KR20220166629A - System for treatment of radioactive decontamination waste water using particle electrode and method thereof - Google Patents

Abstract

A treatment method of a radioactive decontamination waste liquid comprises the following steps of: decontaminating a grid or a device of a nuclear power plant contaminated with a radioactive material to generate a radioactive decontamination waste liquid; and locating an anode electrode and a cathode electrode, to which a power supply source is connected, in the radioactive decontamination waste liquid and allowing OH radicals generated on a surface of a particle electrode located between the anode electrode and the cathode electrode to decompose the decontamination waste liquid by a chemical reaction.

Description

Radioactive decontamination waste treatment system and method using particle electrodes

A system and method for treating radioactive decontamination waste using particle electrodes are provided.

When a nuclear power plant is dismantled after operation, a decontamination process is performed to remove radioactive materials from systems and equipment contaminated with radioactive materials. There are various methods of decontamination, such as physical and chemical methods, but systems and devices use chemical decontamination processes to remove radioactive substances. In the case of chemical decontamination, decontamination waste liquid generated in the decontamination process is generated as secondary waste, and it is necessary to develop technology to treat it. In Korea, a chemical decontamination process is performed using an oxidation/reduction process and a hybrid decontamination process, and organic decontamination waste is generated after the process. As a technology for treating organic decontamination waste, there are thermal decomposition technology, UV/photocatalytic decomposition technology, etc., but recently, an electrochemical advanced oxidation process (EAOP) using an electrochemical method has been mainly studied. Electrode materials play an important role in the electrochemical oxidation process of organic matter, and electrode materials that exhibit high economic feasibility, stability, and catalytic activity should be selected. In the case of electrochemical organic material oxidation technology, mainly boron-doped diamond (BDD), graphite, dimensionally stable anodes (DSA) such as RuO ₂ , PbO ₂ , MnO ₂ , SnO ₂ , or Pt Studies using electrode materials are being conducted. BDD electrodes have a high oxygen evolution potential (OEP) and exhibit high stability, but are expensive, and it is difficult to find an electrode material that bonds well with diamond, limiting their application to engineering-scale processes. Among these, the most actively studied anode electrode is the Ti/PbO ₂ electrode, which exhibits appropriate corrosion resistance, high conductivity, and electrochemical catalytic activity. However, the PbO ₂ layer, which is an active layer, may be easily peeled off from the Ti substrate, resulting in reduced activity. Accordingly, there is a need to develop an electrode that exhibits stable and high decomposition efficiency for treating organic decontamination wastewater generated in the decontamination process of nuclear power plants.

Korean Registered Patent No. 10-0339868 discloses a method and apparatus for treating wastewater by an electrode reactor filled with particle electrodes, Chinese Patent No. 101665950 discloses a zirconia carrier composite coated particle electrode and a method for manufacturing the same, and Chinese Patent Publication No. 112591869 discloses a method for treating organic waste liquid.

Korea Patent Registration 10-0339868 Chinese registered patent 101665950 Chinese Patent Publication 112591869

An embodiment is to exhibit stable and high decomposition efficiency in an organic decontamination waste treatment process using an electrochemical oxidation process.

In addition to the above tasks, embodiments according to the present invention may be used to achieve other tasks not specifically mentioned.

A radioactive decontamination waste treatment system according to an embodiment includes a container containing radioactive decontamination waste resulting from decontamination of systems or devices of a nuclear power plant contaminated with radioactive materials, an anode electrode located on one side of the container, and the other inside the container. a cathode electrode facing the anode electrode, a power supply source connected to the anode electrode and the cathode electrode, and a particle electrode containing Y ₂ O ₃ located between the anode electrode and the cathode electrode; It is decomposed by OH radicals generated on the surface of the silver particle electrode.

A method for treating radioactive decontamination waste according to an embodiment includes generating radioactive decontamination waste by decontaminating a system or device of a nuclear power plant contaminated with radioactive materials, and using an anode electrode and a cathode electrode connected to a power supply source to decontaminate the decontamination waste. and generating OH radicals on the surface of the particle electrode positioned between the anode electrode and the cathode electrode to decompose organic matter in the decontamination wastewater.

An embodiment can exhibit stable and high decomposition efficiency in an organic decontamination waste liquid treatment process using an electrochemical oxidation process.

1 is a schematic diagram of an electrochemical organic oxidation reaction.
2 is a schematic diagram of electrochemical oxidative decomposition using a particle electrode.
3 is a graph of electrochemical oxidation and decomposition test results.
4 is a graph of organic matter decomposition rate according to the type of particle electrode.
5 is a schematic diagram of a process for utilizing yttria particle electrodes using a particle bed.

With reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. This invention may be embodied in many different forms and is not limited to the embodiments set forth herein. In order to clearly describe the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are used for the same or similar components throughout the specification. In addition, in the case of widely known known technologies, detailed descriptions thereof will be omitted.

Throughout the specification, when a certain component is said to "include", it means that it may further include other components without excluding other components unless otherwise stated.

Then, a radioactive decontamination waste treatment system and method using a particle electrode according to an embodiment will be described.

A schematic diagram of an organic material oxidation reaction through an electrochemical oxidation reaction is shown in FIG. 1 . Oxidation takes place at the anode electrode, which steals electrons and oxidizes them. After the initial reaction in which OH radicals are generated through water decomposition, direct oxidation, selective oxidation, indirect oxidation, or indirect combustion occur.

The electrode where the selective oxidation reaction occurs is called an active anode, and the organic matter decomposition reaction performed here is as follows.

M + H ₂ O → M( OH) + H ⁺ + e ^-

M( OH) → MO + H ⁺ + e ^-

MO + R → M + RO (Selective oxidation)

MO → M + 1/2O ₂ (Oxygen evolution reaction, OER)

Through strong interaction between the OH radical and the electrode M, the electrode M is partially oxidized to form a higher oxide (MO). After the organic material R is adsorbed on the electrode MO, it is selectively oxidized (RO or R'). In addition, OER (Oxygen evolution reaction), in which oxygen is generated due to oxidation of water, occurs as a side reaction, and this side reaction competes with the selective oxidation reaction of organic matter.

An electrode that does not form higher oxides is called a non-active anode. The oxidation reaction of inactive organics is shown below.

aM( OH) + R → M + mCO ₂ + nH ₂ O + xH ⁺ + ye ^- (Combustion)

(R: organic compound with m carbon atoms)

M( OH) + H ₂ O → M + O ₂ + 3H ⁺ + 3e ^- (Oxygen evolution reaction, OER)

An indirect oxidation reaction occurs as OH radicals physically adsorbed on the surface react with organic matter because they do not react with the electrode. At this time, unlike the selective oxidation that occurs at the active anode, in the oxidation reaction by OH radicals, the entire organic material is oxidized and a = (2m + n) oxygen atoms are mineralized into carbon dioxide. Therefore, it is expressed as being oxidized through a combustion reaction. The inactive anode also generates OER (Oxygen evolution reaction) as a side reaction, and this side reaction competes with the oxidation reaction of organic matter.

In the organic matter decomposition process using electrochemical oxidation, a combustion reaction by OH radicals must occur in order to achieve a high decomposition rate, and an anode electrode material that exhibits a high oxygen evolution potential (OEP) must be used to suppress oxygen generation, a side reaction. should be used From this, for the electrochemical organic oxidation, the anode material must exhibit i) high oxygen evolution potential (OEP), ii) high electrochemical activity, iii) high electrical conductivity, and iv) long-term operation stability.

According to one embodiment, a conceptual diagram of an electrochemical oxidative decomposition reaction using a particle electrode (3D electrode, bed electrode, particle electrode) is shown in FIG. 2 .

Referring to FIG. 2, the radioactive decontamination waste treatment system includes a container containing radioactive decontamination waste generated by decontaminating systems or devices of a nuclear power plant contaminated with radioactive materials, an anode electrode located on one side of the container, and Located on the other side, a cathode electrode facing the anode electrode, a power supply connected to the anode electrode and the cathode electrode, and a particle electrode positioned between the anode electrode and the cathode electrode and containing Y ₂ O ₃ , decontamination The waste liquid is decomposed by OH radicals generated on the surface of the particle electrode.

An electrochemical reaction in which a first OH radical is generated from water molecules occurs at the anode electrode, and a second OH radical is additionally generated at the particle electrode, whereby a chemical reaction in which decontamination wastewater is decomposed to generate carbon dioxide and water occurs. The particle electrode includes a polarized cathode in which one side is polarized to (-) and a polarized anode in which the other side is polarized to (+), and the second OH radical is generated at the polarized anode. A chemical reaction takes place.

The particle electrode is dispersed in a medium between the anode and the cathode in the reactor, and an additional second OH radical generation reaction occurs by the particle electrode. As shown in FIG. 5, the particle electrode may be filled in a medium composed of a mesh-type bed, and in this case, the particle electrode is easily recovered. For example, the medium in the form of a bed may be made of a polymeric material. Since the particle electrode is an electrode other than a conventional anode electrode or cathode electrode, it is called a 3D electrode, and when forming a bed, it is also called a bed electrode. The particle electrode existing between the anode and the cathode is polarized by an electric field, and at this time, the polarization formed on the particle surface acts as a polarized anode/cathode, respectively, and each polarized particle forms a microelectrode. It can be formed to perform additional organic oxidation reactions.

According to one embodiment, in order to treat the nuclear organic decontamination wastewater (oxidize organic matter in the decontamination wastewater and decompose it into water and carbon dioxide), an electrochemical oxidation process is applied, and Y ₂ O ₃ oxide is applied as a particle electrode, which A process for decomposing organic matter using

Y ₂ O ₃ may be used in an amount of about 200 mg to about 2000 mg based on 100 mL of decontamination waste solution, and when it is about 200 mg or more, decomposition reaction of decontamination waste solution due to generation of OH radicals can occur sufficiently, and when it is about 2000 mg or less, high polarization efficiency can be achieved.

The power supply source can supply a constant current of about 50 mA to about 200 mA based on 100 mL of the decontamination waste solution, and in the case of about 50 mA or more, polarization of the particle electrode can easily occur, and in the case of about 200 mA or less, high current efficiency can be achieved

A method for treating radioactive decontamination waste according to an embodiment includes generating radioactive decontamination waste by decontaminating a system or device of a nuclear power plant contaminated with radioactive materials, and using an anode electrode and a cathode electrode connected to a power supply source to decontaminate the decontamination waste. and decomposing the decontamination wastewater by a chemical reaction with OH radicals generated on the surface of the particle electrode located in the inside and located between the anode electrode and the cathode electrode.

The radioactive decontamination waste liquid treatment method may further include generating carbon dioxide and water by decomposing the decontamination waste liquid by OH radicals in a particle electrode.

The method of treating radioactive decontamination waste may further include a polarization step of polarizing one side to (-) and polarizing the other side to (+) in the particle electrode.

Hereinafter, the present invention will be described in more detail with examples, but the following examples are only examples of the present invention and the present invention is not limited to the following examples.

Example

Electrochemical oxidative decomposition test conditions using a Y ₂ O ₃ particle electrode are as follows. A platinum mesh (Pt mesh) is used as the anode/cathode, and an Ag/AgCl electrode is used as the reference electrode. SDBS (Sodium dodecylbenzenesulfonate) surfactant, a representative decontamination agent present in organic decontamination waste, is selected as a representative organic material and the decomposition rate is evaluated. About 100 mL of simulated organic waste solution containing about 500 ppm SDBS was subjected to an oxidation reaction for about 2 hours under about 0.01 M Na ₂ SO ₄ electrolyte conditions, using galvanostatic conditions of about 50 mA and about 100 mA. carry out About 200 mg and about 2,000 mg of the particle electrode are injected into the simulated lung fluid. In order to evaluate the decomposition rate of the electrochemical oxidation process of the organic decontamination wastewater, a chemical oxygen demand (COD) analysis is performed to measure the amount of oxygen required for oxidation of the remaining organic matter in the sample. The COD measurement method uses the potassium permanganate method in an acidic solution. The test procedure is in accordance with the water pollution process test standard.

First, in order to determine the effect of the particle electrode, an electrochemical oxidation test is performed using only a platinum anode and a platinum cathode electrode without introducing particles. The disassembly test is performed under the condition of about 50 mA constant current. In order to determine the effect of the Y ₂ O ₃ particle electrode, about 200 mg of Y ₂ O ₃ is injected into the simulated decontamination waste, and then a decomposition test is performed under the condition of about 50 mA constant current. In order to determine the effect of the particle amount, about 2,000 mg of Y ₂ O ₃ was added under the same conditions and a decomposition test was performed under the same conditions. In addition, in order to determine the current condition, about 2000 mg of Y ₂ O ₃ was added, and then a decomposition test was performed for about 2 hours under the increased condition of about 100 mA. The change in voltage when the decomposition test is performed under constant current conditions is shown in FIG. 3 . It maintains within 2V under the condition of about 50 mA, and within about 2.5 V under the condition of about 100 mA.

After the decomposition test, the treatment solution is sampled and organic matter concentration analysis is performed using the COD analysis method. In addition, in order to calculate the organic matter decomposition rate, the initial organic matter concentration of the simulated waste liquid containing about 500 ppm of SDBS was analyzed. The degradation efficiency (%) of the organic waste liquid is evaluated using the following formula. COD _initial represents about 142 mg/L, which is a blank as an initial value, and COD _final represents the value after the electrochemical oxidation test under each condition.

[Equation 1]

Degradation rate (%) = (COD _initial - COD _final )/COD _initial

The analysis results are shown in Table 1. Further, the decomposition rate under each condition is shown in FIG. 4 . The decomposition rate without the particle electrode is about 7%. It can be seen that organic matter is hardly decomposed when a platinum anode and a platinum cathode electrode are used. However, when a small amount of about 200 mg of particles was added, the decomposition rate increased to about 31%, indicating that the organic matter was oxidatively decomposed by the particle electrode. It can be seen that when an excess of about 2000 mg was added, the decomposition rate increased to about 53.5%. In addition, it can be seen that a high decomposition rate of about 97.2% was achieved under the condition of about 100 mA constant current in which the current condition was increased to increase the decomposition rate.

Table 1 shows the chemical oxygen demand and organic waste liquid decomposition rate after the electrochemical oxidative decomposition test.

chemical oxygen demand
(COD, mg/L) Degradation rate (%) Initial solution (500ppm SDBS) 142 - Without particle 132 7.0 Y ₂ O ₃ _200mg_50mA 98 31.0 Y ₂ O ₃ 2,000mg_50mA 66 53.5 Y ₂ O ₃ 2,000mg_100mA 4 97.2

As described above, when organic matter in organic decontamination wastewater generated in the decontamination process after decommissioning of nuclear power plants is decomposed using the electrochemical oxidation process, manufacturing is simple compared to conventional electrodes, and it uses polarization, which exhibits a high decomposition rate with improved stability. A particle electrode is introduced into the waste fluid. From this, a high organic matter decomposition rate of up to about 97% or more is achieved. When using the Y ₂ O ₃ particle electrode material and the above process, a high decomposition rate can be achieved in organic decontamination waste treatment. In addition, the above-described process can be operated not only by dispersing the particle electrode powder in the waste liquid, but also in the form of a packed bed in which granules, not powder, are loaded into a mesh, as shown in FIG.

When organic decontamination wastewater is treated using the Y ₂ O ₃ particle electrode according to an embodiment, the following is performed.

In the electrochemical oxidative decomposition process, the oxide-based electrode exhibiting a high decomposition rate is peeled off from the substrate and commercialization is difficult. commercialization is possible.

Environmentally problematic PbO ₂ -based electrodes can be replaced with Y ₂ O ₃ particle electrodes.

Organic decontamination wastewater generated from systemic decontamination and instrumental decontamination during the decontamination process of nuclear power plants can be treated using a simple process, and an electrode manufacturing process is unnecessary.

It is a technology that can improve the decomposition rate compared to the conventional process by injecting the Y ₂ O ₃ particle electrode into the conventional electrochemical organic matter decomposition process, and can be directly applied to the conventional decomposition process, enabling rapid commercialization.

The Y ₂ O ₃ particle electrode can be used not only for organic decontamination waste but also for other wastewater and polluted water treatment.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in the following claims are also made according to the present invention. falls within the scope of the rights of

Claims (11)

A container containing radioactive decontamination waste liquid generated by decontamination of systems or devices of nuclear power plants contaminated with radioactive materials,
An anode electrode located on one side of the container,
A cathode electrode located on the other side of the container and facing the anode electrode;
A power supply source connected to the anode electrode and the cathode electrode, and
A particle electrode positioned between the anode electrode and the cathode electrode and containing Y ₂ O ₃
including,
The decontamination waste liquid is decomposed by OH radicals generated on the surface of the particle electrode.
In paragraph 1,
A first electrochemical reaction in which first OH radicals are generated from water molecules occurs at the anode electrode, and a second electricity in which carbon dioxide and water are generated by decomposition of decontamination wastewater due to generation of additional second OH radicals at the particle electrode A radioactive decontamination waste treatment system in which a chemical reaction takes place.
In paragraph 2,
The particle electrode includes a polarized cathode whose one side is polarized to (-) and a polarized anode whose other side is polarized to (+), and the second electrochemical reaction occurs at the polarized anode. This is the radioactive decontamination waste treatment system.
In paragraph 1,
The particle electrode includes a plurality of Y ₂ O ₃ particles dispersed in the decontamination waste liquid, and each of the plurality of Y ₂ O ₃ particles is polarized.
In paragraph 1,
Based on 100 mL of the decontamination waste solution, the Y ₂ O ₃ is 200 mg to 2000 mg of radioactive decontamination waste treatment system.
In paragraph 5,
Based on 100 mL of the decontamination waste solution, the power supply source supplies a constant current of 50 mA to 200 mA.
In paragraph 1,
The radioactive decontamination waste liquid treatment system in which the particle electrode is filled in a medium composed of a mesh-type bed.
Decontamination of systems or devices of nuclear power plants contaminated with radioactive materials to generate radioactive decontamination waste, and
An anode electrode and a cathode electrode to which a power supply source is connected are located in the decontamination waste liquid, and OH radicals generated on the surface of a particle electrode positioned between the anode electrode and the cathode electrode decompose the decontamination waste liquid by a chemical reaction. Method for treating radioactive decontamination waste containing a.
In paragraph 8,
The radioactive decontamination wastewater treatment method further comprising generating first OH radicals from water molecules in the anode electrode.
In paragraph 8,
The radioactive decontamination waste treatment method further comprising the step of generating carbon dioxide and water by decomposing the decontamination waste solution by the second OH radical additionally generated in the particle electrode.
In paragraph 8,
In the particle electrode, a method of treating radioactive decontamination waste liquid further comprising a polarization step of polarizing one side to (-) and polarizing the other side to (+).

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