JP2014134404A - Method for decontaminating cesium contamination - Google Patents
Method for decontaminating cesium contamination Download PDFInfo
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- JP2014134404A JP2014134404A JP2013001411A JP2013001411A JP2014134404A JP 2014134404 A JP2014134404 A JP 2014134404A JP 2013001411 A JP2013001411 A JP 2013001411A JP 2013001411 A JP2013001411 A JP 2013001411A JP 2014134404 A JP2014134404 A JP 2014134404A
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- 229910052792 caesium Inorganic materials 0.000 title claims abstract description 66
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 title claims abstract description 57
- 238000000034 method Methods 0.000 title abstract description 24
- 238000011109 contamination Methods 0.000 title 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 63
- 238000004140 cleaning Methods 0.000 claims abstract description 47
- 239000007788 liquid Substances 0.000 claims abstract description 42
- 238000005202 decontamination Methods 0.000 claims abstract description 37
- 230000002378 acidificating effect Effects 0.000 claims abstract description 14
- -1 hydroxide ions Chemical class 0.000 abstract description 33
- 230000000694 effects Effects 0.000 abstract description 28
- 230000003588 decontaminative effect Effects 0.000 abstract description 24
- 238000007654 immersion Methods 0.000 abstract description 23
- 230000009471 action Effects 0.000 abstract description 11
- 239000001257 hydrogen Substances 0.000 abstract description 11
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 11
- 238000000926 separation method Methods 0.000 abstract description 6
- 238000006386 neutralization reaction Methods 0.000 abstract description 3
- HUCVOHYBFXVBRW-UHFFFAOYSA-M caesium hydroxide Inorganic materials [OH-].[Cs+] HUCVOHYBFXVBRW-UHFFFAOYSA-M 0.000 description 16
- 239000000243 solution Substances 0.000 description 16
- 238000005406 washing Methods 0.000 description 14
- MFGOFGRYDNHJTA-UHFFFAOYSA-N 2-amino-1-(2-fluorophenyl)ethanol Chemical compound NCC(O)C1=CC=CC=C1F MFGOFGRYDNHJTA-UHFFFAOYSA-N 0.000 description 13
- 239000002699 waste material Substances 0.000 description 11
- 239000002689 soil Substances 0.000 description 9
- 230000008569 process Effects 0.000 description 8
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 7
- 229910017604 nitric acid Inorganic materials 0.000 description 7
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 6
- DCYOBGZUOMKFPA-UHFFFAOYSA-N iron(2+);iron(3+);octadecacyanide Chemical compound [Fe+2].[Fe+2].[Fe+2].[Fe+3].[Fe+3].[Fe+3].[Fe+3].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-] DCYOBGZUOMKFPA-UHFFFAOYSA-N 0.000 description 6
- 229960003351 prussian blue Drugs 0.000 description 6
- 239000013225 prussian blue Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- KOPBYBDAPCDYFK-UHFFFAOYSA-N caesium oxide Chemical compound [O-2].[Cs+].[Cs+] KOPBYBDAPCDYFK-UHFFFAOYSA-N 0.000 description 5
- 229910001942 caesium oxide Inorganic materials 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 230000005855 radiation Effects 0.000 description 5
- 239000002253 acid Substances 0.000 description 4
- TVFDJXOCXUVLDH-RNFDNDRNSA-N cesium-137 Chemical compound [137Cs] TVFDJXOCXUVLDH-RNFDNDRNSA-N 0.000 description 3
- 238000011038 discontinuous diafiltration by volume reduction Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000003595 mist Substances 0.000 description 3
- 239000002105 nanoparticle Substances 0.000 description 3
- 239000011347 resin Substances 0.000 description 3
- 229920005989 resin Polymers 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000012795 verification Methods 0.000 description 3
- PNDPGZBMCMUPRI-HVTJNCQCSA-N 10043-66-0 Chemical compound [131I][131I] PNDPGZBMCMUPRI-HVTJNCQCSA-N 0.000 description 2
- 239000003957 anion exchange resin Substances 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- TVFDJXOCXUVLDH-OUBTZVSYSA-N cesium-134 Chemical compound [134Cs] TVFDJXOCXUVLDH-OUBTZVSYSA-N 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- AKUNKIJLSDQFLS-UHFFFAOYSA-M dicesium;hydroxide Chemical compound [OH-].[Cs+].[Cs+] AKUNKIJLSDQFLS-UHFFFAOYSA-M 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000003912 environmental pollution Methods 0.000 description 2
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- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 1
- 208000019901 Anxiety disease Diseases 0.000 description 1
- 241001237160 Kallima inachus Species 0.000 description 1
- 239000004677 Nylon Substances 0.000 description 1
- 229910021536 Zeolite Inorganic materials 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 230000036506 anxiety Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- FFBHFFJDDLITSX-UHFFFAOYSA-N benzyl N-[2-hydroxy-4-(3-oxomorpholin-4-yl)phenyl]carbamate Chemical compound OC1=C(NC(=O)OCC2=CC=CC=C2)C=CC(=C1)N1CCOCC1=O FFBHFFJDDLITSX-UHFFFAOYSA-N 0.000 description 1
- 238000009933 burial Methods 0.000 description 1
- NCMHKCKGHRPLCM-UHFFFAOYSA-N caesium(1+) Chemical compound [Cs+] NCMHKCKGHRPLCM-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
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- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
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- 150000002500 ions Chemical class 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
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- 150000002825 nitriles Chemical class 0.000 description 1
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- 230000002195 synergetic effect Effects 0.000 description 1
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- 231100000331 toxic Toxicity 0.000 description 1
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- 239000003643 water by type Substances 0.000 description 1
- 239000010457 zeolite Substances 0.000 description 1
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- Processing Of Solid Wastes (AREA)
Abstract
Description
本発明は、放射性セシウムで汚染された土壌や焼却灰、枯草などのセシウム汚染物からセシウムを除去して除染する処理方法に関する。 The present invention relates to a treatment method for removing cesium from decontaminated cesium such as soil, incinerated ash, and hay, contaminated with radioactive cesium.
平成２３年３月１１日に発生した東北地方太平洋沖地震は未曾有の東日本大震災を引き起こし、この地震と津波によって発生した東京電力福島第一原子力発電所事故は放射性物質の漏出に伴う深刻な環境汚染問題を生じさせるに至っている。原子炉から放出された放射性物質は主としてヨウ素１３１，セシウム１３４およびセシウム１３７であり、このうち半減期が８日と短いヨウ素１３１は既に消滅しているが、セシウム１３４（半減期＝約２年）とセシウム１３７（半減期＝約３０年）については現在もなお周辺地域の土壌などに残存していると考えられることから、セシウムの除染作業が急務である。 The 2011 off the Pacific coast of Tohoku Earthquake that occurred on March 11, 2011 caused the unprecedented Great East Japan Earthquake. Has led to problems. The radioactive materials released from the nuclear reactor are mainly iodine 131, cesium 134 and cesium 137. Among them, iodine 131 having a short half-life of 8 days has already disappeared, but cesium 134 (half-life = about 2 years) Since cesium 137 (half-life = about 30 years) is still considered to remain in the surrounding soil, cesium decontamination work is urgently needed.
このような背景から様々な除染方法が開発され提案されており、たとえば、独立行政法人産業技術総合研究所は、土壌を低濃度の酸水溶液で洗浄することによりセシウムイオンを酸水溶液中に脱離させた後、プルシアンブルーナノ粒子に吸着させて回収する技術を開発したとされる（非特許文献１）。これによれば、０．５モル／Ｌ程度の低濃度の希硫酸または稀硝酸であっても高収率でセシウムイオンを抽出することができ、且つ、これをプルシアンブルーナノ粒子でほぼ１００％回収することができ、しかもプルシアンブルーナノ粒子の使用量は汚染土壌の１／１５０で済むことから大幅に廃棄物を減量することができたと報告されている。 Various decontamination methods have been developed and proposed from such a background. For example, the National Institute of Advanced Industrial Science and Technology (AIST) removes cesium ions into an acid aqueous solution by washing the soil with a low concentration acid aqueous solution. After separation, it is said that the technology of adsorbing and recovering to Prussian blue nanoparticles was developed (Non-patent Document 1). According to this, cesium ions can be extracted with a high yield even with dilute sulfuric acid or dilute nitric acid at a low concentration of about 0.5 mol / L, and this is almost 100% by Prussian blue nanoparticles. It is reported that the amount of waste can be significantly reduced because the amount of Prussian blue nanoparticles used can be 1/150 of the contaminated soil.
しかしながら、低濃度とは言っても硫酸や硝酸などの強酸薬品を使用することは、その保管・運搬・取扱時の危険性や、処理後の廃棄による環境汚染などが懸念される。設備の整った環境で熟練者が処理するのであれば問題ないとしても、一般の人が実行する方法としては処理を誤った場合に人体などに与える危険が皆無であるとは言えないし、心理的な不安要素も大きい。 However, using low-concentration strong acid chemicals such as sulfuric acid and nitric acid is a concern for its storage, transportation and handling, and environmental pollution due to disposal after processing. Even if there is no problem as long as an expert performs the treatment in a well-equipped environment, it cannot be said that there is no danger to the human body if the treatment is wrong as a method that the general person performs, psychologically There is also a big anxiety factor.
また、上記従来技術は希硝酸溶液などをたとえば９５℃、より好ましくは加圧下で１００℃以上に加温して処理することが提案されているが、汚染廃棄物現場などでこのような処理温度を採用することは非現実的である。上記従来技術の図３には、０．５モル／Ｌ希硝酸を固液比２００で混合して４５分静置した場合のセシウムイオン抽出量の温度依存性が示されているが、２００℃ではセシウムイオンをほぼ１００％抽出することができるものの、１００℃を下回ると極端に効果が低下し、常温ではほとんどセシウムイオンが抽出されないことを示している。すなわち、この方法は少なくとも１００℃に近い高温まで加熱することが必須条件であり、常温での処理では効果が認められない。 Further, the above prior art has proposed that a dilute nitric acid solution is heated to, for example, 95 ° C., more preferably 100 ° C. or higher under pressure, but such a processing temperature at a contaminated waste site or the like is proposed. Adopting is unrealistic. FIG. 3 of the above prior art shows the temperature dependence of the amount of cesium ion extracted when 0.5 mol / L dilute nitric acid is mixed at a solid-liquid ratio of 200 and allowed to stand for 45 minutes. Although it is possible to extract almost 100% of cesium ions, the effect is extremely reduced below 100 ° C., indicating that almost no cesium ions are extracted at room temperature. That is, in this method, it is essential to heat to a high temperature close to at least 100 ° C., and no effect is observed in the treatment at room temperature.
さらに、プルシアンブルーも熱やアルカリに反応して生体に強い毒性を示すシアン化合物を遊離するので、一般に使用するには危険性が大きい。これらの理由から、上記非特許文献１に記載の方法は、一定の条件下においてはその効果が認められるとしても、実際上は採用が困難であるため、実験的な実施に止まっているのが現状である。 Furthermore, Prussian blue also reacts with heat and alkali to release cyanide compounds that are highly toxic to living organisms, so it is very dangerous for general use. For these reasons, the method described in Non-Patent Document 1 is practically difficult to adopt even if the effect is recognized under a certain condition, and is therefore only experimentally implemented. Currently.
ところで、アルカリ性水は、排水や土壌などを所望のｐＨ値に調節するためのｐＨ調整水として、また、金属や回路基板などに付着した汚れ（有機物、錆など）を分解して洗浄するための洗浄水として、使用されている。アルカリ性水の製造方法としては、原水をイオン交換樹脂に通水してイオン交換させる方法が知られている（特許文献１）。すなわち、原水を強アルカリ性アニオン交換樹脂を用いた塔に通水させると、原水中のＣｌ−、ＮＯ３ −、ＳＯ４ ２−、ＨＣＯ３ −などのアニオンが強酸性アニオン交換樹脂に電着されているＯＨ−（水酸化物イオン）を置換するので、通水後の処理済水のＯＨ−が増加してアルカリ性水が得られる。 By the way, alkaline water is used as pH adjustment water for adjusting drainage or soil to a desired pH value, and for decomposing and cleaning dirt (organic matter, rust, etc.) adhering to metals and circuit boards. Used as cleaning water. As a method for producing alkaline water, a method is known in which raw water is passed through an ion exchange resin for ion exchange (Patent Document 1). That is, when raw water is passed through a tower using a strong alkaline anion exchange resin, anions such as Cl − , NO 3 − , SO 4 2− , and HCO 3 − in the raw water are electrodeposited onto the strongly acidic anion exchange resin. Since OH − (hydroxide ions) are substituted, the OH − of the treated water after passing water increases and alkaline water is obtained.
本発明者は、アルカリ性水について様々な実験と研究を重ねていく中で、アルカリ性水が非常に高いセシウム除去能力を有することを見出し、安全且つ効果的にセシウムを除去することができる新規な手法として本発明を完成するに至ったものである。 The present inventor has discovered that alkaline water has a very high ability to remove cesium during various experiments and research on alkaline water, and is able to remove cesium safely and effectively. As a result, the present invention has been completed.
上記課題を解決するための手段として、本発明は、セシウムで汚染された被処理物を、ｐＨ値が９．０以上、好ましくは１０．５以上のアルカリ性水からなる洗浄液に浸漬することを特徴とするセシウム除染方法である。セシウムは、水に溶けると２Ｃｓ＋Ｈ２Ｏ→２ＣｓＯＨ＋Ｈ２の反応を起して水酸化セシウム（ＣｓＯＨ）に変化して土壌や樹木などに付着し、また、一部は空気中の酸素と反応して酸化セシウム（４Ｃｓ＋Ｈ２→２Ｃｓ２Ｏ）となって付着するが、アルカリ性水（Ｈ２Ｏ＋ＯＨ−）に浸漬することにより、被処理物に酸化セシウムの形で被処理物に付着していたセシウムが水酸化物イオン（ＯＨ−）の作用で中和・剥離されると共に、水酸化セシウムも水（Ｈ２Ｏ）に存在する水素イオン（Ｈ＋）の作用で中和・剥離される。これらの相乗作用を通じて、セシウム汚染された被処理物を効果的に除染することができる。なお、処理後の洗浄廃液中には、水酸化セシウムの分子に水素イオンが反応してイオン化したセシウムイオン（Ｃｓ＋）が存在するが、水中に閉じ込められている限り外部には放出されない。この方法において、被処理物を洗浄液に浸漬する間に洗浄液を振動させると、さらに飛躍的に除染効果を高めることができる。 As means for solving the above-mentioned problems, the present invention is characterized by immersing an object to be treated contaminated with cesium in a cleaning solution comprising alkaline water having a pH value of 9.0 or more, preferably 10.5 or more. And cesium decontamination method. When dissolved in water, cesium causes a reaction of 2Cs + H 2 O → 2CsOH + H 2 to change to cesium hydroxide (CsOH) and adheres to soil, trees, etc., and part of it reacts with oxygen in the air. Cesium oxide (4Cs + H 2 → 2Cs 2 O) adheres, but by immersing in alkaline water (H 2 O + OH − ), cesium attached to the object in the form of cesium oxide is attached to the object. While neutralized and separated by the action of hydroxide ions (OH − ), cesium hydroxide is also neutralized and separated by the action of hydrogen ions (H + ) present in water (H 2 O). Through these synergistic actions, the object to be treated contaminated with cesium can be effectively decontaminated. In the cleaning waste liquid after the treatment, cesium ions (Cs + ) ionized by the reaction of hydrogen ions with cesium hydroxide molecules are present but are not released to the outside as long as they are confined in water. In this method, if the cleaning liquid is vibrated while the object to be treated is immersed in the cleaning liquid, the decontamination effect can be further enhanced.
本発明の好適な一態様によれば、セシウムで汚染された被処理物を、ｐＨ値が９．０以上、好ましくは１０．５以上のアルカリ性水からなる洗浄液に浸漬し、その後に分離抽出した被処理物を、酸性水からなる二次洗浄液に浸漬処理する。上記したように、アルカリ性水での浸漬処理は主として酸化セシウム（Ｃｓ２Ｏ）の形で付着しているセシウムを水酸化物イオン（ＯＨ−）の作用で中和・剥離して除染するのに有効であり、水酸化セシウム（ＣｓＯＨ）の形で付着しているセシウムに対しても水素イオン（Ｈ＋）の作用によって概ね十分に中和・剥離することが可能ではあるが、付着セシウム量とモル数との関係で水酸化セシウムの除去作用が必ずしも十分に行われない場合があり得る。このような場合であっても、アルカリ性水での一次浸漬処理後に酸性水での二次浸漬処理を行うことにより、水酸化セシウムの形で付着しているセシウムも有効に除去することができ、酸化セシウムおよび水酸化セシウムのいずれの形態で付着しているかを問わず（これを確認することは理論的に可能ではあるが、膨大な除染処理量を考えると物理的に実行不可能である）、除染効果を増大させ且つ安定化させることができる。 According to a preferred embodiment of the present invention, the object to be treated contaminated with cesium is immersed in a cleaning solution composed of alkaline water having a pH value of 9.0 or more, preferably 10.5 or more, and then separated and extracted. A to-be-processed object is immersed in the secondary washing | cleaning liquid which consists of acidic water. As described above, the immersion treatment with alkaline water mainly decontaminates cesium adhering in the form of cesium oxide (Cs 2 O) by neutralizing and peeling off by the action of hydroxide ions (OH − ). It is effective for cesium hydroxide (CsOH), and it is possible to neutralize and peel almost completely by the action of hydrogen ions (H + ), but the amount of attached cesium In some cases, the removal effect of cesium hydroxide is not always sufficiently performed in relation to the number of moles. Even in such a case, cesium adhering in the form of cesium hydroxide can be effectively removed by performing a secondary immersion treatment with acidic water after a primary immersion treatment with alkaline water, Regardless of whether it is attached in the form of cesium oxide or cesium hydroxide (it is theoretically possible to confirm this, but it is physically infeasible considering the huge amount of decontamination treatment ), The decontamination effect can be increased and stabilized.
アルカリ性水での浸漬処理後の洗浄廃液中には、水酸化セシウムの分子に水酸化物イオンが反応してイオン化したセシウムイオン（Ｃｓ−）が存在し、酸性水での浸漬処理後の洗浄廃液中には、水酸化セシウムの分子に水素イオンが反応してイオン化したセシウムイオン（Ｃｓ＋）が存在するが、これらのセシウムイオンは他の物質と非常に結合しやすい性質を持っているので、これらを廃液中の水酸化物イオンおよび水素イオンといち早く結合させて安定した化合物である酸化セシウムおよび水酸化セシウムに固定させることができる。前記非特許文献１では、イオンとして存在するセシウムをプルシアンブルーに吸着させることが提案されており、これとは別にゼオライトなどに吸着させる手法も提案されているが、これらの手法はセシウム汚染物質を新たに作り出していることに他ならず、好ましい手法とは言えない。本発明によれば、水に含まれる水素イオンと水酸化物イオンの作用でセシウムイオンを凝集させるので、新たな汚染物質を産出することがなく、また移動もし易く、且つ移動中の被爆も防ぐことができる。また、廃液中の水をミストや気体として放出することにより減容も容易である。 The cleaning waste liquid after immersion treatment with alkaline water contains cesium ions (Cs − ) ionized by the reaction of hydroxide ions with cesium hydroxide molecules, and the cleaning waste liquid after immersion treatment with acidic water. Among them, there are cesium ions (Cs + ) ionized by the reaction of hydrogen ions with cesium hydroxide molecules, but these cesium ions are very easy to bond with other substances, These can be quickly bonded to hydroxide ions and hydrogen ions in the waste liquid and fixed to cesium oxide and cesium hydroxide, which are stable compounds. In Non-Patent Document 1, it is proposed that cesium existing as ions is adsorbed on Prussian blue, and separately, a method of adsorbing to zeolite or the like is also proposed. It is nothing but a new method that is being created. According to the present invention, cesium ions are agglomerated by the action of hydrogen ions and hydroxide ions contained in water, so that no new pollutants are produced, they are easy to move, and also prevent exposure during movement. be able to. Further, volume reduction is easy by discharging water in the waste liquid as mist or gas.
本発明によれば、前述の作用を通じてセシウム汚染被処理物を効果的に除染することができる。本発明による除染処理は加熱を必要とせず、常温で行うことができるので、汚染廃棄物現場などでも有効に実施可能であると共に、東北地方などにおいても季節を問わずに実施可能である。また、本発明で使用する洗浄液（アルカリ性水、酸性水）は、安価で入手容易な地下水や水道水などを原水に用い、この原水中の水酸化物イオン・水素イオンをイオン交換を介して増大させることによって、安価且つ効率的に大量生産することが可能である。さらに、これらの洗浄液は人体に触れても全く無害であり、刺激や臭気もほとんど無い。すなわち、本発明方法は、硫酸や硝酸などの強酸薬品やプルシアンブルーなどの毒性を示す物質を使用する従来法と比較すると、洗浄液の保管・運搬・取扱時の危険性がなく、処理後廃棄しても環境汚染を生じることがない点において、きわめて高い安全性が保証されたセシウム除染方法である。 According to the present invention, a cesium-contaminated workpiece can be effectively decontaminated through the above-described action. Since the decontamination treatment according to the present invention does not require heating and can be performed at room temperature, it can be effectively carried out at a contaminated waste site or the like, and can be carried out in the Tohoku region or the like regardless of the season. The cleaning liquid (alkaline water, acidic water) used in the present invention uses groundwater or tap water that is inexpensive and easily available as raw water, and increases the hydroxide ions and hydrogen ions in the raw water through ion exchange. By doing so, it is possible to mass-produce cheaply and efficiently. Furthermore, these cleaning solutions are completely harmless even when touched by the human body, and there is almost no irritation or odor. In other words, the method of the present invention has no danger during storage, transportation and handling of cleaning liquids compared to conventional methods using toxic substances such as strong acid chemicals such as sulfuric acid and nitric acid and Prussian blue, and is discarded after treatment. However, it is a cesium decontamination method that guarantees extremely high safety in that it does not cause environmental pollution.
＜セシウム除染工程１＞
図１は本発明方法の一実施形態によるセシウム除染の工程図である。セシウム汚染された被処理物（土壌、枯葉、焼却灰など）を洗浄槽に入れ、そこにアルカリ性水からなる洗浄液を注入して、被処理物を洗浄液に浸漬する。浸漬時間は３〜５分間で十分な効果が得られるが、もちろんそれ以上の長時間浸漬させても良い。この洗浄槽の外部（底面など）に超音波発振素子などを配置して、浸漬処理の間洗浄液を振動させると、より効果的である。所定時間の浸漬処理終了後、フィルターにかけて固液分離する。フィルターの種類は特に問われない。分離された処理済の被処理物は、乾燥後、たとえば樹脂コーティング７などによる加工処理を施された後に、場外搬出される。後述するように、セシウムに汚染されていた被処理物はアルカリ性水による浸漬処理によって実質的に無害化されているので、樹脂コーティングされた固形物はコンクリート用の骨材や埋立材料などとして有効利用することができる。
<Cesium decontamination process 1>
FIG. 1 is a process diagram of cesium decontamination according to an embodiment of the method of the present invention. An object to be treated (soil, dead leaves, incinerated ash, etc.) contaminated with cesium is put into a washing tank, and a washing liquid made of alkaline water is poured into the washing tank, and the article to be treated is immersed in the washing liquid. A sufficient effect is obtained when the immersion time is 3 to 5 minutes, but it may of course be immersed for a longer time. It is more effective to arrange an ultrasonic oscillation element or the like outside the cleaning tank (such as the bottom surface) and vibrate the cleaning liquid during the immersion process. After completion of the immersion treatment for a predetermined time, it is filtered through a solid-liquid separation. The type of filter is not particularly limited. The separated processed object is dried, and after being processed by, for example, the resin coating 7, it is carried out of the field. As will be described later, the treated material contaminated with cesium has been made substantially harmless by immersion treatment with alkaline water, so the resin-coated solid material is effectively used as aggregate for concrete, landfill material, etc. can do.
一方、フィルターを通過したろ液（廃液）には、水酸化セシウムの分子に水素イオンが反応してイオン化したセシウムイオン（Ｃｓ＋）が存在するが、水中に閉じ込められている限り外部には放出されない。したがって、一定期間廃液処理槽に貯蔵した後、減容槽に移して廃液中の水をミストや気体として放出することにより容易に減容することができる。放出されるミストや気体はセシウムに汚染されていない純粋な水であるから、そのまま大気中に放出し、または川や海に放流しても何ら問題はない。このような減容処理により水分除去された後に残る濃縮セシウムは、たとえばＦＲＰなどで形成したタンクに密閉して地下に埋設し、セシウム１３７の半減期（約３０年）の経過を待つ。地下埋設については、約３０ｃｍの覆土によって地上へのセシウム放散を実質的に防止できることが確認されている。 On the other hand, the filtrate (waste liquid) that has passed through the filter contains cesium ions (Cs + ) that are ionized by the reaction of hydrogen ions with cesium hydroxide molecules, but they are released to the outside as long as they are confined in water. Not. Therefore, after storing in a waste liquid treatment tank for a certain period, it can be easily reduced by transferring to a volume reduction tank and releasing the water in the waste liquid as mist or gas. Since the released mist and gas are pure water not contaminated with cesium, there is no problem even if it is released into the atmosphere as it is or discharged into the river or the sea. The concentrated cesium remaining after moisture removal by such volume reduction treatment is sealed in a tank formed of, for example, FRP and buried underground, and waits for the half-life of cesium 137 (about 30 years). Regarding underground burial, it has been confirmed that cesium emission to the ground can be substantially prevented by covering soil of about 30 cm.
＜セシウム除染工程２＞
図２は本発明方法の他実施形態によるセシウム除染の工程図である。この工程は、被処理物にアルカリ性水（一次洗浄液）による浸漬処理（一次洗浄）を施して固液分離する工程は図１の場合と同様であるが、さらに、一次洗浄済のセシウム汚染物を二次洗浄槽に入れ、そこに酸性水からなる二次洗浄液を注入して該二次洗浄液に浸漬する処理を行う。二次洗浄液への浸漬時間も３〜５分間で十分であるが、もちろんそれ以上の長時間浸漬させても良い。二次洗浄においても、洗浄槽に超音波発振素子などを配置して、浸漬処理の間洗浄液を振動させると、より効果的である。二次洗浄後、フィルターにかけて固液分離し、処理済のセシウム汚染物は前記と同様にして乾燥後、たとえば樹脂コーティング７などによる加工処理を施された後に場外搬出され、廃液は上記と同様にして減容した後、残存する濃縮セシウムを上記と同様にして地下埋設する。
<Cesium decontamination process 2>
FIG. 2 is a process diagram of cesium decontamination according to another embodiment of the method of the present invention. This process is the same as the case of FIG. 1 in which the object to be treated is subjected to immersion treatment (primary washing) with alkaline water (primary washing liquid) and solid-liquid separation is performed. It puts into a secondary washing tank, the secondary washing liquid which consists of acidic water is inject | poured there, and the process immersed in this secondary washing liquid is performed. Although the immersion time in the secondary cleaning liquid is sufficient for 3 to 5 minutes, it may of course be immersed for a longer time. Also in the secondary cleaning, it is more effective to arrange an ultrasonic oscillation element or the like in the cleaning tank and vibrate the cleaning liquid during the immersion process. After the secondary cleaning, it is filtered through a solid-liquid separation, and the treated cesium contaminants are dried in the same manner as described above, and after being processed by, for example, the resin coating 7, are carried out of the field. After the volume is reduced, the remaining concentrated cesium is buried underground as described above.
＜セシウム除染効果の実証試験１＞
本発明による除染処理効果を確認するために、次の試験を行った。セシウムで汚染された枯葉を採取して試料とし、この試料１００ｇをビーカーに入れ、ここに洗浄液１００ｃｃを注入して試料に浸漬させ、攪拌機で攪拌して３分間放置し、３分経過後にペーパーフィルターでろ過して試料を取り出し、ナイロンメッシュの袋に入れて室内（室温：約２０℃）で自然乾燥した。処理前の枯葉の放射線量をガイガーカウンターで計測したところ、約３５０Ｂｑ／ｃｍ２の値を示した。洗浄液には、ｐＨ値が６通り（ｐＨ１２．５，１１．８，１０．５，９．０，８．５および７．９）に異なるアルカリ性水を用いた。洗浄槽中の液温はいずれも約１７℃であった。乾燥後の試料について再度ガイガーカウンターで放射線量を計測した結果は表１に示す通りであった。
<Verification test 1 of cesium decontamination effect>
In order to confirm the decontamination treatment effect according to the present invention, the following test was performed. A dead leaf contaminated with cesium is collected and used as a sample. 100 g of this sample is put into a beaker, 100 cc of a cleaning solution is poured into the sample, dipped in the sample, stirred for 3 minutes with a stirrer, and a paper filter after 3 minutes. The sample was taken out through filtration, put in a nylon mesh bag, and naturally dried indoors (room temperature: about 20 ° C.). When the radiation dose of dead leaves before treatment was measured with a Geiger counter, a value of about 350 Bq / cm 2 was shown. For the cleaning solution, alkaline waters having different pH values (pH 12.5, 11.8, 10.5, 9.0, 8.5 and 7.9) were used. The liquid temperature in the washing tank was about 17 ° C. The results of measuring the radiation dose again with the Geiger counter for the dried sample were as shown in Table 1.
この結果から、アルカリ性水に短時間浸漬するだけでセシウムが効果的に除去されることが実証された。セシウム除染効果はｐＨ値が大きいほど顕著になるが、ｐＨが９．０より小さくなると除染率が大きく低下する傾向が見られるので、ｐＨ値が９．０以下のアルカリ性水に浸漬させることが好ましい。ｐＨ９．０のアルカリ性水であっても４０％強の除染率が得られる。より好ましくは、ｐＨ値が１０．５以上のアルカリ性水に浸漬させることであり、これによって約５０％またはそれ以上の除染率が得られる。 From this result, it was demonstrated that cesium can be effectively removed by just immersing in alkaline water for a short time. The cesium decontamination effect becomes more pronounced as the pH value increases, but the decontamination rate tends to decrease greatly when the pH value is lower than 9.0. Therefore, the cesium decontamination effect should be immersed in alkaline water with a pH value of 9.0 or less. Is preferred. Even alkaline water having a pH of 9.0 can obtain a decontamination rate of over 40%. More preferably, it is immersed in an alkaline water having a pH value of 10.5 or more, whereby a decontamination rate of about 50% or more is obtained.
既述したように前記非特許文献１に記載の希硝酸などを使用する方法が常温ではほとんど効果を発揮しないことに鑑みれば、洗浄液を何ら加熱せずに浸漬処理するだけでこのような除染率が得られることは、当業者には到底予測不能な驚くべき効果であると言える。常温でのアルカリ性水による浸漬処理でこのような顕著なセシウム除染効果が得られることの理由は現時点で完全には解明されていないが、前記非特許文献１記載の方法では硝酸原液を希釈する際に水素イオンが消費されてしまって効率が低下するので、加熱しないと十分な効果が発揮されないのに対し、本発明方法ではアルカリ性水中の遊離水酸化物イオンの作用でセシウムを中和・剥離することができるので、加熱や希釈することなしに十分な除染効果が得られるものと推測される。 As described above, in view of the fact that the method using the dilute nitric acid described in Non-Patent Document 1 exhibits almost no effect at room temperature, such decontamination can be performed simply by immersing the cleaning solution without heating. It can be said that the fact that the rate is obtained is a surprising effect that is unpredictable to those skilled in the art. The reason why such a remarkable cesium decontamination effect can be obtained by immersion treatment with alkaline water at room temperature has not been completely elucidated at present, but the method described in Non-Patent Document 1 dilutes the nitric acid stock solution. However, hydrogen ions are consumed and the efficiency is reduced, so that sufficient effects are not exhibited unless heated, whereas in the method of the present invention, cesium is neutralized and separated by the action of free hydroxide ions in alkaline water. Therefore, it is estimated that a sufficient decontamination effect can be obtained without heating or diluting.
＜セシウム除染効果の実証試験２＞
次に、洗浄液を振動させながら浸漬処理を行うことによる除染処理効果を確認するために、次の試験を行った。セシウムで汚染された枯葉（放射線量：約３５０Ｂｑ／ｃｍ２）を採取して試料とし、この試料１００ｇをビーカーに入れ、ここに５通りのｐＨ値（ｐＨ１２．５，１１．８，１０．５，９．０および８．５）を有するアルカリ性水からなる洗浄液１００ｃｃを注入して試料に浸漬させ、攪拌機で攪拌して３分間放置し、この間洗浄液を３７ＫＨｚの振動周波数で振動させ、３分経過後にペーパーフィルターでろ過して試料を取り出し、乾燥した。洗浄液の液温はいずれも約１７℃であった。乾燥後の試料について再度ガイガーカウンターで放射線量を計測した結果は表２に示す通りであった。
<Verification test 2 of cesium decontamination effect>
Next, in order to confirm the decontamination treatment effect by performing the immersion treatment while vibrating the cleaning liquid, the following test was performed. Dead leaves contaminated with cesium (radiation dose: about 350 Bq / cm 2 ) are collected and used as a sample. 100 g of this sample is placed in a beaker, and there are five pH values (pH 12.5, 11.8, 10.5). , 9.0 and 8.5), 100 cc of a cleaning solution made of alkaline water is injected and immersed in a sample, stirred with a stirrer and allowed to stand for 3 minutes. During this period, the cleaning solution is vibrated at a vibration frequency of 37 KHz, and 3 minutes have passed. Later, the sample was removed by filtration through a paper filter and dried. The temperature of the cleaning liquid was about 17 ° C. The results of measuring the radiation dose again with the Geiger counter for the dried sample were as shown in Table 2.
この結果から、アルカリ性水に短時間浸漬させると共にその間に振動を加えることにより、セシウム除去効果がさらに飛躍的に向上することが実証された。より詳しくは、洗浄液が中性に近付くほど振動併用による向上効果が薄くなるが、ｐＨ値が１０．５以上のアルカリ性水を洗浄液とする場合に顕著な効果の向上が見られ、これによりセシウム除去効果が６５％以上に向上した。これは、セシウム汚染された土壌や焼却灰はトンパックと呼ばれる大型土嚢に収容した状態で管理保管されているのが現状であり、このため長期保管の間に土圧などによって固形に近い状態になっていることから、振動を与えて物理的に微細化しながら洗浄液に浸漬させることで細部にまで洗浄液を浸透させることができ、セシウムとの中和反応がより活発に行われて除染効果が増大するものと考えられる。 From this result, it was proved that the effect of removing cesium was drastically improved by immersing in alkaline water for a short time and applying vibration in the meantime. More specifically, the improvement effect due to the combined use of vibration becomes thinner as the cleaning solution approaches neutrality, but when the alkaline solution having a pH value of 10.5 or more is used as the cleaning solution, a remarkable improvement is seen, thereby removing cesium. The effect was improved to 65% or more. This is because cesium-contaminated soil and incineration ash are currently managed and stored in a large sandbag called a ton pack. Therefore, it is possible to infiltrate the cleaning liquid in detail by immersing it in the cleaning liquid while applying vibration to physically refine it, and the neutralization reaction with cesium is carried out more actively, resulting in a decontamination effect. It is thought to increase.
＜セシウム除染効果の実証試験３＞
上記試験１においてｐＨ１０．５の洗浄液（一次洗浄液）で処理した後の試料をビーカーに入れ、ここに酸性水からなる洗浄液（二次洗浄液）１００ｃｃを注入して試料に浸漬させ、攪拌機で攪拌して３分間放置し、３分経過後にペーパーフィルターでろ過して試料を取り出し、乾燥した。二次洗浄液には、ｐＨ値が６通り（ｐＨ１２．５，１１．８，１０．５，９．０，８．５および７．９）に異なる酸性水を用いた。一次洗浄液および二次洗浄液の液温はいずれも約１７℃であった。このアルカリ性水での二次洗浄後、乾燥して得られた試料について再度ガイガーカウンターで放射線量を計測した結果は表３に示す通りであった。
<Verification test 3 of cesium decontamination effect>
In the test 1, the sample after being treated with the cleaning solution having a pH of 10.5 (primary cleaning solution) is put into a beaker, and 100 cc of the cleaning solution (secondary cleaning solution) made of acidic water is poured into the sample and immersed in the sample, and stirred with a stirrer. The sample was taken out for 3 minutes, filtered after 3 minutes with a paper filter, and dried. As the secondary washing solution, acidic water having different pH values (pH 12.5, 11.8, 10.5, 9.0, 8.5 and 7.9) was used. The liquid temperature of the primary cleaning liquid and the secondary cleaning liquid was both about 17 ° C. Table 3 shows the results of measuring the radiation dose with the Geiger counter again for the sample obtained after the secondary washing with alkaline water and drying.
この結果から、アルカリ性水による一次浸漬処理後に酸性水による二次浸漬処理を行うことにより、セシウム除去効果がさらに飛躍的に向上することが実証された。二次浸漬処理に用いる酸性水はｐＨ値が小さいほど向上効果が大きいが、一次浸漬処理に用いるアルカリ性水ほどｐＨ依存性は高くなく、酸性水であれば一定の効果が得られることが確認された。これは、アルカリ性水による一次浸漬処理によって酸化セシウム（Ｃｓ２Ｏ）の形で付着しているセシウムをアルカリ性水中の水酸化物イオン（ＯＨ−）の作用で中和・剥離して除去し、さらに、酸性水による二次浸漬処理によって水酸化セシウム（ＣｓＯＨ）の形で付着しているセシウムを酸性水中の水素イオン（Ｈ＋）の作用で中和・剥離して除去し、結果として、水酸化セシウムおよび酸化セシウムの両方の形態で付着しているセシウムを効果的に除去することができたものと考えられる。 From this result, it was demonstrated that the cesium removal effect is further improved dramatically by performing the secondary immersion treatment with acidic water after the primary immersion treatment with alkaline water. The acidic water used for the secondary immersion treatment has a higher effect as the pH value is smaller, but the pH dependence is not as high as the alkaline water used for the primary immersion treatment, and it has been confirmed that a certain effect can be obtained with acidic water. It was. This is because the cesium adhering in the form of cesium oxide (Cs2O) is removed by neutralization and separation by the action of hydroxide ions (OH − ) in alkaline water by the primary immersion treatment with alkaline water. Cesium adhering in the form of cesium hydroxide (CsOH) by the secondary immersion treatment with water is neutralized and removed by the action of hydrogen ions (H + ) in acidic water, and as a result, cesium hydroxide and It is considered that cesium adhering in both forms of cesium oxide could be effectively removed.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014163841A (en) * | 2013-02-26 | 2014-09-08 | Toshiba Corp | Sewage sludge incineration ash processing method |
| WO2018221310A1 (en) * | 2017-05-30 | 2018-12-06 | 国立大学法人横浜国立大学 | Optical receiver array and lidar device |
| JP2019163987A (en) * | 2018-03-19 | 2019-09-26 | 有限会社ジェニス・ホワイト | Release cleaning system for radioactive contaminant |
| JP7462251B2 (en) | 2019-07-08 | 2024-04-05 | 鹿島建設株式会社 | Methods for deflocculating and classifying soil |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014163841A (en) * | 2013-02-26 | 2014-09-08 | Toshiba Corp | Sewage sludge incineration ash processing method |
| WO2018221310A1 (en) * | 2017-05-30 | 2018-12-06 | 国立大学法人横浜国立大学 | Optical receiver array and lidar device |
| JP2019163987A (en) * | 2018-03-19 | 2019-09-26 | 有限会社ジェニス・ホワイト | Release cleaning system for radioactive contaminant |
| JP7462251B2 (en) | 2019-07-08 | 2024-04-05 | 鹿島建設株式会社 | Methods for deflocculating and classifying soil |
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