JP2008014708A - Reprocessing method of spent nuclear fuel - Google Patents

Reprocessing method of spent nuclear fuel Download PDF

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JP2008014708A
JP2008014708A JP2006184546A JP2006184546A JP2008014708A JP 2008014708 A JP2008014708 A JP 2008014708A JP 2006184546 A JP2006184546 A JP 2006184546A JP 2006184546 A JP2006184546 A JP 2006184546A JP 2008014708 A JP2008014708 A JP 2008014708A
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fluoride
nuclear fuel
spent nuclear
solvent extraction
solid material
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JP4627517B2 (en
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Kuniyoshi Hoshino
国義 星野
Fumio Kawamura
文雄 河村
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Hitachi Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

<P>PROBLEM TO BE SOLVED: To avoid plutonium fluoride being deposited for no extraction of plutonium, with an increase in the fluoride ion content of a water solution in a solvent extracting process, in a reprocessing method of a spent nuclear fuel including the combination of a fluoride evaporation method and a solvent extraction method. <P>SOLUTION: The reprocessing method of a spent nuclear fuel includes the fluorinating process of causing fluorine or fluoride to react with the spent nuclear fuel to change part of or most of uranium into fluoride and the solvent extraction process of dissolving uranium, plutonium and other solid matter, remaining after the above process in an acid water solution for processing by the solvent extraction method, and a fluoride ion removing process of removing fluoride ions is provided in the process, before the solid matter is dissolved in the acid water solution. Precipitation of plutonium fluoride is inhibited in the solvent extraction process, by removing the fluoride ions after the fluorination process, to enhance the plutonium extraction efficiency. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、原子力発電所で発生する使用済み核燃料の再処理方法に関する。   The present invention relates to a method for reprocessing spent nuclear fuel generated in a nuclear power plant.

使用済み核燃料の再処理方法には、乾式法、湿式法、乾式法と湿式法を組み合わせた方法などがある。特許文献１には、使用済み核燃料に、まずフッ素またはフッ素化合物を作用させてウラン（Ｕ）の一部分あるいは大部分を揮発除去したのち、残ったＵ、プルトニウム（Ｐｕ）、その他の固体物を溶媒抽出法により処理する再処理方法が記載されている。   As a method for reprocessing spent nuclear fuel, there are a dry method, a wet method, a method combining a dry method and a wet method, and the like. In Patent Document 1, first, fluorine or a fluorine compound is allowed to act on spent nuclear fuel to volatilize and remove a part or most of uranium (U), and then the remaining U, plutonium (Pu), and other solid substances are used as solvents. A reprocessing method for processing by an extraction method is described.

特開２００２−２５７９８０号公報（要約）JP 2002-257980 A (summary)

乾式法と湿式法を組み合わせた方法は、高精製度の製品、特にＵとＰｕの混合酸化物を得る上で優れた方法である。しかし、この方法は、溶媒抽出工程において、フッ化物イオンの濃度が高くなると、Ｐｕのフッ化物が沈殿し、Ｐｕの抽出処理ができなくなることがわかった。また、溶媒抽出工程中の硝酸環境において、フッ化物イオンが共存すると、材料表面へ酸化皮膜が形成されなくなり、ステンレス鋼やジルコニウム等の再処理装置構成材料の腐食が加速され、装置寿命を低下させる問題があることがわかった。   The method combining the dry method and the wet method is an excellent method for obtaining a highly purified product, particularly a mixed oxide of U and Pu. However, it has been found that in this method, if the fluoride ion concentration is increased in the solvent extraction step, Pu fluoride precipitates and Pu extraction cannot be performed. In addition, if fluoride ions coexist in the nitric acid environment during the solvent extraction process, an oxide film will not be formed on the surface of the material, corrosion of reprocessing equipment components such as stainless steel and zirconium will be accelerated, and equipment life will be reduced. I found out there was a problem.

本発明の目的は、フッ化物揮発法と溶媒抽出法を組み合わせた使用済み核燃料の再処理方法において、湿式工程でＰｕのフッ化物が沈殿し、さらに湿式工程でのフッ化物イオンの混入を抑制して、Ｐｕの抽出効率の向上と装置構成材料の腐食防止を図った再処理方法を提供することにある。   The object of the present invention is to reduce the mixing of fluoride ions in the wet process by precipitating Pu fluoride in the wet process in the reprocessing method of spent nuclear fuel combining the fluoride volatilization method and the solvent extraction method. Thus, an object of the present invention is to provide a reprocessing method that improves the extraction efficiency of Pu and prevents corrosion of material constituting the apparatus.

本発明は、使用済み核燃料にフッ素またはフッ素化合物を作用させてウランの一部分あるいは大部分をフッ化物に転換して揮発除去するフッ化工程と、その後、残ったウラン、プルトニウム、その他の固体物を酸性水溶液に溶解し、溶媒抽出法により処理する溶媒抽出工程とを含む使用済み核燃料の再処理方法において、前記固体物を酸性水溶液に溶解する前段階でフッ化物イオンを除去するフッ化物イオン除去工程を設けたことを特徴とする。   In the present invention, a fluorination step in which fluorine or a fluorine compound is allowed to act on spent nuclear fuel to convert a part or most of uranium to fluoride to remove it by volatilization, and then the remaining uranium, plutonium and other solid substances are removed. In a method for reprocessing spent nuclear fuel comprising a solvent extraction step of dissolving in an acidic aqueous solution and processing by a solvent extraction method, a fluoride ion removing step of removing fluoride ions in a previous stage of dissolving the solid matter in an acidic aqueous solution Is provided.

フッ化処理後の固体物に含まれるフッ化物イオンを、湿式工程に移行する前に予め除去しておくことにより、固体物を湿式工程に移行させたときに水溶液中のフッ化物イオン濃度が高くなるのを防ぎ、Ｐｕフッ化物の沈殿が発生するのを抑制することができる。これにより、Ｐｕの抽出効率の向上を図ることができる。つまり、下記（１）式の化学反応式で、湿式工程の水溶液中のフッ化物イオン濃度が下がり、反応が右に移行し、ＰｕＦ４の濃度が低くなり、水溶液中の溶解度以下となれば、ＰｕＦ４の沈殿を防ぐことができる。 By removing the fluoride ions contained in the solid material after the fluorination treatment before moving to the wet process, the fluoride ion concentration in the aqueous solution is high when the solid material is transferred to the wet process. It is possible to prevent the precipitation of Pu fluoride. Thereby, the extraction efficiency of Pu can be improved. That is, in the chemical reaction formula of the following formula (1), if the fluoride ion concentration in the aqueous solution of the wet process decreases, the reaction shifts to the right, the concentration of PuF 4 decreases, and the solubility in the aqueous solution is below, Precipitation of PuF 4 can be prevented.

ＰｕＦ４⇔Ｐｕ４＋＋４Ｆ− ……（１）
また、湿式工程において、水溶液中のフッ化物イオンの濃度が下がることにより、フッ化物イオンが共存する硝酸環境による材料の腐食を防ぐことができる。 PuF 4 ⇔Pu 4+ + 4F − (1)
Further, in the wet process, the concentration of the fluoride ion in the aqueous solution is lowered, so that corrosion of the material due to the nitric acid environment where the fluoride ion coexists can be prevented.

本発明では、フッ化物イオンを除去するための第１の方法として、フッ化処理後の固体物に水蒸気を高温で作用させることにより、フッ化物を酸化物に転換し、フッ化物イオンをフッ化水素として除去することを提案する。この方法による化学反応式を（２）式に示す。ここで、Ｍは、Ｕ、Ｐｕ及び核分裂生成物を表す。   In the present invention, as a first method for removing fluoride ions, water vapor is allowed to act on the solid material after fluorination treatment at a high temperature, thereby converting the fluoride into an oxide and fluoridating the fluoride ions. It is proposed to remove it as hydrogen. The chemical reaction formula by this method is shown in Formula (2). Here, M represents U, Pu, and a fission product.

ｎＭｘＦｙ＋ｍＨ２Ｏ→ＭｎＯｍ＋２ｍＨＦ ……（２）
また、フッ化物イオンを除去するための第２の方法として、フッ化処理後の固体物を水に作用させて、水溶性のフッ化物を水に溶解させ、フッ化物イオンを水に移行させて除去することを提案する。この方法では、湿式工程に入る前の段階で、予め水溶性フッ化物である核分裂生成物を除去することができ、後段の湿式工程での核分裂生成物除去の負荷を低減することができる。フッ化処理後の固体物に含まれるＰｕＦ４及びフッ化されなかったウラン酸化物は、水に不溶のため沈殿物として回収することが可能である。 nM x F y + mH 2 O → M n O m +2 mHF (2)
In addition, as a second method for removing fluoride ions, a solid after fluorination treatment is allowed to act on water, water-soluble fluoride is dissolved in water, and fluoride ions are transferred to water. Suggest to remove. In this method, the fission product, which is a water-soluble fluoride, can be removed in advance before entering the wet process, and the load of removing the fission product in the subsequent wet process can be reduced. PuF 4 and unfluorinated uranium oxide contained in the solid after the fluorination treatment are insoluble in water and can be recovered as a precipitate.

また、フッ化物イオンを除去するための第３の方法として、上記の第１の方法と第２の方法を組み合わせることを提案する。具体的には、フッ化処理後の固体物に水蒸気を高温で作用させることによりフッ化物を酸化物に転換し、フッ化物イオンをフッ化水素として揮発除去する。水蒸気処理後の固体物には、水蒸気により酸化物に転換されなかったフッ化物が含まれる。そこで、次に水蒸気処理後の固体物を水に作用させ、酸化物に転換されなかったフッ化物のうち水溶性の化合物を水に溶解させ、フッ化物イオンを水に移行させて除去する。   In addition, as a third method for removing fluoride ions, it is proposed to combine the first method and the second method. Specifically, the fluoride is converted into an oxide by causing water vapor to act on the solid material after the fluorination treatment at a high temperature, and the fluoride ions are volatilized and removed as hydrogen fluoride. The solid material after the steam treatment includes a fluoride that has not been converted into an oxide by steam. Then, the solid substance after the steam treatment is allowed to act on water, and water-soluble compounds among the fluorides not converted to oxides are dissolved in water, and fluoride ions are transferred to water and removed.

本発明によれば、溶媒抽出工程においてＰｕフッ化物が沈殿するのを抑制し、Ｐｕ抽出効率の向上を図ることができる。また、溶媒抽出工程において、水溶液中でのフッ化物イオンの濃度を低く抑え、溶媒抽出工程での装置構成材料の腐食を防ぐことができる。   ADVANTAGE OF THE INVENTION According to this invention, it can suppress that Pu fluoride precipitates in a solvent extraction process, and can aim at the improvement of Pu extraction efficiency. In addition, in the solvent extraction step, the concentration of fluoride ions in the aqueous solution can be kept low, and corrosion of the device constituent materials in the solvent extraction step can be prevented.

以下、図面を用いて、本発明の実施例を説明する。   Embodiments of the present invention will be described below with reference to the drawings.

本発明の基本的な処理工程を、図１を用いて説明する。使用済み核燃料１を脱被覆粉体処理後、フッ化工程２において、フッ化反応層内でフッ化剤３としてフッ素ガスを供給し、使用済み核燃料のフッ化処理を行う。使用済み核燃料に含まれる大部分のＵはＵＦ６として揮発するので、この揮発したＵＦ６をＵ精製工程で精製しＵＦ６として回収する（ＵＦ６製品４）。一方、フッ化工程で揮発されなかった固体物は、フッ化物イオン除去工程５でフッ化物イオンを除去したのち、溶媒抽出工程６に送り、再処理して含Ｐｕ製品７として回収する。溶媒抽出工程６は、たとえば従来のピューレックス法が採用可能である。 The basic processing steps of the present invention will be described with reference to FIG. After the spent nuclear fuel 1 has been decoated and powdered, in a fluorination step 2, fluorine gas is supplied as a fluorinating agent 3 in the fluorination reaction layer, and the spent nuclear fuel is fluorinated. Since U Most contained in spent nuclear fuel volatility as UF 6, to recover the UF 6 that the volatilized as UF 6 and purified by U purification step (UF 6 products 4). On the other hand, the solid matter that has not been volatilized in the fluorination step is removed in the fluoride ion removal step 5 and then sent to the solvent extraction step 6 to be reprocessed and recovered as a Pu-containing product 7. The solvent extraction step 6 can employ, for example, a conventional Purex method.

本実施例によれば、フッ化物イオン除去工程５で予めフッ化物イオンを除去しているため、溶媒抽出工程６において水溶液中でのフッ化物イオンの濃度が低く抑えられ、Ｐｕフッ化物が沈殿するのを防ぐことができる。これにより、Ｐｕの抽出効率を向上させることができる。また、溶媒抽出工程６において水溶液中でのフッ化物イオンの濃度が低く抑えられることで、溶媒抽出工程での材料の腐食を防ぐことができる。   According to the present embodiment, since fluoride ions are removed in advance in the fluoride ion removal step 5, the concentration of fluoride ions in the aqueous solution is kept low in the solvent extraction step 6, and Pu fluoride is precipitated. Can be prevented. Thereby, the extraction efficiency of Pu can be improved. Further, since the concentration of fluoride ions in the aqueous solution is kept low in the solvent extraction step 6, corrosion of the material in the solvent extraction step can be prevented.

フッ化物イオンを除去する方法として、水蒸気を作用させる場合について、図２を用いて説明する。使用済み核燃料１を脱被覆粉体処理後、フッ化工程２において、フッ化反応層内でフッ化剤３としてフッ素ガスを供給し、使用済み核燃料のフッ化処理を行う。使用済み核燃料に含まれる大部分のＵはＵＦ６として揮発し、揮発したＵＦ６はＵ精製工程で精製されＵＦ６として回収される。一方、フッ化工程２で揮発されなかった固体物は、酸化物転換工程２１において、６００℃前後の高温に保持された反応炉内で水蒸気２２と反応させる。固体物であるフッ化化合物は（２）式の化学反応式により酸化物に転換され、反応生成物としてＨＦが生じる。ＨＦは気体として反応炉から除去（ＨＦ除去２３）される。反応炉としては、たとえばロータリーキルンが採用可能である。水蒸気処理された固体物は、溶媒抽出工程６に送られて再処理される。 As a method for removing fluoride ions, a case where water vapor is applied will be described with reference to FIG. After the spent nuclear fuel 1 has been decoated and powdered, in a fluorination step 2, fluorine gas is supplied as a fluorinating agent 3 in the fluorination reaction layer, and the spent nuclear fuel is fluorinated. Most U contained in the spent nuclear fuel is volatilized as UF 6 , and the volatilized UF 6 is refined in the U refining process and recovered as UF 6 . On the other hand, the solid matter that has not been volatilized in the fluorination step 2 is reacted with the water vapor 22 in the reaction furnace maintained at a high temperature of about 600 ° C. in the oxide conversion step 21. The fluorinated compound, which is a solid substance, is converted into an oxide by the chemical reaction formula (2), and HF is generated as a reaction product. HF is removed as a gas from the reactor (HF removal 23). As the reaction furnace, for example, a rotary kiln can be adopted. The steam-treated solid material is sent to the solvent extraction step 6 to be reprocessed.

本実施例では、酸化物転換工程２１で予めフッ化物イオンを除去しているため、溶媒抽出工程６において水溶液中でのフッ化物イオンの濃度が低く抑えられ、Ｐｕフッ化物が沈殿するのを防ぐことができる。これにより、Ｐｕの抽出効率を向上させることができる。また、溶媒抽出工程６において、水溶液中でのフッ化物イオンの濃度が低く抑えられることで、溶媒抽出工程での材料の腐食を防ぐことができる。   In this embodiment, since fluoride ions are removed in advance in the oxide conversion step 21, the concentration of fluoride ions in the aqueous solution is kept low in the solvent extraction step 6 to prevent precipitation of Pu fluoride. be able to. Thereby, the extraction efficiency of Pu can be improved. Further, in the solvent extraction step 6, the concentration of fluoride ions in the aqueous solution can be kept low, so that corrosion of the material in the solvent extraction step can be prevented.

フッ化物イオンを除去する方法として、水を作用させる場合について、図３を用いて説明する。使用済み核燃料１を脱被覆粉体処理後、フッ化工程２において、フッ化反応層内でフッ化剤３としてフッ素ガスを供給し、使用済み核燃料のフッ化処理を行う。使用済み核燃料に含まれる大部分のＵはＵＦ６として揮発し、揮発したＵＦ６はＵ精製工程で精製されＵＦ６として回収される。一方、フッ化工程で揮発されなかった固体物は、水洗浄工程３１において洗浄槽内で水３２と混合される。固体物に含まれるフッ化化合物のうち、水溶性の化合物は水に溶解し、フッ化物イオンが水中に移行する。固体物に含まれるＰｕＦ４及びフッ化されなかったウラン酸化物は、水に不溶のため沈殿物として回収する。水洗浄後の固体物は、溶媒抽出工程６に送られて再処理される。 As a method for removing fluoride ions, a case where water is applied will be described with reference to FIG. After the spent nuclear fuel 1 has been decoated and powdered, in a fluorination step 2, fluorine gas is supplied as a fluorinating agent 3 in the fluorination reaction layer, and the spent nuclear fuel is fluorinated. Most U contained in the spent nuclear fuel is volatilized as UF 6 , and the volatilized UF 6 is refined in the U refining process and recovered as UF 6 . On the other hand, the solid matter that has not been volatilized in the fluorination step is mixed with water 32 in the washing tank in the water washing step 31. Of the fluorinated compounds contained in the solid material, water-soluble compounds dissolve in water, and fluoride ions migrate into water. PuF 4 and unfluorinated uranium oxide contained in the solid matter are recovered as precipitates because they are insoluble in water. The solid after the water washing is sent to the solvent extraction step 6 to be reprocessed.

本実施例では、水洗浄工程３１で予めフッ化物イオンを除去しているため、溶媒抽出工程６において水溶液中でのフッ化物イオンの濃度が低く抑えられ、Ｐｕフッ化物が沈殿するのを防ぐことができる。これにより、Ｐｕの抽出効率を向上させることができる。また、溶媒抽出工程６において、水溶液中でのフッ化物イオンの濃度が低く抑えられることで、溶媒抽出工程での材料の腐食を防ぐことができる。さらに、予め水溶性フッ化物である核分裂生成物３３（水溶性ＦＰフッ化物：水溶性フィッションプロダクト）を除去することができ、後段の湿式工程での核分裂生成物除去の負荷を低減することができる。   In this embodiment, since fluoride ions are removed in advance in the water washing step 31, the concentration of fluoride ions in the aqueous solution can be kept low in the solvent extraction step 6 to prevent precipitation of Pu fluoride. Can do. Thereby, the extraction efficiency of Pu can be improved. Further, in the solvent extraction step 6, the concentration of fluoride ions in the aqueous solution can be kept low, so that corrosion of the material in the solvent extraction step can be prevented. Furthermore, the fission product 33 (water-soluble FP fluoride: water-soluble fission product), which is a water-soluble fluoride, can be removed in advance, and the burden of removing the fission product in the subsequent wet process can be reduced. .

フッ化物イオンを除去する方法として、水蒸気を作用させる方法と水を作用させる方法を組み合わせた場合について、図４を用いて説明する。使用済み核燃料１を脱被覆粉体処理後、フッ化工程２において、フッ化反応層内で、フッ化剤３としてフッ素ガスを供給し、使用済み核燃料のフッ化処理を行う。使用済み核燃料に含まれる大部分のＵはＵＦ６として揮発し、揮発したＵＦ６はＵ精製工程で精製されＵＦ６として回収される。一方、フッ化工程で揮発されなかった固体物は、酸化物転換工程２１において、６００℃前後の高温に保持された反応炉内で水蒸気２２と反応させる。（２）式の化学反応式により、フッ化化合物は酸化物に転換され、反応生成物としてＨＦが生じる。ＨＦは気体として反応炉から除去される。反応炉としては、たとえばロータリーキルンが採用可能である。水蒸気処理された固体物は、次に水洗浄工程３１に送られる。水蒸気処理後の固体物には、水蒸気により酸化物転換されなかったフッ化化合物が含まれる。水洗浄工程３１において、固体物は洗浄槽内で水と混合される。固体物に含まれるフッ化化合物のうち、水溶性の化合物は水に溶解し、フッ化物イオンが水中に移行する。固体物に含まれるＰｕＦ４及びフッ化されなかったウラン酸化物は、水に不溶のため沈殿物として回収する。水洗浄後の固体物は、溶媒抽出工程６に送られて再処理される。 As a method for removing fluoride ions, a case where a method of applying water vapor and a method of applying water are combined will be described with reference to FIG. After the spent nuclear fuel 1 is decoated and powdered, in the fluorination step 2, fluorine gas is supplied as the fluorinating agent 3 in the fluorination reaction layer, and the spent nuclear fuel is fluorinated. Most U contained in the spent nuclear fuel is volatilized as UF 6 , and the volatilized UF 6 is refined in the U refining process and recovered as UF 6 . On the other hand, the solid matter that has not been volatilized in the fluorination step is reacted with the water vapor 22 in a reactor maintained at a high temperature of about 600 ° C. in the oxide conversion step 21. According to the chemical reaction formula (2), the fluorinated compound is converted into an oxide, and HF is generated as a reaction product. HF is removed from the reactor as a gas. As the reaction furnace, for example, a rotary kiln can be adopted. The steam-treated solid material is then sent to the water washing step 31. The solid material after the steam treatment includes a fluorinated compound that has not been converted to oxide by steam. In the water washing step 31, the solid material is mixed with water in the washing tank. Of the fluorinated compounds contained in the solid material, water-soluble compounds dissolve in water, and fluoride ions migrate into water. PuF 4 and unfluorinated uranium oxide contained in the solid matter are recovered as precipitates because they are insoluble in water. The solid after the water washing is sent to the solvent extraction step 6 to be reprocessed.

本実施例によれば、酸化転換工程で予めフッ化物イオンを除去し、かつ、酸化物転換工程で酸化転換されずに残っているフッ化物を水洗浄工程でさらにフッ化物イオンとして除去できる。酸化物転換工程及び水洗浄工程を組み合わせることにより、フッ化物イオンの除去を効率的に行うことが可能である。これにより、溶媒抽出工程において水溶液中でのフッ化物イオンの濃度が極めて低く抑えられ、Ｐｕフッ化物が沈殿するのを防ぎ、Ｐｕの抽出効率を向上させることができる。また、溶媒抽出工程において、水溶液中でのフッ化物イオンの濃度が低く抑えられることで、溶媒抽出工程での材料の腐食を防ぐことができる。さらに、予め水溶性フッ化物である核分裂生成物を除去することができ、後段の湿式工程での核分裂生成物除去の負荷を低減することができる。   According to this embodiment, fluoride ions can be removed in advance in the oxidation conversion step, and fluoride remaining without being subjected to oxidation conversion in the oxide conversion step can be further removed as fluoride ions in the water washing step. By combining the oxide conversion step and the water washing step, it is possible to efficiently remove fluoride ions. As a result, the concentration of fluoride ions in the aqueous solution in the solvent extraction step can be kept extremely low, so that precipitation of Pu fluoride can be prevented, and Pu extraction efficiency can be improved. Further, in the solvent extraction step, the concentration of fluoride ions in the aqueous solution can be kept low, so that corrosion of the material in the solvent extraction step can be prevented. Furthermore, fission products that are water-soluble fluorides can be removed in advance, and the load of fission product removal in the subsequent wet process can be reduced.

本発明による再処理方法の基本的な工程図である。It is a basic process diagram of the reprocessing method according to the present invention. フッ化物イオン除去方法として水蒸気を作用させる場合の工程図である。It is process drawing in the case of making water vapor | steam act as a fluoride ion removal method. フッ化物イオン除去方法として水を作用させる場合の工程図である。It is process drawing in the case of making water act as a fluoride ion removal method. フッ化物イオン除去方法として水蒸気と水を作用させる場合の工程図である。It is process drawing in the case of making water vapor and water act as a fluoride ion removal method.

符号の説明Explanation of symbols

１…使用済み核燃料、２…フッ化工程、３…フッ化剤、５…フッ化物イオン除去工程、６…溶媒抽出工程、２１…酸化物転換工程、２２…水蒸気、３１…水洗浄工程、３２…水。   DESCRIPTION OF SYMBOLS 1 ... Used nuclear fuel, 2 ... Fluorination process, 3 ... Fluorinating agent, 5 ... Fluoride ion removal process, 6 ... Solvent extraction process, 21 ... Oxide conversion process, 22 ... Water vapor, 31 ... Water washing process, 32 …water.

Claims (4)

使用済核燃料にフッ素またはフッ素化合物を作用させてウランの一部分あるいは大部分をフッ化物に転換して揮発除去するフッ化工程と、その後、残ったウラン、プルトニウム、その他の固体物を酸性水溶液に溶解し、溶媒抽出法により処理する溶媒抽出工程とを含む使用済み核燃料の再処理方法において、前記固体物を酸性水溶液に溶解する前段階でフッ化物イオンを除去するフッ化物イオン除去工程を設けたことを特徴とする使用済み核燃料の再処理方法。   A fluorination process in which fluorine or a fluorine compound is allowed to act on spent nuclear fuel to convert a part or most of uranium to fluoride to remove it by volatilization, and then the remaining uranium, plutonium and other solid substances are dissolved in an acidic aqueous solution. In addition, a method for reprocessing spent nuclear fuel including a solvent extraction process for processing by a solvent extraction method is provided with a fluoride ion removal process for removing fluoride ions at a stage before the solid material is dissolved in an acidic aqueous solution. A method for reprocessing spent nuclear fuel characterized by 請求項１において、前記フッ化物イオン除去工程で、前記固体物の中に含まれるフッ化物に水蒸気を作用させることによりフッ化物を酸化物に転換し、フッ化物イオンをフッ化水素として除去することを特徴とする使用済み核燃料の再処理方法。   2. The fluoride ion removal step according to claim 1, wherein in the fluoride ion removal step, the fluoride contained in the solid substance is converted into an oxide by allowing water vapor to act on the fluoride, and the fluoride ion is removed as hydrogen fluoride. A method for reprocessing spent nuclear fuel characterized by 請求項１において、前記フッ化物イオン除去工程で、前記固体物に水を作用させることにより固体物に含まれるフッ化物を溶解し、水溶液中にフッ化物イオンを移行させて除去することを特徴とする使用済み核燃料の再処理方法。   2. The fluoride ion removing step according to claim 1, wherein the fluoride ion contained in the solid material is dissolved by causing water to act on the solid material, and the fluoride ions are transferred to the aqueous solution to be removed. To reprocess spent nuclear fuel. 請求項１において、前記フッ化物イオン除去工程で、まず前記固体物の中に含まれるフッ化物に水蒸気を作用させることによりフッ化物を酸化物に転換して、フッ化物イオンをフッ化水素として除去し、次いで、固体物に水を作用させることにより固体物に含まれるフッ化物を溶解し、水溶液中にフッ化物イオンを移行させて除去することを特徴とする使用済み核燃料の再処理方法。   2. The fluoride ion removal process according to claim 1, wherein in the fluoride ion removal step, the fluoride is first converted into an oxide by causing water vapor to act on the fluoride contained in the solid material to remove fluoride ions as hydrogen fluoride. Then, the spent nuclear fuel is reprocessed by dissolving the fluoride contained in the solid material by causing water to act on the solid material, and transferring and removing the fluoride ions in the aqueous solution.
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