Processes for the treatment of radioactive liquid waste

Abstract

A method for treating radioactive liquid waste, the method comprising: Adding a metal ion, an oxidizer, and nitrogen oxide to radioactive liquid waste to produce a pretreatment solution; and Irradiating the pretreatment solution with irradiation radiation, wherein the metal ion comprises an iron ion or a copper ion, wherein the oxidizing agent comprises one or more selected from the group consisting of a peroxydisulfate anion (S 2 O 8 2- ) and a salt thereof, wherein an irradiation dose of the irradiation radiation based on an absorbed dose is 1 to 50 kGy.

Description

Technical fieldReference to related application

[0001] This application claims the benefit of Korean Patent KR 10 2 073 018 B1 and the corresponding Korean Patent Application No. 10-2018-135732, filed on November 7, 2018, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical field

[0002] The present invention relates to a technology for treating radioactive liquid waste, and more particularly, to a technology for treating radioactive liquid waste containing an organic decontaminant, an inorganic decontaminant, liquid scintillation counter liquid waste, and the like, which are generated in nuclear power plants, nuclear facilities, facilities using radiation (radioactivity), and the like. Background technology

[0003] A difficult-to-degrade composition is generated due to the use and the like of an organic decontaminant, an inorganic decontaminant and liquid scintillation counter liquid waste in nuclear power plants, nuclear power-related facilities and facilities where radiation (radioactivity) is used.

[0004] Chemical decontamination is a process for removing radiation (radioactivity) from devices, installations, or the like contaminated with radiation (radioactivity). It is a process that generates wastewater containing the above-mentioned difficult-to-degrade composition. Liquid scintillation counter technology is also widely used as a radiation measurement technology. In particular, due to the use of a liquid scintillation counter, a large amount of wastewater containing liquid scintillation counter liquid waste is generated.

[0005] The above-mentioned persistent compositions, such as organic decontaminants, inorganic decontaminants, organic scintillants, and the like, present in radioactive liquid waste degrade the performance of a purification system used in one treatment process for radioactive liquid waste treatment and react with metallic radioactive waste generated in another process, making its treatment difficult. Therefore, the treatment of persistent compositions is important.

[0006] Furthermore, when radioactive liquid waste containing the above-mentioned persistently degradable compound is stored in a drum, the persistently degradable compound and an oxidizer react, increasing the pressure inside the drum, posing a risk of explosion. Furthermore, in the case of using an evaporative concentration method, which is one of the methods for treating radioactive waste, if a persistently degradable compound is contained in the waste to be treated, an environmental hormone such as dioxin may be emitted. Therefore, the above method may also cause problems in the treatment of radioactive liquid waste.

[0007] Consequently, there is a need for a technology capable of appropriately treating the persistently degradable composition contained in radioactive liquid waste. Domestic chemical decontamination technologies, such as system decontamination, component decontamination, and the like, currently developed for nuclear power plant decommissioning include low-concentration chemical decontamination technology using an organic complexing agent, such as an organic acid or ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA), and decontamination technology based on organic acid-based low oxidation state metal ion regeneration (LOMI). In recent years, chemical decontamination technologies based on inorganic substances, such as nitric acid, sulfuric acid, hypochlorous acid, and hydrazine, have been developed.However, no examples of the actual application of an inorganic decontaminant have been reported, which may be due to the fact that the use of an inorganic decontaminant makes it more difficult to treat waste fluids containing inorganic substances. Consequently, organic acid-based decontaminants have been used at domestic nuclear power plants to date, and most of the organic acid-based decontamination technologies used rely on HP-CORD technology, primarily for oxalic acid, and a UV / hydrogen peroxide process for treating oxalic acid, which are foreign commercially available technologies.An organic acid-based decontamination liquid waste treatment technology developed by AREVA, France, which is the most widely used technology so far, is a technology that uses ultraviolet rays and chemicals from hydrogen peroxide to generate hydroxyl radicals and decompose oxalic acid, which is a decontamination agent.

[0008] However, since these techniques use UV with a high energy level, the irradiation range of ultraviolet rays to generate hydroxyl radicals is very short, so problems have been reported that a UV device and a large amount of hydrogen peroxide are needed, and a long process time, which is 5 hours or more, is required.

[0009] Therefore, ongoing research has been conducted to improve the treatment quantity and treatment efficiency of radioactive liquid waste.

[0010] DE 698 14 764 T2 discloses a method and apparatus for waste processing under supercritical conditions. DE 698 12 686 T2 discloses a method for treating a solution that has been used to decontaminate a radioactively contaminated surface. DE 44 10 747 A1 discloses a method and apparatus for disposing of a solution containing an organic acid. DE 41 26 971 A1 discloses a method and apparatus for disposing of an organic substance. US 5 901 368 A discloses a method for minimizing radioactive waste generated during decontamination processes of radioactively contaminated nuclear reactors. US 5 848 363 A discloses a method for treating an acidic aqueous wastewater generated during the decontamination of a component of a nuclear power plant. EP 1 786 000 A1 discloses a process for conditioning radioactive ion exchange resins.JP H10-204206 A discloses a method for decomposing ion exchange resin. KR 10 2007 0026 965 A discloses a treatment method for persistent organic compounds in radioactive liquid waste. US 2010 / 0320156 A1 discloses a method for oxidizing a substance. JP S63-83696 A discloses a plant for treating liquid radioactive waste. JP H11-231097 A discloses a chemical decontamination method. Disclosure of the inventionTechnical problem

[0011] One aspect of the present invention provides a method for treating radioactive liquid waste, the method having excellently improved the treatment amount and treatment efficiency for radioactive liquid waste.

[0012] Another aspect of the present invention provides a method for treating radioactive liquid waste comprising at least one selected from the group consisting of: an organic decontaminant, an inorganic decontaminant, and a liquid scintillation counter (LSC) liquid waste. Technical solution

[0013] According to one aspect of the present invention, there is provided a method for treating radioactive liquid waste according to claim 1. Beneficial results

[0014] When the radioactive liquid waste treatment method of the present invention is used, decontamination waste liquid during a decontamination process and / or generated liquid scintillation counter liquid waste can be treated with excellent efficiency. Specifically, an organic substance such as oxalic acid; an inorganic substance such as nitric acid, sulfuric acid, hypochlorous acid, and hydrazine; a liquid scintillation material; and the like can be decomposed.

[0015] Also, with a powerful oxidation decomposition effect that cannot be achieved by radiation treatment alone, a radiation melting treatment system capable of completely treating radioactive liquid waste can be established to treat radioactive liquid waste safely and efficiently.

[0016] In addition, since the pH of radioactive liquid waste that can be treated is not limited to acid, alkali and neutral liquid waste can also be treated, thereby improving the accessibility of the process and solving problems such as corrosion of equipment. Short description of the drawings

[0017] The following drawings appended to the specification illustrate preferred examples of the present invention by way of example and, together with the detailed description of the invention given below, serve to enable the technical concepts of the present invention to be further understood, and therefore the present invention should not be interpreted solely with materials in such drawings. Fig. Figure 1 is a graph showing the concentration of oxalic acid over time when the oxalic acid is treated with UV / hydrogen peroxide at pH 3; Fig. Figure 2 is a graph showing the concentration of oxalic acid according to an absorbed dose when the oxalic acid is treated with radiation at pH 3; Fig. 3 is a graph showing the treatment efficiency for oxalic acid according to an absorbed dose when the oxalic acid is treated at pH 9 by adding a metal ion, an oxidizing agent, or a metal ion and an oxidizing agent and then irradiating; Fig. Figure 4 is a graph showing the concentration of oxalic acid according to the absorbed dose when the oxalic acid is treated at pH 9 by adding a metal ion, an oxidizing agent, or a metal ion and oxygen and then irradiated; Fig. Figure 5 is a graph showing the treatment efficiency for oxalic acid according to the absorbed dose when radioactive liquid waste is treated with a metal ion and / or a semiconductor and radiation; Fig. Figure 6 is a graph showing the treatment efficiency for oxalic acid according to the absorbed dose when radioactive liquid waste injected with air is treated with an oxidizer and / or gas (oxygen) and radiation; Fig. Figure 7 is a graph showing the treatment efficiency for hydrazine according to the absorbed dose when radioactive liquid waste containing hydrazine is treated with an oxidizer and / or gas (oxygen) and radiation; Fig. Figure 8 is a graph showing the decomposition efficiency for liquid scintillation counters (LSCs) according to the absorbed dose when liquid waste (pH 3) containing the LSC is treated with a metal ion and / or gas (nitric oxide) and radiation; and Fig. Figure 9 is a graph showing the decomposition efficiency for liquid scintillation counters (LSCs) according to the absorbed dose when liquid waste (pH 7) containing the LSC is treated with a metal ion and / or gas (nitric oxide) and radiation. Mode for carrying out the invention

[0018] A method for treating radioactive liquid waste of the present invention comprises adding a metal ion, an oxidizing agent, and nitrogen oxide to radioactive liquid waste to prepare a pretreatment solution, and irradiating the pretreatment solution with irradiation radiation, wherein the metal ion, the oxidizing agent, and the irradiation dose are as defined in claim 1.

[0019] In the present invention, the 'radioactive liquid waste' is liquid waste containing a radioactive material and includes decontamination waste liquid, liquid scintillation counter liquid waste and the like.

[0020] 'Decontamination liquid waste' refers to liquid waste during a decontamination process generated at a nuclear waste disposal facility, a radiation (radioactivity) facility and the like, and may in particular refer to liquid waste comprising an organic decontaminant and / or an inorganic decontaminant.

[0021] In the present specification, the 'organic decontaminant' may comprise one or more selected from the group consisting of: oxalic acid, citric acid, formic acid, picolinic acid, ethylenediamine-N, N, N', N'-tetraacetic acid (EDTA), gluconic acid, acetic acid, sulfamic acid, and the like. The 'inorganic decontaminant' may comprise one or more selected from the group consisting of: nitric acid, sulfuric acid, hydrochloric acid, hydrazine, and the like.

[0022] The 'liquid scintillation counter liquid waste' is not particularly limited as long as it is known to measure radiation, such as liquid scintillation material, a plastic scintillation material, and the like, and may be, for example, a scintillation material contained in liquid waste due to the use of a liquid scintillation counter (LSC) technology.

[0023] In the present invention, the 'treatment of radioactive liquid waste' refers to reducing the content of at least one of the difficult-to-degrade compositions, such as an organic decontaminant, an inorganic decontaminant, and liquid scintillation material, in radioactive liquid waste, and may ultimately refer to substantially removing them (i.e., reducing the content of difficult-to-degrade compositions such as the above in radioactive liquid waste to approximately 0%).

[0024] The method for treating radioactive liquid waste of the present invention comprises: adding a metal ion, an oxidizing agent, and nitrogen oxide to radioactive liquid waste to prepare a pretreatment solution; and irradiating the pretreatment solution with irradiation radiation, wherein the metal ion, the oxidizing agent, and the irradiation dose are as defined in claim 1.

[0025] When radioactive liquid waste is irradiated with irradiation radiation, an active material such as a hydrated electron, a radical, and a hydrated ion, which are highly reactive, is generated, and the active material can decompose a difficult-to-decompose composition in the radioactive liquid waste, the material being, for example, an organic decontaminant and / or an inorganic decontaminant and / or a liquid scintillation material.

[0026] An active material produced when water is irradiated with irradiation radiation can be represented, for example, by equation 1 below, but is not limited to H 2 O → e - aq , · H, OH, H 2 , H 2 O 2 , H + aq , OH - aq [Equation 1]

[0027] The method for treating radioactive liquid waste of the present invention comprises adding a metal ion, an oxidizer, and nitrogen oxide to radioactive liquid waste prior to irradiation with irradiation radiation to prepare a pretreatment solution. The inventors of the present invention have discovered that when treating radioactive liquid waste, if a metal ion, an oxidizer, and nitrogen oxide are added to the radioactive liquid waste, followed by irradiation with irradiation radiation, there is an enhanced effect (synergy effect) in the treatment efficiency for the radioactive liquid waste compared to a treatment method in which each of them is added followed by irradiation with irradiation radiation, and have accomplished the present invention.

[0028] In the present invention, the 'metal ion' includes an iron ion or a copper ion. For example, the iron ion can exhibit a more excellent effect in terms of the partial decomposition rate of a difficult-to-decompose composition (for example, an organic substance such as oxalic acid; an inorganic substance such as nitric acid, sulfuric acid, hydrochloric acid, and hydrazine; an organic scintillation material, and the like), and the copper ion can exhibit a more excellent effect in terms of the rate of complete oxidation of oxalic acid and an organic material such as liquid scintillation counters to carbon dioxide and the decomposition of an inorganic material such as hydrazine, nitric acid, sulfuric acid, and hydrochloric acid.

[0029] When the metal ion is added to the radioactive liquid waste and then irradiated with radiation, there may be an effect for treating the radioactive liquid waste by activating the metal ion through a mechanism such as Equation 2 below. However, the reaction mechanism of the present invention is not limited to this. (When irradiation is performed with irradiation radiation) H 2 O → e - aq , H, OH, H 2 , H 2 O 2 , H + aq , OH - aq M 2+ + H 2 O 2 → M 3+ + OH + OH - (Here M 2+ the metal ion, for example Fe 2+ or Cu 2+ ) [Equation 2]

[0030] According to one aspect, the metal ion may be contained in the radioactive liquid waste, in which case the above effect can be achieved due to the metal ion in the radioactive liquid waste. Likewise, the metal ion may be additionally added, taking into account the content of the metal ion in the radioactive liquid waste. The added metal ion may be of the same type or a different type than the metal ion already present in the radioactive liquid waste, but is not limited thereto.

[0031] When the metal ion is present in the radioactive liquid waste and / or when the metal ion is introduced into the radioactive liquid waste, it is preferable that the concentration of the metal ion present in the radioactive liquid waste before irradiation with irradiation radiation is, for example, 1-100 mM, particularly 2-50 mM. If the content of the metal ion in the radioactive liquid waste before irradiation with irradiation radiation is less than 1 mM, there may be a problem that the treatment efficiency for a difficult-to-degrade composition may be deteriorated. If the content of the metal ion is higher than 100 mM, the ion may act more as a radical scavenger, so there is a problem that the decomposition performance for a difficult-to-degrade composition may be deteriorated.

[0032] In the present invention, the 'oxidizing agent' comprises one or more selected from the group consisting of a peroxydisulfate anion (S 2 O 8 2- ) and a salt thereof. With a view to improving the treatment efficiency of radioactive liquid waste, a compound capable of forming a sulfate radical is used as the oxidizing agent. Specifically, the 'salt' may comprise one or more selected from the group consisting of potassium salt, sodium salt, and ammonium salt.

[0033] The sulfate radical can be generated, for example, as shown in Equation 3 below, but is not limited to this. (When irradiation is performed with irradiation radiation) 2e - aq + S 2 O 8 2- → 2SO 4 · - e - aq + HSO 5 - → SUN 4 · - + OH- [Equation 3]

[0034] Furthermore, in the present invention, when a semiconductor is irradiated, the semiconductor enters an excited state, and since electron transfer is facilitated in the excited state, an effect of excellently improving the production amount of hydroxyl radicals in the radioactive liquid waste can be exhibited. Consequently, an effect such as improving the treatment amount of the radioactive liquid waste can be achieved, thereby reducing treatment costs.

[0035] As the semiconductor, for example, one or more selected from the group consisting of silicon, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, yttrium, zirconium, molybdenum, lanthanum, cerium, tantalum, and an oxide thereof can be used, although not limited thereto. In particular, the semiconductor can be one doped with an organic element or an inorganic element, although not limited thereto. For example, one or more selected from the group consisting of transition metal oxides such as titanium dioxide, zinc oxide, and copper oxide can be used.

[0036] When radioactive liquid waste is treated according to one aspect of the present invention, a method of adding a metal ion and an oxidizing agent to radioactive liquid waste followed by irradiation with irradiation radiation can exhibit an enhanced effect (synergistic effect) in treatment efficiency for the radioactive liquid waste compared to a method of separately adding a metal ion and an oxidizing agent followed by irradiation with irradiation radiation.

[0037] In particular, in the present invention, by irradiating a pretreatment solution comprising both an iron ion, a copper ion or a mixture thereof and a composition capable of forming a sulfate radical upon irradiation, a maximizing effect for the efficiency in the treatment of radioactive liquid waste can be achieved.

[0038] In particular, the inventors of the present invention have confirmed that the treatment efficiency of the radioactive liquid waste is more improved when the molecular equivalent ratio of the metal ion and the oxidizing agent in the pretreatment solution containing a metal ion and an oxidizing agent is 1:1 to 1:10 (metal ion:oxidizing agent), preferably 1:1.5 to 1:8, more preferably 1:2 to 1:6, and most preferably 1:2.5 to 1:5. Furthermore, according to one aspect of the present invention, when radioactive liquid waste is treated, a method of adding a metal ion and nitrogen oxide followed by irradiation with irradiation radiation can exhibit a synergistic effect in the decomposition efficiency of a difficult-to-decompose composition compared with a method of separately adding a metal ion and nitrogen oxide followed by irradiation with irradiation radiation.

[0039] In particular, the molar equivalent ratio of the metal ion and nitrogen oxide in the pretreatment solution containing a metal ion and nitrogen oxide can be 1:0.001 to 1:100 (metal ion: nitrogen oxide). In one embodiment, when the metal ion and nitrogen oxide were contained in a molar equivalent ratio of 1:63, it was confirmed that the treatment efficiency for radioactive liquid waste was significantly improved.

[0040] For example, when nitrogen oxide was added to the pretreatment solution, followed by irradiation with irradiation radiation, the nitrogen oxide dissolved in water rapidly reacted with a hydrated electron generated due to irradiation with irradiation radiation to generate nitrogen gas and a hydroxyl radical (Equation 4). This suppressed the reaction between the hydrated electron and the hydroxyl radical, leading to the improvement in the treatment efficiency of radioactive liquid waste due to the hydroxyl radical. However, the mechanism of the effect of adding nitrogen oxide to improve the treatment efficiency is not limited to this. e - aq + N 2 O + H 2 O → OH - + OH + N 2 [Equation 4]

[0041] As mentioned above, when a metal ion, an oxidizer, and nitrogen oxide were added to radioactive liquid waste to prepare a pretreatment solution, and the pretreatment solution was then irradiated with radiation, it was confirmed that the treatment efficiency of the radioactive liquid waste was significantly improved compared to a case where a metal ion, an oxidizer, and nitrogen oxide were added separately, followed by irradiation with radiation. However, a combination of the metal ion, the oxidizer, and nitrogen oxide is not limited to the above specific examples.

[0042] In the present invention, irradiation with irradiation radiation can be performed, for example, by irradiating with one or more selected from the group consisting of: an electron beam, an alpha ray, a beta ray, a gamma ray, an X-ray, a neutron beam, although not limited thereto. Preferably, irradiation with irradiation radiation can be performed with an electron beam, a gamma ray, or an X-ray. The irradiation with irradiation radiation is performed at an irradiation dose of 1-50 kGy based on an absorbed dose. From the viewpoint of reducing energy consumption and improving treatment efficiency, irradiation with irradiation radiation is performed at an irradiation dose of 1-50 kGy.

[0043] In one embodiment, the inventors of the present invention confirmed that when irradiation with radiation based on an absorbed dose is performed with an irradiation dose of 5-25 kGy, the synergistic effect of co-adding a metal ion and an oxidizer to the radioactive waste solution can be more excellent. Therefore, when a metal ion and an oxidizer are co-added to the radioactive waste liquid, it is most preferable that irradiation with radiation based on an absorbed dose be performed with an irradiation dose of 5-25 kGy.

[0044] In the present invention, the pH of the pretreatment solution before irradiation with irradiation radiation is not particularly limited, but may be, for example, 2 to 13.

[0045] Since the pH of radioactive liquid waste generated in a nuclear power plant is typically 3 or less, studies have mostly been conducted on radioactive liquid waste treatment methods with a pH of 3 or less. However, as described above, according to the radioactive liquid waste treatment method of the present invention, the method comprising adding a combination of at least two of a metal ion, air, oxygen, or nitrogen oxide, and a semiconductor to radioactive liquid waste, followed by irradiation with irradiation radiation, can demonstrate excellent treatment efficiency for radioactive liquid waste without being limited to the pH of the radioactive liquid waste.

[0046] In particular, the method for treating radioactive liquid waste according to the present invention is capable of treating radioactive liquid waste having a pH of 2 to 14. In particular, the method can exhibit excellent treatment efficiency for radioactive liquid waste having a pH of 7 to 10 and a pH of 8 to 9.5, thereby having an advantage of solving the corrosion problem in a treatment apparatus.

[0047] Hereinafter, examples and the like will be described in detail to facilitate understanding of the present invention. However, examples according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as limited to the examples described below. Examples of the present invention are provided to more fully describe the present invention to those skilled in the art to which the invention pertains. Comparative Example Experiment 1. Comparison of UV / hydrogen peroxide treatment and irradiation treatment (pH 3)

[0048] To treat an organic acid and an oxalic acid used as a complexing agent in a decontamination process at a nuclear power plant, a UV / hydrogen peroxide process and a radiation decomposition processing adding a metal ion and an oxidizer were used.

[0049] In the present experiment, an aqueous solution of oxalic acid with a concentration of 10 mM was prepared, and then its pH was adjusted to 3 to prepare a solution to be treated. A copper ion was used as the metal ion, and persulfate was used as the oxidizing agent. The molar equivalent of the copper ion and persulfate was 1:5.

[0050] A 1 kW medium-pressure ultraviolet lamp was used as UV, and 20 mM hydrogen peroxide was added. UV irradiation was carried out for 5 hours under a temperature condition of 35–55°C, and irradiation with irradiation radiation was carried out based on an absorbed dose with an irradiation dose of 0, 10, 20, 30, and 50 kGy. The results are shown in Fig. 1 and Fig. 2 shown.

[0051] If the oxalic acid is referring to Fig. 1 was decomposed by the UV / hydrogen peroxide process at pH 3, the oxalic acid was decomposed to 10 mM, 3.0 mM (decomposition rate 69.8%), 2.3 mM (77%), 1.7 mM (82.7%), 1.2 mM (88%) and 1.0 mM (90.4%) at a duration of 0, 1, 2, 3, 4 and 5 hours, respectively, with the maximum treatment efficiency of 90.4% at a duration of 5 hours.

[0052] If the oxalic acid is referring to Fig. 2 was decomposed by irradiation with irradiation radiation at pH 3, the oxalic acid was decomposed to 10 mM, 8.7 mM (decomposition rate 16.7%), 6.8 mM (36.5%), 3.2 mM (69.5%), 1.7 mM (83.4%) and 0.8 mM (92.2%) at irradiation doses of 0, 10, 20, 30 and 50 kGy, respectively, with the maximum treatment efficiency of 92.2% being shown at the irradiation dose of 50 kGy.

[0053] As such, it was confirmed that the treatment efficiency for the radioactive liquid waste was excellent when the irradiation process was used compared to that using the UV / hydrogen peroxide process.

[0054] Example experiment 1. Verification of the synergistic effect of the co-addition of metal ion and oxidant during irradiation treatment

[0055] To treat an organic acid and oxalic acid, which are used as a complexing agent in a decontamination process at a nuclear power plant, an electron beam was used, and the irradiation dose was 5, 10, 20, and 30 kGy. The concentration of oxalic acid used in the present experiment was 2 mM, and its pH was adjusted to 9.

[0056] A batch treated only with irradiation radiation (reference treatment example 1), a batch to which 2 mM Fe(II) was added (reference treatment example 2), a batch to which 5 mM S 2 O 8 2- were added (Reference Treatment Example 3) and a batch containing 2 mM Fe(II) and 5 mM S 2 O 8 2-were added (Reference Treatment Example 4) were used for the experiment. The treatment efficiency (%) for oxalic acid was calculated by subtracting the residual oxalic acid content after irradiation with irradiation radiation from the oxalic acid content before irradiation with irradiation radiation, and is shown in Fig. 3. In addition, to verify the synergistic effect of Reference Treatment Example 4, in which the metal ion and the oxidizing agent were used together, Fig. 3 also shows the result of simply summing the oxalic acid treatment efficiency of each of Reference Treatment Example 2 and Reference Treatment Example 3.

[0057] First, referring to Fig. 3 confirms that when a metal ion, an oxidizing agent, or a mixture thereof was included during irradiation processing, excellent treatment efficiency was shown even at pH 9.

[0058] Furthermore, with reference to Fig. 3 confirms that, compared with a case where either a metal ion or an oxidizer was added to radioactive liquid waste, such as decontamination liquid waste containing oxalic acid, followed by irradiation with irradiation radiation, the treatment efficiency of a case where a metal ion and an oxidizer were all added, followed by irradiation with irradiation radiation was remarkably improved. Furthermore, when an irradiation dose of irradiation radiation was 5-20 kGy, it was confirmed that a case where a metal ion and an oxidizer were all added (Reference Treatment Example 4) exhibited a more excellent treatment effect than cases where a metal ion and an oxidizer were each added (Reference Treatment Examples 2 and 3), by exceeding the simple sum of the treatment efficiency of each.

[0059] Example experiment 2. Verification of the synergistic effect of the co-addition of metal ion and oxygen during radiation treatment

[0060] To treat an organic acid and oxalic acid, which are used as a complexing agent in a decontamination process at a nuclear power plant, an electron beam was used, and the irradiation dose was 5, 10, 20, and 30 kGy. The concentration of oxalic acid used in the experiment was 2 mM, and its pH was adjusted to 9.

[0061] A batch treated only with irradiation radiation (Reference Treatment Example 1), a batch to which 2 mM Fe(II) was added (Reference Treatment Example 2), a batch to which 0.0442 mM oxygen was added (Reference Treatment Example 5), and a batch to which 2 mM Fe(II) and 0.0442 mM oxygen were added (Reference Treatment Example 6) were used for the experiment. The treatment efficiency (%) for oxalic acid was calculated by subtracting the residual oxalic acid content after irradiation radiation from the oxalic acid content before irradiation radiation, and is shown in Fig. 4. In order to further verify the synergistic effect of Reference Treatment Example 6, in which the metal ion and oxygen were used together, Fig. 4 also shows the result of simply summing the oxalic acid treatment efficiency of each of Reference Treatment Example 2 and Reference Treatment Example 5.

[0062] First, referring to Fig. 4 confirms that when a metal ion, oxygen, or a mixture thereof was included during irradiation processing, excellent treatment efficiency was shown even at pH 9.

[0063] Furthermore, with reference to Fig. Figure 4 confirms that, compared with a case where either a metal ion or oxygen was added to the radioactive liquid waste, followed by irradiation with irradiation radiation, the treatment efficiency of a case where a metal ion and oxygen were all added, followed by irradiation with radiation, was remarkably improved. Furthermore, when the radiation dose was 5-50 kGy, it was confirmed that a case where a metal ion and oxygen were all added (Reference Treatment Example 6) showed a more excellent treatment effect than cases where a metal ion and oxygen were each added (Reference Treatment Examples 2 and 5), exceeding the simple sum of the treatment efficiency of each.

[0064] Example experiment 3. Verification of the effect of introducing air, metal ion and semiconductor during irradiation treatment

[0065] To treat an organic acid and oxalic acid, which are used as a complexing agent in a decontamination process at a nuclear power plant, a gamma ray was used, and the irradiation dose was 5, 10, and 30 kGy. The concentration of oxalic acid used in the present experiment was 2 mM, and its pH was 2.5. Air was introduced for 20 minutes through substitution and dissolution.

[0066] 1 mM copper ion and 1 mM titanium dioxide were added as a metal ion and as a semiconductor, respectively, to conduct the experiment. Specifically, a batch in which the copper ion was added to radioactive liquid waste into which air was injected (Reference Treatment Example 7), a batch in which titanium dioxide was added to radioactive liquid waste into which air was injected (Reference Treatment Example 8), and a batch in which the copper ion and titanium dioxide were added to radioactive liquid waste into which air was injected (Reference Treatment Example 9) were used for the experiment. The treatment efficiency (%) for oxalic acid was calculated by subtracting the residual oxalic acid content after radiation irradiation from the oxalic acid content before radiation irradiation, and is shown in Fig. 5 shown.

[0067] To verify the synergistic effect of Reference Treatment Example 9, in which the metal ion and the semiconductor were treated together, Fig. 5 Values ​​obtained by summing the treatment efficiency of each Reference Treatment Example 7 and Reference Treatment Example 8 in the graph.

[0068] When a gamma irradiation dose was 5, 10 and 30 kGy, the oxalic acid was measured as in Fig. 5, in the case of Reference Treatment Example 7, the oxalic acid was removed by 3.2%, 7.8%, and 15.9%, respectively, and the oxalic acid was removed by 4.5%, 28.8%, and 50.5%, respectively, in the case of Reference Treatment Example 8. The oxalic acid was removed by 51.7%, 59.4%, and 85.0%, respectively, in the case of Reference Treatment Example 9.

[0069] Example experiment 4. Verification of the effect of supplying air, oxidant and oxygen during irradiation treatment

[0070] To treat an organic acid and oxalic acid, which are used as a complexing agent in a decontamination process at a nuclear power plant, a gamma ray was used, and radiation irradiation was carried out at irradiation doses of 5, 10, and 30 kGy. The concentration of oxalic acid used in the present experiment was 2 mM and its pH was 2.5. Air was introduced for 20 minutes through substitution and dissolution.

[0071] 1 mM persulfate was added as an oxidizing agent, and 0.04 mM oxygen was added to conduct the experiment. Specifically, a batch in which persulfate was added to radioactive liquid waste into which air was fed (Reference Treatment Example 10), a batch in which oxygen was added to radioactive liquid waste into which air was fed (Reference Treatment Example 11), and a batch in which the persulfate and oxygen were added to the radioactive liquid waste into which air was fed (Reference Treatment Example 12) were used for the experiment. The treatment efficiency (%) for oxalic acid was calculated by subtracting the residual oxalic acid content after radiation irradiation from the oxalic acid content before radiation irradiation, and is shown in Fig. 6 shown.

[0072] To verify the synergistic effect of Reference Treatment Example 12, in which oxidant and oxygen were treated together, Fig. 6 Values ​​obtained by summing the treatment efficiency of each Reference Treatment Example 10 and Reference Treatment Example 11 in the graph.

[0073] When a gamma irradiation dose was 5, 10 and 30 kGy, the oxalic acid was measured as in Fig. 6, in the case of Reference Treatment Example 10, the oxalic acid was removed by 0.4%, 1.4%, and 5.3%, respectively, and the oxalic acid was removed by 10.0%, 12.7%, and 27.6%, respectively, in the case of Reference Treatment Example 11. The oxalic acid was removed by 28.3%, 35.7%, and 74.1%, respectively, in the case of Reference Treatment Example 12.

[0074] Example experiment 5. Verification of the effect of feeding oxidant and oxygen during irradiation treatment

[0075] To treat hydrazine (N2H4), used as an inorganic decontamination agent in a decontamination process at a nuclear power plant, an electron beam was used, and the irradiation dose was 5, 10, and 30 kGy. The concentration of hydrazine used in the present experiment was 40 mM, and its pH was 3.

[0076] 20 mM persulfate (PDS) was added as an oxidizing agent, and 0.04 mM oxygen was added to conduct the experiment. Specifically, a batch in which persulfate was added to radioactive liquid waste (Reference Treatment Example 13), a batch in which oxygen was added to radioactive liquid waste (Reference Treatment Example 14), and a batch in which persulfate and oxygen were added to radioactive liquid waste (Reference Treatment Example 15) were used for the experiment. The treatment efficiency (%) for hydrazine was calculated by subtracting the residual hydrazine content after radiation irradiation from the hydrazine content before radiation irradiation, and is shown in Fig. 7 shown.

[0077] To verify the synergistic effect of Reference Treatment Example 15, in which the oxidant and oxygen were treated together, Fig. 7 Values ​​obtained by summing the treatment efficiency of each of Reference Treatment Example 13 and Reference Treatment Example 14 in the graph.

[0078] When an electron beam irradiation dose was 5, 10 and 30 kGy, the hydrazine was used as in Fig. 7, in the case of Reference Treatment Example 13, the hydrazine was removed by 14.3%, 17.0%, and 28.6%, respectively, and the hydrazine was removed by 5.1%, 4.8%, and 17.0%, respectively, in the case of Reference Treatment Example 14. The hydrazine was removed by 35.4%, 40.4%, and 53.0%, respectively, in the case of Reference Treatment Example 15.

[0079] Example experiment 6. Verification of the synergistic effect of metal ions, oxidant, and nitric oxide during irradiation treatment (pH 3)

[0080] To treat liquid waste, the liquid scintillation counter (CarboSorb E and Permaflour E +A gamma ray was used for the irradiation of a liquid waste containing scintillation counter (LSC) (from PerkinElmer Co. were mixed 1:1 for use). The total organic carbon (TOC) of the liquid waste containing liquid scintillation counter (LSC) used in the present experiment was 45-60 mg / L, and its pH was adjusted to 3 using 0.1 N nitric acid.

[0081] 1 mM Fe 2+ was added as a metal ion and N 2 O was introduced at a rate of 0.1 MPa / 10 ml for 20 minutes. 1 mM persulfate was added as an oxidant.

[0082] Specifically, a batch in which only the metal ion was added to the liquid scintillation counter (LSC) liquid waste (Reference Treatment Example 16), a batch in which the oxidant and nitrogen oxide were added to the liquid scintillation counter (LSC) liquid waste (Reference Treatment Example 17), and a batch in which the metal ion, the oxidant, and nitrogen oxide were added to the liquid scintillation counter (LSC) liquid waste (Treatment Example 18) were used for the experiment. The treatment efficiency (%) for liquid scintillation counter (LSC) liquid waste was calculated by subtracting the total organic carbon (TOC) concentration of the liquid scintillation counter (LSC) liquid waste after radiation irradiation from that of its total organic carbon (TOC) concentration before radiation irradiation, and is shown in Fig. 8 shown.

[0083] To verify the synergistic effect of Treatment Example 18, in which the metal ion, the oxidizing agent and nitrogen oxide were treated together, Fig. 8 Values ​​obtained by summing the treatment efficiency of each Reference Treatment Example 16 and Reference Treatment Example 17 in the graph.

[0084] When a gamma irradiation dose was 5, 10 and 30 kGy, the treatment efficiency was as in Fig. 8, in the case of Reference Treatment Example 16, the treatment efficiency was 3.7%, 6.6%, and 14.2%, respectively, and the treatment efficiency in the case of Reference Treatment Example 17 was 6%, 18.4%, and 37.1%, respectively. In the case of Treatment Example 18, the treatment efficiency was 22.1%, 34.6%, and 73.9%, respectively.

[0085] Example experiment 7. Verification of the synergistic effect of metal ions, oxidizer, and nitric oxide during irradiation treatment (pH 7)

[0086] The experiment was carried out in the same way as in Example Experiment 6, except that liquid scintillation counter (LSC) waste with a pH of 7 was used and 1 mM Cu 2+ when a metal ion was added, and the result is in Fig. 9. Specifically, a batch in which only the metal ion was added to the liquid scintillation counter (LSC) liquid waste (Reference Treatment Example 19), a batch in which the oxidant and nitrogen oxide were added to the liquid scintillation counter (LSC) liquid waste (Reference Treatment Example 20), and a batch in which the metal ion, the oxidant, and nitrogen oxide were added to the liquid scintillation counter (LSC) liquid waste (Treatment Example 21) were used for the experiment.

[0087] When a gamma irradiation dose was 5, 10 and 30 kGy, the treatment efficiency was as in Fig.9, in the case of Reference Treatment Example 19, the treatment efficiency was 0%, and in the case of Reference Treatment Example 20, the treatment efficiency was 28.1%, 35.7%, and 49.4%, respectively. In the case of Treatment Example 21, the treatment efficiency was 29.5%, 48.4%, and 89.8%, respectively.

Claims

[1] A process for treating radioactive liquid waste, the process comprising: Adding a metal ion, an oxidizer, and nitrogen oxide to radioactive liquid waste to produce a pretreatment solution; and Irradiating the pretreatment solution with irradiation radiation, wherein the metal ion comprises an iron ion or a copper ion, wherein the oxidizing agent comprises one or more selected from the group consisting of a peroxydisulfate anion (S 2 O 8 2- ) and a salt thereof, wherein an irradiation dose of the irradiation radiation based on an absorbed dose is 1 to 50 kGy. [2] The method according to claim 1, wherein the molar equivalent ratio of the metal ion and the oxidizing agent in the pretreatment solution is 1:1 to 1:

10. [3] The process according to claim 2, wherein the molar equivalent ratio of the metal ion and the oxidizing agent is 1:2 to 1:

5. [4] The method according to claim 1, wherein the irradiation radiation is one or more selected from the group consisting of an electron beam, an alpha ray, a beta ray, a gamma ray, an X-ray, and a neutron beam. [5] The method of claim 1, wherein the pH of the radioactive liquid waste is 2 to 13. [6] The method of claim 1, wherein the radioactive waste liquid comprises at least one persistent composition selected from the group consisting of an organic decontaminant, an inorganic decontaminant, and liquid scintillation counter liquid waste, and wherein treating the radioactive waste liquid comprises removing the persistent composition. [7] The method of claim 6, wherein the organic decontaminant is selected from the group consisting of oxalic acid, citric acid, formic acid, picolinic acid, ethylenediamine-N, N, N', N'-tetraacetic acid (EDTA), gluconic acid, acetic acid, sulfamic acid. [8] The method of claim 6, wherein the inorganic decontaminant is selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, hydrazine.

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