KR102006015B1 - Method for system decontamination - Google Patents

Abstract

The present invention provides a safe system decontamination method capable of minimizing radiation exposure of a worker. According to an embodiment of the present invention, the system decontamination method, which is the decontamination method of a system in which a solution moves, comprises the steps of: injecting oxidants into a system; injecting a reducing agent of a first concentration into the system; injecting the reducing agent of a second concentration into the system; removing a particle metal material of a solution; decomposing an organic acid of the solution; and removing the organic acid and metal ions remaining in the solution after the step of decomposing the organic acid.

Description

{METHOD FOR SYSTEM DECONTAMINATION}

The present invention relates to a systematic decontamination method, and more particularly, to a systematic decontamination method for chemical decontamination of a primary system at the time of nuclear dismantling.

Nuclear power plants artificially control the sequential fission reaction of fissile materials in the reactor to generate heat, produce radioactive isotopes and plutonium, or form radiation fields.

It consists of nuclear power plant reactors with many individual functions, such as reactor coolant systems (reactor pressure vessel, steam generator, pressurizer, main piping, etc.), chemical and volumetric control systems, and residual heat removal systems.

There is a radioactive material in this system, and the worker can be exposed to radiation.

Therefore, in order to reduce the radiation exposure of the dismantling worker due to the radioactive material immediately after the permanent suspension of the nuclear power plant, and to ensure the ease of dismantling and dismantling of the power plant, chemical system decontamination must be performed on the whole system contaminated with radioactivity .

Therefore, the present invention provides a safe systematic decontamination method capable of minimizing the exposures of the workers by decontaminating the entire system when the nuclear power plant is demolished.

A systematic decontamination method according to an embodiment of the present invention is a system for decontaminating a system in which a solution moves, comprising the steps of injecting an oxidizing agent into the system, injecting a reducing agent of a first concentration into the system, Removing the particulate metallic material of the solution, decomposing the organic acid of the solution, and removing organic acids and metal ions remaining in the solution after decomposing the organic acid.

After the step of removing the particulate metal material, the iron ion concentration of the solution may be 2 mM or less.

Further comprising the step of removing the metal ions of the solution after the step of removing the particulate metal material, and after the step of removing the metal ions, the iron ion concentration of the solution may be 2 mM or less.

In the step of removing metal ions of the solution, the solution may be passed through a cation exchange resin to remove metal ions.

Further comprising the step of measuring the concentration of the metal ion before the step of removing the particulate metal material.

If the measured chromium ion concentration in the step of measuring the concentration of the metal ion is 1 ppm or more, the step of removing residual organic acid and metal ion may be followed by the step of injecting an oxidizing agent into the system, a step of injecting a reducing agent of a first concentration into the system , Repeating the steps of injecting a second concentration of reducing agent into the system, removing the particulate metallic material of the solution, decomposing the organic acid of the solution, and removing the organic acid and metal ions,

If the measured chromium ion concentration in the solution measured in the step of measuring the concentration of the metal ion is less than 1 ppm, the step of removing the residual organic acid and the metal ion may include the steps of injecting a second concentration of reducing agent into the system, The steps of removing the material, decomposing the organic acid of the solution, and removing the organic acid and metal ions may be repeated.

Further comprising the step of measuring the surface dose rate of the piping of the system after the step of removing the organic acid and the metal ion to derive the DF value, and if the DF is not less than the reference value, the solution can be drained to the system or the outside.

The oxidizing agent may include a permanganic acid solution and a mineral acid solution.

The first concentration of reducing agent may be 100 ppm to 1,000 ppm oxalic acid, and the second concentration of reducing agent may be 1,000 ppm to 3,000 ppm oxalic acid.

The organic acid may be oxalic acid.

The step of decomposing the organic acid may be carried out until oxalic acid is 90% to 99%.

The step of decomposing the organic acid may further include a step of injecting a hydrogen peroxide solution.

In the step of injecting the reducing agent of the second concentration, the step of injecting the reducing agent of the first concentration may be performed and the process may be performed after 30 minutes to 1 hour.

The step of injecting the oxidizing agent may proceed for 3 to 24 hours, and the step of injecting the reducing agent of the second concentration may proceed for 4 to 72 hours.

In the step of removing the organic acid and the metal ion, the solution may be passed through a mixed phase ion exchange resin to remove the organic acid and the metal ion.

The step of decomposing the organic acid may proceed in a UV reactor.

According to an embodiment of the present invention, it is possible to chemically easily decontaminate the entire nuclear disintegration system to remove radioactive materials, thereby minimizing the radiation exposure of the operator during disassembly work.

1 is a block diagram of a systematic decontamination facility for nuclear disassembly according to an embodiment of the present invention.
2 is a flowchart for explaining a systematic decontamination method according to an embodiment of the present invention.
FIGS. 3 to 8 are views for explaining the flow of the solution according to the decontamination procedure of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

1 is a block diagram of a systematic decontamination facility for nuclear disassembly according to an embodiment of the present invention.

1, a systematic decontamination facility 1000 according to an embodiment of the present invention includes a filter unit 200, a cation exchange resin 300, a reactor 400 connected to a system 100 of a nuclear power plant, , A mixed phase ion exchange resin (500), a drug supply part (600), and a circulation piping part forming a circulation structure of a fluid (hereinafter referred to as a solution)

The system 100 can be a reactor coolant system (reactor pressure vessel, steam generator, pressurizer, main piping, etc.), a chemical and volume control system, a residual heat removal system, and can be made of metal including carbon steel or stainless steel. Thus, a metal oxide layer (chromium, iron, nickel, cobalt, etc.) may be formed on the inner surface of the system 100.

The circulation piping unit connects the filter unit 200, the cation exchange resin 300, the reactor 400, the mixed-phase ion exchange resin 500, and the chemical supply unit 600 to remove radioactive substances after chemical decontamination of the system 100 And provides a circulation structure through the decomposition of the organic acid and the removal of the metal ions of the solution containing it.

The circulation piping unit includes a first circulation pipe P1 connected between the outlet of the system 100 and the filter unit 200, a second circulation pipe connected between the filter unit 200 and the cation exchange resin 300 P2, a third circulation pipe P3 connected between the cation exchange resin 300 and the reactor 400, a fourth circulation pipe P4 connected between the reactor 400 and the mixed phase ion exchange resin 500, , And a fifth circulation pipe (P5) connected between the mixed phase ion exchange resin (500) and the inlet of the system (100).

The circulation piping unit branches from the fifth circulation pipe P5 and branches from the first branch pipe Y1 and the third circulation pipe P3 connected to the drug supply unit 600 and supplies hydrogen peroxide to the reactor 400 Is connected to a cleaning liquid tank 42 branched from the second branch pipe Y2, the third circulation pipe P3 and the fourth circulation pipe P4 connected to the hydrogen peroxide tank 41 for washing the reactor 400 The third branch piping Y3 may be provided.

The circulation piping unit may further include a bypass pipe bypassing the device connected to the circulation pipe. The bypass pipe is connected between the second circulation pipe (P2) and the third circulation pipe (P3) to connect the cation exchange resin (300) A second bypass pipe B2 connected between the fourth circulation pipe P4 and the fifth circulation pipe P5 to bypass the mixed phase ion exchange resin 500 and a second bypass pipe B2 bypassing the mixed phase ion exchange resin 500, And a third bypass pipe B3 connecting the circulation pipe P3 and the fourth circulation pipe P4 to bypass the reactor 400. [

The circulation piping unit may be provided with pumps PP1, PP2, PP3, and PP4 and valves VV for controlling the speed and flow rate of the solution moving inside.

The sample pipes SP1, SP2, SP3, SP4, and SP5 may be provided in the circulation piping unit, and the sample pipes SP1, SP2, SP3, SP4, and SP5 may be provided for directly extracting and analyzing the solution. The first to fifth circulation pipes P5 to P5, respectively, and valves may be installed in the sample pipe.

The filter unit 200 removes the remaining particulate metallic material without dissolving in the solution discharged from the system 100 and transferred through the first circulation pipe P1. The particulate metallic materials of Cr, Ni, Fe, Co, Mn, and Cs having a size of 10 탆 or more are removed from the filter unit 200, The solution is transferred to the second circulation pipe (P2). At this time, the filter unit 200 may be a cartridge filter made of a corrosion-resistant material, and may have an efficiency of removing 98% or more of particles of 10 m or more.

The solution transferred to the second circulation pipe (P2) is transferred to the cation exchange resin (300) or the first bypass pipe (B1) according to the iron ion concentration of the solution through the pump (PP1).

The solution transferred to the cation exchange resin 300 may contain metal ions such as chromium (Cr), nickel (Ni), iron (Fe), cobalt (Co), manganese (Mn), cesium The solution is transferred to the third circulation pipe P3 and the solution transferred to the first bypass pipe B1 bypasses the cation exchange resin 300 and is transferred to the third circulation pipe P3.

At this time, the iron ion concentration of the solution transferred to the third circulation pipe P3 is kept at a reference value, for example, 2 mM or less, because the iron ion can be used as a catalyst in the reactor 400 in the photolysis. However, when the iron ion concentration exceeds 2 mM, iron in the solution may be deposited, so that the iron ion concentration is preferably 2 mM or less.

The solution can be collected through the second sample tube (SP2) and the third sample tube (SP3) for the measurement of the iron ion concentration. At this time, when the iron ion concentration measured through the second sample pipe (SP2) is 2 mM or less, the solution does not pass through the cation exchange resin 300 but flows through the first bypass pipe (B1) and the third circulation pipe To the reactor (400). On the other hand, when the ferrous ion concentration measured through the second sample tube (SP2) exceeds 2 mM, the solution passes through the cation exchange resin (300) to maintain the iron ion concentration at 2 mM or less (Via the third circulation pipe SP3) and then to the reactor 400 through the third circulation pipe P3.

Reactor 400 is the number of UV reactors containing UV lamps. When the solution is supplied into the reactor 400 from the upper side or the upper side of the reactor 400, an empty space may be formed on the reactor 400 to lower the reaction efficiency. Therefore, as in the embodiment of the present invention, the third circulation pipe P3 may be connected to the lower or lower side of the reactor 400. [

The UV generated from the UV lamp in the reactor 400 photodecomes the organic acid in the solution, at which time carbon dioxide gas and water may be generated. Therefore, an exhaust pipe 43 for discharging carbon dioxide gas may be connected to the upper part of the reactor 400.

UV lamps in reactor 400 may include UVC lamps and UVB lamps of different wavelengths, and UVB lamps are high energy lamps compared to UVC. Therefore, it is possible to mix UVB and UVC according to the reaction temperature.

A UVC (short wave UV) lamp emits a wavelength of 180 nm to 280 nm, and a UVB (middle wave UV) lamp emits a wavelength of 280 nm to 500 nm.

A temperature controller (not shown) such as a heater or a cooling unit may be installed outside the reactor 400.

Meanwhile, the reactor 400 may be connected to a sensor unit 44 for monitoring the internal reaction state in real time.

The sensor unit 44 measures temperature, pH, pressure, and the like in the reactor 400 so that the inside of the reactor 400 can maintain an optimum reaction environment. For example, when oxalic acid is decomposed with an organic acid, the optimum reaction temperature ranges from 20 ° C to 50 ° C. Therefore, the internal temperature can be measured through the sensor unit 44 and the temperature can be maintained by adjusting the temperature control unit .

Depending on the oxalic acid concentration of the solution extracted through the fourth sample pipe SP4 installed in the fourth circulation pipe P4, the solution discharged from the reactor 400 is mixed with the mixed phase ion exchange resin 500 or the second bypass pipe B2 And then to the system 100 through the fifth circulation pipe P5.

The mixed phase ion exchange resin 500 may include a cation exchange resin and an anion exchange resin. The cation exchange resin removes metal ions remaining in the solution, and the anion exchange resin removes organic acids remaining in the solution.

The ratio of the cation exchange resin to the anion exchange resin may be mixed at a ratio of 5: 5, 6: 4, 7: 3, 8: 2 and may be changed according to the concentration of the organic acid passing through the mixed phase ion exchange resin.

The chemical supply unit 600 may include an oxidant tank 61 and a reducing agent tank 62. The oxidant tank 61 and the reducing agent tank 62 may be made of a chemical agent used as an oxidizing agent or a chemical agent used as a reducing agent, Tank. For example, the oxidizing agent may be an inorganic acid such as nitric acid, sulfuric acid, hydrochloric acid, and permanganic acid, and the reducing agent may be an organic acid such as oxalic acid, citric acid or citric acid and these may be stored in respective tanks and optionally supplied .

The systematic decontamination facility 1000 according to an embodiment of the present invention may further include a monitoring unit 800 positioned between the system 100 and the filter unit 200.

The monitoring unit 800 may include an electrical conductivity sensor, an ORP (Oxidation-Reduction Potential) sensor, a pH sensor, and a flow meter. The monitoring unit 800 may be connected to the system 100, Analyze the discharged solution.

The electrical conductivity sensor, the OPR sensor, and the pH sensor measure the conductivity, oxidation-reduction potential and hydrogen ion concentration index of the chemical decontamination agent, detect the electrochemical properties of the chemical decontamination agent, Process time and so on.

Hereinafter, a method for systematic decontamination using the systematic decontamination facility described above will be described in detail.

FIG. 2 is a flowchart for explaining a systematic decontamination method according to an embodiment of the present invention, and FIGS. 3 to 8 are views for explaining the flow of a solution according to the decontamination procedure of FIG. Reference numerals of the systematic decontamination facility to be described with reference to FIG. 2 refer to FIG.

As shown in FIG. 2, the systematic decontamination method according to an embodiment of the present invention includes an oxidant injection step (S100) for oxidation, a primary injection step (S102) for oxidizing decomposition and removal, a reducing agent A secondary injection step (S104) and a purifying step.

The oxidation process, oxidant decomposition process and reduction process according to the oxidant injection step (S100), the reducing agent first injection step (S102), the reducing agent secondary injection step (S104) .

In the oxidant injection step (S100), the oxidant of the oxidant tank (61) is injected into the system (100) through the pump (PP2). At this time, the valve (VV) for controlling the movement of the solution to the first circulation pipe (P1) is in a closed state, and a solution such as a coolant is present in the system (100).

The oxidant is for removing the chromium oxide layer formed on the inner surface of the system 100 and may be heated after being heated through a heater (not shown) connected to the first branch pipe Y1. At this time, the oxidant is heated to a reaction temperature of 80 ° C to 100 ° C, and then is delivered to the fifth circulation pipe P5 through the pump PP2 and then injected into the system 100 through the booster pump BP . Since the system 100 maintains a constant pressure, the medicine is injected at a higher pressure than the system 100 through the booster pump BP.

The oxidizing agent may be injected with 50 ppm to 300 ppm permanganic acid and 0 to 5 mM inorganic acid, such as at least one of nitric acid, sulfuric acid and hydrochloric acid. As the reaction of oxidant permanganic acid progresses, the concentration of the oxidant changes and thus the pH increases. Thus, inorganic acids can be injected together to maintain the pH between 1.5 and 2.5.

When the oxidizing agent is injected into the system 100, the oxidation process proceeds in the process of Reaction 1 below, and the oxidation process may proceed for 3 to 24 hours. When the oxidation process time is less than 3 hours, sufficient reaction does not occur. When the oxidation process time exceeds 24 hours, the reaction process is not performed any more and the decontamination is not performed.

[Reaction Scheme 1]

In step S102, the reducing agent in the reducing agent tank 62 is injected into the system 100 through the pump PP2. When the reducing agent is injected, the oxidizer decomposition process proceeds. The oxidizing agent decomposition process proceeds in the process of the following Reaction Scheme 2 to decompose the permanganic acid remaining in the solution. At this time, 100 to 1,000 ppm of oxalic acid may be added to the reducing agent.

[Reaction Scheme 2]

Thereafter, in the second step of injecting the reducing agent (S104), an organic acid having a different concentration is further added to the system from the reducing agent tank 62, and the reducing step proceeds. Depending on the concentration, it can be stored in a reducing agent tank which is firstly charged and in a different reducing agent tank.

At this time, 1,000 to 3,000 ppm of oxalic acid is further added, and the reduction process proceeds to the process of Reaction Scheme 3 below, and the second injection is performed after 30 minutes to 1 hour after the first injection of the reducing agent.

[Reaction Scheme 3]

The reduction process may be performed for 4 to 72 hours, and the concentration of the metal ion is measured every one hour through the sample pipe SP1 provided in the first circulation pipe P1 (S106). If the concentration of the measured metal ion no longer changes, the reduction process is terminated.

The oxidation process in the system, the oxidizer decomposition process, and the reduction process are completed, and the valve VV is opened to discharge the solution in the system 100 to the first circulation pipe P1 to proceed the purification process. The purification process includes a step of removing particulate metallic material (S108), a step of removing metal ions (112), a step of decomposing oxalic acid (114), a circulation step of circulation (S117), and a step of removing residual oxalic acid and metal ions (S118), and includes all reaction processes that proceed from the system 100 as well as the system 100 after the reduction process.

In the particulate metallic material removal step (S108), the solution discharged from the system 100 is transferred to the filter unit 200 through the first circulation pipe P1, and the particles remaining in the solution by the filter unit 200 The metallic material is removed (S108). The particulate metal material may be Cr, Ni, Fe, Co, Mn, or Cs.

Thereafter, a sample of the solution passed through the filter unit 200 is sampled to measure the concentration of the iron ion (S108), and it is determined whether the concentration of the iron ion satisfies the reference value (S110).

The reference value of the iron ion concentration of the solution supplied to the reactor 400 is 2 mM or less, and iron may be deposited if the solution is more than 2 mM.

When the concentration of iron ions is within the standard value, the solution is transferred to the reactor 400 through the second circulation pipe P2, the first bypass pipe B1 and the third circulation pipe P3 (see FIG. 4).

On the contrary, when the concentration of the iron ions is out of the reference value, the solution passing through the filter unit 200 is passed through the cation exchange resin 300 to remove the metal ions (S112) so that the concentration of the iron ions can be within the standard value. When the solution passes through the cation exchange resin 300 and the concentration of the iron ions satisfies the reference value, the solution is transferred to the reactor 400 through the third circulation pipe P3 (see FIG. 5).

The cation exchange resin 300 is used to remove metal ions (Cr, Ni, Fe, Co, Mn, and Cs) in the solution. An appropriate amount of the cation exchange resin 300 is installed according to the concentration of the measured iron ions The iron ion concentration can be controlled. At this time, oxalic acid which is an organic acid can be regenerated.

The solution may be injected into the reactor 400 from the lower or lower side of the reactor 400 through a third circulation line P3 connected to the lower or lower side of the reactor 400. [

Meanwhile, the solution moves according to the iron ion concentration, and other metal ions remaining in the solution can be removed through the mixed phase ion exchange resin described later.

Hydrogen peroxide in the hydrogen peroxide tank 41 is injected into the reactor 400 through the second branch pipe Y2 and the third circulation pipe P3 together with the solution in the oxalic acid decomposition step S114, ) At a flow rate and a rate of 1: 1 with oxalic acid.

The oxalic acid decomposition proceeds to the process of the following [Reaction Scheme 4] due to the UV generated from the UV lamp installed in the reactor 400.

[Reaction Scheme 4]

The oxalic acid decomposition step (S114) proceeds through the sensor unit (44) while advancing while circulating (S117) inside the reactor (400) and the system (100), and carbon dioxide is generated by the above reaction scheme (4). The generated carbon dioxide can be discharged to the outside through the exhaust pipe 43 connected to the upper part of the reactor 400.

On the other hand, when oxalic acid is decomposed, the optimum reaction temperature ranges from 20 ° C to 50 ° C. Therefore, the internal temperature of the reactor 400 is measured through the sensor unit 44 and the temperature is maintained by adjusting the heater or the cooler.

The solution in the reactor 400 is sampled every hour through the sample tube SP4 to determine whether the resolution of oxalic acid satisfies a predetermined reference value (S116). At this time, the resolution standard value of oxalic acid can be predetermined to a specific value within the range of 90% to 99%.

The solution in the reactor 400 flows through the fourth circulation pipe P4, the second bypass pipe B2, the fifth circulation pipe P5, the system 100, the first circulation pipe P1 6) for repeatedly circulating the filter unit 200, the second circulation pipe P2, the first bypass pipe B1, the third circulation pipe P3, and the reactor 400 (see FIG. 6) ). The systematic cycle S117 can be repeated until the resolution of oxalic acid meets a criterion.

When the decomposition ability of oxalic acid is equal to or higher than the reference value, the step of removing residual oxalic acid and metal ions (S118) is performed.

The step of removing residual oxalic acid and metal ions S118 proceeds in the mixed phase ion exchange resin 500 and is transferred to the mixed phase ion exchange resin 500 through the fourth circulation pipe P4 and then to the fifth circulation pipe P5) (see Fig. 7). At this time, the valve of the second bypass pipe B2 is closed.

The mixed phase ion exchange resin 500 includes a cation exchange resin and an anion exchange resin for removing metal ions and oxalic acid remaining in the solution conveyed in the reactor 400. At this time, the ratio of the cation exchange resin and the anion exchange resin may be different depending on the concentration of the remaining oxalic acid. For example, the ratio of the cation exchange resin to the anion exchange resin may be 5: 5, 6: 4, 7: 3, 8: 2.

Thereafter, a decontamination factor (DF) is derived using a result obtained by measuring the surface dose rate of the piping or the like in the system 100, and it is determined whether the predetermined value of the DF is satisfied (S120). DF is a value derived by using a surface dose rate measurement value of a piping or the like, and a reference value of DF can be predetermined to a specific value in a range of 20 to 40. At this time, the surface dose rate can be measured by using a mobile / fixed type radiation measuring instrument, and the surface dose rate of the piping and the like in the system 100 can be measured.

If the DF is equal to or greater than a predetermined reference value, the solution is the safe solution after the decontamination process according to an embodiment of the present invention, so it drains to the system 100 or to the outside (S121). The solution can be sampled through a pre-drainage sample tube (SP5) and further analyzed for metal ions and organic acids.

Conversely, when the DF is less than the predetermined reference value, the solution is transferred to the system 100 through the fifth circulation pipe P5, and the decontamination process is repeated from the oxidant injection step S100 or the reducing agent secondary injection step S104 You can proceed.

The oxidizing step of the oxidant injecting step S100 is for removing chromium in the system 100. When the chromium concentration deviates from the reference value, the oxidizing agent injecting step S100 proceeds from the oxidizing agent injecting step S100. When the chromium concentration satisfies the reference value, Since the step is not required, the decontamination step can be started from the step of injecting the reducing agent (S104).

At this time, the concentration of the chromium ion can be determined from the concentration measured in the metal ion concentration measuring step (S106), and the reference value of the chromium ion concentration can be 0 or more and less than 1 ppm. On the other hand, as the process time in the reactor 400 increases, the metal ions in the solution are deposited on the surface of the UV lamp, and the efficiency of the reactor 400 deteriorates due to the deposited metal layer. Thus, the process of washing the reactor 400 (see FIG. 8) proceeds.

The washing of the reactor 400 can proceed as the reaction process proceeds in the system 100 or when the solution remains in the system 100. For example, when the solution remains in the system 100 during the oxidant injection step (S100), the reducing agent primary injection step (S102), the reducing agent secondary injection step (S104), or the system circulation (S117) .

In the washing step of the reactor 400, the washing liquid in the washing liquid tank 42 is injected into the reactor 400 through the pump PP4 to react with the metal on the surface of the lamp so that the metal can be eluted. The washing solution may be an inorganic or organic acid containing at least one of phosphoric acid, nitric acid, oxalic acid and citric acid.

After the valves of the third circulation pipe P3 and the fourth circulation pipe P4 connected to the reactor 400 are closed and the washing solution is injected into the reactor 400 through the third branch pipe Y3, So that the metal on the lamp surface can be removed while being circulated to the tank 43.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Of course.

41: hydrogen peroxide tank 42: cleaning liquid tank
43: exhaust pipe 100: system
200: Filter part 300: Cation exchange resin
400: UV reactor 500: mixed phase ion exchange resin
600: drug supply unit 800: monitoring unit

Claims (16)

In a decontamination method of a system in which a solution moves,
Injecting an oxidant into the system,
Injecting a first concentration of reducing agent into the system,
Injecting a second concentration of reducing agent into the system,
Measuring the concentration of the metal ion in the solution,
Measuring the concentration of the metal ion in the solution, removing the particulate metallic material of the solution,
Decomposing the organic acid of the solution,
Removing the metal ions and the organic acid remaining in the solution after the step of decomposing the organic acid,
Measuring the surface dose rate of the piping of the system and deriving the DF value after removing the remaining metal ions and organic acid
Lt; / RTI >
Wherein the solution is drained to the system or to the outside when the DF is not less than the reference value. The method of claim 1,
After the step of removing the particulate metallic material,
Wherein the solution has an iron ion concentration of 2 mM or less. The method of claim 1,
After the step of removing the particulate metallic material,
Removing the metal ion of the solution
Further comprising:
Wherein the iron ion concentration of the solution after the step of removing the metal ion is 2 mM or less. 4. The method of claim 3,
In the step of removing metal ions of the solution,
Wherein the solution is passed through a cation exchange resin to remove the metal ion. delete The method of claim 1,
The step of removing the remaining metal ions and the organic acid when the measured chromium ion concentration is 1 ppm or more in the step of measuring the concentration of the metal ions, a step of injecting an oxidizing agent into the system, A step of injecting a reducing agent at a second concentration into the system, a step of removing the particulate metallic material of the solution, a step of decomposing the organic acid of the solution, and a step of removing the remaining metal ions and organic acid Repeat,
If the chromium ion concentration of the solution measured in the step of measuring the concentration of the metal ion is less than 1 ppm, the step of removing the residual metal ion and the organic acid may be followed by the step of injecting a second concentration of the reducing agent into the system, Removing the particulate metallic material of the solution, decomposing the organic acid of the solution, and removing the remaining metal ions and organic acids
To the systematic decontamination method. delete 3. The method according to claim 2 or 3,
Wherein the oxidizing agent comprises a permanganic acid solution and an inorganic acid solution. 9. The method of claim 8,
Wherein the first concentration of the reducing agent is 100 ppm to 1,000 ppm oxalic acid,
Wherein the second concentration of reducing agent is 1,000 ppm to 3,000 ppm oxalic acid
Decontamination method of phosphorus system. The method of claim 9,
Wherein the organic acid is oxalic acid. 11. The method of claim 10,
Wherein the step of decomposing the organic acid is performed until the decomposition ability of the oxalic acid is 90% to 99%. 11. The method of claim 10,
The step of decomposing the organic acid
A step of injecting a hydrogen peroxide solution
Wherein the systematic decontamination method further comprises: The method of claim 9,
Wherein the step of injecting the reducing agent at the second concentration is performed after the step of injecting the reducing agent at the first concentration for 30 minutes to 1 hour. The method of claim 13,
In the step of injecting the oxidizing agent, the oxidizing step is carried out for 3 to 24 hours after the oxidizing agent is injected,
Wherein the reducing step is performed for 4 to 72 hours after the second concentration of the reducing agent is injected in the step of injecting the reducing agent of the second concentration. The method of claim 1,
In the step of removing the remaining metal ions and organic acid,
Wherein the solution is passed through a mixed phase ion exchange resin to remove the remaining metal ions and organic acid. The method of claim 1,
The step of decomposing the organic acid
A systematic decontamination method that proceeds in a UV reactor.

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