KR102539152B1 - A apparatus of removing tritium in radioactive wastewater - Google Patents

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, and in the first reaction tank, the tritium and carbon dioxide And carbohydrates are synthesized in the cells of the microalgae by the photosynthetic process of the microalgae introduced into the first reaction tank by using light, and the tritium contained in the radioactive wastewater in which carbohydrates containing tritium as a component are synthesized. It is about a hydrogen removal device.

Description

Apparatus for removing tritium in radioactive wastewater {A apparatus of removing tritium in radioactive wastewater}

The present invention relates to an apparatus for removing tritium contained in radioactive wastewater, and removes tritium contained in radioactive wastewater through the photosynthesis process of algae, but can maximize the removal rate of tritium, and furthermore, tritium contained in radioactive wastewater It relates to a tritium removal device included in radioactive wastewater that can minimize the volume of secondary waste generated by removing the.

Tritium is one of the most important nuclides in terms of radiation safety management of nuclear power plants because it is difficult to concentrate and separate and occupies most of the radioactive effluent from nuclear power plants.

In general, in heavy water reactor nuclear power plants, heavy water (D ₂ O) is used as a coolant and a moderator required for operation of a nuclear reactor. During the output operation of the nuclear reactor, some of the heavy water combines with neutrons and turns into tritium ( ^3H or T) to generate radioactivity, the concentration of which increases with the number of operating years of the power plant.

Tritium is one of the isotopes of hydrogen and is an artificial radioactive element with a mass number of 3 consisting of one proton and two neutrons. Tritium is not only the heaviest among hydrogen isotopes, but also undergoes beta decay (β-decay), and as a radioactive element with a half-life of 12.3 years, it causes radioactive contamination when used in large quantities.

Tritium emits low-energy beta rays and enters the body through the breathing or skin of workers, causing internal exposure. Therefore, in heavy water reactor nuclear power plants, constant efforts are being made to prevent workers from being exposed to tritium by applying various methods.

Recently, tritium removal facilities (TRFs) are being operated in heavy water reactor nuclear power plants to reduce the effects of exposure due to tritium. However, the tritium removal facility does not completely remove tritium in the form of water vapor, and dilutes it with seawater and releases it into warm wastewater. Therefore, tritium (T ₂ O) in seawater can be a big problem when seawater is used as a source of drinking water.

On the other hand, technology related to an apparatus for removing tritium is disclosed in Korean Patent Registration No. 10-0532774. The prior art is a device for removing tritium in the air, and there is a problem that tritium discharged through hot wastewater from a nuclear power plant cannot be removed.

A bioengineering technique for removing tritium contained in radioactive wastewater is disclosed in Korean Patent Registration No. 10-1611275. It is a technology to remove tritium contained in radioactive wastewater by using photosynthesis of microalgae in a state where microalgae are injected into radioactive wastewater containing tritium.

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

Furthermore, in the current situation in which the volume of radioactive waste to be stored in a radioactive waste disposal facility must be minimized during radioactive waste treatment, tritium removed from radioactive wastewater is absorbed into the cells of microalgae, so there is a separate radioactive waste to be stored as radioactive waste. It still has the problem of generating bulky secondary waste (microalgae in which tritium is absorbed).

In order to solve the above-mentioned problems according to the prior art, tritium contained in radioactive wastewater can be removed using microalgae, but the tritium removal rate can be maximized, and furthermore, secondary waste generated in removing tritium from radioactive wastewater We would like to propose a tritium removal device that can minimize the volume.

In order to solve the problems according to the prior art described above, the tritium removal device included in radioactive wastewater according to the present invention includes a first reaction tank in an aerobic state into which radioactive wastewater and microalgae containing tritium are introduced,

In the first reaction tank, carbohydrates are synthesized in the cells of the microalgae by the photosynthesis process of the microalgae introduced into the first reaction tank by using the tritium, carbon dioxide, and light, and the state in which the tritium is included as a component of carbohydrates can be synthesized.

Preferably, it further comprises a second reaction tank introduced after the microalgae subjected to photosynthesis in the first reaction tank are separated from the first reaction tank,

The second reactor may be in a microaerobic or anaerobic state.

Preferably, in the second reactor, methane is produced by fermenting carbohydrates in the microalgae cells by the enzymatic action of microaerobic microorganisms or anaerobic microorganisms, methane in a state in which tritium released from the carbohydrates is included as a component this can be created.

Preferably, the first reaction tank includes a first detailed reaction tank, a second detailed reaction tank, and a third detailed reaction tank,

The radioactive wastewater and microalgae containing tritium are introduced into each of the first sub-reaction tank, the second sub-reaction tank, and the third sub-reaction tank,

The radioactive wastewater containing tritium introduced into the second sub-reaction tank is radioactive wastewater containing tritium separated after photosynthesis in the first sub-reaction tank,

The radioactive wastewater containing tritium introduced into the third sub-reaction tank may be radioactive wastewater containing tritium separated after undergoing a photosynthesis process in the second sub-reaction tank.

Preferably, carbon dioxide is supplied to each of the first sub-reaction tank, the second sub-reaction tank, and the third sub-reaction tank in a state in which a carbon dioxide supply device is communicated with each of the first sub-reaction tank, the second sub-reaction tank, and the third sub-reaction tank. becomes,

In a state in which the first sub-reaction tank and the second sub-reaction tank are in communication, the radioactive wastewater containing tritium from the first sub-reaction tank passes through a filter and is introduced into the second sub-reaction tank;

In a state where the second sub-reaction tank and the third sub-reaction tank are in communication, the radioactive wastewater containing tritium from the second sub-reaction tank passes through a filter and is introduced into the third sub-reaction tank;

In a state in which the methane collector is in communication with the second reaction tank, methane generated 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 sentesmus, or tetraselmis, chlorella, and dunaliella. ), at least one seawater microalgae selected from chaetoceros, nannochloropsis and isochrysis,

The microaerobic microorganism or anaerobic microorganism may be any one or more microorganisms selected from Cellulomonas, Pseudomonas, Rhodopseudomonas, Flavobacterium, and Bacillus.

Due to the above-described problem solving means, by specifying a process in which tritium contained in radioactive waste is removed by photosynthesis of microalgae, it is possible to minimize the volume of secondary waste generated by removing tritium thereafter. In other words, tritium is included as a component of carbohydrates during the process of synthesizing carbohydrates in the photosynthesis process of microalgae, and then, by fermenting these carbohydrates to capture tritium in the form of a gas, tritium is removed. It is possible to minimize the volume of secondary waste generated along the way.

Furthermore, due to the above-described problem solving means, it is possible to maximize the removal rate of tritium in removing tritium contained in radioactive wastewater in the photosynthesis process of microalgae.

Figure 1 is a flow chart for the step of removing tritium contained in radioactive wastewater.
2 and 3 are views schematically showing an apparatus for removing tritium contained in radioactive wastewater.

Hereinafter, preferred embodiments according to the present invention will be described with reference to the accompanying drawings. In this process, the thickness of lines or the size of components shown in the drawings may be exaggerated for clarity and convenience of explanation. In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of a user or operator. Therefore, definitions of these terms will have to be made based on the content throughout this specification.

Referring to FIG. 1, a method of removing tritium contained in radioactive wastewater will be described.

100: Step in which radioactive wastewater and microalgae containing tritium are introduced into the first reactor

The first reactor may be in an aerobic state. Radioactive wastewater containing tritium and microalgae undergoing photosynthesis may be introduced into the first reaction tank.

Microalgae to be introduced can be any microalgae as long as they synthesize carbohydrates using hydrogen contained in water in the photosynthesis process, and are preferably selected from among chlorella, spirulina and sentesmus. Any one or more selected freshwater microalgae, or tetraselmis, chlorella, dunaliella, chaetoceros, nannochloropsis and isochrysis ( isochrysis) may be any one or more seawater microalgae selected from.

These microalgae can be replaced by plants capable of synthesizing carbohydrates using hydrogen contained in water through photosynthesis.

200: step of synthesizing carbohydrates in microalgal cells by photosynthesis of microalgae

Photosynthesis of microalgae may proceed in the first reaction tank in an aerobic state. Carbohydrates can be synthesized in microalgal cells through the photosynthetic process of microalgae. At this time, the photosynthesis of microalgae may proceed using carbon dioxide, light, water, and tritium contained in radioactive wastewater supplied to the first reaction tank.

Carbohydrates are synthesized in microalgal cells through photosynthesis of microalgae. At this time, tritium contained in radioactive wastewater may be included as a component of carbohydrates synthesized in microalgal cells. This process can remove tritium from radioactive wastewater.

In order to synthesize carbohydrates in microalgal cells through photosynthesis, hydrogen, carbon dioxide, and light energy contained in water are used, and energy is required according to the movement of electrons during carbohydrate synthesis. As energy is released from the movement of electrons during reduction, it appears to promote carbohydrate synthesis. In carbohydrate synthesis, tritium contained in radioactive wastewater may have higher selectivity as a carbohydrate component than ordinary hydrogen contained in water. there is.

Accordingly, when carbohydrates are synthesized in microalgal cells through photosynthesis, tritium contained in radioactive wastewater is used and eventually tritium contained in radioactive wastewater can be removed.

Unlike the prior art, which discloses a technology in which heavy tritium cannot escape from microalgal cells in a state where tritium contained in radioactive wastewater is absorbed into microalgae cells through photosynthesis, in the present invention, tritium is absorbed into microalgae cells through photosynthesis. It discloses the technical feature of being included as a component of carbohydrates synthesized in algae cells.

According to the prior art, which has no choice but to store microalgae containing tritium separately, there is still a problem in that a large volume of secondary waste called microalgae containing tritium is generated. That is, problems in storage of radioactive waste in a large volume follow.

However, in the present invention, by specifying a process in which tritium contained in radioactive waste is removed by photosynthesis of microalgae, it is possible to minimize secondary waste generated by removing tritium thereafter. That is, during the process of synthesizing carbohydrates in the photosynthesis process of microalgae, tritium is included as a component of carbohydrates, and then these carbohydrates are fermented to collect tritium contained in carbohydrates in the form of a gas. As tritium is removed, The volume of secondary waste generated can be minimized.

Without specifying the technical feature that tritium is included in carbohydrates in the photosynthetic process, the technical feature that tritium can be stored in the form of a low-volume gas by fermenting these carbohydrates in a microaerobic or anaerobic state cannot be predicted at all. That is, the technical feature of separating tritium from microalgae by fermentation in a microaerobic or anaerobic state cannot be predicted only with the technical feature that tritium is included in the microalgae cell as a photosynthetic process.

300: Step in which microalgae that have undergone photosynthesis are put into a second reactor in a microaerobic or anaerobic state

Carbohydrate synthesis in microalgae cells in the photosynthetic process in the first reactor is a state in which tritium is included as a component of carbohydrates.

In order to release tritium from these carbohydrates, microalgae may be introduced into the second reactor in a microaerobic or anaerobic state in which dissolved oxygen is very low.

Microaerobic or anaerobic microorganisms may be introduced into the second reaction tank in order to ferment carbohydrates in the cells of microalgae by enzymatic action of the microaerobic or anaerobic microorganisms.

A microaerobic microorganism or anaerobic microorganism may be any microorganism capable of enzymatically fermenting carbohydrates. Preferably, it may be any one or more microorganisms selected from Cellulomonas, Pseudomonas, Rhodopseudomonas, Flavobacterium, and Bacillus.

400: Step in which methane is produced by fermenting carbohydrates in microalgae cells in the second reactor

Carbohydrates in microalgal cells are fermented by enzymatic action of microaerobic or anaerobic microorganisms introduced into the second reaction tank, and methane may be generated as the carbohydrates are fermented. Tritium contained in carbohydrates is released from carbohydrates through the fermentation process and can eventually be included as a component of the methane produced.

Accordingly, unlike the prior art in which the secondary waste generated by the removal of tritium was bulky microalgae itself, the secondary waste to be stored as radioactive waste can be limited to the form of methane gas with a small volume, The volume of secondary waste can be minimized.

500: Collect methane containing tritium in methane collector

Methane generated in the second reactor may be collected in the methane collector connected to the second reactor. Captured methane may contain tritium as a constituent.

Then, if tritium can be separated from the captured methane in a separate process, the volume of secondary waste to be stored as radioactive waste can be further reduced, or separated tritium can be reused in a nuclear power plant. It may also be configured so that no tea waste is generated.

An apparatus for removing tritium contained in radioactive wastewater will be described with reference to FIGS. 2 and 3 .

An embodiment will be described with reference to FIG. 2 .

The tritium removal device included in the radioactive wastewater is a first reaction tank in an aerobic state into which radioactive wastewater and algae containing tritium are introduced, and microalgae that have undergone photosynthesis in the first reaction tank are separated from the first reaction tank. A second reaction vessel may be included.

In the first reactor in an aerobic state, the process of photosynthesis in microalgae proceeds by using tritium, carbon dioxide, and light contained in radioactive wastewater, and thus the synthesized carbohydrate may contain tritium as a component, as described above. same as bar

Furthermore, in order to maximize the photosynthetic process of microalgae, the first reaction tank may be made of a transparent material through which light may pass, and a light source device through which light may be irradiated may be installed in the first reaction tank. The light source device may be an LED lighting device.

An air supply device or a carbon dioxide supply device may be installed to supply air or carbon dioxide to the first reaction tank, and preferably may be installed to supply air or carbon dioxide from the lower part of the first reaction tank.

Furthermore, for smooth contact between radioactive wastewater and microalgae, a stirring device may be installed inside the first reaction tank, and a temperature control device capable of adjusting the temperature of the first reaction tank to suit photosynthetic conditions may be provided.

In a state in which tritium is included as a component in the carbohydrates synthesized in the first reaction tank, microalgae containing the synthesized carbohydrates are introduced into the second reaction tank in a microaerobic or anaerobic state, and microaerobic or As described above, carbohydrates are fermented by enzymatic action of anaerobic microorganisms to generate methane, and tritium may be included in the generated methane.

In a state in which the methane collector communicates with the second reactor, methane generated in the second reactor may be collected in the methane collector.

Furthermore, a separate device capable of separating tritium from methane may be provided in the methane collector. In removing tritium, the volume of secondary waste to be stored as radioactive waste can be minimized.

Another embodiment will be described with reference to FIG. 3 .

The first reaction tank may include a first detailed reaction tank, a second detailed reaction tank, and a third detailed reaction tank.

Technical characteristics of the material of the reaction tank described in the embodiment, the air supply device or carbon dioxide supply device, the light source device, the stirring device, the temperature control device, etc. are applied to the first sub-reaction tank, the second sub-reaction tank, and the third sub-reaction tank, respectively. can

Radioactive wastewater and microalgae containing tritium may be introduced into each of the first sub-reaction tank, the second sub-reaction tank, and the third sub-reaction tank. However, the radioactive wastewater containing tritium introduced into the second sub-reaction tank is radioactive wastewater containing tritium separated after photosynthesis in the first sub-reaction tank, and the radioactive wastewater containing tritium injected into the third sub-reaction tank. The radioactive wastewater may be radioactive wastewater containing tritium separated after photosynthesis in the second sub-reactor.

That is, in removing tritium contained in radioactive wastewater, it is intended to increase the tritium removal rate by undergoing a multi-stage photosynthesis process. Looking at the experimental results to be described later, the tritium removal rate after passing through the first sub-reaction tank was about 60%, but the tritium removal rate after passing through the third sub-reaction tank reached 93.6%.

As shown in FIG. 3 , microalgae that have undergone photosynthesis in each of the first sub-reaction tank, the second sub-reaction tank, and the third sub-reaction tank may be introduced into the second sub-reaction tank.

Furthermore, in a state in which the first sub-reaction tank and the second sub-reaction tank are in communication, the radioactive wastewater containing tritium from the first sub-reaction tank is introduced into the second sub-reaction tank through a filter to perform the photosynthesis process in the first sub-reaction tank. It is possible to block the flow of coarse microalgae into the second sub-reactor.

Similarly, in a state in which the second sub-reaction tank and the third sub-reaction tank are connected, the radioactive wastewater containing tritium from the second sub-reaction tank is passed through a filter and introduced into the third sub-reaction tank to perform the photosynthesis process in the second sub-reaction tank. It is possible to block coarse microalgae from flowing into the third sub-reactor.

The description of the remaining components follows the description of one embodiment.

Experiment

In a state where 500 mL of radioactive wastewater having a tritium concentration of 2,000 Bq/mL was introduced into the first reactor, the photosynthesis process was allowed to proceed in chlorella and spirulina introduced into the first reactor.

The concentration of tritium in the radioactive wastewater remaining after the photosynthetic reaction for 5 days was measured.

After photosynthesis in the first reactor, chlorella was separated from the first reactor and then introduced into the anaerobic second reactor, Cellulomonas, Pseudomonas, and Rhodopseudomonas Fermentation was carried out by enzymatic action.

Methane generated during the fermentation process was collected, and then tritium was analyzed in the condensate of the collected methane gas to confirm whether tritium was included in the methane.

Experiment result

The tritium concentration of 500mL of radioactive wastewater introduced into the first sub-reaction tank is 2,000 Bq/mL, and the tritium concentration of the radioactive wastewater in the first sub-reaction tank after the photosynthesis process in the first sub-reaction tank is measured to be 800 Bq/mL. It became.

The radioactive wastewater that had undergone the photosynthesis process in the first sub-reaction tank was put into the second sub-reaction tank to proceed with the photosynthesis process, and the tritium concentration of the radioactive wastewater in the second sub-reaction tank was 320 Bq/mL was measured as

The radioactive wastewater that had undergone the photosynthesis process in the second sub-reaction tank was introduced into the third sub-reaction tank to proceed with the photosynthesis process. was measured as

The removal rate of tritium removed through the photosynthesis process in the first sub-reactor was 60%, and the removal rate of tritium removed through the photosynthesis process through the final third sub-reaction tank reached 93.6%.

Chlorella, which has undergone photosynthesis in each of the first sub-reaction tank, the second sub-reaction tank, and the third sub-reaction tank, was put into the second sub-reaction tank and subjected to fermentation. Carbohydrates in chlorella were fermented under anaerobic conditions to generate methane, and the generated methane was condensed, sampled from the condensed methane, and tritium present in the methane condensate was measured using LSC.

The measured results are shown in Table 1.

day One 3 5 7 9 10 12 Tritium concentration (Bq/mL) 0 450 1,300 9,400 15,000 8,200 1,100

In the anaerobic reaction, methane was generated, and it was confirmed that the concentration of tritium increased with the reaction time in the sample of methane condensate in which the generated methane was condensed.

In the above, 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 only exemplary, and those skilled in the art can make various modifications and equivalents from the embodiments of the present invention. It will be appreciated that embodiments are possible. Therefore, the scope of protection of the present invention should be defined by the claims.

Claims (5)

A first reaction tank in an aerobic state into which radioactive wastewater and microalgae containing tritium are introduced; and
And a second reaction tank introduced after the microalgae that have undergone photosynthesis in the first reaction tank are separated from the first reaction tank,
In the first reaction tank, carbohydrates are synthesized in the cells of the microalgae by the photosynthesis process of the microalgae introduced into the first reaction tank by using the tritium, carbon dioxide, and light, and the state in which the tritium is included as a component of carbohydrates are synthesized,
The second reaction tank is in a microaerobic or anaerobic state,
In the second reaction tank, carbohydrates in the microalgal cells are fermented by enzymatic action of microaerobic microorganisms or anaerobic microorganisms to produce methane, and methane is produced in a state in which tritium released from the carbohydrates is included as a component,
In a state in which the methane collector is in communication with the second reaction tank, methane generated in the second reaction tank is collected in the methane collector,
The methane collected by the methane collector contains the tritium,
In the first reaction tank, tritium contained in the radioactive wastewater is used in the photosynthetic process of microalgae and included as a component of carbohydrates in the cells of the microalgae synthesized in the photosynthetic process, thereby triple hydrogen in the radioactive wastewater introduced into the first reaction tank. hydrogen is removed,
Thereafter, microalgae that have undergone photosynthesis in the first reactor are introduced into the second reactor,
Thereafter, tritium, which is included as a component of carbohydrates in the microalgae introduced into the second reaction tank, is included as a component of methane produced by fermentation in the second reaction tank, so that the composition of carbohydrates in microalgae introduced into the second reaction tank While the tritium included as a component is removed from the carbohydrates in the microalgae introduced into the second reaction tank, the tritium contained in the radioactive wastewater introduced into the first reaction tank is included in the methane captured in the methane collector. Tritium removal device contained in radioactive wastewater collected by
delete delete According to claim 1,
The first reaction tank includes a first detailed reaction tank, a second detailed reaction tank, and a third detailed reaction tank,
The radioactive wastewater and microalgae containing tritium are introduced into each of the first sub-reaction tank, the second sub-reaction tank, and the third sub-reaction tank,
The radioactive wastewater containing tritium introduced into the second sub-reaction tank is radioactive wastewater containing tritium separated after photosynthesis in the first sub-reaction tank,
The radioactive wastewater containing tritium introduced into the third sub-reaction tank is a radioactive wastewater containing tritium separated after undergoing a photosynthesis process in the second sub-reaction tank. Tritium removal device included in radioactive wastewater.
According to claim 4,
Carbon dioxide is supplied to each of the first sub-reaction tank, the second sub-reaction tank, and the third sub-reaction tank in a state in which the carbon dioxide supply device is in communication with each of the first sub-reaction tank, the second sub-reaction tank, and the third sub-reaction tank,
In a state in which the first sub-reaction tank and the second sub-reaction tank are in communication, the radioactive wastewater containing tritium from the first sub-reaction tank passes through a filter and is introduced into the second sub-reaction tank;
In a state where the second sub-reaction tank and the third sub-reaction tank are in communication, the radioactive wastewater containing tritium from the second sub-reaction tank passes through a filter and is introduced into the third sub-reaction tank;
The microalgae is any one or more freshwater microalgae selected from chlorella, spirulina, and sentesmus, or tetraselmis, chlorella, and dunaliella. ), at least one seawater microalgae selected from chaetoceros, nannochloropsis and isochrysis,
The microaerobic microorganism or anaerobic microorganism is any one or more microorganisms selected from Cellulomonas, Pseudomonas, Rhodopseudomonas, Flavobacterium, and Bacillus included in the radioactive wastewater tritium removal device.

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