Radioactive waste processing method and dio-polymer solidified body

Abstract

To provide a radioactive waste processing method that can efficiently and properly process radioactive waste, and to provide a dio-polymer solidified body including the radioactive waste.SOLUTION: A radioactive waste processing method has: a crush step of crushing contamination concrete contaminated by 14CO2; a heating step of heating the crushed contamination concrete; a capturing step of capturing 14CO2 gas generating by the heating of the contamination concrete by an alkali solution, in which the 14CO2 gas turns into the alkali solution; a separation step of performing knead-processing of the heated contamination concrete to separate the knead-processed contamination concrete into coarse aggregate and a fine powder of mortar; and a solidification step of mixing the alkali solution including the 14CO2 gas, the fine powder, a fly ash and blast furnace slag to thereby produce a dio-polymer, and solidifying the dio-polymer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for treating radioactive waste generated during volume reduction of concrete, and to a geopolymer solidified material containing radioactive waste. [Background technology]

[0002] In nuclear power plants, radioactive carbon ( 14 C) was generated and generated 14 C is radioactive carbon dioxide ( 14 CO 2 ) exists. 14 CO 2 Although the radioactive materials are absorbed by the concrete of the reactor building of a nuclear power plant, the gaseous materials are free to move and cause contamination over a wide area. 14 CO 2 Radioactive waste from nuclear power plants is voluminous, but reducing its volume would make it possible to secure storage space and reduce costs.

[0003] 2. Description of the Related Art Conventionally, a method for treating radioactive waste is known, for example, as disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-227493 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, until now there has been no efficient and suitable method for disposing of radioactive waste.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a method for treating radioactive waste that can efficiently and appropriately treat radioactive waste, and a solidified material of geopolymer containing radioactive waste. [Means for solving the problem]

[0007] The present invention has the following aspects. [1] 14 CO 2 a crushing step of crushing the contaminated concrete; A heating step of heating the crushed contaminated concrete; The above-mentioned contaminated concrete was heated. 14 CO 2 The gas is captured with an alkaline solution, 14 CO 2 a capturing step of converting the gas into an alkaline solution; a separation step of grinding the heated contaminated concrete to separate it into coarse aggregate and fine mortar powder; The above 14 CO 2 A method for treating radioactive waste, comprising: kneading an alkaline solution containing gas, the fine powder, fly ash, and blast furnace slag to form a geopolymer; and solidifying the geopolymer. [2] The method for treating radioactive waste described in [1], wherein the temperature to which the contaminated concrete is heated in the heating step is 300°C or higher and 400°C or lower. [3] The method for treating radioactive waste according to [1] or [2], wherein the alkaline solution is an aqueous solution of sodium hydroxide at a concentration of 1 mol / L or more. [4] A geopolymer solidification product containing alkali carbonate, finely divided mortar powder obtained from contaminated concrete, fly ash, and blast furnace slag. Effect of the Invention

[0008] According to the present invention, it is possible to provide a method for treating radioactive waste that can efficiently and appropriately treat radioactive waste, and a solidified material of a geopolymer containing radioactive waste. [Brief description of the drawings]

[0009] [Figure 1] 1 is a flowchart showing a method for treating radioactive waste according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of a method for treating radioactive waste and a geopolymer solidified product according to one embodiment of the present invention will be described. It should be noted that the present embodiment is specifically described to allow a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[0011] [Radioactive waste disposal methods] The method for treating radioactive waste according to the present embodiment includes the steps of: 14 CO 2 A crushing step of crushing the contaminated concrete contaminated by the above-mentioned contaminated concrete, a heating step of heating the crushed contaminated concrete, and 14 CO 2 The gas is captured with an alkaline solution, 14 CO 2 A collection step of converting the gas into an alkaline solution, a separation step of grinding the heated contaminated concrete to separate it into coarse aggregate and fine mortar powder, and 14 CO 2 The method includes a solidification process in which an alkaline solution containing gas, the fine powder, fly ash, and blast furnace slag are mixed together to form a geopolymer, and the geopolymer is solidified.

[0012] FIG. 1 is a flow chart showing the radioactive waste treatment method of this embodiment. The radioactive waste treatment method of this embodiment will be described with reference to FIG.

[0013] "Crushing process" In the crushing process, radioactive material generated in the reactor is 14 CO 2The contaminated concrete is crushed (S1 in Figure 1). Contaminated concrete may be 14 CO 2 The radioactive materials have penetrated deep into the concrete. In some places, they have penetrated to a depth of several tens of millimeters. In decontamination of such contaminated concrete, the surface layer of the contaminated concrete is removed to a thickness of at least several tens of millimeters, and this removed part is treated as radioactive waste. The method for crushing the contaminated concrete is not particularly limited, but may be, for example, a method for removing the surface layer of the contaminated concrete by grinding.

[0014] The particle size of the contaminated concrete after crushing is preferably 10 mm to 80 mm, more preferably 10 mm to 60 mm, and even more preferably 10 mm to 40 mm. If the particle size of the contaminated concrete after crushing is equal to or greater than the lower limit, the contaminated concrete can be efficiently ground in the separation step described below. If the particle size of the contaminated concrete after crushing is equal to or less than the upper limit, the contaminated concrete can be efficiently ground in the heating step described below. 14 CO 2 Gas can be generated.

[0015] "Heating process" In the heating process, the contaminated concrete crushed in the crushing process is heated (S2 shown in Figure 1). By heating the contaminated concrete prior to the grinding treatment in the separation step, the efficiency of separating the contaminated concrete into coarse aggregate and fine mortar powder during the grinding treatment can be improved.

[0016] The temperature to which the contaminated concrete is heated is preferably 250° C. or higher and 400° C. or lower, more preferably 280° C. or higher and 370° C. or lower, and even more preferably 300° C. or higher and 350° C. or lower. If the temperature to which the contaminated concrete is heated is equal to or higher than the lower limit, a large amount of 14 CO 2When the temperature at which the contaminated concrete is heated is equal to or lower than the upper limit, the strength of the contaminated concrete is reduced by heating, and the efficiency of grinding is improved.

[0017] By heating the contaminated concrete, 14 CO 2 Gas is generated.

[0018] "Collection process" In the collection process, the contaminated concrete was heated in the heating process. 14 CO 2 The gas is captured with an alkaline solution, 14 CO 2 The gas is treated as an alkaline solution (S3 shown in FIG. 1).

[0019] The alkaline solution is preferably an aqueous sodium hydroxide solution having a concentration of 1 mol / L or more. When the concentration of the aqueous sodium hydroxide solution is 1 mol / L or more, 14 CO 2 For example, 1 mol / L of sodium hydroxide solution at 25°C will collect 12.3 L of gas per 1 L of solution. 14 CO 2 CO containing 2 The gas can be collected.

[0020] "Separation process" In the separation process, the contaminated concrete heated in the heating process is ground to separate it into coarse aggregate and fine mortar powder (S4 in Figure 1). 14 CO 2 It is known that gas penetrates the mortar portion of concrete, so contamination is observed in the mortar portion, but not in the coarse aggregate. In the separation process, the contaminated concrete is separated into coarse aggregate and fine mortar powder, with the coarse aggregate becoming non-radioactive waste and the fine mortar powder becoming radioactive waste. In other words, by subjecting the contaminated concrete to a grinding process, the contaminated concrete can be separated into coarse aggregate and fine mortar powder, and the volume of radioactive waste can be reduced. In particular, by heating the contaminated concrete,14 CO 2 After generating the gas, the contaminated concrete can be ground to reduce the volume of fine mortar powder that becomes radioactive waste.

[0021] The grinding process can be carried out, for example, in accordance with the method described in JP 2017-227493 A.

[0022] The particle size of the fine powder of the mortar obtained by the grinding process is preferably 0.15 mm to 5 mm, more preferably 0.15 mm to 4 mm, and even more preferably 0.15 mm to 3 mm. If the particle size of the fine powder is above the lower limit, not much energy is required when kneading with the alkaline solution, fly ash, and blast furnace slag, as described below. If the particle size of the fine powder is below the upper limit, the fine powder can be sufficiently mixed with these raw materials when kneading with the alkaline solution, fly ash, and blast furnace slag, as described below.

[0023] The coarse aggregate obtained in the separation process becomes non-radioactive waste. The non-radioactive waste coarse aggregate is reused.

[0024] "Solidification process" In the solidification process, the sintered matter obtained in the collection process is 14 CO 2 The alkaline solution containing the gas, the fine powder obtained in the separation process, fly ash, and blast furnace slag are mixed together to make a geopolymer, which is then solidified (S5 in Figure 1).

[0025] The compounding ratio of the alkaline solution (hereinafter referred to as "A1 component"), fly ash (hereinafter referred to as "B1 component"), blast furnace slag (hereinafter referred to as "C1 component"), and fine powder (hereinafter referred to as "D1 component") is not particularly limited, but for example, the range shown below is preferable. The blending ratio of B1 component to A1 component + C1 component (B1 component / (A1 component + C1 component)) is, by mass, preferably 0.6 to 1.7, more preferably 0.65 to 1.5, and even more preferably 0.7 to 1. When the blending ratio (B1 component / (A1 component + C1 component)) is equal to or greater than the lower limit, the geopolymer solidifies. When the blending ratio (B1 component / (A1 component + C1 component)) is equal to or less than the upper limit, the waste body can be produced by kneading.

[0026] The blending ratio of the C1 component to the A1 component (C1 component / A1 component) is, by mass, preferably 0.1 to 1, more preferably 0.3 to 0.7, and even more preferably 0.4 to 0.5. When the blending ratio (C1 component / A1 component) is within the range between the lower and upper limits, the quality is stable even if the type of fly ash is changed.

[0027] The blending ratio of D1 component to A1 component + B1 component + C1 component (D1 component / (A1 component + B1 component + C1 component)) is, in mass ratio, preferably 0.5 or more and 2.5 or less, more preferably 1 or more and 2.5 or less, and even more preferably 1.5 or more and 2.5 or less. When the blending ratio (D1 component / (A1 component + B1 component + C1 component)) is equal to or more than the lower limit, the waste blend is efficient when it is turned into waste. When the blending ratio (D1 component / (A1 component + B1 component + C1 component)) is equal to or less than the upper limit, the waste can be kneaded to produce waste.

[0028] Fly ash is a type of ash produced when coal is burned. Examples of fly ash include fly ash types I to IV, whose quality standards are defined in JIS A 6201:2015. In addition, in the present invention, fly ash raw powder that does not comply with the JIS standard and is not subjected to any classification treatment or the like may be used, which is obtained from fly ash generated from a coal-fired power plant. The fly ash may be used alone or in combination of two or more types.

[0029] As the blast furnace slag, either air-cooled blast furnace slag or granulated blast furnace slag can be used. As an example of blast furnace slag, there is blast furnace slag powder for concrete (Blaine value 3000 cm), the quality standard of which is set in JIS A 6206:2013. 2 / g class, 4000cm 2 / g class, 6000cm 2 / g class, 8000cm 2 / g class).

[0030] The method of kneading the alkaline solution, fine powder, fly ash, and blast furnace slag is not particularly limited, but it is preferable to, for example, put the raw materials into a container such as a kneading bowl and knead them using a stirring device such as a twin-shaft mixer. From the viewpoint of safety, it is preferable to knead the fine powder, which is radioactive waste, with the other raw materials (alkaline solution, fly ash, and blast furnace slag) to form a paste before adding it.

[0031] A geopolymer containing an alkaline solution, fine powder, fly ash, and blast furnace slag is poured into a formwork and left to harden for, for example, one to fourteen days.

[0032] The solidified geopolymer will be sent to a final disposal site and disposed of as radioactive waste.

[0033] According to the method for treating radioactive waste of this embodiment, the radioactive material generated by heating the contaminated concrete is 14 CO 2 The gas-containing alkaline solution is ground with heated contaminated concrete to obtain fine mortar powder, which is then mixed with fly ash and blast furnace slag to produce a geopolymer, which is then solidified to produce radioactive waste, making it possible to efficiently and appropriately treat radioactive waste. In other words, since all of the components used in the radioactive waste treatment method of this embodiment are waste, the waste can be effectively utilized to solidify the radioactive waste.

[0034] [Solidified geopolymer] The geopolymer solidified material of this embodiment includes alkali carbonate, fine powder of mortar obtained from contaminated concrete, fly ash, and blast furnace slag. The solidified geopolymer of this embodiment can be obtained by the radioactive waste treatment method of the above embodiment.

[0035] In the solidified geopolymer of this embodiment, the compounding ratio of the alkali carbonate (hereinafter referred to as "A2 component"), fly ash (hereinafter referred to as "B2 component"), blast furnace slag (hereinafter referred to as "C2 component"), and fine powder (hereinafter referred to as "D2 component") is not particularly limited, but for example, the range shown below is preferable. Alkaline carbonate is dissolved in the above-mentioned alkaline solution. 14 CO 2 It is made up of gases combined.

[0036] The blending ratio of B2 component to A2 component + C2 component (B2 component / (A2 component + C2 component)) is, in mass ratio, preferably 0.6 to 1.7, more preferably 0.65 to 1.5, and even more preferably 0.7 to 1. When the blending ratio (B2 component / (A2 component + C2 component)) is equal to or greater than the lower limit, the geopolymer solidifies. When the blending ratio (B2 component / (A2 component + C2 component)) is equal to or less than the upper limit, the waste body can be produced by kneading.

[0037] The blending ratio of the C2 component to the A2 component (C2 component / A2 component) is, by mass, preferably 0.1 to 1, more preferably 0.3 to 0.7, and even more preferably 0.4 to 0.5. When the blending ratio (C2 component / A2 component) is within the range between the lower and upper limits, the quality is stable even if the type of fly ash is changed.

[0038] The blending ratio of D2 component to A2 component + B2 component + C2 component (D2 component / (A2 component + B2 component + C2 component)) is, in mass ratio, preferably 0.5 to 2.5, more preferably 1 to 2.5, and even more preferably 1.5 to 2.5. When the blending ratio (D2 component / (A2 component + B2 component + C2 component)) is equal to or greater than the lower limit, the waste is blended efficiently when it is turned into waste. When the blending ratio (D2 component / (A2 component + B2 component + C2 component)) is equal to or less than the upper limit, the waste can be kneaded to produce waste.

[0039] The solidified geopolymer of this embodiment preferably has a compressive strength of 1470 kPa or more as measured by a measurement method conforming to JIS A 1108:2018 "Concrete Compressive Strength Test Method". If the compressive strength of the solidified geopolymer is 1470 kPa or more, the solidified geopolymer can be disposed of as radioactive waste in a final disposal site.

[0040] Since all components of the solidified geopolymer of this embodiment are waste, it can be safely and appropriately disposed of as radioactive waste in a final disposal site without using any materials other than the waste.

Claims

1. １４ CO ２ a crushing step of crushing the contaminated concrete; A heating step of heating the crushed contaminated concrete; The above-mentioned contaminated concrete was heated. １４ CO ２ The gas is captured with an alkaline solution, １４ CO ２ a capturing step of obtaining an alkaline solution containing the gas; a separation step of grinding the heated contaminated concrete to separate it into coarse aggregate and fine mortar powder; The above １４ CO ２ A method for treating radioactive waste, comprising: kneading an alkaline solution containing gas, the fine powder, fly ash, and blast furnace slag to form a geopolymer; and solidifying the geopolymer.

2. 2. The method for treating radioactive waste according to claim 1, wherein the temperature at which the contaminated concrete is heated in the heating step is 300° C. or higher and 400° C. or lower.

3. 2. The method for treating radioactive waste according to claim 1, wherein the alkaline solution is an aqueous solution of sodium hydroxide having a concentration of 1 mol / L or more.

4. A geopolymer solidified material comprising alkaline carbonate, fine powder of mortar obtained from contaminated concrete, fly ash, and blast furnace slag.

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