KR101173176B1 - A Apparatus for the Selective Separation of Iodine in Aqueous Sample - Google Patents

Abstract

PURPOSE: An apparatus for selectively separating nonvolatile iodine from aqueous sample is provided to prevent radioactive contamination by installing a partition in a sub trap. CONSTITUTION: A heating mantle(104) is installed on the outer surface of a reaction bath(102). Iodine ions are oxidized from nonvolatile iodine containing solutions to nonvolatile iodine by oxidizers in the reaction bath. The nonvolatile iodine containing solutions are heated by the heating mantle. The oxidizer is hydrogen peroxide. A main collecting bath(122) is connected to the reaction bath using a transmission tube.

Description

A Apparatus for the Selective Separation of Iodine in Aqueous Sample}

The present invention relates to a device for capturing volatile iodine present in an aqueous solution in a nonpolar organic solvent by distillation to separate iodine in high yield without interference of other elements. More particularly, the present invention relates to an apparatus for selectively separating volatile iodine by trapping volatile iodine by a distillation method in a nonpolar organic solvent without interference of other elements.

The recent explosion of the nuclear power plant caused by the Great East Japan Earthquake has caused serious pollution to groundwater and seawater, as well as to animals and plants, as well as environmental leakage of iodine (I), including radioactive cesium (Cs). As such, iodine may cause thyroid cancer in mammalian animals or destroy skin layers by destroying the ozone layer. In addition to environmental leaks caused by serious accidents in nuclear reactors, iodine is also known to be released during the peaceful commercial development of nuclear reactors. Nuclear iodine produced during the combustion of nuclear fuel swells the fuel and migrates between the fuel and the cladding to damage the fuel cladding. Or lower thermal conductivity can significantly affect fuel life and reactor operation. In addition, rupture of the fuel cladding may lead to the release of fission products, especially ¹²⁹ I (1.7 × 10 ⁷ years), which is highly volatile and has a very long half-life, thus identifying iodine formation behavior and chemical species during the combustion of fuel. Numerous studies have been conducted on the removal of ¹²⁹ I from the waste fuel reprocessing process waste.

Therefore, the quantitative analysis of iodine in radioactive material is essential for the study of the iodine removal process in radioactive waste in reprocessing process as well as the chemical characterization of spent fuel. In addition, in relation to the disposal of radioactive wastes, regulations for selecting radionuclides such as α? Β emitting nuclides, which are difficult to measure by radioactive and biological toxicity, half-life of nuclear species, and non-destructive methods, have been established and tightened. In Korea, research is conducted on the selection of target nuclear species that are expected to be regulated in relation to the transport and disposal of radioactive waste discharged from nuclear power plants and other nuclear facilities in various forms. have. In particular, among the few elements that are expected to be regulatory nuclei, ¹²⁹ I is strictly regulated by setting a very low lower limit of the incoming concentration of radioactive waste storage.

Recently, various radioactive wastes are emitted from nuclear facilities and industries using nuclear and isotope. In addition to spent fuel in nuclear power plants, non-metals such as iron, concentrated waste, sludge, cooling water, glass, waste filters, and workers' work clothes, gloves and disposables such as disposable gloves are being discharged. In this case, various types of radioactive waste such as syringes, gowns, surgical gloves, patient masks, and biological samples are generated. Except for a few of these samples, most of them contain trace amounts of iodine, especially in the case of ¹²⁹ I, which has a very low specific radioactivity, making it difficult to measure directly. Therefore, in order to be able to directly measure the iodine contained in these wastes, it is necessary to separate and concentrate the iodine contained in the sample to remove the disturbing elements and to form a concentration above the measurement limit.

In order to be able to measure iodine by separating the sample, the pretreatment method should be selected according to the type of sample.

The amount of ¹²⁹ I contained in environmental samples or radioactive waste is estimated to be extremely small. To quantify these, a large amount of samples are taken to separate the iodine from the medium and the solution to recover iodine such as leaching, adsorption, and decomposition. A chemical separation process to recover and a measurement process for measurement of trace amounts of iodine are necessary. In particular, radioactive waste contains a number of fission products that can affect the measurement of nuclear material or other ¹²⁹ I, and radiation shielding facilities and the spread of radioactive waste that can selectively separate and recover iodine from these elements. The pretreatment of the sample should be carried out in a confined space where it can be suppressed.

As a pretreatment method of a sample for separating and recovering iodine from radioactive samples emitted from an industrial or nuclear power plant, it is dissolved using a mixed acid, and then chemically separated from oxidized iodine during dissolution. Alkali melting method to add and melt, ion exchange resin separation method to separate ionic I ^- from an liquefied sample using anion exchange resin, and activated carbon adsorption elution method to elute gaseous iodine with acid adsorbed on activated carbon The sample preparation method of the method can be used.

In the case of solid environmental samples such as soil, soil, and biological samples, the gas discharged while burning at a high temperature of 1,000 ° C. is passed through the activated carbon layer to adsorb iodine, and then eluted with dilute NaOH solution to reduce and oxidize iodine in the solution. The method of measuring after chemical separation is known. In the case of soluble samples, the most widely used method can be selected by separation of the acid, but volatile iodine loss may occur during the decomposition of the sample. Except for some kinds of radioactive waste discharged from nuclear power plants, iodine is eluted by leaching rather than acid dissolving as a poorly soluble and insoluble sample. Or it melt | dissolves in an alkaline atmosphere of comparatively low temperature (about 450 degreeC), and re-dissolves and uses it. ¹²⁹ I-rule KOH and KI contained in the waste paper among radioactive wastes were added to alkali melt at 450 ℃, and then dissolved with dilute acid to separate iodine, and then MgI ₂ Precipitates can be formed and separated by neutron emission analysis.

Samples in solution contain many ionic elements that can affect iodine measurements. In the case of separating the nuclides of iodine contained in the concentrated waste liquid of the reactor coolant system or in aqueous solutions such as natural water and seawater, various types of anions and high concentrations of boron are included in the sample. do. The anion exchange resin is separated by changing the concentration of the eluent after adsorbing for more than 12 hours by using the difference in the affinity of the ionic iodine to the resin. That is, the anion exchange column (AG1x4, chlorine type) eluting the sample to IO ₃ ^- separated iodine by elution by reduction of a chemical ^species by passing the KHSO ₃ solution, disconnect the IO ₃ ^{- -} I from or organic iodine to I Is possible.

A soluble pre-treatment of the sample The method of measuring the concentration of iodine is contained in the metal in the oxidation resistance of silver nitrate samples are frequently used in the decomposition of the sample I ^- since the oxidized with I ₂ during the decomposition process, the volatile dissolution method according to the general acid Not suitable D. Geithoff and V. Schneider of the Karlsruhe Institute, Germany, reported that the rate of oxidation of I ₂ to IO ₃ ^- is very slow compared to the rate of oxidation of I ^- to I ₂ in the study of iodine behavior in nitric acid media. ₂ is volatilized, making it difficult to quantitatively recover iodine. Nitrosyl chloride, which is formed from a mixed acid of more oxidizing nitric acid and hydrochloric acid, rapidly oxidizes I ₂ to IO ₃ ^- to quantitatively isolate and recover iodine. I presented a way to do it. On the other hand, hydrogen peroxide is added to sulfuric acid, a non-volatile acid, to oxidize I ^- to I ₂ for separation of iodine contained in radioactive metals, and then distilled and collected in 2M NaOH, followed by distillation after acid dissolution to recover iodine quantitatively. There is a way.

In general, depending on the type of medium used to decompose iodine in the sample, the type of oxidizing agent and reducing agent, and the recovery and measuring methods are different. Iodine contained in nuclear fuel can be separated by oxidation of I ^- to IO ₃ ^- using KMnO ₄ and KCrO ₄ in acidic media.In case of alkaline media that has undergone alkali melting for dissolution of the sample, NaClO _The method of separating and recovering by column elution after oxidation with ₃ ^- is applied.

Radioactive waste contains various kinds of interfering elements and fissile nuclides, which requires selective separation. In particular, most samples, including industrial wastes except some high-burning spent fuels and radioactive waste resins, contain trace amounts of iodine, so the choice of sample pretreatment is very important. Among various pretreatment methods, distillation has the advantage of selectively separating and recovering only the elements to be quantified by using volatile iodine.

The iodine separation method by distillation is carried out by leaching a large amount of the sample with acid to separate the iodine contained in the radioactive collectible sample, and then distilling the iodine in the leachate at low temperature and collecting it in alkaline solution. It is a method that can be selected to lower the minimum detection detection limit and increase the recovery rate.

¹²⁹ I has low energy (0.15 MeV) β particle emission and specific radioactivity (6.4 Bq / μm), and γ-ray (0.0039 MeV) and X-ray (0.029 MeV) are also very low and difficult to measure directly. The method of sample pretreatment requires selective isolation of ¹²⁹ I from the interfering element to lower the measurement limit. The measurement method of ¹²⁹ I using the liquid scintillation counter (LSC) and γ-ray spectrometry is inexpensive and simple to handle, but the measurement limit after sample preparation is as high as 20 mBq. The neutron activation analysis (NAA), which is widely used for the measurement of ¹²⁹ I in environmental samples, has a very low meas- urement limit of 1 μBq but requires a large neutron irradiation facility.

Accelerator mass spectrometry and inductively coupled plasma mass spectrometry, which have recently been the subject of interest for the measurement method of ¹²⁹ I, also have very low measurement limits, but require expensive equipment and skill. do. In the case of iodine containing trace amounts in environmental samples such as soil or rock, iodine is recovered through various separation processes, and then neutron radiation is applied to the radioactive analysis method, and in particular, the trace concentration can be measured. However, although there are advantages of low measurement limits, there is a problem that the iodine separation process is very complicated and a neutron irradiation facility is required.

¹²⁹ I contained in radioactive waste has a very long half-life (1.57 x 10 ⁷ years) and should be carried out in a restricted area equipped with radiation shielding to prevent the mass production or spread of contamination in handling. The iodine distillation method for the separation and recovery of radioactive iodine has an advantage of good recovery rate and selective distillation of only volatile iodine, thereby not being affected by interferences. However, two or more collecting tubes of the distillation apparatus should be installed, and the collecting liquid may be thrown out by the bumping of the carrier gas collected by each collecting tube, which may cause an error in the analysis result. In addition, the iodine recovery extraction process for two or more collecting pipes not only produce a large amount of waste, but also increase the working process, causing errors in the analysis results, and thus requires more work time.

SUMMARY OF THE INVENTION An object of the present invention for solving the above problems is to provide a selective separation device of volatile iodine in an aqueous solution which collects volatile iodine contained in an aqueous solution in a nonpolar organic solvent by distillation to separate iodine in high yield without interference of other elements. There is.

In the selective separation device of volatile iodine in the aqueous solution of the present invention for achieving the above object, a heating mantle is provided on the outer circumferential surface, and oxidized iodine ions to volatile iodine by oxidant from a volatile iodine-containing solution heated by the heating mantle. A reaction tank in which an oxidation reaction occurs; And a volatile iodine is supplied through the delivery pipe by a carrier gas supplied from a carrier gas supply pipe installed in the reactor, and is connected to the reactor by a non-polar organic solvent filled therein. It contains the main collection tank from which iodine is separated.

The oxidizing agent is characterized in that hydrogen peroxide.

In addition, the outer peripheral surface of the delivery pipe is characterized in that the delivery pipe heater is installed.

In addition, the main collection tank is connected to the secondary collecting pipe which can be discharged gas, the auxiliary collecting pipe is formed in the bent portion bent in a U-shape, the bent portion is characterized in that the non-polar organic solvent is charged.

In addition, a buffer tank is integrally formed at the end of the auxiliary collecting pipe, and a diaphragm is disposed in the buffer tank to prevent the flow of gas.

In addition, the nonpolar organic solvent is characterized in that sulfuric acid.

According to the selective separation device of volatile iodine in the aqueous solution of the present invention described above, by unifying the conventional two-stage collection trap in one step, to minimize the work space, and to reduce the work time for verifying the recovery rate of the iodine to be separated It is possible to improve the recovery rate of iodine to 90% or more. In addition, when collecting iodine using an organic solvent, compared with the case of using a conventional NaOH trap, the correction step by the incorporation of water vapor can be omitted, and directly collected in the organic solvent, without the addition of a reducing agent Back extraction is possible.

In addition, the selective separation device of the volatile iodine in the aqueous solution of the present invention by installing a diaphragm in the auxiliary trap to prevent the test solution from splashing out by bumping when air bubbles are absorbed into the trapping solution to suppress the diffusion of radioactive material contamination Have

1 is a schematic diagram of a selective separation apparatus of volatile iodine according to an embodiment of the present invention.
2 is a graph showing the recovery rate of iodine according to the concentration of hydrogen peroxide in the selective separation device of volatile iodine of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention.

In FIG. 1, reference numeral 100 denotes an apparatus for selectively separating volatile iodine according to an embodiment of the present invention. The selective separation device 100 for volatile iodine is largely a reaction tank 102 for oxidizing and vaporizing iodine ions in an aqueous solution, and a main collection tank 122 for collecting iodine primarily from a gas vaporized from the reaction tank 102. And an auxiliary collecting pipe 132 for collecting iodine secondary from the gas discharged from the main collecting tank 122.

The reaction tank 102 has a space for storing the aqueous solution therein, the thermometer holder 106 to install the thermometer 108 to the upper side, and the injection gas injection pipe 112 for supplying the carrier gas is installed The tube holder 110 and one end of the delivery pipe 118 through which the iodine vaporized moves is installed. In addition, a heating mantle 104 is provided on the outer circumferential surface of the reaction tank 102 to heat the aqueous solution inside the reaction tank 102.

The thermometer 108 serves to measure the temperature of the aqueous solution, and since the heating temperature of the aqueous solution is 90 to 97 ° C., an alcohol thermometer, a mercury thermometer, a resistance thermometer, etc., capable of measuring the temperature in this temperature range are known. Thermometers can be used.

The carrier gas injection pipe 112 is connected by a carrier gas supply source (not shown) and a carrier gas supply pipe 114, and the carrier gas may be argon (Ar) which is an inert gas.

The heating mantle 104 may use an electric heater using a resistance, and surrounds the outer circumferential surface of the reaction tank 102 to favor the heat transfer. The heating mantle 104 may be used to heat the aqueous solution in the range of 90 to 97 ° C., check the temperature of the aqueous solution by the thermometer 108, and control the heat supply by the heating mantle 104.

The vaporized iodine I ₂ is moved through the delivery pipe 118 installed in the delivery pipe holder 116. In the vaporization of the iodine, iodine ions (I ⁻ ) are oxidized to volatile iodine (I ₂ ) by hydrogen peroxide H ₂ O ₂ ) contained in the aqueous solution.

One end of the delivery pipe 118 is fixed to the delivery pipe holder 116 of the reactor 102, and the other end of the insertion pipe 126 is connected to the main collection tank 122. In particular, the insertion portion 126 is extended to the inner space of the main collection tank 122, one end of the secondary collection pipe 132 to be described below is disposed lower than the position where the main collection tank 122 is connected. . The transfer pipe 118 is provided with a heat pipe heater 120 to prevent the volatilized iodine moved by the carrier gas due to the temperature decrease during the movement is cooled and fixed to the inner wall surface of the transfer pipe 118. The heat pipe heater 120 is installed on the entire outer circumferential surface of the transfer pipe 118. As the heat pipe heater 120, an electric resistance heater or a planar heating element may be used. Moreover, it is also possible to wind and install the planar heating element of the tape form to the said 1st transmission pipe 118.

In addition, by checking the temperature inside the delivery pipe 118, and measuring the temperature of the gas passing through the delivery pipe 118, it is preferable to adjust the amount of heat generated by the heat pipe heater 120 through this information. Do. Therefore, the temperature sensor 140 is installed in the delivery pipe 118. A known thermocouple may be used as the temperature sensor 140.

The main collection tank 122 has a space having a larger cross-sectional area than the insertion portion 126 of the delivery pipe 118, the discharge portion 128 is provided with a discharge valve 130 is installed below the main collection tank 122 do. In addition, a nonpolar organic solvent is charged in the main collection tank 122 so that the insertion part 126 is locked. The non-polar organic solvent may be used as a solvent 7 ~ 9 M sulfuric acid (H ₂ SO ₄ ) solution. Therefore, after the gas flowing through the delivery pipe 118 is supplied to the main collection tank 122, iodine in the gas is separated from the upper layer of the non-polar organic solvent.

In addition, the main collection tank 122 is connected to the auxiliary collection pipe 132. The auxiliary collecting pipe 132 has a bent portion of the approximately U-shape, the bent portion is installed lower than one end of the auxiliary collecting pipe 132 connected to the main collecting tank 122, the auxiliary collecting pipe 132 The other end of is disposed higher than the one end.

A non-polar organic solvent is charged into the main collecting tank 122 and the bent portion of the auxiliary collecting tube 132. The non-polar organic solvent may be used as a solvent 7 ~ 9 M sulfuric acid (H ₂ SO ₄ ) solution. Therefore, iodine contained in the gas not separated from the main collection tank 122 may be dissolved in the non-polar organic solvent and separated from the bent portion of the auxiliary collection pipe 132.

The other end of the auxiliary collecting pipe 132 is provided with a buffer 134, the buffer 134 is to reduce the moving speed of the gas passing through the auxiliary collecting pipe 132, the auxiliary collecting pipe ( It is formed to have a large cross-sectional area compared to the cross-sectional area of 132). The diaphragm 136 may be disposed in the buffer 134 to prevent the movement of gas, and an exhaust pipe 138 may be disposed above the buffer 134 to discharge the gas.

The diaphragm 136 has an inclined plate shape to prevent the flow of gas passing through the auxiliary collecting pipe 132. Therefore, the gas passing through the auxiliary collecting pipe 132 is disturbed by the flow of the diaphragm 136, to prevent the scattering of the organic solvent by the bubbles, it is possible to suppress the diffusion of contamination of the radioactive material.

The selective separation device 100 of volatile iodine according to the embodiment of the present invention is basically configured as described above. Hereinafter, an experimental example of recovering iodine by preparing an aqueous solution containing volatile iodine using the present invention will be described.

[Test Example]

Boric acid and potassium iodine (KI) contained in the matrix were used as a sample, and ¹²⁹ I was used as a tracer.

Ionic iodine (I ⁻ ) present in the prepared iodine sample solution containing sulfuric acid was oxidized to volatile iodine (I ₂ ) using hydrogen peroxide (H ₂ O ₂ ). At this time, the amount of oxidant was found to be suitable for 32% H ₂ O ₂ 0.7%. At this time, when the amount of the oxidant is small or exceeded, as shown in FIG. 2, it was found that the recovery rate of volatile iodine is rather reduced.

In order to transport the volatile iodine formed in the reactor to the delivery pipe 118, argon (Ar) gas was used as a carrier gas, and the argon gas was flowed through the carrier gas supply pipe 112 at a rate of 2 ml / min. Heated while feeding. The temperature of the reaction tank 102 is preferably distilled by heating to a temperature range of 90 ~ 97 ℃ as water does not boil. The time required for distillation was 4-5 hours with 500 ml of 9 M sulfuric acid medium which is a nonpolar organic solvent.

As described above, the volatile iodine is collected in the non-polar organic solvent present in the main collection tank 122 and the auxiliary collection tube 132 by heating and distilling the reactant. Unlike the conventional method using NaOH, the present separator has the advantage that the water vapor contained in the carrier gas flowing in is separated from the upper layer of the organic solvent. Volatile iodine not absorbed by the main collection tank 122 is absorbed again while passing through the organic solvent contained in the auxiliary collection pipe 132. By the process according to the invention volatile iodine was recovered with a recovery of at least 90%.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications or changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. In addition, it is natural that it belongs to the scope of the present invention.

100: selective separation device of volatile iodine 102: reactor
104: heating mantle 106: thermometer holder
108: thermometer 110: injection tube holder
112: carrier gas injection pipe 114: carrier gas supply pipe
116: delivery pipe holder 118: delivery pipe
120: tube heater 122: gun collection
124: main collection input unit 126: insertion unit
128: outlet 130: discharge valve
132: secondary collecting pipe 134: buffer tank
136: plate 138: exhaust pipe
140: temperature sensor

Claims (6)

A reaction tank in which a heating mantle is provided on an outer circumferential surface, and an oxidation reaction for oxidizing iodine ions into volatile iodine by an oxidizing agent from a volatile iodine-containing solution heated by the heating mantle;
The volatile iodine is supplied through the transfer pipe by a carrier gas supplied from a carrier gas supply pipe installed in the reactor, and is connected to the reactor by the delivery gas, and the volatile iodine is filled by a nonpolar organic solvent filled therein. Optional separation device of volatile iodine comprising a main collection tank is separated.
The device of claim 1, wherein the oxidant is hydrogen peroxide.
The apparatus of claim 1, wherein a delivery tube heater is installed on an outer circumferential surface of the delivery tube.
According to claim 1, wherein the main collection tank is connected to the secondary collection pipe that can be discharged gas,
The auxiliary collecting pipe is formed with a bent portion bent in a U-shape, the bent portion is a selective separation device of volatile iodine characterized in that the non-polar organic solvent is charged.
[5] The apparatus of claim 4, wherein a buffer tank is integrally formed at an end of the auxiliary collecting pipe, and a diaphragm is disposed in the buffer tank to prevent the flow of gas.
5. The device of claim 4, wherein the nonpolar organic solvent is sulfuric acid.

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