JP7178322B2 - Radioactive waste liquid treatment method and radioactive waste liquid treatment system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a radioactive waste liquid treatment method and a radioactive waste liquid treatment system, and is particularly suitable for treatment of radioactive waste liquid generated by washing waste resin generated from a nuclear power plant and radioactive waste liquid generated by nuclear fuel reprocessing. The present invention relates to a radioactive waste liquid treatment method and a radioactive waste liquid treatment system.

Cellulosic filter aids, filter sludge containing ion-exchange resins, and other radioactive organic waste generated from reactor coolant cleanup systems and fuel pool coolant cleanup systems of nuclear power plants shall be stored in storage tanks for a long period of time. It is These radioactive organic wastes are constantly generated with the operation of nuclear power plants.

In order to secure storage space for radioactive organic waste, volume reduction processing technology is required to efficiently reduce the volume of currently stored radioactive organic waste.
The ion exchange resin is based on styrene-divinylbenzene and is chemically stable, so it can be safely stored for a long period of time. However, due to its stability, decomposition treatment is difficult, and in the case of reducing the volume of the ion-exchange resin, a thermal decomposition treatment at a high temperature is usually required.

Pyrolysis and methods other than pyrolysis are known for reducing the volume of radioactive organic waste, and some of these methods are described in Patent Document 1 below.
This Patent Document 1 describes a volume reduction method capable of not only reducing the volume of radioactive organic waste but also reducing the concentration of radioactive substances contained in the radioactive organic waste.
Specifically, in the volume reduction method described in Patent Document 1, the clad (including radionuclides such as cobalt 60, iron oxide, etc.) contained in radioactive organic waste is reduced to cobalt 60, etc. by an organic acid aqueous solution. is dissolved together with the radionuclides, and radioactive organic wastes, for example, radionuclides (cobalt 60, cesium 137, etc.) adsorbed on the ion exchange resin, which is a waste resin, are eluted from the ion exchange resin with the organic acid salt aqueous solution. Then, the organic acid contained in the organic acid aqueous solution used for dissolving the crud (iron oxide, etc.) and the organic acid salt contained in the organic acid salt aqueous solution used for eluting the radionuclide are treated with ozone or the like. It decomposes by Furthermore, the waste liquid containing radionuclides remaining after decomposition of the organic acid and organic acid salt is dried and powdered, and the obtained powder containing radionuclides is solidified with a solidifying agent (cement, etc.).

Further, Patent Document 2 below describes a method for reprocessing nuclear fuel.
The nuclear fuel reprocessing method described in Patent Document 2 includes a fluorination process and a solvent extraction process. In the fluorination process, fluorine is brought into contact with the nuclear fuel material contained in the spent fuel assemblies removed from the nuclear reactor, and the uranium contained in the nuclear fuel material is reacted with the fluorine and converted into volatile _UF6 . After part or most of the uranium contained in the nuclear fuel material is volatilized as _UF6 , the remaining uranium and plutonium are recovered in a solvent extraction process. The solvent extraction step includes a dissolution step of dissolving the remaining nuclear fuel material with a solution containing nitric acid, an extraction solution containing tributyl phosphate (TBP) is brought into contact with the solution containing the dissolved nuclear fuel material, and the A co-decontamination process in which uranium and plutonium are transferred to the extract liquid side, and the extract liquid containing the extracted uranium and plutonium is brought into contact with a nitric acid aqueous solution with a low nitric acid concentration, and the uranium and plutonium contained in the extract are transferred to the nitric acid aqueous solution side. It includes a transfer back extraction step.

A core of a nuclear reactor of a nuclear power plant is loaded with a large number of fuel assemblies. Each fuel assembly has a plurality of fuel rods filled with nuclear fuel material within cladding tubes. The core is supplied with a coolant, specifically cooling water, which is heated by the heat generated by the nuclear fission of the nuclear fuel material within the fuel rods in the fuel assemblies. A part of the cooling water flowing inside the reactor is supplied to a purification device provided in the reactor coolant purification system, and the radioactive nuclides contained in the cooling water are removed by the purification device.
2. Description of the Related Art In a boiling water nuclear power plant, cooling water is purified by a purification device provided in a purification system pipe of a reactor coolant purification system that supplies cooling water in the reactor (see Patent Document 3). Inside the purifier is an ion exchange resin that purifies the cooling water.
A pressurized water nuclear power plant is also provided with a reactor coolant purification system for purifying the cooling water in the reactor, and this reactor coolant purification system is provided with a purification device in which ion exchange resin is present.

In addition, in the following Patent Document 4, by bringing the adsorbent into contact with a liquid containing a radioactive substance, the radioactive substance is adsorbed by the adsorbent, and the liquid containing the adsorbent is cross-flow filtered to adsorb the radioactive substance. A method for separating the adsorbent and the liquid after adsorption treatment is described.

JP 2015-64334 A JP-A-2002-257980 JP 2018-48831 A JP 2014-66647 A

If the cladding tubes of the fuel rods contained in the fuel assemblies loaded in the core are damaged by any chance, the nuclear fuel materials in the fuel rods, namely uranium (U), plutonium (Pu), neptunium ( Np) and curium (Cm) actinides, which are alpha nuclides, leak into the cooling water. Cooling water containing those alpha nuclides is led to a reactor coolant cleanup system purifier, and each alpha nuclides is removed by an ion exchange resin in the purifier. The half-life of alpha nuclides is the ultra-half-life.

In the method described in Patent Document 1, an ion exchange resin, which is a waste resin that adsorbs α nuclides, is brought into sequential contact with an organic acid aqueous solution and an organic acid salt aqueous solution to remove the clad contained in the ion exchange resin. to elute the radionuclides adsorbed on the ion exchange resin.
In the method described in Patent Document 1, the alpha nuclides removed by the ion exchange resin are also eluted and transferred into the organic acid aqueous solution and the organic acid salt aqueous solution, respectively.

Here, the organic acid contained in the organic acid aqueous solution containing α nuclides and the organic acid salt contained in the organic acid salt aqueous solution containing α nuclides are decomposed and removed, and then the aqueous solution in which the α nuclides remain is concentrated. A large amount of radioactive waste containing half-lived alpha nuclides is generated. It is desirable to reduce the amount of radioactive waste generated containing alpha nuclides with an extra half-life.

Further, in the method described in Patent Document 4, an adsorbent is brought into contact with a liquid containing a radioactive substance.
However, in the case of the method described in Patent Document 4, depending on the water quality of the liquid containing the radioactive substance, even if the radioactive substance is adsorbed by the adsorbent, the radioactive substance cannot be adsorbed sufficiently, and the liquid after the adsorbent is separated Some radioactive material may remain.

An object of the present invention is to provide a radioactive waste liquid treatment method and a radioactive waste liquid treatment system that can reduce the amount of radioactive substances contained in radioactive organic waste and reduce the amount of radioactive waste that contains α-nuclides with a half-life. to provide.

In addition, the above objects, other objects and novel features of the present invention will be made clear by the description of the specification and the accompanying drawings.

The radioactive waste liquid treatment method of the present invention is a radioactive waste liquid treatment method for treating radioactive waste liquid containing α nuclides.
Then, a pH adjuster is injected into the radioactive waste liquid containing the α nuclides, an α nuclide adsorbent is supplied to the radioactive waste liquid containing the α nuclides and the pH adjuster, and the α nuclides are adsorbed by the α nuclides adsorbent, whereby the radioactive waste liquid remove the alpha nuclides from
In the radioactive liquid waste treatment method of the first present invention, the α-nuclide adsorbent is ferrite, and the magnetic susceptibility measuring device detects the ferrite supplied to the radioactive liquid waste.
In the method for treating radioactive waste liquid of the second present invention, when removing alpha nuclides from radioactive waste liquid containing nitric acid and alpha nuclides generated by recovery of uranium and plutonium in nuclear fuel reprocessing, a pH adjuster is used. A certain neutralizing agent is injected into the radioactive waste liquid to neutralize the radioactive waste liquid, and then a reducing agent, which is a pH adjuster, is injected into the radioactive waste liquid containing α-nuclides.

The radioactive waste liquid treatment system of the present invention includes a radioactive waste liquid supply pipe for guiding radioactive waste liquid containing α nuclides, a pH adjuster injection device connected to the radioactive waste liquid supply pipe for injecting a pH adjuster, and a radioactive waste liquid supply pipe. and an α-nuclide removal device for removing α-nuclides from a radioactive waste liquid containing α-nuclides, and an adsorbent injection device for injecting an α-nuclide adsorbent that adsorbs α-nuclides into the α-nuclide removal device. .
In the radioactive waste liquid treatment system of the first invention, the pH adjuster injection device further includes a neutralization liquid injection device and a reducing agent injection device, generated by recovery of uranium and plutonium in nuclear fuel reprocessing, A neutralizing liquid injection device for injecting a neutralizing liquid containing an alkaline neutralizing agent into the radioactive waste liquid containing nitric acid and α nuclides and flowing in the radioactive waste liquid supply pipe is provided with a reducing agent injection device for injecting a reducing agent and a radioactive waste liquid supply pipe. is connected to the radioactive waste liquid supply pipe on the upstream side of the connection point, and the first pH meter is connected to the connection point of the reducing agent injection device and the radioactive waste liquid supply pipe and the connection point of the neutralizing liquid injection device and the radioactive waste liquid supply pipe. In between, it is attached to the radioactive waste liquid supply pipe.
The radioactive waste liquid treatment system of the second aspect of the present invention further has a configuration in which the injection of the pH adjuster into the radioactive waste liquid is performed when the desired α nuclide concentration is reached.
The radioactive waste liquid treatment system of the third aspect of the present invention further comprises an adsorbent separation device for separating the α-nuclide adsorbent from the radioactive waste liquid containing the α-nuclide adsorbent.

According to the present invention, since the pH adjuster is injected into the radioactive waste liquid containing α-nuclides, the pH of the radioactive waste liquid can be adjusted, and the pH of the radioactive waste liquid can be adjusted to sufficiently exhibit the adsorption performance of the α-nuclide adsorbent. It can be within the pH range.
As a result, it is possible to reduce the amount of radioactive substances contained in the radioactive waste obtained by treating the radioactive liquid waste, and to reduce the amount of radioactive waste containing α-nuclides with an extra half-life.

Furthermore, according to the present invention, since the α-nuclide adsorbent is injected into the radioactive waste liquid, the particles of the α-nuclide adsorbent can be made finer, and the specific surface area of the α-nuclide adsorbent can be increased. It becomes possible to control the time during which the nuclide adsorbent is immersed in the radioactive waste liquid.
Therefore, the α-nuclide removal performance of the α-nuclide adsorbent can be improved.

Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

1 is a flow chart showing the procedure of a method for treating radioactive waste liquid in Example 1. FIG. 1 is a configuration diagram of an example of a radioactive waste liquid treatment system that executes the radioactive waste liquid treatment method of Example 1. FIG. FIG. 3 is a detailed configuration diagram of the waste liquid decomposition apparatus of FIG. 2; FIG. 3 is a detailed configuration diagram of the α-nuclide removal device of FIG. 2 ; FIG. 4 is an explanatory diagram showing residual ratios of α nuclides in radioactive waste liquid corresponding to methods for removing α nuclides contained in radioactive waste liquid. It is a figure which shows the size of adsorbent, and the relationship of the adsorption amount of the alpha nuclide per 1g of adsorbent. FIG. 10 is a configuration diagram of an example of a radioactive waste liquid treatment system that executes the radioactive waste liquid treatment method of Example 2; 10 is a flow chart showing the procedure of a method for treating radioactive waste liquid of Example 3. FIG. FIG. 10 is a detailed configuration diagram of an α-nuclide removal device used in Example 3;

Hereinafter, embodiments and examples according to the present invention will be described with reference to sentences or drawings. However, the structure, materials, and various other specific configurations shown in the present invention are not limited to the embodiments and examples taken up here, and can be appropriately combined and improved within the scope of not changing the gist. is. Elements that are not directly related to the present invention are omitted from the drawing.

The purpose of providing a radioactive waste liquid treatment method that can reduce the amount of radioactive substances contained in the radioactive organic waste and can reduce the amount of radioactive waste that contains α-nuclides with a half-life as described above is as follows ( It can be achieved by the radioactive waste liquid treatment method of A1).
(A1) A method for treating radioactive waste liquid containing α nuclides.
The target radioactive liquid waste containing α-nuclides includes, for example, radioactive liquid waste containing α-nuclides generated by desorption of radionuclides containing α-nuclides from cation exchange resin, which is radioactive organic waste, and nuclear fuel reprocessing. radioactive liquid waste containing alpha nuclides generated by the recovery of uranium and plutonium; Moreover, it is not limited to these radioactive waste liquids, and can be applied to radioactive waste liquids generated from other sources as long as they contain α nuclides.
Then, a pH adjuster is injected into the radioactive waste liquid containing the α nuclides, an α nuclide adsorbent is supplied to the radioactive waste liquid containing the α nuclides and the pH adjuster, and the α nuclides are adsorbed by the α nuclide adsorbent, thereby Removes alpha nuclides.

Further, in the method for treating radioactive waste liquid (A1) above, a more preferable method will be described below.

(A2) Preferably, in (A1) above, before the α-nuclides are adsorbed by the α-nuclide adsorbent, the pH of the radioactive waste liquid containing α-nuclides is adjusted to within the range of 4 or more and 11 or less by injecting a pH adjuster. It is desirable to adjust the pH.

(A3) Preferably, in (A2) above, it is a pH adjusting agent when adjusting the pH of the radioactive waste liquid containing α nuclides to a pH within the range of 4 or more and 7 or less within the range of 4 or more and 11 or less. When an acid solution containing an acid is injected to adjust the pH of the radioactive waste liquid to a pH within the range of 4 or more and 11 or less and greater than 7 and within the range of 11 or less, the radioactive waste liquid contains a reducing agent that is a pH adjuster. It is desirable to inject the agent solution.

(A4) Preferably, in (A3) above, an acid solution containing an acid (for example, dilute nitric acid) that cannot be decomposed as the acid solution is used.

(A5) Preferably, in (A3) above, an acid solution containing a decomposable acid (e.g., oxalic acid) is used as the acid solution, and the α-nuclides in the radioactive waste liquid containing the decomposable acid and α-nuclides are It is desirable to decompose the decomposable acid contained in the radioactive effluent after it has been removed and the alpha nuclides have been removed.

(A6) Preferably, in (A1) above, the used α-nuclide adsorbent adsorbing α-nuclides is solidified in a solidification container.

(A7) Preferably, in (A1) above, when treating radioactive waste liquid containing nitric acid and α-nuclides generated by the recovery of uranium and plutonium in nuclear fuel reprocessing, a reducing agent as a pH adjuster is added to the radioactive waste liquid. Prior to the injection, the pH of the radioactive waste liquid is increased by injecting a neutralizing agent, which is another pH adjuster, into the radioactive waste liquid to increase the pH of the radioactive waste liquid containing α nuclides to 4 or more within the range of 4 or more and 11 or less. A pH within the range of 7 or less is desirable.

(A8) Preferably, in the above (A7), when the pH of the radioactive waste liquid containing α nuclides is adjusted to a pH within the range of 4 or more and 11 or less and within the range of 7 or more and 11 or less, by injecting a neutralizing agent It is desirable to bring the pH of the radioactive effluent to 7 and then inject a reducing agent into the radioactive effluent containing the alpha nuclides and the neutralizing agent.

(A9) Preferably, in (A1) above, after the α-nuclides are removed from the radioactive waste liquid by the α-nuclide adsorbent, the α-nuclide adsorbent that adsorbs the α-nuclides is separated from the radioactive waste liquid.

The purpose of providing a radioactive waste liquid treatment system that can reduce the radioactive substances contained in the radioactive organic waste described above and can reduce the amount of radioactive waste that contains α-nuclides with a half-life is the following (B1 ) radioactive waste treatment system.
(B1) A radioactive liquid waste treatment system for treating radioactive liquid waste containing α nuclides.
The target radioactive liquid waste containing α-nuclides includes, for example, radioactive liquid waste containing α-nuclides generated by desorption of radionuclides containing α-nuclides from cation exchange resin, which is radioactive organic waste, and nuclear fuel reprocessing. radioactive liquid waste containing alpha nuclides generated by the recovery of uranium and plutonium; Moreover, it is not limited to these radioactive waste liquids, and can be applied to radioactive waste liquids generated from other sources as long as they contain α nuclides.
This is achieved by a radioactive waste liquid treatment system equipped with a radioactive liquid waste supply pipe for guiding radioactive liquid waste containing α-nuclides, a pH adjuster injection device and an α-nuclide removal device connected to the radioactive liquid waste supply pipe, and an adsorbent injection device. can.
The pH adjuster injector injects the pH adjuster.
The α-nuclide removal device removes α-nuclides from radioactive waste liquid containing α-nuclides.
The adsorbent injector injects an α-nuclide adsorbent that adsorbs α-nuclides into the α-nuclide removal device.

Further, in the above radioactive waste liquid treatment system (B1), a more preferable configuration will be described below.

(B2) Preferably, in (B1) above, the pH adjusting agent injection device includes a neutralizing liquid injection device and a reducing agent injection device, and is generated by recovery of uranium and plutonium in nuclear fuel reprocessing, and nitric acid and a neutralizing liquid injection device for injecting a neutralizing liquid containing an alkaline neutralizing agent into the radioactive waste liquid flowing in the radioactive waste liquid supply pipe, the reducing agent injection device for injecting the reducing agent and the radioactive waste liquid supply pipe It is connected to the radioactive waste liquid supply pipe on the upstream side of the connection point, and the first pH meter is located between the connection point of the reducing agent injection device and the radioactive waste liquid supply pipe and the connection point of the neutralizing liquid injection device and the radioactive waste liquid supply pipe. , preferably attached to the radioactive waste supply pipe.

(B3) Preferably, in (B2) above, a second pH meter is attached to the radioactive waste liquid supply pipe between the connecting point of the reducing agent injection device and the radioactive waste liquid supply pipe and the α nuclide removal device, and It is desirable that the magnetic susceptibility measuring device is provided in the α nuclide removal device.

(B4) Preferably, in (B1) above, the injection of the pH adjuster into the radioactive waste liquid is performed when the desired concentration of α nuclides is reached.

(B5) Preferably, in (B4) above, the α nuclide concentration is further measured by analyzing a radioactive waste liquid sampled by a sampling valve attached to a pipe upstream of the pH adjuster injector. is desirable.

(B6) Preferably, in (B1) above, an adsorbent separation device is provided for separating the α-nuclide adsorbent from the radioactive waste liquid containing the α-nuclide adsorbent.

(B7) Preferably, in (B6) above, the adsorbent separation device is configured to separate the α nuclide adsorbent by a cross-flow method using a membrane having a pore size on the order of μm.

In the radioactive waste liquid treatment method and the radioactive waste liquid treatment system described above, for example, ferrite (Fe ₃ O ₄ ) or activated carbon can be used as the α-nuclide adsorbent.
Note that the α-nuclide adsorbent is not limited to the ferrite or activated carbon described above, and any adsorbent capable of adsorbing α-nuclides can be used as the α-nuclide adsorbent.

The α-nuclide adsorbent, particularly the ferrite described above, varies in its ability to adsorb α-nuclides (adsorption performance) depending on the pH of the radioactive waste liquid. Therefore, if the radioactive waste liquid is kept within a specific pH range, the adsorption performance can be sufficiently exhibited.
According to the radioactive waste liquid treatment method and the radioactive waste liquid treatment system described above, since the pH adjuster is injected into the radioactive waste liquid containing α nuclides, the pH of the radioactive waste liquid can be adjusted. The pH can be within the range where the adsorption performance of the α-nuclide adsorbent can be fully exhibited.
As a result, the extra-half-life alpha nuclides contained in the radioactive waste liquid can be easily removed by the alpha nuclide adsorbent, and the alpha nuclides contained in the radioactive waste liquid after removing the alpha nuclides are significantly reduced, so the alpha nuclides are adsorbed. The amount of used α-nuclide adsorbent that has been used is reduced. As a result, the amount of radioactive waste containing alpha nuclides generated can be reduced.

Furthermore, according to the radioactive waste liquid treatment method and the radioactive waste liquid treatment system described above, the α nuclides are adsorbed by the α nuclide adsorbent injected into the radioactive waste liquid, and the α nuclides are removed from the radioactive waste liquid containing the α nuclides.
Since the α-nuclide adsorbent is injected into the radioactive waste liquid, the particles of the α-nuclide adsorbent can be made finer and the specific surface area of the α-nuclide adsorbent can be increased. It is possible to control the time Thereby, it is possible to control the α-nuclide adsorbent to be immersed in the radioactive waste liquid until the desired α-nuclide adsorption amount is reached.
Therefore, the α-nuclide removal performance of the α-nuclide adsorbent can be improved, and the amount of generated radioactive waste containing α-nuclides can be further reduced.
And even compared with the configuration in which the absorption tower is filled with the α-nuclide adsorbent and the layer of the α-nuclide adsorbent is formed in the absorption tower, the α-nuclide removal performance is improved, and the radioactive waste containing α-nuclides It becomes possible to reduce the amount of generation.

Examples of the present invention will be described below.

(Example 1)
A method for treating radioactive waste liquid in Example 1 will be described with reference to FIGS. 1 to 6. FIG.
Example 1 is a radioactive liquid waste treatment method applied to the treatment of radioactive organic waste generated in a boiling water nuclear power plant.

First, with reference to FIG. 1, the outline of the radioactive waste liquid treatment method of the present embodiment will be described. FIG. 1 is a flow chart showing the procedure of the radioactive waste liquid treatment method of Example 1. FIG.

Fuel rods contained in fuel assemblies loaded into the reactor core in the reactor pressure vessel of a nuclear plant, e.g., a boiling water nuclear plant undergoing operation, or spent fuel assemblies stored in a fuel storage pool In the unlikely event that the cladding tube is damaged, the nuclear fuel material (including alpha nuclides such as uranium, plutonium, neptunium and curium) in the fuel rod will be released into the cooling water in the reactor pressure vessel or the fuel storage pool. It leaks into the cooling water inside. The alpha nuclides that have leaked into the cooling water in the reactor pressure vessel are removed by the ion exchange resin in the purification device of the reactor coolant purification system. Also, the alpha nuclides that have leaked into the cooling water in the fuel storage pool are removed by the ion exchange resin in the purification device of the fuel pool coolant purification system.

Filter sludge (radioactive organic waste) containing cellulosic filter aids, ion-exchange resins, etc. generated from the reactor coolant purification system and fuel pool coolant purification system of boiling water nuclear power plants is It is stored in storage tanks for a long period of time. The radioactive organic waste stored in the high dose resin storage tank is removed from the high dose resin storage tank after a predetermined storage period has elapsed.

A first washing step (crud dissolving step) S1 shown in FIG. 1 is performed on the radioactive organic waste containing the cation exchange resin taken out from the high-dose resin storage tank.
In this first washing step S1, an aqueous solution of a reducing organic acid (for example, an aqueous solution of oxalic acid) is brought into contact with the radioactive organic waste, and the organic acid contained in the aqueous solution oxidizes the iron contained in the radioactive organic waste. A crud such as an object is dissolved. Radionuclides such as cobalt-60 contained in the clad migrate into the organic acid aqueous solution by dissolving the clad.
The reason why the organic acid is used in the first cleaning step S1 is that the main constituent elements of the organic acid are carbon, hydrogen, oxygen and nitrogen. This is because no non-volatile residue is generated in the waste liquid when the oxidation treatment (waste liquid decomposition step S4 described later) is performed using ozone. As the organic acid, it is desirable to use formic acid, oxalic acid, acetic acid or citric acid, for example.

The waste liquid decomposition step S4 is carried out on the organic acid aqueous solution (cladding solution), which is the cleaning waste liquid containing the dissolution component of the clad generated in the first cleaning step S1.
In this waste liquid decomposition step (decomposition step for either organic acid or organic acid salt) S4, an oxidizing agent such as hydrogen peroxide or ozone is aerated into the organic acid aqueous solution, and the organic acid is decomposed by the oxidizing action of the oxidizing agent. be done.

A second washing step (radionuclide elution step) S2 is performed on the radioactive organic waste in which the clad has been dissolved after the first washing step S1.
In this second washing step S2, the organic acid salt aqueous solution is brought into contact with the radioactive organic waste in which the clad is dissolved, and the organic acid salt contained in the aqueous solution causes radioactive alpha nuclides such as α nuclides adsorbed to the radioactive organic waste. Nuclides are eluted.
The organic acid salt used in the second washing step S2 is desirably an organic acid salt that dissociates in an aqueous solution and produces cations that are more likely to be adsorbed by the cation exchange resin than hydrogen ions. That is, the main constituent elements of the organic acid salt are carbon, hydrogen, oxygen and nitrogen, and after the second cleaning step S2, the organic acid salt aqueous solution, which is the cleaning waste liquid, is oxidized using, for example, ozone. It is desirable that the waste liquid does not leave a non-volatile residue when the (waste liquid decomposition step S4) is carried out. As organic acid salts, it is desirable to use, for example, ammonium salts, barium salts or cesium salts of formic acid, oxalic acid, acetic acid or citric acid. Hydrazine formate may be used as the organic acid salt.
Ammonium salts are decomposed into nitrogen gas and water by oxidation treatment, so that the amount of radioactive waste generated can be reduced compared to barium salts and cesium salts. Ammonium, barium or cesium salts of formic acid, oxalic acid, acetic acid or citric acid dissociate in aqueous solutions to NH4 ⁺ , Ba2 ⁺ or Cs ⁺ . NH ⁴⁺ , Ba ²⁺ or Cs ⁺ are cations that are more likely to be adsorbed on cation exchange resins than hydrogen ions.

The waste liquid decomposition step S4 is performed on the organic acid salt aqueous solution, which is the washing waste liquid and contains the eluted radionuclides such as α nuclides generated in the second washing step S2. In the waste liquid decomposition step (decomposition step for either organic acid or organic acid salt) S4, an oxidizing agent such as ozone or hydrogen peroxide is aerated into the organic acid salt aqueous solution, and the organic acid salt is decomposed by the oxidizing agent. .

A pH adjuster is injected into the residual aqueous solution containing radionuclides (radioactive waste liquid) left after the organic acid or organic acid salt is decomposed in the waste liquid decomposition step S4 (pH adjuster injection step S5).
Here, a reducing agent such as hydrazine can be used as the pH adjuster.
By the pH adjusting agent injection step S5, the residual aqueous solution, that is, the radioactive waste liquid is adjusted to pH 4 to 11 (4 to 11 or less), for example 6. Then, in the reducing radioactive waste liquid containing a reducing agent (e.g., hydrazine) that is a pH adjuster, the valence of each of the above-mentioned α nuclides (uranium, plutonium, americium, neptunium, curium, etc.) becomes "3". Become.

The α nuclide removal step S6 is performed on the residual aqueous solution (radioactive waste liquid) containing the radionuclide into which the pH adjuster was injected in the pH adjuster injection step S5.
In the α-nuclide removal step S6, ferrite (Fe ₃ O ₄ ), which is an α-nuclide adsorbent, is supplied to the radioactive waste liquid containing α-nuclides whose valence is controlled to be “3”, and the ferrite reduces the valence to “3”. 3' controlled alpha nuclides are adsorbed and removed from the radioactive effluent.

Here, the results of experiments on removal of α nuclides will be described with reference to FIG. FIG. 5 shows the relationship between the removal methods (A, B, and C) of the α-nuclides contained in the radioactive waste liquid and the residual rate of the α-nuclides in the radioactive waste liquid after each removal method.
In "A" shown in FIG. 5, the α nuclide, for example, americium, adsorbed on the cation exchange resin is eluted with an aqueous solution of ammonium oxalate, which is an organic acid salt solution, and the ammonia oxalate contained in the aqueous solution of ammonia oxalate is eluted with ozone. This is the case where the water containing americium (in an untreated state) is discharged as it is without removing the eluted americium (concentration on the order of ppb). Therefore, in "A", the uranium residue rate (α nuclide residue rate) in the discharged water is 100%.
"B" shown in FIG. 5 is the case where the ammonium oxalate in the eluted ammonium oxalate aqueous solution containing uranium is decomposed with ozone, and ferrite (Fe ₃ O ₄ ) is supplied to the water containing americium produced by this decomposition. is. The ratio of the americium concentration of the water after supplying the ferrite to the americium concentration of the water before supplying the ferrite is the americium residual ratio, that is, the α nuclide residual ratio. The americium concentration of the water before the ferrite feed is the same as the americium concentration of the water in "A". In "B", the uranium retention rate (α nuclide retention rate) is 25%, which is 1/4 of "A".
"C" shown in FIG. 5 is an eluted ammonium oxalate aqueous solution containing americium that is decomposed with ozone, and hydrazine as a reducing agent is injected into the water containing americium generated by this decomposition to is adjusted to pH 8 within the range of 4 to 11, and ferrite (Fe ₃ O ₄ ) is supplied to water containing americium with pH 8. The americium concentration of the water before supplying ferrite at "C" is also the same as the americium concentration of the water at "A". In "C", the americium residual ratio (α nuclide residual ratio) is about 6.7%, which is about 1/15 of "A".
Therefore, a pH adjuster is injected into water containing α nuclides after organic acid salt decomposition to adjust the pH of the water to a range of 4 to 11, and ferrite is supplied to the pH-adjusted water containing α nuclides. It was found that the alpha nuclides contained in the water can be remarkably removed by

In the α-nuclide removal step S6, the pH adjuster, for example, the reducing agent injected into the radioactive waste liquid before the injection of the α-nuclide adsorbent is discharged while being contained in the radioactive waste liquid.

In the adsorbent separation step S7 following the α nuclide removal step S6, the adsorbent is separated from the radioactive waste liquid.
Thereafter, it is determined whether the pH adjuster injected into the radioactive waste liquid is a reducing agent (pH adjuster determination step S8). When the pH adjuster is a reducing agent, the determination is "YES", and the radioactive waste liquid containing the reducing agent discharged from the α-nuclide removal device is supplied to a decomposition device having a catalyst (e.g., precious metal), and the The reducing agent is decomposed in the decomposition device by the action of the catalyst and the oxidizing agent (for example, hydrogen peroxide) supplied to the decomposition device (reducing agent decomposition step S9). Note that when an acid (for example, a diluted nitric acid aqueous solution) is injected into the radioactive waste liquid as a pH adjuster, the above determination becomes "No" and the reducing agent decomposition step S9 is not performed.

In the volume reduction step S10, the radioactive waste liquid containing no reducing agent (including the radioactive waste liquid containing the injected acid) is subjected to a concentration treatment or a dry powderization treatment.
In the container filling or solidification step S11, the concentrated waste liquid generated by the concentration process or the powder of radioactive waste generated by the dry powderization process is filled and stored in a container, or is solidified with a solid agent such as cement. solidified inside.

Next, an example of the structure of a radioactive waste liquid treatment system used in a radioactive waste liquid treatment method including steps S1 to S11 of the first embodiment will be described with reference to FIG. FIG. 2 is a configuration diagram of an example of a radioactive waste liquid treatment system that executes the radioactive waste liquid treatment method of the first embodiment.

The radioactive waste liquid treatment system 1 shown in FIG. 2 includes a chemical cleaning unit 10 that processes radioactive organic waste, and a waste liquid processing unit 19 that processes cleaning waste liquid (radioactive liquid waste) discharged from the chemical cleaning unit 10.

In the chemical cleaning section 10, among the steps shown in FIG. 1, the first cleaning step S1 for dissolving the crud and the second cleaning step S2 for eluting radionuclides from the radioactive organic waste are performed.
The chemical cleaning section 10 has a first receiving tank 3 , a chemical reaction tank (cleaning tank) 4 , a cleaning liquid supply tank 6 , an organic acid tank 7 , an organic acid salt tank 8 and a transfer tank 9 . In addition, a high-dose resin storage tank 2 is provided in front of the chemical cleaning unit 10, and a second receiving tank 11 and an incineration facility (or cement solidification facility) 12 are provided below the chemical cleaning unit 10 in the drawing. .
An organic waste feed line 23 equipped with a transfer pump 22 connects the high dose resin storage tank 2 and the first receiving tank 3 .
The chemical reaction vessel 4 is connected to the first receiving tank 3 by an organic waste transfer pipe 25 provided with a transfer pump 24 . A heating device 5 is arranged around the chemical reaction tank 4 .
The cleaning liquid supply tank 6 is connected to the chemical reaction tank 4 by a cleaning liquid supply pipe 33 provided with a transfer pump 32 .
A return pipe 36 connected to the bottom of the chemical reaction tank 4 and provided with a transfer pump 34 and a valve 35 is connected to the cleaning liquid supply tank 6 .
A pipe 29 connected to an organic acid bath 7 filled with an aqueous solution of organic acid, for example, an aqueous solution of oxalic acid and provided with a valve 26 is connected to the cleaning liquid supply tank 6 . The oxalic acid aqueous solution filled in the organic acid bath 7 is a saturated aqueous solution, and the oxalic acid concentration of the oxalic acid aqueous solution is, for example, 0.8 mol/L.
A pipe 30 connected to an organic acid salt bath 8 filled with an aqueous organic acid salt solution, for example, an aqueous solution of hydrazine formate and provided with a valve 27 is connected to a pipe 29 downstream of the valve 26 .
A pipe 31 connected to a transfer water tank 9 filled with water to be transferred and provided with a valve 28 is connected to a pipe 30 downstream of the valve 27 .
A pipe 38 provided with a valve 37 and connected to the bottom of the chemical reaction tank 4 is connected to the second receiving tank 11 .
A pipe connected to the second receiving tank 11 is connected to an incineration facility (or cement solidification facility) 12 .

In addition, the waste liquid processing unit 19 includes a waste liquid decomposition device 13, an α-nuclide removal device 14, a pH adjuster injection device 112, an adsorbent injection device 121, an adsorbent separation device 131, a decomposition device 107, an oxidant supply device 108, and treated water. It has a recovery tank 18 .
A waste liquid supply pipe 40 connected to a return line 36 between a transfer pump 34 and a valve 35 and provided with a valve 39 is connected to the waste liquid decomposition device 13 .
A pipe 45 provided with a transfer pump 43 and a valve 44 is connected to the waste liquid decomposition device 13 and the α nuclide removal device 14 . The aforementioned "radioactive waste liquid supply pipe for guiding the radioactive waste liquid containing α nuclides" corresponds to the piping such as the piping 45 and the like.
A pipe 46 is connected to the α nuclide removal device 14 , the adsorbent separation device 131 , the decomposition device 107 and the treated water recovery tank 18 .
The pH adjusting agent injection device 112 is connected to the pipe 45 between the waste liquid decomposition device 13 and the α nuclide removal device 14 .
The adsorbent injection device 121 is connected to the α nuclide removal device 14 .
In the adsorbent separation device 131, the radioactive waste liquid is filtered by, for example, a cross-flow filter system using a membrane having a pore size of μm order or less, and the α-nuclide adsorbent that adsorbs the α-nuclides is separated from the radioactive waste liquid.
A pipe 55 connected between the transfer pump 34 and the valve 35 of the return pipe 36 of the chemical cleaning unit 10 is also connected to the adsorbent separation device 131 . The filtered water from which the adsorbent is separated by filtration in the adsorbent separation device 131 returns to the return pipe 36 through the pipe 55 . Thereby, filtered water can be circulated as circulating water. In addition, valves (not shown) are provided on the upstream sides of the pipes 36 and 55 (the side of the chemical reaction tank 4 and the side of the adsorbent separation device 131) of the connecting portion between the return pipe 36 and the pipe 55 so that the chemical reaction tank 4 The water from the pipe 55 and the filtered water from the pipe 55 can be switched.
The decomposition device 107 is filled with an activated carbon catalyst in which, for example, ruthenium is impregnated on the surface of the activated carbon.
The oxidant supply device 108 has a chemical tank 109 and a supply pipe 110 . A chemical tank 109 is connected to the decomposition device 107 by a supply line 110 having a valve 111 . The chemical liquid tank 109 is filled with hydrogen peroxide as an oxidizing agent. As the oxidizing agent, ozone or water in which oxygen is dissolved may be used instead of hydrogen peroxide.

Further, a dry powderization device 20 and a solidification device 21 are provided downstream of the waste liquid processing section 19 .
A pipe 48 provided with a transfer pump 47 connects the treated water recovery tank 18 and the dry powderization device 20 .
A pipe 49 connected to the dry powderization device 20 is connected to the solidification equipment 21 .
Incidentally, instead of the drying and pulverizing device 20, a radioactive liquid waste concentrating device may be used.

Here, FIG. 3 shows a detailed configuration diagram of the waste liquid decomposition device 13 in the waste liquid treatment unit 19 of FIG. 2, and FIG. 4 shows a detailed configuration diagram of the α nuclide removal device 14. 3 and 4, pipes connected to the liquid waste decomposition device 13 and the α-nuclide removal device 14, components (tanks, devices, etc.) provided near the liquid waste decomposition device 13 and the α-nuclide removal device 14 is also shown.

As shown in FIG. 3, the waste liquid decomposition apparatus 13 is composed of a cleaning waste liquid processing tank, and an ozone injection pipe 81 is installed at the bottom of the cleaning waste liquid processing tank. A large number of injection holes are formed in the ozone injection pipe 81 . The ozone injection pipe 81 is connected to the ozone supply device 80 by an ozone supply pipe 82 .
A pipe 40 from the chemical cleaning unit 10 shown in FIG. Also, the pipe 45 connected to the α-nuclide removal device 14 and the adsorbent separation device 131 shown in FIG. Furthermore, a gas exhaust pipe 83 is connected to the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 .
By supplying ozone from the ozone supply device 80 through the ozone supply pipe 82 , ozone is injected from the injection hole of the ozone injection pipe 81 into the radioactive waste liquid in the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 . As a result, oxalic acid, formic acid, hydrazine, and the like in the radioactive waste liquid are decomposed by the injected ozone. The generated gas is discharged through a gas exhaust pipe 83 . The treated water is sent to the α-nuclide removal device 14 through the pipe 45 .

As shown in FIG. 4 , a pH adjuster injection device 112 is connected to a pipe 45 connected to the α-nuclide removal device 14 .
The α-nuclide removal device 14 is composed of a liquid waste treatment tank that accommodates the radioactive waste liquid sent from the liquid waste decomposition device 13 through the pipe 45 .
The pH adjuster injection device 112 has a reducing agent injection device 17 and an acid injection device 113 .
The reducing agent injection device 17 has a reducing agent tank 17A and an injection pipe 42 provided with a valve 41 . The reducing agent tank 17A is filled with a reducing agent aqueous solution, for example, a hydrazine aqueous solution.
The injection pipe 42 is connected to the reducing agent tank 17A and further connected to a pipe 45 between the waste liquid decomposition device 13 and the valve 44 (see FIG. 2 for each).
The acid injection device 113 has an acid bath 114 and an injection line 116 provided with a valve 115 . The acid bath 114 is filled with an acid aqueous solution, for example, a diluted nitric acid aqueous solution.
Injection line 116 is connected to acid bath 114 and downstream of valve 41 to injection line 42 .
A pH meter 49 is attached to the pipe 45 at a portion of the pipe 45 between the connecting point of the injection pipe 42 and the pipe 45 connected to the reducing agent injection device 17 and the α nuclide removal device 14 .

As shown in FIG. 4, one end of an injection pipe 123 provided with a valve 122 is connected to the adsorbent injection device 121 . The adsorbent injection device 121 is filled with α-nuclide adsorbent such as ferrite (Fe ₃ O ₄ ) particles.
The other end of the injection pipe 123 is connected to the α nuclide removal device 14 .
The adsorbent can be injected from the adsorbent injection device 121 into the radioactive waste liquid in the waste liquid treatment tank of the α nuclide removal device 14 through the injection pipe 123 .
In addition, a magnetic susceptibility measuring device 49B is installed in the outer surface downstream portion of the casing of the α nuclide removal device 14 .

In the α-nuclide removal device 14 , an adsorbent pulverized to a particle size of μm order is injected from an adsorbent injection device 121 through an injection pipe 123 . As a result, the specific surface area of the adsorbent is increased as compared with a granular adsorbent of several hundred μm order.

Here, the effect of the specific surface area of the adsorbent on the removal rate of α nuclides in the radioactive waste liquid will be described with reference to FIG. FIG. 6 shows the relationship between the size of the adsorbent and the amount of α nuclides adsorbed per 1 g of the adsorbent.
FIG. 6 compares the size of the adsorbent between granular (particle size >100 μm) and fine powder (particle size <1 μm).
As shown in FIG. 6, when the adsorbent is finely powdered, the α nuclide adsorption amount per 1 g of the adsorbent is improved by 100 times or more compared to when the adsorbent is granular.

In addition, by injecting the adsorbent into the α-nuclide removal device 14, it is possible to control the time during which the adsorbent is immersed in the radioactive waste liquid, unlike the method of passing water through an adsorption tower filled with adsorbent. . Thereby, it is possible to control the α-nuclide adsorbent to be immersed in the radioactive waste liquid until the desired α-nuclide adsorption amount is reached. Then, after the adsorbent is immersed for a desired time to achieve the desired α-nuclide adsorption amount, water can be passed from the α-nuclide removal device 14 to the adsorbent separation device 131 . Therefore, radioactive waste containing alpha nuclides can be reduced.

Next, a detailed description will be given of the radioactive liquid waste treatment method of the present embodiment using the radioactive liquid waste treatment system 1 shown in FIG.
Radioactive organic waste discharged from the reactor coolant cleanup system, fuel pool cooling cleanup system, etc. of a boiling water nuclear power plant and stored in the high-dose resin storage tank 2 for a predetermined long period is treated with a cellulosic filter aid. materials, ion exchange resins, etc. The radioactive organic waste stored in the high-dose resin storage tank 2 is made into a slurry state that is easy to transfer, for example, by supplying water from the transfer water tank to the high-dose resin storage tank 2 through a transfer water supply pipe. Become.
The radioactive organic waste stored in the high-dose resin storage tank 2 contains clad that has been removed from cooling water by the reactor coolant cleanup system, the fuel pool cooling cleanup system, etc. The clad contains cobalt-60 It contains radionuclides such as The ion exchange resin stored in the high-dose resin storage tank 2 adsorbs ions of radionuclides other than α nuclides, such as cobalt-60, cesium-137, carbon-14, and chlorine-36. Furthermore, the ion exchange resin adsorbs α nuclides (uranium, plutonium, americium, neptunium, curium, etc.) as described above.

By driving the transfer pump 22, a predetermined amount of slurry containing radioactive organic waste (for example, at a concentration of about 10 wt%) is transferred from the high-dose resin storage tank 2 through the organic waste supply pipe 23 to the chemical reaction tank 4. be transported. When the water level of the radioactive organic waste slurry in the chemical reaction tank 4 reaches a predetermined level, the transfer pump 22 is stopped and the supply of the slurry to the chemical reaction tank 4 is stopped.
After that, the transfer pump 34 is driven, and the water contained in the slurry in the chemical reaction tank 4 is discharged as a radioactive waste liquid (hereinafter referred to as "third radioactive waste liquid") through the return pipe 36 and the pipe 40 to the waste liquid decomposition device 13. is guided to the washing waste liquid treatment tank. At this time, valve 35 is closed and valve 39 is open. The third radioactive waste liquid led to the washing waste liquid treatment tank is driven by the transfer pump 43 and is led to the α-nuclide removal device 14 through the pipe 45 . In the chemical reaction tank 4, the water contained in the radioactive organic waste slurry does not contain α-nuclides, so the third radioactive waste liquid in the cleaning waste liquid treatment tank does not contain α-nuclides and does not contain radioactive substances other than α-nuclides. Contains nuclides.
The third radioactive liquid waste passes through the α-nuclide removal device 14 , is discharged to the pipe 46 and is led to the treated water recovery tank 18 . When the third radioactive waste liquid is supplied to the α-nuclide removal device 14, the ferrite (Fe ₃ O ₄ ) particles in the α-nuclide removal device 14 do not adsorb α-nuclides and radionuclides other than α-nuclides. Colloidal substances and solids contained in the third radioactive waste liquid are removed by the filter effect of ferrite. Since the third radioactive waste liquid does not contain α nuclides, the injection of the pH adjuster aqueous solution (hydrazine aqueous solution or dilute nitric acid aqueous solution) from the pH adjuster injection device 112 to the pipe 45 in the pH adjuster injection step S5 is not performed, and the reduction Also, the reducing agent (for example, hydrazine) is not decomposed in the agent decomposition step S9.

When the transfer of the third radioactive waste liquid in the washing waste liquid treatment tank to the α-nuclide removal device 14 is completed, the transfer pump 43 is stopped. A predetermined amount of the third radioactive waste liquid in the treated water recovery tank 18 is supplied to the dry powderization device 20 through the pipe 48 by driving the transfer pump 47 . The third radioactive waste liquid containing radionuclides other than α nuclides is pulverized by the drying and pulverizing device 20 (volume reduction step S10).
After that, the powder produced by the dry powderization device 20 is transferred to the solidification equipment 21 (or filling equipment). In the solidification equipment 21, the powder is filled in a solidification container, and a solidification material (for example, cement) is injected into the solidification container. The powder in the solidification container is solidified by the solidification material (container filling or solidification step S11). The solidified powder is present inside and the sealed solidification container is stored in a storage location. No long-lived alpha nuclides are present in this stored solidification container. Moreover, when using the filling equipment, the powder is filled in the container, and after the container filled with the powder is sealed, the container is stored in the storage place.

By driving the transfer pump 32, an oxalic acid aqueous solution of about 72 g/L (oxalic acid concentration of 0.8 mol /L) is supplied from the cleaning liquid supply tank 6 through the cleaning liquid supply pipe 33 . An aqueous oxalic acid solution having an oxalic acid concentration of 0.8 mol/L is supplied from the organic acid tank 7 to the cleaning liquid supply tank 6 through a pipe 29 by opening a valve 26 . At this time, the valves 27 and 28 are fully closed. A citric acid aqueous solution may be used instead of the oxalic acid aqueous solution. These organic acids have reducing properties.

The oxalic acid aqueous solution in the chemical reaction tank 4 is heated by the heating device 5 . The heating temperature of the oxalic acid aqueous solution is less than 100°C. The oxalic acid contained in the oxalic acid aqueous solution supplied into the chemical reaction tank 4 dissolves the crud adhering to the radioactive organic waste in the chemical reaction tank 4 (first cleaning step S1). Due to the dissolution of the clad, radionuclides contained in the clad, eg, cobalt-60, migrate into the aqueous oxalic acid solution.
The crud components contained in the aqueous oxalic acid solution, which are generated by the dissolution of the crud by the aqueous oxalic acid solution in the chemical reaction bath 4, are precipitated in the chemical reaction bath 4. Only the oxalic acid aqueous solution, which is the supernatant liquid in the chemical reaction tank 4 caused by the sedimentation of the components dissolved in the crud, is recovered to the cleaning liquid supply tank 6 through the return pipe 36 by driving the transfer pump 34 . At this time, valve 39 is closed and valve 35 is open. The oxalic acid aqueous solution recovered in the cleaning liquid supply tank 6 is supplied to the chemical reaction tank 4 and reused in the chemical reaction tank 4 for dissolving the crud.
In the first washing step S1, the ion exchange resin, which is part of the radioactive organic waste, is immersed in oxalic acid, which is an organic acid. is detached from Specifically, hydrogen ions and oxalate ions generated by the dissociation of oxalic acid are ion-exchanged with radionuclides adsorbed on the cation exchange resin and anion exchange resin, respectively, so some radionuclides ( alpha nuclides and radionuclides other than alpha nuclides) are desorbed from the ion exchange resin.

After finishing the dissolution of the crud in the chemical reaction tank 4, the valve 35 is closed and the valve 39 is opened. Ion exchange with the above-mentioned hydrogen ions and oxalate ions generated by the dissociation of radionuclides (e.g., cobalt 60) and oxalic acid used for dissolving the crud and contained in the crud in the chemical reaction tank 4 Oxalic acid aqueous solution containing some radionuclides (α nuclides and radionuclides other than α nuclides, respectively) desorbed from the cation exchange resin and anion exchange resin, respectively, which are part of the radioactive organic waste by (hereinafter referred to as "first radioactive liquid waste") is transferred to the cleaning liquid waste treatment tank of the liquid waste decomposition apparatus 13 through the pipes 36 and 40 by driving the transfer pump 34. As shown in FIG. The waste liquid decomposition device 13 has an ozone supply device 80, an ozone injection pipe 81, an ozone supply pipe 82 and a gas exhaust pipe 83, as shown in FIG.

After the transfer of the oxalic acid aqueous solution to the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 is completed, the waste liquid decomposition step S4 is carried out. In the waste liquid decomposition step S4, ozone is supplied from the ozone supply device 80 through the ozone supply pipe 82 to the ozone injection pipe 81 in the cleaning waste liquid treatment tank for a predetermined period of time. , is sprayed into the oxalic acid aqueous solution in the washing waste liquid treatment tank. Oxalic acid, which is an organic component contained in the oxalic acid aqueous solution, is decomposed by the injected ozone. Oxalic acid reacts with ozone and decomposes into carbon dioxide gas and water. The remaining ozone and carbon dioxide gas sprayed into the waste cleaning liquid treatment tank are supplied to an off-gas treatment device (not shown) through a gas exhaust pipe 83 connected to the waste cleaning liquid treatment tank and discharged through the gas exhaust pipe 83. Radioactive gases contained in the discharged gas are removed in an off-gas treatment unit.

After the decomposition of oxalic acid contained in the oxalic acid aqueous solution (waste liquid decomposition step S4) in the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 is completed, the supply of ozone to the cleaning waste liquid treatment tank is stopped and the transfer pump 43 is turned on. is driven, and an aqueous solution containing each of the detached α-nuclides and radionuclides other than α-nuclides remaining in the cleaning waste liquid treatment tank after oxalic acid decomposition, that is, the first radioactive waste liquid is sent through the pipe 45 to α It is supplied to the nuclide removal device 14 . At this time, the valve 44 is open.

After the waste liquid decomposition step S4 described above, the pH adjuster is injected into the pipe 45 from the pH adjuster injection device 112 in order to perform the pH adjuster injection step S5.
In this embodiment, either a reducing agent or an acid is used as the pH adjuster injected into the pipe 45 .
As the reducing agent, for example, hydrazine, formhydrazine, hydrazine derivatives such as hydrazine carboxamide and carbohydrazide, and hydroxylamine are used.
As the acid, for example, either dilute nitric acid or oxalic acid is used.

In this embodiment, when the pH of the first radioactive waste liquid containing α nuclides is adjusted to a pH within the range of 4 to 7 within the range of 4 to 11 (4 to 7), as a pH adjuster, Acid (eg, dilute nitric acid) is injected into the radioactive effluent. When adjusting the pH to within the range of 4 to 7 (4 or more and 7 or less), the acid injected into the first radioactive waste liquid includes an acid that cannot be decomposed (e.g., diluted nitric acid) and an acid that can be decomposed. (e.g. oxalic acid).
In addition, in the present embodiment, when the pH of the first radioactive waste liquid is adjusted to a range of more than 7 and less than or equal to 11 within the range of 4 or more and 11 or less, a reducing agent ( hydrazine) is injected.

In the present embodiment, the pH of the first radioactive waste liquid containing α-nuclides, which is supplied to the α-nuclide removal device 14, is set to, for example, the set pH of "8".
In this case, in the pH adjuster injection device 112, the valve 41 is opened to inject the reducing agent aqueous solution, for example hydrazine aqueous solution, filled in the reducing agent tank 17A of the reducing agent injection device 17 through the injection pipe 42 into the pipe 45. (pH adjuster injection step S5). The injected hydrazine aqueous solution is mixed with the first radioactive waste liquid in the pipe 45 .
The first radioactive waste liquid containing injected hydrazine flows into the α-nuclide removal device 14 . The hydrazine injection adjusts the pH of the first radioactive effluent to within the range of 4-11, eg, 8. The pH of the first radioactive waste liquid flowing into the α-nuclide removal device 14 is measured with a pH meter 49A. The opening of the valve 41 is controlled based on the measured value of the pH meter 49A, and the amount of hydrazine aqueous solution supplied from the reducing agent tank 17A to the pipe 45 is adjusted so that the pH of the first radioactive waste liquid becomes 8. At this time, the valve 115 is closed. The pH of the first radioactive waste liquid is, for example, 6 before it flows into the α-nuclide removal device 14, specifically, before the hydrazine aqueous solution is injected.
The first radioactive waste liquid contains hydrazine as a reducing agent, and the hydrazine adjusts the pH of the first radioactive waste liquid to within the range of 4 to 11, for example, 8, so the valence contained in the first radioactive waste liquid is "3 to 5" (uranium, plutonium, neptunium, curium, etc.) is adjusted to "3".

Ferrite is supplied as an adsorbent to the first radioactive waste liquid containing each α-nuclide with a valence of "3". By opening the valve 122 , ferrite is supplied from the adsorbent injection device 121 to the α nuclide removal device 14 through the injection pipe 123 . In the presence of a reducing agent (e.g., hydrazine), each α-nuclide contained in the first radioactive waste liquid and having its valence adjusted to "3" is efficiently adsorbed to ferrite particles and removed (α-nuclide removal step S6). Solids contained in the first radioactive waste liquid are removed by ferrite. Magnetic susceptibility measurement device 49B provided in α-nuclide removal device 14 detects whether ferrite exists in α-nuclide removal device 14 .

The ferrite in which α nuclides have been adsorbed in the α nuclide removal device 14 is discharged from the α nuclide removal device 14 as used ferrite together with the first radioactive waste liquid, and supplied to the adsorbent separation device 131 through the pipe 46.
In the adsorbent separation device 131, for example, the first radioactive waste liquid is filtered by a cross-flow filter method using a membrane having a pore size of μm order or less to separate the ferrite on which the α nuclide is adsorbed (adsorbent separation step S7).
The first radioactive waste liquid from which the α-nuclides-adsorbed ferrite has been separated is discharged from the adsorbent separator 131 to the pipe 46 .
In the adsorbent separation device 131 , the filtrate filtered by the membrane is supplied to the return line 36 through the line 55 .

In this case, since hydrazine, which is a reducing agent, is injected in the pH adjuster injection step S5, the determination of "is the pH adjuster a reducing agent?" The hydrazine-containing first radioactive waste liquid from which α-nuclides, colloidal substances and solids have been removed by the ferrite of the α-nuclide removal device 14 is led from the adsorbent separation device 131 to the decomposition device 107 through the pipe 46.
Hydrazine (reducing agent) contained in the first radioactive waste liquid is decomposed in the decomposition device 107 . That is, the valve 111 is opened to supply the hydrogen peroxide in the chemical liquid tank 109 to the decomposition device 107 through the supply pipe 110 . In the decomposition device 107, hydrazine contained in the first radioactive waste liquid is decomposed into nitrogen and water by the action of the activated carbon catalyst and hydrogen peroxide (reducing agent decomposition step S9).
The first radioactive waste liquid discharged from the decomposition device 107 and containing no alpha nuclides and hydrazine is guided to the treated water recovery tank 18 through the pipe 46 .

In addition, when the pH of the first radioactive waste liquid is set to, for example, 6, in the pH adjuster injection step S5, an acid aqueous solution (eg, diluted nitric acid aqueous solution) is injected from the pH adjuster injector 112 into the first radioactive waste liquid. be done. Injection of the dilute nitric acid aqueous solution from the pH adjuster injection device 112 is performed by opening the valve 115 and allowing the acid aqueous solution, for example, the dilute nitric acid aqueous solution, filled in the acid tank 114 of the acid injection device 113, to flow through the injection pipe 116 and the injection pipe 42. through and inject into the pipe 45 (pH adjuster injection step S5). At this time, the valve 41 is closed. The injected diluted nitric acid aqueous solution is mixed with the first radioactive waste liquid within the pipe 45 . The first radioactive waste liquid containing injected dilute nitric acid flows into the α nuclide removal device 14 . The opening of the valve 115 is controlled based on the pH of the first radioactive waste liquid measured by the pH meter 49A, and the pH of the first radioactive waste liquid is within the range of 4 to 11, for example, 6. Acid The amount of dilute nitric acid aqueous solution supplied from tank 114 to pipe 45 is adjusted. The pH of the first radioactive waste liquid is, for example, 8 before it flows into the α-nuclide removal device 14, specifically, before injection of the diluted nitric acid aqueous solution. The α nuclides contained in the first radioactive waste liquid adjusted to pH 6 by injecting the diluted nitric acid aqueous solution are removed by being adsorbed by the ferrite injected into the α nuclide removal device 14 (α nuclide removal step S6).

In the pH adjuster injection step S5, when the dilute nitric acid aqueous solution is injected into the first radioactive waste liquid, the determination in the pH adjuster determination step S8 becomes “No”, and the dilute The first radioactive waste liquid containing nitric acid is led to the decomposition device 107, but in this case, the valve 111 is kept closed, so the hydrogen peroxide in the chemical tank 109 is not supplied to the decomposition device 107. , the first radioactive waste liquid containing dilute nitric acid is directly discharged from the decomposition device 107 and led to the treated water recovery tank 18 .
The injection of dilute nitric acid, which is a pH adjuster, into the first radioactive solution described above can also be applied to Example 2 described later.

When the pH of the first radioactive waste liquid is set to, for example, 6, an oxalic acid aqueous solution can be used as the acid aqueous solution instead of the dilute nitric acid aqueous solution. At this time, the oxalic acid aqueous solution is injected from the acid tank 114 of the acid injector 113 into the pipe 45 through the injection pipe 116 and the injection pipe 42 (pH adjuster injection step S5). The α nuclides contained in the first radioactive waste liquid having a pH of 6 and containing oxalic acid are removed by being adsorbed by the ferrite injected into the α nuclide removal device 14 (α nuclide removal step S6).
However, when the oxalic acid aqueous solution is injected into the first radioactive waste liquid, the determination in the pH adjuster determining step S8 becomes "YES" because oxalic acid is the reducing agent. The first radioactive waste liquid containing oxalic acid discharged from the α nuclide removal device 14 is supplied to the decomposition device 107 , the valve 111 is opened, and the hydrogen peroxide in the chemical tank 109 is supplied to the decomposition device 107 . Oxalic acid (pH adjuster) contained in the first radioactive waste liquid is decomposed into carbon dioxide and water in the decomposer 107 by the action of the activated carbon catalyst and injected hydrogen peroxide. By decomposing the oxalic acid (pH adjuster) contained in the first radioactive waste liquid, the amount of the first radioactive waste liquid can be reduced. Such decomposition of oxalic acid contained in the first radioactive solution can also be applied when oxalic acid is injected into the first radioactive waste liquid in Example 2 below.

The first radioactive waste liquid (the first radioactive waste liquid in which hydrazine or oxalic acid is decomposed, or the first radioactive waste liquid containing dilute nitric acid) in the treated water recovery tank 18 described above is supplied to the drying and pulverizing device 20. Powdered (volume reduction step S10). The powder containing no alpha nuclides generated by the dry powderization device 20 is transferred to the solidification equipment 21 and filled in a solidification container, and solidified by injecting a solidification material into the solidification container (container filling or solidification step S11). After the solidification container is sealed, it is stored in a storage location. No long-lived alpha nuclides are present in this stored solidification container.
Here, when dilute nitric acid is injected into the first radioactive waste liquid, the powder produced by pulverization of this first radioactive waste liquid contains nitric acid components, and this powder is melted in the solidification container. A vitrified material produced by solidifying with glass also contains a nitric acid component.
On the other hand, when oxalic acid, which is a pH adjuster, is injected into the first radioactive waste liquid, as described above, the oxalic acid (pH adjuster) is decomposed, and the vitrified material produced is oxalic acid. Contains no acid.

In a state where the first radioactive waste liquid has been treated as described above and solidification has been performed in the solidification equipment 21, there is still radioactive organic waste containing a cation exchange resin in which the crud is dissolved in the chemical reaction tank 4. remains. Subsequently, the radioactive organic waste containing this cation exchange resin is treated.
By driving the transfer pump 32, a hydrazine formate aqueous solution of about 40 to 400 g/L is continuously supplied from the cleaning liquid supply tank 6 through the cleaning liquid supply pipe 33 into the chemical reaction tank 4 where the radioactive organic waste remains. The concentration of hydrazine formate in an aqueous solution of hydrazine formate is the mass of solute (hydrazine formate) per liter of solution. The hydrazine formate aqueous solution supplied to the chemical reaction tank 4 is a neutral liquid having a pH of about 7. The hydrazine formate aqueous solution is supplied from the organic acid salt tank 8 to the cleaning liquid supply tank 6 through the pipes 30 and 29 by opening the valve 27 . Valves 26 and 28 are closed.
The radioactive organic waste is brought into contact with the hydrazine formate aqueous solution in the chemical reaction tank 4 . In the chemical reaction tank 4, the α-nuclides uranium, plutonium, americium, neptunium, and curium, and the radionuclides other than α-nuclides, cobalt, are adsorbed on the cation exchange resin, which is the radioactive organic waste, due to this contact. 60, cesium-137, carbon-14, and chlorine-36 ions are eluted in the hydrazine formate aqueous solution (second washing step S2).
Only the aqueous hydrazine formate solution is recovered from the chemical reaction tank 4 , and the recovered aqueous hydrazine formate solution is transferred to the cleaning liquid supply tank 6 through the return pipe 36 . At this time, valve 35 is open and valve 39 is closed. The hydrazine formate aqueous solution transferred to the cleaning liquid supply tank 6 is again supplied to the chemical reaction tank 4 and used for elution of each radionuclide adsorbed on the cation exchange resin. An aqueous solution of hydrazine salt of any one of oxalic acid, acetic acid and citric acid may be used instead of the hydrazine formate aqueous solution. These organic acid salts are organic acid salts that yield cations that are more likely to be adsorbed to the cation exchange resin than hydrogen ions.

When an oxalic acid aqueous solution is brought into contact with a cation exchange resin, which is a radioactive organic waste, the decontamination performance (decontamination coefficient) for cobalt 60 adsorbed on the cation exchange resin is about DF4.
On the other hand, when the hydrazine formate aqueous solution was brought into contact with the cation exchange resin, the decontamination performance was DF20 or higher, and the decontamination performance was improved as compared with the case where the oxalic acid aqueous solution was brought into contact.
In order to obtain decontamination performance of DF20 or higher using only an oxalic acid aqueous solution, it is necessary to repeatedly add oxalic acid.
On the other hand, when hydrazine formate aqueous solution is used, the repetition is not required, and the amount of detergent used, that is, the amount of oxalic acid can be reduced.
Here, the decontamination coefficient DF is a numerical value calculated by (counting rate before decontamination)/(counting rate after decontamination). Decontamination with hydrazine formate (ion elution) is performed after decontamination with oxalic acid (crud dissolution). Therefore, when dissolving only the crud with an aqueous organic acid solution, ions are not eluted with an aqueous organic acid salt solution. only counting rate). On the other hand, when ions are also eluted, the decontamination factor DF is a value calculated by (counting rate before decontamination)/(counting rate after crud dissolution and ion elution).

After the elution of radionuclides in the chemical reaction tank 4 (second cleaning step S2) is completed, the valve 35 is closed, the valve 39 is opened, and the transfer pump 34 is driven. The hydrazine formate aqueous solution containing the eluted α-nuclides and radionuclides other than α-nuclides (hereinafter referred to as “second radioactive waste liquid”) in the chemical reaction tank 4 passes through the pipes 36 and 40 to the waste liquid decomposition apparatus described above. It is transferred to the cleaning waste liquid treatment tank No. 13.

After the transfer of the hydrazine formate aqueous solution to the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 is completed, the waste liquid decomposition step S4 is carried out. In this waste liquid decomposition step S4, ozone from the ozone supply device 80 is sprayed into the hydrazine formate aqueous solution in the cleaning waste liquid treatment tank of the waste liquid decomposition device 13. FIG. Formic acid and hydrazine contained in the hydrazine formate aqueous solution are decomposed by the injected ozone. Formic acid is decomposed into nitrogen gas and water, and hydrazine is decomposed into carbon dioxide and water. The remaining ozone, carbon dioxide gas and nitrogen gas injected into the waste cleaning liquid treatment tank are supplied to an offgas treatment device (not shown) through a gas exhaust pipe 83 connected to the waste cleaning liquid treatment tank.

After the decomposition of formic acid and hydrazine (waste liquid decomposition step S4) in the cleaning waste liquid treatment tank of the waste liquid decomposition device 13, which is performed after the second cleaning step S2, is completed, the waste liquid decomposition device 13 is discharged to the cleaning waste liquid treatment tank. The supply of ozone is stopped and the transfer pump 43 is driven, and the aqueous solution containing α-nuclides and radionuclides other than α-nuclides remaining in the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 after the decomposition of formic acid and hydrazine, that is, A second radioactive waste liquid is supplied to the α-nuclide removal device 14 through a pipe 45 . At this time, the valve 44 is open.

In this embodiment, when the pH of the second radioactive waste liquid containing α nuclides is adjusted to a pH within the range of 4 to 7 within the range of 4 or more and 11 or less (4 or more and 7 or less), the pH adjuster is An acid (eg, dilute nitric acid) is injected into the bi-radioactive effluent. When adjusting the pH to within the range of 4 to 7 (4 or more and 7 or less), the acid injected into the second radioactive waste liquid includes non-decomposable acid (e.g., dilute nitric acid) and decomposable acid. (e.g. oxalic acid).
In addition, in the present embodiment, when the pH of the second radioactive waste liquid is adjusted to within the range of 4 or more and 11 or less and within the range of more than 7 and 11 or less, a reducing agent ( hydrazine) is injected.

In the present embodiment, the pH of the second radioactive waste liquid containing α-nuclides supplied to the α-nuclide removal device 14 is set to, for example, the set pH of "8".
Since the second radioactive waste liquid containing α-nuclides is supplied to the α-nuclide removal device 14, the valve 41 is opened and the reducing agent aqueous solution, for example, hydrazine aqueous solution, filled in the reducing agent tank 17A of the reducing agent injection device 17 is It is injected into the pipe 45 through the injection pipe 42 (pH adjuster injection step S5). The injected hydrazine aqueous solution is mixed with the second radioactive waste liquid within the pipe 45 .
The second radioactive waste liquid containing injected hydrazine flows into the α nuclide removal device 14 . The injection of hydrazine adjusts the pH of the second radioactive effluent to within the range of 4-11, eg, 8. The pH of the second radioactive waste liquid flowing into the α-nuclide removal device 14 is also measured by the pH meter 49A. The opening of the valve 41 is controlled based on the measured value of the pH meter 49A, and the amount of hydrazine aqueous solution supplied from the reducing agent tank 17A to the pipe 45 is adjusted so that the pH of the second radioactive waste liquid becomes 8. The pH of the second radioactive waste liquid is, for example, 6 before it flows into the α-nuclide removal device 14 .
The second radioactive waste liquid contains hydrazine, and the hydrazine adjusts the pH of the second radioactive waste liquid to 8, so the valence of each α nuclide with a valence of "3 to 5" contained in the second radioactive waste liquid is adjusted to "3".

Each α-nuclide with a valence of "3" contained in the second radioactive waste liquid is removed by being efficiently adsorbed to ferrite particles in the α-nuclide removal device 14 in the presence of a reducing agent (α nuclide removal step S6). Colloidal substances and solids contained in the second radioactive waste liquid are also removed by the filtering effect of the ferrite. The existence of ferrite in the α nuclide removal device 14 can be confirmed based on the output of the magnetic susceptibility measurement device 49B.

The ferrite in which the α nuclides have been adsorbed in the α nuclide removal device 14 is discharged from the α nuclide removal device 14 as used ferrite together with the second radioactive waste liquid, and supplied to the adsorbent separation device 131 through the pipe 46.
In the adsorbent separation device 131, for example, the second radioactive waste liquid is filtered by a cross-flow filter method using a membrane having a pore size of μm order or less to separate the ferrite on which the α nuclide is adsorbed (adsorbent separation step S7).
The second radioactive waste liquid from which the α-nuclides-adsorbed ferrite has been separated is discharged from the adsorbent separation device 131 to the pipe 46 .
In the adsorbent separation device 131 , the filtrate filtered by the membrane is supplied to the return line 36 through the line 55 .

Since hydrazine, which is a reducing agent, is injected in the pH adjuster injection step S5, the determination in the pH adjuster determination step S8 is "YES", and the ferrite of the α nuclide removal device 14 extracts α nuclides and colloidal substances. The hydrazine-containing second radioactive waste liquid from which solids have been removed is led from the adsorbent separation device 131 to the decomposition device 107 through the pipe 46 .
The hydrazine contained in the second radioactive waste liquid is decomposed in the decomposition device 107 in the same manner as the hydrazine contained in the first radioactive waste liquid (reducing agent decomposition step S9).
The second radioactive waste liquid discharged from the decomposition device 107 and containing no alpha nuclides and hydrazine is guided to the treated water recovery tank 18 through the pipe 46 .

In addition, when the pH of the second radioactive waste liquid is set to 6, for example, similarly to the first radioactive waste liquid, in the pH adjuster injection step S5, the acid dilute nitric acid aqueous solution is injected from the pH adjuster injector 112 into the pH adjuster injection device 112. Two are injected into the radioactive effluent. The second radioactive waste liquid containing injected dilute nitric acid flows into the α nuclide removal device 14 . The α nuclides contained in the second radioactive waste liquid adjusted to pH 6 by injecting the diluted nitric acid aqueous solution are removed by being adsorbed by the ferrite injected into the α nuclide removal device 14 (α nuclide removal step S6).

In the pH adjuster injection step S5, when the dilute nitric acid aqueous solution is injected into the second radioactive waste liquid, the determination in the pH adjuster determination step S8 becomes “No”, and the dilute The second radioactive waste liquid containing nitric acid is not supplied with hydrogen peroxide from the chemical liquid tank 109 , passes through the decomposition device 107 as it is, and is led to the treated water recovery tank 18 .
The injection of dilute nitric acid, which is a pH adjuster, into the second radioactive solution described above can also be applied to Example 2 described later.

When the pH of the second radioactive waste liquid is set to, for example, 6, even when an oxalic acid aqueous solution is used as the acid aqueous solution, the oxalic acid aqueous solution is It is injected into the pipe 45 from the acid tank 114 of the acid injection device 113 (pH adjuster injection step S5). The α nuclides contained in the second radioactive waste liquid having a pH of 6 and containing oxalic acid are removed by being adsorbed by the ferrite injected into the α nuclide removal device 14 (α nuclide removal step S6).
However, when the oxalic acid aqueous solution is injected into the second radioactive waste liquid, the determination in the pH adjuster determination step S8 becomes "YES", and the second radioactive waste containing oxalic acid discharged from the α-nuclide removal device 14 The waste liquid is supplied to the decomposition device 107 , the valve 111 is opened, and the hydrogen peroxide in the chemical tank 109 is supplied to the decomposition device 107 . Oxalic acid (pH adjuster) contained in the second radioactive waste liquid is decomposed into carbon dioxide and water in the decomposer 107 by the action of the activated carbon catalyst and injected hydrogen peroxide. By decomposing the oxalic acid (pH adjuster) contained in the second radioactive waste liquid, the amount of the second radioactive waste liquid can be reduced. Such decomposition of oxalic acid contained in the second radioactive solution can also be applied when oxalic acid is injected into the second radioactive waste liquid in Example 2 described later.

As with the first radioactive waste liquid described above, the second radioactive waste liquid in the treated water recovery tank 18 (the second radioactive waste liquid in which hydrazine and oxalic acid are decomposed, or the second radioactive waste liquid containing dilute nitric acid) is dried powder It is pulverized by the materializing device 20 (volume reduction step S10). The powder containing no alpha nuclides generated in the dry powderization device 20 is filled in a solidification container and solidified in the solidification container (container filling or solidification step S11). No long-lived alpha nuclides are present in this stored solidification vessel.
Here, when dilute nitric acid is injected into the second radioactive waste liquid, the powder produced by pulverization of this second radioactive waste liquid contains nitric acid components, and this powder is melted in the solidification container. A vitrified body produced by solidifying with glass also contains a nitric acid component.
On the other hand, when oxalic acid, which is a pH adjuster, is injected into the second radioactive waste liquid, the oxalic acid (pH adjuster) is decomposed as described above. Contains no acid.

When the radionuclide elution step (second washing step S2) using the hydrazine formate aqueous solution is completed, radioactive organic waste from which radionuclides including cladding and α nuclides have been removed remains in the chemical reaction tank 4. ing. In this state, the transfer pump 32 is driven, and the transfer water in the cleaning liquid supply tank 6 is supplied to the chemical reaction tank 4 through the cleaning liquid supply pipe 33 . The transfer water is supplied to the cleaning liquid supply tank 6 from the transfer water tank 9 through lines 31 , 30 and 29 by opening the valve 28 . Valves 26 and 27 are closed.
By supplying transport water, the radioactive organic waste in the chemical reaction tank 4 becomes slurry. The radioactive organic waste slurry contains about 10 wt% radioactive organic waste.
By opening the valve 37 , the radioactive organic waste slurry in the chemical reaction tank 4 is led through the pipe 38 to the second receiving tank 11 .
A predetermined amount of radioactive organic waste taken out from the second receiving tank 11 is transferred to the incineration facility 12 and incinerated in the incineration facility 12 . Ash produced by incineration is solidified by a solidification agent such as cement in a solidification container. This solidified material is low-level radioactive waste because it does not contain alpha nuclides with an extra half-life.

According to this embodiment, in the first washing step S1, the iron oxide component mixed in the radioactive organic waste can be dissolved using the aqueous oxalic acid solution.
Furthermore, according to the present embodiment, in the second washing step S2, radionuclide ions containing α-nuclide ions that are adsorbed on the cation exchange resin, which is radioactive organic waste, are removed from the cation exchange resin of the hydrazine formate aqueous solution. By desorbing from the cation exchange resin by contacting with , the concentration of radionuclides contained in radioactive organic waste can be reduced, and the amount of high-dose radioactive waste can be reduced. In particular, ions of radionuclides, including α-nuclide ions that remain adsorbed on the cation exchange resin without being desorbed from the cation exchange resin even by the aqueous oxalic acid solution, are brought into contact with the radioactive organic waste. Thereby, it can be efficiently desorbed from the cation exchange resin.

According to this embodiment, since a reducing agent such as hydrazine is injected into the radioactive waste liquid containing α-nuclides to adjust the pH of the radioactive waste liquid, the ultra-half-life α-nuclides contained in the radioactive waste liquid are removed by the α-nuclide removal apparatus. It becomes easy to be removed by the ferrite (α nuclide adsorbent) injected in 14 . Therefore, the α-nuclides contained in the radioactive waste liquid are removed by the α-nuclide removal device 14, and the ultra-half-life α-nuclides contained in the radioactive waste liquid flowing out of the α-nuclide removal device 14 are remarkably reduced. As a result, the radiation dose of the radioactive liquid waste flowing out of the α-nuclide removal apparatus 14 is significantly reduced, and the amount of radioactive waste (for example, solidified waste) containing ultra-half-life α-nuclides generated can be reduced.
In particular, the injection of the reducing agent adjusts the pH of the radioactive waste liquid containing the α-nuclides to a range of 4 to 11, so that the α-nuclides removal device 14 can efficiently remove the α-nuclides.

In this embodiment, the ferrite in the α-nuclide removal device 14 is separated by the adsorbent separation device 131 as used ferrite (used α-nuclide adsorbent). The separated ferrite is stored in a solidification container (hereinafter referred to as "first solidification container"). After that, for example, molten glass is filled in a first solidification container containing a predetermined amount of used ferrite that adsorbs α nuclides. After the molten glass has solidified, the first solidification container containing a predetermined amount of used ferrite is sealed.

The timing of transferring the radioactive waste liquid from the chemical cleaning unit 10 to the waste liquid processing unit 19 is measured by attaching a sampling valve to the return pipe 36 and periodically analyzing the radioactive waste liquid sampled by the sampling valve. It may be transferred when the α nuclide concentration reaches a desired concentration.
In this case, when the desired α nuclide concentration is reached, the radioactive waste liquid is transferred from the chemical cleaning unit 10 to the waste liquid treatment unit 19, and in the waste liquid treatment unit 19, the pH adjuster injection device 112 injects the pH adjuster into the radioactive waste liquid. is injected. Also, the adsorbent injection device 121 injects the α-nuclide adsorbent into the radioactive waste liquid.
As described above, the adsorption performance of the α-nuclide adsorbent can be sufficiently exhibited by transferring the radioactive waste liquid to the waste liquid treatment unit 19 when the α-nuclide concentration reaches the desired concentration.
The sampling valve for measuring the α nuclide concentration may be attached to the pipe upstream of the pH adjuster injector 112, and is not limited to the return pipe 36. 112 may be attached to a portion on the upstream side of the confluence with the injection pipe 42 .

When the radioactive organic waste stored in the high-dose resin storage tank 2 contains a cation exchange resin with α nuclides adsorbed, the above-mentioned Patent Document 1 (JP 2015-64334). When the described radioactive organic waste treatment method is carried out, the organic acid aqueous solution in which the crud contained in the radioactive organic waste is dissolved and the organic acid salt aqueous solution in which α-nuclides are desorbed from the cation exchange resin contains alpha nuclides.
The first radioactive waste liquid generated by decomposing the organic acid of the organic acid aqueous solution containing α nuclides with ozone, etc., and the second generated by decomposing the organic acid salt of the organic acid salt aqueous solution containing α nuclides with ozone etc. Each radioactive waste liquid is pulverized and filled into separate solidification containers (hereinafter referred to as “second solidification containers”), and then, for example, molten glass is filled into each second solidification container. be. After the molten glass for solidifying the α-nuclide-containing powder of the first radioactive waste liquid is solidified in the second solidification container, the second solidification container is sealed. After the molten glass for solidifying the α-nuclide-containing powder of the second radioactive waste liquid is solidified in the second solidification container, the second solidification container is sealed.

Here, the processing method of this embodiment and the processing method described in Patent Document 1 are compared.
In these treatment methods, the amount of radioactive organic waste to be subjected to the first cleaning step S1 and the second cleaning step S2 is the same, and the amount of dissolved crud and the amount of desorbed α nuclides are the same. , and the amount of the first radioactive waste liquid and the amount of the second radioactive waste liquid generated are assumed to be the same. At this time, the number of vitrified bodies produced by vitrification of the ferrite adsorbing α nuclides in the first solidification container generated in this example was generated by the treatment method described in Patent Document 1. , the number of vitrified substances produced by vitrifying the powder containing α nuclides of the first radioactive waste liquid in the second solidification container, and the powder containing α nuclides of the second radioactive waste liquid to the second It is less than the total number of vitrified bodies produced by vitrification in the solidification container. That is, the vitrified material containing α-nuclides (radioactive waste containing α-nuclides) generated in this embodiment is the vitrified material containing α-nuclides generated by the treatment method described in Patent Document 1 (α-nuclides (including radioactive waste).

According to the present embodiment, the organic acid (e.g., oxalic acid) contained in the organic acid aqueous solution in which the crud is dissolved and the organic acid salt (e.g., hydrazine formate) contained in the organic acid salt aqueous solution in which the α nuclide is eluted are Since it is decomposed by oxidation treatment using ozone, etc., the amount of radioactive liquid waste containing alpha nuclides is reduced, and the amount of radioactive waste generated is reduced by concentrating or pulverizing the radioactive liquid waste after removing alpha nuclides. be.

According to this embodiment, the crud contained in the radioactive organic waste is dissolved by the organic acid aqueous solution (first washing step S1), and the organic acid salt aqueous solution adsorbs to the cation exchange resin, which is the radioactive organic waste. Since the desorption of α nuclides (second cleaning step S2) is sequentially performed in one cleaning tank (for example, the chemical reaction tank 4), the radioactive waste liquid treatment system can be made more compact. Furthermore, this embodiment eliminates the need to transfer the radioactive organic waste from the first cleaning tank 50 to the second cleaning tank 51 as in the second embodiment described later, so that the radioactive organic waste can be treated. The time required can be shortened.

(Example 2)
As another preferred embodiment of the present invention, the method for treating radioactive waste liquid of Embodiment 2 will be described.
Example 2 is also a radioactive liquid waste treatment method applied to the treatment of radioactive organic waste generated in a boiling water nuclear power plant.
In the radioactive liquid waste treatment method of the present embodiment, the steps S1 to S11 shown in FIG. 1, which were performed in the first embodiment, are also performed.

An example of the structure of a radioactive liquid waste treatment system used in the method for treating radioactive liquid waste in Example 2 will be described with reference to FIG. FIG. 7 is a configuration diagram of an example of a radioactive waste liquid treatment system that executes the radioactive waste liquid treatment method of the first embodiment.

A radioactive waste liquid treatment system 1A shown in FIG. 7 includes a chemical cleaning section 10A for treating radioactive organic waste and a waste liquid treatment section 19A for treating cleaning waste liquid (radioactive liquid waste) discharged from the chemical cleaning section 10A.

In the chemical cleaning section 10A of the present embodiment, among the steps shown in FIG. 1, the first cleaning step S1 for dissolving the crud and the second cleaning step S2 for eluting radionuclides from the radioactive organic waste are performed.
The chemical cleaning section 10A has a first cleaning tank 50, a second cleaning tank 51, an organic acid tank 52, a transfer water tank 54A, an organic acid salt tank 53 and a transfer water tank 54B. In addition, a transfer water tank 56 and a high-dose resin storage tank 2 are provided in the front stage of the chemical cleaning section 10A, and a second receiving tank 11 and an incineration facility (or cement solidification facility) 12 are provided on the right side of the chemical cleaning section 10A in the drawing. is provided.
High dose resin storage tank 2 is connected to transfer water tank 56 by transfer water supply pipe 57 .
A first wash tank 50 is connected to the high dose resin storage tank 2 by an organic waste feed line 23 provided with a transfer pump 22 .
A stirring device configured by attaching a motor 59 to a rotating shaft of a stirring blade 58 is installed in the first cleaning tank 50 .
An organic acid supply pipe 60 connected to the bottom of the organic acid tank 52 and a transfer water supply pipe 61 connected to the bottom of the transfer water tank 54A are connected to a switching valve 62 . The organic acid tank 52 is filled with an oxalic acid aqueous solution, and the transfer water tank 54A is filled with water to be transferred. A liquid supply pipe 64 connected to a switching valve 62 is connected to the first cleaning tank 50 , and a transfer pump 63 is provided in the liquid supply pipe 64 .
A stirring device configured by attaching a motor 68 to a rotating shaft of a stirring blade 67 is installed in the second cleaning tank 51 .
An organic waste transfer pipe 66 equipped with a transfer pump 65 is connected to the first washing tank 50 and the second washing tank 51 .
An organic acid salt supply pipe 69 connected to the bottom of the organic acid salt tank 53 and a transfer water supply pipe 70 connected to the bottom of the transfer water tank 54B are connected to a switching valve 71 . The organic acid salt tank 53 is filled with an ammonium formate aqueous solution, and the transfer water tank 54B is filled with water to be transferred water. A liquid supply pipe 73 connected to a switching valve 71 is connected to the second cleaning tank 51 , and a transfer pump 72 is provided in the liquid supply pipe 73 .
An organic waste transfer pipe 75 is inserted into the second washing tank 51 , and one end of the organic waste transfer pipe 75 reaches near the bottom of the second washing tank 51 . A transfer pump 74 is provided in the organic waste transfer pipe 75 . An organic waste transfer pipe 75 is connected to the second receiving tank 11 .
A pipe connected to the second receiving tank 11 is connected to an incineration facility (or cement solidification facility) 12 .

In addition, the liquid waste treatment unit 19A includes a liquid waste decomposition device 13, an α nuclide removal device 14, a pH adjuster injection device 112, an adsorbent injection device 121, an adsorbent separation device 131, a decomposition device 107, an oxidant supply device 108, and treated water. It has a collection tank 18 .
The waste liquid decomposition device 13 is composed of a cleaning waste liquid treatment tank, and has an ozone injection pipe 81 arranged in the cleaning waste liquid treatment tank. An ozone injection pipe 81 formed with a large number of injection holes is installed at the bottom of the cleaning waste liquid treatment tank. The ozone injection pipe 81 is connected to the ozone supply device 80 by an ozone supply pipe 82 . A waste liquid transfer pipe 77 inserted into the first washing tank 50 and attached to the first washing tank 50 is connected to the washing waste liquid treatment tank of the waste liquid decomposition device 13 . A transfer pump 76 is provided in the waste liquid transfer pipe 77 . A waste liquid transfer pipe 79 inserted into the second washing tank 51 and attached to the second washing tank 51 is connected to the washing waste liquid treatment tank of the waste liquid decomposing device 13 . A transfer pump 78 is provided in the waste liquid transfer pipe 79 . A gas exhaust pipe 83 is connected to the cleaning waste liquid treatment tank of the waste liquid decomposition apparatus 13 . A pipe 45 provided with a transfer pump 43 is inserted into the waste washing liquid treatment tank of the waste liquid decomposition device 13 and attached to the waste washing liquid treatment tank. The pipe 45 is also connected to the α nuclide removal device 14 . The aforementioned “radioactive waste liquid supply pipe for guiding the radioactive waste liquid containing α nuclides” corresponds to this pipe such as the pipe 45 .

Although not shown in FIG. 7, a pipe is provided for returning the filtrate from which the adsorbent has been separated by the adsorbent separator 131 to the chemical cleaning unit 10A, similarly to the pipe 55 in FIG. This pipe is connected to the adsorbent separation device 131 and the liquid supply pipes 64 and 73 flowing into the cleaning tanks 50 and 51 or directly to the cleaning tanks 50 and 51 of the chemical cleaning section 10A.

In this embodiment, the configurations of the α-nuclide removal device 14, the pH adjuster injection device 112, and the parts around them are the same as those of the first embodiment shown in FIG.
A pH adjusting agent injection device 112 is connected to the pipe 45 between the transfer pump 43 and the α nuclide removal device 14 . The pH adjuster injection device 112 used in this embodiment has the same configuration as the pH adjuster injection device 112 used in the first embodiment.
A pipe 46 connects between the α nuclide removal device 14 and the treated water recovery tank 18 (including the adsorbent separation device 131 and the decomposition device 107).

Further, a dry powderization device 20 and a solidification device 21 are provided downstream of the waste liquid processing section 19A.
A pipe 48 provided with a transfer pump 47 connects the treated water recovery tank 18 and the dry powderization device 20 .
A pipe 49 connected to the dry powderization device 20 is connected to the solidification equipment 21 .

Next, a detailed description will be given of the radioactive liquid waste treatment method of this embodiment using the radioactive liquid waste treatment system 1A shown in FIG. In addition, in the present embodiment, description of the same steps (for example, the adsorbent separation step S7 by the adsorbent separation device 131) as in the treatment method using the radioactive waste liquid treatment system 1 of Example 1 will be omitted.
As in Example 1, radioactive organic waste generated from the reactor coolant cleanup system, fuel pool cooling cleanup system, etc. of the boiling water nuclear power plant is stored in the high-dose resin storage tank 2 for a long period of time. Radioactive organic waste stored and stored contains clad, and furthermore, the above-mentioned alpha nuclides and radionuclides other than alpha nuclides are adsorbed.
When transferring the radioactive organic waste stored for a long time in the high-dose resin storage tank 2 to the outside of the high-dose resin storage tank 2, the water in the transfer water tank 56 is transferred through the transfer water supply pipe 57 to the high-dose resin. It is fed into the storage tank 2 . This supply of water turns the radioactive organic waste in the high-dose resin storage tank 2 into a slurry that is easy to transfer.

By driving the transfer pump 22 , the radioactive organic waste slurry in the high-dose resin storage tank 2 is supplied to the first cleaning tank 50 through the organic waste supply pipe 23 . When the water level of the radioactive organic waste slurry in the first washing tank 50 reaches a predetermined level, the transfer pump 22 is stopped and the supply of the slurry to the first washing tank 50 is stopped.
After that, the transfer pump 76 is driven, and the water contained in the slurry in the first washing tank 50 is transferred to the waste liquid transfer pipe 77 as radioactive waste liquid (hereinafter referred to as "third radioactive waste liquid" as in Example 1). It is discharged into the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 through the waste liquid decomposition apparatus 13 . The third radioactive waste liquid introduced into the cleaning waste liquid treatment tank of the liquid waste decomposition device 13 is guided to the α-nuclide removal device 14 in the same manner as the third radioactive waste liquid in the first embodiment. Since the water contained in the radioactive organic waste slurry in the first cleaning tank 50 does not contain α nuclides, the third radioactive waste liquid in the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 does not contain α nuclides, Contains radionuclides other than alpha nuclides.
The third radioactive waste liquid passes through the α-nuclide removal device 14 and is led to the treated water recovery tank 18 . While the third radioactive waste liquid passes through the α-nuclide removal device 14, ferrite (Fe ₃ O ₄ ) particles in the α-nuclide removal device 14 do not adsorb α-nuclides and radionuclides other than α-nuclides. Since the third radioactive waste liquid does not contain α nuclides, the pH adjuster aqueous solution is not injected from the pH adjuster injector 112 into the pipe 45, and the reducing agent (eg, hydrazine) is not decomposed in the decomposer 107. do not have. Colloidal substances and solids contained in the third radioactive waste liquid are removed by the filtering effect of ferrite.

When the transfer of the third radioactive waste liquid in the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 to the α-nuclide removal device 14 is completed, the transfer pump 43 is stopped.
The third radioactive waste liquid containing no alpha nuclides in the treated water recovery tank 18 is pulverized by the dry pulverization device 20, and the produced powder is transferred to the solidification equipment 21 and solidified in the solidification container. After sealing, the solidification container is stored at a storage location. No long-lived alpha nuclides are present in this stored solidification vessel.

After that, the first cleaning step S1 is performed. In the first cleaning step S1, mainly by injecting an organic acid aqueous solution, for example, an oxalic acid aqueous solution into the first cleaning tank 50, the crud such as iron oxides transferred to the first cleaning tank 50 together with the radioactive organic waste is removed. is dissolved. Detailed contents of the first cleaning step S1 performed in this embodiment will be described below.

The switching valve 62 is operated to connect the organic acid supply pipe 60 and the liquid supply pipe 64, and the transfer pump 63 is driven. An oxalic acid aqueous solution (oxalic acid concentration: about 0.8 mol/L) in the organic acid tank 52 is supplied to the first cleaning tank 50 through the organic acid supply pipe 60 and the liquid supply pipe 64 . At this time, the water in the transfer water tank 54A is not supplied to the first cleaning tank 50 because the transfer water supply pipe 61 and the liquid supply pipe 64 are not in communication. When the liquid level of the oxalic acid aqueous solution in the first cleaning tank 50 reaches the set liquid level, the transfer pump 63 is stopped and the supply of the oxalic acid aqueous solution to the first cleaning tank 50 is stopped. The amount of oxalic acid aqueous solution supplied into the first cleaning tank 50 is set to be ten times the amount of radioactive organic waste in the first cleaning tank 50 .

The oxalic acid aqueous solution in the first cleaning tank 50 is heated to, for example, 60° C. by a heating device (not shown) provided on the outer surface of the first cleaning tank 50 . The temperature of this oxalic acid aqueous solution is maintained at 60° C. by adjusting the amount of heating by the heating device. While the temperature is maintained at 60° C., the motor 59 is driven to rotate the stirring blade 58 to stir the radioactive organic waste and the aqueous oxalic acid solution in the first cleaning tank 50 . The radioactive organic waste is immersed in the aqueous oxalic acid solution for, for example, 6 hours while being stirred in the first cleaning tank 50 . In the first cleaning tank 50, clad mixed in the radioactive organic waste is dissolved by oxalic acid. Radionuclides such as cobalt-60 contained in the clad migrate into the aqueous oxalic acid solution due to the dissolution of the clad. When the iron component of the cladding is dissolved, iron (II) ions are generated, and these iron (II) ions react with oxalic acid to generate iron oxalate, which may precipitate. In order to suppress the generation of iron oxalate, if necessary, a small amount of an oxidizing agent (for example, hydrogen peroxide) that converts iron (II) ions to iron (III) ions is added to the first cleaning tank 50 .
As in Example 1, in the first washing step S1, the ion exchange resin, which is a part of the radioactive organic waste, is immersed in oxalic acid, so that hydrogen ions and oxalate ions generated by dissociation of oxalic acid are Some radionuclides (α nuclides and radionuclides other than desorbed from the exchange resin.

The first cleaning step S1 is completed when 6 hours, which is the immersion time of the radioactive organic waste in the oxalic acid aqueous solution in the first cleaning tank 50, has elapsed. The heating of the first cleaning tank 50 by the heating device and the motor 59 are stopped, the transfer pump 76 is driven, and the oxalic acid containing radionuclides (α nuclides and radionuclides other than α nuclides) in the first cleaning tank 50 An aqueous solution (hereinafter referred to as "first radioactive waste liquid" as in Example 1) is supplied as a washing waste liquid through a waste liquid transfer pipe 77 into the washing waste liquid treatment tank of the waste liquid decomposition device 13 . When the transfer of the oxalic acid aqueous solution in the first cleaning tank 50 to the waste cleaning liquid treatment tank is completed, the transfer pump 76 is stopped.

After the transfer of the oxalic acid aqueous solution to the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 is completed, the waste liquid decomposition step S4 is carried out. In the waste liquid decomposition step S4, ozone is supplied from the ozone supply device 80 through the ozone supply pipe 82 to the ozone injection pipe 81 for a predetermined period of time, and is discharged from a large number of injection holes of the ozone injection pipe 81 to the cleaning waste liquid treatment of the waste liquid decomposition device 13. It is injected into the oxalic acid aqueous solution in the tank. Oxalic acid, which is an organic component contained in the oxalic acid aqueous solution, is decomposed into carbon dioxide gas and water by the injected ozone. The remainder of the ozone sprayed into the cleaning waste liquid treatment tank and carbon dioxide gas are supplied to an offgas treatment device (not shown) through the gas exhaust pipe 83, and the radioactive gas contained in the gas discharged through the gas exhaust pipe 83 is removed. Removed in an offgassing unit.
After the supply of ozone is stopped, the transfer pump 43 is driven, and the α nuclides desorbed from the cation exchange resin and the radionuclides other than the α nuclides existing in the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 are removed. A waste liquid containing each, that is, a first radioactive waste liquid is supplied to the α-nuclide removal device 14 through a pipe 45 .

After the waste liquid decomposition step S4 described above, a pH adjuster is injected from the pH adjuster injection device 112 into the pipe 45 in order to perform the pH adjuster injection step S5.
Also in this embodiment, either a reducing agent or an acid is used as the pH adjuster injected into the pipe 45 .
Any of the various reducing agents and acids listed in Example 1 can be used as the reducing agent and acid.

In this example, as in Example 1, a pH adjuster corresponding to the pH to be adjusted is injected. That is, when the pH of the first radioactive waste liquid containing α nuclides is adjusted to a pH within the range of 4 to 7 (4 to 7) within the range of 4 to 11, the pH adjuster is added to the first radioactive waste liquid. Acid (eg dilute nitric acid) is injected. On the other hand, when adjusting the pH of the first radioactive waste liquid containing α nuclides to a pH within the range of 4 or more and 11 or less and within the range of 7 or more and 11 or less, a reducing agent (for example, , hydrazine) is injected.

In this embodiment, the pH of the first radioactive waste liquid containing α-nuclides, which is supplied to the α-nuclide removal device 14, is set to, for example, "8", which is the set pH.
Therefore, in the pH adjuster injection device 112, the valve 41 is opened to inject the reducing agent aqueous solution, for example, hydrazine aqueous solution, in the reducing agent tank 17A into the pipe 45 through the injection pipe 42 (pH adjuster injection step S5). ). The pH of the first radioactive waste liquid is adjusted to within the range of 4 to 11, eg, 8, by injecting hydrazine, and the first radioactive waste liquid containing the hydrazine flows into the α-nuclide removal device 14 . The opening of the valve 41 is controlled based on the pH of the first radioactive waste liquid flowing into the α-nuclide removal device 14 measured by the pH meter 49A, and the pH of the first radioactive waste liquid, that is, the pH measured by the pH meter 49A The amount of hydrazine aqueous solution supplied from the reducing agent tank 17A to the pipe 45 is adjusted so that the pH becomes 8. The pH of the first radioactive waste liquid is, for example, 6 before it flows into the α-nuclide removal device 14 .
The first radioactive waste liquid contains hydrazine, and the hydrazine adjusts the pH of the first radioactive waste liquid to within the range of 4 to 11, for example, to 8. Therefore, the valence contained in the first radioactive waste liquid is "3 to The valence of each alpha nuclide which is 5" is adjusted to '3'. Each α-nuclide with a valence of "3" contained in the first radioactive waste liquid is removed by being adsorbed by ferrite particles in the α-nuclide removal device 14 (α-nuclide removal step S6). Colloidal substances and solids contained in the first radioactive waste liquid are also removed by the filtering effect of the ferrite.

Since hydrazine, which is a reducing agent, is injected in the pH adjuster injection step S5, the determination in the pH adjuster determination step S8 becomes "YES", and the ferrite injected into the α nuclide removal device 14 has α nuclides, The first radioactive waste liquid, from which colloidal substances and solids have been removed, is discharged through pipe 46 and led to decomposition device 107 . Hydrazine contained in the first radioactive waste liquid is decomposed in the decomposition device 107 in the same manner as hydrazine contained in the first radioactive waste liquid in Example 1 (reducing agent decomposition step S9).
The first radioactive waste liquid discharged from the decomposition device 107 and containing no alpha nuclides and hydrazine is guided to the treated water recovery tank 18 through the pipe 46 .

When the pH of the first radioactive waste liquid is set to 6, for example, in the same manner as the first radioactive waste liquid in Example 1, in the pH adjusting agent injection step S5, the acid dilute nitric acid aqueous solution is injected as the pH adjusting agent. Apparatus 112 is injected into the first radioactive effluent. The first radioactive waste liquid containing injected dilute nitric acid flows into the α nuclide removal device 14 . The α nuclides contained in the first radioactive waste liquid, the pH of which has been adjusted to 6 by the injection of the diluted nitric acid aqueous solution, are removed by being adsorbed by the ferrite injected into the α nuclide removal device 14 (α nuclide removal step S6).

In the pH adjuster injection step S5, when the dilute nitric acid aqueous solution is injected into the first radioactive waste liquid, the determination in the pH adjuster determination step S8 becomes “No”, and the dilute The first radioactive waste liquid containing nitric acid directly passes through the decomposition device 107 to which hydrogen peroxide is not supplied from the chemical liquid tank 109 and is led to the treated water recovery tank 18 .

As in Example 1, the first radioactive waste liquid (the first radioactive waste liquid in which hydrazine is decomposed or the first radioactive waste liquid containing dilute nitric acid) in the treated water recovery tank 18 is powdered by the drying and pulverizing device 20. (volume reduction step S10). The powder produced by the dry powderization device 20 is filled into a solidification container and solidified in the solidification container by the solidification equipment 21 (container filling or solidification step S11). No long-lived alpha nuclides are present in this stored solidification vessel.

After the aqueous oxalic acid solution in the first cleaning tank 50 has been discharged to the cleaning waste liquid treatment tank of the waste liquid decomposition device 13, the switching valve 62 is operated to connect the transfer water supply pipe 61 and the liquid supply pipe 64. , the transfer pump 63 is driven, and the water in the transfer water tank 54A is supplied to the first cleaning tank 50 through the transfer water supply pipe 61 and the liquid supply pipe 64 as transfer water. At this time, since the organic acid supply pipe 60 and the liquid supply pipe 64 are not communicated with each other, the oxalic acid aqueous solution in the organic acid tank 52 is not supplied to the first cleaning tank 50 . When a predetermined amount of water is supplied from the transfer water tank 54A to the first washing tank 50 and the water level in the first washing tank 50 reaches the set water level, the transfer pump 63 is stopped and the water is supplied to the first washing tank 50. stop the supply.
The motor 59 is driven to rotate the stirring blades 58 to stir the radioactive organic waste and water in the first cleaning tank 50 to make the radioactive organic waste into slurry. The transfer pump 65 is driven to supply the radioactive organic waste slurry in the first cleaning tank 50 to the second cleaning tank 51 through the organic waste transfer pipe 66 .
When the radioactive organic waste slurry in the first washing tank 50 is transferred, the amount of water in the first washing tank 50 decreases and the radioactive organic waste in the first washing tank 50 becomes difficult to transfer. The pump 63 is driven to supply the water in the transfer water tank 54A into the first cleaning tank 50.
When the transfer of the radioactive organic waste in the first cleaning tank 50 to the second cleaning tank 51 is completed, the transfer pump 65 is stopped and the transfer pump 78 is driven.
The water in the second cleaning tank 51 is discharged to the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 through the waste liquid transfer pipe 79 as the third radioactive waste liquid.

The third radioactive waste liquid discharged from the second cleaning tank 51 to the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 passes through the α nuclide removal device 14 and is led to the treated water recovery tank 18 . The third radioactive waste liquid discharged from the second cleaning tank 51 does not contain α-nuclides, but contains radionuclides other than α-nuclides. For this reason, the pH adjuster aqueous solution (hydrazine aqueous solution or dilute nitric acid aqueous solution) is not injected from the pH adjuster injector 112 into the pipe 45 in the pH adjuster injection step S5, and this third radioactive waste liquid is transferred to the α-nuclide removal apparatus 14. , the ferrite in the α-nuclide removal device 14 does not adsorb α-nuclides and radionuclides other than α-nuclides. Also, the reducing agent (for example, hydrazine) is not decomposed in the reducing agent decomposition step S9.
The third radioactive waste liquid in the treated water recovery tank 18 is powdered by the dry powderization device 20 (volume reduction step S10), and the generated powder is transferred to the solidification equipment 21 and solidified in the solidification container ( Container filling or solidification step S11). After sealing, the solidification container is stored at a storage location. No long-lived alpha nuclides are present in this stored solidification vessel.

When the transfer pump 78 is stopped and the discharge of water from the second cleaning tank 51 to the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 is completed, the second cleaning step S2 (organic acid salt treatment step) is carried out. In the second washing step S2, organic acid salts are used to more efficiently elute radionuclides adsorbed on ion exchange resins (eg, cation exchange resins).
The organic acid salt bath 53 is filled with an aqueous solution of ammonium formate, which is an organic acid salt, and the concentration of ammonium formate in this aqueous solution of ammonium formate is, for example, 1.2 mol/L. Ammonium formate is an organic acid salt that yields a cation that is more likely to be adsorbed on a cation exchange resin than a hydrogen ion. The following matters are implemented in the second cleaning step S2.
The switching valve 71 is operated to connect the organic acid salt supply pipe 69 and the liquid supply pipe 73, and the transfer pump 72 is driven. The aqueous ammonium formate solution in the organic acid salt tank 53 is supplied to the second cleaning tank 51 through the organic acid salt supply pipe 69 and the liquid supply pipe 73 . At this time, since the transfer water supply pipe 70 and the liquid supply pipe 73 are not communicated with each other, the water in the transfer water tank 54B is not supplied to the second cleaning tank 51 . When the liquid level of the ammonium formate aqueous solution in the second cleaning tank 51 reaches the set liquid level, the transfer pump 72 is stopped and the supply of the ammonium formate aqueous solution to the second cleaning tank 51 is stopped.

The ammonium formate aqueous solution in the second cleaning tank 51 is heated to 60° C., for example, by a heating device (not shown) provided on the outer surface of the second cleaning tank 51 . The temperature of this ammonium formate aqueous solution is maintained at 60° C. by adjusting the amount of heating by the heating device. While the temperature is maintained at 60° C., the motor 68 is driven to rotate the stirring blade 67 to stir and mix the radioactive organic waste and the ammonium formate aqueous solution in the second cleaning tank 51 . The radioactive organic waste is immersed in the ammonium formate aqueous solution for, for example, two hours while being stirred in the second cleaning tank 51 . In the second washing tank 51, radionuclide ions adsorbed to the cation exchange resin, which is radioactive organic waste, are more likely to be adsorbed to the cation exchange resin than hydrogen ions. Ammonium present in the ammonium formate aqueous solution It is replaced with ions and efficiently desorbed into an aqueous solution of ammonium formate. This significantly reduces the amount of radionuclides adsorbed on the cation exchange resin.
The second cleaning step S2 is completed when two hours, which is the immersion time of the radioactive organic waste in the aqueous ammonium formate solution in the second cleaning tank 51, has elapsed. After stopping the heating of the second washing tank 51 by the heating device and stopping the motor 68, the transfer pump 78 is driven, and the ammonium formate aqueous solution containing the radionuclide in the second washing tank 51 (hereinafter referred to as "second radioactive waste liquid") ) is supplied as a cleaning waste liquid through the waste liquid transfer pipe 79 into the cleaning waste liquid treatment tank of the waste liquid decomposing device 13 . When the transfer of the ammonium formate aqueous solution in the second cleaning tank 51 to the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 is completed, the transfer pump 78 is stopped.

After the transfer of the ammonium formate aqueous solution to the cleaning waste liquid treatment tank of the waste liquid decomposition device 13 is completed, the waste liquid decomposition step S4 is carried out. In the waste liquid decomposition step S4, ozone is supplied from the ozone supply device 80 to the ozone injection pipe 81 for a predetermined period of time, and is jetted into the ammonium formate aqueous solution in the cleaning waste liquid treatment tank of the waste liquid decomposition device 13. Ammonium formate, which is an organic component contained in the ammonium formate aqueous solution, is decomposed by ozone. Ammonium formate reacts with ozone and decomposes into nitrogen gas, carbon dioxide gas and water. These gases are supplied through a gas exhaust pipe 83 to the above-described offgas treatment device (not shown).
After the supply of ozone is stopped and the waste liquid decomposition step S4 performed after the second cleaning step S2 is completed, the transfer pump 43 is driven, and the desorbed A waste liquid containing each of the α-nuclides and radionuclides other than the α-nuclides, that is, the second radioactive waste liquid is supplied to the α-nuclide removal device 14 through the pipe 45 .

Since the second radioactive waste liquid containing α nuclides is supplied to the α nuclide removal device 14, the valve 41 is opened to inject the hydrazine aqueous solution in the reducing agent tank 17A into the pipe 45 through the injection pipe 42 (reducing agent injection step S5). The pH of the second radioactive waste liquid is adjusted to within the range of 4 to 11, eg, 8, by injecting hydrazine, and the second radioactive waste liquid containing hydrazine flows into the α-nuclide removal device 14 . The opening degree of the valve 41 is controlled based on the pH of the second radioactive waste liquid flowing into the α-nuclide removal device 14, which is measured by the pH meter 49A, so that the pH of the second radioactive waste liquid is within the range of 8. The amount of hydrazine aqueous solution supplied from the reducing agent tank 17A to the pipe 45 is adjusted. The pH of the second radioactive waste liquid is, for example, 6 before it flows into the α-nuclide removal device 14 .
The second radioactive waste liquid contains hydrazine, and the hydrazine adjusts the pH of the second radioactive waste liquid to within the range of 4 to 11, for example, to 8. Therefore, the valence contained in the second radioactive waste liquid is "3 to The valence of each alpha nuclide which is 5" is adjusted to '3'. Each α-nuclide with a valence of "3" contained in the second radioactive waste liquid is removed by being adsorbed by ferrite particles in the α-nuclide removal device 14 (α-nuclide removal step S6). Colloidal substances and solids contained in the second radioactive waste liquid are also removed by the filtering effect of the ferrite.

Since hydrazine, which is a reducing agent, is injected in the pH adjuster injection step S5, the judgment in the pH adjuster judgment step S8 becomes "YES", and the ferrite removes α nuclides, colloidal substances, and solid content. The second radioactive waste liquid is discharged to the pipe 46 and guided to the decomposition device 107, and the hydrazine contained in the second radioactive waste liquid is decomposed in the decomposition device 107 in the same manner as the hydrazine contained in the first radioactive waste liquid. (reducing agent decomposition step S9).
The second radioactive liquid waste discharged from the decomposition device 107 and containing no alpha nuclides and hydrazine is guided to the treated water recovery tank 18 through the pipe 46 .

In addition, when the pH of the second radioactive waste liquid is set to, for example, 6, similarly to the above-mentioned first radioactive waste liquid in the present embodiment, a dilute nitric acid aqueous solution, which is an acid, is added upstream of the α-nuclide removal device 14 to pH It is injected from the modifier injector 112 into the second radioactive effluent. The α nuclides contained in the second radioactive waste liquid containing dilute nitric acid and having a pH of 6 are removed by being adsorbed by ferrite in the α nuclide removal device 14 (α nuclide removal step S6).

In the pH adjuster injection step S5, when the dilute nitric acid aqueous solution is injected into the second radioactive waste liquid, the determination in the pH adjuster determination step S8 becomes “No”, and the dilute The second radioactive waste liquid containing nitric acid directly passes through the decomposition device 107 to which hydrogen peroxide is not supplied from the chemical liquid tank 109 and is led to the treated water recovery tank 18 .

The second radioactive waste liquid (the second radioactive waste liquid in which hydrazine is decomposed or the second radioactive waste liquid containing dilute nitric acid) in the treated water recovery tank 18 is pulverized by the drying and powdering device 20 (volume reduction process S10). The powder produced by the dry powderization device 20 is filled into a solidification container and solidified in the solidification container by the solidification equipment 21 (container filling or solidification step S11). No long-lived alpha nuclides are present in this stored solidification vessel.

After the transfer of the ammonium formate aqueous solution from the second washing tank 51 to the washing waste liquid treatment tank of the waste liquid decomposition device 13 is completed, the transfer water supply pipe 70 and the liquid supply pipe 73 are connected by operating the switching valve 71, and the transfer pump 72 is driven, the water in the transfer water tank 54B is supplied to the second washing tank 51. As shown in FIG. After a predetermined amount of water has been supplied to the second washing tank 51, the transfer pump 72 is stopped, and the supply of water from the transfer water tank 54B to the second washing tank 51 is stopped. The stirring blade 67 is rotated to stir the remaining radioactive organic waste and the supplied water in the second washing tank 51 to produce a slurry containing the radioactive organic waste. The transfer pump 74 is driven, and the slurry containing the radioactive organic waste in the second washing tank 51 is discharged to the organic waste transfer pipe 75 . Since the radioactive organic waste discharged into the organic waste transfer pipe 75 does not substantially contain crud, and the radionuclide ions adsorbed to the cation exchange resin are further reduced, the radiation dose of the radioactive organic waste is rate has been significantly reduced.

The radioactive organic waste discharged to the organic waste transfer pipe 75 is guided to the second receiving tank 11 .
A predetermined amount of radioactive organic waste taken out from the second receiving tank 11 is transferred to the incineration facility 12 and incinerated in the incineration facility 12 . Ash produced by incineration is solidified by a solidification agent such as cement in a solidification container. This solidified material is low-level radioactive waste because it does not contain alpha nuclides with an extra half-life.

In the first washing step S1 of the present embodiment, formic acid, acetic acid or citric acid may be used instead of oxalic acid, and in the second washing step S2, oxalic acid, carbonic acid, acetic acid or citric acid may be used instead of ammonium formate. Ammonium, barium or cesium salts of acids or barium or cesium formic acids may be used. These organic acid salts are organic acid salts that yield cations that are more readily adsorbed to the cation exchange resin than hydrogen.

In this embodiment, among the effects produced in the first embodiment, the effects produced by carrying out the first cleaning step S1 and the second cleaning step S2 in one cleaning tank are excluded, and the remaining effects are obtained. can be done.

(Example 3)
Embodiment 3 A radioactive waste liquid treatment method of Embodiment 3 applied to nuclear fuel reprocessing, which is another preferred embodiment of the present invention, will be described with reference to FIGS. 8 and 9. FIG.

Spent nuclear fuel contained in spent fuel assemblies removed from nuclear reactors of nuclear plants such as boiling water nuclear plants and pressurized water nuclear plants is subjected to nuclear fuel reprocessing and the spent nuclear fuel material Uranium and plutonium are recovered from The recovered uranium and plutonium are used to manufacture new fuel assemblies, and the manufactured new fuel assemblies are loaded into the core of a nuclear power plant. In the reprocessing of nuclear fuel, radioactive waste liquid containing alpha nuclides such as trace amounts of uranium and plutonium left unrecovered and alpha nuclides such as neptunium and curium is generated as uranium and plutonium are recovered. This radioactive waste liquid is an aqueous nitric acid solution.

The radioactive liquid waste treatment method of this embodiment uses the injection of the reducing agent and the removal of the alpha nuclides by the alpha nuclide removal device described in Examples 1 and 2 for the treatment of the radioactive liquid waste generated in nuclear fuel reprocessing. applied.

FIG. 8 shows a flow chart showing the procedure of the method for treating radioactive waste liquid in Example 3. As shown in FIG. In FIG. 8, steps similar to those shown in FIG. 1 are given the same reference numerals.

In this embodiment, first, in the decladding step S21 shown in FIG. 8, the cladding tubes are removed from a plurality of fuel rods included in the spent fuel assembly removed from the core of the nuclear reactor. As a result, the pellet-shaped nuclear fuel material 85 present in the cladding tube is taken out. This nuclear fuel material 85 contains alpha nuclides such as uranium, plutonium, neptunium and curium.
Pellet-shaped uranium dioxide exists as a nuclear fuel material in the fuel rods contained in the fuel assemblies initially loaded into the core. During the operation of a nuclear power plant, fissionable material (eg, uranium-235) contained in the nuclear fuel material is fissioned to produce fission products of alpha nuclides such as plutonium, neptunium, and curium within the nuclear fuel material.

In the nuclear fuel pulverization process S22 performed after the decoating step S21, the pellet-shaped nuclear fuel material 85 is converted into oxide powder to become powdered nuclear fuel material 86 . The powdered nuclear fuel material 86 is sent to the fluorination step S23.

In this fluorination step S23, fluorine (or a fluorine compound) is brought into contact with the powdered nuclear fuel material 86 to convert part of the uranium contained in the nuclear fuel material 86 into uranium hexafluoride (UF ₆ ) 87. volatilize. The uranium hexafluoride 87 is sent to the UF ₆ refining step S24.
Uranium hexafluoride 87 is purified by distillation or adsorption to remove impurities in the UF ₆ purification step S24. Uranium fuel 88 is produced by refining uranium hexafluoride 87 .

The remaining nuclear fuel material 89 that has not volatilized in the fluorination step S23 contains non-volatilized alpha nuclides such as uranium, plutonium, neptunium and curium. The residual nuclear fuel material 89 is dissolved with a nitric acid solution in the dissolving step S25.
Then, the nuclear fuel material solution (containing nitric acid) 90 is brought into contact with an organic phase containing tributyl phosphate (TBP) in the co-decontamination step S26. Uranium and plutonium contained in the solution 90 are transferred to the organic phase, and among fission products, alpha nuclides such as neptunium and curium, excluding plutonium, do not transfer to the organic phase.

A back extraction step S27 is performed on the organic phase 91 containing uranium and plutonium. In this back extraction step S27, a dilute oxalic acid aqueous solution is brought into contact with the organic phase 91 containing uranium and plutonium. Uranium and plutonium contained in the organic phase 91 migrate into the aqueous oxalic acid solution. A dilute oxalic acid aqueous solution 92 containing uranium and plutonium is sent to a refining step S28.

In the refining step S28, extraction using an organic phase containing TBP and back extraction using a dilute nitric acid aqueous solution are repeated until the degree of refining of uranium and plutonium reaches a predetermined value.
The uranium and plutonium that have reached a predetermined accuracy are sent to a denitrification/roasting reduction process (not shown), where they are converted into a uranium-plutonium mixed oxide. A mixed oxide fuel (MOX fuel) 93 is produced using this mixed oxide.
The eight steps S21 to S28 described above are steps related to nuclear fuel reprocessing.

A pH adjusting agent injection step S5 is performed on the radioactive waste liquid 94, which is a nitric acid solution containing a trace amount of uranium and plutonium and α-nuclides such as neptunium and curium generated in the co-decontamination step S26. The pH of the radioactive waste liquid 94 containing nitric acid generated in the co-decontamination step S26 is about 1 (strong acid). The radioactive waste liquid 94 has lower concentrations of uranium and plutonium than the dissolution liquid 90 , but the components contained in the radioactive waste liquid 94 are the same as the components contained in the dissolution liquid 90 .

FIG. 9 shows a detailed block diagram of the α-nuclide removal device used in Example 3. As shown in FIG.
The configuration other than the configuration shown in FIG. 9 can be the same configuration as the configuration of the first embodiment shown in FIG. 2 or the configuration of the second embodiment shown in FIG.
The radioactive waste liquid 94 is supplied to the piping 45A of the radioactive waste liquid processing system used in the radioactive waste liquid processing method of this embodiment shown in FIG.

Here, the configuration of the radioactive waste liquid treatment system used in this embodiment will be described with reference to FIG.
This radioactive waste liquid treatment system has a pH adjuster injection device 112A, an adsorbent injection device 121A, and an α nuclide removal device .
The pH adjuster injector 112A has a reducing agent injector 17 and a neutralizer injector 99 . The reducing agent injection device 17 has the same configuration as the reducing agent injection device 17 used in the first embodiment. The neutralizing liquid injection device 99 has a neutralizing liquid tank 100 and a neutralizing liquid injection pipe 102 provided with a valve 101 .
The neutralizing liquid tank 100 is filled with a neutralizing agent aqueous solution, for example, a sodium hydroxide aqueous solution containing sodium hydroxide as a neutralizing agent. A neutralizing liquid injection pipe 102 is connected to the neutralizing liquid tank 100 . A neutralizing solution injection pipe 102 of the neutralizing solution injection device 99 is connected to the pipe 45A on the upstream side of the connection point between the injection pipe 42 of the reducing agent injection device 17 and the pipe 45A.
In this embodiment, a reducing agent and a neutralizing agent are used as pH adjusters.

In this embodiment, since the nitric acid contained in the radioactive liquid waste 94 must be neutralized, the neutralizer is an alkaline substance.
In this embodiment, the neutralizing agent is sodium hydroxide, sodium bicarbonate, or hydroxides of alkali metals and alkaline earth metals.

The neutralizing agent used in this embodiment is a kind of pH adjusting agent, and not only adjusts the pH of the radioactive waste liquid 94 to neutral "7", but also adjusts the pH of the radioactive waste liquid 94 to 4 or more and less than 7. Also used for regulation. The neutralizing agent aqueous solution filled in the neutralizing liquid tank 100 is a kind of pH adjusting agent aqueous solution containing a neutralizing agent which is a pH adjusting agent.
A pH meter 49C is attached to the pipe 45A between the connection point of the pipe 45A of the neutralized solution injection pipe 102 of the neutralized solution injection device 99 and the connection point of the injection pipe 42 of the reducing agent injection device 17 and the pipe 45A. A pH meter 49A is attached to the pipe 45A between the connecting point of the injection pipe 42 and the pipe 45A and the α nuclide removal device 14 . The pipe 45A is connected to the α nuclide removal device 14 .

In this embodiment, when adjusting the pH of the radioactive waste liquid containing α nuclides to within the range of 4 to 7 within the range of 4 to 11 (4 to 7), a neutralizing agent (for example, sodium hydroxide).
On the other hand, when adjusting the pH of the radioactive waste liquid containing α nuclides to within the range of 4 to 11 and greater than 7 to 11 or less, first, a neutralizing agent is injected into the radioactive waste liquid to adjust the pH of the radioactive waste liquid. to 7, and then inject a reducing agent (eg, hydrazine) into the radioactive effluent.

In the radioactive waste liquid treatment method of the present embodiment, it is assumed that the pH of the radioactive waste liquid 94, which has a pH of about 1, is adjusted to within the range of 4 or more and 11 or less, for example, 8.
First, the valve 101 is opened to inject the sodium hydroxide aqueous solution in the neutralization liquid tank 100 into the radioactive waste liquid 94 containing nitric acid flowing in the pipe 45A, and the pH of the radioactive waste liquid 94 is adjusted to within the range of 4 or more and 7 or less. Adjust to "7" (pH adjusting agent injection step S5).
The pH meter 49C measures water flowing in the pipe 45A between the connection point of the pipe 45A of the neutralized solution injection pipe 102 of the neutralizing solution injection device 99 and the connection point of the injection pipe 42 of the reducing agent injection device 17 and the pipe 45A. The pH of the radioactive waste liquid 94 into which the sodium oxide aqueous solution is injected (the radioactive waste liquid 94 containing sodium hydroxide but not containing hydrazine) is measured. The opening of the valve 101 is controlled so that the measured value of the pH meter 49C becomes the set value of pH, for example, "7", and the injection amount of the aqueous sodium hydroxide solution into the radioactive waste liquid 94 flowing in the pipe 45A is adjusted. do.

After that, the valve 41 is opened to inject the hydrazine aqueous solution in the reducing agent tank 17A through the injection pipe 42 into the pipe 45A through which the radioactive waste liquid 94 adjusted to pH 7 flows (pH adjuster injection step S5 ).
The pH of the radioactive waste liquid 94 is adjusted to within the range of 4 to 11, for example 8, by injecting sodium hydroxide and hydrazine, and the radioactive waste liquid 94 containing sodium hydroxide and hydrazine flows into the α-nuclide removal device 14. do. The degree of opening of the valve 41 is controlled based on the pH of the radioactive waste liquid 94 containing sodium hydroxide and hydrazine flowing into the α nuclide removal device 14 measured by the pH meter 49A, and the pH of the radioactive waste liquid 94 becomes 8. , the amount of hydrazine aqueous solution supplied from the reducing agent tank 17A to the pipe 45A is adjusted.

In order to adjust the pH of the radioactive liquid waste 94, which has a pH of about 1, to 8 only by injecting hydrazine, a large amount of hydrazine is required, the amount of the radioactive liquid waste 94 significantly increases, and the number of solidified substances generated is also very large. increase in However, as in this embodiment, the neutralizing agent sodium hydroxide is injected to increase the pH of the radioactive waste liquid 94 from about 1 to 7, and then hydrazine is injected to increase the pH of the radioactive waste liquid 94 to 8. In this case, the amount of sodium hydroxide to be injected can be reduced, and the amount of hydrazine to be injected can be significantly reduced.
As described above, when the pH of the radioactive waste liquid 94 is increased from about 1 to 8 by injecting sodium hydroxide and hydrazine, when the pH of the radioactive waste liquid 94 is increased from about 1 to 8 by injecting hydrazine alone, Compared to this, the number of generated solidified bodies can be significantly reduced.

The radioactive waste liquid 94 contains sodium hydroxide and hydrazine, and the pH of the radioactive waste liquid 94 is adjusted to within the range of 4 to 11, for example, 8 by the sodium hydroxide and hydrazine. is adjusted to "3". Each α-nuclide with a valence of "3" contained in the radioactive waste liquid 94 is removed by being adsorbed by ferrite particles in the α-nuclide removal device 14 (α-nuclide removal step S6). Colloidal substances and solids contained in radioactive waste liquid 94 are also removed by the filtering effect of ferrite.

Since hydrazine is contained in the radioactive waste liquid 94 together with sodium hydroxide, the determination of "is the pH adjuster a reducing agent?" in the pH adjuster determination step S8 becomes "YES". Determination of "whether the pH adjuster is a reducing agent" in this embodiment is substantially a determination of "whether a reducing agent is included as the pH adjuster". Since hydrazine is contained in the radioactive waste liquid 94, the determination in the pH adjusting agent determination step S8 is "YES".
Hydrazine contained in the radioactive waste liquid 94 discharged from the α-nuclide removal device 14 to the pipe 46 is decomposed in the decomposing device 107 as described in the first and second embodiments (reducing agent decomposition step S9). Then, the radioactive waste liquid 94 containing no alpha nuclides and hydrazine is guided to a waste liquid recovery tank (not shown) through the pipe 46 .
The radiation dose rate of the radioactive waste liquid 94 from which the α nuclides have been removed is significantly reduced.

The radioactive waste liquid 94 in the waste liquid collection tank is pulverized by a dry pulverizer (volume reduction step S10).
The powder produced by the dry powderization apparatus is filled into a solidification container and solidified in the solidification container (container filling or solidification step S11).

Incidentally, when the pH of the radioactive waste liquid 94 whose pH is about 1 is adjusted to within the range of 4 or more and 11 or less, for example, 6, the measured value of the pH meter 49C is "6", which is the set value of pH. , the opening of the valve 101 is controlled to adjust the injection amount of the aqueous sodium hydroxide solution into the radioactive waste liquid 94 flowing in the pipe 45A. At this time, the hydrazine aqueous solution is not injected into the radioactive waste liquid 94 having a pH of 6 by the reducing agent injector 17 .
In addition, since the aqueous hydrazine solution is not injected, the decomposition of hydrazine in the decomposition device 107 (reducing agent decomposition step S9) is not performed. The radioactive waste liquid 94 having a pH of 6 and containing sodium hydroxide discharged from the α-nuclide removal device 14 passes through the decomposition device 107 as it is, and is pulverized by the drying powderization device (volume reduction step S10).

According to this embodiment, a reducing agent such as hydrazine is injected into the radioactive waste liquid containing nitric acid and α nuclides to adjust the pH of the radioactive waste liquid. The α-nuclides are easily removed by the removal device 14, and the α-nuclides contained in the radioactive waste liquid flowing out from the α-nuclide removal device 14 are significantly reduced. As a result, the radiation dose of the radioactive liquid waste flowing out of the α-nuclide removal apparatus 14 is significantly reduced, and the amount of radioactive waste (for example, solidified waste) containing ultra-half-life α-nuclides generated can be reduced.
In particular, the injection of the reducing agent adjusts the pH of the radioactive waste liquid containing α-nuclides to a value within the range of 4 to 11, so that the α-nuclides removal device 14 can efficiently remove α-nuclides.

(Modification)
Modifications of the above embodiment will be described below.

In Example 1, the case of using ferrite as the α nuclide adsorbent was described.
As the α-nuclide adsorbent, in addition to ferrite, the above-described activated carbon and other adsorbents capable of adsorbing α-nuclides can be used.

In Example 1, the α-nuclide adsorbent that adsorbs α-nuclides was injected from the adsorbent injection device 121 into the α-nuclide removal device 14 .
Furthermore, it is also possible to use other adsorbents that adsorb radionuclides other than alpha nuclides and to inject the other adsorbents into the alpha nuclide removal device 14 . Such other adsorbents include, for example, ion exchange resins, chelate resins, activated carbon, oxine-impregnated activated carbon, zeolite, titanic acid, ferrocyanide, and the like.
When using other adsorbents, the other adsorbents are injected from the same adsorbent injection device 121 as the α-nuclide adsorbent, and the other adsorbents are injected from the adsorbent injection device 121 for the α-nuclide adsorbents. A configuration in which an injection device is provided and another adsorbent is injected into the α-nuclide removal device 14 from another injection device is also possible. When another injection device is provided, it becomes possible to make the timing of injection different between the α-nuclide adsorbent and other adsorbents.
Even when other adsorbents are used, the adsorbent separation device 131 can separate the other adsorbents from the radioactive waste liquid.

In the explanation of Example 1, colloidal substances and solids contained in the third radioactive waste liquid were removed by the filter effect of ferrite. That is, ferrite, which is an α-nuclide adsorbent, was also injected into the third radioactive liquid waste that did not contain α-nuclides.
On the other hand, since the third radioactive waste liquid does not contain α-nuclides, it is possible not to inject the α-nuclide adsorbent into the third radioactive waste liquid.
In addition, since the third radioactive waste liquid contains radionuclides other than α nuclides, when using other adsorbents described above, other adsorbents are also injected into the third radioactive waste liquid. Then, for example, when another injection device as described above is provided, it becomes possible to inject only another adsorbent into the third radioactive waste liquid.

In the first embodiment, the adsorbent separation device 131 employs a cross-flow filter system using a membrane having a pore size of μm order or less.
The configuration of the adsorbent separation device 131 is not limited to a cross-flow filter system using a membrane having pores, and other configurations can be adopted. For example, it is possible to employ a dead-end filter method.
Further, for example, when using another adsorbent as described above, two cross-flow filter type adsorbent separation devices are connected in series, and one adsorbent separation device separates the other adsorbent. It is also possible to separate the α nuclide adsorbent in the other adsorbent separation device.

Moreover, when the dead-end filter system is employed in the adsorbent separation device, the adsorbents (α nuclide adsorbent and other adsorbents) are all separated by the filter.
On the other hand, when adopting the cross-flow filter method in the adsorbent separation device, depending on the conditions (particle size of the adsorbent, flow rate and water pressure of the radioactive waste liquid, differential pressure in the filter, etc.), the adsorbent will be filtered. (membrane, etc.) and may flow into the concentrated water after filtration. For example, some adsorbent may flow from the filter media into the retentate and separate from the adsorbent remaining on the filter media.
Therefore, the radioactive waste liquid treatment system and treatment method are not limited to the configuration in which the adsorbent is separated from the radioactive waste liquid in the adsorbent separation device as in each of the above embodiments, and the radioactive waste liquid containing the adsorbent is filtered. It also includes a configuration in which the adsorbent flows through the concentrated water.
When the adsorbent flows into the concentrated water, the concentrated water containing the adsorbent is reduced in volume and solidified by evaporating water. For example, in the radioactive waste liquid treatment system 1 of FIG. Solidify in equipment 21 .
In addition, instead of providing the adsorbent separation device 131 and reusing the filtrate in the chemical cleaning unit 10 as in each embodiment, the adsorbent is removed without providing a filtration device such as an adsorbent separation device. It is also possible to configure such that the contained radioactive waste liquid is dried and solidified.

The present invention is not limited to the above-described embodiments and examples, and includes various modifications. For example, each of the embodiments described above has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the configurations described.

S1... First cleaning process, S2... Second cleaning process, S4... Waste liquid decomposition process, S5... pH adjuster injection process, S6... α nuclide removal process, S7... Adsorbent separation process, 1, 1A... Radioactive waste liquid treatment system , 4... Chemical reaction tank, 7, 52... Organic acid tank, 8, 53... Organic acid salt tank, 9, 54A, 54B... Transfer water tank, 10, 10A... Chemical washing unit, 12... Incineration equipment, 13... Waste liquid decomposition Apparatus 14...α nuclide removal device 17...Reducing agent injection device 17A...Reducing agent tank 19, 19A...Waste liquid treatment unit 20...Drying and pulverization equipment 21...Solidification equipment 49A, 49C...pH meter, 49B... Magnetic susceptibility measuring device, 50... First cleaning tank, 51... Second cleaning tank, 80... Ozone supply device, 81... Ozone injection pipe, 99... Neutralizing liquid injector, 100... Neutralizing liquid tank, 112, 112A ... pH adjuster injection device, 121, 121A ... adsorbent injection device, 131 ... adsorbent separation device

Claims (8)

A radioactive liquid waste treatment method for treating radioactive liquid waste containing α nuclides,
injecting a pH adjuster into the radioactive waste liquid containing the α nuclide;
supplying an α-nuclide adsorbent to the radioactive waste liquid containing the α-nuclide and the pH adjuster;
The α nuclide adsorbent is ferrite,
detecting the ferrite supplied to the radioactive waste liquid by a magnetic susceptibility measuring device;
A method for treating radioactive waste liquid, wherein the α-nuclide is removed from the radioactive waste liquid by adsorbing the α-nuclide with the α-nuclide adsorbent. A radioactive liquid waste treatment method for treating radioactive liquid waste containing α nuclides,
When removing the α-nuclides from the radioactive waste liquid containing nitric acid and the α-nuclides generated by the recovery of uranium and plutonium in nuclear fuel reprocessing,
neutralizing the radioactive waste liquid by injecting a neutralizing agent, which is a pH adjuster, into the radioactive waste liquid;
after that, injecting a reducing agent, which is a pH adjuster, into the radioactive waste liquid containing the α nuclide;
supplying an α-nuclide adsorbent to the radioactive waste liquid containing the α-nuclide and the pH adjuster;
A method for treating radioactive waste liquid, wherein the α-nuclide is removed from the radioactive waste liquid by adsorbing the α-nuclide with the α-nuclide adsorbent. a radioactive waste liquid supply pipe for guiding radioactive waste liquid containing α nuclides;
a pH adjuster injection device connected to the radioactive waste liquid supply pipe and injecting a pH adjuster;
an α-nuclide removal device that is connected to the radioactive waste liquid supply pipe and removes α-nuclides from the radioactive waste liquid containing the α-nuclides;
an adsorbent injection device for injecting an α-nuclide adsorbent that adsorbs the α-nuclides into the α-nuclide removal device;
with
The pH adjuster injection device includes a neutralizing liquid injection device and a reducing agent injection device,
The neutralizing solution for injecting a neutralizing solution containing an alkaline neutralizing agent into the radioactive waste liquid generated by recovery of uranium and plutonium in nuclear fuel reprocessing and containing nitric acid and the α nuclide and flowing through the radioactive waste liquid supply pipe. an injection device connected to the radioactive waste liquid supply pipe upstream of a connection point between the reducing agent injection device for injecting the reducing agent and the radioactive waste liquid supply pipe;
A first pH meter is attached to the radioactive waste liquid supply pipe between a connection point of the reducing agent injection device and the radioactive waste liquid supply pipe and a connection point of the neutralizing liquid injection device and the radioactive waste liquid supply pipe.
A radioactive waste liquid treatment system characterized by: A second pH meter is attached to the radioactive waste liquid supply pipe between the connecting point of the reducing agent injection device and the radioactive waste liquid supply pipe and the α nuclide removal device,
4. The radioactive waste liquid treatment system according to claim 3 , wherein a magnetic susceptibility measuring device is provided in the α nuclide removal device. a radioactive waste liquid supply pipe for guiding radioactive waste liquid containing α nuclides;
a pH adjuster injection device connected to the radioactive waste liquid supply pipe and injecting a pH adjuster;
an α-nuclide removal device that is connected to the radioactive waste liquid supply pipe and removes α-nuclides from the radioactive waste liquid containing the α-nuclides;
an adsorbent injection device for injecting an α-nuclide adsorbent that adsorbs the α-nuclides into the α-nuclide removal device;
with
The injection of the pH adjuster into the radioactive waste liquid is performed when the desired α nuclide concentration is reached.
A radioactive waste liquid treatment system characterized by: 6. The radioactive waste liquid treatment system according to claim 5 , wherein the α-nuclide concentration is measured by analyzing the radioactive waste liquid sampled by a sampling valve attached to the piping upstream of the pH adjuster injector. a radioactive waste liquid supply pipe for guiding radioactive waste liquid containing α nuclides;
a pH adjuster injection device connected to the radioactive waste liquid supply pipe and injecting a pH adjuster;
an α-nuclide removal device connected to the radioactive waste liquid supply pipe for removing α-nuclides from the radioactive waste liquid containing the α-nuclides;
an adsorbent injection device for injecting an α-nuclide adsorbent that adsorbs the α-nuclides into the α-nuclide removal device;
an adsorbent separation device for separating the α-nuclide adsorbent from the radioactive waste liquid containing the α-nuclide adsorbent;
A radioactive liquid waste treatment system comprising: 8. The radioactive waste liquid treatment system according to claim 7 , wherein the adsorbent separation device separates the α-nuclide adsorbent by a cross-flow method using a membrane having a pore size on the order of μm.

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