Radioactive liquid waste treatment method and radioactive liquid waste treatment system

Abstract

A radioactive waste liquid treatment method and radioactive waste liquid treatment system are provided that can treat alpha nuclides, beta nuclides, and gamma nuclides with a minimum required equipment configuration. [Solution] A method for treating radioactive liquid waste involves adding a powder or a slurry containing the powder that adsorbs β and γ nuclides to radioactive liquid waste containing α, β, and γ nuclides so that the pH of the waste is above a predetermined level. Also, a radioactive liquid waste treatment system is a radioactive liquid waste treatment system that removes α, β, and γ nuclides from radioactive liquid waste containing α, β, and γ nuclides, and includes a radionuclide removal device 15 that adds a powder or a slurry containing the powder that adsorbs β and γ nuclides to the radioactive liquid waste so that the pH of the waste is above a predetermined level.

Description

[Technical Field]

[0001] The present invention relates to a method and system for treating radioactive liquid waste. [Background technology]

[0002] As an example of a contaminated water treatment facility and method that can efficiently treat contaminated water containing radioactive materials while suppressing the amount of secondary waste, Patent Document 1 describes that the facility and method include a radiation measurement mechanism that measures the radionuclide concentration in the contaminated water, a water quality measurement mechanism that measures water quality information including the amount of ions coexisting in the contaminated water, a pretreatment mechanism that performs pretreatment of the contaminated water, a plurality of radionuclide removal mechanisms that remove radionuclides from the contaminated water, and a control unit that selects the mechanism required for treating the contaminated water from the pretreatment mechanism and the plurality of radionuclide removal mechanisms based on the measurement results of the radiation measurement mechanism and the water quality measurement mechanism. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-118283 Summary of the Invention [Problem to be solved by the invention]

[0004] Radioactive organic wastes, such as filter sludge containing cellulose-based filter aids and ion exchange resins, generated from reactor coolant purification systems, fuel pool coolant purification systems, etc., of nuclear power plants are stored for long periods in storage tanks. These radioactive organic wastes are generated regularly during the operation of nuclear power plants.

[0005] In order to secure storage space for radioactive organic waste, volume reduction treatment is carried out to efficiently reduce the volume of radioactive organic waste being stored, as disclosed in Patent Document 1, for example.

[0006] The technology described in Patent Document 1 involves removing radioactive liquid waste containing α, β, and γ radionuclides using an adsorbent, recovering and concentrating the waste adsorbent and colloid after nuclide adsorption by cross-flow filtration, and reducing the volume by coagulating and precipitating the waste adsorbent and dehydrating the supernatant water.

[0007] In the above-mentioned treatment, there is a possibility that radioactive liquid waste containing high doses of radioactive nuclides will be treated, and therefore it is desirable to minimize maintenance by simplifying the equipment. To achieve this, it is necessary to reduce the concentrations of α, β, and γ nuclides in the radioactive liquid waste to below a specified level using the minimum necessary equipment configuration. However, since the same ionic nuclides may have different valences or may exist in different colloidal forms, it is necessary to perform removal treatments separately for each, which makes the treatment equipment complex.

[0008] In order to solve the above-mentioned problems, the present invention provides a radioactive liquid waste treatment method and radioactive liquid waste treatment system that can treat alpha nuclides, beta nuclides and gamma nuclides with the minimum necessary equipment configuration. [Means for solving the problem]

[0009] The present invention includes a number of means for solving the above-mentioned problems. One example is to add a powder that adsorbs β and γ nuclides or a slurry containing said powder to radioactive liquid waste containing α, β, and γ nuclides so that the pH is equal to or higher than a predetermined value.

[0010] Another example is a radioactive waste treatment system that removes α, β, and γ nuclides from radioactive waste containing the α, β, and γ nuclides, and is equipped with a removal device that adds a powder that adsorbs β and γ nuclides or a slurry containing the powder to the radioactive waste so that the pH of the radioactive waste is equal to or higher than a predetermined value. [Effects of the Invention]

[0011] According to the present invention, alpha, beta, and gamma nuclides can be treated with a minimum necessary equipment configuration. Problems, configurations, and effects other than those described above will become clear from the following description of the examples. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a flowchart showing the steps of a method for treating radioactive liquid waste according to a first embodiment. [Figure 2] 1 is a diagram showing an example of the configuration of a radioactive liquid waste treatment system according to a first embodiment. [Figure 3] FIG. 2 is a diagram showing a detailed configuration of the radioactive waste liquid treatment system of the first embodiment, from a radionuclide concentration measuring device to a radionuclide removal device. [Figure 4] FIG. 1 is a graph showing the relationship between the pH after addition of an adsorbent and the amount of cesium sorbed by the adsorbent. [Figure 5] FIG. 1 is a graph showing the relationship between the pH after addition of an adsorbent and the amount of americium sorbed by the adsorbent. [Figure 6] FIG. 1 shows the potential-pH diagram of americium. [Figure 7] FIG. 1 is a graph showing the liquid-solid ratio of the adsorbent and the pH after addition of the adsorbent. DETAILED DESCRIPTION OF THE INVENTION

[0013] The radioactive liquid waste treatment method and radioactive liquid waste treatment system according to the embodiments of the present invention will be described below with reference to text and drawings. However, the structures, materials, and other specific configurations shown in the present invention are not limited to the embodiments and examples described here, and can be appropriately combined and improved within the scope that does not change the gist of the present invention.

[0014] Furthermore, elements not directly related to the present invention may be omitted for convenience of illustration. Furthermore, in the drawings used in this specification, identical or similar reference numerals may be used to denote identical or corresponding components, and repeated explanations of these components may be omitted.

[0015] The radioactive waste liquid treatment method and radioactive waste liquid treatment system capable of treating alpha, beta and gamma nuclides with the minimum necessary equipment configuration described above can be achieved as follows.

[0016] First Embodiment A first embodiment of a method for treating radioactive liquid waste and a radioactive liquid waste treatment system according to the present invention will be described with reference to Figures 1 to 6. The method for treating radioactive liquid waste and the radioactive liquid waste treatment system according to this embodiment are applied to the treatment of radioactive waste generated in nuclear power plants.

[0017] First, the details of each of steps S1 to S7 of the method for treating radioactive liquid waste of this embodiment will be described with reference to Fig. 1. Fig. 1 is a flow chart showing the procedure of the method for treating radioactive liquid waste of the first embodiment.

[0018] In a nuclear power plant, for example, a boiling water nuclear power plant currently in operation, fuel assemblies are loaded into the reactor core within the reactor pressure vessel, and spent fuel assemblies are stored in a fuel storage pool. The fuel rods of these fuel assemblies are provided with cladding tubes.

[0019] If the cladding tube were to break, the nuclear fuel material (including alpha nuclides such as uranium, plutonium, neptunium, americium, and curium) and radioactive nuclides (including strontium, the source of beta nuclides, and cesium, the gamma nuclides) in the fuel rods would leak into the cooling water in the reactor pressure vessel and the cooling water in the fuel storage pool. Radioactive nuclides that leak into the cooling water in the reactor pressure vessel are removed by ion exchange resins in the purification device of the reactor coolant purification system. Radioactive nuclides that leak into the cooling water in the fuel storage pool are also removed by ion exchange resins in the purification device of the fuel pool coolant purification system.

[0020] Filter sludge (radioactive organic waste) containing cellulose-based filter aids and ion exchange resins, which is generated from the reactor coolant purification system and fuel pool coolant purification system of a boiling water nuclear power plant, is stored for a long period of time in a high-dose resin storage tank 2 (see Figure 2).

[0021] After a predetermined storage period has elapsed, the radioactive organic waste stored in the high-dose resin storage tank 2 is removed from the high-dose resin storage tank 2. The radioactive organic waste containing the cation exchange resin removed from the high-dose resin storage tank 2 is subjected to a first cleaning step (crud dissolution step) S1 shown in FIG.

[0022] In the first cleaning step S1, an aqueous solution of a reducing organic acid (e.g., an aqueous solution of oxalic acid) is brought into contact with the radioactive organic waste. The organic acid contained in this aqueous solution dissolves crud such as iron oxide contained in the radioactive organic waste. Radionuclides such as cobalt-60 contained in the crud are transferred into the organic acid aqueous solution as the crud is dissolved.

[0023] The organic acid used in the first cleaning step S1 is mainly composed of carbon, hydrogen, oxygen, and nitrogen. Therefore, by using an organic acid in the first cleaning step S1, when the organic acid aqueous solution generated as cleaning waste liquid in the first cleaning step S1 is subjected to oxidation treatment (waste liquid decomposition step S4 described below) using, for example, ozone, no nonvolatile residue is generated in the waste liquid. As the organic acid, it is desirable to use one or more selected from, for example, formic acid, oxalic acid, acetic acid, and citric acid.

[0024] The radioactive organic waste that has been subjected to the first cleaning step S1 and from which the crud has been dissolved is subjected to a second cleaning step (radionuclide elution step) S2.

[0025] In this second cleaning step S2, an aqueous solution of an organic acid salt is brought into contact with the radioactive organic waste in which the crud has been dissolved, and the radioactive nuclides, such as alpha nuclides, adsorbed to the radioactive organic waste are eluted by the organic acid salt contained in the aqueous solution.

[0026] The organic acid salt used in the second cleaning step S2 is preferably an organic acid salt that dissociates in the aqueous solution to produce cations that are more easily adsorbed by the cation exchange resin than hydrogen ions. In other words, the organic acid salt is preferably one whose main constituent elements are carbon, hydrogen, oxygen, and nitrogen, and which does not produce nonvolatile residues in the wastewater when the organic acid salt aqueous solution, which is the cleaning wastewater after the second cleaning step S2, is subjected to oxidation treatment (wastewater decomposition step) S4, for example, using ozone. As the organic acid salt, for example, ammonium salts, barium salts, or cesium salts of formic acid, oxalic acid, acetic acid, or citric acid are preferably used. Hydrazine formate may also be used as the organic acid salt.

[0027] Ammonium salts are decomposed into nitrogen gas and water by oxidation, which reduces the amount of radioactive waste generated compared to barium and cesium salts. Ammonium, barium, or cesium salts of formic acid, oxalic acid, acetic acid, or citric acid dissociate in aqueous solution to form NH4 + , Ba 2+ or Cs + NH4 + , Ba 2+ or Cs + is a cation that is more easily adsorbed by a cation exchange resin than a hydrogen ion.

[0028] The radioactive organic waste separated from the eluate of radionuclides in the second washing step S2 is subjected to the incineration and solidification step S3. The radioactive organic waste separated from the eluate of radionuclides is transferred to an incineration facility, where it is incinerated. The ash produced by the incineration is then solidified in a solidification vessel using a solidifying agent such as cement.

[0029] The organic acid aqueous solution (clad dissolved solution) containing dissolved components of the crud, which is generated as a cleaning waste liquid in the first cleaning step S1, is subjected to a waste liquid decomposition step (a step S4 for decomposing either an organic acid or an organic acid salt). The organic acid aqueous solution containing eluted radionuclides such as alpha nuclides, which is generated as a cleaning waste liquid in the second cleaning step S2, is also subjected to the waste liquid decomposition step S4.

[0030] In the waste liquid decomposition step S4, an oxidizing agent such as ozone or hydrogen peroxide is aerated into an aqueous solution of an organic acid or an aqueous solution of an organic salt, and the organic acid or organic salt is decomposed by the oxidizing action of the oxidizing agent.

[0031] After the organic acid or organic acid salt is decomposed in the waste liquid decomposition step S4, the α nuclide concentration, β nuclide concentration, and γ nuclide concentration are measured for the remaining aqueous solution containing radioactive nuclides (radioactive waste liquid) (radioactive nuclide concentration measurement S5).

[0032] In this radionuclide concentration measurement S5, the radioactive liquid waste may be sampled and measured continuously or intermittently by an analyzer, or may be measured intermittently by a survey meter, or may be measured online.

[0033] Next, in the radionuclide concentration measurement S5, it is determined whether or not any one or more of the α nuclide concentration, β nuclide concentration and γ nuclide concentration is equal to or greater than a predetermined value, and if any one or more concentrations are equal to or greater than a predetermined value, the α, β and γ nuclides are removed so that their concentrations are less than the predetermined value (α, β and γ nuclide removal step S6).

[0034] In this α, β, and γ nuclide removal step S6, a powder or a slurry containing the powder that adsorbs β and γ nuclides is added to the radioactive waste liquid containing α, β, and γ nuclides so that the pH is equal to or higher than a predetermined value. At this time, an alkaline solution in which the powder or slurry has been soaked can be added to the radioactive waste liquid.

[0035] In this case, the alkaline liquid to be injected into the radioactive waste liquid can be inorganic acids (hydrochloric acid, sulfuric acid, nitric acid, etc.), inorganic alkalis (sodium hydroxide, calcium hydroxide, magnesium hydroxide, etc.), organic acids (carboxylic acids, ascorbic acid, etc.), or organic alkalis (ammonium-based, etc.).

[0036] In addition to the addition of powder or slurry, a chemical injection device can be installed to adjust the pH. In this case, the chemicals that can be injected into the radioactive waste liquid include inorganic acids (hydrochloric acid, sulfuric acid, nitric acid, etc.), inorganic alkalis (sodium hydroxide, calcium hydroxide, magnesium hydroxide, etc.), organic acids (carboxylic acids, ascorbic acid, etc.), and organic alkalis (ammonium-based, etc.).

[0037] In addition, since the particle size of the powder or slurry added affects the speed of adsorbent recovery by subsequent filtration, the particle size of the powder or slurry added can be adjusted with an eye toward adsorbent recovery by subsequent filtration.

[0038] In this α, β, and γ nuclide removal step S6, α nuclides and at least one of β and γ nuclides are removed by adding a powder or slurry to the radioactive liquid waste as an adsorbent for radioactive nuclides. That is, by bringing the radioactive liquid waste into contact with the adsorbent, the radioactive nuclides in the radioactive liquid waste are adsorbed by the adsorbent, and the radioactive nuclides are removed from the liquid phase of the radioactive liquid waste.

[0039] The powder as the adsorbent or the powder in the slurry can be, for example, one or more selected from cation exchange resins, Fe oxides, titanic acid compounds, silicic titanic acid compounds, titanate compounds, ferrocyanide compounds, chelating resins, activated carbon, oxine-impregnated activated carbon, zeolite, silica particles, and alumina particles.

[0040] The reference pH, which is equal to or higher than the predetermined pH used in the α, β, and γ nuclide removal step S6, can be determined from the pH at which the target α nuclide precipitates. More preferably, the pH at which the α nuclide precipitates can be determined from the potential-pH diagram of the target α nuclide.

[0041] If the concentrations of all α, β, and γ nuclides measured in the radionuclide concentration measurement S5 are less than the predetermined concentration, the α, β, and γ nuclide removal process S6 may be bypassed and the water may be sent to storage, treatment, and disposal S7.

[0042] After the removal of alpha, beta, and gamma nuclides is complete, the radioactive liquid waste is subjected to a cross-flow filter treatment, a press filter treatment, concentration using an evaporator, flocculation treatment using a flocculant, and dehydration treatment using a dehydrator to separate solids such as waste adsorbent and slurry from the liquid waste from which the radionuclides have been removed. The solids are then solidified using a solidifying agent, and the waste is filled into containers for disposal (storage, treatment, and disposal S7).

[0043] When a flocculant is used in this storage, treatment and disposal step S9, the flocculant can be one or more selected from inorganic flocculants including at least one of aluminum sulfate, polyaluminum chloride, ferric sulfate and ferric chloride, and organic flocculants including at least one of natural polymers and synthetic polymers.

[0044] The waste liquid after the treatment may be circulated and used as washing water in the first washing step S1 and the second washing step S2.

[0045] Next, the configuration of a radioactive liquid waste treatment system according to this embodiment, which is capable of carrying out the above-described method for treating radioactive liquid waste, will be described with reference to Figures 2 to 6. Figure 2 is a diagram showing an example of the configuration of a radioactive liquid waste treatment system according to the first embodiment, Figure 3 is a diagram showing an example of the detailed configuration from the radionuclide concentration measuring device to the radionuclide removal device, Figure 4 is a diagram showing the relationship between the pH after addition of an adsorbent and the amount of cesium sorbed by the adsorbent, Figure 5 is a diagram showing the relationship between the pH after addition of an adsorbent and the amount of americium sorbed by the adsorbent, and Figure 6 is a diagram showing the potential-pH diagram of americium.

[0046] The radioactive waste liquid treatment system 1 shown in FIG. 2 includes a chemical cleaning section 10 that treats radioactive organic waste, and a waste liquid treatment section 19 that treats the cleaning waste liquid (radioactive waste liquid) discharged from the chemical cleaning section 10.

[0047] The chemical cleaning section 10 has a first receiving tank 3, a chemical reaction tank (cleaning tank) 4, a cleaning liquid supply tank 6, an organic acid tank 7, an organic acid salt tank 8, and a transfer water tank 9. A high-dose resin storage tank 2 is provided upstream of the chemical cleaning section 10, and a second receiving tank 11 and incineration equipment 12 are provided below the chemical cleaning section 10 in the drawing. A cement solidification equipment can be provided in addition to or instead of the incineration equipment 12.

[0048] In the chemical cleaning section 10, of the steps shown in FIG. 1, a first cleaning step S1 for dissolving the crud and a second cleaning step S2 for eluting radioactive nuclides from the radioactive organic waste are carried out.

[0049] In the chemical cleaning section 10, an organic waste supply pipe 23 equipped with a transfer pump 22 connects the high-dose resin storage tank 2 and the first receiving tank 3.

[0050] The chemical reaction tank 4 is connected to the first receiving tank 3 by an organic waste transfer pipe 25 equipped with a transfer pump 24. A heating device 5 is arranged around the chemical reaction tank 4.

[0051] The cleaning liquid supply tank 6 is connected to the chemical reaction tank 4 by a cleaning liquid supply pipe 33 to which a transfer pump 32 is attached.

[0052] A return pipe 36 connected to the bottom of the chemical reaction tank 4 and equipped with a transfer pump 34 and a valve 35 is connected to the cleaning liquid supply tank 6 .

[0053] A pipe 29 equipped with a valve 26 is connected to an organic acid tank 7 filled with an aqueous organic acid solution, for example, an aqueous oxalic acid solution, and is connected to the cleaning liquid supply tank 6. The aqueous oxalic acid solution filled in the organic acid tank 7 is a saturated aqueous solution, and the oxalic acid concentration of the aqueous oxalic acid solution is, for example, 0.8 mol / L.

[0054] A pipe 30 equipped with a valve 27 is connected to an organic acid salt tank 8 filled with an aqueous solution of an organic acid salt, for example, an aqueous solution of formic acid hydrazine. The pipe 30 is connected to a pipe 29 downstream of the valve 26 .

[0055] A pipe 31 provided with a valve 28 is connected to a transfer water tank 9 filled with water to be transferred, and the transfer water tank 9 is also connected to a pipe 30 downstream of a valve 27 .

[0056] A pipe 38 equipped with a valve 37 and connected to the bottom of the chemical reaction tank 4 is connected to the second receiving tank 11 .

[0057] The piping connected to the second receiving tank 11 is connected to an incineration facility 12.

[0058] The waste liquid treatment unit 19 includes a waste liquid decomposition device 13, radionuclide concentration measuring devices 14A and 14B, a radionuclide removal device 15, a flocculation device 16, a dehydration device 20, an adsorbent supply device 121, a flocculant supply device 122, and a concentration device 131.

[0059] In the waste liquid treatment unit 19, of the processes shown in Figure 1, from the waste liquid decomposition process S4, which decomposes the organic acid in the organic acid aqueous solution containing the dissolved components of the crud, to the storage, treatment and disposal of the waste adsorbent S7, are carried out.

[0060] A waste liquid supply pipe 40 equipped with a valve 39 is connected to the return pipe 36 between the transfer pump 34 and the valve 35 of the chemical cleaning section 10 on the upstream side, and is connected to the waste liquid decomposition device 13 on the downstream side.

[0061] A pipe 45 equipped with a transfer pump 43 and a valve 44 is connected to the liquid waste decomposition apparatus 13 and the radionuclide removal apparatus 15. This pipe 45 is a supply pipe for the radioactive liquid waste that leads the radioactive liquid waste containing radionuclides to the radionuclide removal apparatus 15 in the above-mentioned method for treating radioactive liquid waste. A radionuclide concentration measuring apparatus 14A and an adsorbent supplying apparatus 121 are connected to this pipe 45.

[0062] The pipe 46 is connected to the radionuclide removal device 15, the concentration device 131, and the flocculation device 16. The flocculation agent supply device 122 is connected to the flocculation device 16.

[0063] A pipe 48 equipped with a transfer pump 47 is connected to the flocculation device 16 and the dehydration device 20 , and a pipe 49 is further connected to the dehydration device 20 and the solidification equipment 21 .

[0064] A pipe 55 is connected to the concentrator 131, which is connected between the transfer pump 34 and the valve 35 of the return pipe 36 of the chemical cleaning unit 10. The filtered water, from which the adsorbent and the slurry containing radionuclides have been separated by filtration in the concentrator 131, returns to the return pipe 36 through the pipe 55. This allows the filtered water to be circulated as circulating water.

[0065] In addition, valves (not shown) are provided upstream of the connection between the return pipe 36 and pipe 55 on each of the pipes 36 and 55 (on the chemical reaction tank 4 side and the concentration device 131 side) to enable switching between water from the chemical reaction tank 4 and filtered water from pipe 55.

[0066] The dehydration device 20 may include, for example, a solid-liquid separator using a cross-flow filter method that uses a membrane with a pore size on the order of μm or less, a solid-liquid separator using a press filter method that performs filtration by pressure, or a solid-liquid separator that performs concentration by an evaporation concentration method that uses an evaporator.

[0067] Similar to the above-described concentrating device 131, the dehydrating device 20 is connected to a pipe 56 that is connected between the transfer pump 34 and the valve 35 of the return pipe 36 of the chemical cleaning section 10. The water from which the radionuclides have been removed by the dehydrating device 20 returns to the return pipe 36 through the pipe 56. This allows the water to be circulated as circulating water.

[0068] Valves (not shown) are provided on the upstream side of each of the pipes 36, 56 (on the chemical reaction tank 4 side and the dehydration device 20 side) from the connection between the return pipe 36 and the pipe 56, so that the water from the chemical reaction tank 4 and the water from the pipe 56 can be switched. In addition, the dehydration device 20 can perform dehydration using the cross-flow filter method, press filter method, etc. described for the concentrator 131.

[0069] There is no limitation on the timing for transferring the radioactive liquid waste from the chemical cleaning unit 10 to the liquid waste treatment unit 19. For example, a sampling valve may be attached to the return pipe 36, and the radioactive liquid waste collected by the sampling valve may be periodically analyzed, so that the radioactive liquid waste may be transferred when the measured concentration of radionuclides reaches a desired concentration.

[0070] Next, details of the configuration around the radionuclide removal device 15 in the waste liquid treatment unit 19 shown in Fig. 2 will be described with reference to Fig. 3. Fig. 3 also shows piping connected to the radionuclide removal device 15 and components (tanks, devices, etc.) installed nearby.

[0071] As shown in Figure 3, the radionuclide removal device 15 is a part that adds powder or a slurry containing powder that adsorbs β and γ nuclides to the radioactive waste liquid so that the pH is equal to or higher than a predetermined value, and has an α, β, and γ nuclide removal device 101, an adsorbent supply device 121, etc., and is composed of a waste liquid treatment tank that contains the radioactive waste liquid sent from the waste liquid decomposition device 13 through piping 45.

[0072] The amount of powder or slurry added to the radioactive liquid waste in this radioactive nuclide removal device 15 can be determined based on the measurement results of the β and γ nuclide concentrations by the radioactive nuclide concentration measuring device 14A, or the measurement results of the β and γ nuclide concentrations in the waste liquid decomposition device 13 or in the upstream stage thereof.

[0073] A radionuclide concentration measuring device 14A that measures the concentrations of alpha, beta, and gamma nuclides in the radioactive waste liquid is connected to pipe 45, which is a supply pipe for radioactive waste liquid located upstream of the alpha, beta, and gamma nuclide removal device 101, and a radionuclide concentration measuring device 14B that measures the concentrations of alpha, beta, and gamma nuclides in the radioactive waste liquid is connected to pipe 46, which is a discharge pipe for radioactive waste liquid located downstream of the alpha, beta, and gamma nuclide removal device 101.

[0074] In addition, the radionuclide concentration measuring devices 14A, 14B can also be configured not to be connected to the waste liquid treatment device 19, but to measure the radionuclide concentration of the sampled radioactive waste liquid, and to reflect the determination result in the amount of adsorbent supplied by the adsorbent supply device 121.

[0075] Furthermore, when the radionuclide concentration is known, the radionuclide concentration measuring devices 14A and 14B do not need to be installed, and furthermore, in addition to the radionuclide concentration, pH measurement, oxidation-reduction potential measurement, etc. may be performed.

[0076] If the radionuclide concentration of the radioactive liquid waste measured by the radionuclide concentration measuring devices 14A, 14B is equal to or lower than a predetermined concentration, the radioactive liquid waste may be returned to the return pipe 36 through the pipe 54 and circulated as circulating water, or may be passed through the pipe 103 to bypass the α, β, γ nuclide removal device 101 and passed through the concentrator 131. The predetermined concentration is, for example, based on the notified concentration.

[0077] As a result of measuring the concentrations of radionuclides in the radioactive liquid waste, if the concentrations of α, β, and γ nuclides are found to be equal to or higher than a predetermined concentration, the radioactive liquid waste is supplied to the α, β, and γ nuclide removal device 101. Before supplying the radioactive liquid waste to the α, β, and γ nuclide removal device 101, the pH of the radioactive liquid waste may be adjusted to control its chemical form.

[0078] In the α, β, γ nuclide removal apparatus 101, an adsorbent is supplied from an adsorbent supply device 121. Then, the radioactive liquid waste is brought into contact with the adsorbent in the α, β, γ nuclide removal apparatus 101. As a result, in the α, β, γ nuclide removal apparatus 101, the α, β, γ nuclides are adsorbed by the adsorbent, and the α, β, γ nuclides are removed from the liquid phase of the radioactive liquid waste.

[0079] In the α, β, γ nuclide removal device 101, the radioactive liquid waste in which the α, β, γ nuclides have been adsorbed by the adsorbent to a concentration below a predetermined level is supplied to the concentrator 131 through the pipe 46. At this time, the radioactive nuclide concentration measuring device 14B is connected to the pipe 46, and it can be confirmed whether the concentrations of the α, β, γ nuclides in the radioactive liquid waste have been removed to a concentration below a predetermined level.

[0080] Here, a test using cesium (Cs) as a representative gamma nuclide will be explained with reference to the relationship between the pH after adsorbent addition and the Cs sorption amount of the beta, gamma nuclide adsorbent in Fig. 4. The example shown in Fig. 4 shows the results when 1000-fold diluted simulated seawater was used as the test liquid, Cs was used as the gamma nuclide, and a silicic acid titanate compound (CST) was used as the beta, gamma nuclide adsorbent.

[0081] As shown in Figure 4, the amount of Cs sorption was similar when the pH after addition of the adsorbent was 7 (neutral) and when it was 10 (alkaline). This confirmed that changing the pH of the radioactive waste liquid from neutral to alkaline did not affect the amount of Cs sorption by the β,γ nuclide adsorbent (CST).

[0082] Next, a test using americium (Am) as a representative alpha nuclide will be explained with reference to the relationship between the pH after adsorbent addition and the amount of Am sorption by the beta, gamma nuclide adsorbent in Figure 5. The example shown in Figure 5 shows the results using 1000-fold diluted simulated seawater as the test solution, Am as the alpha nuclide, and CST as the beta, gamma nuclide adsorbent.

[0083] As shown in Figure 5, when the pH after addition of the adsorbent was 10 (alkaline), the amount of Am sorbed was approximately 1000 times higher than when the pH after addition of the adsorbent was 7 (neutral). This confirmed that Am was sorbed onto the β,γ nuclide adsorbent (CST) by changing the pH of the radioactive waste liquid from neutral to alkaline.

[0084] The mechanism by which Am was sorbed onto CST by changing the pH of radioactive waste liquid from neutral to alkaline will be explained with reference to the potential-pH diagram of Am in Figure 6. As shown in the potential-pH diagram of Am in Figure 6, the form of Am in radioactive waste liquid is Am under conditions of pH < 7. 3+ , 7≦pH<8.5, AmOH 2+ Under conditions of pH 8.5 or less, it becomes Am(OH)3. The amount of Am sorbed by CST is greater under alkaline conditions than under neutral conditions because Am(OH)3 precipitates (colloidal) and is sorbed by CST.

[0085] As described above, Am can be sorbed onto the β,γ nuclide adsorbent (CST) by adding the β,γ nuclide adsorbent under conditions above a predetermined pH (the pH at which the target α nuclide precipitates).

[0086] Therefore, as described above, the reference pH that is equal to or higher than the predetermined pH can be determined from the pH at which the target α nuclide precipitates, and more preferably, the pH at which the α nuclide precipitates can be determined from the potential-pH diagram of the target α nuclide.

[0087] In the method for treating radioactive liquid waste of the present embodiment, radioactive nuclides other than the Am nuclide may also be targeted for removal.

[0088] In addition to americium, the target alpha nuclides include one or more selected from the above, including plutonium, curium, neptunium, and uranium; transition metals such as ruthenium, technetium, and niobium; alkali metals such as cesium; alkaline earth metals such as strontium; rare earths such as cerium; and non-metallic elements such as antimony, tellurium, and halogens such as iodine, carbon, and boron.

[0089] Next, the effects of this embodiment will be described.

[0090] The method for treating radioactive liquid waste according to the first embodiment of the present invention described above involves adding a powder or a slurry containing a powder that adsorbs β and γ nuclides to radioactive liquid waste containing α, β, and γ nuclides so that the pH is equal to or higher than a predetermined value.

[0091] Furthermore, the radioactive waste liquid treatment system of the first embodiment of the present invention is a radioactive waste liquid treatment system that removes alpha nuclides, beta nuclides, and gamma nuclides from radioactive waste liquid containing alpha nuclides, beta nuclides, and gamma nuclides, and is equipped with a radioactive nuclide removal device 15 that adds a powder or a slurry containing a powder that adsorbs beta and gamma nuclides to the radioactive waste liquid so that the pH is a predetermined value or higher.

[0092] This allows alpha nuclides, beta nuclides, and gamma nuclides to be efficiently removed in a single process, making it possible to provide a radioactive waste treatment method and a radioactive waste treatment system that can treat radioactive waste with the minimum necessary equipment configuration.

[0093] Furthermore, by determining the reference pH, which is equal to or higher than a predetermined pH, from the pH at which the target alpha nuclides precipitate, and in particular by determining the pH at which the alpha nuclides precipitate from the potential-pH diagram of the target alpha nuclides, it is possible to realize a process that efficiently removes a large number of alpha nuclides as well.

[0094] Furthermore, by adding an alkaline solution in which powder or slurry has been soaked to the radioactive waste liquid, removal can be achieved while easily maintaining a predetermined pH or higher.

[0095] Furthermore, by injecting a chemical agent in addition to the powder or slurry, it is easy to maintain a predetermined pH or higher, that is, to maintain a high removal efficiency, and the removal efficiency can be further improved.

[0096] Furthermore, by using an inorganic acid, inorganic alkali, organic acid, or organic alkali as the alkaline solution or chemical, it is possible to maintain a predetermined pH or higher using materials that are inexpensive and easy to handle.

[0097] Furthermore, by using one or more powders selected from the group consisting of cation exchange resins, Fe oxides, titanic acid compounds, titanate compounds, silicic acid compounds, ferrocyanide compounds, chelating resins, activated carbon, oxine-impregnated activated carbon, zeolite, silica particles, and alumina particles, the material can be made highly suitable for removing target radionuclides.

[0098] Furthermore, the concentrations of alpha, beta, and gamma nuclides and the pH can be measured safely by sampling the radioactive waste liquid and measuring it with an analytical device, by measuring it with a survey meter, or by measuring it online.

[0099] Furthermore, by using one or more of the alpha nuclides selected from the group consisting of plutonium, americium, curium, neptunium, and uranium, transition metals such as ruthenium, technetium, and niobium, alkali metals such as cesium, alkaline earth metals such as strontium, rare earths such as cerium, and non-metallic elements such as antimony, tellurium, halogens such as iodine, carbon, and boron, it is possible to provide a new method and system for treating radioactive liquid waste that has never existed before.

[0100] Second Embodiment A radioactive liquid waste treatment method and a radioactive liquid waste treatment system according to a second embodiment of the present invention will be described with reference to FIG.

[0101] The radioactive liquid waste treatment method of the second embodiment has some steps overlapping with the radioactive liquid waste treatment method of the first embodiment described above, and the radioactive liquid waste treatment system of the second embodiment can be configured in a similar manner to the radioactive liquid waste treatment system shown in Figures 2 and 3, which is the same as the first embodiment described above. Therefore, in the following explanation, explanations of the same processes and configurations as those of the first embodiment described above will be omitted.

[0102] The method for treating radioactive liquid waste according to the second embodiment differs from that according to the first embodiment in the method for adjusting the pH to a predetermined pH or higher. In the method for treating radioactive liquid waste according to the second embodiment, the amount of powder or slurry to be added is determined based on the relationship between the amount of powder or slurry (liquid-solid ratio) of the β,γ nuclide adsorbent and the pH of the radioactive liquid waste after the addition of the powder or slurry.

[0103] The relationship between the liquid-solid ratio of the adsorbent and the pH after addition of the adsorbent will be explained with reference to Fig. 7. The example shown in Fig. 7 shows the results when 1000-fold diluted simulated seawater was used as the test liquid, the initial pH was 6, and CST was used as the β, γ nuclide adsorbent.

[0104] As shown in Figure 7, the pH after adding CST increased when the liquid-solid ratio of CST was 10 3 Under the conditions of mL / g, pH 10 and CST liquid-solid ratio 10 4Under the mL / g condition, the pH was 7, and the smaller the liquid-solid ratio, i.e., the greater the amount of CST added, the higher the pH after CST addition.

[0105] The other configurations and operations are substantially the same as those of the radioactive liquid waste treatment method and radioactive liquid waste treatment system of the first embodiment described above, and details thereof will be omitted.

[0106] The radioactive liquid waste treatment method and radioactive liquid waste treatment system of the second embodiment of the present invention also provide substantially the same effects as those of the radioactive liquid waste treatment method and radioactive liquid waste treatment system of the first embodiment described above. That is, according to the radioactive liquid waste treatment method of this embodiment, the pH can be adjusted to alkaline (above a predetermined pH) by controlling the amount of β,γ nuclide adsorbent added (liquid-solid ratio), and as shown in the first embodiment, the sorption amount of α nuclides of the β,γ nuclide adsorbent can be increased.

[0107] Furthermore, by determining the amount of powder or slurry to be added based on the relationship between the liquid-solid ratio of the powder or slurry and the pH of the radioactive liquid waste after the addition of the powder or slurry, it is possible to provide a radioactive liquid waste treatment method and a radioactive liquid waste treatment system that can treat alpha, beta, and gamma nuclides with a minimum required equipment configuration, thereby eliminating the need to immerse the adsorbent in an alkaline solution, and achieving a simpler configuration.

[0108] <Other> It should be noted that the present invention is not limited to the above-described embodiment, and includes various modifications. The above-described embodiment has been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to an embodiment having all of the described configurations.

[0109] It is also possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment, or to add, delete, or replace part of the configuration of each embodiment with the configuration of another embodiment. [Explanation of symbols]

[0110] 1...Radioactive waste treatment system 2...High-dose resin storage tank 3...First receiving tank 4...Chemical reactor 5...Heating device 6...Cleaning liquid supply tank 7…Organic acid bath 8...Organic acid salt bath 9...Transfer tank 10...Chemical cleaning section 11...Second receiving tank 12...Incineration facility 13...Waste liquid decomposition equipment 14A, 14B...Radioactive nuclide concentration measuring device 15...Radioactive nuclide removal device 16...Agglomeration device 19...Waste liquid treatment unit 20...Dehydration device 21…Solidification equipment 22, 24, 32, 34, 43, 47...Transfer pumps 23...Organic waste supply pipe 25...Organic waste transfer pipe 26, 27, 28, 35, 37, 39, 44...Valves 29, 30, 31, 36, 38, 45, 46, 48, 49, 54, 55, 56, 103...Piping 33...Cleaning liquid supply pipe 40...Waste liquid supply pipe 101…α,β,γ nuclide removal device 121…Adsorbent supply device 122...Flocculant supply device 131...Concentrator

Claims

1. A powder that adsorbs β and γ nuclides or a slurry containing said powder is added to radioactive liquid waste containing α, β, and γ nuclides so that the pH is equal to or higher than a predetermined value. Methods for treating radioactive liquid waste.

2. 2. The method for treating radioactive liquid waste according to claim 1, The reference pH that is equal to or higher than the predetermined pH is determined from the pH at which the target α nuclide precipitates. Methods for treating radioactive liquid waste.

3. 3. The method for treating radioactive liquid waste according to claim 2, The pH at which the α nuclide precipitates is determined from the potential-pH diagram of the target α nuclide. Methods for treating radioactive liquid waste.

4. 2. The method for treating radioactive liquid waste according to claim 1, The alkaline solution in which the powder or the slurry has been soaked is added to the radioactive waste liquid. Methods for treating radioactive liquid waste.

5. 2. The method for treating radioactive liquid waste according to claim 1, The amount of the powder or the slurry to be added is determined based on the relationship between the liquid-solid ratio of the powder or the slurry and the pH of the radioactive liquid waste after the addition of the powder or the slurry. Methods for treating radioactive liquid waste.

6. 2. The method for treating radioactive liquid waste according to claim 1, In addition to the powder or the slurry, a drug is injected. Methods for treating radioactive liquid waste.

7. 5. The method for treating radioactive liquid waste according to claim 4, The alkaline solution is any one of an inorganic acid, an inorganic alkali, an organic acid, and an organic alkali. Methods for treating radioactive liquid waste.

8. 7. The method for treating radioactive liquid waste according to claim 6, The agent is any one of inorganic acid, inorganic alkali, organic acid, and organic alkali. Methods for treating radioactive liquid waste.

9. 2. The method for treating radioactive liquid waste according to claim 1, The powder is at least one selected from the group consisting of cation exchange resin, Fe oxide, titanic acid compound, titanate compound, silicic acid compound, ferrocyanide compound, chelating resin, activated carbon, oxine-impregnated activated carbon, zeolite, silica particles, and alumina particles. Methods for treating radioactive liquid waste.

10. 2. The method for treating radioactive liquid waste according to claim 1, The concentrations of the α nuclide, the β nuclide, and the γ nuclide and the pH are measured by sampling the radioactive liquid waste and measuring it with an analytical device, by measuring it with a survey meter, or by measuring it online. Methods for treating radioactive liquid waste.

11. 2. The method for treating radioactive liquid waste according to claim 1, The α nuclide is one or more selected from the group consisting of plutonium, americium, curium, neptunium, and uranium, transition metals such as ruthenium, technetium, and niobium, alkali metals such as cesium, alkaline earth metals such as strontium, rare earths such as cerium, and non-metal elements such as antimony, tellurium, iodine, and other halogens, carbon, and boron. Methods for treating radioactive liquid waste.

12. A radioactive liquid waste treatment system for removing alpha nuclides, beta nuclides, and gamma nuclides from radioactive liquid waste containing the alpha nuclides, beta nuclides, and gamma nuclides, comprising: A removal device is provided that adds a powder that adsorbs β and γ nuclides or a slurry containing the powder to the radioactive waste liquid so that the pH is equal to or higher than a predetermined value. Radioactive waste treatment system.

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