JP2016142599A - Method foe removing radioactive substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently removing radioactive substances contained in zirconium molybdate.SOLUTION: Zirconium molybdate 1 containing radioactive substances is brought into contact with a dissolving/removing agent of the zirconium molybdate, so that the radioactive substances are dissolved and removed together with the zirconium molybdate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for removing a radioactive substance, and more particularly, to a method for removing a radioactive substance contained in zirconium molybdate.

  Conventionally, there has been proposed a fixed sludge removal method for removing sludge containing a radioactive substance mainly composed of zirconium molybdate fixed to the inner surface of a melting tank or the like of a nuclear fuel reprocessing facility (see, for example, Patent Document 1). . In this fixed sludge removal method, a strong base such as sodium hydroxide is contacted with a sludge mainly composed of zirconium molybdate adhering to the inner surface of the dissolution reaction tank to dissolve molybdenum, and then a strong acid such as nitric acid is contacted. Thus, by dissolving zirconium, sludge fixed to the dissolution reaction tank is efficiently removed.

JP 2001-147296 A

  However, in the method of removing the fixed sludge from the dissolution reaction tank described in Patent Document 1, in order to efficiently remove the sludge fixed to the dissolution reaction tank, the strong base and the strong acid that are difficult to handle are alternately switched several times. It is necessary to clean it in contact with fixed sludge. For this reason, the amount of waste liquid required for removal of the fixed sludge increases, making it difficult to treat the waste liquid, and there is a situation where the fixed sludge cannot always be efficiently removed.

  This invention is made | formed in view of such a situation, and it aims at providing the removal method of the radioactive substance which can remove efficiently the radioactive substance contained in a zirconium molybdate.

  The method for removing a radioactive substance according to the present invention is characterized in that the radioactive substance is dissolved and removed together with the zirconium molybdate by bringing a dissolution remover that dissolves the zirconium molybdate into contact with zirconium molybdate containing the radioactive substance. To do.

  According to this configuration, since the dissolution remover that dissolves the zirconium molybdate is brought into contact with the zirconium molybdate, the radioactive substance contained in the zirconium molybdate can be efficiently removed.

  In the method for removing a radioactive substance of the present invention, it is preferable that the dissolution remover is an alkaline aqueous solution containing a chelating agent. With this configuration, molybdenum of zirconium molybdate can be dissolved with an alkaline aqueous solution, and zirconium can be dissolved with a chelating agent, so that radioactive substances contained in zirconium molybdate can be efficiently removed.

  In the method for removing a radioactive substance of the present invention, the alkaline aqueous solution is preferably an aqueous solution of an alkali metal hydroxide. With this configuration, molybdenum of zirconium molybdate can be efficiently dissolved, so that radioactive substances contained in zirconium molybdate can be efficiently removed.

  In the method for removing a radioactive substance of the present invention, the alkali metal hydroxide preferably contains at least one selected from the group consisting of sodium hydroxide, lithium hydroxide, and potassium hydroxide. With this configuration, molybdenum of zirconium molybdate can be efficiently dissolved, so that radioactive substances contained in zirconium molybdate can be efficiently removed.

  In the method for removing a radioactive substance of the present invention, the chelating agent is ethylenediaminetetraacetate, oxalic acid, citric acid, itaconic acid, aconitic acid, malic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberin. It is preferable to contain at least one selected from the group consisting of acids, azelaic acid, phthalic acid, isophthalic acid and glycolic acid. With this configuration, zirconium can be dissolved efficiently, so that radioactive substances contained in zirconium molybdate can be efficiently removed.

  In the method for removing a radioactive substance of the present invention, the alkaline aqueous solution preferably contains a potential adjusting agent. With this configuration, molybdenum of zirconium molybdate can be efficiently dissolved, so that radioactive substances contained in zirconium molybdate can be efficiently removed.

  In the method for removing a radioactive substance according to the present invention, the dissolution remover is preferably an acidic aqueous solution containing nanobubbles. With this configuration, zirconium of molybdenum molybdate can be dissolved by an acidic aqueous solution, and molybdenum can be dissolved by positively charged nanobubbles, so that radioactive substances contained in zirconium molybdate can be efficiently removed.

  In the method for removing a radioactive substance of the present invention, it is preferable that the dissolution removing agent is an acidic aqueous solution containing at least one surfactant selected from the group consisting of a cationic surfactant and an amphoteric surfactant. . With this configuration, zirconium of molybdenum molybdate can be dissolved by an acidic aqueous solution, and molybdenum can be dissolved by a positively charged surfactant, so that the radioactive substance contained in zirconium molybdate can be efficiently removed.

  In the method for removing a radioactive substance of the present invention, the dissolution / removal agent is preferably an alkaline aqueous solution containing at least one selected from the group consisting of an anionic surfactant and an amphoteric surfactant. With this configuration, molybdenum of zirconium molybdate can be dissolved by an alkaline aqueous solution, and zirconium can be dissolved by a negatively charged surfactant, so that the radioactive substance contained in zirconium molybdate can be efficiently removed.

  ADVANTAGE OF THE INVENTION According to this invention, the removal method of the radioactive substance which can remove efficiently the radioactive substance contained in a zirconium molybdate is realizable.

FIG. 1 is an explanatory view of zirconium molybdate containing a radioactive substance. FIG. 2 is a graph showing the relationship between the dissolution amount of zirconium molybdate and the pH of the dissolution remover. FIG. 3A is an explanatory view of dissolution removal of zirconium molybdate containing a radioactive substance. FIG. 3B is an explanatory diagram of dissolution removal of zirconium molybdate containing a radioactive substance. FIG. 4 is a conceptual diagram of the radioactive substance removal method according to the first embodiment of the present invention. FIG. 5 is a diagram showing the relationship of the amount of zirconium molybdate dissolved with respect to the pH of the dissolution remover to which a chelating agent is added. FIG. 6 is a diagram showing the relationship between the chelating agent concentration of the dissolution remover and the metal concentration. FIG. 7 is a conceptual diagram of the potential pH of molybdenum and zirconium. FIG. 8 is a flowchart of the radioactive substance removal method according to the present embodiment. FIG. 9 is a schematic diagram illustrating an example of equipment to be cleaned. FIG. 10 is a conceptual diagram of a radioactive substance removal method according to the second embodiment of the present invention. FIG. 11 is a diagram showing the relationship between the pH of the dissolution agent and the zeta potential of the nanobubbles. FIG. 12A is a conceptual diagram of a radioactive substance removal method according to the third embodiment of the present invention. FIG. 12B is a conceptual diagram of a radioactive substance removal method according to the third embodiment of the present invention.

  FIG. 1 is an explanatory view of zirconium molybdate containing a radioactive substance. As shown in FIG. 1, zirconium molybdate 1 to be dissolved and removed by the radioactive substance removal method according to the present embodiment is sludge fixed to the inner wall of the dissolution tank 11 of the nuclear fuel reprocessing facility. In this zirconium molybdate 1, molybdenum 12 and zirconium 13 are alternately laminated. Further, the zirconium molybdate 1 adheres to the inner wall of the dissolution tank 11 in a state where the radioactive substance 14 is wound between the molybdenum 12 and the zirconium 13 and contained therein. Zirconium molybdate 1 can be dissolved and removed by bringing it into contact with a strong acid and strong basic dissolution remover.

  FIG. 2 is a graph showing the relationship between the dissolution amount of zirconium molybdate and the pH of the dissolution remover. As shown in FIG. 2, zirconium molybdate has a higher zirconium dissolution amount and a lower molybdenum dissolution amount in the acidic region where the pH of the dissolution remover is low. Further, zirconium molybdate has a higher dissolution amount of molybdenum and a lower dissolution amount of zirconium in the basic region where the pH of the dissolution agent is large. Furthermore, in the zirconium molybdate, in the neutral region where the pH is around 7, both the dissolved amount of molybdenum and the dissolved amount of zirconium become small.

  As shown in FIG. 3A, when zirconium molybdate 1 containing a radioactive substance 14 is brought into contact with a strongly acidic dissolution remover, zirconium 13 on the surface of zirconium molybdate 1 is dissolved and removed, while molybdenum 12 Is deposited on the surface and the radioactive substance 14 in the zirconium molybdate 1 cannot be dissolved and removed. As shown in FIG. 3B, when zirconium molybdate 1 containing radioactive substance 14 is brought into contact with a strongly basic dissolution remover, molybdenum 12 on the surface of zirconium molybdate 1 is dissolved and removed. Zirconium 13 is deposited on the surface, and the radioactive substance 14 inside the zirconium molybdate 1 cannot be dissolved and removed. Therefore, generally, in order to dissolve and remove the zirconium molybdate 1 containing the radioactive substance 14, a strong acidic dissolution remover and a strongly basic dissolution remover are alternately brought into contact with the zirconium molybdate 1. There was a need.

  The inventors paid attention to the dissolution characteristics of the zirconium molybdate 1 described above. As a result of various studies on the liquidity and additives of the dissolution remover, the present inventors have found that the radioactive substance 14 can be dissolved and removed together with the zirconium molybdate 1 only by using a single dissolution remover. It came to complete. That is, the gist of the present invention is to dissolve and remove the radioactive substance 14 together with the zirconium molybdate 1 by contacting the zirconium molybdate 1 containing the radioactive substance with a dissolution removing agent that dissolves the zirconium molybdate 1.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, it is not limited to each following embodiment, It can implement by changing suitably. Also, the following embodiments can be implemented in combination as appropriate. Moreover, the same code | symbol is attached | subjected to the component which is common in each embodiment, and duplication of description is avoided.

(First embodiment)
In the method for removing a radioactive substance according to the first embodiment of the present invention, a zirconium molybdate containing a radioactive substance is brought into contact with an alkaline aqueous solution containing a chelating agent that dissolves the zirconium molybdate and then radioactive together with the zirconium molybdate. The substance is dissolved and removed.

FIG. 4 is a conceptual diagram of the radioactive substance removal method according to the first embodiment. As shown in FIG. 4, in this embodiment, since zirconium molybdate 1 is brought into contact with an alkaline aqueous solution containing a chelating agent 15, molybdenum 12 is dissolved and removed by the alkaline aqueous solution, and the surface of zirconium molybdate 1 is also removed. The precipitated zirconium 13 and chelating agent 15 form a chelate and dissolve in the alkaline aqueous solution. When oxalic acid ((COOH) ₂ ) is used as the chelating agent, zirconium molybdate (Mo ₂ ZrO ₇ (OH) ₂ .2H ₂ O) based on the following formula (1) Forms a chelate and zirconium depends on the pH of the dissolution agent Zr [(COO) ₂ ] ²⁺ , Zr [(COO) ₂ ] ₂ , Zr [(COO) ₂ ] ₃ ²⁻ and Zr [( COO) ₂ ] ₄ ⁴⁻ is dissolved in the dissolution remover, and molybdenum is dissolved in the dissolution remover as MoO ₄ ²⁻ . As a result, it is possible to dissolve and remove the radioactive substance 14 entrained in the zirconium molybdate 1 together with the zirconium molybdate 1 only by using an alkaline aqueous solution.
Mo ₂ ZrO ₇ (OH) ₂ .2H ₂ O + (COOH) ₂ → Zr [(COO) ₂ ] ²⁺ + Zr [(COO) ₂ ] ₂ + Zr [(COO) ₂ ] ₃ ²⁻ + Zr [(COO) ₂ ] ₄ ^4- + MoO ₄ ^2- (1)

  FIG. 5 is a diagram showing the relationship of the amount of zirconium molybdate dissolved with respect to the pH of the dissolution remover to which a chelating agent is added. As shown in FIG. 5, by adding a chelating agent, the dissolved amount of zirconium changes from the dotted line L1 to the solid line L2 and increases in a region where the pH is large due to the above-described effects. Therefore, in this embodiment, zirconium molybdate can be efficiently dissolved and removed by adding a chelating agent to an alkaline aqueous solution having a high pH and using it as a dissolution and removal agent.

  FIG. 6 is a diagram showing the relationship between the chelating agent concentration of the dissolution remover and the metal concentration. In FIG. 6, the horizontal axis represents the chelating agent concentration, and the vertical axis represents the lower metal ion concentration of molybdenum or zirconium dissolved in the alkaline aqueous solution. In FIG. 6, when the sodium hydroxide concentration is 0 mol / L and the concentration of oxalic acid is changed as a chelating agent (see L3), the sodium hydroxide concentration is 0.5 mol / L and oxalic acid is used as a chelating agent. When the concentration of oxalic acid is changed (see L4) and when the sodium hydroxide concentration is 1.5 mol / L and the concentration of oxalic acid as a chelating agent is changed (see L5).

  As shown in FIG. 6, it can be seen that when the sodium hydroxide concentration is 0.5 mol / L, the metal ion concentration is greatly increased when the sodium hydroxide concentration is 0 mol / L. From this result, it is understood that zirconium molybdate can be efficiently dissolved and removed by increasing the pH of the dissolution remover and using it together with the chelating agent. When the sodium hydroxide concentration is 1.5 mol / L, when the sodium hydroxide concentration is 0.5 mol / L, the metal ion concentration is only the chelating agent in the range where the chelating agent is low. It can be seen that the metal ion concentration increases with increasing chelator concentration, although lower than when used. From this result, it is understood that zirconium molybdate can be efficiently dissolved and removed by controlling the pH of the dissolution agent and the chelating agent concentration within a predetermined range.

  The chelating agent is not particularly limited as long as it can form a chelate with zirconium 13 in an alkaline aqueous solution, and various conventionally known chelating agents can be used. Chelating agents include ethylenediaminetetraacetate (EDTA), oxalic acid, citric acid, itaconic acid, aconitic acid, malic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelonic acid, phthalic acid , Isophthalic acid and glycolic acid. These chelating agents may be used individually by 1 type, and may use 2 or more types together. Among these chelating agents, oxalic acid and ethylenediaminetetraacetate (EDTA) are preferable from the viewpoint that zirconium 13 can be efficiently dissolved and removed.

  The alkaline aqueous solution is not particularly limited as long as it can dissolve and remove molybdenum 12, and various conventionally known alkaline aqueous solutions can be used. Examples of the alkaline aqueous solution include an aqueous solution of an alkali metal hydroxide. Examples of the alkali metal hydroxide include sodium hydroxide, lithium hydroxide, potassium hydroxide and cesium hydroxide. These alkali metal hydroxides may be used alone or in combination of two or more. Among these alkali metal hydroxides, sodium hydroxide, lithium hydroxide, potassium hydroxide, and cesium hydroxide are preferable, and sodium hydroxide is more preferable from the viewpoint that molybdenum 12 can be efficiently dissolved and removed.

  The pH of the dissolution remover is preferably 4 or more, more preferably 2 or more, and preferably 11 or less from the viewpoint of efficiently dissolving and removing zirconium molybdate.

  The concentration of the chelating agent in the dissolution / removal agent is preferably 0.5 mol / L or more, and preferably 2.0 mol / L from the viewpoint of efficiently dissolving and removing zirconium molybdate.

  As content of the chelating agent of the dissolution / removal agent, the equivalent of the carboxyl group equivalent of the chelating agent is more preferably in the range of 1: 1 to 1: 4 with respect to the equivalent of the hydroxyl group of the alkali metal oxide.

  In the radioactive substance removal method according to the present embodiment, it is preferable that the dissolution remover further contains a potential adjusting agent. By containing this potential adjusting agent, zirconium molybdate can be dissolved and removed more efficiently.

FIG. 7 is a conceptual diagram of the potential pH of molybdenum and zirconium. As shown in FIG. 7, when a chelating agent such as oxalic acid having reducing properties is added to the dissolution remover, the oxidation-reduction potential based on the hydrogen electrode of the dissolution remover is insoluble so that molybdenum of zirconium molybdate becomes MoO _2. It becomes area A1. Therefore, by adding a potential adjusting agent that improves the oxidation-reduction potential of the dissolution remover such as hydrogen peroxide, the oxidation-reduction potential of the dissolution remover increases outside the insoluble region A1 of molybdenum. Can be dissolved and removed more efficiently.

  Potential regulators include peroxides such as hydrogen peroxide, peroxoacids such as peroxyacetic acid, peroxoacid salts, oxygen gas, ozone, carbon dioxide, perchloric acid, perchlorate, hypochlorous acid, And hypochlorite can be used. These potential adjusting agents may be used alone or in combination of two or more. Among these, hydrogen peroxide is preferable from the viewpoint of efficiently dissolving and removing zirconium molybdate.

  The concentration of the potential regulator of the dissolution remover is preferably 0.1% by mass or more, more preferably 10% by mass or less, and more preferably 5% by mass or less from the viewpoint of efficiently dissolving and removing zirconium molybdate.

  Next, a method for removing a radioactive substance according to the present embodiment will be described in detail. FIG. 8 is a flowchart of the radioactive substance removal method according to the present embodiment. As shown in FIG. 8, in the method for removing a radioactive substance according to the present embodiment, first, a dissolution remover is prepared (step ST11), and then the symmetrical equipment to be cleaned is cleaned using the prepared dissolution remover. (Step ST12). Next, after the dissolved and removed agent containing the washed radioactive substance is recovered as a waste liquid (step ST13), the radioactive substance is separated from the waste liquid (step ST14). Here, the radioactive material separated from the waste liquid is discarded as radioactive waste. Next, the waste liquid from which the radioactive substance has been separated is purified, and a small amount of radioactive substance dissolved in the waste liquid is discarded as radioactive waste (step ST15). For the purification of the waste liquid here, it is possible to use a concentration facility and a neutralization facility of the reprocessing facility. The purified dissolution remover is used again as a dissolution removal agent for the equipment to be cleaned. For the purification of waste liquid, existing equipment may be used, or dedicated equipment may be provided.

  FIG. 9 is a schematic diagram illustrating an example of equipment to be cleaned. This equipment 100 to be cleaned includes a plurality of nuclear fuel reprocessing equipment dissolution tanks in a cell 101 having a concrete sealable structure. The cell 101 is provided with a supply pipe 102 for supplying the cleaning liquid into the cell 101 and a discharge pipe 103 for discharging the cleaning liquid in the cell. Further, the cell 101 is provided with a steam pipe L <b> 1 for supplying steam into the cell 101 and an air pipe L <b> 2 for supplying air into the cell 101. The steam pipe L1 is provided with an adjustment valve V1 for adjusting the supply amount of steam, and the air pipe L2 is provided with an adjustment valve V2 for adjusting the supply amount of air. In the method for removing a radioactive substance according to the present embodiment, zirconium molybdate can be dissolved and removed using a single dissolving and removing agent. Therefore, a dissolving and removing agent is supplied into the cell 101 to dissolve and remove the inside of the cell 101. Then, the cell 101 can be cleaned simply by discharging the dissolution remover from the cell 101. In addition, since the inside of the cell 101 can be cleaned with a single dissolution and removal agent, not only the supply pipe 102 but also the steam pipe L1 and the air pipe L2 which are utilities of transfer equipment unique to the reprocessing facility, enter the cell 101 The inside of the cell 101 can be efficiently cleaned also by supplying the dissolution remover.

  As described above, according to this embodiment, since the alkaline aqueous solution containing the chelating agent is brought into contact with zirconium molybdate, not only the molybdenum can be dissolved by the alkaline aqueous solution, but also the zirconium can be dissolved by the chelating agent. As a result, the radioactive substance removal method can quickly dissolve and remove the radioactive substance entrained in zirconium molybdate, so that the radioactive substance mainly composed of zirconium molybdate can be efficiently removed. It becomes.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the following, differences from the first embodiment described above will be mainly described to avoid duplication of description. Further, description of components common to the above-described first embodiment is omitted.

  In the method for removing a radioactive substance according to the second embodiment of the present invention, zirconium molybdenum molybdate containing a radioactive substance is contacted with an acidic aqueous solution containing nanobubbles as a dissolution and removal agent for dissolving zirconium molybdate. A radioactive substance is dissolved and removed together with zirconium acid.

  FIG. 10 is a conceptual diagram of a radioactive substance removal method according to the second embodiment of the present invention. As shown in FIG. 10, in the radioactive substance removal method according to the present embodiment, an acidic aqueous solution containing nanobubbles is brought into contact with zirconium molybdate 1, so that zirconium 13 of zirconium molybdate 1 is dissolved by the acidic aqueous solution. As a result, zirconium molybdate 1 becomes brittle. Since the remaining molybdenum 12 of the zirconium molybdate 1 is negatively charged (−), the zirconium molybdate 1 embrittled by electrostatic interaction with the nanobubbles 16 charged positively (+) in the acidic solution. Peel and dissolve. As a result, together with the zirconium molybdate 1, the radioactive substance 14 entrained in the zirconium molybdate 1 can be efficiently dissolved and removed.

  FIG. 11 is a diagram showing the relationship between the pH of the dissolution agent and the zeta potential of the nanobubbles. As shown in FIG. 11, the nanobubbles are negatively charged when the pH of the dissolution / removal agent is negative, whereas they are positively charged when the pH is 4 or less. Therefore, in the present embodiment, by using an acidic aqueous solution as the dissolution removing agent, the nanobubbles are positively charged, and the molybdenum 12 can be efficiently dissolved and removed by the above-described effects.

  The acidic aqueous solution is not particularly limited as long as it can dissolve and remove zirconium 13, and various conventionally known acidic aqueous solutions can be used. Examples of the acidic aqueous solution include aqueous solutions of acids such as sulfuric acid, nitric acid, and hydrochloric acid. These acids may be used individually by 1 type, and may use 2 or more types together. Of these acids, nitric acid is preferred.

  There is no restriction | limiting in particular as a generation method of nanobubble, For example, a pressurization melt | dissolution system, a two phase flow swirl release type, a dispersal type etc. are mentioned.

  The bubble diameter of the nanobubble is not particularly limited as long as molybdenum 12 can be dissolved and removed. The bubble diameter of the nanobubbles is preferably less than 1 μm, more preferably from 10 nm to 500 nm, and even more preferably from 100 nm to 200 nm from the viewpoint of efficiently dissolving the molybdenum 12.

(Third embodiment)
Next, a third embodiment of the present invention will be described. In the following description, differences from the first embodiment and the second embodiment described above will be mainly described, and overlapping description will be avoided. Further, description of components common to the first embodiment and the second embodiment described above is omitted.

  The method for removing a radioactive substance according to the third embodiment of the present invention includes a cationic surfactant and an amphoteric surfactant as a dissolution and removal agent for dissolving zirconium molybdate in zirconium molybdate containing the radioactive substance. Molybdic acid by contacting an acidic aqueous solution containing at least one surfactant selected from the group consisting of or an alkaline aqueous solution containing at least one selected from the group consisting of an anionic surfactant and an amphoteric surfactant The radioactive substance is dissolved and removed together with zirconium.

  12A and 12B are conceptual diagrams of a radioactive substance removal method according to the third embodiment of the present invention. As shown in FIG. 12A, in the method for removing a radioactive substance according to the present embodiment, an acidic aqueous solution containing at least one surfactant selected from the group consisting of a cationic surfactant and an amphoteric surfactant. Is brought into contact with the zirconium molybdate 1, the zirconium 13 of the zirconium molybdate 1 is dissolved by the acidic aqueous solution, and the zirconium molybdate 1 becomes brittle. Since the remaining molybdenum 12 of zirconium molybdate 1 is negatively (−) charged, at least one selected from the group consisting of a cationic surfactant and an amphoteric surfactant charged positively (+) in an acidic solution. It peels and dissolves from the zirconium molybdate 1 embrittled by electrostatic interaction with the seed surfactant 17. As a result, together with the zirconium molybdate 1, the radioactive substance 14 entrained in the zirconium molybdate 1 can be efficiently dissolved and removed. As alkaline aqueous solution, the thing similar to 1st Embodiment mentioned above can be used.

  In addition, as shown in FIG. 12B, the radioactive substance removal method according to the present embodiment contains at least one surfactant selected from the group consisting of an anionic surfactant and an amphoteric surfactant. Since the acidic aqueous solution is brought into contact with the zirconium molybdate 1, the molybdenum 12 of the zirconium molybdate 1 is dissolved by the acidic aqueous solution and the zirconium molybdate 1 becomes brittle. Since the remaining zirconium 13 of zirconium molybdate 1 is positively (+) charged, it is at least one selected from the group consisting of an anionic surfactant and an amphoteric surfactant that are negatively (−) charged in an alkaline solution. It peels and dissolves from the zirconium molybdate 1 embrittled by electrostatic interaction with the seed surfactant 18. As a result, together with the zirconium molybdate 1, the radioactive substance 14 entrained in the zirconium molybdate 1 can be efficiently dissolved and removed. As acidic aqueous solution, the thing similar to 2nd Embodiment mentioned above can be used.

（式（１）中、Ｒ_１〜Ｒ_４は、ステアリル基、パルミチル基、メチル基、又はブチル基などのアルキル基を表す。Ｘは、塩素又は臭素などのハロゲンを表す。） Examples of the cationic surfactant include alkylamine salts and quaternary ammonium salts represented by the following general formula (1).

(In formula (1), R _{1 to} R ₄ represent an alkyl group such as a stearyl group, a palmityl group, a methyl group, or a butyl group. X represents a halogen such as chlorine or bromine.)

R _{1 to} R ₄ in the formula (1) are preferably an alkyl group having 1 to 25 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, and more preferably a carbon number from the viewpoint of waste liquid treatment. 1 to 5 alkyl groups are more preferred.

  Examples of anionic surfactants include alkyl sulfonates, alkyl sulfates, acylated amino acid salts, polyoxyethylene alkyl ether sulfates, alkyl benzene sulfonates, N-acyl-N-methyl taurate salts, and α-olefin sulfonic acids. Salt, higher fatty acid ester sulfonate, alkyl ether acetate, polyoxyethylene alkyl ether acetate, fatty acid soap, alkyl phosphate ester salt, N-lauroyl glutamate, N-palmitoyl glutamate, N-lauroyl-N- Examples include ethyl glycine salt, N-lauroyl sarcosine salt, and N-myristoyl-β-alanine salt.

  Amphoteric surfactants include alkylbetaine activators such as alkyldimethylaminoacetic acid betaine, amide betaine activators such as alkylamidopropyl betaine, sulfobetaine activators, hydroxysulfobetaine activators, amide sulfobetaine activators Agents, phosphobetaine activators, imidazolinium betaine activators, aminopropionic acid activators, and amino acid activators.

  The concentration of the surfactant is preferably 0.1% by mass or more with respect to the dissolution remover, for example.

  The pH of the acidic aqueous solution is preferably less than 7, and more preferably 4 or less.

  The pH of the alkaline aqueous solution is preferably more than 7 and more preferably 10 or more.

DESCRIPTION OF SYMBOLS 1 Zirconium molybdate 11 Dissolution tank 12 Molybdenum 13 Zirconium 14 Radioactive substance 15 Chelating agent 16 Nano bubble 17,18 Surfactant

Claims (9)

  A method for removing a radioactive substance, comprising contacting a zirconium molybdate containing a radioactive substance with a dissolution remover for dissolving the zirconium molybdate to dissolve and remove the radioactive substance together with the zirconium molybdate.   The method for removing a radioactive substance according to claim 1, wherein the dissolution and removal agent is an alkaline aqueous solution containing a chelating agent.   The method for removing a radioactive substance according to claim 2, wherein the alkaline aqueous solution is an aqueous solution of an alkali metal hydroxide.   The method for removing a radioactive substance according to claim 2 or 3, wherein the alkali metal hydroxide contains at least one selected from the group consisting of sodium hydroxide, lithium hydroxide and potassium hydroxide.   The chelating agent is ethylenediaminetetraacetate, oxalic acid, citric acid, itaconic acid, aconitic acid, malic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelonic acid, phthalic acid, isophthalic acid The method for removing a radioactive substance according to any one of claims 2 to 4, comprising at least one selected from the group consisting of and glycolic acid.   The method for removing a radioactive substance according to any one of claims 2 to 5, wherein the alkaline aqueous solution contains a potential adjusting agent.   The method for removing a radioactive substance according to claim 1, wherein the dissolution remover is an acidic aqueous solution containing nanobubbles.   The method for removing a radioactive substance according to claim 1, wherein the dissolution remover is an acidic aqueous solution containing at least one surfactant selected from the group consisting of a cationic surfactant and an amphoteric surfactant.   The method for removing a radioactive substance according to claim 1, wherein the dissolution remover is an alkaline aqueous solution containing at least one selected from the group consisting of an anionic surfactant and an amphoteric surfactant.

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