Complex decontamination apparatus

Abstract

The present invention relates to a composite decontamination device. A composite decontamination device according to one embodiment of the present invention is a composite decontamination device for removing an oxide film formed on the surface of radioactive metal waste generated in a nuclear power plant, comprising: at least one decontamination agent supply unit that generates a chemical decontamination agent by mixing pure water and a plurality of chemical agents; a decontamination unit that receives radioactive metal waste inside and performs a decontamination process to remove an oxide film formed on the surface of the radioactive metal waste using a chemical decontamination agent supplied from any one of the at least one decontamination agent supply units; a waste liquid treatment unit that receives the decontamination waste liquid after the decontamination process is completed from the decontamination unit and purifies the decontamination waste liquid; and a control unit connected to at least one decontamination agent supply unit, the decontamination unit, and the waste liquid treatment unit, and controls the operation of at least one decontamination agent supply unit, the decontamination unit, and the waste liquid treatment unit, wherein the chemical decontamination agent is an inorganic acid-based chemical decontamination agent.

Description

Technology Field

[0001] The present invention relates to a composite decontamination device, and more specifically, to a composite decontamination device that can not only improve the efficiency of the decontamination process for radioactive metal waste compared to existing organic acid-based chemical decontamination methods, but is also applicable to radioactive metal waste having various types, shapes, sizes, etc. Background Technology

[0002] Generally, nuclear power plants are divided into a primary system, in which coolant circulates from the reactor to the steam generator containing radioactive material, and a secondary system, in which steam generated in the steam generator circulates through the turbine and generator to produce electricity. In the primary system, coolant containing radioactive material flows through direct contact with the reactor.

[0003] Radioactive metal waste generated at nuclear power plants includes metal components, waste from on-site equipment, and tools used during the power generation process. Decontamination processes must be performed on this radioactive metal waste to reduce worker radiation exposure and prevent the spread of radioactive contaminants. These decontamination processes are applied to primary system decontamination prior to decommissioning, decontamination during operation, and the decontamination of various metal wastes generated during maintenance.

[0004] Decontamination processes for radioactive metal waste whose surfaces are contaminated by radioactive materials are classified into physical decontamination, chemical decontamination, and electrochemical decontamination.

[0005] Among these, the chemical decontamination method is a process that performs the decontamination of radioactive metal waste by removing oxide films containing radioactive contaminants from the radioactive metal waste using chemical decontamination agents such as sulfuric acid and nitric acid. Compared to the physical decontamination process, which has low decontamination efficiency and is difficult to remove due to adherent contamination, or the electrolytic decontamination process, which is unsuitable for radioactive metal waste with complex shapes, the chemical method is frequently used because it is effective for radioactive metal waste with complex shapes, such as curved pipes or valves.

[0006] Most chemical decontamination methods already commercialized use organic acid complexing agents such as oxalic acid, ethylenediaminetetraacetic acid, and picolinic acid, which are known to form strong complexes.

[0007] For example, Korean registered patent publication No. 10-1860002 (continuous chemical decontamination method for removing radioactive contaminants from nuclear power plants) (published May 21, 2018) and Korean registered patent publication No. 10-2122164 (method for decontaminating metal surfaces of nuclear power plants) (published June 12, 2020) disclose a technology for removing a metal oxide film containing iron, nickel, etc. present on the surface of an object to be decontaminated by introducing an organic acid such as oxalic acid into a decontamination tank.

[0008] However, conventional organic acid-based chemical decontamination methods have the problem that, in order to minimize the amount of radioactive waste generated after decontamination, they must be decomposed or adsorbed onto ion exchange resins. Furthermore, they require separate devices such as UV irradiation devices to decompose organic acid complexing agents such as oxalic acid, and if the organic acid complexing agents are not completely decomposed, they must also be treated as radioactive waste, which increases the amount of secondary waste generated.

[0009] In addition, conventional organic acid-based chemical decontamination methods had the problem of significantly reducing the disposal stability of radioactive waste even when organic acid complexing agents were adsorbed by ion exchange resins.

[0010] Therefore, there is a need for a composite decontamination device that can solve the problems of existing organic acid-based chemical decontamination methods and improve the efficiency of the decontamination process for radioactive metal waste compared to existing organic acid-based chemical decontamination methods, as well as be applicable to radioactive metal waste of various types, shapes, and sizes. Prior art literature

[0011] Korean Registered Patent Publication No. 10-1860002 (Continuous chemical decontamination method for removing radioactive contaminants from nuclear power plants) (Published May 21, 2018) Korean Registered Patent Publication No. 10-2122164 (Method for decontaminating metal surfaces of a nuclear power plant) (Published June 12, 2020) The problem to be solved

[0012] The present invention was developed to improve upon the aforementioned problems. The objective of the present invention is to provide a composite decontamination device that can improve decontamination performance by using an inorganic acid-based chemical decontamination method to perform a decontamination process for removing an oxide film formed on the surface of radioactive metal waste, thereby increasing the oxide film removal rate while minimizing corrosion of the radioactive metal waste compared to the existing organic acid-based chemical decontamination method, and also reduce the amount of secondary radioactive waste generated after the decontamination process.

[0013] The technical problems of the present invention are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[65535] To achieve the above objective, a composite decontamination device according to one embodiment of the present invention, for removing an oxide film formed on the surface of radioactive metal waste generated in a nuclear power plant, comprises: at least one decontamination agent supply unit for generating a chemical decontamination agent by mixing pure water and a plurality of chemical agents; a decontamination unit that accommodates radioactive metal waste and performs a decontamination process for removing an oxide film formed on the surface of the radioactive metal waste using the chemical decontamination agent supplied from any one of the at least one decontamination agent supply units; and a waste liquid treatment unit for receiving the decontamination waste liquid after the decontamination process is completed from the decontamination unit and purifying the decontamination waste liquid. The apparatus comprises a control unit connected to at least one decontamination agent supply unit, the decontamination unit, and the waste liquid treatment unit, and controlling the operation of the at least one decontamination agent supply unit, the decontamination unit, and the waste liquid treatment unit, wherein the chemical decontamination agent is an inorganic acid-based chemical decontamination agent. At this time, the inorganic acid is characterized as being one or more inorganic acids selected from the group consisting of hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), phosphoric acid (H3PO4), hydrogen bromide (HBr), hydrogen fluoride (HF), and hydrogen iodide (HI). Additionally, the chemical decontamination agent is characterized as further comprising cerium. Furthermore, the decontamination agent supply unit is provided in multiple units, and the control unit is characterized as selecting a first decontamination agent supply unit, which is one of the multiple decontamination agent supply units, according to the radioactive metal waste contained inside the decontamination unit, and then supplying the chemical decontamination agent from the first decontamination agent supply unit to the decontamination unit.Additionally, the decontamination unit comprises: a decontamination tank having an open top and a receiving space formed inside for placing the radioactive metal waste, and equipped with a decontamination agent inlet on one side for introducing the chemical decontamination agent and a waste liquid discharge outlet for discharging the decontamination waste liquid; a basket rotatably coupled to the open top or inside of the decontamination tank and containing the radioactive metal waste; and a basket driving unit provided on one side of the decontamination tank and generating a driving force to drive the basket. The device is characterized by including an opening / closing cover that opens and closes the open upper portion of the decontamination tank. Additionally, the decontamination unit is further characterized by including at least one ultrasonic generator that is provided inside the decontamination tank and generates ultrasonic waves toward the radioactive metal waste while the decontamination process is performed. Furthermore, the composite decontamination device is further characterized by including an ozone supply unit that supplies ozone to the chemical decontamination agent discharged from the decontamination unit after the decontamination process is completed. Meanwhile, to achieve the above objective, a composite decontamination device according to one embodiment of the present invention is a composite decontamination device for removing an oxide film formed on the surface of radioactive metal waste generated in a nuclear power plant, comprising: a decontamination agent supply unit that generates a chemical decontamination agent by mixing pure water, an oxidizing agent, and an inorganic acid; and a decontamination unit that receives radioactive metal waste inside and performs a chemical decontamination process using the chemical decontamination agent supplied from the decontamination agent supply unit and an ultrasonic decontamination process using ultrasonic waves generated from an ultrasonic generator to remove the oxide film formed on the surface of the radioactive metal waste. It is characterized by including: an ozone supply unit that receives the chemical decontamination agent that has completed the decontamination process from the decontamination unit and supplies ozone to reduce and regenerate the oxidizing agent; and a waste liquid treatment unit that receives the decontamination waste liquid that has completed the decontamination process from the decontamination unit and purifies the decontamination waste liquid.At this time, the above oxidizing agent is characterized by using cerium(IV) sulfate (Ce(SO4)2) and the inorganic acid is characterized by using sulfuric acid (H2SO4). Furthermore, the above cerium(IV) sulfate (Ce(SO4)2) is characterized by using a concentration of 0.01 M and the above sulfuric acid (H2SO4) is characterized by using a concentration of 0.2 M. Furthermore, the above chemical decontamination agent is characterized by being used after heating to 60 ℃. Furthermore, the above ultrasonic generator is characterized by generating ultrasound of 40 kHz and irradiating the above radioactive metal waste. Specific details of other embodiments are included in the detailed description and drawings. Effects of the invention

[0027] According to a composite decontamination device according to one embodiment of the present invention, by using an inorganic acid-based chemical decontamination method to perform a decontamination process for removing an oxide film formed on the surface of radioactive metal waste, it is possible to improve decontamination performance by increasing the oxide film removal rate while minimizing corrosion of radioactive metal waste compared to existing organic acid-based chemical decontamination methods, and also reduce the amount of secondary radioactive waste generated after the decontamination process.

[0028] In addition, according to a composite decontamination device of one embodiment of the present invention, a plurality of decontamination agent supply units storing a plurality of chemical decontamination agents are provided, and by configuring to select one of the plurality of decontamination agent supply units to supply a chemical decontamination agent according to the radioactive metal waste to be decontaminated, the decontamination process can be performed universally for radioactive metal waste having various types, shapes, sizes, etc., thereby reducing the time and cost of the decontamination process and maximizing the efficiency of the decontamination process.

[0029] In addition, according to a composite decontamination device of one embodiment of the present invention, by combining an inorganic acid-based chemical decontamination method with an ultrasonic decontamination method, the decontamination process time for radioactive metal waste contaminated with adhesion and radioactive metal waste of complex shape can be significantly shortened, thereby improving the efficiency of the decontamination process.

[0030] Meanwhile, according to a preferred embodiment of the present invention, a composite decontamination device is used to perform a composite decontamination process consisting of a chemical decontamination process using a chemical decontamination agent comprising an oxidizing agent and an inorganic acid, and an ultrasonic decontamination process using ultrasound. By regenerating the oxidizing agent constituting the chemical decontamination agent after the chemical decontamination process using ozone, the decontamination performance for radioactive metal waste can be significantly improved, and the generation of secondary waste can be minimized.

[0031] In addition, according to a preferred embodiment of the present invention, a chemical decontamination agent is prepared by mixing cerium (IV) sulfate (Ce(SO4)2) at a concentration of 0.015 M, which is an oxidizing agent, with sulfuric acid (H2SO4) at a concentration of 0.2 M, which is an inorganic acid. Then, by heating to 60 ℃ to perform a chemical decontamination process and irradiating with ultrasound at 40 kHz to perform an ultrasonic decontamination process, a composite decontamination device having commercially viable technology can be manufactured to perform a decontamination process that satisfies decontamination performance, decontamination efficiency, and economic feasibility.

[0032] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims. Brief explanation of the drawing

[0033] FIG. 1 is a diagram schematically showing the structure of a composite decontamination device according to one embodiment of the present invention. FIG. 2 is a diagram showing the operation of a control unit constituting a composite decontamination device according to one embodiment of the present invention controlling a plurality of decontamination agent supply units. FIG. 3 is a diagram schematically showing the structure of a decontamination unit constituting a composite decontamination device according to one embodiment of the present invention. FIG. 4 is a diagram schematically showing the structure of a decontamination unit constituting a composite decontamination device according to one embodiment of the present invention when the decontamination unit includes an ultrasonic generating unit. FIG. 5 is a schematic diagram showing the structure of a composite decontamination device according to one embodiment of the present invention when it includes an ozone supply unit. FIG. 6 is a diagram showing the structure of a composite decontamination device according to a preferred embodiment of the present invention. FIG. 7 is a flowchart showing the process of a composite decontamination process using a composite decontamination device according to a preferred embodiment of the present invention. FIGS. 8 to 14 are drawings showing the results of an experimental example of a composite decontamination process using a composite decontamination device according to a preferred embodiment of the present invention. Specific details for implementing the invention

[0034] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings so that a person skilled in the art to which the present invention pertains can easily practice the present invention.

[0035] In describing the embodiments, technical details that are well known in the art to which the present invention belongs and are not directly related to the present invention are omitted. This is intended to convey the essence of the present invention more clearly without obscuring it by omitting unnecessary explanations.

[0036] For the same reason, some components in the attached drawings have been exaggerated, omitted, or schematically depicted. Additionally, the size of each component does not entirely reflect its actual dimensions. Identical or corresponding components in each drawing have been assigned the same reference numbers.

[0037] Additionally, regarding terms such as device or element orientation (e.g., "front," "back," "up," "down," "top," "bottom," "left," "right," "lateral"), it will be understood that the expressions and terms used herein are used merely to simplify the description of the invention and do not indicate or imply that the related device or element must simply have a specific orientation.

[0038] Hereinafter, the present invention will be described with reference to the drawings for explaining a composite decontamination device according to one embodiment of the present invention.

[0039] FIG. 1 is a diagram schematically showing the structure of a composite decontamination device according to one embodiment of the present invention.

[0040] As illustrated in FIG. 1, a composite decontamination device (1) according to one embodiment of the present invention may be configured to include at least one decontamination agent supply unit (100), a decontamination unit (200), a waste liquid treatment unit (300), and a control unit (400). This composite decontamination device (1) can perform a decontamination process to remove an oxide film formed on the surface of radioactive metal waste (M) generated in a nuclear power plant, particularly small and medium-sized radioactive metal waste (M) such as metal cuttings, valves, and fittings.

[0041] The decontamination agent supply unit (100) can produce a chemical decontamination agent in liquid form by mixing pure water (W) and a plurality of chemical agents (c1, c2, c3, c4, cn). At least one such decontamination agent supply unit (100) is provided, but preferably, a plurality of units (100A, 100B, 100C in the example of FIG. 1) may be provided depending on the type of chemical decontamination agent.

[0042] As illustrated in FIG. 1, a plurality of decontamination agent supply units (100A, 100B, 100C) are connected through piping (dotted line portion) to a pure water supply unit (110) in which pure water (W) is stored and a plurality of chemical supply units (120) in which a plurality of chemical agents (c1, c2, c3, c4, cn) are stored, and can produce a plurality of chemical decontamination agents required for a decontamination process by receiving pure water (W) from the pure water supply unit (110) and receiving a plurality of chemical agents (c1, c2, c3, c4, cn) from the plurality of chemical supply units (120).

[0043] Although not described in detail, each decontamination agent supply unit (100A, 100B, 100C) may selectively receive some of the chemical agents (c1, c2, c3, c4, cn) for producing a specific chemical decontamination agent from some of the multiple chemical supply units (120).

[0044] FIG. 1 illustrates an example in which a composite decontamination device (1) is equipped with three decontamination agent supply units (100A, 100B, 100C), but is not limited thereto, and the type and number of decontamination agent supply units (100) can be changed by a person skilled in the art in consideration of the type, shape, size, etc. of the radioactive metal waste (M) to be decontaminated.

[0045] The decontamination unit (200) contains radioactive metal waste (M) to be decontaminated inside, and can perform a decontamination process to remove an oxide film formed on the surface of the radioactive metal waste (M) using a chemical decontamination agent selectively supplied from at least one of the decontamination agent supply units (100). The specific structure of the decontamination unit (200) will be described later with reference to FIGS. 3 and FIGS. 4.

[0046] The waste liquid treatment unit (300) is connected to the decontamination unit (200) through a pipe (dotted line portion), and can receive the decontamination waste liquid that has completed the decontamination process from the decontamination unit (200) and purify the decontamination waste liquid.

[0047] The control unit (400) is electrically connected (dotted line portion) to the pure water supply unit (110), the plurality of chemical supply units (120), at least one decontamination agent supply unit (100), the decontamination unit (200), and the waste liquid treatment unit (300), and can control the operation of the pure water supply unit (110), the plurality of chemical supply units (120), at least one decontamination agent supply unit (100), the decontamination unit (200), and the waste liquid treatment unit (300).

[0048] For convenience of explanation, in FIG. 1, the piping structure (dotted line portion) connecting at least one decontamination agent supply unit (100), decontamination unit (200), and waste liquid treatment unit (300) constituting the composite decontamination device (1) is simplified, and components installed in the piping, such as pumps, valves, and temperature / pressure / flow rate measuring means, in relation to the operation of at least one decontamination agent supply unit (100), decontamination unit (200), and waste liquid treatment unit (300), have been omitted.

[0049] Preferably, a composite decontamination device (1) according to one embodiment of the present invention may use an inorganic acid-based chemical decontamination agent to perform a decontamination process for removing an oxide film formed on the surface of radioactive metal waste (M).

[0050] Accordingly, the composite decontamination device (1) according to one embodiment of the present invention has the advantage of being able to increase the oxide film removal rate while minimizing corrosion of radioactive metal waste (M) compared to the existing organic acid-based chemical decontamination method, and reducing the amount of secondary radioactive waste generated after the decontamination process.

[0051] In particular, a composite decontamination device (1) according to one embodiment of the present invention may use a chemical decontamination agent mixed with an oxidizing agent, a reducing agent, a metal ion, and an inorganic acid to remove an oxide film formed on the surface of radioactive metal waste (M).

[0052] For example, the chemical decontamination agent used in the composite decontamination device (1) according to one embodiment of the present invention may include an oxidizing agent, a metal ion, and an inorganic acid. In this case, the oxidizing agent uses one or more oxidizing agents selected from the group consisting of KMnO4, NaMnO4, H2CrO4, and HMnO4, and the metal ion is Cu 2+ , Fe 3+ , Cr 3+ , Ni 2+ and Zn 2+ One or more metal ions selected from the group consisting of can be used.

[0053] Preferably, one or more inorganic acids selected from the group consisting of hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), phosphoric acid (H3PO4), hydrogen bromide (HBr), hydrogen fluoride (HF), and hydrogen iodide (HI) may be used.

[0054] As such, when a chemical decontamination agent contains an oxidizing agent, metal ions, and inorganic acids, it has the advantage of minimizing corrosion of radioactive metal waste (M) to be decontaminated and reducing the amount of secondary waste generated compared to conventional organic acid-based chemical decontamination agents.

[0055] As another example, the chemical decontamination agent used in the composite decontamination device (1) according to one embodiment of the present invention may include a reducing agent, a metal ion, and an inorganic acid. In this case, the reducing agent uses one or more reducing agents selected from the group consisting of NaBH4, H2S, N2H4, and LiAlH4, and the metal ion is Ag + , Ag 2+ , Co 2+ , Co 3+ , Cr 2+ , Cr 3+ , Cu + , Cu 2+ , Mn 2+ , Mn 3+ , Sn 2+ , Sn 4+ , Ti 2+ and Ti 3+ One or more reducing metal ions selected from the group consisting of can be used.

[0056] Preferably, one or more inorganic acids selected from the group consisting of hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), phosphoric acid (H3PO4), hydrogen bromide (HBr), hydrogen fluoride (HF), and hydrogen iodide (HI) may be used.

[0057] As such, when a chemical decontamination agent contains a reducing agent, metal ions, and inorganic acids, it has the advantage of solving the problem of requiring a separate device to purify organic acids compared to existing organic acid-based chemical decontamination agents, and the problem of reducing the disposal stability of radioactive waste when adsorbing organic acids by ion exchange resins, and reducing the amount of secondary waste generated.

[0058] Preferably, the chemical decontamination agent used in the composite decontamination device (1) according to one embodiment of the present invention may include an oxidizing agent and an inorganic acid. In this case, the oxidizing agent may include cerium, and the inorganic acid may be one or more inorganic acids selected from the group consisting of hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), phosphoric acid (H3PO4), hydrogen bromide (HBr), hydrogen fluoride (HF), and hydrogen iodide (HI).

[0059] As such, when a chemical decontamination agent contains an oxidizing agent and an inorganic acid, and the oxidizing agent contains cerium, it has the advantage of being able to effectively remove sparingly soluble chromium oxide compared to conventional organic acid-based chemical decontamination agents, as well as regenerate and reuse the decontamination agent without performance degradation, thereby reducing the amount of secondary waste generated. This will be described in detail later through experimental examples.

[0060] Meanwhile, a composite decontamination device (1) according to one embodiment of the present invention can perform a decontamination process for radioactive metal waste (M) by selectively supplying one of a plurality of chemical decontamination agents generated in each of at least one decontamination agent supply unit (100).

[0061] FIG. 2 is a diagram showing the operation of a control unit constituting a composite decontamination device according to one embodiment of the present invention controlling a plurality of decontamination agent supply units.

[0062] As shown in FIG. 2, at least one decontamination agent supply unit (100A, 100B, 100C) is each connected to a decontamination unit (200) through a pipe (dotted line portion), and a switching valve (130) for selectively supplying chemical decontamination agents (D1, D2, D3) may be installed between the pipe supplying chemical decontamination agents (D1, D2, D3) from each of the at least one decontamination agent supply unit (100A, 100B, 100C) and the pipe connecting the decontamination unit (200).

[0063] Preferably, the control unit (400) can select a first decontamination agent supply unit (100A), which is one of at least one decontamination agent supply unit (100A, 100B, 100C), according to the radioactive metal waste (M) contained inside the decontamination unit (200), and then control the supply of a chemical decontamination agent (D1) from the selected first decontamination agent supply unit (100A) to the decontamination unit (200).

[0064] That is, the control unit (400) determines the type, shape, size, etc. of the radioactive metal waste (M) contained within the decontamination unit (200), and if, based on the determination result, selects a first chemical decontamination agent (D1) suitable for the decontamination process of the radioactive metal waste (M) from among a plurality of chemical decontamination agents (D1, D2, D3) generated in each of at least one decontamination agent supply unit (100A, 100B, 100C), the control unit (400) can control the first decontamination agent supply unit (100A) where the first chemical decontamination agent (D1) is stored and the switching valve (130) to supply the first chemical decontamination agent (D1) to the decontamination unit (200).

[0065] Accordingly, the composite decontamination device (1) according to one embodiment of the present invention has the advantage of being universally applicable to radioactive metal waste (M) having various types, shapes, sizes, etc. by selectively controlling at least one of the decontamination agent supply units (100A, 100B, 100C).

[0066] Hereinafter, with reference to FIGS. 3 and FIGS. 4, the structure of a decontamination unit (200) constituting a composite decontamination device (1) according to one embodiment of the present invention will be described.

[0067] FIG. 3 is a diagram schematically showing the structure of a decontamination unit constituting a composite decontamination device according to one embodiment of the present invention.

[0068] As illustrated in FIG. 3, the decontamination unit (200) may be configured to include a decontamination tank (210), a basket (220), a basket drive unit (230), and an opening / closing cover (240).

[0069] The decontamination tank (210) may have an open top and a receiving space (211) formed inside in which radioactive metal waste (M) is placed. Additionally, the decontamination tank (210) may be provided with a decontamination agent inlet (212) into which a chemical decontamination agent (D1) is introduced on one side (left center in the example of FIG. 3) and a waste liquid discharge (213) into which a decontamination waste liquid (W1) is discharged on the other side (right bottom in the example of FIG. 3).

[0070] Although not shown, the decontamination tank (210) may be equipped with a spraying means (not shown), such as a nozzle, positioned adjacent to the radioactive metal waste (M) to be decontaminated.

[0071] A basket (220) is rotatably coupled to the open top or inside of a decontamination tank (210) and can hold radioactive metal waste (M). Additionally, a basket drive unit (230) is provided on one side of the decontamination tank (210) (in the example of FIG. 3, the upper right) and can generate a driving force to drive the basket (220).

[0072] The opening / closing cover (240) is detachably coupled to the open top of the decontamination tank (210) and can open and close the open top of the decontamination tank (210).

[0073] Meanwhile, a composite decontamination device (1) according to one embodiment of the present invention can perform a decontamination process by using both an inorganic acid-based chemical decontamination method and an ultrasonic decontamination method to improve the decontamination efficiency for radioactive metal waste (M).

[0074] FIG. 4 is a schematic diagram showing the structure of a decontamination unit constituting a composite decontamination device according to one embodiment of the present invention when the decontamination unit includes an ultrasonic generating unit (250).

[0075] As illustrated in FIG. 4, when performing a decontamination process using an inorganic acid-based chemical decontamination method and an ultrasonic decontamination method simultaneously, the decontamination unit (200) may include an ultrasonic generating unit (250) in addition to a decontamination tank (210), a basket (220), a basket driving unit (230), and an opening / closing cover (240).

[0076] An ultrasonic generator (250) is provided inside the decontamination tank (210) and can generate ultrasonic waves toward radioactive metal waste (M) while the decontamination process is being performed. As shown in FIG. 4, the ultrasonic generator (250) is positioned between the inner surface of the decontamination tank (210) and the outer surface of the basket (220), and multiple units may be installed as needed. FIG. 4 illustrates an example in which multiple ultrasonic generators (250) are provided on the side and bottom surfaces of the decontamination tank (210), but the number and arrangement of the ultrasonic generators (250) can be changed by a person skilled in the art.

[0077] Meanwhile, the inorganic acid-based chemical decontamination agent used in the composite decontamination device (1) according to one embodiment of the present invention may further include cerium. That is, by including cerium as an oxidizing agent, the speed of the decontamination process can be further increased.

[0078] Preferably, the inorganic acid-based chemical decontamination agent may include one or more oxidizing agents selected from the group consisting of cerium nitrate (Ce(NO3)4), cerium (IV) sulfate (Ce(SO4)2), and cerium (III) sulfate (Ce2(SO4)3).

[0079] Meanwhile, a composite decontamination device (1) according to one embodiment of the present invention may further include an ozone supply unit (500) that supplies ozone (O3) to a chemical decontamination agent discharged from a decontamination unit (200).

[0080] FIG. 5 is a schematic diagram showing the structure of a composite decontamination device according to one embodiment of the present invention when it includes an ozone supply unit.

[0081] As illustrated in FIG. 5, a composite decontamination device (1) according to one embodiment of the present invention may be configured to include an ozone supply unit (500) in addition to at least one decontamination agent supply unit (100), a decontamination unit (200), a waste liquid treatment unit (300), and a control unit (400).

[0082] The ozone supply unit (500) is connected to one side of the decontamination tank (210) constituting the decontamination unit (200), and can perform the role of generating and supplying ozone to regenerate the chemical decontamination agent after the decontamination process is completed. That is, since ozone has the characteristic of having strong oxidizing power, it can perform the role of regenerating the oxidizing agent (cerium, as will be described later) reduced from the chemical decontamination agent during the decontamination process by oxidizing it again.

[0083] Although not shown, the ozone supply unit (500) may be configured to include an ozone generator that generates ozone, a tubular ozone injection unit for injecting ozone into the interior of the decontamination tank (210), and a tubular decontamination agent recovery unit for recovering the chemical decontamination agent that is regenerated by ozone after the decontamination process.

[0084] Hereinafter, with reference to FIGS. 6 to 14, a composite decontamination device (1) according to a preferred embodiment of the present invention and a composite decontamination process using the same will be described.

[0085] FIG. 6 is a diagram showing the structure of a composite decontamination device according to a preferred embodiment of the present invention, and FIG. 7 is a flowchart showing the process of a composite decontamination process using a composite decontamination device according to a preferred embodiment of the present invention.

[0086] As illustrated in FIG. 6, a composite decontamination device (1) according to a preferred embodiment of the present invention may be configured to include a decontamination agent supply unit (100), a decontamination unit (200), a waste liquid treatment unit (300), a control unit (400), and an ozone supply unit (500). The composite decontamination device (1) according to a preferred embodiment of the present invention can perform a decontamination process to effectively remove an oxide film formed on the surface of radioactive metal waste (M), particularly a sparingly soluble metal oxide composed of chromium, iron, and nickel.

[0087] The decontamination agent supply unit (100) may be configured to include a pure water supply unit (110) that supplies pure water (W), a chemical supply unit (120) that supplies a chemical decontamination agent prepared by mixing pure water, an inorganic acid, and an oxidizing agent, and a cerium supply unit (140) that supplies cerium constituting the oxidizing agent. Preferably, the decontamination agent supply unit (100) may supply a chemical decontamination agent comprising cerium (IV) sulfate (Ce(SO4)2) as an oxidizing agent and sulfuric acid (H2SO4) as an inorganic acid.

[0088] The decontamination unit (200) can perform a chemical decontamination process using a chemical decontamination agent injected from a chemical supply unit (120) while radioactive metal waste (M) is placed in a basket (220) contained in a receiving space (211) of a decontamination tank (210), and can perform a physical decontamination process using ultrasonic waves irradiated from an ultrasonic generating unit (250) placed on the side and bottom surfaces of the decontamination tank (210). As shown in FIG. 6, the decontamination unit (200) may include a decontamination unit circulation unit (260) that circulates the chemical decontamination agent by heating or cooling it to maintain a constant process temperature of the chemical decontamination agent.

[0089] The waste liquid treatment unit (300) can receive the decontamination waste liquid that has completed the decontamination process from the decontamination unit (200) and purify the decontamination waste liquid.

[0090] The ozone supply unit (500) can supply ozone (O3) to regenerate cerium, which constitutes the oxidizing agent of the chemical decontamination agent (decontamination waste liquid) supplied from the decontamination tank (210), after the chemical decontamination process by the chemical decontamination agent is completed. As shown in FIG. 6, the ozone supply unit (500) may be configured to include an ozone generation unit (510) that generates ozone and a cerium regeneration unit (520) that regenerates cerium by injecting ozone into the chemical decontamination agent recovered from the decontamination tank (210).

[0091] Figure 7 illustrates the process of a composite decontamination process using a composite decontamination device according to a preferred embodiment of the present invention shown in Figure 6.

[0092] As illustrated in FIG. 7, the pure water supply unit (110) constituting the decontamination agent supply unit (100) injects pure water (distilled water) into the chemical supply unit (120) and the decontamination tank (210) (S110), and the chemical supply unit (120) can produce a chemical decontamination agent in liquid form by mixing the pure water injected from the pure water supply unit (110), an inorganic acid (sulfuric acid) injected from the outside, and an oxidizing agent (cerium) injected from the cerium supply unit (140) (S120, S130).

[0093] The decontamination unit (200) performs a chemical decontamination process using a chemical decontamination agent injected into the interior of the decontamination tank (210) from the chemical supply unit (120) (S140), and can perform an ultrasonic decontamination process using ultrasonic waves irradiated from an ultrasonic generator (250) positioned on the side and bottom surfaces of the decontamination tank (210) (S150). In FIG. 7, the chemical decontamination process (S140) and the ultrasonic decontamination process (S150) constituting the composite decontamination process are shown as being performed sequentially, but they may be performed simultaneously as needed.

[0094] Afterward, the chemical decontamination agent (decontamination waste liquid) that has completed the chemical decontamination process in the decontamination tank (210) of the decontamination unit (200) may be supplied to the ozone supply unit (500) (S160), or supplied to the waste liquid treatment unit (300) together with the washing water used for transporting and washing (S180) the radioactive metal waste (M) that is the object to be decontaminated.

[0095] The ozone supply unit (500) can supply ozone (O3) to the chemical decontamination agent that has completed the chemical decontamination process by the ozone generation unit (510), and the cerium regeneration unit (520) can regenerate the cerium constituting the oxidizing agent of the chemical decontamination agent by the ozone (O3) and then supply it back to the decontamination tank (210) (S170).

[0096] The waste liquid treatment unit (300) can receive and purify the chemical decontamination agent (decontamination waste liquid) that has completed the chemical decontamination process in the decontamination tank (210) and the washing water used for transporting and washing radioactive metal waste (M) (S190).

[0097] Meanwhile, as described above, the decontamination unit (200) constituting the composite decontamination device (1) according to a preferred embodiment of the present invention can sequentially perform a chemical decontamination process using an oxidizing agent containing cerium and a chemical decontamination agent containing an inorganic acid and a physical decontamination process using ultrasound to remove chromium, iron, and nickel oxide films formed on the surface of radioactive metal waste (M).

[0098] Preferably, for carrying out the chemical decontamination process, cerium(IV) sulfate (Ce(SO4)2) may be used as the oxidizing agent, and sulfuric acid (H2SO4) may be used as the inorganic acid.

[0099] This chemical decontamination process removes chromium oxide and iron oxide formed on the surface of radioactive metal waste (M) from cerium (Ce 4+ The oxidation process that removes the remaining iron oxide and nickel oxide by ) and hydrogen ions (H + It may include an acid washing process that removes by ).

[0100] First, cerium (Ce 4+ The oxidation process by ) can be represented by the following [Reaction Scheme 1].

[0101] [Reaction Equation 1]

[0102] Cr2O3+ 6Ce 4+ + 5H2O = 2HCrO4 - + 6Ce 3+ + 8H +

[0103] FeO + Ce 4+ + 2H + = Fe 3+ + Ce 3+ + H2O

[0104] The oxidation process of [Reaction Scheme 1] above is a reaction led by cerium(IV) sulfate (Ce(SO4)2), a powerful oxidizing agent, which oxidizes the chromium oxide film (Cr2O3) and iron oxide film (iron(II) oxide) (FeO) formed on the surface of radioactive metal waste (M) into a water-soluble form (HCrO4). - It can be converted into etc.

[0105] At this time, tetravalent cerium (Ce 4+ ) gains electrons to trivalent cerium (Ce 3+ It is reduced to ), and the reduced trivalent cerium (Ce 3+ ) is subsequently converted back into tetravalent cerium (Ce) by ozone (O3) supplied by the ozone supply unit (500). 4+ It can be recycled and recycled and reused. As such, since the cerium used in the oxidation process of [Reaction Equation 1] can be recycled by ozone and reused, it has the advantage of reducing the generation of secondary waste.

[0106] In addition, hydrogen ions (H + The acid washing process by ) can be represented by the following [Reaction Scheme 2].

[0107] [Reaction Equation 2]

[0108] Fe3O4+ 8H + = Fe 2+ + 2Fe 3++ 4H2O

[0109] NiFe2O4+ 8H + = Ni 2+ + 2Fe 3+ + 4H2O

[0110] Fe2O3+ 6H + = Fe 3+ + 3H2O

[0111] FeCr2O4+ 8H + = Fe 2+ + 2Cr 3+ + 4H2O

[0112] Cr2O3+ 6H + = 2Cr 3+ + 3H2O

[0113] FeO + 2H + = Fe 2+ + H2O

[0114] NiO + 2H + = Ni 2+ + H2O

[0115] The acid washing process of the above [Reaction Equation 2] involves hydrogen ions (H₂SO₄) dissociated from sulfuric acid (H₂SO₄), an inorganic acid. + In a reaction led by ), after the chromium oxide and iron oxide films are removed or loosened by the oxidation reaction of [Reaction Equation 1], hydrogen ions (H + ) combines with oxygen in the iron oxide and nickel oxide remaining on the surface of the radioactive metal waste (M) to form water (H2O), thereby forming iron and nickel metal ions (Fe 2+ , Fe 3+ , Ni 2+ ) can be eluted into an aqueous solution.

[0116] Meanwhile, the ultrasonic generator (250) for performing the physical decontamination process can easily separate the remaining oxide film loosened by the chemical decontamination process of [Reaction Equation 1] and [Reaction Equation 2] by means of ultrasound. Preferably, the ultrasonic generator (250) can irradiate the radioactive metal waste (M) with ultrasound of 40 kHz.

[0117] The present invention may be better understood by the following examples, which are for illustrative purposes only and are not intended to limit the scope of protection defined by the appended claims.

[0118] [Example 1]

[0119] Step 1 (Dissolution by inorganic acid): Sulfuric acid (H2SO4) was dissolved in distilled water (pure water) at varying concentrations in the range of 0.1 to 0.3 M.

[0120] Step 2 (Dissolution by oxidizing agent): The solution produced in Step 1 was prepared by dissolving cerium sulfate (Ce(SO4)2) as an oxidizing agent in a concentration ranging from 0.01 to 0.1 M.

[0121] Step 3 (Heating of chemical decontamination agent): The solution produced in Step 2 was heated to 60°C.

[0122] Step 4 (Chemical Decontamination Process): A chemical decontamination process was performed on a SUS 304 simulated oxide film specimen, which is radioactive metal waste (M), by varying the concentrations of sulfuric acid (H2SO4) and cerium sulfate (Ce(SO4)2) constituting the chemical decontamination agent.

[0123] Step 5 (Ultrasonic decontamination process): After the chemical decontamination process of Step 4, an ultrasonic decontamination process, which is a physical decontamination process, was performed by irradiating with 40 kHz ultrasound.

[0124] Step 6 (Regeneration): Ozone (O3) is injected into the decontamination tank (210) after the chemical decontamination process of Step 4 and the ultrasonic decontamination process of Step 5 are completed to cerium (Ce 4+ ) was regenerated. The process of regenerating cerium by ozone (O3) can be represented by the following [Reaction Equation 3].

[0125] [Reaction Equation 3]

[0126] O3(g) + 2Ce 3+ + 2H + = O2(g) + 2Ce 4+ + H2O

[0127] [Comparative Example 1]

[0128] Step 1 (Dissolution by inorganic acid): Sulfuric acid (H2SO4) was dissolved in distilled water (pure water) at varying concentrations in the range of 0.1 to 0.3 M.

[0129] Step 2 (Dissolution by oxidizing agent): The solution produced in Step 1 was prepared by dissolving cerium sulfate (Ce(SO4)2) as an oxidizing agent in a concentration ranging from 0.01 to 0.1 M.

[0130] Step 3 (Heating of chemical decontamination agent): The solution produced in Step 2 was heated to 60°C.

[0131] Step 4 (Chemical Decontamination Process): A chemical decontamination process was performed on a simulated oxide film specimen of SUS 304, which is radioactive metal waste (M), by varying the concentrations of sulfuric acid (H2SO4) and cerium sulfate (Ce(SO4)2) constituting the chemical decontamination agent.

[0132] [Comparative Example 2]

[0133] Step 1 (Dissolution by inorganic acid): Sulfuric acid (H2SO4) was dissolved in distilled water (pure water) at varying concentrations in the range of 0.1 to 0.3 M.

[0134] Step 2 (Dissolution by oxidizing agent): The solution produced in Step 1 was prepared by dissolving cerium sulfate (Ce(SO4)2) as an oxidizing agent in a concentration ranging from 0.01 to 0.1 M.

[0135] Step 3 (Heating of chemical decontamination agent): The solution produced in Step 2 was maintained at room temperature (25 ℃).

[0136] Step 4 (Chemical Decontamination Process): A chemical decontamination process was performed on a simulated oxide film specimen of SUS 304, which is radioactive metal waste (M), by varying the concentrations of sulfuric acid (H2SO4) and cerium sulfate (Ce(SO4)2) constituting the chemical decontamination agent.

[0137] Step 5 (Ultrasonic decontamination process): After the chemical decontamination process of Step 4, an ultrasonic decontamination process, which is a physical decontamination process, was performed by irradiating with 40 kHz ultrasound.

[0138] [Experimental Example 1]

[0139] To evaluate the performance of a composite decontamination process composed of a chemical decontamination process and an ultrasonic decontamination process of a composite decontamination device (1) according to a preferred embodiment of the present invention, the decontamination performance was compared with and without the ultrasonic decontamination process.

[0140] First, a chemical decontamination process was performed for 3 hours using a chemical decontamination agent prepared with 0.3 M concentration sulfuric acid (H2SO4) and 0.1 M concentration cerium sulfate (Ce(SO4)2) according to [Example 1], and an ultrasonic decontamination process was performed for 5 minutes by irradiating with 40 kHz ultrasound, and then the surface changes of the SUS 304 mock oxide film specimen were compared before and after the combined decontamination process.

[0141] In addition, a chemical decontamination process was performed for 6 hours using a chemical decontamination agent prepared with 0.3 M concentration sulfuric acid (H2SO4) and 0.1 M concentration cerium sulfate (Ce(SO4)2) according to [Comparative Example 1], and the surface changes of a simulated oxide film specimen of SUS 304 before and after the chemical decontamination process were compared.

[0142] The results of surface changes of a SUS 304 mock oxide film specimen in the composite decontamination process according to [Example 1] and the chemical decontamination process according to [Comparative Example 1] are shown in Fig. 8.

[0143] Figure 8(a) shows the results of surface changes of a SUS 304 mock oxide film specimen in a chemical decontamination process according to [Comparative Example 1], and Figure 8(b) shows the results of surface changes of a SUS 304 mock oxide film specimen in a composite decontamination process according to [Example 1].

[0144] First, as shown in Fig. 8(a), when the decontamination process is performed only by a chemical decontamination process using an oxidizing agent (cerium) and an inorganic acid (sulfuric acid) on a SUS 304 mock oxide film specimen according to [Comparative Example 1], it can be seen that the removal of the oxide film proceeds slowly over time.

[0145] On the other hand, as shown in Fig. 8(b), when a chemical decontamination process using an oxidizing agent (cerium) and an inorganic acid (sulfuric acid) and an ultrasonic decontamination process (combined decontamination process) were sequentially performed on a SUS 304 mock oxide film specimen according to [Example 1], it can be seen that the oxide film was removed much more cleanly in a time shortened by approximately 2 times compared to [Comparison 1].

[0146] In conclusion, when using chemical decontamination agents containing sulfuric acid (H2SO4) and cerium sulfate (Ce(SO4)2) at the same concentration, it can be confirmed that the performance of a combined decontamination process, which performs both chemical and ultrasonic decontamination processes, is significantly superior to that of a chemical decontamination process alone.

[0147] [Experimental Example 2]

[0148] In order to produce a composite decontamination device (1) according to a preferred embodiment of the present invention as a commercially viable technology, and to derive the optimal composition ratio of a chemical decontamination agent that satisfies both economic efficiency and decontamination efficiency, the decontamination performance was compared when the concentrations of cerium sulfate (Ce(SO4)2) and sulfuric acid (H2SO4) were varied.

[0149] First, a chemical decontamination process was performed at room temperature using a chemical decontamination agent prepared by varying the concentration of cerium sulfate (Ce(SO4)2) in sulfuric acid (H2SO4) at a concentration of 0.3 M in accordance with [Example 1], and an ultrasonic decontamination process was performed for 5 minutes by irradiating with 40 kHz ultrasound. Then, the weight change (removed weight) of a simulated oxide film specimen of SUS 304 before and after a combined decontamination process that took 3 hours was compared, and the results are shown in [Figure 9] and [Table 1].

[0150] Decontamination time (h) Cerium concentration (M) Sulfuric acid concentration (M) Removal weight (g) 3 0.1 0.3 0.0487 3 0.05 0.3 0.0453 3 0.02 0.3 0.0421 3 0.015 0.3 0.0386 3 0.01 0.3 0.0369

[0151] As shown in [Fig. 9] and [Table 1], experiments were conducted by mixing cerium sulfate (Ce(SO4)2) at concentrations of 0.1 M, 0.05 M, 0.02 M, 0.015 M, and 0.01 M, respectively, with sulfuric acid (H2SO4) at a concentration of 0.3 M. The results showed that as the concentration of cerium sulfate (Ce(SO4)2) decreased, the residual contamination of the SUS 304 mock oxide film specimen after the decontamination process tended to increase slightly; however, even at a concentration of 0.015 M, a sufficient visual decontamination effect and weight loss (0.0386 g) were observed, so it was determined to be the optimal concentration for commercialization. Subsequently, a chemical decontamination process was performed using a chemical decontamination agent prepared according to [Example 1] by varying the concentration of sulfuric acid (H2SO4) in the range of 0.1 to 0.3 M with cerium sulfate (Ce(SO4)2) at a concentration of 0.015 M. After performing an ultrasonic decontamination process for 5 minutes by irradiating with 40 kHz ultrasound, the weight change (removed weight) of the SUS 304 mock oxide film specimen before and after a combined decontamination process that took 3 hours was compared, and the results are as shown in [Fig. 10] and [Table 2].

[0152] Decontamination time (h) Cerium concentration (M) Sulfuric acid concentration (M) Removal weight (g) 3 0.015 0.3 0.0438 3 0.015 0.2 0.0442 3 0.015 0.15 0.0391 3 0.015 0.1 0.0092

[0153] As shown in [Figure 10] and [Table 2], experiments were conducted by mixing sulfuric acid (H2SO4) at concentrations of 0.3 M, 0.2 M, 0.15 M, and 0.1 M with cerium sulfate (Ce(SO4)2) at a concentration of 0.015 M. As a result, the weight loss was 0.0442 g when the concentration of sulfuric acid (H2SO4) was 0.2 M, which was the best, and thus it was determined to be the optimal concentration for usability. In conclusion, although decontamination performance was superior as the concentrations of sulfuric acid (H2SO4) and cerium sulfate (Ce(SO4)2) increased, when considering both economic efficiency, such as wastewater treatment costs, and decontamination efficiency, it was confirmed that the combination of sulfuric acid (H2SO4) at a concentration of 0.2 M and cerium sulfate (Ce(SO4)2) at a concentration of 0.015 M was the most efficient optimal composition ratio when tested at room temperature.

[0154] [Experimental Example 3]

[0155] In order to produce a composite decontamination device (1) according to a preferred embodiment of the present invention as a commercially viable technology, the decontamination performance was compared according to temperature conditions that can increase the reaction activity of cerium sulfate (Ce(SO4)2) and sulfuric acid (H2SO4).

[0156] First, according to [Example 1], a chemical decontamination process was performed by heating a chemical decontamination agent prepared with cerium sulfate (Ce(SO4)2) at concentrations of 0.01 M and 0.015 M, respectively, to 60 ℃ in sulfuric acid (H2SO4) at a concentration of 0.2 M, and an ultrasonic decontamination process was performed by irradiating with ultrasound at 40 kHz, and then the weight change (removed weight) of a simulated oxide film specimen of SUS 304 before and after the combined decontamination process was compared.

[0157] In addition, according to [Comparative Example 2], a chemical decontamination process was performed by maintaining a room temperature of 25°C with a chemical decontamination agent prepared with 0.01°M and 0.015°M concentrations of cerium sulfate (Ce(SO4)2) in 0.2°M concentration sulfuric acid (H2SO4), respectively, and an ultrasonic decontamination process was performed by irradiating with 40 kHz ultrasound, and then the weight change (removed weight) of a simulated oxide film specimen of SUS 304 before and after the combined decontamination process was compared.

[0158] The weight change (removed weight) of a simulated SUS 304 oxide film specimen was compared for the composite decontamination process at 60 ℃ according to [Example 1] and the chemical decontamination process at 25 ℃ according to [Comparative Example 2], and the results are as shown in [Fig. 11] and [Table 3].

[0159] Decontamination time (h) Cerium concentration (M) Sulfuric acid concentration (M) Temperature (C) Removal weight (g) 4 0.015 0.2 25 0.0344 4 0.01 0.2 25 0.0351 2 0.015 0.2 60 0.0358 2 0.01 0.2 60 0.0333

[0160] As shown in [Fig. 11] and [Table 3], at room temperature (25 ℃), the chemical decontamination agent containing cerium sulfate (Ce(SO4)2) at a concentration of 0.015 M and the chemical decontamination agent containing cerium sulfate (Ce(SO4)2) at a concentration of 0.01 M resulted in a weight change (removed weight) of 0.0344 g and 0.0351 g, respectively, of the SUS 304 mock oxide film specimen after a 4-hour chemical decontamination process. However, at a high temperature of 60 ℃, the chemical decontamination agent with the same concentration resulted in a weight change (removed weight) of 0.0358 g and 0.0333 g, respectively, after only a 2-hour chemical decontamination process. Furthermore, at room temperature (25 ℃), the SUS 304 of the chemical decontamination agent containing cerium sulfate (Ce(SO4)2) at a concentration of 0.015 M It can be seen that the weight change (removal weight) of the mock oxide film specimen is 0.0344 g, but at high temperature (60 ℃), the weight change (removal weight) of the SUS 304 mock oxide film specimen with a chemical decontamination agent containing cerium sulfate (Ce(SO4)2) at a concentration of 0.01 M is 0.0358 g.

[0161] In conclusion, it can be confirmed that chemical decontamination agents of the same concentration can have their reaction activity increased when heated to a high temperature (60 ℃) rather than room temperature (25 ℃), thereby shortening the decontamination process time to achieve the same decontamination performance by approximately 1.5 to 2 times. Furthermore, it can be confirmed that when heated to a high temperature (60 ℃), chemical decontamination agents can maintain better decontamination performance compared to room temperature (25 ℃) conditions even if the concentration of cerium sulfate (Ce(SO4)2) is slightly lowered (from 0.015 M to 0.01 M in the example in Table 3). Therefore, it can be confirmed that the combination of sulfuric acid (H2SO4) at a concentration of 0.2 M and cerium sulfate (Ce(SO4)2) at a concentration of 0.01 M is the most efficient optimal composition ratio when tested at a high temperature (60 ℃).

[0162] [Experimental Example 4]

[0163] In order to verify the degree of reduction of secondary waste generated after the composite decontamination process when the composite decontamination device (1) according to a preferred embodiment of the present invention is manufactured using commercially available technology, cerium (Ce) by ozone (O3) injection 4+ The regeneration of ) and the resulting availability of the decontamination agent (maintenance of decontamination performance) were evaluated.

[0164] First, a chemical decontamination process was performed using a chemical decontamination agent prepared with 0.3 M concentration sulfuric acid (H2SO4) and 0.01 M concentration cerium sulfate (Ce(SO4)2) according to [Example 1], and an ultrasonic decontamination process was performed by irradiating with 40 kHz ultrasound. Then, the weight change (removed weight) of a simulated SUS 304 oxide film specimen before and after the combined decontamination process, which took 2 hours, was compared, and the results are shown in [Fig. 12] and [Table 4].

[0165] Number of decontamination attempts Decontamination time (h) Cerium concentration Removal weight (g) 1 time 2 0.01M 0.0349 2nd time 2 0.01M 0.0361 3 times 2 0.01M 0.0333 4th time 2 0.01M 0.0226

[0166] In addition, cerium (Ce) regenerated by ozone (O3) after the complex decontamination process according to [Example 1] 4+After performing a chemical decontamination process using a chemical decontamination agent containing ) and an ultrasonic decontamination process by irradiating with 40 kHz ultrasound, the weight change (removed weight) of the SUS 304 mock oxide film specimen before and after the combined decontamination process, which took 2 hours, was compared, and the results are as shown in [Fig. 13], [Fig. 14] and [Table 5].

[0167] Decontamination recovery Decontamination time (h) Cerium concentration Removal weight (g) 1 time 2 0.01M 0.0393 2nd time 2 0.01M 0.0368 3 times 2 0.01M 0.0335 4th time 2 0.01M 0.0189

[0168] First, as shown in [Fig. 12], [Fig. 13], and [Table 4], when a chemical decontamination process is continuously performed for 2 hours using a chemical decontamination agent prepared with 0.3 M sulfuric acid (H2SO4) and 0.01 M cerium sulfate (Ce(SO4)2), it can be seen that the decontamination performance of the chemical decontamination agent gradually decreases, and in the 4th decontamination process stage, the decontamination performance is reduced by approximately 40% compared to the initial 1st decontamination process stage. Additionally, as shown in [Fig. 13], ozone (O3) is supplied to the chemical decontamination agent after the 4th decontamination process, and cerium (Ce 4+ If the regeneration process of ) is performed, cerium (Ce ) after approximately 4 hours 4+ It can be confirmed that the concentration of ) recovers to nearly 100%.

[0169] Finally, as shown in [Fig. 14] and [Table 5], when a chemical decontamination process of 2 hours is continuously performed using a chemical decontamination agent after cerium regeneration, it can be confirmed that the decontamination performance is similar to that of the chemical decontamination agent before regeneration.

[0170] In conclusion, when using a chemical decontamination agent containing sulfuric acid (H2SO4) and cerium sulfate (Ce(SO4)2), cerium (Ce) is removed by the injection of ozone (O3). 4+ It can be confirmed that the amount of secondary waste generated can be reduced because it can be regenerated and reused without deterioration of decontamination performance.

[0171] In this way, the composite decontamination device (1) according to one embodiment of the present invention uses an inorganic acid-based chemical decontamination method to perform a decontamination process for removing an oxide film formed on the surface of radioactive metal waste (M), thereby increasing the oxide film removal rate while minimizing corrosion of the radioactive metal waste (M) compared to the existing organic acid-based chemical decontamination method, and can not only improve decontamination performance but also reduce the amount of secondary radioactive waste generated after the decontamination process.

[0172] In addition, a composite decontamination device (1) according to one embodiment of the present invention is provided with a plurality of decontamination agent supply units (100) in which a plurality of chemical decontamination agents are stored, and is configured to supply a chemical decontamination agent by selecting one of the plurality of decontamination agent supply units according to the radioactive metal waste (M) to be decontaminated, thereby enabling a decontamination process to be performed universally for radioactive metal waste (M) having various types, shapes, sizes, etc., so that the decontamination process time and cost can be reduced and the efficiency of the decontamination process can be maximized.

[0173] In addition, the composite decontamination device (1) according to one embodiment of the present invention can significantly reduce the decontamination process time for radioactive metal waste (M) contaminated with adhesion and radioactive metal waste (M) of complex shape by combining an inorganic acid-based chemical decontamination method with an ultrasonic decontamination method, thereby improving the efficiency of the decontamination process.

[0174] Meanwhile, the composite decontamination device (1) according to a preferred embodiment of the present invention performs a composite decontamination process consisting of a chemical decontamination process using a chemical decontamination agent including an oxidizing agent and an inorganic acid and an ultrasonic decontamination process using ultrasound, and by regenerating the oxidizing agent constituting the chemical decontamination agent after the chemical decontamination process by ozone, it is possible to significantly improve the decontamination performance for radioactive metal waste and minimize the generation of secondary waste.

[0175] In addition, the composite decontamination device (1) according to a preferred embodiment of the present invention is manufactured by mixing a chemical decontamination agent with an oxidizing agent, cerium (IV) sulfate (Ce(SO4)2) at a concentration of 0.015 M, and an inorganic acid, sulfuric acid (H2SO4) at a concentration of 0.2 M, and then performing a chemical decontamination process by heating to 60 ℃ and performing an ultrasonic decontamination process by irradiating with ultrasound at 40 kHz, thereby producing a composite decontamination device (1) that has commercially viable technology for actual use and can perform a decontamination process that satisfies decontamination performance, decontamination efficiency, and economic feasibility.

[0176] Meanwhile, the present specification and drawings disclose preferred embodiments of the present invention. Although specific terms have been used, they are used merely in a general sense to facilitate the explanation of the technical content of the present invention and to aid in understanding the invention, and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art that, in addition to the embodiments disclosed herein, other variations based on the technical concept of the present invention are possible. Explanation of the symbols

[0177] <Explanation of symbols for major parts of the drawing> 1: Complex decontamination device M: Radioactive metal waste 100: Decontamination agent supply unit 110: Pure water supply unit 120: Chemical supply unit 130: Switching valve 140: Cerium supply unit 200: Decontamination Unit 210: Decontamination Tank 211: Containment space 212: Decontamination agent inlet 213: Waste liquid discharge section 220: Basket 230: Basket drive unit 240: Opening / closing cover 250: Ultrasonic generator 260: Decontamination water circulation unit 300: Waste liquid treatment unit 400: Control unit 500: Ozone supply unit 510: Ozone generator unit 520: Cerium Regeneration Unit

Claims

Claim 1 A composite decontamination device for removing an oxide film formed on the surface of radioactive metal waste generated in a nuclear power plant, comprising: at least one decontamination agent supply unit that mixes pure water and a plurality of chemical agents to produce a chemical decontamination agent in liquid form; a decontamination tank in which radioactive metal waste is contained and into which the chemical decontamination agent supplied from any one of the at least one decontamination agent supply units is introduced; a decontamination unit that includes at least one ultrasonic generator provided inside the decontamination tank and generates ultrasonic waves toward the radioactive metal waste, and performs a decontamination process for removing an oxide film formed on the surface of the radioactive metal waste; and a waste liquid treatment unit that receives the decontamination waste liquid from the decontamination unit after the decontamination process is completed and purifies the decontamination waste liquid. A composite decontamination device comprising a control unit connected to at least one decontamination agent supply unit, the decontamination unit, and the waste liquid treatment unit, and controlling the operation of the at least one decontamination agent supply unit, the decontamination unit, and the waste liquid treatment unit, wherein the chemical decontamination agent is an inorganic acid-based chemical decontamination agent, and the decontamination unit performs an ultrasonic decontamination process using ultrasound generated from at least one ultrasonic generator while a chemical decontamination process using the inorganic acid-based chemical decontamination agent is performed to remove an oxide film formed on the surface of the radioactive metal waste. Claim 2 A composite decontamination device according to claim 1, characterized in that the inorganic acid is one or more inorganic acids selected from the group consisting of hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), phosphoric acid (H3PO4), hydrogen bromide (HBr), hydrogen fluoride (HF), and hydrogen iodide (HI). Claim 3 A composite decontamination device according to claim 1, characterized in that the chemical decontamination agent further comprises cerium. Claim 4 A composite decontamination device according to claim 1, wherein the decontamination agent supply unit is provided with a plurality of units, and the control unit selects a first decontamination agent supply unit, which is one of the plurality of decontamination agent supply units, according to radioactive metal waste contained inside the decontamination unit, and then supplies the chemical decontamination agent from the first decontamination agent supply unit to the decontamination unit. Claim 5 A composite decontamination device according to claim 1, wherein the decontamination tank has an open top and a receiving space formed inside for placing the radioactive metal waste, and is provided on one side with a decontamination agent inlet for introducing the chemical decontamination agent and a waste liquid discharge outlet for discharging the decontamination waste liquid, and the decontamination unit further comprises: a basket rotatably coupled to the open top or inside of the decontamination tank and containing the radioactive metal waste; a basket driving unit provided on one side of the decontamination tank and generating a driving force to drive the basket; and an opening / closing cover for opening and closing the open top of the decontamination tank. Claim 6 delete Claim 7 A composite decontamination device according to claim 1, characterized in that the composite decontamination device further includes an ozone supply unit that supplies ozone to the chemical decontamination agent discharged from the decontamination unit after the decontamination process is completed. Claim 8 A composite decontamination device for removing an oxide film formed on the surface of radioactive metal waste generated in a nuclear power plant, comprising: a decontamination agent supply unit that mixes pure water, an oxidizing agent, and an inorganic acid to produce a chemical decontamination agent in liquid form; a decontamination unit that receives radioactive metal waste inside and performs an ultrasonic decontamination process using ultrasound generated from an ultrasonic generator while a chemical decontamination process using the chemical decontamination agent supplied from the decontamination agent supply unit is performed to remove the oxide film formed on the surface of the radioactive metal waste; an ozone supply unit that receives the chemical decontamination agent that has completed the decontamination process from the decontamination unit and supplies ozone to reduce and regenerate the oxidizing agent; and a waste liquid treatment unit that receives the decontamination waste liquid that has completed the decontamination process from the decontamination unit and purifies the decontamination waste liquid, wherein the oxidizing agent uses cerium(IV) sulfate (Ce(SO4)2) and the inorganic acid uses sulfuric acid (H2SO4). Claim 9 delete Claim 10 A combined decontamination device according to claim 8, characterized in that the cerium (IV) sulfate (Ce(SO4)2) is used at a concentration of 0.01 M and the sulfuric acid (H2SO4) is used at a concentration of 0.2 M. Claim 11 A composite decontamination device according to claim 8, characterized in that the chemical decontamination agent is heated to 60°C for use. Claim 12 A composite decontamination device according to claim 8, characterized in that the ultrasonic generating unit generates ultrasonic waves of 40 kHz and irradiates the radioactive metal waste.

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