Aluminum waste treatment method

Abstract

To provide a treatment method suitable for radioactive aluminum waste such as aluminum separators included in HEPA filters.SOLUTION: An aluminum waste treatment method is provided, comprising mixing an aluminosilicate raw material, alkali activator, and aluminum waste contaminated with radioactive substances to form a solidified product containing a geopolymer.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a method for treating aluminum waste. [Background technology]

[0002] Some air filters (HEPA filters) used in nuclear power plants, nuclear fuel cycle facilities, and other nuclear facilities contain aluminum foil as a separator. Air filters used in these facilities are classified as low-level radioactive waste with a relatively low level of radioactivity (Level II (L2)), and therefore must be solidified in containers such as drums and then disposed of by burying them in artificial structures such as concrete pits installed at a shallow depth of about 10 meters underground (also known as "pit disposal").

[0003] Cement, which is used as a standard solidification material in many nuclear power facilities, is alkaline with a pH of about 12 to 13, so aluminum may react with cement to generate hydrogen gas. In addition, when the concentration of radioactive materials in radioactive waste becomes high, the water in the cement may be radiolyzed to generate hydrogen gas.

[0004] The methods of treating HEPA filters used in nuclear facilities include separation and removal of the aluminum separator and vitrification.

[0005] Patent Document 1 (JP 2002-035732 A) describes "an apparatus for separating and processing an aluminum separator from a HEPA filter or a filter of the same structure, which is composed of a core portion formed of corrugated media and an aluminum separator inserted into the gaps between the corrugations, and a frame portion surrounding the outer periphery of the core portion, after the filter has been used, the apparatus comprising: a stand for mounting the filter; a clamping mechanism for fixing the frame portion of the filter onto the stand; a pair of cutters for cutting the core portion vertically along the left and right inner edges of the frame portion as they descend from above to below the filter; and a media winding mechanism positioned above the height of the filter, the upper end of the media of the cut core portion being attached to the winding mechanism, and the media being wound up so that the aluminum separator falls off by gravity and is separated."

[0006] Patent Document 2 (JP Patent Publication 4-290997) describes a method for melting and processing a HEPA filter, which is characterized in that "after pre-cutting a HEPA filter consisting of an aluminum thin plate separator and a glass fiber filter cloth, it is melted together with a vitrification additive and the aluminum thin plate in the HEPA filter is vitrified and solidified."

[0007] Patent Document 3 (JP Patent Publication No. 2015-121509) describes a "method for vitrification of aluminum and filter radioactive waste, characterized in that aluminum and filter radioactive waste are mixed with composition glass in an induction heating low-temperature melting furnace, melted at 1,100 to 1,200°C, and vitrified into a glass solidification body."

[0008] The use of hydrogen oxidation catalysts to mitigate the effects of hydrogen gas evolution on cement solidification is known.

[0009] Patent Document 4 (JP Patent Publication No. 2002-286893) describes a "method for treating radioactive waste in which radioactive waste solidified with cement is sealed in a container, characterized in that a catalyst is placed between the solidified body and the container, and the container is sealed."

[0010] It is known that the generation of hydrogen gas during cement solidification can be suppressed by treating the surface of aluminum waste.

[0011] Non-patent document 1 (Nishiura Hideaki et al., "Mortar-filled solidification of aluminum items contained in low-level radioactive waste (1) General issues and countermeasures for aluminum items," Proceedings of the Spring Annual Meeting of the Atomic Energy Society of Japan, 3G09, 2023) describes that an oxide coating is formed on the surface of the aluminum waste by immersing the aluminum waste in a weak alkaline solution before cement solidification.

[0012] Non-patent document 2 (Mitsuyoshi Motoyama et al., "Mortar-filled solidification of aluminum items contained in low-level radioactive waste (2) Aluminum countermeasures currently under consideration," Proceedings of the Spring Annual Meeting of the Atomic Energy Society of Japan, 3G10, 2023) describes applying paint to the surface of aluminum waste before cement solidification.

[0013] It is known that geopolymers can be used as a solidification material for radioactive waste. Geopolymers can control the moisture content and reduce the amount of free water compared to cement, which makes it possible to suppress the generation of hydrogen gas due to radiolysis.

[0014] Patent Document 5 (JP 2017-067679 A) describes a method for treating radioactive waste in which geopolymer, radioactive waste, and mixed water are kneaded and cured under heating conditions in a waste container using an in-drum mixer to solidify the mixture, and the solidified material within the waste container is then removed together with the waste container, the method being characterized in that the water evaporated by heating is recovered, and the moisture content of the solidified material is controlled to 35% by weight or less based on the amounts of geopolymer, mixed water, and recovered evaporated water.

[0015] Non-patent document 3 (Takahiro Kikuchi et al., "Geopolymer solidification of readily soluble fly ash (3) Comparison of characteristics between geopolymer and cement solidified bodies", Abstracts of the Autumn Meeting of the Atomic Energy Society of Japan, 3A13, 2017) describes that by subjecting geopolymer to vacuum drying treatment, the free water content can be reduced, thereby lowering the G value, which is an indicator of the amount of hydrogen generated.

[0016] Patent Document 6 (JP 2019-045453 A) describes a method for immobilizing cesium in cesium-containing waste, comprising the following steps (I), (II), and (III): (I) a step of kneading cesium-containing waste with metakaolin and an alkaline solution to prepare a geopolymer kneaded material A, (II) a step of curing the obtained geopolymer kneaded material A at a temperature of 90 to 120°C to produce a pre-solidified geopolymer body B, and (III) a step of vacuum drying the obtained pre-solidified geopolymer body B to obtain a geopolymer solidified body C. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] JP 2002-035732 A [Patent Document 2] Japanese Patent Application Publication No. 4-290997 [Patent Document 3] JP 2015-121509 A [Patent Document 4] JP 2002-286893 A [Patent Document 5] JP 2017-067679 A [Patent Document 6] JP 2019-045453 A [Non-patent literature]

[0018] [Non-Patent Document 1] Hideaki Nishiura et al., "Mortar-filled solidification of aluminum items contained in low-level radioactive waste (1) General issues and countermeasures for aluminum items," Proceedings of the Spring Annual Meeting of the Atomic Energy Society of Japan, 3G09, 2023 [Non-Patent Document 2] Mitsushi Motoyama et al., "Mortar-filled solidification of aluminum items contained in low-level radioactive waste (2) Aluminum countermeasures currently under consideration," Proceedings of the Spring Annual Meeting of the Atomic Energy Society of Japan, 3G10, 2023 [Non-Patent Document 3] Takahiro Kikuchi et al., "Geopolymer solidification of easily soluble fly ash (3) Comparison of properties of geopolymer and cement solidified bodies," Proceedings of the Autumn Meeting of the Atomic Energy Society of Japan, 3A13, 2017 Summary of the Invention [Problem to be solved by the invention]

[0019] Separating the aluminum separator from the HEPA filter and disposing of it separately would be costly and inefficient, since the amount of aluminum waste to be treated is small.

[0020] Vitrification is the most stable method of immobilizing waste, but the construction and running costs of treatment facilities are high, making it economically disadvantageous to apply vitrification to L2 waste such as aluminum separators in HEPA filters.

[0021] It is difficult for hydrogen oxidation catalysts to maintain their catalytic activity over a long storage period, and it is also difficult to maintain the oxide film or coating stably over a long period of time in the surface treatment of aluminum waste.

[0022] Because geopolymers are more expensive than cement, they have been considered for use in treating waste with relatively high levels of radioactivity per volume or mass, such as waste ion exchange resins that have captured radioactive materials and their decomposition residues, and incineration residues of rubble, which fall under the category of low-level radioactive waste with relatively high levels of radioactivity (Level I (L1)).

[0023] The present disclosure provides a method for treating radioactive aluminum waste, such as aluminum separators contained in HEPA filters. [Means for solving the problem]

[0024] The inventors discovered that, because metallic aluminum produces aluminate ions, which are the raw material for geopolymers, in high-concentration alkali, by coexisting radioactive aluminum waste during geopolymer formation, the radioactive aluminum waste can be used not only as a material to be immobilized in the geopolymer, but also as a raw material for the geopolymer, and thus completed the present invention.

[0025] The present disclosure includes the following aspects. [Aspect 1] A method for treating aluminum waste, comprising mixing an aluminosilicate raw material, an alkaline activator, and aluminum waste contaminated with radioactive materials to form a solidified material comprising a geopolymer. [Aspect 2] 2. The method of embodiment 1, wherein the mixing further comprises mixing radioactive waste other than the radioactively contaminated aluminum waste. [Aspect 3] 3. The method according to claim 1 or 2, wherein the aluminosilicate raw material is at least one selected from the group consisting of metakaolin, fly ash, and blast furnace slag. [Aspect 4] The method according to any one of aspects 1 to 3, wherein the alkaline activator is an aqueous solution containing at least one selected from the group consisting of an alkali metal hydroxide and an alkali metal silicate. [Aspect 5] The mixing mixing the aluminum waste with the alkaline activator to obtain a premix containing aluminate ions; mixing the premix with the aluminosilicate feedstock; The method according to any one of aspects 1 to 4, comprising: [Aspect 6] The method according to any one of aspects 1 to 5, further comprising vacuum drying the solidified product. [Aspect 7] The method according to any one of aspects 1 to 6, further comprising adjusting the moisture content of the solidified material to 35% by mass or less. [Aspect 8] The method according to any one of the preceding aspects, wherein the aluminum waste is a separator of a HEPA filter. [Aspect 9] 9. The method of embodiment 8, further comprising the step of separating the separator from the HEPA filter. [Aspect 10] pulverizing the HEPA filter to obtain a pulverized material containing the aluminum waste; mixing the ground material with the alkaline activator to obtain a premix containing aluminate ions; mixing the premix with the aluminosilicate feedstock; 9. The method of embodiment 8, comprising: Effect of the Invention

[0026] According to the aluminum waste treatment method of the present disclosure, radioactive aluminum waste such as aluminum separators contained in HEPA filters can be stably and economically treated.

[0027] It should be noted that the above description should not be considered as disclosing all the embodiments of the present invention and all the advantages related to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The present invention will now be described in more detail with the purpose of illustrating representative embodiments thereof, but the present invention is not limited to these embodiments.

[0029] [Method of disposing of aluminum waste] In one embodiment, a method for treating aluminum waste includes mixing an aluminosilicate raw material, an alkaline activator, and aluminum waste contaminated with radioactive materials (also referred to simply as "aluminum waste" in this disclosure) to form a solidified material containing a geopolymer.

[0030] Geopolymers are polymerized by forming aluminate ions and silicate ions by reaction of aluminosilicate raw materials with alkaline activators, and these ions undergo dehydration condensation to form -Si-O-Al- or -Si-O-Si- bonds. The residue of the aluminosilicate raw materials is fixed in the geopolymer. Unlike cement, geopolymers do not contain structural water in their skeletons, so the water content can be controlled to be lower than that of cement. This makes it possible to suppress the generation of hydrogen gas due to radiolysis of water. In addition, because geopolymers have cation exchange sites, radionuclide ions such as Cs-137 can be incorporated into the geopolymer structure during the polymerization process. Geopolymers are formed through various reactions depending on the type of aluminosilicate raw materials used. An example of a geopolymer reaction formula is shown below. Na 2 S 4 O 9 (aq) + 2NaOH(aq) + 4SiO 2 2Al 2 O 3 (s) → 4NaAlSi 2 O 6 (s)+H 2 O

[0031] When the aluminum waste is mixed with the alkaline activator, it generates aluminate ions, which are the raw material of the geopolymer. These aluminate ions are also incorporated into the geopolymer skeleton by the above-mentioned dehydration condensation. The residue of the aluminum waste that has released the aluminate ions is fixed in the geopolymer in the same manner as the residue of the aluminosilicate raw material. In this embodiment, the aluminum waste can be used not only as a material to be fixed in the geopolymer, but also as a raw material for the geopolymer, so that the aluminum waste can be stably and economically treated.

[0032] <Aluminosilicate raw material> Examples of the aluminosilicate raw material include metakaolin, coal ashes such as fly ash and clinker ash, slags such as blast furnace slag, steelmaking slag, sewage sludge molten slag, and coal gasification molten slag, aluminum silicate, zeolite which is crystalline silica alumina, and combinations of silica raw materials such as sodium silicate and silica fume with alumina raw materials such as alumina powder. The aluminosilicate raw materials can be used alone or in combination of two or more.

[0033] Fly ash is a glass-like spherical particle produced when molten coal ash particles floating in the combustion gas solidify near the boiler outlet due to a drop in temperature. Clinker ash is obtained by crushing the solidified lumps of red-hot coal ash that fall into a water tank at the bottom of the boiler and adjusting the particle size. Coal ash such as fly ash and clinker ash function as a source of Si and Al, which are the constituent elements of geopolymers, and can also supply Ca components to promote the solidification of geopolymers. Like coal ash, slag also functions as a source of Si and Al, and can supply Ca components to promote the solidification of geopolymers.

[0034] The aluminosilicate raw material is preferably at least one selected from the group consisting of metakaolin, fly ash, and blast furnace slag, since this promotes the formation of a three-dimensional network structure and allows the geopolymer to be solidified more efficiently.

[0035] The aluminosilicate raw material is preferably at least one selected from the group consisting of metakaolin and aluminum silicate, and more preferably metakaolin, because it can form a geopolymer with an excellent fixation rate for radioactive nuclides such as Cs-137.

[0036] <Alkaline activator> The alkali activator is a component that dissolves Si and Al from the aluminosilicate raw material and Al from the aluminum waste, and promotes dehydration condensation. The alkali activator is preferably an aqueous solution containing at least one selected from the group consisting of alkali metal hydroxides and alkali metal silicates. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide, and sodium hydroxide is preferred. Examples of the alkali metal silicate include sodium silicate and potassium silicate, and sodium silicate is preferred. Si in the alkali metal silicate can also be used as a constituent element of the geopolymer.

[0037] The alkali metal silicate can be used in the form of, for example, water glass. As the water glass, for example, JIS No. 1 (SiO 2 :35~38% by mass, Na 2 O: 17~19% by mass, Fe: 0.03% by mass or less, water-insoluble matter: 0.2% by mass or less), JIS No. 2 (SiO 2 :34~36% by mass, Na 2 O: 14-15% by mass, Fe: 0.03% by mass or less, water insoluble matter: 0.2% by mass or less), and JIS No. 3 (SiO 2 :28~30% by mass, Na 2 O: 9 to 10 mass %, Fe: 0.02 mass % or less, water insoluble matter: 0.2 mass % or less. Sodium hydroxide may be further added to the water glass.

[0038] <Radioactively contaminated aluminum waste> Examples of aluminum waste contaminated with radioactive materials include, but are not limited to, aluminum foil such as HEPA filter separators, aluminum glass cloth, exterior materials for thermal insulation materials, thin plates such as jigs, aluminum plates such as aluminum cases and aluminum frames, and aluminum parts attached to equipment.

[0039] In one embodiment, the aluminum waste is low-level radioactive waste (Level II (L2)) that is subject to shallow land disposal as defined in the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Nuclear Reactors and related laws and regulations.

[0040] The aluminum waste is preferably in the form of a thin plate, film, sheet, foil, fiber, string, or the like, with a relatively large specific surface area. Aluminum waste with a large specific surface area can generate aluminate ions more effectively upon contact with an alkaline activator, and therefore can efficiently solidify the geopolymer while reducing the amount of aluminosilicate raw material used. The specific surface area of ​​aluminum waste is, for example, 1×10 -4 m 2 / g~1m 2 The specific surface area of ​​the aluminum waste can be calculated based on the shape, size, and mass of the aluminum waste, and the density of metallic aluminum.

[0041] In one embodiment, the aluminum waste is a separator of a HEPA filter. A HEPA filter is a filter medium made of a sheet-like glass fiber folded into pleats, and an aluminum foil as a separator inserted between adjacent surfaces of the filter medium, which are placed inside an outer frame and sealed with a sealant and a gasket. JIS Z 4812:1995 is an example of a standard for filters for nuclear facilities.

[0042] <Radioactive waste other than aluminum waste> The above components may be further mixed with radioactive waste other than aluminum waste contaminated with radioactive materials. This allows radioactive waste other than aluminum waste to be solidified together in the geopolymer. Examples of radioactive waste other than aluminum waste include waste ion exchange resin that has captured radioactive materials and its decomposition residue, incineration residue of rubble, etc., metal cutting chips, plates and pipes contaminated with radioactive materials, and solutions containing radioactive materials. The amount of radioactive waste other than aluminum waste contaminated with radioactive materials is not particularly limited as long as it is within the range in which a solidified material containing a geopolymer is formed.

[0043] <aggregate> To increase the strength of the geopolymer, the above components may be further mixed with aggregates, such as standard sand, crushed sand, and silica sand.

[0044] <mixture> The above components, and optionally mixing water, are charged into a mixing vessel, and mixing can be carried out by placing a stirring blade or the like inside the mixing vessel.

[0045] <Mixing container> The mixing container is not particularly limited, and for example, a waste container can be used. The waste container is not particularly limited as long as it is capable of long-term storage. As the waste container, a drum can or a pail can is generally used. The capacity of the waste container can be appropriately selected in consideration of the processing efficiency, etc. The capacity of the waste container can be, for example, 200L, 120L, 100L, 80L, 60L, 50L, 40L, and 20L according to the specifications of drum cans and pail cans.

[0046] Mixing using a waste container as a mixing container is also called the in-drum method. Compared to the out-drum method, in which mixing is performed in a dedicated mixing tank and then the mixture is poured into a drum, the in-drum method reduces the number of contaminated materials and the contaminated work area because the only materials contaminated by radioactive waste are the mixing blades and other mixing members. The in-drum method also makes it easier to handle radioactive waste in an isolated facility.

[0047] <Preliminary Mixture> The aluminum waste may be mixed with an alkaline activator to obtain a premix containing aluminate ions, and then the premix may be mixed with an aluminosilicate raw material. This increases the concentration of aluminate ions in the mixture from the initial stage of mixing, and further promotes the formation of a three-dimensional network structure of the geopolymer. In addition, when the aluminum waste is mixed with an alkaline activator, hydrogen gas is generated in conjunction with the generation of aluminate ions. In this embodiment, hydrogen gas may be released to the outside when the premix is ​​prepared. This prevents bubbles derived from hydrogen gas from being mixed into the solidified product, and allows the formation of a solidified product with a higher density.

[0048] <Mixed water> Mixed water may be used during mixing. By using mixed water, sufficient fluidity can be ensured when mixing the above components. The mixed water is not particularly limited, and examples thereof include tap water, reclaimed water, and seawater. As the mixed water, the recovered evaporated water described below can also be reused.

[0049] <Scatter prevention plate> When a waste container is used as a mixing container, a scattering prevention plate may be provided around the opening of the waste container to prevent overflow and scattering of the mixture during mixing. This makes it possible to raise the liquid level during mixing while preventing radioactive waste from scattering to the surroundings. As a result, the solidified material can be stored in the waste container at a high filling rate. The scattering prevention plate is fixed so as to fit into the inner surface of the waste container during mixing. The size of the scattering prevention plate is appropriately selected depending on the stirring device, stirring conditions, and amount of components charged, but it is preferable to select it so that 85% or more of the volume of the waste container is filled with the solidified material. After mixing, the scattering prevention plate may be dropped into the waste container and stored in the waste container together with the solidified material. This makes it possible to omit separate processing of the contaminated scattering prevention plate.

[0050] <Si / Al ratio> The types and amounts of the above components can be determined, for example, so that the atomic ratio of Si to Al (Si / Al ratio) in the geopolymer is 1:1 to 35:1. From the viewpoint of effective fixation of radioactive nuclides, the types and amounts of the above components are determined so that the Si / Al ratio is preferably 1.2:1 to 5:1, more preferably 1.5 to 3:1.

[0051] <Mixing time> The mixing time is not particularly limited, and can be appropriately determined depending on the shape, type and mixing amount of the components, the mixing temperature, etc. The mixing time can be, for example, 5 minutes to 0.5 hours, or 5 minutes to 1 hour.

[0052] <Mixing temperature> The mixing may be performed without heating or with heating. The mixing temperature is not particularly limited, but may be, for example, 20° C. to 40° C. The mixing temperature may be increased stepwise or continuously. The mixing may be performed while collecting water vapor generated by heating.

[0053] <Mixing pressure> The mixing may be performed under normal pressure or under reduced pressure. By mixing under reduced pressure, the mixing temperature can be lowered, the generated water vapor can be easily collected, and the moisture content of the solid matter can be more precisely controlled. The mixing pressure can be appropriately set within a range lower than the vapor pressure of water. For example, when the mixing temperature is 80°C, the vapor pressure of water is 0.5 atm, so the mixing pressure is set to 0.5 atm or less, preferably 0.1 atm or less.

[0054] If the aluminum waste is a separator of a HEPA filter, the separator may be separated from the HEPA filter before mixing. Alternatively, the HEPA filter may be crushed and crushed material containing the aluminum waste (separator) may be mixed. The crushed material may include, for example, a filter medium such as glass fiber, an outer frame, a sealant, a gasket, etc.

[0055] In one embodiment, the treatment method includes crushing the HEPA filter to obtain a crushed material containing aluminum waste; mixing the crushed material with an alkaline activator to obtain a premix containing aluminate ions; and mixing the premix with an aluminosilicate raw material. In this embodiment, for example, if the HEPA filter contains silicon-containing materials such as glass fiber filter media, these materials will also dissolve when mixed with the alkaline activator to produce silicate ions. The produced silicate ions can also be used to form a geopolymer. The premix may be mixed with an aluminosilicate raw material after filtering if necessary.

[0056] Formation of solidified matter During the mixing of the above components, dehydration and condensation proceeds to form a solidified material containing a geopolymer. This allows the aluminum waste and its residue, and optionally other radioactive waste, to be immobilized in the solidified material. After mixing of the above components, the mixture can be cured as necessary to further promote dehydration and condensation, and to further improve the three-dimensional network structure of the geopolymer.

[0057] <Curing> Curing is preferably performed with the mixture in the mixing container used for mixing. The curing step starts at the end of the mixing step, for example, when the mixing is stopped. The impeller used for mixing may be submerged in the mixture, or may be taken out and washed as necessary and used for other mixing. When mixing is performed in a waste container, curing can be continued in the waste container to form a solidified material in a state suitable for transport.

[0058] <Cure time> The curing time is not particularly limited, and can be appropriately determined based on the mixing temperature, curing temperature, water content of the mixture, volume and shape of the container, etc. The curing time can be, for example, 3 hours to 24 hours.

[0059] <Curing temperature> The curing may be performed without heating or with heating. The curing temperature is not particularly limited, but may be, for example, 20°C to 400°C. The curing temperature may be increased stepwise or continuously. Curing may be performed while collecting water vapor generated by heating.

[0060] <Curing pressure> Curing may be performed under normal pressure or under reduced pressure. Curing is preferably performed under reduced pressure. By curing under reduced pressure, the curing temperature can be lowered, the generated water vapor can be easily collected, and the moisture content of the solid matter can be more precisely controlled. Curing under reduced pressure can also shorten the curing time. The curing pressure can be appropriately set within a range lower than the vapor pressure of water. For example, when the curing temperature is 80°C, the vapor pressure of water is 0.5 atm, so the curing pressure is set to 0.5 atm or less, preferably 0.1 atm or less.

[0061] <Vacuum drying> The solidified material containing the formed geopolymer may be vacuum-dried. By vacuum-drying the solidified material, the water content of the solidified material can be reduced, and hydrogen gas generation due to radiolysis of water can be further suppressed. When aluminum waste or any other radioactive waste contains Cs-137, vacuum drying effectively suppresses the leaching of Cs-137. Without being bound by any theory, it is believed that the structure around Cs fixed at the cation exchange site of the geopolymer becomes pollucite by vacuum drying, and Cs is trapped in the crystal lattice, making it difficult to leach. The pressure and time of vacuum drying are not particularly limited, but can be, for example, 50 kPa to 0.5 kPa and 10 hours to 200 hours.

[0062] <Moisture content of solidified material> The treatment method of one embodiment further includes controlling the moisture content of the solidified material to 35% by mass or less. This can further suppress hydrogen gas generation due to radiolysis of water. The moisture content of the solidified material is preferably controlled to 20% by mass or less, more preferably 10% by mass or less. The moisture content of the solidified material can be controlled by adjusting at least one of the temperature, pressure, and time of the container based on the amount of mixed water used and the amount of evaporated water recovered during mixing, curing, or vacuum drying. Since the water generated by dehydration condensation is also included in the moisture content of the solidified material, the amount of geopolymer generated is also taken into consideration when controlling the moisture content of the solidified material.

[0063] The solidified material in the waste container is transported to a disposal site together with the waste container, and can then be stored or buried underground.

[0064] [Aluminum waste treatment facility] The aluminum waste treatment facility of one embodiment includes a treatment chamber that is isolated from the outside and into which a waste container is carried. a waste supply device for supplying aluminum waste contaminated with radioactive materials into the waste container; a solidification material supplying device for supplying an aluminosilicate raw material, an alkaline activator, and optionally mixed water into the waste container; a mixing device for mixing the aluminosilicate raw material, the alkaline activator, the radioactively contaminated aluminum waste, and optionally the mixed water in the waste container; a heating device for heating the waste container; A recovery device for recovering evaporated water; a control device for controlling the moisture content of the solidified material in the waste container; a transport device for transporting the waste container between the outside of the processing facility and the processing chamber; Equipped with.

[0065] The treatment facility may be, for example, a concrete building. The inside of the building may be divided into a plurality of treatment chambers by concrete partitions, and the waste container may be moved between the plurality of treatment chambers for each step, such as mixing, curing, and vacuum drying, to perform each step.

[0066] Radiation control areas vary depending on the dose of radioactive material. Workers can enter low-dose areas, where they prepare waste containers such as drums and remove waste containers that have been treated. Depending on the dose of radioactive material, these tasks may be automated.

[0067] A waste container such as a drum can is carried into the processing chamber from outside the processing facility by a transport device such as an unmanned transport vehicle. The transport device is equipped with a mounting table, and the waste container is transported while placed on the mounting table. The mounting table is configured to be freely raised and lowered in the vertical direction, and the height position at which the waste container is held can be adjusted. The transport device may be equipped with a mechanism for moving based on remote control from a control room, for example, or may be equipped with a mechanism for moving to a predetermined location at a predetermined timing by automatic control or the like. After processing is completed, the transport device moves the waste container to the outside of the processing facility.

[0068] The above-mentioned aluminum waste treatment method is carried out in the treatment chamber of the treatment facility. The treatment facility includes a waste supply device such as a hopper that supplies the aluminum waste contaminated with radioactive materials and optionally other radioactive waste into a waste container, a solidification material supply device such as a hopper or a measuring tank that supplies the aluminosilicate raw material, the alkaline activator, and optionally mixed water into the waste container, and a mixer that mixes the aluminosilicate raw material, the alkaline activator, the aluminum waste contaminated with radioactive materials, and optionally mixed water in the waste container. The treatment facility may further include a mixed water supply device that supplies mixed water separately from the aluminosilicate raw material and the alkaline activator.

[0069] The waste supply device and the solidification material supply device are provided at their lower ends with discharge sections for discharging the contents of each supply device into the waste container. The discharge section is a cylindrical member extending downward, and the contents are discharged into the waste container when the discharge section is inserted into the opening of the waste container.

[0070] The mixing device includes a driving device and a stirring member such as a stirring blade. The number of stirring blades may be two or more. When a plurality of stirring blades are provided, they are preferably arranged at equal intervals so as to extend radially from the rotating shaft. Each stirring blade is attached to the rotating shaft, for example, with the stirring surface formed to be wide perpendicular to the rotating direction of the stirring blade.

[0071] A scattering prevention plate may be provided around the opening of the waste container. The scattering prevention plate is temporarily fixed to the waste container by a stopping member. Examples of the stopping member include a spring that can hook one end onto the outer surface of the waste container and the other end onto the scattering prevention plate, and a protrusion provided on the inner surface of the waste container. The scattering prevention plate may be a cylindrical member that fits into the inner surface of the waste container. The scattering prevention plate can be dropped into the waste container after mixing by removing the stopping member such as the spring, making a slit in the part of the scattering prevention plate that corresponds to the protrusion on the inner surface of the waste container, or the like.

[0072] The treatment facility includes a heating device for heating the waste container and a recovery device for recovering evaporated water. The heating device is not particularly limited, but examples include a rubber heater and a jacket heater. The heating device may or may not be directly attached to the waste container. For example, the heating device may be attached to a chamber that houses the waste container. The heating device may be a heating chamber that houses the waste container transferred from the treatment chamber. The recovery device recovers all of the water generated during mixing, curing, and vacuum drying. The recovery device may be equipped with a condensation mechanism that condenses water vapor.

[0073] The processing facility may include a pressure reducing device, such as a vacuum pump, for reducing the pressure within the waste container or within a chamber in which the waste container is housed.

[0074] The treatment facility may include a crushing device for crushing the aluminum waste in the treatment chamber. Examples of the crushing device include a biaxial crusher and a vertical rotary crusher.

[0075] The above-mentioned conveying device, each supply device, mixing device, heating device, recovery device, pressure reducing device, etc. are connected to a control device that controls the operation of these devices. The control device estimates the moisture content of the solidified material based on the amount of mixed water used and evaporated water recovered during mixing, curing, or vacuum drying, and the amount of geopolymer produced, and adjusts the operating conditions of each device connected to the control device so that the desired moisture content is achieved.

[0076] The method and treatment equipment of the present disclosure can be suitably used for treating aluminum waste contaminated with radioactive materials.

[0077] It will be apparent to those skilled in the art that the above-described embodiments and examples can be modified in various ways without departing from the basic principles of the present invention. It will also be apparent to those skilled in the art that various improvements and modifications of the present invention can be made without departing from the spirit and scope of the present invention. [Industrial Applicability]

[0078] The disclosed method and treatment equipment can be advantageously used for the treatment of aluminum waste contaminated with radioactive materials.

Claims

1. A method for treating aluminum waste, comprising mixing an aluminosilicate raw material, an alkaline activator, and aluminum waste contaminated with radioactive materials to form a solidified material comprising a geopolymer.

2. 10. The method of claim 1, wherein said mixing further comprises mixing radioactive waste other than said radioactively contaminated aluminum waste.

3. The method according to claim 1 or 2, wherein the aluminosilicate raw material is at least one selected from the group consisting of metakaolin, fly ash, and blast furnace slag.

4. The method according to claim 1 or 2, wherein the alkaline activator is an aqueous solution containing at least one selected from the group consisting of alkali metal hydroxides and alkali metal silicates.

5. The mixing mixing the aluminum waste with the alkaline activator to obtain a premix containing aluminate ions; mixing the premix with the aluminosilicate feedstock; The method of claim 1 or 2, comprising:

6. The method according to claim 1 or 2, further comprising vacuum drying the solidified material.

7. The method according to claim 1 or 2, further comprising adjusting the moisture content of the solidified material to 35% by mass or less.

8. 3. The method according to claim 1 or 2, wherein the aluminum waste is a separator of a HEPA filter.

9. The method of claim 8 further comprising the step of separating the separator from the HEPA filter.

10. pulverizing the HEPA filter to obtain a pulverized material containing the aluminum waste; mixing the ground material with the alkaline activator to obtain a premix containing aluminate ions; mixing the premix with the aluminosilicate feedstock; The method of claim 8 , comprising: