JP6133077B2 - Decontamination method for radioactive contaminants - Google Patents
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- 238000005202 decontamination Methods 0.000 title claims description 42
- 230000002285 radioactive effect Effects 0.000 title claims description 34
- 239000000356 contaminant Substances 0.000 title claims description 30
- 238000004140 cleaning Methods 0.000 claims description 136
- 239000007788 liquid Substances 0.000 claims description 124
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 84
- 238000005406 washing Methods 0.000 claims description 56
- 239000000941 radioactive substance Substances 0.000 claims description 49
- 239000000243 solution Substances 0.000 claims description 43
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 35
- 238000000034 method Methods 0.000 claims description 31
- 238000003756 stirring Methods 0.000 claims description 28
- 239000013078 crystal Substances 0.000 claims description 22
- 239000003463 adsorbent Substances 0.000 claims description 21
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 claims description 19
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims description 19
- 239000012670 alkaline solution Substances 0.000 claims description 18
- 239000012857 radioactive material Substances 0.000 claims description 18
- 239000000920 calcium hydroxide Substances 0.000 claims description 16
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims description 16
- QORWJWZARLRLPR-UHFFFAOYSA-H tricalcium bis(phosphate) Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O QORWJWZARLRLPR-UHFFFAOYSA-H 0.000 claims description 16
- 239000001506 calcium phosphate Substances 0.000 claims description 14
- 229910000389 calcium phosphate Inorganic materials 0.000 claims description 14
- 235000011010 calcium phosphates Nutrition 0.000 claims description 14
- 238000000605 extraction Methods 0.000 claims description 14
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 8
- 230000001747 exhibiting effect Effects 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 6
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 4
- 239000011259 mixed solution Substances 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- 238000011109 contamination Methods 0.000 claims description 3
- ANBBXQWFNXMHLD-UHFFFAOYSA-N aluminum;sodium;oxygen(2-) Chemical compound [O-2].[O-2].[Na+].[Al+3] ANBBXQWFNXMHLD-UHFFFAOYSA-N 0.000 claims description 2
- 229910001388 sodium aluminate Inorganic materials 0.000 claims description 2
- 239000003513 alkali Substances 0.000 description 34
- 230000003588 decontaminative effect Effects 0.000 description 24
- 230000005855 radiation Effects 0.000 description 9
- 238000000926 separation method Methods 0.000 description 9
- 239000012528 membrane Substances 0.000 description 8
- 239000000126 substance Substances 0.000 description 8
- 229910052792 caesium Inorganic materials 0.000 description 7
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 7
- 238000002474 experimental method Methods 0.000 description 7
- 239000000463 material Substances 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- -1 and at the same time Substances 0.000 description 5
- 230000018044 dehydration Effects 0.000 description 5
- 238000006297 dehydration reaction Methods 0.000 description 5
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 239000002689 soil Substances 0.000 description 5
- 229910021536 Zeolite Inorganic materials 0.000 description 4
- 239000004568 cement Substances 0.000 description 4
- 238000010907 mechanical stirring Methods 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 239000010457 zeolite Substances 0.000 description 4
- 239000004743 Polypropylene Substances 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 229920001155 polypropylene Polymers 0.000 description 3
- 230000008929 regeneration Effects 0.000 description 3
- 238000011069 regeneration method Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000003337 fertilizer Substances 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000010865 sewage Substances 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000003828 vacuum filtration Methods 0.000 description 2
- IRPGOXJVTQTAAN-UHFFFAOYSA-N 2,2,3,3,3-pentafluoropropanal Chemical compound FC(F)(F)C(F)(F)C=O IRPGOXJVTQTAAN-UHFFFAOYSA-N 0.000 description 1
- KLZUFWVZNOTSEM-UHFFFAOYSA-K Aluminum fluoride Inorganic materials F[Al](F)F KLZUFWVZNOTSEM-UHFFFAOYSA-K 0.000 description 1
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 229910000323 aluminium silicate Inorganic materials 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 239000008394 flocculating agent Substances 0.000 description 1
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 238000012432 intermediate storage Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 239000002901 radioactive waste Substances 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000001172 regenerating effect Effects 0.000 description 1
- 239000010801 sewage sludge Substances 0.000 description 1
- 239000010802 sludge Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
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Description
本発明は、放射性汚染物の除染方法に関し、特に放射性セシウム等で汚染された下水汚泥焼却灰、汚染土壌等の除染に有効な技術に関する。 The present invention relates to a method for decontaminating radioactive contaminants, and more particularly to a technique effective for decontamination of sewage sludge incineration ash, contaminated soil, etc. contaminated with radioactive cesium or the like.
原発事故発生以来、その放射性物質で汚染された地区からは除染作業により多量の汚染土壌が排出され続けている。また、放射性物質で汚染された雨水等が下水に流れ込み、各地の下水処理場では、放射性物質により汚染された焼却灰の処理に苦慮しているところである。 Since the nuclear accident, a large amount of contaminated soil has been discharged from the area contaminated with radioactive materials by decontamination work. In addition, rainwater contaminated with radioactive material flows into sewage, and various sewage treatment plants are struggling to dispose of incinerated ash contaminated with radioactive material.
また、一方で、これら放射性汚染物の再利用が注目されている。すなわち、放射性汚染物から放射性物質を取り除くことで放射性汚染物の低線量化を図り、汚染焼却灰においては、セメントの原料や化学肥料などへの転用を図ることで、その有効活用と放射性廃棄物の排出量軽減を目指している。 On the other hand, the reuse of these radioactive contaminants has attracted attention. In other words, the radioactive contaminants are removed from the radioactive contaminants to reduce the dose of the radioactive contaminants, and the contaminated incineration ash can be effectively used and radioactive waste by diverting it to cement raw materials and chemical fertilizers. Aims to reduce emissions.
この種の技術は、例えば、焼却灰中にアルカリと石灰を混ぜ入れてリン酸カルシウムを回収する技術（特許文献１）等に代表されるリサイクル技術を応用して確立されるものであるが、これらの多くは、放射性物質の付着を、問題として未だ適用できずにいる。 This type of technology is established, for example, by applying a recycling technology represented by a technology (Patent Document 1) that recovers calcium phosphate by mixing alkali and lime into incinerated ash. Many have yet to apply radioactive material deposition as a problem.
すなわち、汚染焼却灰や汚染土壌に含まれるセシウム等の放射性物質は、これら放射性汚染物に含まれるアルミノシリケート等の鉱物質に強く吸着されて容易に分離できないため、汚染焼却灰や汚染土壌を再利用する際には、有価物の回収に先立ち、放射性汚染物に強く吸着した放射性物質を取り除く必要がある。 In other words, radioactive materials such as cesium contained in contaminated incineration ash and contaminated soil are strongly adsorbed by minerals such as aluminosilicate contained in these radioactive contaminants and cannot be easily separated. When using it, it is necessary to remove the radioactive material strongly adsorbed to the radioactive contaminants prior to the collection of valuable materials.
本発明は、上記した技術的課題を解決するためになされたもので、放射性汚染物に含まれる放射性物質を容易に、また、経済的に除去できる除染技術の提供を課題とする。 The present invention has been made to solve the above-described technical problems, and an object of the present invention is to provide a decontamination technique that can easily and economically remove radioactive substances contained in radioactive contaminants.
本発明は、放射性物質に汚染された放射性汚染物の除染方法であって、
前記放射性汚染物とアルカリ性を示す洗浄液とを混合し、その混合液を加温下で撹拌洗浄して前記放射性物質を洗浄処理液中に溶出させて抽出する工程と、
吸着剤を用いて前記洗浄処理液中に溶出した放射性物質を除去する工程と、
前記放射性物質が除去された洗浄処理液に、水酸化カルシウム若しくは水酸
化アルミ結晶のうちの何れか一方、又は両方を加えることで、前記洗浄処理液
中に、前記放射性物質を含む洗浄処理液を抽出する工程で用いるアルカリ溶液
を再合成した再合成洗浄液を得る工程と、
を有することを特徴とする。
The present invention is a decontamination method for radioactive contaminants contaminated with radioactive substances,
A step of mixing the radioactive contaminants and a cleaning solution showing alkalinity, stirring and washing the mixed solution under heating, and eluting and extracting the radioactive substance in a cleaning treatment solution;
Removing radioactive material eluted in the cleaning solution using an adsorbent;
In the cleaning treatment liquid from which the radioactive substance has been removed, calcium hydroxide or hydroxide
By adding either one or both of aluminum fluoride crystals, the cleaning treatment liquid
Alkaline solution used in the process of extracting the cleaning treatment liquid containing the radioactive substance
A step of obtaining a re-synthesizing cleaning solution re-synthesized
It is characterized by having.
この方法によれば、放射性汚染物と洗浄液とを混合し、加温下で撹拌洗浄して放射性物質を含む洗浄処理液を抽出する。また、放射性物質の吸着剤を用いて洗浄処理液中の放射性物質を吸着剤に吸着させて除去する。すなわち、放射性汚染物に対して強固に吸着している放射性物質を洗浄液中に一度溶かし出し、後に吸着剤を用いてこの放射性物質を選択的に除去する。
このように本除染方法は、洗浄液を用いて放射性物質を洗浄液中に溶かし出す簡単な作業で、その放射性物質の選択的除去を可能にしたものである。
According to this method, the radioactive contaminant and the cleaning liquid are mixed, and the cleaning treatment liquid containing the radioactive substance is extracted by stirring and cleaning under heating. Further, the radioactive substance in the cleaning liquid is adsorbed and removed by using the radioactive substance adsorbent. That is, a radioactive substance that is firmly adsorbed to radioactive contaminants is once dissolved in a cleaning solution, and this radioactive substance is selectively removed later using an adsorbent.
As described above, the present decontamination method enables the selective removal of the radioactive substance by a simple operation of dissolving the radioactive substance in the cleaning liquid using the cleaning liquid.
なお、本除染方法が適用できる放射線汚染物としては、汚泥焼却灰、汚染土壌等の粒状物質を好適に例示できる。また、放射性物質としては、放射性セシウムに対して特に有用である。 In addition, as a radioactive pollutant to which this decontamination method can be applied, granular substances, such as sludge incineration ash and contaminated soil, can be illustrated suitably. Moreover, as a radioactive substance, it is especially useful with respect to radioactive cesium.
また、前記アルカリ性を示す洗浄液は、その主成分として水酸化ナトリウム、及び水酸化カリウムの何れか、又はその両方をアルカリ溶液として含むとよい。
すなわち、水酸化ナトリウム、及び水酸化カリウムから選ばれた少なくとも１種を添加することで、放射性汚染物の洗浄に適したアルカリ性を示す洗浄液が得られる。
In addition, the alkaline cleaning liquid may contain sodium hydroxide and / or potassium hydroxide as the main component, or both as an alkaline solution.
That is, by adding at least one selected from sodium hydroxide and potassium hydroxide, a cleaning liquid exhibiting alkalinity suitable for cleaning radioactive contaminants can be obtained.
また、前記吸着剤としては、例えばゼオライト、フェロシアン化合物等を用いることができる。 Moreover, as said adsorbent, a zeolite, a ferrocyan compound, etc. can be used, for example.
また、前記放射性物質が除去された洗浄処理液に、水酸化カルシウム若しくは水酸化アルミ結晶のうちの何れか一方、又は両方を加えることで、前記洗浄処理液中に次のサイクルに使用可能なアルカリ溶液を再合成して、再合成洗浄液を得る工程と、
前記再合成洗浄液に、新規アルカリを加えて前記アルカリ性を示す洗浄液として再利用する工程と、を更に付加してもよい。
Further, by adding one or both of calcium hydroxide and aluminum hydroxide crystals to the cleaning treatment liquid from which the radioactive substance has been removed, an alkali that can be used in the next cycle in the cleaning treatment liquid. Re-synthesizing the solution to obtain a re-synthetic washing solution;
A step of adding a new alkali to the re-synthesizing cleaning liquid and reusing it as a cleaning liquid exhibiting the alkalinity may be further added.
すなわち、洗浄処理液中に水酸化カルシウム及び水酸化アルミ結晶のいずれか一方、又はこれらの両方を加えることで、アルカリを洗浄処理液中に再合成し、この再合成されたアルカリを再利用して、さらなる放射性汚染物の除染洗浄に用いる。
この方法によれば、放射線汚染物の撹拌洗浄に用いるアルカリ性を示す洗浄水を再利用することができ、また、新規アルカリ溶液の追加も少なくて済むため経済的である。また、除染によって排出される洗浄処理液の排出量も減らせる。
That is, by adding one or both of calcium hydroxide and aluminum hydroxide crystals to the cleaning treatment solution, the alkali is re-synthesized in the cleaning treatment solution, and the re-synthesized alkali is reused. For further decontamination and cleaning of radioactive contaminants.
According to this method, cleaning water showing alkalinity used for stirring cleaning of radiation contaminants can be reused, and it is economical because the addition of a new alkaline solution can be reduced. In addition, the amount of cleaning liquid discharged by decontamination can be reduced.
また、前記洗浄処理液を用いて抽出する工程が、複数回にわたり繰り返されるようにしてもよい。この方法によれば、洗浄処理液中に放射性物質が濃縮されるため、本工程における放射性物質の抽出率を高めることができる。 Moreover, you may make it repeat the process extracted using the said washing | cleaning process liquid over multiple times. According to this method, since the radioactive substance is concentrated in the cleaning treatment liquid, the extraction ratio of the radioactive substance in this step can be increased.
また、前記再生洗浄液を、アルカリ性を示す洗浄液として再利用する工程では、その都度、前記再合成洗浄液のアルカリ濃度を、前回使用時のアルカリ濃度と同等となるように調整して再利用することが望ましい。しかし、状況に応じて、前回使用時のアルカリ濃度よりも低いか、又は、高い濃度で使用してもよい。
さらに、上記再合成洗浄液のアルカリ濃度を、容易に前回処理時と同等程度にすることができるので、より効率的な除染をすることが可能である。
Further, in the step of reusing the regenerated cleaning liquid as a cleaning liquid exhibiting alkalinity, the alkali concentration of the re-synthetic cleaning liquid may be adjusted and reused so as to be equal to the alkali concentration at the previous use each time. desirable. However, it may be used at a concentration lower or higher than the alkali concentration at the previous use depending on the situation.
Furthermore, since the alkali concentration of the re-synthesizing washing liquid can be easily made comparable to that at the previous treatment, more efficient decontamination can be performed.
この方法では、放射性物質の抽出率を高めるために必要なアルカリを、最小量で満たすことができる。すなわち、アルカリ濃度を保持し、又は、これを徐々に回復していくことが容易であるため、確実な抽出率を確保することができる。よって、除染に用いるアルカリの総量を減らすことができる。 In this method, the alkali necessary for increasing the extraction rate of the radioactive substance can be filled with a minimum amount. That is, since it is easy to maintain the alkali concentration or to gradually recover the alkali concentration, it is possible to ensure a reliable extraction rate. Therefore, the total amount of alkali used for decontamination can be reduced.
また、前記再生洗浄液を得る工程では、前記水酸化カルシウムを前記洗浄処理液に添加し、この水酸化カルシウムの添加によって前記洗浄処理液中のリン酸をリン酸カルシウムの結晶体とすると共に、その結晶化したリン酸カルシウムを前記洗浄処理液から固液分離して水酸化ナトリウムを再合成し、この再合成された水酸化ナトリウムを、前記アルカリ溶液として再利用するとよい。 Further, in the step of obtaining the regenerated cleaning liquid, the calcium hydroxide is added to the cleaning processing liquid, and the phosphoric acid in the cleaning processing liquid is converted into a calcium phosphate crystal by the addition of the calcium hydroxide, and the crystallization thereof is performed. The calcium phosphate that has been subjected to solid-liquid separation from the washing treatment solution is used to re-synthesize sodium hydroxide, and the re-synthesized sodium hydroxide may be reused as the alkaline solution.
この方法では、放射線汚染物中の有価物としてリン酸カルシウムを回収できると同時に、アルカリ溶液の再合成に用いる洗浄用の水酸化ナトリウムも得られる。 In this method, calcium phosphate can be recovered as a valuable material in radiation contaminants, and at the same time, sodium hydroxide for washing used for resynthesis of an alkaline solution can be obtained.
また、前記再合成洗浄液を得る工程では、前記洗浄処理液に前記水酸化アルミ結晶を種晶として加えると共に、この種晶によって前記洗浄処理液中の溶解状アルミン酸ソーダから水酸化アルミニウムを結晶化させて水酸化ナトリウムを再合成し、この再合成された水酸化ナトリウムを、前記アルカリ溶液として再利用してもよい。 In the step of obtaining the re-synthesizing cleaning solution, the aluminum hydroxide crystal is added as a seed crystal to the cleaning processing solution, and aluminum hydroxide is crystallized from the dissolved sodium aluminate in the cleaning processing solution by the seed crystal. Then, sodium hydroxide may be re-synthesized, and the re-synthesized sodium hydroxide may be reused as the alkaline solution.
この方法では、放射線汚染物中の有価物として水酸化アルミニウムを回収できると同時に、アルカリ溶液の再生に用いる水酸化ナトリウムも得られる。 In this method, aluminum hydroxide can be recovered as a valuable material in radiation contaminants, and at the same time, sodium hydroxide used for regeneration of an alkaline solution can be obtained.
また、前記各工程を経る毎に固液分離処理を行ってもよい。すなわち、工程毎に固液分離処理を行うことで、後の工程の処理が容易になる他、各工程で得られる洗浄処理液、再生処理液の容量を減らすことができる。 Moreover, you may perform a solid-liquid separation process whenever it passes through each said process. That is, by performing the solid-liquid separation process for each process, the process of the subsequent process is facilitated, and the capacity of the cleaning process liquid and the regeneration process liquid obtained in each process can be reduced.
また、前記水酸化カルシウムの添加によるアルカリ溶液の再合成の後に、前記水酸化アルミ結晶によるアルカリ溶液の再合成処理を実施するとよい。 Further, after the resynthesis of the alkaline solution by the addition of calcium hydroxide, a resynthesis process of the alkaline solution with the aluminum hydroxide crystals may be performed.
このように水酸化カルシウムを、水酸化アルミ結晶に先立ち添加すれば、洗浄処理液中に多量に含まれている放射線汚染物から抽出されたリン酸を効率良く回収できる。 Thus, if calcium hydroxide is added prior to the aluminum hydroxide crystal, phosphoric acid extracted from radiation contaminants contained in a large amount in the cleaning solution can be efficiently recovered.
また、前記洗浄液による抽出操作では、撹拌洗浄時の温度を２０〜１２０℃の範囲に保持することが好ましい。さらに好ましくは３０℃〜９５℃の範囲とするのがよい。このように、撹拌洗浄時の温度を管理することで洗浄液の洗浄力を高め、放射性物質の抽出率を高く維持することができる。 In the extraction operation using the cleaning liquid, it is preferable to maintain the temperature during stirring and cleaning in the range of 20 to 120 ° C. More preferably, it is good to set it as the range of 30 to 95 degreeC. Thus, by controlling the temperature at the time of stirring and cleaning, the cleaning power of the cleaning liquid can be increased, and the extraction rate of the radioactive substance can be maintained high.
また、前記洗浄液のアルカリ濃度を０．１〜８Ｍ／Ｌの範囲に設定するのがよい。さらに好ましくは２〜５Ｍ／Ｌの範囲に設定するとよい。このようなアルカリ濃度に設定すれば、アルカリ濃度を不必要に高めずとも、放射性物質を効率良く洗浄液中に溶出せることが可能である。 The alkali concentration of the cleaning liquid is preferably set in the range of 0.1 to 8 M / L. More preferably, it may be set in the range of 2 to 5 M / L. If such an alkali concentration is set, the radioactive substance can be efficiently eluted into the cleaning liquid without unnecessarily increasing the alkali concentration.
以上のように本発明によれば、放射性汚染物に含まれる放射性物質を容易に除去することができ、かつ、アルカリ溶液の再合成により、経済的な処理が可能な除染技術が提供される。
また、放射線汚染物中の有価物としてリン酸カルシウムを回収することができる。
As described above, according to the present invention, there is provided a decontamination technique that can easily remove radioactive substances contained in radioactive contaminants and that can be economically processed by resynthesis of an alkaline solution. .
Moreover, calcium phosphate can be recovered as a valuable material in the radiation contaminant.
以下、放射性セシウム（Ｃｓ１３４，Ｃｓ１３７）で汚染された汚染焼却灰に本発明の除染方法を適用した実施の形態を説明する。 Hereinafter, an embodiment in which the decontamination method of the present invention is applied to contaminated incineration ash contaminated with radioactive cesium (Cs134, Cs137) will be described.
本実施の形態に示す除染方法は、図１に示すように、汚染焼却灰とアルカリ性を示す洗浄液とを混合すると共に、その混合液を加温下で撹拌洗浄して、放射性物質を洗浄処理液に抽出する工程（１０１）と、吸着剤を用いて洗浄処理液中の放射性物質を除去する工程（１０２）と、を経て放射性物質を除染する。 In the decontamination method shown in the present embodiment, as shown in FIG. 1, the contaminated incineration ash and a cleaning liquid showing alkalinity are mixed, and the mixed liquid is stirred and washed under heating to wash the radioactive substance. The radioactive substance is decontaminated through the step (101) of extracting into the liquid and the step (102) of removing the radioactive substance in the cleaning treatment liquid using the adsorbent.
また、放射性物質が除去された洗浄処理液中に水酸化カルシウム及び水酸化アルミ結晶等を加え、その洗浄処理液中にアルカリ溶液を再生させて再生洗浄液を得る工程（１０３）と、再生洗浄液中に新規アルカリを追加補充して洗浄液として再利用する工程（１０４）とを更に含み、このように放射性物質除去後の洗浄処理液（再生洗浄液）を再利用してさらなる放射線汚染物の除染を実施する。 A step (103) of adding calcium hydroxide and aluminum hydroxide crystals to the cleaning treatment liquid from which the radioactive material has been removed to regenerate an alkaline solution in the cleaning treatment liquid to obtain a regenerated cleaning liquid; And a step (104) of replenishing with a new alkali and reusing it as a cleaning solution, and thus reusing the cleaning treatment solution (recycled cleaning solution) after removing the radioactive material to further decontaminate radiation contaminants. carry out.
はじめに、汚染焼却灰とアルカリ性を示す洗浄液とを混合して放射性物質を含む洗浄処理液を抽出する工程（１０１）を説明する。
本工程（１０１）では、平均粒度２０〜３０μｍの焼却灰を対象として、その焼却灰を、アルカリ性を示す洗浄液を用いて撹拌洗浄した後、固液分離処理を施すことによって放射性物質を含む洗浄処理液を得る。
First, the step (101) of mixing the contaminated incineration ash and the cleaning liquid showing alkalinity and extracting the cleaning processing liquid containing the radioactive substance will be described.
In this step (101), for incineration ash having an average particle size of 20 to 30 μm, the incineration ash is agitated and washed with a cleaning solution showing alkalinity, and then subjected to a solid-liquid separation treatment to contain a radioactive substance. Obtain a liquid.
また、洗浄条件を説明すると、アルカリとして水酸化ナトリウム（ＮａＯＨ）あるいは水酸化カリウム（ＫＯＨ）等を溶かし込んだ水溶液を、洗浄液として用いる。また、汚染焼却灰とアルカリ性を示す洗浄液との比率（Ｗ／Ｗ）は、１／３〜１／５０とする。また、アルカリ濃度は、０．１〜８Ｍ／Ｌの範囲、さらに望ましくは２〜５Ｍ／Ｌの範囲とするのがよい。
また、撹拌洗浄時の液温度を２０〜１２０℃（望ましくは３０〜９５℃）に保ち、強力加熱撹拌によって１〜１０ｈ撹拌洗浄することができる。
The cleaning conditions will be described. An aqueous solution in which sodium hydroxide (NaOH) or potassium hydroxide (KOH) is dissolved as an alkali is used as the cleaning liquid. The ratio (W / W) between the contaminated incineration ash and the alkaline cleaning liquid is 1/3 to 1/50. The alkali concentration is preferably in the range of 0.1 to 8 M / L, more preferably in the range of 2 to 5 M / L.
Moreover, the liquid temperature at the time of stirring and washing can be kept at 20 to 120 ° C. (desirably 30 to 95 ° C.), and can be stirred and washed for 1 to 10 hours by vigorous heating and stirring.
なお、上記洗浄条件による撹拌洗浄は、汚染焼却灰に対して複数回にわたり実施する。また、初回の洗浄時には、新規の洗浄液のみならず、後に詳述する再合成洗浄液を利用して洗浄してもよい。また、続く２回目以降の洗浄では、初回の洗浄で得た再合成洗浄液に不足分のアルカリ（新規アルカリ）を追加補充して、その洗浄に用いる。 In addition, the stirring washing | cleaning by the said washing | cleaning conditions is implemented in multiple times with respect to contaminated incineration ash. Further, at the time of the first cleaning, not only a new cleaning solution but also a re-synthesizing cleaning solution described in detail later may be used for cleaning. In the subsequent second and subsequent washings, a short amount of alkali (new alkali) is additionally supplemented to the re-synthesizing washing liquid obtained in the first washing and used for the washing.
また、汚染焼却灰とアルカリ性を示す洗浄液とが混ざり合った混合液は、撹拌洗浄を終えた後に、その都度、遠心分離器またはフィルタープレスなどによって固液分離され、洗浄処理液として抽出される。
洗浄処理液抽出後の残渣（固形物）は、ケーキ洗浄の後に乾燥させてセメントの原料などに用いられる。
Further, the mixed liquid in which the contaminated incineration ash and the alkaline cleaning liquid are mixed is subjected to solid-liquid separation by a centrifuge or a filter press after each stirring and cleaning, and extracted as a cleaning processing liquid.
The residue (solid matter) after the washing treatment liquid extraction is dried after the cake washing and used as a raw material for cement.
続いて、洗浄処理液中の放射性物質を除去する工程（１０２）を説明する。
本工程（１０２）では、吸着剤を用いて洗浄処理液中の放射性物質を除去する。
具体的には、ゼオライト等の多孔質濾材等の他、フェロシアン化鉄及びフェロシアン化ニッケルなどのフェロシアン化合物等を用いて放射性物質を接触分離することができる。また、その接触分離方式は、撹拌槽式や吸着塔式などの既存の方式を例示できる。そして、吸着剤と洗浄処理液とを固液分離処理して、放射性物質を吸着剤と共に洗浄処理液から除去する。
Subsequently, the step (102) of removing radioactive substances in the cleaning treatment liquid will be described.
In this step (102), radioactive material in the cleaning treatment liquid is removed using an adsorbent.
Specifically, the radioactive material can be contact-separated using a porous filter medium such as zeolite or the like, or a ferrocyan compound such as iron ferrocyanide or nickel ferrocyanide. Moreover, the contact separation system can illustrate existing systems, such as a stirring tank type and an adsorption tower type. Then, the adsorbent and the cleaning treatment liquid are subjected to solid-liquid separation, and the radioactive substance is removed from the cleaning treatment liquid together with the adsorbent.
続いて、放射性物質除去済みの洗浄処理液中にアルカリを再生させて再生洗浄液を得る工程（１０３）について説明する。
本工程（１０３）では、上記工程で得た洗浄処理液に水酸化カルシウムあるいは水酸化アルミ結晶を加えて、アルカリの再生をする。
具体的には、下記構造（化１参照）の洗浄処理液中に水酸化カルシウム（Ｃａ（ＯＨ）２）を添加し（化２参照）、この水酸化カルシウムの添加によって洗浄処理液中のリン酸（Ｎａ３ＰＯ４）をリン酸カルシウム（Ｃａ３（ＰＯ４）２）の結晶体とする。また、その結晶化したリン酸カルシウムを洗浄処理液中から固液分離回収して、水酸化ナトリウムを液中に副生させる。
Next, the step (103) of regenerating the alkali in the cleaning treatment liquid from which the radioactive substance has been removed to obtain a regenerated cleaning liquid will be described.
In this step (103), calcium hydroxide or aluminum hydroxide crystal is added to the cleaning solution obtained in the above step to regenerate the alkali.
Specifically, calcium hydroxide (Ca (OH) 2 ) is added to a cleaning treatment liquid having the following structure (see chemical formula 1) (see chemical formula 2 ), and phosphorous in the cleaning treatment liquid is added by the addition of calcium hydroxide. Acid (Na 3 PO 4 ) is a crystalline form of calcium phosphate (Ca 3 (PO 4 ) 2 ). Further, the crystallized calcium phosphate is separated and recovered from the washing treatment liquid, and sodium hydroxide is by-produced in the liquid.
なお、アルカリ溶液の再生前の洗浄処理液中には、化学式１に示すように焼却灰由来のリン酸（Ｎａ３ＰＯ４）が多量に溶解蓄積している。このため本工程では、水酸化アルミ結晶に先立って水酸化カルシウムを添加してリンを固定化し、有価物としてそのリンを回収し、また水酸化ナトリウム（ＮａＯＨ）の再合成を図る。 In addition, a large amount of phosphoric acid (Na 3 PO 4 ) derived from incineration ash is dissolved and accumulated in the cleaning solution before regeneration of the alkaline solution as shown in Chemical Formula 1. Therefore, in this step, calcium hydroxide is added prior to the aluminum hydroxide crystal to fix phosphorus, recover the phosphorus as a valuable material, and re-synthesize sodium hydroxide (NaOH).
また、洗浄処理液中に溶解アルミ（ＮａＡｌＯ２）が多くなった場合には、水酸化アルミ結晶からなる種晶を洗浄処理液にさらに加え、この種晶をもとに得られた溶解状アルミン酸ソーダから水酸化アルミニウムを結晶化させると共に、水酸化ナトリウム（アルカリ）溶液を再合成する。 Further, when the amount of dissolved aluminum (NaAlO 2 ) increases in the cleaning treatment liquid, a seed crystal composed of aluminum hydroxide crystals is further added to the cleaning treatment liquid, and the dissolved aluminium obtained based on this seed crystal. Aluminum hydroxide is crystallized from acid soda and a sodium hydroxide (alkali) solution is re-synthesized.
また、このようにしてアルカリ溶液を再合成した後、洗浄処理液を再度、固液分離処理して水酸化アルミニウムを回収する。また、その残液を再合成処理液として抽出に再利用する。
このように本工程では、水酸化カルシウム及び水酸化アルミ結晶を適時添加してアルカリ溶液を再合成し、併せてリン酸カルシウム等の有価物を洗浄処理液から効率良く回収する。
Moreover, after re-synthesize | combining an alkali solution in this way, a washing process liquid is again solid-liquid-separated and aluminum hydroxide is collect | recovered. Further, the residual liquid is reused for extraction as a resynthesis process liquid.
Thus, in this step, calcium hydroxide and aluminum hydroxide crystals are added at appropriate times to re-synthesize the alkaline solution, and at the same time, valuable materials such as calcium phosphate are efficiently recovered from the cleaning treatment liquid.
そして、本除染方法では、上記工程（１０３）を経て得られた再合成洗浄液を次なる撹拌洗浄作業に再利用する。
なお、本工程（１０４）で再利用する再合成洗浄液は、通常、新規のアルカリ性を示す洗浄液に較べてアルカリ濃度が低いため、再利用の都度、新規のアルカリを追加補充しながら用いる。また、このアルカリを補充する際には、放射性物質の抽出効率を上げるために、前回使用時のアルカリ濃度と同等に、これを高めるようにアルカリを補充することができる。
In this decontamination method, the re-synthetic cleaning liquid obtained through the step (103) is reused for the next stirring and cleaning operation.
The re-synthesizing cleaning solution reused in this step (104) usually has a lower alkali concentration than the cleaning solution exhibiting a new alkalinity, so that it is used while replenishing a new alkali every time it is reused. Further, when replenishing this alkali, in order to increase the extraction efficiency of the radioactive substance, it is possible to replenish the alkali so as to increase the same as the alkali concentration at the previous use.
このように本除染方法によれば、放射性汚染物とアルカリ性を示す洗浄液とを混合し、加温下で撹拌洗浄して放射性物質を含む洗浄処理液を抽出する。また、放射性物質の吸着剤を用いて、洗浄処理液中の放射性物質を吸着させて除去する。つまり、放射性汚染物に対して強固に吸着している放射性物質を、アルカリ性を示す洗浄液中に溶出させるという簡単な作業で、吸着剤による放射性物質の選択的除去を可能にした。 As described above, according to the present decontamination method, the radioactive contaminants and the cleaning liquid exhibiting alkalinity are mixed, and the cleaning treatment liquid containing the radioactive substance is extracted by stirring and cleaning under heating. Further, the radioactive substance in the cleaning treatment liquid is adsorbed and removed using a radioactive substance adsorbent. That is, it is possible to selectively remove the radioactive substance by the adsorbent by a simple operation of eluting the radioactive substance that is firmly adsorbed to the radioactive contaminants into the alkaline cleaning liquid.
また、洗浄処理液中に水酸化カルシウム及び水酸化アルミ結晶から選ばれる少なくとも１種を加えることで、アルカリを洗浄処理液中に再生させ、この再生されたアルカリを再利用して、さらなる放射性汚染物の除染洗浄作業を行えるようにした。 Further, by adding at least one selected from calcium hydroxide and aluminum hydroxide crystals to the cleaning treatment liquid, the alkali is regenerated in the cleaning treatment liquid, and the regenerated alkali is reused to further reduce radioactive contamination. The decontamination washing work of the thing was enabled.
なお、上記の実施の形態では、前記洗浄液として水酸化ナトリウム（ＮａＯＨ）の水溶液を用いたが、水酸化ナトリウムに代えて水酸化カリウム（ＫＯＨ）を用いた場合にも、上記とほぼ同様のメカニズムで除染と洗浄処理液の再生、並びに有価物の回収を行える（化学式３、化学式４参照）。 In the above-described embodiment, an aqueous solution of sodium hydroxide (NaOH) is used as the cleaning liquid. However, when potassium hydroxide (KOH) is used instead of sodium hydroxide, the same mechanism as described above is used. Can decontaminate, regenerate the cleaning solution, and recover valuable materials (see Chemical Formula 3 and Chemical Formula 4).
すなわち、上記化学式から明らかな様に水酸化カリウム（ＫＯＨ）を洗浄液に用いた場合には、アルカリ溶液として水酸化カリウム溶液が再合成される。また、有価物として焼却灰由来のリン酸カルシウム（Ｃａ３（ＰＯ４）２）が得られる。
このように本実施の形態では、水酸化ナトリウム及び水酸化カリウムの何れか、又はこれらの両方を含む水溶液をアルカリ性を示す洗浄液として用いている。
That is, as apparent from the above chemical formula, when potassium hydroxide (KOH) is used for the cleaning liquid, the potassium hydroxide solution is re-synthesized as an alkaline solution. In addition, calcium phosphate (Ca 3 (PO 4 ) 2 ) derived from incinerated ash is obtained as a valuable resource.
As described above, in the present embodiment, an aqueous solution containing either or both of sodium hydroxide and potassium hydroxide is used as a cleaning liquid exhibiting alkalinity.
続いて、本除染方法に基づいて実施した除染実験の結果を示す。 Then, the result of the decontamination experiment implemented based on this decontamination method is shown.
＜実施例１＞
除染実験に先立ち、本実験で用いるアルカリ性を示す洗浄液を得るために予備抽出を行う。予備抽出は下記手順で行われる。
はじめに放射性セシウムに汚染された汚染焼却灰５０ｇ（水分量３４％）と、アルカリ性を示す洗浄液５００ｍＬ（ＮａＯＨ液 ２Ｍ／Ｌ）とを１リットルのポリプロピレン容器内に入れて混合する。続いて、その混合液を、ウォーターバスを用いて８０℃で保温しながら強力機械撹拌によって６時間撹拌する。また、撹拌後の混合液を１μｍのメンブレンフィルターによって真空濾過し、濾液は、続く除染実験に用いるための洗浄液として使用する。
<Example 1>
Prior to the decontamination experiment, pre-extraction is performed to obtain an alkaline cleaning solution used in this experiment. Pre-extraction is performed according to the following procedure.
First, 50 g of contaminated incineration ash contaminated with radioactive cesium (water content 34%) and 500 mL of alkaline cleaning solution (NaOH solution 2 M / L) are placed in a 1 liter polypropylene container and mixed. Subsequently, the mixture is stirred for 6 hours by vigorous mechanical stirring while being kept at 80 ° C. using a water bath. Further, the mixed liquid after stirring is vacuum filtered through a 1 μm membrane filter, and the filtrate is used as a washing liquid for use in subsequent decontamination experiments.
１回目の除染洗浄は下記手順で行われる。１回目の除染洗浄では、上記同様、放射性セシウムに汚染された汚染焼却灰５０ｇ（水分量３４％）を新規に用意すると共に、この汚染焼却灰と、予備抽出で得られた洗浄液５００ｍＬとを１リットルのポリプロピレン容器に入れて混合する。続いて、その混合液を、ウォーターバスを用いて８０℃で保温しながら、攪拌羽を用いた強力機械撹拌によって、６時間、撹拌洗浄する。また、撹拌洗浄後の混合液を、孔径が１μｍのメンブレンフィルターによって真空濾過し、放射性物質を含んだ洗浄処理液を得て、残渣は、ケーキ洗浄・脱水の上、その線量を測定しておく。 The first decontamination cleaning is performed according to the following procedure. In the first decontamination cleaning, as described above, 50 g of contaminated incineration ash contaminated with radioactive cesium (water content 34%) is newly prepared, and this contaminated incineration ash and 500 mL of the cleaning liquid obtained by the preliminary extraction are prepared. Place in a 1 liter polypropylene container and mix. Subsequently, the mixed solution is stirred and washed for 6 hours by vigorous mechanical stirring using stirring blades while being kept at 80 ° C. using a water bath. Moreover, the mixed liquid after stirring and washing is vacuum filtered through a membrane filter having a pore size of 1 μm to obtain a washing treatment liquid containing a radioactive substance, and the residue is subjected to cake washing and dehydration, and the dose is measured in advance. .
続いて、この洗浄処理液から吸着剤を用いて放射性物質を除去する。
本作業では、容量１リットルの撹拌槽に洗浄処理液５００ｍＬと、吸着剤として０，８２ｇのゼオライトとを入れ、１時間撹拌して放射性物質を吸着剤に吸着させる。また、撹拌後の洗浄処理液を１μｍのメンブレンフィルターによって真空濾過して、放射性物質を洗浄処理液中から吸着剤と共に除去する。
Subsequently, the radioactive material is removed from the cleaning treatment liquid using an adsorbent.
In this operation, 500 mL of the cleaning treatment liquid and 0.82 g of zeolite as an adsorbent are placed in a 1 liter stirring tank, and the radioactive material is adsorbed on the adsorbent by stirring for 1 hour. Further, the washing treatment liquid after stirring is vacuum filtered through a 1 μm membrane filter, and the radioactive substance is removed from the washing treatment liquid together with the adsorbent.
続いて、このようにして得られた放射性物質除去済みの洗浄処理液を再生する。
本作業では、容量１リットルの撹拌槽に放射性物質除去済みの洗浄処理液に水酸化カルシウム（Ｃａ（ＯＨ）２）を１３ｇ添加して３時間撹拌し、その洗浄処理液中にアルカリ（ＮａＯＨ）溶液を再合成する。また、撹拌後の洗浄処理液を孔径が１μｍのメンブレンフィルターによって真空濾過して、リン酸カルシウムを洗浄処理液中から回収すると共に、その残液を再生洗浄液として抽出する。また、残渣は、ケーキ洗浄・脱水の上、その線量を測定する。
Subsequently, the cleaning liquid obtained after removing the radioactive material is regenerated.
In this work, 13 g of calcium hydroxide (Ca (OH) 2 ) was added to a cleaning treatment solution having a radioactive substance removed in a stirring tank having a capacity of 1 liter, and the mixture was stirred for 3 hours. Re-synthesize the solution. Further, the washing treatment liquid after stirring is vacuum filtered through a membrane filter having a pore size of 1 μm to collect calcium phosphate from the washing treatment liquid, and the remaining liquid is extracted as a regenerated washing liquid. In addition, the dose of the residue is measured after washing and dewatering the cake.
続いて、上記作業で得られた再生洗浄液を用いて２回目の撹拌洗浄を実施する。
本作業では、１回目の洗浄を終えた焼却灰を再び同様の手順にて再洗浄する。２回目の洗浄では、その洗浄に用いる洗浄液として、上記工程で得られた再合成洗浄液に、水酸化ナトリウムを１０ｇ補給して、すなわち、新規アルカリを補充し、アルカリ濃度を１回目の除染洗浄時と同程度とした後、強力機械撹拌によって６時間、再洗浄する。
Subsequently, a second stirring and cleaning is performed using the regenerated cleaning liquid obtained in the above operation.
In this work, the incinerated ash after the first washing is washed again in the same procedure. In the second washing, 10 g of sodium hydroxide is replenished to the re-synthetic washing liquid obtained in the above step as the washing liquid used for the washing, that is, a new alkali is replenished, and the alkali concentration is set to the first decontamination washing. After about the same time, rewash for 6 hours with strong mechanical agitation.
そして、再洗浄を終えた汚染焼却灰を、孔径が１μｍのメンブレンフィルターを用いて真空濾過する。また、この真空濾過によって固液分離された残渣をケーキ洗浄・脱水の上、その線量を測定した。 Then, the contaminated incineration ash that has been rewashed is vacuum filtered using a membrane filter having a pore diameter of 1 μm. In addition, the residue separated by solid-liquid separation by vacuum filtration was subjected to cake washing and dehydration, and the dose was measured.
以上の工程を経て得られた残灰の除染結果を表１に示す。 Table 1 shows the decontamination results of the residual ash obtained through the above steps.
表１から明らかなように、本除染方法で除染した場合、その残灰（残渣）の重量は、リン酸カルシウム等の回収分を差し引いて考えれば、洗浄前と洗浄後で殆ど変化しておらず、しかも、その放射線量は、２回目の洗浄を終えた時点で約１／５迄低下している。
すなわち、セメント原料等に利用可能な残灰を減らすこと無く、大幅な除染に成功したことがわかる。
As is apparent from Table 1, when decontamination is performed by the present decontamination method, the weight of the residual ash (residue) hardly changes after washing and after washing, considering the recovered amount of calcium phosphate and the like. In addition, the radiation dose is reduced to about 1/5 when the second cleaning is completed.
That is, it can be seen that the decontamination succeeded without reducing the residual ash that can be used for cement raw materials.
＜実施例２＞
続いて、水酸化ナトリウム（ＮａＯＨ）に代えて、水酸化カリウム（ＫＯＨ）を洗浄液の主成分として用いた除染結果を本実施例２で説明する。
<Example 2>
Subsequently, a decontamination result using potassium hydroxide (KOH) as a main component of the cleaning liquid instead of sodium hydroxide (NaOH) will be described in the second embodiment.
本実施例２も実施例１と同様に、その除染実験に先立ち、本実験で用いる洗浄液を得るために予備抽出を行う。予備抽出は下記手順で行われる。
はじめに放射性セシウムに汚染された汚染焼却灰５０ｇ（水分量３０％）と、洗浄液５００ｍＬ（ＫＯＨ液 ５Ｍ／Ｌ）とを１リットルポリプロピレン容器内に入れて混合する。続いて、その混合液を、ウォーターバスを用いて８０℃で保温しながら強力機械撹拌によって６時間撹拌する。また、撹拌後の混合液を１μｍのメンブレンフィルターによって真空濾過し、続く除染実験に用いるための洗浄液として抽出する。また、残渣は、ケーキ洗浄・脱水の上、その線量を測定しておく。
Similarly to Example 1, in Example 2, prior to the decontamination experiment, preliminary extraction is performed to obtain a cleaning solution used in the experiment. Pre-extraction is performed according to the following procedure.
First, 50 g of contaminated incinerated ash contaminated with radioactive cesium (water content 30%) and 500 mL of cleaning solution (KOH solution 5 M / L) are placed in a 1 liter polypropylene container and mixed. Subsequently, the mixture is stirred for 6 hours by vigorous mechanical stirring while being kept at 80 ° C. using a water bath. Further, the mixed solution after stirring is vacuum filtered through a 1 μm membrane filter and extracted as a cleaning solution for use in subsequent decontamination experiments. In addition, the dose of the residue is measured after cake washing and dehydration.
続いて、この洗浄処理液から吸着剤を用いて放射性物質を除去する。
本作業では、容量１リットルの撹拌槽に洗浄処理液５００ｍＬと、吸着剤として３ｇのゼオライトを入れ、１時間撹拌して放射性物質を吸着剤に吸着させる。また、撹拌後の洗浄処理液を１μｍのメンブレンフィルターによって真空濾過して、放射性物質を洗浄処理液中から吸着剤と共に除去する。
Subsequently, the radioactive material is removed from the cleaning treatment liquid using an adsorbent.
In this operation, 500 mL of the cleaning treatment liquid and 3 g of zeolite as an adsorbent are placed in a 1 liter stirring tank, and the mixture is stirred for 1 hour to adsorb the radioactive material to the adsorbent. Further, the washing treatment liquid after stirring is vacuum filtered through a 1 μm membrane filter, and the radioactive substance is removed from the washing treatment liquid together with the adsorbent.
続いて、このようにして得られた放射性物質除去済みの洗浄処理液を再生する。
本作業では、容量１リットルの撹拌槽に放射性物質除去済みの洗浄処理液と水酸化カルシウム（Ｃａ（ＯＨ）２）を１６，１ｇ添加して３時間撹拌し、その洗浄処理液中にアルカリ（ＮａＯＨ）を再合成する。撹拌後の洗浄処理液を孔径が１μｍのメンブレンフィルターによって真空濾過して、リン酸カルシウムを洗浄処理液中から回収すると共に、その残液を再生洗浄液として抽出する。また、残渣は、ケーキ洗浄・脱水の上、その線量を測定しておく。
Subsequently, the cleaning liquid obtained after removing the radioactive material is regenerated.
In this work, 16 and 1 g of cleaning treatment liquid and calcium hydroxide (Ca (OH) 2 ) from which radioactive substances have been removed are added to a 1 liter stirring tank and stirred for 3 hours. NaOH) is re-synthesized. The washing treatment liquid after stirring is vacuum filtered through a membrane filter having a pore size of 1 μm to collect calcium phosphate from the washing treatment liquid, and the remaining liquid is extracted as a regenerated washing liquid. In addition, the dose of the residue is measured after cake washing and dehydration.
続いて、上記作業で得られた再生洗浄液を用いて２回目の撹拌洗浄を実施する。
本作業では、１回目の洗浄を終えた焼却灰を再び同様の手順にて再洗浄する。２回目の洗浄では、その洗浄に用いる洗浄液として、上記工程で得られた再合成洗浄液に水酸化カリウムを１５，４ｇ補給して必要なアルカリ度を維持し、強力機械撹拌によって６時間、再洗浄する。
Subsequently, a second stirring and cleaning is performed using the regenerated cleaning liquid obtained in the above operation.
In this work, the incinerated ash after the first washing is washed again in the same procedure. In the second washing, as a washing liquid used for the washing, 15.4 g of potassium hydroxide is replenished to the re-synthetic washing liquid obtained in the above step to maintain the necessary alkalinity, and the washing is performed again for 6 hours by vigorous mechanical stirring. To do.
そして、再洗浄を終えた汚染焼却灰をフィルタープレスにかけて真空濾過する。また、この真空濾過によって固液分離された残渣をケーキ洗浄・脱水の上、その線量を測定する。 Then, the contaminated incineration ash that has been rewashed is vacuum filtered through a filter press. Moreover, the residue separated by solid-liquid separation by this vacuum filtration is subjected to cake washing and dehydration, and the dose is measured.
以上の工程を経て得られた残灰の除染結果を表２に示す。 Table 2 shows the decontamination results of the residual ash obtained through the above steps.
表２から明らかなように、本除染方法で除染した場合、その残灰（残渣）の重量は、リン酸カルシウム等の回収分を差し引いて考えれば、洗浄前と洗浄後で殆ど変化しておらず、しかも、その放射線量は２回目の洗浄を終えた時点で約１／９迄低下している。
すなわち、セメント原料等に利用可能な残灰を減らすこと無く、大幅な除染に成功した。
As is apparent from Table 2, when decontamination is performed by this decontamination method, the weight of the residual ash (residue) hardly changes after washing and after washing, considering the recovered amount of calcium phosphate and the like. Moreover, the radiation dose is reduced to about 1/9 when the second cleaning is completed.
In other words, it succeeded in significant decontamination without reducing the residual ash available for cement raw materials.
このように本除染方法によれば、放射性物質で汚染された焼却灰や土壌の線量を低減できるため、それら放射線汚染物を資源として再利用できる。また、放射性物質を吸着剤に選択的に吸着させて処理できるため放射性物質の濃縮化による減量化も可能である。また、これによって中間貯蔵施設の規模縮小化にも貢献できる。また、本除染方法の過程で化学的に生成されるリン酸カルシウムおよび水酸化アルミニウムの固体は放射線の汚染を受けないため、各々、肥料や凝集剤の原料として有効利用することができる。 Thus, according to the present decontamination method, the dose of incinerated ash and soil contaminated with radioactive substances can be reduced, so that these radioactive contaminants can be reused as resources. In addition, since the radioactive substance can be selectively adsorbed on the adsorbent and processed, the amount of the radioactive substance can be reduced by concentrating the radioactive substance. This can also contribute to reducing the scale of intermediate storage facilities. In addition, the calcium phosphate and aluminum hydroxide solids that are chemically generated during the decontamination process are not contaminated by radiation, and can be effectively used as raw materials for fertilizers and flocculants, respectively.
Claims (5)
前記放射性汚染物とアルカリ性を示す洗浄液とを混合し、その混合液を加温下で撹拌洗浄して前記放射性物質を洗浄処理液中に溶出させて抽出する工程と、
吸着剤を用いて前記洗浄処理液中に溶出した放射性物質を除去する工程と、
前記放射性物質が除去された洗浄処理液に、水酸化カルシウム若しくは水酸化アルミ結晶のうちの何れか一方、又は両方を加えることで、前記洗浄処理液中に、前記放射性物質を含む洗浄処理液を抽出する工程で用いるアルカリ溶液を再合成した再合成洗浄液を得る工程と、
を有することを特徴とする放射性汚染物の除染方法。 A decontamination method for radioactive contaminants contaminated with radioactive substances,
A step of mixing the radioactive contaminants and a cleaning solution showing alkalinity, stirring and washing the mixed solution under heating, and eluting and extracting the radioactive substance in a cleaning treatment solution;
Removing radioactive material eluted in the cleaning solution using an adsorbent;
By adding one or both of calcium hydroxide and aluminum hydroxide crystals to the cleaning treatment liquid from which the radioactive substance has been removed, a cleaning treatment liquid containing the radioactive substance is added to the cleaning treatment liquid. A step of obtaining a re-synthesizing washing solution obtained by re-synthesizing the alkaline solution used in the extraction step ;
A decontamination method for radioactive contaminants, comprising:
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