KR101601201B1 - Chelate free chemical decontamination reagent for removal of the dense radioactive oxide layer on the metal surface and chemical decontamination method using the same - Google Patents

Abstract

The present invention relates to a chemical decontaminating agent for removing a sticky radioactive contaminated oxide film on a metal surface containing a reducing agent, a reducing metal ion and an inorganic acid. The chemical decontaminating agent of the present invention comprises a metal surface- It can be effectively dissolved and removed, and the decontamination can be carried out by a process of contacting the radioactive contaminated oxide with the chemical decontamination agent, so that it is economical from the viewpoint of process cost and process time, , Since a reducing agent is used as a main decontaminating agent, it is possible to easily decompose and remove the remaining reducing agent by using an oxidizing agent after decontamination, thereby minimizing the generation of secondary radioactive waste through easy destruction of the decontamination agent, The nuclide can be effectively removed.

Description

TECHNICAL FIELD The present invention relates to a chemical decontamination agent for removing a radioactive contaminated oxide film on a metal surface, and a chemical decontamination method using the same, and a chemical decontamination method using the decontamination reagent,

The present invention relates to a low concentration non-ignition chemical decontaminating agent effective for removing a fixed surface of a radioactive contaminated oxide film on a metal surface, and a chemical decontamination method using the same.

Major metal components constituting the system of a nuclear power plant may be corroded by steam or cooling water circulating in a nuclear power plant, and a sticky metal oxide may be formed as a small amount of corrosion product on its surface. The metal oxide is contaminated by the radioactive material and accumulates the radioactive material in the system of the nuclear power plant.

Furthermore, the radiation emitted from the radioactive material deposited in the system of the nuclear power plant may cause inevitable radiation exposure to the related workers (plant operators and maintenance personnel) and surrounding workers. The metal oxide contains a radioactive nucleus, which makes the radiation level near the system of the nuclear power plant high.

As part of efforts to reduce the radiation exposure of workers in nuclear power plants around the world, the focus is on research to effectively remove the radioactivity attached to steam generators and coolant pumps, which contribute most to workers' exposure. , And a decontamination technique for metal oxide contaminated with radioactivity is being developed.

Decontamination technologies that have been studied so far include chemical decontamination techniques using high concentration and low concentration of oil and inorganic acid chemical decontamination, mechanical decontamination techniques such as cleaning, polishing, high pressure injection, and electrical decontamination techniques.

Conventionally, various chemical decontamination technologies that have been used in the past have used organic acid complexing agents such as oxalic acid, ethylenediaminetetraacetic acid (EDTA), and picolinic acid, which are known to form strong complexes .

(1) For example, the CITROX process, the first developed low-concentration chemical decontamination technique, uses a mixture of organic complexing agent and salt (oxalic acid - 2.5 wt%, dibasic ammonium citrate - 5 wt% and ferric nitrate - 2 wt%).

(2) In Canada, CAN-DECON and CAN-DEREM processes have been developed by upgrading the CITROX process and a chemical called LND-101A containing EDTA: citric acid: oxalic acid = 2: 1: 1 is used.

(3) In addition, the UK and the US jointly developed the LOMI process and used organic acid complexing agents such as picolinic acid to keep the iron ions in complex form in solution.

(4) The CORD process developed in Germany also uses an organic acid complexing agent such as oxalic acid, and it has been reported that precipitation in the form of oxalate during decontamination occurs, thereby making the purification process difficult.

On the other hand, organic acid complexing agents such as oxalic acid, EDTA, PDCA and the like are also used in the prior art related to the primary system decontamination technology of a nuclear power plant including a steam generator and a coolant pump.

(1) For example, in 2005, Stiepani, Germany, presented "Full System Decontamination with HP / CORD UV for Decommissioning of the German PWR Stade" to the International Conference on Structural Mechanics in Reactor Technology There is one.

They reported that repeated application of oxalic acid and permanganic acid in the decontamination process effectively cleared the primary and auxiliary systems of the nuclear power plant and significantly reduced the radiation exposure of the nuclear power plant workers.

(2) Further, Prince et al. Published a "Dissolution Behavior of Magnetite Film Formed Carbon Steel in Dilute Organic Acid Media" in Journal of Nuclear Materials in 2001.

They used EDTA, EDTA-citric acid, EDTA-citric acid-ascorbic acid system and PDCA (Pyridinedicarboxylic acid), PDCA-citric acid, PDCA-citric acid-ascorbic acid system for dissolution of the oxide film.

On the other hand, prior art documents related to the decontamination technique of metal oxides whose surface is radioactively contaminated also include organic acid complexing agents such as oxalic acid in chemical decontamination agents.

(1) For example, Patent Document 1 relates to a chemical decontamination method for decontaminating radionuclides from a metallic material, wherein oxalic acid and hydrazine are brought into contact with a metal material as a reducing agent, and an oxidizing agent such as hydrogen peroxide destroys the reducing agent And the like.

(2) Patent Document 2 discloses a process in which formic acid and oxalic acid are used as a reducing agent salt in the decontamination of radioactive contaminated metal surfaces, and repeatedly subjected to reduction dissolution and oxidation dissolution using ozone, permanganic acid and permanganate as oxidizing agents And hydrogen peroxide solution is also injected to destroy the reducing agent.

(3) Patent Document 3 also discloses a technique of using ozone at a high concentration generated by a solid electrolytic electrolysis process with an oxidizing agent and using oxalic acid as a reducing agent in decontamination of radioactive contaminated metal surfaces. However, in order to remove the oxalic acid, ozone is injected with irradiation of UV light, and ions in the oxalic acid solution are removed by the ion exchange resin.

(4) Patent Document 4 discloses a technique using 0.05 to 0.3 wt% oxalic acid as a reducing decontaminating agent and using a hydrogen peroxide solution and a catalyst such as Pd, Ur, Rh, V, Pd and IR to decompose the reducing decontaminating agent .

(5) Patent Document 5 relates to a method of reducing denitrification chemical reactor internal coolant pump contaminated with radioactive materials, which includes an oxidation process, a decomposition process, and a reduction process, and oxalic acid, which is an organic acid complexing agent, And a short time of 4 hours or less is applied at each step.

(6) Patent Document 6 relates to a chemical decontamination apparatus and a decontamination method using ultrasound and organic acid, which are the main components of a primary system of a nuclear power plant such as a steam generator and a coolant pump in a nuclear power plant, EDTA and ascorbic acid, and a reduction process is applied for 12 hours.

As has been seen, the common features of the prior art techniques are chemical decontamination of the primary system, reactor cooling pump or metallic waste contaminated with radioactivity by a decontamination agent, in order to dissolve the iron component present in the radioactive contaminated oxide film, oxalic acid, formic acid , EDTA, and other organic acid complexing agents.

In order to minimize the amount of radioactive waste generated after decontamination, the organic acid complexing agent must be decomposed or adsorbed onto an ion exchange resin. In order to decompose the organic acid complexing agent, a separate apparatus such as a UV irradiation apparatus is required And if they can not be completely decomposed, they are also left as radioactive waste. Further, even when the organic acid complexing agent is adsorbed by the ion exchange resin, the disposal stability of the radioactive waste is significantly lowered.

Accordingly, the present inventors have been interested in a non-ignitable low-concentration chemical decontaminating agent effective for removing a radioactive contaminated oxide film on a metal surface without using an organic acid complexing agent such as oxalic acid or the like capable of solving the above problems , A reducing agent, a reducing metal ion and an inorganic acid, can effectively and economically remove the radioactive contaminated oxide film.

Patent Document 1: United States Patent No. 06973154 Patent Document 2: U.S. Patent No. 01422724 Patent Document 3: United States Patent No. 06875323 Patent Document 4: United States Patent No. 06335475 Patent Document 5: Korean Patent No. 0856944 Patent Document 6: Korean Patent No. 0605558

It is an object of the present invention to provide an anti-ignition low-concentration chemical decontaminating agent effective for removing a sticky radioactive contaminated oxide film on a metal surface and a chemical decontamination method using the same.

In order to achieve the above object,

The present invention provides a non-accelerating chemical decontaminating agent for removing a sticky radioactive contaminated oxide film containing a reducing agent, a reducing metal ion and an inorganic acid.

In the chemical decontaminating agent of the present invention, the reducing agent is at least one reducing agent selected from the group consisting of NaBH ₄ , H ₂ S, N ₂ H ₄ and LiAlH ₄ .

In the chemical decontamination of the present invention, the reducible metal ion is ⁺ Ag, Ag ^{2 +,} Mn ^{2 +,} Mn ^3+, Co ^{+ 2,} Co ^{+ 3,} Cr ^{+ 2,} Cr ^{+ 3,} Cu ^+, Cu ^{2 At} least one metal ion selected from the group consisting of ⁺ , Mn ^{2 +} , Mn ^{3 +} , Sn ^{2 +} , Sn ^{4 +} Ti ^{2 +} and Ti ^{3 +} .

In the chemical decontaminating agent of the present invention, the inorganic acid is characterized by being one or more inorganic acids selected from the group consisting of HBr, HF, HI, HNO ₃ , H ₃ PO ₄ and H ₂ SO ₄ .

Further, the present invention relates to a method for producing a solution, comprising the steps of: (1) preparing a solution in which a reducing agent is dissolved in distilled water; Adding inorganic acid to said solution of step 1 (step 2); And adding a reducing metal ion to the solution to which the inorganic acid of step 2 is added (step 3).

In addition, the present invention provides a chemical decontamination method comprising the step of bringing the chemical decontamination agent into contact with the surface of the metal on which the radioactive contaminated oxide film is fixed.

The chemical decontaminating agent of the present invention can effectively dissolve and remove the fixation radioactive contaminated oxide film on the metal surface even at a suitable temperature and is effective because the decontamination can be performed by a process of contacting the radioactive contaminated oxide with the chemical decontamination agent.

Furthermore, since the chemical decontaminating agent of the present invention does not use an organic acid complexing agent such as oxalic acid and uses a reducing agent as a main decontaminating agent, the remaining reducing agent can be easily decomposed and removed using an oxidizing agent after decontamination, It is possible to minimize the generation of secondary radioactive waste through one destruction and to effectively remove radionuclides remaining in the decontamination solution.

FIG. 1 is a graph showing a change in dissolution performance of a simulated iron oxide according to an embodiment of the present invention, in which inorganic acid, a reducing agent, and a reducing metal ion are sequentially added.
FIG. 2 is a graph showing the change in dissolution performance of the simulated iron oxide according to the concentration of the reducing agent in the chemical decontamination agent of one embodiment of the present invention. FIG.
3 is a graph showing the change of dissolution performance of the simulated iron oxide according to the change of the reducing metal ion concentration in the chemical decontamination agent having pH 2 and pH 3 in one embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

The present invention provides a non-accelerating chemical decontaminating agent for removing a sticky radioactive contaminated oxide film containing a reducing agent, a reducing metal ion and an inorganic acid.

Conventionally, organic acid complexing agents such as oxalic acid, formic acid and EDTA have been used to dissolve and remove the radioactive contaminated metal oxide film. However, in order to minimize the amount of radioactive waste generated after decontamination, There is a disadvantage in that it is necessary to adsorb the organic acid complexing agent, and a separate apparatus such as a UV irradiation apparatus is required for decomposing the organic acid complexing agent. If the organic acid complexing agent can not be completely decomposed, these are also left as radioactive waste. In addition, when the organic acid complexing agent is adsorbed by the ion exchange resin, the disposal stability of the radioactive waste is significantly lowered.

Since the chemical decontaminating agent of the present invention effectively dissolves the metal component present in the radioactive contaminated metal oxide film to remove radioactivity and does not use an organic acid complexing agent such as oxalic acid and uses a reducing agent as a main decontaminating agent, The remaining reducing agent can be easily decomposed and removed to minimize the generation of secondary radioactive waste through easy destruction of the decontamination agent and effectively remove radionuclides remaining in the decontamination solution.

In addition, according to the chemical decontaminating agent of the present invention, since the reducing metal ion acts as a catalyst, the decontamination process can be performed at a lower temperature to effectively remove radioactivity.

Specifically, in the chemical decontamination agent of the present invention, the reducing agent is at least one reducing agent selected from the group consisting of NaBH ₄ , H ₂ S, N ₂ H ₄ and LiAlH ₄ . The reducing agent serves to remove the radioactive contaminated metal oxide film by the reduction dissolution reaction of the following reaction formula (1)

[Reaction Scheme 1]

Fe ₃ O ₄ + 2e ^- + 8H ^{+ -} > 3Fe ^{2 +} + 4H ₂ O

(Fe ₃ O ₄ is an example of a radioactive contaminated metal oxide film, which means iron oxide).

In the chemical decontamination of the present invention, the reducible metal ion is ⁺ Ag, Ag ^{2 +,} Mn ^{2 +,} Mn ^3+, Co ^{+ 2,} Co ^{+ 3,} Cr ^{+ 2,} Cr ^{+ 3,} Cu ^+, Cu ^{2 At} least one metal ion selected from the group consisting of ⁺ , Mn ^{2 +} , Mn ^{3 +} , Sn ^{2 +} , Sn ^{4 +} , Ti ^{2 +} and Ti ^{3 +} . The reducing metal ion promotes the removal of the radioactive contaminated metal oxide film by the dissolution reaction of the metal inside the radioactive contaminated metal oxide film of the following reaction formula (2).

[Reaction Scheme 2]

Fe ₃ O ₄ + 2M ⁺ + 8H ^{+ -} > 3Fe ^{2 +} + 2M ^{2 +} + 4H ₂ O

(M ⁺ means a reducing metal ion).

In the chemical decontaminating agent of the present invention, the inorganic acid is at least one inorganic acid selected from the group consisting of HBr, HF, HI, HNO ₃ , H ₃ PO ₄ and H ₂ SO ₄ . The inorganic acid serves to remove the radioactive contaminated metal oxide film by the acid dissolution reaction of the following reaction formula (3).

[Reaction Scheme 3]

Fe ₃ O ₄ + 8H ^{+ -} > 2Fe ^{3 +} + Fe ^{2 +} + 4H ₂ O

On the other hand, in the chemical decontaminating agent of the present invention, the metal surface fixation radioactive contaminated oxide film is generated inside the system of the nuclear power plant.

Major metal components constituting the system of the nuclear power plant may be corroded by steam or cooling water circulating in a nuclear power plant, and a fixing metal oxide may be formed as a small amount of corrosion product on the surface thereof. Since the metal oxide contains a radionuclide, the radioactive material accumulated in the system causes an increase in the radiation dose of the operator. Therefore, the chemical decontamination agent of the present invention is particularly useful for removing the sticky radioactive contaminated oxide film on the metal surface occurring in the system of the nuclear power plant.

In the chemical decontaminating agent of the present invention, the metal on which the sticky radioactive contaminated oxide film is formed may be one or more selected from stainless steel, inconel steel and zirconium alloy.

On the other hand, in the chemical decontamination agent of the present invention, the concentration of the reducing agent is preferably 5 × 10 ^-4 to 0.5 M. If the concentration of the reducing agent is less than 5 x 10 < ^-4 > M, the reducing ability can not be sufficiently exhibited. If the concentration is more than 0.5M,

In the chemical decontamination agent of the present invention, the concentration of the reducing metal ion is preferably 1 x 10 ^-5 - 0.1 M. When the concentration of the reducing metal ion is less than 1 x 10 < ^-5 > M, the decontamination effect is reduced. When the concentration is less than 0.1 M, precipitates of metal components are formed.

Further, in the chemical decontamination agent of the present invention, the concentration of the inorganic acid is preferably 1 × 10 ^-4 to 0.5 M. When the concentration of the inorganic acid is less than 1 x 10 < ^-4 > M, the decontamination effect decreases. If the concentration exceeds 0.5 M, a large amount of neutralizing agent is required to neutralize the detergent.

Conventionally, in the case of the non-accelerating chemical decontaminating agent for removing the sticky radioactive contaminated oxide film on the metal surface, high concentration chemical decontamination using a decontamination substance at a high concentration of 1 wt% or more can obtain a large decontamination coefficient, . Further, in the case of low concentration chemical decontamination using a decontamination substance at a concentration of less than 1% by weight, the amount of secondary wastes generated is small and the treatment thereof is easy. However, the decontamination coefficient is not large and a long decontamination time There was a disadvantage required.

According to the chemical decontaminating agent of the present invention, a reducing agent having a concentration of 5 × 10 ^-4 to 0.5 M, a reducing metal ion having a concentration of 1 × 10 ^-5 to 0.1 M and an inorganic acid having a concentration of 1 × 10 ^-4 to 0.5 M, It is possible to perform decontamination effectively in a short period of time even with a chemical decontaminating agent, and it is advantageous in that the amount of secondary waste generated is small and the treatment thereof is easy.

Meanwhile, the pH of the chemical decontamination agent of the present invention is preferably controlled within the range of 1.0 to 3.7, depending on the purpose of decontamination. If the pH is less than 1.0, there arises a problem of corrosion on metal materials. If the pH is more than 3.7, the decontamination effect is reduced.

Further,

Preparing a solution in which the reducing agent is dissolved in distilled water (step 1);

Adding inorganic acid to said solution of step 1 (step 2); And

And adding a reducing metal ion to the solution containing the inorganic acid in step 2 (step 3).

Hereinafter, the method for producing the chemical decontaminating agent of the present invention will be described in detail.

First, in the method for producing a chemical decontamination agent of the present invention, Step 1 is a step of preparing a solution in which a reducing agent is dissolved in distilled water.

The reducing agent in step 1 is at least one reducing agent selected from the group consisting of NaBH ₄ , H ₂ S, N ₂ H ₄ and LiAlH ₄ , and the concentration of the reducing agent dissolved in the distilled water is 5 × 10 ^-4 to 0.5 M desirable.

Next, in the method for producing a chemical decontamination agent of the present invention, Step 2 is a step of adding inorganic acid to the solution of Step 1 above.

The inorganic acid in step 2 is at least one inorganic acid selected from the group consisting of HBr, HF, HI, HNO ₃ , H ₃ PO ₄ and H ₂ SO ₄ and is preferably added in a concentration of 1 × 10 ^-4 to 0.5 M Do.

In addition, the inorganic acid in step 2 serves to control the pH of the chemical decontamination agent, and it is preferable to adjust the pH to the range of 1.0 to 3.7 depending on the purpose of decontamination.

Next, in the method for producing a chemical decontamination agent of the present invention, Step 3 is a step of adding a reducing metal ion to the solution containing the inorganic acid in Step 2.

Reducing the metal ions of step 3, ^{Ag +, Ag 2 +, Mn} 2 +, Mn 3 +, Co 2 +, Co 3 +, Cr 2 +, Cr 3+, Cu +, Cu 2 +, Mn 2 +, At least one metal ion selected from the group consisting of Mn ^{3 +} , Sn ^{2 +} , Sn ^{4 +} Ti ^{2 +} and Ti ^{3 +} , and is preferably added at a concentration of 1 × 10 ^-5 to 0.1 M.

Further, the reducing metal ion in step 3 may be added in the form of an ion or an ion pair by adding a metal salt. For example, Cl ^- , NO ₃ ^- , SO ₄ ^{2 -} and the like may be used as the anion of the metal salt, but the present invention is not limited thereto.

On the other hand, the present invention provides a chemical decontamination method comprising the step of contacting the surface of the chemical decontamination agent with a metal to which a radioactive contaminated oxide film is fixed.

The chemical decontamination method of the present invention can be performed by immersing the surface of the chemical decontaminating agent in a metal on which a radioactive contaminated oxide film is fixed on the surface or by passing the chemical decontaminating agent into a system or a loop of a nuclear power plant.

In addition, the chemical decontamination method of the present invention is preferably performed at a temperature in the range of 70 - 140 캜. If the decontamination temperature is lower than 70 deg. C, the decontamination effect is reduced. If the decontamination temperature is higher than 140 deg. C, the process becomes complicated due to an increase in vapor pressure.

Further, the chemical decontamination method of the present invention is preferably performed for 2 to 26 hours. If the decontamination time is less than 2 hours, the reaction can not proceed completely. If the decontamination time exceeds 26 hours, the decontamination effect is not sufficient.

According to the chemical decontamination method of the present invention, since the reducing metal ion acts as a catalyst, the decontamination process can be performed at a lower temperature to effectively remove the radioactive contaminated oxide, and the radioactive contaminated oxide is contacted with the chemical decontaminating agent It is economical in terms of process cost and process time.

Hereinafter, the present invention will be described in detail with reference to the following examples and experimental examples.

However, the following examples and experimental examples are illustrative of the present invention, but are not limited thereto.

< Example  1> Preparation of reducing agent + reducing metal ion + inorganic acid chemical decontaminating agent

N ₂ H ₄ as a reducing agent was dissolved in distilled water to a concentration of 0.07 M, and then 0.0005 M of Cu ⁺ was added as a reducing metal ion, and 0.07 M of nitric acid was added as inorganic acid to adjust the pH to 3, A chemical decontamination agent was prepared.

< Comparative Example  1> Preparation of inorganic acid-based chemical decontaminating agent

0.003 M of nitric acid as an inorganic acid was added to distilled water to prepare a chemical decontaminating agent of Comparative Example 1. [

< Comparative Example  2> Preparation of reducing agent + inorganic acid chemical decontaminating agent

To the distilled water was added N ₂ H ₄ as a reducing agent at a concentration of 0.07 M and 0.07 M nitric acid was added as an inorganic acid to prepare a chemical decontaminating agent of Comparative Example 2.

< Experimental Example  1> Evaluation of metal oxide dissolution performance of chemical decontamination agent

In order to evaluate the metal oxide dissolution performance of the chemical decontaminating agent of the present invention, the amount of the iron component dissolved from the simulated iron oxide of the chemical decontaminating agent of Example 1 and Comparative Example 1 - 2 was evaluated, .

The metal oxide dissolution performance was evaluated at 95 캜 for 2 hours, and FIG. 1 is based on the iron component concentration of 18 ppm in the aqueous solution when the simulated iron oxide was completely dissolved at pH 3.

As a result, referring to Fig. 1, the dissolution rate of the chemical decontaminating agent of Comparative Example 1 containing only nitric acid was less than 0.002 even after 2 hours at 95 캜, but the iron component was hardly dissolved, while nitric acid and a reducing agent In the case of the chemical decontaminating agent of Comparative Example 2, the dissolution rate rose to 0.72, and in the case of the chemical decontaminating agent of Comparative Example 3 in which nitric acid, a reducing agent and a reducing metal ion were added, the dissolution rate was 1, indicating that the iron component was completely dissolved.

From the above experimental results, it can be seen that the chemical decontaminating agent of the present invention has the effect of effectively removing the radioactive contaminated metal oxide even with a low concentration of chemical decontamination agent, without using an organic complexing agent.

< Experimental Example  2> Evaluation of metal oxide dissolution performance by changing the concentration of reducing agent

In order to evaluate the metal oxide dissolution performance of the chemical decontaminating agent according to the concentration of the reducing agent, the concentration of N ₂ H ₄ reducing agent of the chemical decontamination agent was changed from 0.000007 M to 0.07 M in the absence of reducing metal ion The amount of iron component dissolved from the simulated iron oxide was evaluated when the concentration of nitric acid was changed from 0.002 M to 0.07 M in order to maintain the pH of the solution at 3. The results are shown in FIG.

The evaluation of the metal oxide dissolution performance according to the reducing agent concentration was carried out at 150 ° C. for 2 hours and FIG. 2 is based on the iron component concentration of 36 ppm in the aqueous solution when the simulated iron oxide was completely dissolved at pH 3.

As a result, referring to FIG. 2, it can be confirmed that when the reducing agent concentration of the chemical decontamination agent of the present invention is 0.007 M or higher, 18 ppm iron component is dissolved within 2 hours.

From the above experimental results, it can be seen that the decontamination effect comparable to the chemical decontaminating agent of the present invention can not be obtained because the chemical decontaminating agent using only N ₂ H _{4 as a} reducing agent proceeds slowly at a high temperature of 150 ° C.

< Experimental Example  3> Evaluation of metal oxide dissolution performance by changing the concentration of reducing metal ion

In order to evaluate the metal oxide dissolution performance of the chemical decontaminating agent of the present invention with respect to the change of the reducing metal ion concentration, a chemical decontaminating agent containing 0.07 M of reducing agent, 0.15 M nitric acid (pH adjusted to 2) or 0.07 M (pH 3) The amount of the iron component dissolved from the simulated iron oxide was evaluated while changing the concentration of the reducing metal ion to 26 x 10 &lt; ^{-4 &} gt ;. The results are shown in Fig. The metal oxide dissolution performance was evaluated at 95 ℃ for 2 hours according to the reductive metal ion concentration.

As a result, referring to FIG. 3, it can be seen that when a certain amount of reducing metal ion is added, the dissolution amount of the iron component is higher at a pH of 3 compared to the pH of 2.

Further, under the condition of pH 3, it can be confirmed that the amount of the reducing component is increased by increasing the concentration of the reducing metal ion to 5 × 10 ^-4 M, and the amount of the iron component is almost the same at the higher concentration.

In addition, it can be seen that, under the condition of pH 2, the amount of the iron component dissolved increases as the concentration of the reducing metal ion to be added increases to 2 × 10 ^-3 M, but becomes constant at the higher concentration.

The pH of the chemical decontaminating agent of the present invention can be controlled within a range of 1.0 to 3.7 according to the purpose of decontamination. From the above experimental results, it can be seen that when the radioactive contaminated metal oxide is iron oxide, the dissolution rate is better than pH 2 have.

Claims (11)

0.07 M concentration of N ₂ H ₄ reducing agent, a reducing metal ion, and 0.07 M concentration of HNO _3, H ₃ PO ₄ and H ₂ is only composed of one or more inorganic acids selected from the group consisting of SO ₄ as in the nuclear power plant system Characterized in that it is used in decontamination and is used in a temperature range of 70 to 140 占 폚 and at a pH of 3. The non-repellent chemical decontaminating agent for removing sticky radioactive contaminated oxide film containing metal oxides.
delete According to claim 1, wherein said reducible metal ions ⁺ Ag, Ag ^{+ 2,} Mn ^{+ 2,} Mn ^{+ 3,} Co ^{+ 2,} Co ^{+ 3,} Cr ^2+, Cr ^{+ 3,} Cu ^+, Cu ^{2 +,} Mn ^{+ 2,} Mn ^{+ 3,} Sn ^{+ 2,} Sn ^{+ 4,} Ti ^{+ 2,} and the chemical decontamination, characterized in that at least one metal ion selected from the group consisting of Ti ^{3 +.}
The chemical decontamination agent according to claim 1, wherein the metal is at least one selected from the group consisting of stainless steel, inconel steel and zirconium alloy.
delete The chemical decontamination agent according to claim 1, wherein the concentration of the reducing metal ion is 1 × 10 ^-5 to 0.1 M.
delete A chemical decontamination method comprising the step of contacting the chemical decontaminating agent of claim 1 to a surface of a metal to which a radioactive contaminated oxide film is adhered, at a temperature ranging from 70 to 140 캜.
The chemical decontamination method according to claim 8, wherein the chemical decontamination method is carried out by immersing the surface of the metal contaminated with the radioactive contaminated oxide film in the chemical decontaminating agent of claim 1.
The chemical decontamination method according to claim 8, wherein the chemical decontamination method is carried out by passing the chemical decontaminating agent of claim 1 into a system or a loop of a nuclear power plant.
The method of chemical decontamination according to claim 8, wherein the chemical decontamination method is performed for 2 to 26 hours.

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