Equipment for removing tritium from radioactive wastewater

Abstract

The present invention relates to an apparatus for removing tritium contained in radioactive wastewater, and includes a first reaction tank in an aerobic state into which radioactive wastewater containing tritium and microalgae are introduced. In the first reaction tank, the tritium, carbon dioxide and light are used, and carbohydrates are synthesized within the cells of the microalgae through the photosynthesis process of the microalgae introduced into the first reaction tank, and at this time, carbohydrates containing the tritium as a constituent are synthesized.

Description

[Technical field]

[0001] The present invention relates to an apparatus for removing tritium contained in radioactive wastewater, and more particularly, to an apparatus for removing tritium contained in radioactive wastewater by using the photosynthesis process of algae, maximizing a tritium removal rate, and further minimizing the volume of secondary waste generated when removing tritium contained in radioactive wastewater. [Background technology]

[0002] Tritium is difficult to enrich and separate, accounts for most of the radioactive effluent from nuclear power plants, and is one of the nuclides that is handled with great care in terms of radiation safety management at nuclear power plants.

[0003] Generally, heavy water reactor nuclear power plants use heavy water (DWR) as a coolant and moderator required for the operation of the reactor. 2 During reactor operation, some of the heavy water combines with neutrons to produce tritium (Tritium; 3 H or T), generating radioactivity, the concentration of which increases over the life of the plant.

[0004] Tritium is one of the hydrogen isotopes, and is an artificial radioactive element consisting of one proton and two neutrons with a mass number of 3. Tritium is not only the heaviest of all hydrogen isotopes, but it is also a radioactive element that undergoes beta decay and has a half-life of 12.3 years, and when used in large quantities, it can cause radioactive contamination.

[0005] Tritium emits low-energy beta radiation and can enter the body through the breath or skin of workers, causing internal radiation exposure. Therefore, heavy water reactor nuclear power plants are constantly making efforts to prevent workers from being exposed to tritium, including by applying various methods.

[0006] Recently, in order to reduce the effects of tritium exposure, tritium removal facilities (TRFs) have been put into operation at nuclear power plants using heavy water reactors. However, the tritium removal facilities are unable to completely remove tritium in the form of water vapor, and it is diluted with seawater and discharged as heated wastewater. Therefore, when seawater is used as a source of drinking water, it is necessary to take into account the tritium (T 2 O) can be a big problem.

[0007] Meanwhile, technology relating to an apparatus for removing tritium is disclosed in Patent Document 1: Korean Patent Registration No. 10-0532774. The prior art relates to an apparatus for removing tritium from the air, but has a problem in that it cannot remove tritium discharged from nuclear power plants via heated wastewater.

[0008] A technology for biotechnologically removing tritium from radioactive wastewater is disclosed in Patent Document 2: Korean Patent Registration No. 10-1611275. This technology involves adding microalgae to radioactive wastewater containing tritium and using the photosynthesis of the microalgae to remove tritium from the radioactive wastewater.

[0009] However, when removing tritium contained in radioactive wastewater by photosynthesis of microalgae, the removal rate of tritium is limited.

[0010] Furthermore, in the current situation where the volume of radioactive waste to be stored at radioactive waste treatment facilities must be minimized when treating radioactive waste, the tritium removed from the radioactive wastewater is absorbed into the cells of the microalgae, which still poses the problem of generating a large volume of secondary waste (microalgae with absorbed tritium) that needs to be stored as radioactive waste. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Korean Patent Registration No. 10-0532774 [Patent Document 2] Korean Patent Registration No. 10-1611275 Summary of the Invention [Problem to be solved by the invention]

[0012] In order to solve the above-mentioned problems of the conventional technology, a tritium removal device is proposed that can remove tritium contained in radioactive wastewater using microalgae, maximize the tritium removal rate, and minimize the volume of secondary waste generated when removing tritium from radioactive wastewater. [Means for solving the problem]

[0013] In order to solve the problems of the conventional technology described above, the apparatus for removing tritium contained in radioactive wastewater according to the present invention includes a first reaction tank in an aerobic state into which radioactive wastewater containing tritium and microalgae are introduced, and in the first reaction tank, the tritium, carbon dioxide and light are used, and carbohydrates are synthesized within the cells of the microalgae through the photosynthesis process of the microalgae introduced into the first reaction tank, and at this time, carbohydrates containing the tritium as a constituent can be synthesized.

[0014] Preferably, the microalgae that has undergone a photosynthetic process in the first reaction tank is separated in the first reaction tank and then introduced into a second reaction tank, The second reactor can be in microaerobic or anaerobic conditions.

[0015] Preferably, in the second reaction tank, carbohydrates in the cells of the microalgae are fermented by the enzymatic action of microaerobic microorganisms or anaerobic microorganisms to produce methane, and at this time, methane containing tritium released from the carbohydrates as a constituent may be produced.

[0016] Preferably, the first reaction vessel comprises a first part reaction vessel, a second part reaction vessel and a third part reaction vessel; The tritium-containing radioactive wastewater and microalgae are introduced into each of the first, second and third sub-reactors, The radioactive wastewater containing tritium introduced into the second sub-reactor is radioactive wastewater containing tritium separated after undergoing a photosynthetic process in the first sub-reactor, The radioactive wastewater containing tritium introduced into the third reactor section may be radioactive wastewater containing tritium separated after undergoing a photosynthesis process in the second reactor section.

[0017] Preferably, carbon dioxide is supplied to each of the first, second and third small section reaction tanks in a state where a carbon dioxide supplying device is connected to each of the first, second and third small section reaction tanks, In a state in which the first and second small-area reactors are in communication with each other, radioactive wastewater containing tritium from the first small-area reactor is introduced into the second small-area reactor through a filter; In a state in which the second and third small-area reactors are in communication with each other, radioactive wastewater containing tritium from the second small-area reactor is introduced into the third small-area reactor through a filter; With a methane collector in communication with the second reaction tank, methane produced in the second reaction tank is collected in the methane collector, The microalgae is any one or more freshwater microalgae selected from Chlorella, Spirulina, and Senedesmus, or any one or more marine microalgae selected from Tetraselmis, Chlorella, Dunaliella, Chaetoceros, Nannochloropsis, and Isochrysis; The microaerophilic or anaerobic microorganism may be one or more microorganisms selected from Cellulomonas, Pseudomonas, Rhodopseudomonas, Flavobacterium, and Bacillus. Effect of the Invention

[0018] By identifying the process in which tritium contained in radioactive waste is removed by the photosynthesis of microalgae using the means for solving the above problems, it is possible to minimize the volume of secondary waste generated as tritium is subsequently removed. That is, tritium is included as a component of carbohydrates during the process in which carbohydrates are synthesized by the photosynthesis process of microalgae, and then the carbohydrates are fermented and the tritium contained in the carbohydrates is collected in the form of gas, thereby minimizing the volume of secondary waste generated as tritium is removed.

[0019] Furthermore, by using the means for solving the above-mentioned problems, it is possible to maximize the removal rate of tritium when removing tritium contained in radioactive wastewater through the photosynthetic process of microalgae. [Brief description of the drawings]

[0020] [Figure 1] 1 is a flow chart showing steps for removing tritium contained in radioactive wastewater. [Diagram 2] 1 is a schematic diagram of an apparatus for removing tritium contained in radioactive wastewater. [Diagram 3] 1 is a schematic diagram of an apparatus for removing tritium contained in radioactive wastewater. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In this process, the thickness of lines and the size of components shown in the drawings may be exaggerated for clarity and convenience of description. In addition, the terms described below are defined in consideration of the functions of the present invention, and may vary depending on the intention or practice of a user or operator. Therefore, the definitions of such terms are based on the entire contents of this specification.

[0022] A method for removing tritium contained in radioactive wastewater will be described with reference to FIG.

[0023] 100: A step in which radioactive wastewater containing tritium and microalgae are introduced into a first reaction tank The first reaction tank may be in an aerobic state, and radioactive wastewater containing tritium and microalgae undergoing photosynthesis may be introduced into the first reaction tank.

[0024] The microalgae to be added may be any microalgae that synthesizes carbohydrates using hydrogen contained in water through a photosynthetic process, and is preferably any one or more freshwater microalgae selected from chlorella, spirulina, and senedesmus, or any one or more marine microalgae selected from tetraselmis, chlorella, dunaliella, chaetoceros, nannochloropsis, and isochrysis.

[0025] Such microalgae can replace plants, capable of synthesizing carbohydrates using the hydrogen contained in the water through the process of photosynthesis.

[0026] 200: Steps in which carbohydrates are synthesized within microalgae cells by photosynthesis in microalgae In the first reaction tank under aerobic conditions, the photosynthesis process of the microalgae can be carried out. Carbohydrates can be synthesized within the cells of the microalgae through the photosynthesis process of the microalgae. Here, the photosynthesis of the microalgae can be carried out using carbon dioxide, light, water, and tritium contained in the radioactive wastewater supplied to the first reaction tank.

[0027] Carbohydrates are synthesized within the microalgae cells through photosynthesis of the microalgae, and tritium contained in the radioactive wastewater can be included as a component of the carbohydrates synthesized within the microalgae cells. Through this process, tritium can be removed from the radioactive wastewater.

[0028] In order for carbohydrates to be synthesized within the cells of microalgae through the photosynthesis process, hydrogen, carbon dioxide, light energy, etc. contained in water are used, and during the carbohydrate synthesis process, energy is required through the movement of electrons. In the case of tritium, its radioactive energy is reduced and energy through the movement of electrons is released, which is believed to promote the synthesis of carbohydrates. In the synthesis of carbohydrates, tritium contained in radioactive wastewater may have a higher selectivity as a carbohydrate component than ordinary hydrogen contained in water.

[0029] Therefore, when carbohydrates are synthesized within the cells of the microalgae by photosynthesis, the tritium contained in the radioactive wastewater is used, and as a result, the tritium contained in the radioactive wastewater can be removed.

[0030] Unlike the prior art, which disclosed a technology in which tritium contained in radioactive wastewater is absorbed into the cells of microalgae through the photosynthesis process and the heavy tritium cannot escape from the cells of the microalgae, the present invention discloses a technical feature in which tritium is contained as a component of carbohydrates synthesized within the cells of microalgae through the photosynthesis process.

[0031] According to the prior art, the only option is to separately store the tritium-containing microalgae, which still has the problem of generating a large volume of secondary waste, i.e., the large volume poses problems in storing radioactive waste.

[0032] However, in the present invention, by specifying the process in which tritium contained in radioactive waste is removed by photosynthesis of microalgae, it is possible to minimize the secondary waste generated as tritium is subsequently removed. That is, tritium is contained as a component of carbohydrates during the process in which carbohydrates are synthesized by photosynthesis of microalgae, and then the carbohydrates are fermented and the tritium contained in the carbohydrates is collected in the form of gas, thereby minimizing the volume of secondary waste generated as tritium is removed.

[0033] Without specifying the technical feature that tritium is contained in carbohydrates through the photosynthetic process, it is impossible to predict the technical feature that such carbohydrates can be fermented in a microaerobic or anaerobic state and tritium can be stored in a small-volume gas form. In other words, the technical feature that tritium is contained within the cells of microalgae through the photosynthetic process alone does not allow prediction of the technical feature that tritium is fermented in a microaerobic or anaerobic state and separated from the microalgae.

[0034] 300: A step in which the microalgae that have undergone the photosynthetic process are introduced into a second reaction tank in a microaerobic or anaerobic state. In the first reaction tank, tritium is included as a component of carbohydrates due to the synthesis of carbohydrates within the cells of microalgae through the photosynthesis process.

[0035] To release tritium from such carbohydrates, the microalgae can be placed in a second reactor with microaerobic or anaerobic conditions where dissolved oxygen is very low.

[0036] Microaerophilic or anaerobic microorganisms can be added to the second reaction vessel to ferment carbohydrates within the cells of the microalgae through the enzymatic action of the microaerophilic or anaerobic microorganisms.

[0037] The microaerophilic or anaerobic microorganism may be any microorganism capable of enzymatically fermenting carbohydrates, preferably one or more microorganisms selected from Cellulomonas, Pseudomonas, Rhodopseudomonas, Flavobacterium and Bacillus.

[0038] 400: A step in which carbohydrates in the cells of microalgae are fermented in the second reactor to produce methane. The carbohydrates in the cells of the microalgae are fermented by the enzymatic action of the microaerobic or anaerobic microorganisms introduced into the second reactor, and methane can be produced as the carbohydrates are fermented. Tritium contained in the carbohydrates is released from the carbohydrates through the fermentation process, and can ultimately be included as a component of the produced methane.

[0039] As a result, unlike the prior art in which the secondary waste generated as tritium was removed was the microalgae itself, which had a large volume, the secondary waste to be stored as radioactive waste can be limited to the form of methane gas, which has a small volume, thereby minimizing the volume of the secondary waste.

[0040] 500: Collect methane containing tritium using a methane collector The methane produced in the second reaction vessel can be collected by a methane collector connected to the second reaction vessel. The collected methane can contain tritium as a constituent.

[0041] If tritium can subsequently be separated from the collected methane in a separate process, the volume of secondary waste to be stored as radioactive waste can be further reduced, or the separately separated tritium can be reused, for example in a nuclear power plant, thereby preventing the generation of secondary waste altogether.

[0042] An apparatus for removing tritium contained in radioactive wastewater will be described with reference to Figs. 2 and 3. One embodiment will be described with reference to FIG.

[0043] The device for removing tritium contained in radioactive wastewater may include a first aerobic reactor into which the radioactive wastewater containing tritium and algae are introduced, and a second reactor into which the microalgae that have undergone the photosynthetic process in the first reactor are separated and then introduced.

[0044] As described above, in the first reaction tank under aerobic conditions, the photosynthesis process is carried out in the microalgae using tritium, carbon dioxide, light, etc. contained in the radioactive wastewater, and the carbohydrates synthesized in this way may contain tritium as a constituent.

[0045] Furthermore, in order to maximize the photosynthesis process of the microalgae, the first reaction tank may be made of a transparent material through which light can pass, and a light source device that can irradiate light to the first reaction tank may be installed. The light source device may be an LED lighting device.

[0046] An air supplying device or a carbon dioxide supplying device may be attached to the first reaction tank so that air or carbon dioxide is supplied to the first reaction tank, and preferably, the device may be attached so that air or carbon dioxide is supplied from the lower part of the first reaction tank.

[0047] Furthermore, in order to ensure smooth contact between the radioactive wastewater and the microalgae, an agitator may be installed inside the first reaction tank, and a temperature control device capable of adjusting the temperature of the first reaction tank according to the photosynthetic conditions may also be provided.

[0048] As described above, the carbohydrates synthesized in the first reaction tank contain tritium as a constituent component, and the microalgae containing the synthesized carbohydrates are introduced into a second reaction tank under microaerobic or anaerobic conditions, where the carbohydrates are fermented by the enzymatic action of microaerobic or anaerobic microorganisms to produce methane in the microaerobic or anaerobic conditions, and the produced methane may contain tritium.

[0049] With the methane collector in communication with the second reaction vessel, methane produced in the second reaction vessel can be collected in the methane collector.

[0050] Additionally, the methane collector may be equipped with a separate device capable of separating tritium from methane. In removing tritium, the volume of secondary waste that must be stored as radioactive waste can be minimized.

[0051] Another embodiment will now be described with reference to FIG.

[0052] The first reaction vessel can include a first part reaction vessel, a second part reaction vessel and a third part reaction vessel.

[0053] The technical features relating to the material of the reaction tank, the attached air supply device or carbon dioxide supply device, light source device, stirring device, temperature control device, etc. described in one embodiment can be applied to each of the first small-scale reaction tank, the second small-scale reaction tank, and the third small-scale reaction tank.

[0054] The radioactive wastewater containing tritium and microalgae may be introduced into each of the first, second and third detailed reactors, provided that the radioactive wastewater containing tritium introduced into the second detailed reactor may be radioactive wastewater containing tritium separated after undergoing a photosynthesis process in the first detailed reactor, and the radioactive wastewater containing tritium introduced into the third detailed reactor may be radioactive wastewater containing tritium separated after undergoing a photosynthesis process in the second detailed reactor.

[0055] In other words, the purpose is to increase the tritium removal rate by making the tritium undergo multiple photosynthesis processes when removing tritium from radioactive wastewater. Referring to the experimental results described below, the tritium removal rate after passing through the first detailed reactor was about 60%, but after passing through the third detailed reactor, the tritium removal rate reached 93.6%.

[0056] As shown in FIG. 3, microalgae that have undergone photosynthesis in each of the first, second and third sub-reactors may be introduced into the second sub-reactor.

[0057] Furthermore, with the first and second detailed reactors connected to each other, radioactive wastewater containing tritium from the first detailed reactor is introduced into the second detailed reactor through a filter, thereby preventing microalgae that have undergone the photosynthetic process in the first detailed reactor from flowing into the second detailed reactor.

[0058] Similarly, with the second and third detailed reactors connected to each other, radioactive wastewater containing tritium from the second detailed reactor is introduced into the third detailed reactor through a filter, thereby preventing microalgae that have undergone the photosynthetic process in the second detailed reactor from flowing into the third detailed reactor.

[0059] The remaining components will be described according to the description of one embodiment.

[0060] experiment 500mL of radioactive wastewater with a tritium concentration of 2,000Bq / mL was poured into the first reactor, and the photosynthesis process was carried out in the chlorella and spirulina placed in the first reactor.

[0061] After 5 days of photosynthetic reaction, the concentration of tritium in the remaining radioactive wastewater was measured.

[0062] After undergoing the photosynthesis process in the first reactor, the chlorella was separated from the first reactor and then placed in the second reactor, which was in an anaerobic state, where fermentation took place through the enzymatic action of Cellulomonas, Pseudomonas, and Rhodopseudomonas.

[0063] The methane produced during the fermentation process was collected, and the condensed water from the collected methane was analyzed for tritium to confirm whether tritium was contained in the methane.

[0064] Experimental Results The tritium concentration of the 500 mL of radioactive wastewater poured into the first detailed reactor was 2,000 Bq / mL, and after the photosynthesis process in the first detailed reactor, the tritium concentration of the radioactive wastewater in the first detailed reactor was measured to be 800 Bq / mL.

[0065] The radioactive wastewater that had undergone the photosynthesis process in the first detailed reactor was introduced into the second detailed reactor where the photosynthesis process took place. After the photosynthesis process in the second detailed reactor, the tritium concentration of the radioactive wastewater in the second detailed reactor was measured to be 320 Bq / mL.

[0066] The radioactive wastewater that had undergone the photosynthesis process in the second detailed reactor was then poured into the third detailed reactor, where the photosynthesis process took place. After the photosynthesis process in the third detailed reactor, the tritium concentration of the radioactive wastewater in the third detailed reactor was measured to be 128 Bq / mL.

[0067] It was found that the tritium removal rate through the photosynthetic process in the first sub-reactor was 60%, and finally, the tritium removal rate through the photosynthetic process after passing through the third sub-reactor reached 93.6%.

[0068] Chlorella that had undergone photosynthesis in the first, second and third reactors was placed in the second reactor and fermented. Under anaerobic conditions, carbohydrates in the chlorella were fermented to produce methane, which was then condensed and sampled. The tritium present in the methane condensate was measured using LSC.

[0069] The measurement results are shown in Table 1.

[0070] [Table 1]

[0071] Methane was produced during the anaerobic reaction, and it was confirmed that the concentration of tritium in samples of methane condensate, which is the condensed form of methane, increased with reaction time.

[0072] The present specification has been described with reference to the embodiments shown in the drawings so that those skilled in the art can easily understand and reproduce the present invention, but this is merely an example, and those skilled in the art can understand that various modifications and equivalent other embodiments are possible from the embodiments of the present invention. Therefore, the scope of protection of the present invention is defined by the claims.

Claims

1. The method includes a first reaction tank in an aerobic state into which radioactive wastewater containing tritium and microalgae are introduced, In the first reaction tank, the tritium, carbon dioxide, and light are used, and carbohydrates are synthesized in the cells of the microalgae through a photosynthetic process of the microalgae introduced into the first reaction tank, and at this time, carbohydrates containing the tritium as a constituent are synthesized. An apparatus for removing tritium contained in radioactive wastewater, comprising:

2. The microalgae that has undergone a photosynthetic process in the first reaction tank is separated in the first reaction tank and then introduced into a second reaction tank, The second reaction tank is in a microaerobic or anaerobic state.

2. An apparatus for removing tritium contained in radioactive wastewater according to claim 1.

3. In the second reaction tank, carbohydrates in the cells of the microalgae are fermented by the enzyme action of microaerobic microorganisms or anaerobic microorganisms to produce methane, and at this time, methane containing tritium released from the carbohydrates as a constituent is produced.

3. The apparatus for removing tritium contained in radioactive wastewater according to claim 2.

4. The first reaction vessel includes a first small section reaction vessel, a second small section reaction vessel and a third small section reaction vessel, The tritium-containing radioactive wastewater and microalgae are introduced into each of the first small-area reaction tank, the second small-area reaction tank, and the third small-area reaction tank, The tritium-containing radioactive wastewater introduced into the second sub-reactor is radioactive wastewater containing tritium separated after undergoing a photosynthesis process in the first sub-reactor, The radioactive wastewater containing tritium fed to the third reactor is radioactive wastewater containing tritium separated after undergoing photosynthesis in the second reactor. The apparatus for removing tritium contained in radioactive wastewater according to claim 3.

5. Carbon dioxide is supplied to each of the first small section reaction tank, the second small section reaction tank, and the third small section reaction tank in a state in which a carbon dioxide supplying device is connected to each of the first small section reaction tank, the second small section reaction tank, and the third small section reaction tank; In a state in which the first and second small-area reaction vessels are in communication with each other, radioactive wastewater containing tritium from the first small-area reaction vessel is introduced into the second small-area reaction vessel through a filter; In a state in which the second and third small section reactors are in communication with each other, radioactive wastewater containing tritium from the second small section reactor is introduced into the third small section reactor through a filter; With a methane collector in communication with the second reaction tank, methane produced in the second reaction tank is collected in the methane collector, The microalgae is any one or more freshwater microalgae selected from Chlorella, Spirulina, and Senedesmus, or any one or more marine microalgae selected from Tetraselmis, Chlorella, Dunaliella, Chaetoceros, Nannochloropsis, and Isochrysis; The microaerophilic or anaerobic microorganism is at least one selected from the group consisting of Cellulomonas, Pseudomonas, Rhodopseudomonas, Flavobacterium, and Bacillus.

5. The apparatus for removing tritium contained in radioactive wastewater according to claim 4.

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