A radionuclide composite decontaminant and its use method and purpose

Abstract

The present invention relates to a radionuclide composite decontaminant and a method for using and applying the same. The composite decontaminant comprises the following components: ammonium chloride, an oxidant, an alkaline agent, an organic acid, a cleaning agent, and a solvent. The method for using the composite decontaminant comprises the following steps: (1) cleaning a measuring container to be decontaminated with a solvent; and (2) adding the composite decontaminant to the measuring container to be decontaminated described in step (1) and allowing the decontaminant to stand. The composite decontaminant provided by the present invention can efficiently remove radionuclides adsorbed on the measuring container at room temperature, meeting the requirement that the total gamma specific activity of residual radionuclides is less than 5 Bq / L, and can be reused. Furthermore, the composite decontaminant is simple to use and does not require the use of ultrasound, heating, or other equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of radionuclide decontamination, and in particular relates to a radionuclide composite decontaminant and a use method and application thereof. Background Art

[0002] Under normal operating conditions, radioactive liquid effluents from nuclear power plants contain activated corrosion products (such as Ag-110m, Co-58, Co-60, Cr-51, Mn-54, and Fe-59) and fission products (such as Cs-137, Sr-90, and I-131). Most of these radionuclides exist in ionic form, while Ag-110m, Co-60, and Co-58 tend to convert to colloidal form. These nuclides adsorb on the inner walls of measurement vessels, making them difficult to remove and potentially interfering with measurement results. Therefore, measurement vessels must be decontaminated after use to remove adsorbed radionuclides and minimize the risk of restricted emissions.

[0003] CN113881513A discloses a detergent for decontaminating reactor components in a nuclear power plant. The detergent contains, by mass percentage, 2-5% of an organic acid, 0.1-5% of a complexing agent, 5-15% of a nonionic surfactant, 2-8% of anionic surfactant, 0.1-4% of a thickener, and 60-75% of water. The method of use comprises the following steps: (1) placing disassembled components containing metal oxides to be decontaminated in an ultrasonic cleaning tank; (2) mixing the detergent with water and adding the mixture to the ultrasonic cleaning tank, and ultrasonically cleaning the components to be decontaminated.

[0004] The aforementioned decontamination reagents are all designed to remove contamination from metal surfaces. The standards achieved after decontamination are relatively low, requiring only a surface dose rate close to background levels (approximately 0.3 μSv / h). These reagents also require ultrasonic cleaning at relatively high temperatures, resulting in a long decontamination time. However, the liquid effluent measurement containers used in nuclear power plants are typically Marlin cups made of polypropylene (PP). Existing decontamination reagents are ineffective against polypropylene, making it difficult to meet the requirement for a residual radionuclide total gamma specific activity of less than 5 Bq / L.

[0005] Therefore, developing a radionuclide decontamination reagent that has good decontamination effect on polypropylene devices and does not require ultrasonic cleaning is a technical problem that technicians in this field urgently need to solve. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a radionuclide composite decontaminant and its use method and purpose. The composite decontaminant can efficiently remove radionuclides adsorbed on a measuring container at room temperature, is reusable, and is simple to operate without the need for ultrasound, heating, and other equipment. It also meets the requirement that the total gamma specific activity of residual radionuclides is less than 5Bq / L.

[0007] In order to achieve the above technical effects, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a radionuclide composite decontaminant, comprising the following components: ammonium chloride, an oxidant, an alkaline agent, an organic acid, a cleaning agent, and a solvent.

[0009] In the present invention, multiple detergents are compounded and used, and the synergistic effect among ammonium chloride, an oxidant, an alkaline agent and an organic acid is utilized, so that the composite detergent can efficiently remove radioactive nuclides adsorbed on the measuring container.

[0010] It is worth noting that the ammonium chloride is used to enhance the complexing ability of metal ions, the oxidant is used to oxidize low-valent metal ions to high-valent states, the alkaline agent is used to adjust the pH of the composite detergent, and the organic acid is used to form a stable complex with the metal ions, and they play a synergistic role with each other; in addition, the composite detergent is alkaline as a whole because it contains a large amount of sodium hydroxide. After adding a small amount of organic acid, the pH change is very small, and it will not exist in the form of salt in the solution. At the same time, the organic acid radical generated by the organic acid is a ligand, which can form a stable water-soluble complex with the high-valent metal ions.

[0011] As a preferred technical solution of the present invention, the composite detergent comprises the following components in percentage by mass:

[0012]

[0013]

[0014] In the present invention, the mass percentage of ammonium chloride is 0.9%-1.1%, for example, it can be 0.92%, 0.94%, 0.96%, 0.98%, 1.0%, 1.02%, 1.04%, 1.06% or 1.08%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0015] It is worth noting that when the amount of ammonium chloride added is too little, the complexing ability with metal ions is insufficient, resulting in the inability to effectively remove radioactive nuclides. When the amount of ammonium chloride added is too much, the ammonium ions will continue to react with the formed complex, causing it to decompose, resulting in the inability to effectively remove radioactive nuclides.

[0016] In the present invention, the mass percentage of the oxidant is 0.5%-0.7%, for example, it can be 0.52%, 0.54%, 0.56%, 0.58%, 0.6%, 0.62%, 0.64%, 0.66% or 0.68%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0017] In the present invention, the mass percentage of the alkaline agent is 0.9%-1.1%, for example, it can be 0.92%, 0.94%, 0.96%, 0.98%, 1.0%, 1.02%, 1.04%, 1.06% or 1.08%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0018] In the present invention, the mass percentage of the organic acid is 0.1%-0.3%, for example, it can be 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.26% or 0.28%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0019] In the present invention, the mass percentage of the cleaning agent is 0.1%-0.3%, for example, it can be 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.26% or 0.28%, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0020] It is worth noting that when the amount of cleaning agent added is too small, the radioactive nuclides will be re-adsorbed on the wall of the device, resulting in a significant decrease in the radioactive nuclide removal performance of the composite detergent; when the amount of cleaning agent added is too much, it will compete with organic acid radicals for metal ions, causing some metal ions to precipitate, thereby reducing the radioactive nuclide removal performance of the composite detergent.

[0021] As a preferred technical solution of the present invention, the mass ratio of ammonium chloride, oxidant, alkaline agent and organic acid is 1:(0.55-0.65):(0.9-1):(0.15-0.25), for example, it can be 1:0.6:0.95:0.2, 1:0.65:1:0.1.5 or 1:0.55:0.95:0.25, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0022] It is worth noting that the present invention further controls the mass ratio of ammonium chloride, oxidant, alkaline agent and organic acid within a specific range, which is conducive to the efficient removal of radioactive nuclides.

[0023] As a preferred technical solution of the present invention, the oxidant includes potassium permanganate and / or sodium percarbonate, preferably potassium permanganate.

[0024] Preferably, the alkaline agent comprises sodium hydroxide and / or potassium hydroxide.

[0025] Preferably, the organic acid comprises any one of oxalic acid, ascorbic acid or ethylenediaminetetraacetic acid, or a combination of at least two thereof. Typical but non-limiting examples of the combination include: a combination of oxalic acid and ascorbic acid, a combination of ethylenediaminetetraacetic acid and ascorbic acid, or a combination of oxalic acid, ascorbic acid and ethylenediaminetetraacetic acid, etc., preferably oxalic acid.

[0026] As a preferred technical solution of the present invention, the cleaning agent includes any one of sodium gluconate, potassium tartrate or sodium citrate, or a combination of at least two of them. Typical but non-limiting examples of the combinations include: a combination of sodium gluconate and potassium tartrate, a combination of potassium tartrate and sodium citrate, or a combination of sodium gluconate, potassium tartrate and sodium citrate.

[0027] Preferably, the solvent comprises demineralized water and / or water.

[0028] In a second aspect, the present invention provides a method for using the composite detergent according to the first aspect, the method comprising the following steps:

[0029] (1) Clean the measuring container to be decontaminated with a solvent;

[0030] (2) Add the composite detergent into the measuring container to be decontaminated described in step (1) and let it stand.

[0031] The method for using the composite detergent provided by the present invention does not require ultrasonic cleaning, and can efficiently remove radioactive nuclides adsorbed on the measuring container by simply standing and soaking at room temperature.

[0032] As a preferred technical solution of the present invention, the material of the decontamination measuring container includes polypropylene.

[0033] Preferably, the number of cleaning times in step (1) is ≥ 3 times, for example, it can be 3 times, 4 times, 5 times or 6 times, but is not limited to the listed values. Other unlisted values within the numerical range are also applicable, preferably 3 times.

[0034] As a preferred technical solution of the present invention, the standing time in step (2) is 20-30 min, for example, it can be 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min or 29 min, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0035] It is worth noting that the method provided by the present invention is simple to operate and does not require equipment such as ultrasound and heating; and the decontamination is highly efficient, completing the removal of radioactive nuclides in a relatively short period of time.

[0036] Preferably, the standing temperature in step (2) is 10-40°C, for example, 15°C, 20°C, 25°C, 30°C, 35°C or 38°C, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0037] In the present invention, the volume of the composite detergent is determined according to the volume of the measuring container, so that the composite detergent completely soaks the measuring container without overflowing.

[0038] As a preferred technical solution of the present invention, step (2) further includes step (3):

[0039] (3) Recovering the composite detergent in step (2), and then cleaning the measuring container with a solvent.

[0040] In the present invention, the composite detergent can be reused and generates less waste liquid.

[0041] In a third aspect, the present invention provides a use of the composite decontaminant according to the first aspect, wherein the composite decontaminant is used for decontaminating a measuring container for liquid effluent from a nuclear power plant.

[0042] Preferably, the radioactive nuclides in the liquid effluent include any one of Ag-110m, Co-60 or Co-58, or a combination of at least two of them.

[0043] Preferably, the material of the measuring container includes polypropylene.

[0044] The numerical range described in the present invention includes not only the point values listed above, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The radioactive nuclide composite decontaminant provided by the present invention is prepared by using a plurality of decontaminants in combination, which act synergistically with each other and can efficiently remove radionuclides adsorbed on the measuring container at room temperature. The composite decontaminant is low in cost and can be reused.

[0047] (2) The method of use provided by the present invention is simple to operate, does not require ultrasound, heating and other equipment, and has high decontamination efficiency. The measuring container after decontamination meets the requirement that the total gamma specific activity of residual radionuclides is less than 5Bq / L. DETAILED DESCRIPTION

[0048] For the convenience of understanding the present invention, the present invention is given below with examples. It should be understood by those skilled in the art that the examples are only for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0049] Example 1

[0050] This embodiment provides a radionuclide composite decontaminant and a method for using the same. The composite decontaminant comprises the following components by mass percentage: 1% ammonium chloride, 0.6% potassium permanganate, 1% sodium hydroxide, 0.2% oxalic acid, 0.2% sodium gluconate, and the balance is deionized water.

[0051] The method of use comprises the following steps:

[0052] (1) Wash the measuring container to be decontaminated 3 times with deionized water;

[0053] The material of the decontamination measuring container is polypropylene, and the decontamination measuring container is a Marlin cup;

[0054] (2) Add 1 L of the composite detergent to the measuring container to be decontaminated described in step (1) and let it stand at 20° C. for 30 minutes;

[0055] (3) Recovering the composite detergent in step (2), and then washing the measuring container with deionized water.

[0056] Example 2

[0057] This embodiment provides a radionuclide composite decontaminant and a method for using the same. The composite decontaminant comprises the following components by mass percentage: 1.1% ammonium chloride, 0.65% potassium permanganate, 1% potassium hydroxide, 0.25% oxalic acid, 0.25% sodium gluconate, and the balance is deionized water.

[0058] The method of use comprises the following steps:

[0059] (1) Wash the measuring container to be decontaminated 3 times with deionized water;

[0060] The material of the decontamination measuring container is polypropylene, and the decontamination measuring container is a Marlin cup;

[0061] (2) adding 1.1 L of the composite detergent to the measuring container to be decontaminated described in step (1) and allowing to stand at 30° C. for 25 min;

[0062] (3) Recovering the composite detergent in step (2), and then washing the measuring container with deionized water.

[0063] Example 3

[0064] This embodiment provides a radionuclide composite decontaminant and a method for using the same. The composite decontaminant comprises the following components by mass percentage: 0.95% ammonium chloride, 0.6% sodium percarbonate, 0.95% sodium hydroxide, 0.20% oxalic acid, 0.20% sodium gluconate, and the balance water.

[0065] The method of use comprises the following steps:

[0066] (1) Wash the measuring container to be decontaminated 3 times with deionized water;

[0067] The material of the decontamination measuring container is polypropylene, and the decontamination measuring container is a Marlin cup;

[0068] (2) adding 1 L of the composite detergent to the measuring container to be decontaminated described in step (1) and allowing to stand at 15° C. for 30 min;

[0069] (3) Recovering the composite detergent in step (2), and then washing the measuring container with deionized water.

[0070] Example 4

[0071] This embodiment provides a radionuclide composite decontaminant and a method for using the same. The composite decontaminant comprises the following components by mass percentage: 1% ammonium chloride, 0.7% potassium permanganate, 1.1% sodium hydroxide, 0.2% oxalic acid, 0.2% sodium gluconate, and the remainder is deionized water. Other conditions are the same as those in Example 1.

[0072] Example 5

[0073] This embodiment provides a radionuclide composite decontaminant and a method for using the same. The composite decontaminant comprises the following components by mass percentage: 1% ammonium chloride, 0.5% potassium permanganate, 1.1% sodium hydroxide, 0.2% oxalic acid, 0.2% sodium gluconate, with the remainder being deionized water. Other conditions are the same as those in Example 1.

[0074] Example 6

[0075] This embodiment provides a radionuclide composite decontaminant and a method for using the same. Except that the mass percentage of ammonium chloride is 0.8%, other conditions are the same as those in Example 1.

[0076] Example 7

[0077] This embodiment provides a radionuclide composite decontaminant and a method for using the same. Except that the mass percentage of ammonium chloride is 1.3%, other conditions are the same as those in Example 1.

[0078] Example 8

[0079] This embodiment provides a radionuclide composite decontaminant and a method for using the same. Except that the mass percentage of potassium permanganate is 0.4%, other conditions are the same as those in Example 1.

[0080] Example 9

[0081] This embodiment provides a radionuclide composite decontaminant and a method for using the same. Except that the mass percentage of the sodium hydroxide is 0.8%, other conditions are the same as those in Example 1.

[0082] Example 10

[0083] This embodiment provides a radionuclide composite detergent and a method for using the same. Except that the mass percentage of sodium gluconate is 0.05%, other conditions are the same as those in Example 1.

[0084] Example 11

[0085] This embodiment provides a radionuclide composite detergent and a method for using the same. Except that the mass percentage of sodium gluconate is 0.4%, other conditions are the same as those in Example 1.

[0086] Example 12

[0087] This embodiment provides a radionuclide composite detergent and a method for using the same. Except that the standing time in step (2) is 15 minutes, other conditions are the same as those in Example 1.

[0088] Example 13

[0089] This embodiment provides a radionuclide composite decontaminant and a method for using the same. Except that the standing time in step (2) is 60 minutes, other conditions are the same as those in Example 1.

[0090] Example 14

[0091] This embodiment provides a radionuclide composite decontaminant and a method for using the same. Except for using the composite decontaminant recovered in step (3) for decontamination, other conditions are the same as those in Example 1.

[0092] Comparative Example 1

[0093] This comparative example provides a radionuclide composite decontaminant and a method for using the same. Except that the composite decontaminant does not contain ammonium chloride and the contents of other raw materials are increased accordingly according to the raw material ratio, other conditions are the same as those in Example 1.

[0094] Comparative Example 2

[0095] This comparative example provides a radionuclide composite detergent and a method for using the same. Except that the composite detergent does not contain sodium hydroxide and the contents of other raw materials are increased accordingly according to the raw material ratio, other conditions are the same as those in Example 1.

[0096] Comparative Example 3

[0097] This comparative example provides a radionuclide composite detergent and a method for using the same. Except that the composite detergent does not contain sodium gluconate and the contents of other raw materials are increased accordingly according to the raw material ratio, other conditions are the same as those in Example 1.

[0098] The total gamma specific activity of the radionuclides in the above examples and comparative examples is the sum of the specific activities of Ag-110m, Co-60, and Co-58. Data below the lower detection limit are counted according to the lower detection limit. The lower detection limits of Ag-110m, Co-60, and Co-58 are 0.7, 0.5, and 0.4 Bq / L, respectively.

[0099] Ten measurement containers contaminated by liquid effluents of different activities were selected. The material of the measurement containers was polypropylene. The total gamma specific activity (Bq / L) of adsorbed radionuclides was measured before and after rinsing with deionized water. The number of rinses was three. The test results of the total gamma specific activity of radionuclides in the measurement containers before and after rinsing are shown in Tables 1 and 2, respectively.

[0100] Table 1

[0101] serial number 1# 2# 3# 4# 5# 6# 7# 8# 9# 10# Ag-110m 134.5 45.6 11.2 152.4 10.5 5.2 325.4 22.4 3.5 5.7 Co-60 20.2 12.3 42.0 23.0 4.3 0.8 24.3 2.8 0.7 23.7 Co-58 11.4 6.4 10.0 1.5 7.6 1.0 42.2 1.6 0.4 5.9 Total 166.1 64.3 63.2 176.9 22.4 7.0 391.9 26.8 4.6 35.3

[0102] Table 2

[0103] serial number 1# 2# 3# 4# 5# 6# 7# 8# 9# 10# Ag-110m 132.7 42.3 11.7 112.4 11.2 4.2 311.1 21.1 3.1 5.7 Co-60 21.2 12.4 12.7 26.0 4.1 0.8 8.3 2.8 0.7 14.7 Co-58 10.3 2.3 5.9 1.7 2.3 0.4 12.2 1.4 0.5 5.4 Total 164.2 57.0 30.3 140.1 17.6 5.4 331.6 25.3 4.3 25.8

[0104] It can be seen from Tables 1 and 2 that the total gamma specific activity of the measuring container is slightly reduced after flushing with desalted water, but it is far from meeting the requirement that the total gamma specific activity of residual radionuclides is less than 5 Bq / L.

[0105] The test results of the total gamma specific activity of radionuclides in the measurement containers before and after decontamination in the above examples and comparative examples are shown in Table 3.

[0106] Table 3

[0107]

[0108]

[0109] The following points can be drawn from Table 3:

[0110] (1) The radionuclide composite decontaminants and methods of use provided in Examples 1-3 and Example 14 of the present invention can efficiently remove radionuclides adsorbed on the measuring container at room temperature, are reusable, and meet the requirement that the total gamma specific activity of residual radionuclides is less than 5 Bq / L;

[0111] (2) Based on Example 1 and Examples 4-5, it can be seen that when the mass ratio of the oxidant to the alkaline agent to the ammonium chloride and the organic acid is not within the preferred range, the synergistic effect between them is no longer within the optimal range, resulting in a decrease in the removal effect of the composite detergent;

[0112] (3) Based on Example 1 and Examples 6-11, it can be seen that the performance of the composite detergent obtained in Examples 6-11 is not as good as that in Example 1. This is because the present invention achieves a better radionuclide removal effect at a smaller amount through the synergistic effect between ammonium chloride, oxidant, alkaline agent and organic acid in a specific ratio. If the addition amount of any component is outside the scope of the present invention, the effect will be deteriorated.

[0113] (4) Based on Example 1 and Examples 12-13, it can be seen that when the static soaking time is too short, although the total gamma specific activity of the measuring container is reduced, it cannot meet the requirement that the total gamma specific activity of the residual radionuclides is less than 5 Bq / L; when the static soaking time is too long, it has little effect on the total gamma specific activity of the measuring container. When the static soaking time reaches 30 minutes, the total gamma specific activity of the measuring container can meet the requirement that the total gamma specific activity of the residual radionuclides is less than 5 Bq / L.

[0114] (5) Based on Example 1 and Comparative Examples 1-3, it can be seen that since the present invention is a composite detergent prepared by using specific components, the synergistic effect between the components is achieved. When the composite detergent lacks any component, its effect becomes worse.

[0115] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A radionuclide composite detergent, characterized in that: The composite detergent comprises the following components in percentage by mass: Ammonium chloride 0.9%-1.1% Oxidant 0.5%-0.7% Alkaline agent 0.9%-1.1% Organic acid 0.1%-0.3% Cleaning agent 0.1%-0.3% The balance is solvent; The oxidant includes potassium permanganate and / or sodium percarbonate; the alkaline agent includes sodium hydroxide and / or potassium hydroxide; the organic acid is oxalic acid; the cleaning agent is sodium gluconate; and the solvent includes deionized water and / or water.

2. The composite detergent according to claim 1, characterized in that The mass ratio of the ammonium chloride, the oxidant, the alkaline agent and the organic acid is 1:(0.55-0.65):(0.9-1):(0.15-0.25).

3. The composite detergent according to claim 1, characterized in that The oxidant is potassium permanganate.

4. A method for using the composite detergent according to any one of claims 1 to 3, characterized in that: The method of use comprises the following steps: (1) Use solvent to clean the measuring container to be decontaminated; (2) Add the composite detergent into the measuring container to be decontaminated described in step (1) and let it stand.

5. The method of use according to claim 4, characterized in that: The material of the decontamination measuring container includes polypropylene.

6. The method of use according to claim 4, characterized in that: The number of cleanings in step (1) is ≥ 3 times.

7. The method of use according to claim 4, characterized in that: The standing time in step (2) is 20-30 minutes.

8. The method of use according to claim 4, characterized in that: The standing temperature in step (2) is 10-40°C.

9. The method of use according to claim 4, characterized in that: Step (2) is followed by step (3): (3) Recovering the composite detergent in step (2), and then cleaning the measuring container with a solvent.

10. Use of the composite detergent according to any one of claims 1 to 3, characterized in that: The composite decontaminant is used for decontaminating a measuring container of liquid effluent in a nuclear power plant.

11. The use according to claim 10, characterized in that The radioactive nuclides in the liquid effluent include any one of Ag-110m, Co-60 or Co-58, or a combination of at least two of them.

12. The use according to claim 10, characterized in that The material of the measuring container includes polypropylene.

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