High-level radioactive material processing system and method

Abstract

To make minor actinoid a solid body in a more stable state.SOLUTION: A high level radioactive substance processing system comprises: a uranium supply part which supplies uranium to liquid from which at least one of minor actinoid and lanthanoid is extracted; and a solidification and stabilization processing part which causes one device to execute solidification processing of creating a solidified body obtained by heating the liquid to which the uranium is supplied and from which the minor actinoid and the lanthanoid are extracted, vaporizing partial liquid, heating and solidifying the liquid, and stabilization processing of sintering the generated solidified body, removing a portion or all of carbon, hydrogen, oxygen and nitrogen components and generating a fluorite structure of uranium dioxide which takes the minor actinoid and the lanthanoid therein.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a high-level radioactive material processing system and a high-level radioactive material processing method. [Background technology]

[0002] As a method for treating high-level radioactive waste, there is a method for extracting minor actinides, which are radioactive substances, from high-level radioactive materials (e.g., Patent Document 1 and Patent Document 2). In addition, there is a solidification method as a treatment method for storing spent fuel in a recyclable form (e.g., Patent Document 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-63198 A [Patent Document 2] JP 2019-15533 A [Patent Document 3] Patent No. 6037168 Summary of the Invention [Problem to be solved by the invention]

[0004] By extracting minor actinides from high-level radioactive materials, the extracted minor actinides can be reused as fuel for fast breeder reactors and other reactors. In addition, by removing the minor actinides, it is possible to reduce the waste treatment burden. Here, in order to reuse minor actinides as fuel, minor actinide combustion technology is required. Furthermore, in situations where reuse technology has not yet been put to practical use, the separated minor actinides need to be stored stably for long periods of time.

[0005] The present disclosure has been made in consideration of the above, and has an object to provide a high-level radioactive material processing system and a high-level radioactive material processing method that can convert minor actinides into a solid in a more stable state. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the objects, the present disclosure provides a radioactive material treatment device that includes a uranium supplying unit that supplies uranium to a liquid from which at least one of a minor actinide and a lanthanide has been extracted, a solidification process in which uranium is supplied and the liquid from which the minor actinide and the lanthanide have been extracted is heated to evaporate some of the liquid, and then further heated to create a solidified body, and a stabilization process in which the solidified body thus created is sintered to remove some or all of the carbon, hydrogen, oxygen, and nitrogen components, and a fluorite structure of uranium dioxide having the minor actinide and the lanthanoid incorporated therein is created.

[0007] In order to solve the above-mentioned problems and achieve the objectives, the present disclosure provides a high-level radioactive material processing method, comprising the steps of: supplying uranium to a liquid from which at least one of minor actinides and lanthanides has been extracted; a solidification process in which the uranium is supplied and the liquid from which the minor actinides and lanthanoids have been extracted is heated to evaporate some of the liquid, and then further heated to create a solidified body; and a stabilization process in which, in a single apparatus, the solidified body thus produced is sintered to remove some or all of the carbon, hydrogen, oxygen, and nitrogen components, and a fluorite structure of uranium dioxide having the minor actinides and the lanthanoid incorporated therein is produced. Effect of the Invention

[0008] According to the present disclosure, minor actinides can be made into a more stable solid state. [Brief description of the drawings]

[0009] [Figure 1]FIG. 1 is a schematic diagram showing a schematic configuration of a high-level radioactive material treatment apparatus according to this embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a schematic configuration of a high-level radioactive material treatment apparatus according to another embodiment. [Diagram 3] FIG. 3 is a schematic diagram showing an example of the solidification stabilization processing unit. [Figure 4] FIG. 4 is a schematic diagram showing another example of the solidification stabilization processing unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the high-level radioactive material treatment device according to the present disclosure will be described in detail with reference to the drawings. The high-level radioactive material treatment device according to the present disclosure extracts MA (minor actinides) from high-level radioactive material, and vitrifies and stabilizes the MA. In addition, when lanthanides are contained in the high-level radioactive material, the high-level radioactive material treatment device extracts the lanthanides together with the minor actinides. In the present disclosure, "MA (minor actinides)" refers to transuranium elements belonging to actinides, excluding Pu. "Actinides" is a general term for elements with atomic numbers from 89 to 103. Minor actinides include, for example, Np (neptunium), Am (americium), and Cm (curium). "Ln (lanthanoid)" is a general term for elements with atomic numbers from 57 to 71.

[0011] FIG. 1 is a schematic diagram showing a schematic configuration of a high-level radioactive material treatment device of this embodiment. The high-level radioactive material treatment device (treatment device) 10 shown in FIG. 1 includes an extraction device 12, a solidification and stabilization device 13, and a storage device 18. The solidification and stabilization device 13 includes a solidification device 14 and a stabilization device 16. The treatment device of this embodiment will be described in the case where high-level radioactive waste (hereinafter also referred to as "HALW") is used as the high-level radioactive material. The waste liquid is, for example, a liquid obtained after U (uranium) and Pu (plutonium) are recovered from a solution of spent nuclear fuel discharged from a light water reactor in the reprocessing of the spent nuclear fuel. The high-level radioactive waste contained in the waste liquid includes fission products (hereinafter also referred to as "FP"), MA, and lanthanoids. Specifically, the high-level radioactive waste (hereinafter also referred to as "HALW") is a waste liquid generated in reprocessing by the PUREX method. In the Purex process, a nitric acid solution containing U and Pu is contacted and mixed with tributyl phosphate (TBP) and an organic solvent such as dodecane. As a result, U and Pu in the nitric acid solution form complexes with TBP and move to the organic solvent. Meanwhile, FP, MA, and Ln remain in the nitric acid solution (waste liquid). The nitric acid solution containing FP, MA, and Ln becomes the waste liquid to be treated.

[0012] The extraction apparatus 12 extracts MA components from waste liquid. The extraction apparatus 12 includes a waste liquid supply unit 22, an extractant supply unit 24, a diluent supply unit 26, and an MA extract liquid production unit 28. The waste liquid supply unit 22 stores HALW, which is liquid high-level radioactive waste, and supplies it to the MA extract liquid production unit 28. In this embodiment, the extractant supply unit 24 and the diluent supply unit 26 are provided, but the extractant supply unit 24 and the diluent supply unit 26 may be combined into a single device to supply a liquid phase organic solvent in which the extractant is dissolved.

[0013] The extractant supply unit 24 supplies the extractant to the MA extractant generating unit 28. The extractant captures MA and Ln. The extractant is a liquid that migrates to the dilution liquid and mixes uniformly. For example, a complexing agent that forms a complex with MA or Ln can be used as the extractant. The complexing agent is preferably less expensive than a complexing agent that selectively forms a complex with MA. Examples of the extractant include n-octyl(phenyl)-N,N'-diisobutylcarbamoylmethylphosphine oxide-tributyl phosphate mixture (CMPO-TBP mixture), diisodecyl phosphate, 6,6'-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2'-bipyridine (BTBP), and N,N'-dibutyl-N,N'-dimethyltetradecylmalonamide (DMDBTDMA). As the extractant, it is preferable to use a DGA-based material (complexing agent). Specific examples of the complexing agent include N,N,N',N'-tetraoctyl-3-oxapentanediamide (TODGA), tetra(2-ethylhexyl)diglycolamide (T2EHDGA), etc. The extractant may be used alone or in combination of two or more.

[0014] The diluent supplying unit 26 supplies the diluent to the MA extract generating unit 28. The diluent is an organic phase material (organic solvent) that is insoluble in the liquid component of the waste liquid. The organic solvent can be appropriately selected depending on the extractant used. It is desirable that the organic solvent is reusable, inexpensive, and resistant to radiation degradation. The diluent is an organic phase material that is insoluble in the liquid component of the waste liquid. The diluent has a property of eluting the extractant from the liquid of the waste liquid. The diluent preferably has a boiling point of 30°C or more and 100°C or less. In addition, it is preferable that the diluent does not have a flash point or has a flash point of 150°C or more. By using a liquid that satisfies the above range as the diluent, the processing load in the solidification processing unit can be reduced. In addition, the diluent is preferably a material that is less deteriorated by heat or radiation even when reused, and is preferably a solvent having a hydrocarbon structure that is less deteriorated by heat or radiation even when reused. Here, being less degraded by heat or radiation even when reused means that even if it is exposed to heat or radiation energy and becomes a low molecular weight structure, it has the property of being difficult to form a complex with a metal ion. For example, hydrofluorocarbon (HFC) is preferably used as the diluent. One type of organic solvent may be used alone, or two or more types may be used in combination. In addition, it is preferable that the diluent is separated from the MA in the solidification device 14 and then made into a liquid that can be reused.

[0015] The MA extract generating unit 28 is supplied with waste liquid, an extractant, and a diluent. When the MA and Ln in the waste liquid are brought into contact with the extractant by the solvent extraction method, the MA and Ln migrate to the extractant side. The extractant that has captured MA and Ln is encapsulated in the diluent. After the extraction process, the MA extract generating unit 28 separates the diluent from the waste liquid to generate an MA extract in which the extractant that has captured MA and Ln is encapsulated in the diluent. The MA extract generating unit 28 may be a continuous type in which each material is continuously supplied and an MA extract is generated, or a batch type in which each material is intermittently supplied and an MA extract is generated. The MA extract generating unit 28 may selectively capture MA with the extractant, or may simultaneously capture and process MA and Ln.

[0016] Next, the solidification stabilization processing device 13 will be described. The solidification stabilization processing device 13 includes a solidification device 14 and a stabilization device 16. The solidification stabilization processing device 13 performs the heat treatment of the solidification device 14 and the stabilization device 16 in one device. The configuration of the device that performs the heat treatment of the solidification stabilization processing device 13 will be described later.

[0017] The solidification device 14 mixes uranium with the MA extraction liquid, removes liquid components from the mixed liquid, and produces a solidified body. The solidification device 14 includes a solidification processing unit 40 and a uranium supplying unit 44. The uranium supplying unit 44 supplies uranium to the MA extraction liquid in the solidification processing unit 40. The uranium supplying unit 44 supplies a uranium-containing substance that is uniformly soluble in the diluent (organic solvent) that constitutes the MA extraction liquid, such as an organic U complex, specifically a uranium complex of dipivaloylmethane. The uranium in the organic U complex is contained in a valence state of tetravalent or hexavalent.

[0018] The solidification treatment section 40 includes a distillation section 45, a heat treatment section 46, a diluent recovery section 47, an oxidizing gas supply section 48, and an exhaust gas recovery section 49. The distillation section 45 heats the MA extract mixed with uranium to, for example, 50°C to 100°C to evaporate the diluent. The heat treatment section 46 is an apparatus integrated with the distillation section 45, and further heats the object from which the diluent has been evaporated, for example, to 300°C, to thermally decompose the residue and convert it to an oxide. The diluent recovery section 47 is connected to the distillation section 45 and recovers the diluent evaporated in the dilution section 45. The diluent recovery section 47 supplies the recovered diluent to the diluent supply section 26 for reuse. The oxidizing gas supply section 48 supplies an oxidizing gas, for example, oxygen or air, to the heat treatment section 46. The exhaust gas supply section 49 recovers the exhaust gas discharged from the heat treatment section 46.

[0019] The solidification processing unit 40 distills the MA extract mixed with uranium in the distillation unit 45 to remove the dilution liquid components. By removing the dilution liquid, the solidification processing unit 40 leaves a solidified residue containing the extractant, MA, Ln, and uranium as a complex. The solidification processing unit 40 also recovers the gas discharged during distillation in the distillation unit 45 in the dilution liquid recovery unit 47. The solidification processing unit 40 heats the target obtained by distilling the dilution liquid in the heat treatment unit 46 while supplying an oxidizing gas from the oxidizing gas supply unit 48, thereby removing the components of the extractant, specifically, C, N, O, and H, and generating a solidified body. The solidified body becomes an oxide. The solidification processing unit 40 can use known evaporation methods such as a batch type (batch type) and a continuous type (plate tower or packed tower) for distillation and heat treatment. The distillation unit 45 preferably sets the treatment temperature to a boiling point of the dilution liquid of the MA extract liquid at a temperature between -10°C and +20°C, and below the flash point, based on the boiling point of the dilution liquid. The temperature in the heat treatment section 46 is equal to or higher than the temperature at which the thermal decomposition process and the oxide conversion process occur, for example, 300° C. or higher.

[0020] The stabilization device 16 performs a stabilization treatment for removing a part or all of the carbon, hydrogen, oxygen, and nitrogen components from the solidified body. The stabilization device 16 includes a stabilization treatment section 50.

[0021] The stabilization treatment section 50 includes a reduction section 52, a reducing gas supply section 54, and an exhaust gas recovery section 56. The reduction section 52 heats the solidified body in a reducing atmosphere to calcinate and sinter it. The reduction section 52 is an integrated device with the distillation section 45 and the heat treatment section 46. The reducing gas supply section 54 supplies a reducing gas, such as hydrogen, to the reduction section 52. The exhaust gas recovery section 56 recovers the exhaust gas discharged from the reduction section 52.

[0022] The stabilization treatment unit 50 supplies reducing gas from the reducing gas supply unit 54 to the reducing unit 52 while heating, calcining, and sintering the solidified body in the reducing unit 52, thereby removing some or all of the carbon, hydrogen, oxygen, and nitrogen components from the treatment target and solidifying it into a fluorite structure. Specifically, the stabilization treatment unit 50 sinters the solidified body to perform denitration and pyrolysis treatment, remove impurity components (organic components, nitric acid components, moisture) in the solidified body, i.e., CHON components, and then sinters it. The sintering temperature is, for example, 600°C or higher and 800°C or lower.

[0023] The stabilization treatment unit 50 removes impurities from the solidified body containing uranium, and then sinters it in a reducing atmosphere to obtain uranium oxide having a fluorite structure in which MA and Ln are dissolved. 3+ ·(NO3 - )3·m(extractant)]+([U 4+ ·(NO3 - )4·n(ligand)] or [M 3+ ·(NO3 - )3·m(extractant)]+([UO2 2+ ·(NO3 - )2·n(ligand)] is generated, where M is MA or Ln. By heat treating this solidified body and removing the CHON component, M a O b +U3O8+(αCO2+βH2O+γNO x ) and (αCO2 + βH2O + γNO x ) is removed. Furthermore, M a O b +U3O8 is sintered to form an oxide with a fluorite structure, UM RM O y is formed. RM is M(Ln or MA) / U, which is the equivalence ratio of LnorMA to U. The stabilization device 16 removes some or all of the carbon, hydrogen, oxygen, and nitrogen components that may gasify during storage, and turns the uranium dioxide into a fluorite structure containing MA and Ln, resulting in a solidified body with high thermal and chemical stability.

[0024] The storage device 18 stores the stabilized material. The storage device 18 includes a storage section 60. The storage section 60 stores the stabilized MA-containing material in a solid state. The storage section 60 is, for example, a cask. The storage section 60 may also be provided underground, and the stabilized material may be buried underground.

[0025] The MA-containing material stored in the storage unit 60 of the processing system 10 can be used as fuel for a nuclear power generation system. When burning MA as fuel, the stored solidified body with a fluorite structure is melted to generate a solution containing U, MA, and Ln (solidified body melting). Next, the obtained solution is subjected to a purification process for U and MA (MA purification). In MA purification, for example, U and MA and Ln in the obtained solution are separated, and highly exothermic MA is separated from MA as necessary. Next, the obtained U and MA (Np, Am, etc.) are mixed with U and Pu to obtain a mixed oxide, thereby producing fuel (MA fuel production). The obtained fuel is burned in a fast breeder reactor or the like (MA combustion).

[0026] In the processing device 10 of this embodiment, an extractant and a diluent are added to the waste liquid and mixed in the extraction device 12, thereby performing a separation process to separate MA together with Ln from the waste liquid, and produce an MA extract. Next, in the solidification device 14, the processing device 10 distills the diluent from the MA extract and supplies U, thereby producing a solidified body containing U, MA, and Ln. Next, in the stabilization device 16, the processing device 10 forms a fluorite structure from the solidified body containing MA by removing organic components (CHON). The processing device 10 stores the processed product with the fluorite structure in the storage device 18.

[0027] The processing apparatus 10 can simplify the apparatus configuration by performing the heat treatment of the solidification stabilization apparatus 13 in one apparatus. In addition, the processing apparatus 10 can perform multiple processes in one apparatus, thereby reducing the number of times radioactive materials need to be transported, and processing can be performed more safely.

[0028] In addition, by using a diluent with a boiling point of 30°C or higher and 100°C or lower, or with no flash point or with a flash point of 150°C or higher, the diluent can be easily recovered by solidification treatment and the required energy can be reduced.

[0029] The processing device 10 separates, solidifies, and stabilizes MA together with Ln. This allows MA to be efficiently extracted from liquid high-level radioactive waste, reducing the waste disposal load, and solidifying it. Furthermore, by extracting MA and Ln and making them into a stabilized substance, the MA can be stably stored even when it is stored for reuse as fuel. Furthermore, when it is reused, it is possible to make it reusable by simply dissolving the solidified body.

[0030] Furthermore, by processing MA and Ln without separating them, the process of separating MA and Ln becomes unnecessary, and the processing load can be reduced.

[0031] In addition, the processing device 10 preferably uses an extractant that does not form a third phase when producing an MA extract from highly radioactive materials containing nitric acid-based substances. Specifically, it is preferable to use a DGA-based material. One example is T2EHDGA. Furthermore, it is preferable that the extractant is a material that can be removed during processing in the stabilization device 16, specifically, a material that is composed only of carbon, hydrogen, nitrogen, and oxygen. Furthermore, it is preferable that the extractant does not contain any corrosive components.

[0032] Moreover, the processing device 10 supplies uranium to the liquid containing MA and Ln in the uranium supply unit 44, generates a solidified body, and then sinters it in the stabilization device 16, thereby forming a fluorite structure of uranium dioxide in which MA and Ln are fixed. This allows a long-term stable crystal structure to be formed as a solid after stabilization processing, and MA can be stably stored. Specifically, trivalent MA and Ln can be solid-dissolved in the fluorite structure, and a stable fluorite structure can be formed compared with a mixture of MA and Ln or an oxide structure of only one of them. Furthermore, by forming a crystal structure using uranium, when a solid containing MA is reprocessed and used, it is possible to form a structure that is free of unnecessary components such as Si, Na, Ca, etc. This allows a substance to be stabilized in a state that is easy to use during reprocessing.

[0033] It is preferable that the uranium supply unit 44 supplies uranium in the form of an organic substance complex. This makes it easier to dissolve the uranium in the diluent. Here, it is preferable to use a ligand that is coordinated to the organic U complex and that is composed only of carbon, hydrogen, nitrogen, and oxygen. It is also preferable that the ligand that is coordinated to the organic U complex is easy to stabilize (thermally decompose) and does not contain corrosive components. This allows it to be suitably removed during the stabilization process, and the MA-containing substance can be made into a stabilized substance, which can be stored stably.

[0034] In the above embodiment, the extractor 12 produces an MA extract by extracting with an organic solvent and performs a solidification process, but the present invention is not limited to this. The processing device may produce a stripped liquid by extracting MA in a liquid phase, and solidify and stabilize the stripped liquid.

[0035] Fig. 2 is a schematic diagram showing a schematic configuration of a high-level radioactive material treatment device of another embodiment. A high-level radioactive material treatment device (treatment device) 10A shown in Fig. 2 includes an extraction device 12A, a solidification and stabilization device 13A, and a storage device 18. The solidification and stabilization device 13A includes a solidification device 14A and a stabilization device 16A. The treatment device 10A of this embodiment will be described as a case in which high-level radioactive waste (hereinafter, also referred to as "HALW") is used as the high-level radioactive material, similar to the treatment device 10.

[0036] The extraction apparatus 12A extracts MA components from waste liquid. The extraction apparatus 12A includes a waste liquid supply unit 22, an extractant supply unit 24, a diluent supply unit 26, an MA extract liquid production unit 28, an MA strip-extraction liquid production unit 30, a strip-extractant supply unit 32, and a diluent supply unit 34. The waste liquid supply unit 22 stores HALW, which is liquid high-level radioactive waste, and supplies it to the MA extract liquid production unit 28.

[0037] The extractant supply unit 24 supplies the extractant to the MA extractant generating unit 28. The extractant captures MA and Ln. The extractant is a liquid that transfers to the dilution liquid. For example, a complexing agent that forms a complex with MA or Ln can be used as the extractant. The complexing agent is preferably cheaper than the complexing agent that selectively forms a complex with MA. Examples of the extractant include n-octyl(phenyl)-N,N'-diisobutylcarbamoylmethylphosphine oxide-tributyl phosphate mixture (CMPO-TBP mixture), diisodecyl phosphate, 6,6'-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2'-bipyridine (BTBP), and N,N'-dibutyl-N,N'-dimethyltetradecylmalonamide (DMDBTDMA). It is preferable to use a DGA-based material (complexing agent) as the extractant. Specific examples of the complexing agent include N,N,N',N'-tetraoctyl-3-oxapentanediamide (TODGA), tetra(2-ethylhexyl)diglycolamide (T2EHDGA), etc. The extracting agent may be used alone or in combination of two or more kinds.

[0038] The diluent supply unit 26 supplies the diluent to the MA extract production unit 28. The diluent is an organic phase material (organic solvent) that is insoluble in the liquid components of the waste liquid. The organic solvent can be appropriately selected depending on the extractant used. It is desirable that the organic solvent is reusable, inexpensive, and resistant to radiation degradation. A specific example of the organic solvent is n-dodecane. One type of organic solvent may be used alone, or two or more types may be used in combination. In addition, it is preferable that the diluent is separated from MA in the MA stripping liquid production unit 30 and then made into a reusable liquid.

[0039] The MA extract generating unit 28 is supplied with waste liquid, an extractant, and a diluent. When the MA and Ln in the waste liquid are brought into contact with the extractant by the solvent extraction method, the MA and Ln migrate to the extractant side. The extractant also migrates to the diluent side. The MA extract generating unit 28 separates the diluent from the waste liquid after the extraction process to generate an MA extract, which is an extractant that captures MA and Ln. The MA extract generating unit 28 may be a continuous type in which each material is continuously supplied and an MA extract is generated, or a batch type in which each material is intermittently supplied and an MA extract is generated. In this embodiment, the extractant supply unit 24 and the diluent supply unit 26 are provided, but the extractant supply unit 24 and the diluent supply unit 26 may be combined into one device to supply an organic solvent in a liquid phase in which the extractant is dissolved.

[0040] The MA stripping liquid production unit 30 is supplied with the MA extract from the MA extract production unit 28 and with the stripping agent from the stripping agent supply unit 32 .

[0041] The stripping agent supplying unit 32 supplies a substance that transfers MA and Ln from the MA extract to the liquid phase as a stripping agent. The stripping agent is, for example, nitric acid. The stripping agent is diluted with a diluent of the liquid phase, for example, water. The hydrothermal treatment promoter supplying unit 34 supplies the hydrothermal treatment promoter to the MA stripping agent generating unit 30. The hydrothermal treatment promoter is a neutral to basic liquid and is a reducing agent composed of CNOH, for example, an aldehyde compound, an amine compound, etc. Here, the preparation of the mixture of the MA extracting agent, the stripping agent, and the hydrothermal treatment promoter is not limited to this embodiment. The hydrothermal treatment promoter supplying unit 34 may supply the stripping agent to the MA extract, and supply the hydrothermal treatment promoter to the MA stripping agent.

[0042] The MA stripping solution generator 30 brings the MA extract into contact with a diluent containing a stripping agent, and transfers the MA and Ln contained in the organic phase MA extract to the diluent containing a stripping agent. The extraction device 12A may reuse the organic solvent (extractant and diluent) in the MA extract after treatment. The MA stripping solution generator 30 controls the acid concentration of the liquid and the amount of stripping solution to set the component ratio during treatment in the solidification treatment 14A to a predetermined ratio.

[0043] Next, the solidification stabilization processing device 13A will be described. The solidification stabilization processing device 13A includes a solidification device 14A and a stabilization device 16A. The solidification stabilization processing device 13A performs the heat treatment of the solidification device 14A and the stabilization device 16A in one device. The configuration of the device that performs the heat treatment of the solidification stabilization processing device 13A will be described later.

[0044] The solidification device 14A supplies uranium to the MA stripping solution, removes liquid components from the mixed liquid, and produces a solidified body. The solidification device 14A includes a solidification processing unit 40A and a uranium supplying unit 44A. The uranium supplying unit 44A supplies uranium to the MA stripping solution in the solidification processing unit 40A. The uranium supplying unit 44A supplies a uranium-containing material that is uniformly soluble in the liquid phase solvent that constitutes the MA stripping solution. Uranium dissolves in the liquid phase in a valence state of tetravalent or hexavalent.

[0045] The solidification treatment section 40A includes a hydrothermal treatment section 45A, a heat treatment section 46A, an exhaust gas recovery section 47A, an oxidizing gas supply section 48A, and an exhaust gas recovery section 49A. The hydrothermal treatment section 45A heats the MA stripping liquid mixed with uranium to, for example, 80°C to 150°C, causing hydrothermal treatment and oxide conversion treatment, and evaporating the liquid components. The liquid components also include a hydrothermal treatment promoter. The heat treatment section 46A is an apparatus integrated with the hydrothermal treatment section 45A, and further heats the object from which the liquid has been evaporated, for example to 300°C, to thermally decompose the residue. The exhaust gas recovery section 47A is connected to the hydrothermal treatment section 45A and recovers the exhaust gas evaporated by the hydrothermal treatment section 45A. The oxidizing gas supply section 48A supplies an oxidizing gas, for example, oxygen or air, to the heat treatment section 46A. The exhaust gas supply section 49A recovers the exhaust gas discharged from the heat treatment section 46A.

[0046] The solidification processing unit 40A performs hydrothermal synthesis of the MA stripping solution mixed with uranium in the hydrothermal processing unit 45A to form a solidified material containing MA and uranium. The solidified body and the dilution liquid component are separated into solid and liquid to remove the liquid component. In addition, the hydrothermal reaction can be promoted by adding a hydrothermal processing accelerator. The solidification processing unit 40A heats the target from which the liquid has been removed and which has been oxidized in the heat processing unit 46A while supplying an oxidizing gas from the oxidizing gas supply unit 48A, thereby removing the components of the extractant, specifically, C, N, O, and H, components, to generate a solidified body. The solidified body contains U, MA, and Ln. Specifically, the solidified body contains UO2 and M oxide precursors. The M oxide precursors are MOOH, M(OH)3, etc. M is at least one of MA and Ln. The hydrothermal processing unit 45A may have a hydrothermal treatment temperature of 80°C or more and 150°C or less, and a treatment time of 0.5 h or more and 20 h or less, for example. The heat treatment section 46 is heated to a temperature equal to or higher than the temperature at which pyrolysis occurs, for example, 300° C. or higher.

[0047] The stabilization device 16A performs a stabilization process to remove all or part of the carbon, hydrogen, oxygen, and nitrogen components from the solidified body and generate a solidified body having a fluorite structure. The stabilization device 16A has a stabilization processing unit 50A.

[0048] The stabilization treatment section 50A includes a reduction section 52A, a reducing gas supply section 54A, and an exhaust gas recovery section 56A. The reduction section 52A heats the solidified body in a reducing atmosphere, calcines it, and sinters it. The reduction section 52A is an integrated device with the distillation section 45A and the heat treatment section 46A. The reducing gas supply section 54A supplies a reducing gas, such as hydrogen, to the reduction section 52A. The exhaust gas recovery section 56A recovers the exhaust gas discharged from the reduction section 52A.

[0049] The stabilization treatment unit 50A supplies reducing gas from the reducing gas supply unit 54 to the reduction unit 52A, while heating, calcining, and sintering the solidified body in the reduction unit 52A, thereby solidifying the object to be treated into a fluorite structure. Specifically, the stabilization treatment unit 50A sinters the solidified body to perform denitration and pyrolysis treatment, remove impurity components (organic components, nitric acid components, and moisture) in the solidified body, i.e., CHON components, and then sinters it. The sintering temperature is, for example, 600°C or higher and 800°C or lower.

[0050] The stabilization processing unit 50A removes impurity components from the solidified body containing uranium, and then sinters it to obtain uranium oxide with a fluorite structure containing MA and Ln as a solid solution. The stabilization device 16A removes some or all of the carbon, hydrogen, oxygen, and nitrogen components that may gasify during storage, and turns the solidified body into a fluorite structure of uranium dioxide containing MA and Ln, resulting in a solidified body with high thermal and chemical stability.

[0051] The storage device 18 stores the stabilized material. The storage device 18 includes a storage section 60. The storage section 60 stores the stabilized MA-containing material in a solid state. The storage section 60 is, for example, a cask. The storage section 60 may also be provided underground, and the stabilized material may be buried underground.

[0052] The processing device 10A of this embodiment performs extraction and stripping in the extraction device 12A, processes a solution containing MA in the liquid phase, supplies uranium, and converts MA and Ln into a fluorite structure of uranium dioxide in which the uranium dioxide is fixed in the stabilization device 16A.

[0053] The processing apparatus 10A can simplify the apparatus configuration by performing the heat treatment of the solidification and stabilization apparatus 13 in one apparatus. In addition, since the processing apparatus 10A can perform multiple processes in one apparatus, it is possible to reduce the transportation of radioactive materials and perform processing more safely.

[0054] Furthermore, even in the case of performing back extraction, by forming the fluorite structure, the solid after stabilization treatment can have a long-term stable crystal structure, and MA can be stably stored. Specifically, trivalent MA and Ln can be dissolved in the fluorite structure, and the stable fluorite structure can be made even more stable. Furthermore, by forming a crystal structure using uranium, when a solid containing MA is reprocessed for use, it is possible to obtain a structure that is free of unnecessary components such as Si, Na, Ca, etc. This allows the substance to be stabilized in a state that is easy to use during reprocessing. Furthermore, the processing device 10A can obtain various effects similar to those of the processing device 10.

[0055] The uranium supply unit 44 of the processing device 10, 10A preferably supplies uranium in an amount equal to or greater than the total molar amount of minor actinides and lanthanides contained in the liquid extracted by the extraction device, thereby making the structure more stable than the fluorite structure of the solid material during storage.

[0056] Next, an example of a solidification stabilization processing unit will be described with reference to Fig. 3. Fig. 3 is a schematic diagram showing an example of a solidification stabilization processing unit. The solidification stabilization processing unit 100 shown in Fig. 3 is a unit in the solidification stabilization apparatus that performs processing after adding uranium, that is, heat treatment. In other words, the solidification stabilization processing unit 100 is the portion of the solidification apparatus 14 (14A) and the stabilization apparatus 16 (16A) excluding the uranium supply unit 40.

[0057] The solidification stabilization treatment unit 100 (hereinafter also referred to as treatment unit 100) continuously treats the target material to generate a stabilized solid material. The treatment unit 100 includes a rotating drum 102, a heating furnace 104, a supply unit 106, a circulating gas supply unit 108, and a combustion air supply unit 110. The supply unit 106 supplies the target material to the rotating drum 102, i.e., the liquid extracted by the extraction devices 12, 12A and the uranium supplied from the uranium supply units 44, 44A.

[0058] The rotating drum 102 is a so-called rotary kiln that conveys the object toward the heating furnace 104 while rotating. The rotating drum 102 is rotated by a drive source around the center of the drum as an axis. The rotating drum 102 conveys the object to be treated from one side to the other. The conveying area of ​​the rotating drum 102 is divided into a distillation section 130 (hydrothermal treatment section 130A), a heat treatment section 132, and a reduction section 134 from the upstream side to the downstream side in the conveying direction. The treatment section 100 becomes the distillation section 130 when producing an MA extract as shown in FIG. 1, and becomes the hydrothermal treatment section 130A when producing an MA stripping agent as shown in FIG. 2. The position of division is not particularly limited. The rotating drum 102 moves the object from the upstream side to the downstream side, so that the object passes through the distillation section 130 (hydrothermal treatment section 130A), the heat treatment section 132, and the reduction section 134. Further, the rotating drum 102 has a structure in which the area corresponding to the distillation section 130 (hydrothermal treatment section 130A) can transport liquid.

[0059] The heating furnace 104 is a heat source for the treatment section 100, and is connected to the end of the outlet side of the rotating drum 102. The heating gas supply section 110 supplies a gas, such as heated air or nitrogen, for heating the rotating drum 102. The heating furnace 104 may be supplied with air and fuel to be burned in the heating furnace 104 from the heating gas supply section 110 and burned in the heating furnace 104. The heating furnace 104 increases the temperature inside the furnace with the heating gas, and radiant heat 112 from the furnace wall and structures arranged in the furnace is supplied to the rotating drum 102. The heating furnace 104 supplies heat to each of the distillation section 130 (hydrothermal treatment section 130A), heat treatment section 132, and reduction section 134 of the rotating drum 102, and heats the treatment target in each area to a predetermined temperature. In addition, the heating furnace 104 discharges the heating gas and the gas that has passed through the rotating drum 102 as exhaust gas 114.

[0060] The circulating gas supply unit 108 supplies gas into the rotating drum 102, such that the gas flows from the supply unit 106 toward the heating furnace 104. The circulating gas is preferably an inert gas.

[0061] The rotary drum 102 is also provided with a dilute gas recovery section 120, an oxidizing gas supply section 122, a reducing gas supply section 126, and an exhaust gas recovery section 128. The dilute gas recovery section 120 is connected to the downstream end of the distillation section 130 of the rotary drum 102. The dilute gas recovery section 120 is used when an MA extract is used. The dilute gas recovery section 120 recovers a gas containing the components of the dilute liquid that have been heated and evaporated in the distillation section 130. The dilute gas recovery section 120 recovers the components of the dilute liquid from the recovered gas. When a part of the upstream side of the rotary drum 102 is used as the hydrothermal treatment section 130A, the rotary drum 102 may be configured without the dilute gas recovery section 120. The oxidizing gas supply section 122 is disposed at the upstream end of the thermal treatment section 132 of the rotary drum 102, and supplies an oxidizing gas to the rotary drum 102. The reducing gas supply unit 126 is disposed at the upstream end of the reduction unit 134 of the rotating drum 102, and supplies reducing gas to the rotating drum 102. The exhaust gas recovery unit 128 recovers the exhaust gas discharged from the heating furnace 104.

[0062] The processing section 100 heats the object to be processed in each region while transporting it on the rotating drum 102, and further supplies and collects the necessary gas in each region, thereby allowing the solidification and stabilization of the object to be processed to be performed continuously in one device. This allows the heat source in the device to be used effectively, and eliminates the need to transport the object to be processed separately for each process.

[0063] Moreover, by treating the object to be treated while rotating it on the rotary drum 102, the treatment section 100 can suitably attach the solidified material obtained by evaporating the dilution liquid to the uranium particles supplied to the rotary drum 102 by the supply section 106 together with the liquid extracted by the extraction devices 12 and 12A, thereby making the treated object with a fluorite structure into granules. This allows the product to have a granular structure that is easy to manage.

[0064] The processing unit 100 may not include the diluent gas recovery unit 120 and may extract a component to be used as a diluent from the gas recovered by the exhaust gas recovery unit 128 .

[0065] Here, the solidification and stabilization treatment unit 100 shown in Fig. 3 is a rotary kiln, but the structure is not limited to this. In addition, the heat source may be a heating element wound around a rotating drum, or heated inert gas may be supplied.

[0066] Here, in Fig. 3, an example of a solidification stabilization processing unit that performs continuous processing has been described, but a batch type may also be used. An example of a batch type solidification stabilization processing unit will be described with reference to Fig. 4. Fig. 4 is a schematic diagram showing an example of a solidification stabilization processing unit.

[0067] 4 (hereinafter also referred to as the processing unit 200) processes objects in a batch manner to generate a stabilized solid object. The processing unit 200 includes a base unit 212, a support unit 214, a drive unit 216, a container 218, and a heat source 220.

[0068] The base unit 212 is a base formed at a position where the processing unit 200 is installed. The support unit 214 is fixed to the base unit 212 and supports the drive unit 216 and the container 218. The support unit 214 supports the drive unit 216 and the container 218 in a state in which they can rotate freely around the rotation axis of the drive unit 216. In addition, the support unit 214 may support the drive unit 216 and the container 218 so that they can rotate around an axis perpendicular to the rotation axis of the drive unit 216. The drive unit 216 is fixed to the support unit 214 and rotates the container 218. The container 218 is introduced with a processing object. The container 218 is provided with a lid, and the inside can be sealed. The inner surface of the container 218 is a curved surface that is convex to the bottom surface. In addition, the container 218 is supported by the support unit 214 with the central axis from the bottom of the container to the lid inclined with respect to the vertical direction. The heat source 220 heats the container 218. The heat source 220 is disposed vertically below the container 218, and heats the container 218 from the outer periphery of the container 218.

[0069] Further, an exhaust gas recovery unit 120A, an oxidizing gas supply unit 122A, a reducing gas supply unit 126A, and an exhaust gas recovery unit 128A are connected to the container 218. The exhaust gas recovery unit 120A recovers gas containing components of the liquid evaporated by the hydrothermal reaction. The oxidizing gas supply unit 122A supplies an oxidizing gas to the container 218. The reducing gas supply unit 126A supplies a reducing gas to the container 218. The exhaust gas recovery unit 128A recovers the exhaust gas discharged from the container 218.

[0070] The processing unit 200 starts processing by introducing the object to be processed, that is, the liquid extracted by the extraction device 12, 12A, and the uranium supplied from the uranium supply unit 44, 44A, into the container 218. The processing unit 200 may be equipped with a device for introducing the object to be processed and a device for opening and closing the lid of the container. After putting the object to be processed into the container 218 and closing the lid, the processing unit 200 rotates the container 218 with the drive unit 216 and heats it with the heat source 220. The processing unit 200 executes each process by switching the temperature and the gas supplied for each of the heating process, pyrolysis process, and reduction process.

[0071] As a result, the processing section 200 can perform the solidification and stabilization of the processing object in a single device and in a batch manner, making it possible to effectively utilize a single heat source and eliminating the need to transport the processing object for each process.

[0072] Moreover, the treatment unit 200 treats the object to be treated while rotating it in the container 218, so that the solidified material obtained by evaporating the diluting liquid can be favorably attached to the uranium particles contained in the object to be treated, and the treated object with a fluorite structure can be made into granules. This makes it possible to give the product a granular structure that is easy to manage.

[0073] Although the present invention has been described above by showing the embodiments, the present disclosure is not limited to the above embodiments. Each configuration and their combination in the above embodiments is an example, and addition, omission, substitution, and other modifications of the configuration are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0074] 10, 10A Processing System (High-level Radioactive Material Processing System) 12, 12A extraction device 13, 13A Solidification stabilization device 14, 14A solidification device 16, 16A stabilizer 18 Storage device 22 Waste liquid supply section 24 Extractant supply section 26 Diluent supply section 28 MA extract generation section 30 MA reverse extraction liquid generation section 34 Hydrothermal treatment accelerator supply section 40, 40A Solidification Processing Unit 44, 44A Uranium Supply Department 45, 45A Distillation section 46, 46A Heat treatment section 47, 47A Dilution fluid recovery section 48, 48A Oxidizing gas supply unit 49, 49A Exhaust gas recovery section 50, 50A stabilization processing section 52, 52A Reduction section 54, 54A Reducing gas supply unit 56, 56A Exhaust gas recovery section 60 Storage Department 100, 200 Solidification stabilization unit 102 Rotating Torso 104 Heating Furnace 106 Supply section 108 Circulating gas supply section 110 Heating gas supply section 112 Radiant heat 120, 120A Dilution gas recovery section 122, 122A Oxidizing gas supply unit 126, 126A Reducing gas supply unit 128, 128A Exhaust gas recovery section 130 Distillation Section 130A Hydrothermal treatment section 132 Heat Treatment Section 134 Reduction Section 212 Foundation 214 Support part 216 Drive Unit 218 Container 220 Heat source

Claims

1. a uranium supply unit that supplies uranium to the liquid from which at least one of minor actinides and lanthanides has been extracted; a solidification and stabilization treatment section which performs, in a single apparatus, a solidification treatment in which uranium is supplied, the liquid from which the minor actinides and the lanthanoids have been extracted is heated to evaporate a portion of the liquid, and then further heated to create a solidified body; and a stabilization treatment in which the solidified body thus created is sintered to remove some or all of the carbon, hydrogen, oxygen, and nitrogen components, and a fluorite structure of uranium dioxide having the minor actinides and the lanthanoids incorporated therein is created.

2. 2. The high-level radioactive material processing system according to claim 1, wherein the solidification and stabilization processing unit performs the solidification and stabilization processing in a batch manner.

3. 2. The high-level radioactive material processing system according to claim 1, wherein the solidification and stabilization processing unit performs the solidification and stabilization processing in succession.

4. 4. The high-level radioactive material processing system according to claim 1, wherein the solidification and stabilization processing unit includes an oxidizing gas supply unit that supplies oxygen or air during the solidification processing.

5. 5. The high-level radioactive material processing system according to claim 1, wherein the solidification stabilization processing unit includes a reducing gas supply unit that supplies a reducing gas during the stabilization processing.

6. 6. The high-level radioactive material processing system according to claim 1, wherein the uranium supply unit supplies uranium in an amount equal to or greater than the total molar amount of the minor actinide and the lanthanide contained in the extracted liquid.

7. an extraction device that uses an organic solvent liquid to extract the minor actinides and the lanthanides from a liquid containing a high-level radioactive material, extracts the organic solvent containing the minor actinides and the lanthanides, and supplies a dilution liquid to produce a diluted liquid; The high-level radioactive material processing system according to claim 1 , wherein the uranium supply unit adds a uranium complex that dissolves in the organic solvent to the liquid.

8. 8. The high-level radioactive material processing system according to claim 7, wherein the diluting liquid has a boiling point of 30°C or higher and 100°C or lower.

9. 9. The high-level radioactive material processing system according to claim 7 or 8, wherein the diluting liquid has no flash point or a flash point of 150° C. or higher.

10. an extraction device for extracting the minor actinides and the lanthanides from a liquid containing high-level radioactive materials using an organic solvent liquid, and then mixing the extracted organic solvent with a diluent containing a liquid-phase stripping agent to generate a liquid in which the minor actinides and the lanthanides have been transferred to the diluent containing the liquid-phase stripping agent; 7. The high-level radioactive material processing system according to claim 1, wherein the uranium supply unit adds uranium ions that dissolve in a liquid phase to the liquid.

11. The high-level radioactive material processing system according to claim 10 , wherein the solidification and stabilization processing section creates a solidified body by a heat treatment.

12. Supplying uranium to the liquid from which at least one of minor actinides and lanthanides has been extracted; A high-level radioactive material processing method comprising the steps of: a solidification treatment in which uranium is supplied, and a liquid from which the minor actinides and the lanthanoids have been extracted is heated to evaporate a portion of the liquid, and then further heated to create a solidified body; and a stabilization treatment in which the solidified body thus created is sintered to remove some or all of the carbon, hydrogen, oxygen, and nitrogen components, and to create a fluorite structure of uranium dioxide having the minor actinides and the lanthanoids incorporated therein, in a single apparatus.

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