JP6730126B2 - Method for manufacturing solid waste of radioactive waste - Google Patents

Description

The embodiment of the present invention relates to a technique for manufacturing a solidified body of radioactive waste generated in a nuclear facility.

Conventionally, there are a vitrification method and a cement solidification method as a method for treating radioactive waste containing a high concentration of radioactive substances (hereinafter referred to as high-dose radioactive waste). In the vitrification method, the mixture of glass and radioactive waste is heated at a high temperature of 1200° C. or higher, and thus the treatment cost is high. On the other hand, the cement solidification method is an inexpensive treatment method. However, in the case of high-dose radioactive waste, the moisture contained in the manufactured cement solidification material is radiolytically decomposed to generate hydrogen gas and the like. Therefore, in some containers, a drug that fixes gas is placed in a container that stores radioactive waste.

JP, 2001-228296, A

From the above viewpoint, a geopolymer solidification method is being studied as an inexpensive treatment method and a method for producing a solidified body containing no water. The main components of the geopolymer are silicon and aluminum, which are inexpensive, and the skeletal structure of the geopolymer does not contain water. However, the water used in the manufacturing process and the water generated by the condensation polymerization reaction of the geopolymer remain. Although the water content in the solidified body of geopolymer can be reduced by heating the solidified body, a large amount of heat energy is required and the cost required for preparing the solidified body increases.

The embodiment of the present invention has been made in consideration of such circumstances, and it is an object of the present invention to provide a solid waste production technology for radioactive waste that can reduce the energy required when producing a solid geopolymer. To aim.

A method for producing a solidified body of radioactive waste according to an embodiment of the present invention, a mixing step of mixing a material forming a geopolymer and a radioactive waste, a solidification step of solidifying the mixture mixed in the mixing step, A pulverizing step of pulverizing the mixture solidified in the solidifying step, and a drying step of forming the geopolymer solidified body by drying the mixture pulverized in the pulverizing step in an environment lower than atmospheric pressure. Including.

Embodiments of the present invention provide a technique for producing a solidified product of radioactive waste that can reduce the energy required when producing a solidified geopolymer.

The figure which shows the solidified body manufacturing apparatus of the radioactive waste of 1st Embodiment. The flowchart which shows the solid waste solidification manufacturing method of 1st Embodiment. The figure which shows the solidified body manufacturing apparatus of the radioactive waste of 2nd Embodiment. The flowchart which shows the solid waste solidification manufacturing method of 2nd Embodiment. The graph which shows the measurement result of the water content of a test body.

(First embodiment)
Hereinafter, the present embodiment will be described with reference to the accompanying drawings. Reference numeral 1 in FIG. 1 is a solid waste producing apparatus for radioactive waste according to the first embodiment. In the present embodiment, a solidified body of radioactive waste is produced by using a method of solidifying radioactive waste by a geopolymer that does not utilize a hydration reaction (geopolymer solidification method).

As shown in FIG. 1, a solid waste production apparatus 1 for radioactive waste is charged with a geopolymer material, radioactive waste, and water, and a mixing section 2 for mixing these materials and a mixing section 2 are arranged inside the apparatus. From the first decompression chamber 4 (first vacuum chamber) capable of decompressing, the first decompression pump 5 (first vacuum pump) for evacuating the air inside the first decompression chamber 4, and the first decompression pump 5 A first removal filter 6 that removes radioactive substances contained in the extracted air when it is released into the atmosphere. The mixing unit 2 includes a stirring blade for stirring the geopolymer material, radioactive waste, and water, and a motor for rotating the stirring blade. Geopolymer is a binder for solidifying radioactive waste. The geopolymer material is a material for forming a geopolymer, and contains a solidifying material, an alkali stimulant and the like.

Further, the apparatus 1 for producing a solidified product of radioactive waste includes a mold 7 for molding the mixture, a drying unit 8 for drying the solidified product, which is solidified from the mold 7 and solidified at a predetermined temperature, A second decompression chamber 9 (second vacuum chamber) in which the drying unit 8 is arranged and which can decompress the inside, and a second decompression pump 10 (second vacuum pump) for evacuating air inside the second decompression chamber 9 ) And a second removal filter 11 that removes radioactive substances contained in the air when the air extracted from the second decompression pump 10 is released into the atmosphere.

Further, the radioactive waste solidified body manufacturing apparatus 1 includes a storage canister 12 that stores the dried and solidified solidified geopolymer.

The geopolymer is a silicon-aluminum-based binder containing silicon (Si) as a main component, and is one kind of inorganic polymer containing sodium silicate solution (water glass) as a monomer source. Further, the geopolymer is formed by adding water to the material of the geopolymer. Water is not included in the skeletal structure of the geopolymer, but water is necessary to promote the reaction that forms the geopolymer.

The solidifying material which is one of the geopolymer materials is, for example, metakaolin, kaolin, blast furnace slag, fly ash, incineration ash and the like. Examples of the alkali stimulant include lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, rubidium hydroxide, lithium silicate, sodium silicate, potassium silicate, cesium silicate, and rubidium silicate. A single substance or a combination of at least one of these can be used. Also, and some of the water that contributed to the formation of the geopolymer remains in the structure of the geopolymer formed.

In the present embodiment, an aluminosilicate containing silicon (Si) such as metakaolin and aluminum (Al) as main components is used as the solidifying material. Further, as an alkali stimulant, a mixture of sodium silicate solution (Na ₂ SiO ₃ ) or potassium silicate solution (K ₂ SiO ₃ ) and potassium hydroxide (KOH) or sodium hydroxide (NaOH) is used. To use.

As shown in Table 1, the composition (ratio) of each material when producing a solidified geopolymer can be appropriately changed within a predetermined range. For example, aluminosilicate in the range of 6 to 53 wt%, sodium silicate solution in the range of 3 to 32 wt%, potassium hydroxide in the range of 1 to 10 wt%, water in the range of 2 to 27 wt%, high dose radioactive waste. Can be changed within the range of 3 to 45 wt %. The amounts of these materials are appropriately adjusted and charged into the mixing section 2.

In the present embodiment, the high-dose radioactive waste is in the range of 3 to 45 wt %, but when the radioactive waste contains a large amount of water, the input amount of water is reduced and the radioactive waste is replaced instead. The composition of the product may be increased to about 90 wt %.

Further, the method for producing a solidified product of radioactive waste according to the present embodiment is intended to make a solidified product of a high-dose radioactive waste, which may cause generation of hydrogen due to radiolysis of water, but is not limited thereto. Instead of solid substances, low-level radioactive wastes may be solidified regardless of the concentration of radioactive substances. In addition, it can be widely applied to wastes that require water removal. In particular, a large amount of contaminated water is produced when a severe accident involving core melting occurs in a nuclear power plant, and the present embodiment is applied to the production of a solidified body of a large amount of slurry discharged when the contaminated water is purified. It is considered that the method for producing a solidified product of radioactive waste can be applied.

Further, in the present embodiment, when the geopolymer material and the radioactive waste are mixed in the mixing unit 2, the air (atmosphere) inside the first decompression chamber 4 is evacuated by the first decompression pump 5. Then, the atmospheric pressure inside the first decompression chamber 4 is lowered. For example, the air pressure inside the first decompression chamber 4 is set to 0.8 atm or less.

By doing so, it is possible to increase the density and reduce the volume of the geopolymer solidified body while promoting the evaporation of water contained in the mixture and without generating bubbles or the like inside the geopolymer solidified body. That is, the solidified body can be densified, and the amount of water remaining in the mixture can be reduced.

Further, since the strength of the solidified body is improved with the reduction of the remaining amount of bubbles in the mixture, it is possible to prevent the solidified body after drying from being cracked. In addition, if the atmosphere is 0.8 atm or less, the evaporation of the water contained in the mixture can be sufficiently promoted. Further, a hygroscopic material (desiccant) such as silica gel may be arranged inside the first decompression chamber 4 in order to accelerate evaporation of water.

Moreover, since the gas containing the radioactive substance generated from the mixture is removed from the first decompression chamber 4 (container) by the first decompression pump 5, the radioactive substance does not leak out of the first decompression chamber 4. .. Therefore, it is possible to prevent the surrounding environment from being contaminated with radioactive substances. When the air sucked from the first decompression pump 5 is released into the atmosphere, the radioactive substance contained in this air is removed by the first removal filter 6.

The mixture mixed in the mixing section 2 is poured into the mold 7. Here, after a lapse of a predetermined time, the mixture is solidified to form a solidified geopolymer. When this solidified geopolymer is removed from the mold 7, it is held in a predetermined shape. In this embodiment, a columnar geopolymer solidified body is manufactured.

Further, the mold 7 may have a shape corresponding to a shape in which the solidified geopolymer solidified body is easily dried. For example, the surface (side peripheral surface) of the solidified geopolymer after molding may be corrugated to form irregularities that increase the surface area. Further, the shape of the solidified geopolymer after molding may be a donut shape having a hole in the center or a shape having a large number of holes on the surface.

In addition, although the crystallized water is not contained in the solidified body of the geopolymer, the water generated by the condensation polymerization reaction generated during the solidification process or the water initially added remains. By this water is exposed to radioactive material high dose, there is a possibility that hydrogen is generated by radiation degradation. Therefore, in this embodiment, the solidified geopolymer is dried in the drying unit 8. Moreover, the drying time of this embodiment is 3 hours.

Further, in the present embodiment, when the solidified geopolymer (mixture) is dried in the drying unit 8, a pattern of drying at room temperature, a pattern of drying at a temperature of less than 100° C., and a temperature of 100° C. or more are dried. The geopolymer solidified product is dried in at least one pattern selected from three patterns.

For example, in a normal temperature (5° C. or higher and lower than 35° C.) drying pattern, the geopolymer solidified body is dried without providing a heater or the like in the drying unit 8. Further, in a drying pattern of less than 100° C. (35° C. or more and less than 100° C.), a heater is provided in the drying unit 8, and the solidified geopolymer is heated to a temperature of less than 100° C. and dried. Further, in a drying pattern of 100° C. or higher (100° C. or higher and lower than 500° C.), a heater is provided in the drying section 8, and the geopolymer solidified body is heated to 100° C. or higher by this heater to be dried. The heater (heating unit) may be an electric heater or a coil for performing high frequency heating (electromagnetic induction heating).

In the present embodiment, when the solidified geopolymer is dried in the drying unit 8, the air (atmosphere) inside the second decompression chamber 9 is evacuated by the second decompression pump 10. Then, the air pressure inside the second decompression chamber 9 is lowered. For example, the air pressure inside the second decompression chamber 9 is set to 0.8 atm or less. The decompression of the second decompression chamber 9 is continued until the drying of the solidified geopolymer in the drying section 8 is completed.

By doing this, it is possible to accelerate the evaporation of the water contained in the solidified geopolymer, and thus it is possible to reduce the energy required for heating when manufacturing the solidified geopolymer. In addition, if the atmosphere is 0.8 atm or less, the evaporation of the water contained in the mixture can be sufficiently promoted. Further, a hygroscopic material (desiccant) such as silica gel may be arranged inside the second decompression chamber 9 in order to accelerate evaporation of water.

For example, in a normal temperature drying pattern, it is not necessary to use energy for driving a heater or the like. That is, the solidified geopolymer (mixture) can be dried at room temperature in a shorter time, and the heating energy for heating the solidified geopolymer can be saved.

Moreover, in the drying pattern of 100° C. or higher, energy for driving the heater is required. By heating the solidified mixture of geopolymer (mixture) in a reduced pressure atmosphere, evaporation of water is promoted by both heating and reduced pressure, and the water contained in the solidified body can be removed in a shorter time. Since the heating time is shortened, the energy required for heating and drying can be reduced.

On the other hand, when the solidified geopolymer (mixture) is heated to a higher temperature, the solidified geopolymer expands during heating and shrinks during subsequent cooling, which may cause cracks in the solidified geopolymer. If a crack is generated, the confinement performance of the radioactive substance by the solidified body may be deteriorated, and the desired confinement performance may not be satisfied. In the drying pattern of less than 100° C., since the heating temperature of the solidified body is set low, it is possible to suppress a rapid increase in the solidified body pressure due to the rapid evaporation of water, and it is possible to reduce cracks generated in the solidified body. it can. In addition, since the evaporation of water is promoted by both heating and depressurization, the water contained in the solidified body can be removed in a shorter time as compared with the case where the depressurization is not performed, and the energy required for heating and drying is reduced. be able to.

As described above, in the present embodiment, by reducing the pressure, the pressure difference between the inside and outside of the solidified body is increased, and the movement of water (steam) inside the solidified body is accelerated, thereby promoting drying. be able to. Further, since the drying is promoted, the time required for heat drying can be shortened as compared with the case where no pressure reduction is performed, and the heat energy required for heat drying can be reduced.

Further, since the gas containing the radioactive substance generated from the solidified geopolymer is removed from the second decompression chamber 9 (container) by the second decompression pump 10, the radioactive substance leaks out of the second decompression chamber 9. Will disappear. Therefore, it is possible to prevent the surrounding environment from being contaminated with radioactive substances. When the air sucked from the second decompression pump 10 is released into the atmosphere, the radioactive substance contained in this air is removed by the second removal filter 11. Further, even if hydrogen gas is generated by the radiolysis of water contained in the solidified body, it is removed from the second decompression chamber 9, so that the hydrogen gas can be prevented from catching fire in the drying section 8.

The dried geopolymer solidified body is stored in the storage canister 12 for storage. The solidified geopolymer may be used as a final disposal form, or may be stored in an intermediate storage facility and then subjected to an appropriate solidification treatment again to be finally disposed.

Will now be described with reference to FIG. 2 with the solidified body produced how the radioactive waste in the first embodiment. In the description of each step of the flowchart, for example, a portion described as "step S11" is abbreviated as "S11".

First, the geopolymer material, radioactive waste, and water are charged into the mixing unit 2 (S11: charging step). Next, the geopolymer material, the radioactive waste, and water are mixed in the mixing section 2 (S12: mixing step). Next, the first decompression pump 5 is driven to evacuate the air inside the first decompression chamber 4 in which the mixing section 2 is arranged to lower the atmospheric pressure (S13: decompression step during mixing). In the present embodiment, decompression of the first decompression chamber 4 is started after mixing is started, but decompression of the first decompression chamber 4 may be started before starting this mixing.

After completion of the mixing, the atmospheric pressure of the first decompression chamber 4 is returned to the atmospheric pressure, and the mixture is taken out of the first decompression chamber 4. Then, this mixture is poured into the mold 7 for molding (S14: molding step). Then, wait for a predetermined time until the mixture solidifies. Next, the solidified mixture, that is, the solidified geopolymer molded by the mold 7 is demolded (S15: demolding step). By doing so, the shape of the mixture can be adjusted, and the solidified geopolymer can be easily handled.

Next, the solidified geopolymer is placed in the drying unit 8 arranged in the second decompression chamber 9, and the drying of the solidified geopolymer is started (S16: drying step). Next, the second decompression pump 10 is driven to evacuate the air inside the second decompression chamber 9 in which the drying unit 8 is arranged to reduce the atmospheric pressure (S17: decompression step during drying). In the present embodiment, the pressure reduction in the second pressure reducing chamber 9 is started after the mixing is started, but the pressure reduction in the second pressure reducing chamber 9 may be started before the mixing is started.

In the present embodiment, the depressurized state of the second depressurizing chamber 9 is maintained for the entire period from the start of drying to the end of drying. Then, after the drying is completed, the atmospheric pressure of the second decompression chamber 9 is returned to the atmospheric pressure, and the geopolymer solidified body is taken out from the second decompression chamber 9. Next, the solidified geopolymer is housed in the storage canister 12 and stored (S18: storage step).

In the depressurizing step during mixing of the present embodiment, the atmospheric pressure inside the first depressurizing chamber 4 may be 0.8 atm or less. For example, the atmospheric pressure inside the first decompression chamber 4 may be 0.4 atm or less, 0.1 atm or less, or 0.005 atm or less.

In the drying depressurization step of the present embodiment, the atmospheric pressure inside the second depressurization chamber 9 may be 0.8 atm or less. For example, the atmospheric pressure inside the second decompression chamber 9 may be 0.4 atm or less, 0.1 atm or less, or 0.005 atm or less.

The atmospheric pressure inside the first depressurizing chamber 4 in the depressurizing step during mixing and the atmospheric pressure inside the second depressurizing chamber 9 in the depressurizing step during drying do not have to be reduced to the same atmospheric pressure, and they are different from each other. Is also good.

In the drying step of this embodiment, the solidified geopolymer may be dried at room temperature without heating. For example, the solidified geopolymer may be dried at a temperature of 25°C. Further, the solidified geopolymer may be heated and dried at a temperature lower than 100°C. For example, the solidified geopolymer may be dried at a temperature of 90°C. Further, the solidified geopolymer may be heated and dried at a temperature of 100° C. or higher. For example, the solidified geopolymer may be dried at a temperature of 105°C.

In particular, when the solidified geopolymer (mixture) is dried at room temperature or at a temperature lower than 100° C., the pressure inside the second decompression chamber 9 is preferably 0.1 atm or less. By doing so, even when the solidified geopolymer is dried at a low temperature, evaporation of water contained in the solidified geopolymer is promoted, so that the mixture can be sufficiently dried.

The heating temperature in the present embodiment means the maximum temperature reached by the solidified geopolymer. Further, it may be the average temperature of the solidified geopolymer during the period from the start of drying to the completion of drying.

The drying time in this embodiment is 3 hours, but this drying time can be changed as appropriate.

(Second embodiment)
Next, a method for manufacturing a solidified body of radioactive waste according to the second embodiment will be described with reference to FIGS. 3 to 4. In addition, the same components as those shown in the above-described embodiment are designated by the same reference numerals, and duplicate description will be omitted.

As shown in FIG. 3, the radioactive waste solidified body manufacturing apparatus 1A of the second embodiment includes a crusher 15 in addition to the radioactive waste solidified body manufacturing apparatus 1 (see FIG. 1) of the first embodiment. It has been added configuration. Other devices are the same.

Will now be described with reference to FIG. 4 with the solidified body produced how the radioactive waste in the second embodiment. In the method for producing a solidified product of radioactive waste according to the second embodiment, only S15A is different from the method for producing a solidified product of radioactive waste according to the first embodiment (see FIG. 2), and other steps are the same. is there.

In the second embodiment, the atmospheric pressure is lowered during the mixing step (S12) (S13). Then, after the mixing is completed, the atmospheric pressure of the first decompression chamber 4 is returned to the atmospheric pressure, and the mixture is taken out of the first decompression chamber 4. Then, the mixture is poured into the mold 7 to be molded, and a predetermined time is waited until the mixture is solidified (S14: solidification step).

Next, the solidified mixture, that is, the geopolymer solidified body molded by the mold 7 is demolded, and the geopolymer solidified body is crushed by the crusher 15 to be a powder or granule (S15A: crushing step). Next, the crushed geopolymer solidified body is placed in the drying unit 8 arranged in the second decompression chamber 9, and the drying of the geopolymer solidified body is started (S16: drying step). The subsequent steps are the same steps as the method for producing a solidified body of radioactive waste according to the first embodiment described above.

Here, in order to increase the production amount of the solidified geopolymer, it may be strongly desired to shorten the drying time. In addition, the storage place of radioactive waste such as the solidified geopolymer is limited, and it may be strongly desired to store more solidified geopolymer in the canister.

In the second embodiment, since the (mixture) of the solidified geopolymer is pulverized, the surface area of the solidified geopolymer is increased. Therefore, it becomes easy to dry the geopolymer solidified body. In addition, since a powdery granular solidified polymer can be obtained, it becomes possible to store the solidified solidified polymer in containers of various shapes, and the solidified solidified polymer becomes easy to handle. In addition, in the first embodiment, it is described that cracks should not be generated in the solidified body in order to keep the confinement performance high, but when the confinement performance of the geopolymer solidified body is sufficient even if pulverized, the pulverized It is possible to

In the second embodiment, the solidified geopolymer is pulverized before the drying step, but the solidified geopolymer may be pulverized after the drying step. By doing so, it is possible to store the powdered and granular geopolymer solidified bodies in the storage canisters 12 of various sizes and shapes. Further, the work becomes easy when the appropriate solidification treatment is performed again after the storage in the intermediate storage facility.

(Example)
Next, the experimental results when the test bodies (T1 to T9) of the solidified geopolymer are manufactured by the method for manufacturing the solidified body of radioactive waste will be described with reference to FIG.

In FIG. 5, the atmosphere of the depressurizing step during mixing and the depressurizing step during drying is set to 1 atm (atmospheric pressure), 0.8 atm, and 0.005 atm, and the temperature at the time of drying is 25° C. (room temperature) under each atmospheric pressure condition. , 90° C., 105° C., and the water content of the test piece prepared. Table 2 is a table in which the water content of the test body is described for each atmospheric pressure during mixing and drying and each heating temperature during drying.

In the examples, the composition (ratio) of each material to be added to the mixing unit 2 when manufacturing the solidified geopolymer is 30% by weight of aluminosilicate, 14% by weight of sodium silicate solution, and potassium hydroxide. 6 wt%, 5 wt% water, and 45 wt% simulated radioactive waste (for example, slurry waste).

Further, the mixture of the geopolymer material, the radioactive waste and water in the mixing section 2 was poured into the mold 7, and after being solidified, it was demolded and dried in the drying section 8. The geopolymer solidified body after demolding has a cylindrical shape with a size of φ50 mm×40 mm. These geopolymer solidified bodies were dried in the drying unit 8 for 28 hours. Further, a solidified body of the geopolymer was produced under various conditions of the atmospheric pressure of the mixing depressurization step and the drying decompression step and the temperature of the drying decompression step, and each test body was obtained. The drying period of each test body is 3 hours. A reduced pressure state was maintained for the entire drying period.

As shown in FIG. 5 and Table 2, as compared with the test body which was mixed and dried at 1 atm at any temperature, 0.8 atm and 0. It was confirmed that the water content of the test body set to 005 atm was low. That is, it is understood that the water in the solidified geopolymer can be removed more efficiently by performing the mixing and the drying in the reduced pressure environment.

Further, on the surface of the test body in which the drying temperature was set to 105° C., cracks that could be visually confirmed were scattered. On the other hand, there were no visually observable cracks on the surface of the test body whose drying temperature was set to 90°C.

Next, a test body (test body: T1) having a mixing temperature and a drying time of 1 atm and a drying temperature of 25° C. and a mixing and drying time of 0.005 atm and a drying temperature of 90° C. With respect to the test body (test body: T4) set to, a dissolution test for confirming the confinement property of the solidified body was performed. This dissolution test was carried out by a method in accordance with JIS K-0058-1, "Method for testing chemical substances of slags, Part 1 Dissolution test method". Specifically, a 10-fold amount of solvent (water) was added to the test specimen in a usable state, the mixture was stirred at 200 rpm for 6 hours, and the supernatant was filtered with a membrane filter having a pore diameter of 0.45 μm. The test solution was used. Then, the quantification of the elements contained in these test solutions was carried out by an inductively coupled plasma optical emission spectrometer (ICP-AES). Table 3 shows the measurement results. It was confirmed that the test body T4 had higher confinement performance than the test body T1.

According to the above-described embodiment, by having a drying step of forming a geopolymer solidified product by drying the mixed mixture in an environment lower than atmospheric pressure, it is necessary when manufacturing the geopolymer solidified product. Energy can be reduced.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and the gist of the invention.

1 (1A)... Solidified body manufacturing apparatus, 2... Mixing section, 4... First decompression chamber, 5... First decompression pump, 6... First removal filter, 7... Form, 8... Drying section, 9... Second Decompression chamber, 10... Second decompression pump, 11... Second removal filter, 12... Grinder, 12... Storage canister, 15... Grinder.

Claims (9)

A mixing step of mixing the geopolymer-forming material with the radioactive waste;
A solidification step of solidifying the mixture mixed in the mixing step,
A crushing step of crushing the mixture solidified in the solidifying step ,
A drying step of forming the geopolymer solidified product by drying the mixture ground in the grinding step in an environment lower than atmospheric pressure;
A method for producing a solidified product of radioactive waste containing. The method for producing a solidified product of radioactive waste according to claim 1, wherein the material forming the geopolymer contains at least a solidifying material and an alkali stimulant. The method for producing a solidified product of radioactive waste according to claim 1 or 2, further comprising a depressurizing step at the time of mixing for lowering the atmospheric pressure below atmospheric pressure during the mixing step. The method for producing a solidified product of radioactive waste according to any one of claims 1 to 3, wherein the atmospheric pressure is 0.8 atm or less in the drying step. The method for producing a solidified product of radioactive waste according to any one of claims 1 to 4, wherein the atmospheric pressure is set to 0.1 atm or less in the drying step. The method for producing a solidified product of radioactive waste according to any one of claims 1 to 5, wherein the mixture is dried at room temperature in the drying step. The method for producing a solidified product of radioactive waste according to any one of claims 1 to 6, wherein, in the drying step, the mixture is heated to be dried at a temperature lower than 100°C. The method for producing a solidified product of radioactive waste according to any one of claims 1 to 5, wherein in the drying step, the mixture is heated to be dried at a temperature of 100°C or higher. A molding step of pouring the mixture into a mold after the mixing step and before the drying step,
A demolding step of demolding the mixture molded by the mold,
The method for producing a solidified product of radioactive waste according to any one of claims 1 to 8, further comprising:

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