KR100605558B1 - Chemical Decontamination Apparatus and Process Using Ultrasonic Wave and Organic Acid - Google Patents

Abstract

The present invention relates to a process and apparatus for chemically removing radioactive pollutants accumulated on the surface of these components for the main components of the nuclear power plant, such as steam generators and coolant pumps in the nuclear power plant, A chemical decontamination apparatus, comprising: a decontamination tank having an ultrasonic generator installed therein for storing decontamination agents; An electric heater for controlling the temperature of the decontamination agent; filter; A cation resin tower filled with a strong acid type cation exchange resin having a sulfonic acid as a functional group; An interphase resin tower in which an anion exchange resin having a quaternary amine as a functional group is mixed with a cation exchange resin; And an activated carbon tower filled with activated carbon.

Chemical decontamination, decontamination agents, nuclear power plant components, ion exchange resins, activated carbon

Description

Chemical Decontamination Apparatus and Process Using Ultrasonic Wave and Organic Acid}             

1 is an overall configuration diagram of a chemical decontamination apparatus according to the present invention.

<Description of the symbols for the main parts of the drawings>

10: decontamination tank 11: chemical injection pump

12: ultrasonic generator 13: electric heater

14 filter 15 exhaust port

16: cation resin tower 17: anion resin tower

18: activated carbon tower 19: flow meter

20: circulation pump 21: drain

22: sampling hole 23: the basket

24: basket 31: the first valve

32: second valve 33: third valve

34: fourth valve 35: fifth valve

36: sixth valve 37: seventh valve

38: eighth valve 39: ninth valve

40: tenth valve 41: eleventh valve

42: twelfth valve 43: thirteenth valve

44: 14th valve 45: 15th valve

46: 16th Valve 47: 17th Valve

48: 18th valve 49: 19th valve

The present invention relates to a chemical decontamination apparatus and process using ultrasonic waves and organic acids.

More specifically, the present invention relates to a process and an apparatus for chemically removing radioactive contaminants accumulated on the surface of the nuclear power plant, for the main components of the nuclear power plant such as steam generators and coolant pumps. will be.

During planned preventive maintenance, which is a regular maintenance period for nuclear power plants, plant operators and maintenance personnel are inevitably exposed to radiation from radioactive materials deposited within the system.

In reality, this method cannot be completely prevented, but various methods and equipment are used to minimize radiation exposure based on the ALARA (As Low As Reasonably Achievable) concept, such as the installation of a radiation shield or the use of a remote work facility.

Nevertheless, as the operation history of nuclear power plants increases, the radiation exposure of workers due to accumulated radioactive material in the system is increasing. In particular, the radiation exposure received by workers during the maintenance of steam generators and coolant pumps with high radiation levels. This is the most.

Recently, ICRP-60 of the International Commission on Radiological Protection (ICRP) recommends setting the annual allowable exposure of nuclear workers to lower than 5rem, and can actively cope with such strict radiation management regulations. To this end, there is an urgent need to develop technologies that can lower the radiation dose of related systems and devices.

Nuclear power plants around the world focus on research to effectively remove radiation attached to steam generator chambers and coolant pumps, which contribute to the workers 'exposure, as part of efforts to reduce workers' radiation exposure. We are looking for ways to eliminate it. As a result, decontamination techniques using mechanical, electrical and chemical methods have been developed.

Currently, various decontamination processes have been developed worldwide and are used not only in laboratories but also on nuclear power plants. In the field of chemical decontamination, considerable experience and know-how have been accumulated.

However, up to the 1960s, the early stage of the decontamination process, most chemical decontamination processes used high concentrations of chemicals, resulting in damage to the base material and disposal and disposal of radioactive waste.

At present, low-density chemical decontamination processes have been developed and used to minimize the disadvantages of high-density chemical decontamination processes and use only a small amount of low-density chemicals to produce the least amount of waste. Chemical decontamination process.

The present invention has been made in response to the above development demands, and an object of the present invention is to provide a relatively low concentration of chemical decontamination agents on the surface of radioactive components that cause radioactive exposure of nuclear power workers during the regular maintenance period of nuclear power plants. Use to remove. In this process, the conventional chemical decontamination process, such as the generation of a large amount of waste or damage to the base metal, improves the problems and optimizes the condition variables of the decontamination process to reduce the work time and to remove the ultrasonic wave and organic acid to suppress the radiation exposure of the decontamination worker. To provide a chemical decontamination apparatus and process used.

One embodiment of the present invention for achieving the above object is a chemical decontamination apparatus, the ultrasonic generator is installed inside, the decontamination tank for storing the decontamination agent; An electric heater for controlling the temperature of the decontamination agent; filter; A cation resin tower filled with a strong acid type cation exchange resin having a sulfonic acid as a functional group; A mixed bed resin column in which an anion exchange resin having a quaternary amine as a functional group is mixed with a cation exchange resin; And an activated carbon tower filled with activated carbon.

In addition, another embodiment of the present invention, in the chemical decontamination method, (1) forming a first decontamination solution by putting a predetermined chemical and pure water in a decontamination tank to which the specimen is attached; (2) adjusting the flow rate by adjusting the opening degree of the first valve and then raising the temperature of the first decontamination liquid by a predetermined temperature by an electric heater; (3) circulating the first decontamination solution for a predetermined time at a predetermined temperature; (4) closing the eleventh valve and opening the nineteenth valve to circulate the activated carbon tower with the first decontamination liquid; (5) injecting a second salt solution into the salt bath and rotating for a predetermined time; (6) injecting a predetermined chemical into the salt bath and injecting a predetermined solution to form a third anti-saline solution and circulating for a predetermined time; (7) opening the eleventh valve, closing the nineteen valve to separate the activated carbon tower, and then discharging the activated carbon inside the activated carbon tower and filling it with new activated carbon; (8) circulating the fourth decontamination solution into the activated carbon tower after injecting a fourth decontamination solution into the decontamination tank; (9) filling the cation exchange column and the anion ion exchange resin in the cation resin tower and anion resin tower; (10) Close the 19th valve and open the 3rd valve to allow the 4th decontamination solution to circulate for a predetermined time through the cation resin tower, and then close the 3rd valve and open the 5th valve to open the 4th decontamination solution to the anion resin tower for a predetermined time. To circulate during the process; And (11) opening the eleventh valve, the twelfth valve, the fourteenth valve, and closing the fifth and thirteenth valves to allow the fourth decontamination liquid to pass through the filter for a predetermined time. .

The present invention focuses on the decontamination and decontamination process for chemical decontamination for components of a domestic PWR-type power plant. Use the method.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

As shown in FIG. 1, a plurality of valves 31 to 49 and an ultrasonic generator 12 are installed therein, a decontamination tank 10 for storing a decontamination agent, and a decontamination agent of the decontamination agent. An electric heater 13 for controlling temperature, a filter 14, a cation resin tower 16 filled with a strong acid type cation exchange resin containing sulfonic acid as a functional group, and an anion exchange resin having a quaternary amine as a functional group. It consists of a mixed-phase resin tower mixed with a cation exchange resin, and an activated carbon tower 18 filled with activated carbon.

The decontamination tank 10 has a capacity of about 160 liters, and the ultrasonic generator () facilitates the flow of the decontamination agent and allows the oxide film of the decontamination object to be easily detached into the decontamination agent.

The electric heater 13 is composed of two sets of operation, one electric heater so that the temperature of the decontamination agent is raised to a temperature 2 ℃ lower than the set temperature, the temperature difference between the set temperature and the decontamination agent is 2 ℃ or less When the temperature of the decontamination agent is raised by another electric heater.

The filter 14 is provided with two upper and lower, and the replacement of the filter 14 is made when the pressure difference of the pressure gauge installed at the front and rear of the filter is 0.15 mPa or more.

The activated carbon filled in the activated carbon tower 18 is activated carbon having a specific gravity of 0.40 to 0.45 g / cm 3, a particle diameter of 8 to 32 mesh, and an ignition residue of 0.5% or less.

Referring to the chemical decontamination method using the ultrasonic and organic acids configured as described above are as follows.

First, while all other valves are closed, open the eighteenth valve 48, and in the decontamination tank to which the specimen is attached, use 70.2 g of potassium permanganate (KMnO ₄ ) and 63 ml of phosphoric acid (H ₃ PO ₄ ) by using a chemical injection pump (11). After the injection, pure water was added so that the total volume of the solution was 140 L (first decontamination solution) so that the weight ratio of potassium permanganate and phosphoric acid was 0.05% and 0.025%, respectively, and then the 18th valve 48 was closed.

In addition, after the first valve 31, the second valve 32, the eleventh valve 41, the thirteenth valve 43, and the fifteenth valve 45 are opened, the circulation pump 20 and the ultrasonic generator 12 are opened. ) To work.

Then, the opening degree of the first valve 31 is adjusted to adjust the flow rate to 30 l / min, and the air heater 13 waits until the temperature reaches the set value, and if necessary, opens the sixteenth valve 46 to exhaust the air. Let's do it.

And the 1st decontamination liquid is circulated for about 6 to 8 hours at the temperature of 85 degreeC. At this time, by the following reaction, the insoluble chromium oxide dichromate (HCrO ₄ ^-) it is eluted into the salt solution to form.

^{_{Cr 2 O 3 + 2MnO 4 -}} + H 2 O → 2HCrO 4 - + 2MnO 2

Then, the eleventh valve 41 is closed and the nineteenth valve 49 is opened to cause the first decontamination solution to circulate through the activated carbon tower 18 to remove unreacted phosphoric acid and dichromic acid.

In order to decompose the oxidizing agent, 140 ml of hydrogen peroxide solution having a weight ratio of 30% is slowly injected using the chemical injection pump 23 (second decontamination solution), and then circulated for about 6 periods. At this time, permanganate ions and manganese dioxide (MnO ₂ ) remaining in the decontamination solution are reduced by hydrogen peroxide to generate manganese ions (Mn ²⁺ ) and oxygen (O ₂ ).

2MnO ₄ ^2- + 5H ₂ O ₂ + 6H ⁺ → 2Mn ²⁺ + 8H ₂ O + 5O ₂

MnO ₂ + H ₂ O ₂ + 2H ⁺ → Mn ²⁺ + 2H ₂ O + O ₂

Then, 280 g of oxalic acid (H ₂ C ₂ O ₄ ) was put into the decontamination tank 10 through the chemical injection pump 23, and the weight ratio of EDTA was 2.6% and the weight ratio of ascorbic acid was 0.85%. 280 g are then injected (third decontamination solution) and circulated for about 12 hours. In this process, magnetite (Fe ₃ O ₄ ), nickel ferrite (NiFe ₂ O ₄ ), hematite (Fe ₂ O ₃ ), and the like are eluted into the decontamination solution while forming a complex by excess oxalic acid and EDTA. The reaction taking place is as follows.

Fe ₃ O ₄ + 3H ₂ C ₂ O ₄ → 3FeC ₂ O ₄ + 3H ₂ O + 1 / 2O ₂

NiFe ₂ O ₄ + 3H ₂ C ₂ O ₄ → 2FeC ₂ O ₄ + NiC ₂ O ₄ + 3H ₂ O + 1 / 2O ₂

Fe ₂ O ₃ + 4H ₂ C ₂ O ₄ → FeC ₂ O ₄ + 2H ₂ O + 1 / 2O ₂

Fe ₃ O ₄ + 3Na ₂ -EDTA + 3H ₂ O → 3Fe-EDTA + 6NaOH + 1 / 2O ₂

NiFe ₂ O ₄ + 3 Na ₂ -EDTA + 3H ₂ O

→ Ni-EDTA + 2Fe-EDTA + 6NaOH + 1 / 2O ₂

Fe ₂ O ₃ + 2Na ₂ -EDTA + 2H ₂ O → 2Fe-EDTA + 4NaOH + 1 / 2O ₂

Then, after opening the first valve 31 and closing the nineteenth valve 49 to separate the activated carbon tower 18, the activated carbon in the activated carbon tower 18 is discharged and removed, and 5 L of fresh activated carbon is filled.

Then, 140 ml of hydrogen peroxide water having a weight ratio of 30% is injected into the decontamination tank 10 again (fourth decontamination solution), and the eleventh valve 41 is closed again, and the nineteenth valve 49 is opened to make it into the activated carbon tower 18. Circulate the salt solution. At this time, the circulation was continued until the concentrations of EDTA and ascorbic acid were 0.01% and 0.02% or less, respectively. At this time, EDTA and oxalic acid (H ₂ C ₂ O ₄ ) remaining in the decontamination solution is decomposed by hydrogen peroxide or adsorbed on activated carbon. The remaining ascorbic acid is also oxidized to carbon dioxide (CO ₂ ).

_{Na 2 -EDTA + 25H 2 O 2} → 10CO 2 + 32H 2 O + 2NO 3 - + 2Na +

H ₂ C ₂ O ₄ + H ₂ O ₂ → 2H ₂ O + 2CO ₂

Then, the cation resin tower 16 and the anion resin tower 17 are filled with 5 l of cation exchange resin and anion exchange resin, respectively.

Then, the 19th valve 49 is closed and the 3rd valve 33 is opened to allow the 4th decontamination liquid to circulate for about 3 hours by the cation resin tower 16, and then the 3rd valve 33 is closed again and the 5th valve (35) is opened to circulate the fourth decontamination solution to the anion resin tower 17 for about 3 hours.

The reaction in the cationic resin tower 16 is as follows.

Mn ²⁺ + 2H: R → Mn: R ₂ + 2H ⁺

FeC ₂ O ₄ + 2H: R → Fe: R ₂ + H ₂ C ₂ O ₄

NiC ₂ O ₄ + 2H: R → Ni: R ₂ + H ₂ C ₂ O ₄

Fe-EDTA + 2H: R → Fe: R ₂ + H ₂ -EDTA

Ni-EDTA + 2H: R → Ni: R ₂ + H ₂ -EDTA

The reaction in the anion resin tower 17 is as follows.

H ₂ C ₂ O ₄ + 2R: OH → R ₂ C ₂ O ₄ + 2H ₂ O

H ₂ -EDTA + 2R: OH → R ₂ -EDTA + 2H ₂ O

After the eleventh valve 41, the twelfth valve 42, and the fourteenth valve 44 are opened, and the fifth valve 45 and the thirteenth valve 43 are closed, the fourth decontamination liquid is filtered for about one hour. Let it pass (14).

Therefore, the chemical decontamination apparatus and process according to the present invention uses a lower concentration of chemical decontamination agents and organic acids that are harmless to the human body, compared to conventional decontamination processes, thereby minimizing damage to the base metal and various risks due to the handling of toxic chemicals by workers. It also eliminates the amount of waste generated. In particular, since there is no risk of damage to the base metal, it can be useful for decontamination of components made of expensive materials, and the amount of waste generated is small, which greatly reduces the burden of radioactive waste disposal due to the generation of radioactive waste during decontamination of nuclear power systems. have.

Claims (11)

In chemical decontamination apparatus, Ultrasonic generator is installed inside, the decontamination tank for storing the decontamination agent; An electric heater for controlling the temperature of the decontamination agent; filter; A cation resin tower filled with a strong acid type cation exchange resin having a sulfonic acid as a functional group; An interphase resin tower in which an anion exchange resin having a quaternary amine as a functional group is mixed with a cation exchange resin; And Activated carbon tower filled with activated carbon; Chemical decontamination apparatus using ultrasonic and organic acids, characterized in that consisting of. The method of claim 1, wherein the electric heater, It is composed of two sets and operates. One electric heater causes the temperature of the decontamination agent to be raised to a temperature lower than the set temperature by 2 ° C, and the other electric heater when the temperature difference between the set temperature and the decontamination agent is 2 ° C or less. Chemical decontamination apparatus using the ultrasonic wave and the organic acid, characterized in that to increase the temperature of the decontamination agent. The method of claim 1, wherein the filter, The upper and lower two are mounted, and the replacement of the filter is a chemical decontamination apparatus using ultrasonic and organic acids, characterized in that when the differential pressure of the pressure gauge installed at the front and rear of the filter is 0.15mPa or more. According to claim 1, The activated carbon filled in the activated carbon tower, Chemical decontamination apparatus using ultrasonic and organic acids, characterized in that the specific gravity is 0.40 ~ 0.45g / cm3, the particle size is 8 ~ 32mesh, the ignition residue is 0.5% or less. In the chemical decontamination method, (1) forming a first decontamination solution by putting a predetermined chemical and pure water in a decontamination tank to which the specimen is attached, and then operating the ultrasonic generator; (2) adjusting the flow rate by adjusting the opening degree of the first valve and then raising the temperature of the first decontamination liquid by a predetermined temperature by an electric heater; (3) circulating the first decontamination solution for a predetermined time at a predetermined temperature; (4) closing the eleventh valve and opening the nineteenth valve to circulate the activated carbon tower with the first decontamination liquid; (5) injecting a second salt solution into the salt bath and rotating for a predetermined time; (6) injecting a predetermined chemical into the salt bath and injecting a predetermined solution to form a third anti-saline solution and circulating for a predetermined time; (7) opening the eleventh valve, closing the nineteen valve to separate the activated carbon tower, and then discharging the activated carbon inside the activated carbon tower and filling it with new activated carbon; (8) circulating the fourth decontamination solution into the activated carbon tower after injecting a fourth decontamination solution into the decontamination tank; (9) filling the cation exchange column and the anion ion exchange resin in the cation resin tower and anion resin tower; (10) Close the 19th valve and open the 3rd valve to allow the 4th decontamination solution to circulate for a predetermined time through the cation resin tower, and then close the 3rd valve and open the 5th valve to open the 4th decontamination solution to the anion resin tower for a predetermined time. To circulate during the process; And (11) allowing the fourth decontamination solution to pass through the filter for a predetermined time after opening the eleventh valve, the twelfth valve, the fourteenth valve, and closing the fifth and thirteenth valves; Chemical decontamination method using ultrasonic and organic acids, characterized in that consisting of. The method of claim 5, wherein the first decontamination solution, Pure water is added to 70.2 g of potassium permanganate (KMnO ₄ ) and 63 ml of phosphoric acid (H ₃ PO ₄ ) to form a total volume of 140 L. The weight ratio of potassium permanganate and phosphoric acid is 0.05% and 0.025%, respectively. Chemical decontamination method using ultrasonic wave and organic acid. The method of claim 5, wherein the second decontamination solution, It consists of 140 ml of hydrogen peroxide water at a weight ratio of 30%, The permanganate ions and manganese dioxide (MnO ₂ ) remaining in the first decontamination solution are reduced by hydrogen peroxide to generate manganese ions (Mn ²⁺ ) and oxygen (O ₂ ) Decontamination method. The method of claim 5, wherein the third decontamination solution, 280 g of oxalic acid (H ₂ C ₂ O ₄ ), a weight ratio of EDTA 2.6%, ascorbic acid (ascorbic acid) solution of the chemical salt using an organic acid, characterized in that consisting of 280g of 0.85%. The method of claim 8, Magnetite (Fe ₃ O ₄ ), nickel ferrite (NiFe ₂ O ₄ ), hematite (Fe ₂ O ₃ ) is characterized in that the complex is formed by the oxalic acid and EDTA present in excess to elute into the third decontamination solution. Chemical decontamination method using ultrasonic wave and organic acid. The method of claim 5, wherein the fourth decontamination solution, It consists of 140 ml of hydrogen peroxide water at a weight ratio of 30%, The fourth decontamination solution is a chemical decontamination method using ultrasonic and organic acids, characterized in that continuously circulating in the activated carbon tower 18 until the concentration of EDTA and ascorbic acid is 0.01%, 0.02% or less, respectively. The method of claim 10, EDTA and oxalic acid (H ₂ C ₂ O ₄ ) remaining in the first decontamination solution are decomposed by hydrogen peroxide or adsorbed on activated carbon, the remaining ascorbic acid is oxidized to change to carbon dioxide (CO ₂ ), characterized in that Chemical decontamination method using ultrasonic wave and organic acid.

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