KR20220141009A - Sequential separation of tritium and radiocarbon - Google Patents

Abstract

According to the present invention, a separation method is to provide a time-efficient and economical method as it can sequentially collect two radionuclides from one sample. Unlike the prior art, radiocarbon is not collected when collecting tritium to increase analysis accuracy of tritium and radiocarbon and maximize a recovery rate.

Description

Sequential separation of tritium and radiocarbon {SEQUENTIAL SEPARATION OF TRITIUM AND RADIOCARBON}

The present invention relates to a method for rapidly and accurately sequentially separating tritium (H-3) and radiocarbon (C-14), which are radionuclides.

Tritium and radiocarbon generated from radioactive waste from nuclear power plants are radioactive isotopes (nuclides) with volatile characteristics, and their half-lives are 12.3 years and 5730 years, respectively, and are widely distributed in the vicinity. These radionuclides are mainly produced in nuclear power generation, spent nuclear fuel reprocessing, radioactive isotope production, and medical fields. management is required.

For the separation of tritium and radiocarbon, a method of separating HTO liquid and ¹⁴ CO ₂ gas using an oxidation reaction is generally used. As for the separation method of these nuclides, the high-temperature oxidation method in which tritium and radiocarbon are separated by oxidizing the sample at a temperature of 850 ° C using a combustion furnace and the chemical oxidation method in which the sample is chemically oxidized using an oxidizing agent and a distillation apparatus are mainly used.

The high-temperature oxidation method has the advantage of completely decomposing a solid sample with a complex sample medium in a high-temperature combustion furnace, but has a problem in that the furnace is expensive, its use is limited for liquid samples, and it is impossible to separate tritium and radiocarbon at the same time.

The chemical oxidation method has the advantage of being able to separate tritium and radiocarbon separately at a relatively low equipment cost. On the other hand, in the chemical oxidation method, when tritium is collected in an acidic solution, radiocarbon is also collected, making it difficult to quantitatively analyze tritium, and there is a problem in that the recovery rate of radiocarbon is low.

Republic of Korea Patent Publication No. 10-1305241 (2013.09.06)

An object of the present invention as devised to solve the above problems is to provide a time-efficient and economical separation method since two radionuclides can be simultaneously collected using a single distillation apparatus.

In addition, another object of the present invention is to provide a separation method that maximizes the recovery rate of two radionuclides while sequentially separating tritium and radiocarbon.

In the present invention, (S1) converting the pH of the sample solution containing at least one radionuclide of tritium and radiocarbon to basic;

(S2) separating the gas containing tritium by heating the basic sample solution;

(S3) converting the pH of the basic sample solution to acid; and

(S4) heating the acidic sample solution to separate a gas containing radiocarbon; provides a sequential separation method of tritium and radiocarbon comprising a.

The step (S1) may be a step of converting the sample solution into a basic sample solution by mixing a basic material and an oxidizing agent.

The step (S2) may further include a step of distilling the gas containing tritium to convert it into a liquid and collect it.

The method may further include a step of cooling the basic sample solution between the step (S2) and the step (S3).

The step (S3) may be a step of converting the pH of the basic sample solution to acidic by mixing an acidic material and an oxidizing agent in the basic sample solution.

The step (S4) may include; collecting a gas containing radiocarbon with a radiocarbon adsorbing organic solvent.

It may include; distilling and cooling the gas separated in step (S2) or step (S4) and measuring the concentration of radionuclides using a liquid scintillation counter.

The tritium may be in the form of tritium of ³ H ₂ O, and the radiocarbon may be in the form of ¹⁴ CO ₂ , ¹⁴ CH ₄ or ¹⁴ C ₂ H ₆ .

The basic material may include any one or more selected from the group consisting of sodium hydroxide, calcium hydroxide, ammonium hydroxide and ammonia.

The acidic material may include at least one selected from the group consisting of hydrochloric acid, nitric acid, and sulfuric acid.

The separation method according to the present invention is to provide a time-efficient and economical method since it is possible to simultaneously capture two radionuclides. Unlike the existing ones, radiocarbon is not collected when tritium is collected, so the recovery rate of tritium and radiocarbon can be maximized.

1 is a schematic diagram schematically showing an apparatus for separating tritium and radiocarbon according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail through embodiments or examples including the accompanying drawings. However, the following specific examples or examples are only a reference for describing the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Referring to FIG. 1, the sequential separation device for tritium and radiocarbon of the present invention includes: a sample solution in which a solid or liquid sample containing at least one radionuclide of tritium and radiocarbon is dissolved therein; a heating unit for heating the sample in the sample solution unit; a distillation unit connected to an upper portion of the sample solution unit and converting water vapor generated by the heating unit into water; a cooling unit that continuously circulates and cools water; a tritium collecting unit for collecting water containing tritium generated from the distillation unit; The radiocarbon gas generated in the heating unit passes through the distillation unit to include a radiocarbon collecting unit in which radiocarbon is collected.

The sample solution unit may store at least one radionuclide of tritium and radiocarbon therein. The sample solution may contain radionuclides together with a cleaning agent used for decontamination or cleaning of contaminated equipment in nuclear facilities. At this time, in the case of tritium in the form of ³ H ₂ O triple water, in the case of radiocarbon, it may be dissolved in the sample solution in the form of ¹⁴ CO ₂ , ¹⁴ CH ₄ or ¹⁴ C ₂ H ₆ .

The sample solution part is heated by a heating part to sequentially separate the two nuclides. Specifically, the sample solution is first basified, then heated and distilled to separate tritium. Thereafter, after the sample solution is acidified, the radiocarbon is separated by heating and distillation. The sample solution unit may be a transparent container in which the inside can be observed from the outside. The sample solution unit may be provided to be spaced apart from the heating unit.

The sample solution unit may be connected to a reagent supply unit. The reagent supply unit supplies a basic material, an acidic material, an oxidizing agent, and the like to the sample solution unit. The reagent supply unit may control the pH of the sample solution supplied in the receiving unit to a predetermined value by adding an appropriate amount of a basic material, an acidic material, an oxidizing agent, or the like.

The sample solution unit may be connected to a gas supply unit. The gas supply unit injects gas so that the gas generated from the heating unit can move to the distillation unit. At this time, the gas used may be an inert gas such as nitrogen, helium, neon, or argon, but is not limited thereto.

The heating unit may heat the sample in the sample solution unit to a predetermined temperature, and in this case, the heating temperature may be sequentially heated over multiple steps. The temperature at which the separation unit is heated through the heating unit may be 50° C. to 250° C. The heating part may heat the lower part of the sample solution part, or it may be provided in a shape surrounding the sample solution part so that it can be heated with high efficiency.

As the sample solution is heated by the heating unit in the distillation unit, a gas containing radionuclides is evaporated, and the evaporated gas is cooled by a temperature difference in the distillation unit and converted into a liquid. The distillation unit may be a transparent container, so that condensation and movement of the vaporized gas sample can be visually observed even from the outside. For example, it can be observed that vapor phase condensation occurs in the form of mist inside the distillation unit, and when this phenomenon is stopped, it can be seen that the distillation is completed.

The cooling unit serves to continuously circulate water inside or outside the distillation unit to maintain a constant temperature of the distillation unit.

The tritium collecting unit collects water components including tritium by condensing water vapor containing tritium through a cooling unit and converting it into a liquid form through heating and distillation from the basic sample solution through the distillation unit. The tritium is collected in a liquid state in the tritium collecting unit because the gas generated in the heating unit in the cooling unit contacts the surface of the cold distillation unit through which water is circulated, and is condensed by a temperature difference.

The radiocarbon collecting unit is to collect gaseous radiocarbon generated by heating the heating unit from the acidic sample solution using a radiocarbon collecting body. In the radiocarbon collecting unit, radiocarbon gas may be collected in the form of ¹⁴ CO ₂ , ¹⁴ CH ₄ or ¹⁴ C ₂ H ₆ , and if an organic solvent (Carbo-Sorb) that selectively adsorbs only radiocarbon is used, radioactive carbon It can be separated from radioactive iodine and tritium with similar volatility.

The cooling unit cools the gas evaporated in the distillation unit. The cooling unit may indirectly cool the evaporation liquid using a refrigerant. That is, the cooling unit may lower the temperature of the distillate by using the refrigerant. However, the cooling unit is not limited thereto, and the cooling means capable of lowering the vaporization gas temperature may be applied to the cooling unit through which the water is circulated.

As such, the sequential separation device for tritium and radiocarbon according to an aspect of the present invention heats a sample solution including a sample containing a radionuclide such as tritium or radiocarbon, but the pH of the sample solution under acidic or basic conditions It is possible to increase the recovery rate of tritium or radiocarbon and sequentially separate radionuclides from one sample by controlling the

One aspect of the present invention provides a method for sequential separation of tritium and radiocarbon.

Specifically, (S1) converting the pH of the sample solution containing at least one radionuclide of tritium and radiocarbon to basic;

(S2) separating the gas containing tritium by heating the basic sample solution;

(S3) converting the pH of the basic sample solution to acid; and

(S4) heating the acidic sample solution to separate the gas containing radiocarbon; to provide.

Conventionally, tritium and radiocarbon were separated under an acidic solution. However, in this case, a small amount of radiocarbon is also collected when tritium is collected, so it is difficult to quantitatively analyze tritium, and there is a problem in that the recovery rate of radiocarbon is low.

On the other hand, in the sequential separation method of tritium and radiocarbon according to an aspect of the present invention, only tritium is first collected by basifying the sample solution. After cooling the remaining sample solution, it is acidified to collect radiocarbon. Accordingly, high-purity tritium is collected except for radiocarbon whose volatility is suppressed in a basic solution, and radiocarbon is sequentially collected in an acidic solution, thereby simplifying the analysis operation and providing a high recovery rate. In addition, it is possible to improve the accuracy of tritium analysis as well as increase the recovery rate of radiocarbon by reducing side reactions in which radiocarbon is simultaneously captured during tritium collection.

Hereinafter, a detailed look.

First, the pH of the sample solution containing at least one radionuclide of tritium and radiocarbon is converted to basicity. At this time, the pH may be, for example, 7.5 to 11. Specifically, the sample solution is basified by mixing a basic material and an oxidizing agent with the sample solution. At this time, the basic material may include any one or more selected from the group consisting of sodium hydroxide, calcium hydroxide, ammonium hydroxide and ammonia.

Thereafter, the basic sample solution is heated to separate a gas containing tritium. Specifically, by heating the sample solution section through the heating section, the gas containing tritium is distilled from the basic sample solution to be converted into a liquid and collected.

After the basic sample solution is heated through a heating unit, a gas containing tritium is separated, and the separated gas containing tritium may be cooled through a cooling unit and collected in a liquid state.

Next, after cooling the basic sample solution from which tritium has been removed, the pH of the sample solution is converted to acid. At this time, the pH may be, for example, 1.0 to 3.0. Specifically, it is a step of converting the pH of the basic sample solution to acid by mixing an acidic material and an oxidizing agent in the basic sample solution. In this case, the acidic material may include any one or more selected from the group consisting of hydrochloric acid, nitric acid, and sulfuric acid.

Thereafter, the acidic sample solution is heated to separate a gas containing radiocarbon. Specifically, the gas containing the radiocarbon is to be collected with an organic solvent that selectively adsorbs the radiocarbon. At this time, the organic solvent for selectively adsorbing radiocarbon may be, for example, carbo-sorb.

In a specific embodiment of the present invention, the final concentration of tritium or radiocarbon using a liquid scintillation counter (LSC, Liquid Scintillation Counter) by cooling the gas separated in step (S2) or step (S4) after distillation. can be measured. Specifically, a predetermined amount of the sample collected in the tritium collecting unit and the radiocarbon collecting unit may be collected, and then the tritium concentration and the radiocarbon concentration may be analyzed using a liquid scintillation counter.

At this time, the tritium may be in the form of tritium of ³ H ₂ O, and the radiocarbon may be in the form of ¹⁴ CO ₂ , ¹⁴ CH ₄ or ¹⁴ C ₂ H ₆ .

Example

Since the present invention may have various changes and may have various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. In addition, the unit of additives not specifically described in the specification may be weight %.

[Example]

Separation of tritium .

First, 100 g of a water sample was placed in a two-neck round-bottom flask, and 200 mg of potassium permanganate (KMnO ₄ ) was added to the round-bottom flask containing the sample. After adding granular NaOH 2-3 pieces (~500 mg) to the sample and stirring, the flask containing the sample was connected to a distillation apparatus. The sample was heated and distilled through a heating unit, and the temperature was adjusted to 60 °C. Discard 10 mL of the initially distilled sample, and then turn off the heating unit when 10 mL of the distilled sample is collected. A 10 mL sample was taken and placed in a liquid scintillation counting container and the sample volume was recorded. 10 mL of liquid scintillation cocktail (Uitima Gold LLT) was added to the liquid scintillation counting vessel and stirred. At this time, the surface of the sample container was well wiped with an antistatic tissue containing alcohol to prevent external contamination and static electricity. Tritium radioactivity was measured with a liquid scintillation counter.

radiocarbon separation

After the tritium collection was completed, the sample was cooled at room temperature for about one hour, the flask inlet stopper was opened, and 5.0 g of potassium permanganate, 2 mL of 1M silver nitrate, and 25 mL of concentrated nitric acid were added. Turn on the cooling unit (water cooler/circulator (condenser)), and turn on the heating mantle (heating mantle) to heat distillation. The temperature was adjusted to 60 °C and heated for 90 minutes, then the fitting mantle was turned off and left to cool for about 30 minutes. Record the distillation start and end times. The water cooler/circulator is kept constant. 5mL of Carbo-Sorb carbon trapping solution was transferred to a glass liquid scintillation counting container, and the trap tube was washed with 5mL of CarboSorb and placed in a liquid scintillation counting container. After adding 10 mL of liquid scintillation cocktail (Permafluor) to the liquid scintillation counting container and stirring, the radiocarbon activity was measured with a liquid scintillation counter.

[Comparative example]

Separation of tritium .

First, take 100 g of a water sample, put it in a two-neck round-bottom flask, add 5.0 g of potassium permanganate, 2 mL of 1M silver nitrate, and 25 mL of concentrated nitric acid to the round-bottom flask containing the sample and stir, and then distill the flask containing the sample. connected to the device. The sample was heated and distilled through a heating unit, and the temperature was adjusted to 60 °C. Discard 10 mL of the initially distilled sample, and then turn off the heating unit when 10 mL of the distilled sample is collected. A 10 mL sample was taken and placed in a liquid scintillation counting container and the sample volume was recorded. 10 mL of liquid scintillation cocktail (Uitima Gold LLT) was added to the liquid scintillation counting vessel and stirred. At this time, the surface of the sample container was well wiped with an antistatic tissue containing alcohol to prevent external contamination and static electricity. Tritium radioactivity was measured with a liquid scintillation counter.

radiocarbon separation

After the tritium was collected, the sample was cooled at room temperature for about an hour, and then a cooling unit (water cooler/circulator (condenser)) was turned on, and a heating mantle was turned on to heat distillation. The temperature was adjusted to 60 °C and heated for 90 minutes, then the fitting mantle was turned off and left to cool for about 30 minutes. Record the distillation start and end times. The water cooler/circulator is kept constant. 5mL of Carbo-Sorb carbon trapping solution was transferred to a glass liquid scintillation counting container, and the trap tube was washed with 5mL of CarboSorb and placed in a liquid scintillation counting container. After adding 10 mL of liquid scintillation cocktail (Permafluor) to the liquid scintillation counting container and stirring, the radiocarbon activity was measured with a liquid scintillation counter.

[Experimental example]

In order to find out the separation performance of the nuclide for the nuclide separation method devised in the present invention, the average and standard deviation of the recovery rate by using the tritium and radiocarbon certified standard materials provided by the Korea Research Institute of Standards and Science for the above Examples and Comparative Examples three times repeatedly is shown in Table 1 below.

division comparative example Example Tritium recovery (%) 95.2 ± 5.3 92.5 ± 5.4 Radiocarbon recovery (%) 78.8 ± 6.7 95.1 ± 4.8

When separated as in Comparative Example, the recovery rate of tritium was measured to be 95% or more, but the recovery rate of radiocarbon was measured to be 80% or less. In the case of the existing method, when tritium was captured in an acidic medium, a portion of highly volatile radiocarbon was also dissolved in water vapor in a gaseous state and collected together with tritium, which resulted in an increase and decrease in tritium and radiocarbon recovery rates. As a result of using the tritium and radiocarbon sequential separation method presented in the present invention, the recovery rate for tritium and radiocarbon is 90% or more, and the standard deviation is also calculated to be within 5%, thereby securing reliability and accuracy for tritium and radiocarbon analysis. Could.

The tritium and radiocarbon sequential separation method presented in the present invention can be usefully used as a tool to quickly and accurately evaluate the content of tritium and radiocarbon in a radioactive waste sample compared to the existing tritium and radiocarbon individual and simultaneous analysis methods. it can be seen that

The present invention described above is merely exemplary, and those of ordinary skill in the art to which the present invention pertains will appreciate that various modifications and equivalent other embodiments are possible therefrom. Therefore, it will be well understood that the present invention is not limited to the forms recited in the above detailed description. Therefore, the true technical protection scope of the present invention should be defined by the technical spirit of the appended claims.

Claims (10)

(S1) converting the pH of the sample solution containing at least one radionuclide of tritium and radiocarbon to basic;
(S2) separating the gas containing tritium by heating the basic sample solution;
(S3) converting the pH of the basic sample solution to acid; and
(S4) separating the gas containing radiocarbon by heating the acidic sample solution; tritium and radiocarbon sequential separation method comprising a. According to claim 1,
The step (S1) is a step of converting the sample solution into a basic sample solution by mixing a basic material and an oxidizing agent; the sequential separation method of tritium and radiocarbon. According to claim 1,
The step (S2) is, after distilling the gas containing tritium, converting it into a liquid to collect tritium; the sequential separation method of tritium and radiocarbon further comprising. According to claim 1,
The sequential separation method of tritium and radiocarbon further comprising; cooling the basic sample solution between the (S2) step and the (S3) step. According to claim 1,
The step (S3) is a step of converting the pH of the basic sample solution to acidic by mixing an acidic material and an oxidizing agent in the basic sample solution; the sequential separation method of tritium and radiocarbon. According to claim 1,
The (S4) step is a sequential separation method of tritium and radial carbon comprising a; collecting a gas containing radiocarbon with a radiocarbon adsorbing organic solvent. According to claim 1,
Distilling and cooling the gas separated in step (S2) or step (S4) to measure the concentration of radionuclides using a liquid scintillation counter; According to claim 1,
The tritium is a tritium form of ³ H ₂ O, and the radiocarbon is ¹⁴ CO ₂ , ¹⁴ CH ₄ or ¹⁴ C ₂ H ₆ A sequential separation method of tritium and radiocarbon that is in the form of. According to claim 1,
The basic material is a sequential separation method of tritium and radiocarbon comprising at least one selected from the group consisting of sodium hydroxide, calcium hydroxide, ammonium hydroxide and ammonia. According to claim 1,
The acidic material is a sequential separation method of tritium and radiocarbon comprising at least one selected from the group consisting of hydrochloric acid, nitric acid, and sulfuric acid.

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