal components contained in the pulverized material S1 is achieved. It can be carried out. Then, by immersing the pulverized product S1 in the treatment liquid W1, which is nitric acid kept at about 120 ° C., for 24 hours, the metal components contained in the pulverized product S1 are efficiently extracted, and each particle size of the pulverized product S1 is obtained. Can be processed all at once even if they are 8 mm or less and uneven.

    And in the collection process 5, compared with the conventional method which collect | recovers cobalt and europium, and a nondetermined nuclide separately from the process liquid W2 isolate | separated by the solid-liquid separation process, the operation | work which removes the cobalt and europium adhering to a nondetermined nuclide Therefore, cobalt and europium can be reliably and efficiently recovered in one recovery step 5, and the labor required for work can be reduced and the cost can be reduced.

(Second embodiment)
Next, another second embodiment will be described with reference to the accompanying drawings, but the same or similar members and parts as those of the above-described first embodiment will be denoted by the same reference numerals, and description thereof will be omitted. A configuration different from that of the first embodiment will be described.

(Classification process 11)
As shown in FIG. 2, in the activated concrete processing method according to the second embodiment, after the pulverization step 2, the pulverized product S1 obtained in the pulverization step 2 is reduced to a particle size of 0.5 mm using a sieve or the like. A classification step 11 is performed in which the pulverized product (first pulverized product) Sa and the finely pulverized product (second pulverized product) Sb having a particle size of 0.5 mm or less are classified. At this time, the pulverized product Sa is a pulverized product of the aggregate of the activated concrete 1, and the finely pulverized product Sb is the fine powder Sc and the cement powder Sd of the aggregate of the activated concrete 1.
And the 1st washing | cleaning process 3 and the solid-liquid separation process 4 are performed to the ground material Sa similarly to ground material S1 of 1st embodiment.
In the present embodiment, the pulverized product Sa and the finely pulverized product Sb are classified with a particle size of 0.5 mm as a boundary, but the boundary value of the classified particle size may be other than 0.5 mm. At this time, the boundary value of the particle size to be classified is a value at which the pulverized material Sa does not fall out from the eyes of a filter, a screen or a basket made of Teflon (registered trademark) used in the solid-liquid separation step 4 performed later. It is preferable to do.

(Aggregate cement separation process 12)
An aggregate cement separation step 12 is performed for separating the finely pulverized product Sb into aggregate fine powder Sc and cement powder Sd.
In the aggregate cement separation step 12, for example, the finely pulverized product Sb is separated into an aggregate fine powder Sc and a cement powder Sd using a cyclone.

The cyclone separates the powder by utilizing the difference in particle density between the fine powder Sc and the cement powder Sd of the aggregate, and the particles having a high density are formed on the inner peripheral surface side by the spiral airflow in the inverted conical cyclone. In addition, particles having a low density gather on the center side. Then, a downflow having an inverted conical shape is formed on the inner peripheral surface side in the cyclone, and an upflow is formed in the central portion in a corresponding manner, so that the aggregate fine powder Sc and the cement powder Sd Separation can be performed.
The aggregate fine powder Sc thus separated is processed in a process described later, and the cement powder Sd is disposed of as general waste as it is or recycled.

(Second cleaning step 13)
Before and after the first washing step 3 and the first solid-liquid separation step 4, a second washing step 13 for washing the aggregate fine powder Sc obtained in the aggregate cement separation step 12 is performed. Hereinafter, the fine powder Sc of the aggregate will be described as a finely pulverized product Sc.
In the second cleaning step 13, first, the finely pulverized product Sc is charged into the reaction layer, and the processing liquid W6 is supplied to the reaction layer. Nitric acid is used for the treatment liquid W6 in the same manner as the treatment liquid W1 used in the first cleaning step 3. The concentration of nitric acid is 30% by weight or more and 70% by weight or less.

Then, the processing liquid W6 is kept at a temperature of about 100 ° C., and the finely pulverized material Sc is immersed in the processing liquid W6 for about 24 hours. By immersing the finely pulverized material Sc in the treatment liquid W6, the metal component contained in the finely pulverized material Sc is extracted into the treatment liquid W1.
The finely pulverized product from which the metal component is dissolved and removed after the second cleaning step 13 is referred to as a finely pulverized product S6, and the processing liquid from which the metal component is extracted is referred to as a processing liquid W7.
In the second cleaning step 13, the processing liquid W2 separated in the solid-liquid separation step 4 may be reused instead of the processing liquid W6. In this case, the processing can be performed using the residual heat of the processing liquid W2. Further, the time for immersing the finely pulverized material Sc in the processing liquid W6 may be set as appropriate.

Subsequently, the treatment liquid W7 separated from the pulverized material S2 in the first solid-liquid separation step 4 and the treatment liquid W7 mixed with the finely pulverized material S6 after the second cleaning step 13 are processed in the recovery process 5 and subsequent steps. As in the first embodiment, the determined nuclides Co and Eu are collected together with the non-determined nuclides. At this time, the processing liquid W2 and the processing liquid W7 mixed with the finely pulverized material S6 are processed together.
The finely pulverized product S6 is separated from the treatment liquid W3 together with the hydroxide precipitated in the treatment liquid W3 by solid-liquid separation using a filter press performed in the recovery step 5. Thereafter, it is disposed as radioactive waste through the metal component drying step 6.
Further, the pulverized product S2 separated in the solid-liquid separation step 4 is sent to the drying step 7 as in the first embodiment, and becomes a pulverized product S3 in a form that can be recycled or treated as general waste.

In the activated concrete processing method according to the second embodiment, the activated concrete 1 is separated and processed into the aggregate pulverized material Sa, the aggregate pulverized material Sc, and the cement powder Sd. When cement and cement powder Sd are reused, it is not necessary to separate them after processing, and the work is easy to perform.
Further, the activated concrete 1 is separated into an aggregate pulverized product Sa, an aggregate pulverized product Sc, and a cement powder Sd, and then processed in the second cleaning step 13 for processing the pulverized product Sc. The temperature of the treatment liquid W1 can be lowered as compared with the first cleaning step 3 for treating the material Sa, and the time for immersing the cement powder Sb in the treatment liquid W1 can be shortened.

As mentioned above, although embodiment of the processing method of activation concrete concerning this invention was described, this invention is not limited to said embodiment, It can change suitably in the range which does not deviate from the meaning.
For example, in the above-described embodiment, the pulverized product S1 is immersed in the processing liquid W1 at about 120 ° C. for about 24 hours in the first cleaning step 3, but the temperature of the processing liquid W1 is 70 ° C. or higher and 150 ° C. or lower. The time for dipping the pulverized material S1 may be 3 hours or more and 30 hours or less. Further, in the first cleaning step 3, the treatment liquid W1 may be stirred in order to promote elution of the metal component.
In the above-described embodiment, in the second cleaning step 13, the finely pulverized product Sc is immersed in the processing liquid W6 at about 100 ° C. for about 24 hours, but the temperature of the processing liquid W6 is 70 ° C. or higher and 150 ° C. The time for dipping the finely pulverized material Sc may be 3 hours or longer and 30 hours or shorter.
Further, in the second cleaning step 13, the treatment liquid W6 may be stirred in order to promote the elution of the metal component.

In the above-described embodiment, the pulverized product S1 obtained in the pulverization step 2 has a particle size of 8 mm or less, and the particle sizes thereof are not uniform. Alternatively, the first cleaning step 3 may be performed, and the temperature of the treatment liquid W1 and the time for immersing the pulverized material S1 in the first cleaning step 3 may be set. For example, the pulverized product S1 is classified using sieves having a sieve size of 8 mm, 5.6 mm, 3 mm, and 1 mm, and the temperature of the treatment liquid is set to 70 ° C. or more and 150 ° C. or less for each particle size. You may set suitably in 3 hours or more and 30 hours or less.
Further, when the first cleaning step 3 is performed for each particle size of the pulverized product S1, the first cleaning step 3 of the pulverized product S1 having a relatively large particle size is performed with the high-temperature treatment liquid W1, and then this process is performed. You may perform the 1st washing | cleaning process 3 of the ground material S1 with a comparatively small particle size using the residual heat of the liquid W1.

In the second embodiment described above, the finely pulverized product Sb having a particle size of 0.5 mm or less obtained in the classification step 11 is used as the aggregate pulverized product Sc and the cement powder Sd in the aggregate cement separation step 12. The cement powder Sd is disposed of as general waste or recycled as it is, but depending on the radiation amount contained in the cement powder Sd, the cement powder Sd is similar to the finely pulverized material Sc of the aggregate. Alternatively, the second cleaning step 13 and subsequent steps may be used. Further, the finely pulverized product Sb obtained in the classification step 11 may be processed in the steps after the second washing step 13 without performing the aggregate cement separation step 12.
In the second embodiment described above, the processing liquid W7 after the second cleaning step 13 and the finely pulverized product S6 are processed in the recovery step 5 without being separated, but the processing liquid W7 and the finely pulverized product are processed. S6 may be separated, and only the processing liquid W7 may be processed in the recovery step 5, and the finely pulverized product S6 may be dried and disposed of as general waste or recycled. In addition, when recycling finely pulverized material S6, it is not necessary to perform a drying process.
In the above-described second embodiment, the processing liquid W2 and the processing liquid W7 are processed together in the recovery step 5, but may be processed separately. In that case, the recovery process 5 may be performed on each of the processing liquid W2 and the processing liquid W7.

1 Activated concrete (waste concrete block)
2 Crushing Step 3 First Washing Step 4 Solid-Liquid Separation Step 5 Recovery Step 11 Classification Step 12 Aggregate Cement Separation Step 13 Second Washing Step S1, S2, S3 Ground Product Sa Ground Product (First Ground Product)
Sb, Sc Finely pulverized product (second pulverized product)
W1, W2, W6, W7 Treatment liquid (nitric acid)
W3 treatment liquid

Claims (4)

A crushing process for crushing the activated concrete;
A first washing step of immersing the pulverized product obtained in the pulverizing step in a treatment liquid and extracting cobalt and europium of the determined nuclides contained in the pulverized product;
A solid-liquid separation step for solid-liquid separation of the pulverized product and the treatment liquid after the first washing step;
A recovery step of recovering cobalt and europium together with non-determined nuclides from the treatment liquid separated in the solid-liquid separation step;
In the first cleaning step, the treatment liquid is nitric acid at 70 ° C. or more and 150 ° C. or less, and the pulverized material is immersed in the treatment liquid for 3 hours or more and 30 hours or less. A classification step of classifying the pulverized product obtained in the pulverization step into a first pulverized product having a predetermined particle size and a second pulverized product having a predetermined particle size or less;
A second washing step of extracting the cobalt and europium contained in the second pulverized product by immersing the second pulverized product obtained in the classification step in a treatment solution that is nitric acid,
The first pulverized product obtained in the classification step is treated in the first washing step and the solid-liquid separation step, and the treatment liquid separated in the solid-liquid separation step and the treatment liquid after the second washing step are obtained. The method for treating activated concrete according to claim 1, wherein the treatment is performed in the collecting step.   An aggregate cement separation step of dividing the second pulverized product obtained in the classification step into an aggregate and cement powder, the aggregate, or the aggregate and cement powder after the second washing step The method for treating activated concrete according to claim 2, wherein the treatment is performed in a process. The activated concrete according to any one of claims 1 to 3, wherein the pulverized product obtained in the pulverization step is classified according to particle size, and the first washing step is performed for each of the pulverized product thus separated. Processing method.

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