JP2001174587A - Decontamination method for liquid radioactive waste - Google Patents
Decontamination method for liquid radioactive wasteInfo
- Publication number
- JP2001174587A JP2001174587A JP36021799A JP36021799A JP2001174587A JP 2001174587 A JP2001174587 A JP 2001174587A JP 36021799 A JP36021799 A JP 36021799A JP 36021799 A JP36021799 A JP 36021799A JP 2001174587 A JP2001174587 A JP 2001174587A
- Authority
- JP
- Japan
- Prior art keywords
- waste liquid
- radioactive
- iron
- insoluble tannin
- uranium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Landscapes
- Water Treatment By Sorption (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、ウランに代表され
る放射性元素と鉄が主として溶解した強酸性の放射性廃
液から放射性元素を除去する放射性廃液の除染方法に関
する。更に詳しくは廃液及びこの廃液から生じた放射性
固体廃棄物の各放射能濃度を低減する除染方法に関する
ものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radioactive waste liquid decontamination method for removing a radioactive element from a strongly acidic radioactive waste liquid in which a radioactive element represented by uranium and iron are mainly dissolved. More specifically, the present invention relates to a decontamination method for reducing each radioactivity concentration of a waste liquid and a radioactive solid waste generated from the waste liquid.
【０００２】[0002]
【従来の技術】一般的に、ウランを主とした核燃料の加
工施設やプルトニウムを使用する核燃料再処理施設で
は、設備の機器表面や配管内部に付着したウラン等の放
射性元素を硝酸、硫酸等の鉱酸で溶解することにより、
放射性元素を除染している。この際、回収された廃液に
はウラン等の放射性元素の他に機器や配管の構成元素で
ある鉄が多く含まれる。従来、こうして回収された廃液
ではウラン等の放射性元素及び鉄の各濃度が高いため、
凝集沈殿法により廃液が処理されるのが一般的である。
この凝集沈殿法では、強酸性の廃液にＮａＯＨ等のアル
カリ水溶液を加えて廃液を中和する一次処理を行い、こ
の処理によりウラン等の放射性元素と鉄を共沈現象によ
り凝集沈殿させた後、この凝集沈殿物を固液分離して廃
液の放射能濃度を低減させている。そして必要に応じて
蒸発乾留やイオン交換法等による二次処理を行って放射
能濃度を排水管理基準以下にした後、廃液を施設外に排
出している。このとき発生する凝集沈殿物は乾燥した
後、放射能濃度が比較的高い放射性固体廃棄物として取
扱われている。上記一次処理に際しては、二次処理での
負荷を軽減する目的で、ｐＨ値をアルカリ側まで上げた
り、凝集助剤を添加して凝集効果を高めている。このた
め一次処理で生じた凝集沈殿物中へのウラン等の放射性
元素の移行率は高くなっている。一方、放射性固体廃棄
物の放射能濃度や長半減期核種の量に応じて、放射性固
体廃棄物を地下の浅層に処分するか、又は深層に処分す
るかの廃棄物の分別処分が近年検討されている。このた
め埋設施設への放射性固体廃棄物の輸送や最終の処分形
態を考慮した場合には、経済的にも放射性固体廃棄物中
へのウラン等の放射性元素の移行率を可能な限り低減し
ておくことが望まれる。2. Description of the Related Art Generally, in a nuclear fuel processing facility mainly using uranium or a nuclear fuel reprocessing facility using plutonium, radioactive elements such as uranium adhering to the equipment surface of a facility or the inside of a pipe are converted to nitric acid, sulfuric acid or the like. By dissolving with mineral acid,
It decontaminates radioactive elements. At this time, the recovered waste liquid contains a large amount of iron, which is a constituent element of equipment and piping, in addition to radioactive elements such as uranium. Conventionally, since the concentration of radioactive elements such as uranium and iron is high in the waste liquid thus collected,
Generally, the waste liquid is treated by the coagulation sedimentation method.
In this coagulation sedimentation method, a primary treatment is performed to neutralize the waste liquid by adding an alkaline aqueous solution such as NaOH to a strongly acidic waste liquid, and coagulate and precipitate a radioactive element such as uranium and iron by this treatment, This coagulated sediment is subjected to solid-liquid separation to reduce the radioactivity concentration of the waste liquid. Then, if necessary, secondary treatment such as evaporative distillation or ion exchange is performed to lower the radioactivity concentration below the wastewater management standard, and then the waste liquid is discharged outside the facility. After the coagulated precipitate generated at this time is dried, it is handled as radioactive solid waste having a relatively high radioactivity concentration. In the primary treatment, the pH value is increased to an alkaline side or a coagulation aid is added to increase the coagulation effect in order to reduce the load in the secondary treatment. For this reason, the transfer rate of radioactive elements such as uranium into the coagulated precipitate generated in the primary treatment is high. On the other hand, depending on the radioactivity concentration of radioactive solid waste and the amount of long-lived nuclides, the separation of radioactive solid waste into shallow underground or deep underground has been studied recently. Have been. For this reason, considering the transport of radioactive solid waste to landfill facilities and the final disposal form, the transfer rate of radioactive elements such as uranium into radioactive solid waste should be reduced as economically as possible. It is desired to keep.
【０００３】[0003]
【発明が解決しようとする課題】しかしながら、従来の
凝集沈殿法では廃液のウラン等の放射性元素の濃度を低
減できるものの、凝集沈殿物である放射性固体廃棄物の
放射能濃度が高く、廃棄物の処分費用が高くなる不具合
があった。また廃液中のウラン等の放射性元素を回収し
て再利用することは困難であった。However, although the concentration of radioactive elements such as uranium in the waste liquid can be reduced by the conventional coagulation and sedimentation method, the radioactive solid waste, which is the coagulated sediment, has a high radioactivity concentration and the waste There was a problem that the disposal cost was high. Also, it has been difficult to recover and reuse radioactive elements such as uranium in waste liquid.
【０００４】本発明の目的は、廃液の放射能濃度を低減
し得る放射性廃液の除染方法を提供することにある。本
発明の別の目的は、廃液から生じた放射性固体廃棄物の
放射能濃度を低減し得る放射性廃液の除染方法を提供す
ることにある。[0004] It is an object of the present invention to provide a method for decontaminating radioactive waste liquid which can reduce the radioactive concentration of the waste liquid. Another object of the present invention is to provide a method for decontaminating radioactive waste liquid that can reduce the radioactive concentration of radioactive solid waste generated from the waste liquid.
【０００５】[0005]
【課題を解決するための手段】請求項１に係る発明は、
(a) 放射性元素と鉄が主として溶解している強酸性の放
射性廃液にアルカリ水溶液を所定量だけ添加混合して前
記廃液を弱酸性にすることにより鉄のコロイドを生成す
る工程と、(b) 鉄のコロイドを生成した放射性廃液に粒
状の不溶性タンニンを添加混合する工程と、(c) 不溶性
タンニンを廃液から分離する工程とを含む放射性廃液の
除染方法である。放射性元素と鉄を含む強酸性の放射性
廃液を中和処理して弱酸性にすると鉄イオンの大部分は
コロイド状態になって液中に浮遊し、放射性元素の一部
は鉄の凝集力によりコロイドに取込まれるが、その大部
分は放射性イオンとして液中に存在する。この状態の廃
液に粒状の不溶性タンニンを添加混合すると、不溶性タ
ンニンは放射性イオンを吸着する。廃液から不溶性タン
ニンを分離することにより、廃液の放射能濃度を低減す
ることができる。The invention according to claim 1 is
(a) a step of adding a predetermined amount of an aqueous alkali solution to a strongly acidic radioactive waste liquid in which a radioactive element and iron are mainly dissolved and mixing them to make the waste liquid weakly acidic, thereby producing an iron colloid; and (b) A method for decontaminating a radioactive waste liquid, comprising: a step of adding and mixing granular insoluble tannin to a radioactive waste liquid that has produced iron colloid; and (c) a step of separating the insoluble tannin from the waste liquid. When a strongly acidic radioactive waste liquid containing radioactive elements and iron is neutralized to make it weakly acidic, most of the iron ions are in a colloidal state and float in the liquid, and some of the radioactive elements are colloidal due to the cohesion of iron. Most of which are present in the liquid as radioactive ions. When granular insoluble tannin is added to and mixed with the waste liquid in this state, the insoluble tannin adsorbs radioactive ions. By separating the insoluble tannin from the waste liquid, the radioactivity concentration of the waste liquid can be reduced.
【０００６】請求項２に係る発明は、請求項１に係る発
明であって、(d) 不溶性タンニンを分離した廃液にアル
カリ水溶液を添加混合して廃液に含まれる鉄を凝集沈殿
させる工程と、(e) 鉄を凝集沈殿させた廃液を固液分離
する工程とを更に含む放射性廃液の除染方法である。不
溶性タンニンを分離した廃液の放射能濃度は低くなって
いるため、この廃液の凝集沈殿物の放射能濃度も低くな
る。The invention according to claim 2 is the invention according to claim 1, wherein (d) a step of adding and mixing an aqueous alkali solution to the waste liquid from which the insoluble tannin has been separated to coagulate and precipitate iron contained in the waste liquid; (e) a step of solid-liquid separation of a waste liquid in which iron has been coagulated and precipitated. Since the radioactive concentration of the waste liquid from which the insoluble tannin has been separated is low, the radioactive concentration of the coagulated precipitate of this waste liquid is also low.
【０００７】[0007]
【発明の実施の形態】本発明の処理対象とする放射性廃
液は、放射性元素と鉄が主として溶解したｐＨが１以下
の強酸性の廃液である。この廃液を例示すれば、核燃料
の加工施設や、核燃料再処理施設における鉄製の機器又
は配管を硝酸又は硫酸により洗浄又は電解除染等の湿式
除染を行った際に発生する廃液、或いは鉄製の機器その
ものを解体廃棄する場合に表面汚染を取除く目的で酸に
よる除染を行った際に発生する廃液が挙げられる。放射
性元素には、ウラン、トリウム、超ウラン元素（ネプツ
ニウム、プルトニウム、アメリシウム、キュリウム）等
のアクチニド元素が挙げられる。BEST MODE FOR CARRYING OUT THE INVENTION The radioactive waste liquid to be treated in the present invention is a strongly acidic waste liquid having a pH of 1 or less in which radioactive elements and iron are mainly dissolved. As an example of this waste liquid, a waste liquid generated when performing a wet decontamination such as washing or electro-discharging with nitric acid or sulfuric acid on iron equipment or piping in a nuclear fuel processing facility or a nuclear fuel reprocessing facility, or an iron-based waste liquid A waste liquid generated when acid decontamination is performed for the purpose of removing surface contamination when dismantling and disposing of the equipment itself. Examples of radioactive elements include actinide elements such as uranium, thorium, and transuranium elements (neptunium, plutonium, americium, curium).
【０００８】この廃液に添加するアルカリ水溶液を例示
すれば、ＮａＯＨ、アンモニア水等の水溶液が挙げられ
る。このアルカリ水溶液を放射性廃液に添加する量は、
強酸性の放射性廃液のｐＨ値が不溶性タンニンの放射性
元素への吸着に適した領域であり、好ましくはｐＨ３以
上になる量であって、しかも鉄がアルカリ水溶液による
中和処理でイオン状態からコロイドになる量である。具
体的には鉄が加水分解して、鉄イオンの濃度が１００分
の１以下に低下する量が好ましく、この添加量は多くて
もｐＨ＝７未満の弱酸性領域が好ましい。アルカリ水溶
液の添加量が上記の量より少ない場合には、鉄のコロイ
ドが十分に生成されないので、イオン状の鉄が不溶性タ
ンニンに吸着されるため、鉄と放射性元素の分離効果が
期待できない。アルカリ水溶液の添加量が上記の量より
多い場合には、鉄のコロイドの凝集効果が促進され、放
射性元素とともに澱物を生成してしまうとともに、放射
性元素自体の加水分解が進み、イオン状態で不溶性タン
ニンに吸着することができなくなる。廃液中の鉄の濃度
に依存して不溶性タンニンの放射性元素の吸着量は変化
するが、鉄と放射性元素の廃液中のモル濃度比が５対１
以下であれば、ｐＨを４〜６程度に中和した場合には、
不溶性タンニンは廃液中の放射性元素を９０％近く吸着
するとともに、吸着した放射性元素に同伴する鉄の濃度
を数％以下に抑えることができる。このとき、鉄の９０
％以上が残液中に移行するが、放射性元素の移行率は数
％〜１０％程度と低減する。As an example of an alkaline aqueous solution to be added to the waste liquid, an aqueous solution of NaOH, ammonia water or the like can be given. The amount of this alkaline aqueous solution added to the radioactive waste liquid is
The pH value of the strongly acidic radioactive waste liquid is a region suitable for the adsorption of insoluble tannin to radioactive elements, preferably in an amount of pH 3 or more, and furthermore, iron is converted from an ionic state to a colloid by neutralization treatment with an aqueous alkali solution. Amount. Specifically, an amount in which iron is hydrolyzed to reduce the concentration of iron ions to 1/100 or less is preferable, and the amount of addition is preferably at most a weakly acidic region of less than pH = 7. If the amount of the alkaline aqueous solution is less than the above amount, iron colloid is not sufficiently generated, and ionic iron is adsorbed on the insoluble tannin, so that the effect of separating iron and radioactive elements cannot be expected. If the amount of the alkaline aqueous solution is larger than the above amount, the coagulation effect of the iron colloid is promoted, and a precipitate is formed together with the radioactive element, and the hydrolysis of the radioactive element itself proceeds, and the insoluble in the ionic state It cannot be adsorbed on tannins. The amount of radioactive element adsorbed on the insoluble tannin changes depending on the iron concentration in the waste liquid, but the molar concentration ratio of iron and the radioactive element in the waste liquid is 5: 1.
If below, when the pH is neutralized to about 4 to 6,
The insoluble tannin adsorbs almost 90% of the radioactive element in the waste liquid, and can suppress the concentration of iron accompanying the adsorbed radioactive element to several percent or less. At this time, 90
% Or more migrates into the residual liquid, but the migration rate of the radioactive element is reduced to several percent to about 10%.
【０００９】鉄のコロイドを生成した放射性廃液に添加
する粒状の不溶性タンニンとしては、特開平５−６６２
９１号公報及び特開平５−１７７１３５号公報に示され
る不溶性タンニンが挙げられる。前者の不溶性タンニン
は、アルカリ水溶液に縮合型タンニン粉末を溶解し、こ
の溶液にアルデヒド水溶液を混合してゲル状組成物を生
成し、このゲル状組成物を室温下で熟成、又は加熱して
安定化することにより作られる。後者の不溶性タンニン
は、加水分解型不溶性タンニンであって、アンモニア水
に加水分解型タンニン粉末を溶解し、この溶液にアルデ
ヒド水溶液を混合して沈殿物を生成し、この沈殿物を加
熱し、この加熱した沈殿物を硝酸のような鉱酸に浸漬し
た後、濾過することにより作られる。「不溶性タンニ
ン」とは、水、酸又はアルカリのいずれに対しても溶解
しないタンニンを意味する。この不溶性タンニンは粒径
が好ましくは０．５ｍｍ以上のものが選ばれる。放射性
元素を吸着した不溶性タンニンを廃液から分離する方法
としては、ステンレス製のスクリーンが採用され、スク
リーンの目開は、不溶性タンニンのみ通過不能な目開を
有するものである。不溶性タンニンの粒径が０．５ｍｍ
以上であれば、目開が０．２〜０．３ｍｍ程度のスクリ
ーンが選ばれる。弱酸性領域の鉄のコロイドは凝集効果
が進んでいないので、この目開のスクリーンでは鉄のコ
ロイドは容易に通過してしまう。As the particulate insoluble tannin to be added to the radioactive waste liquid in which an iron colloid has been formed, JP-A-5-662 describes
No. 91 and JP-A-5-177135. The former insoluble tannin is prepared by dissolving condensed tannin powder in an aqueous alkali solution, mixing this solution with an aqueous aldehyde solution to form a gel composition, and aging or heating the gel composition at room temperature or stable. It is made by conversion. The latter insoluble tannin is a hydrolyzable insoluble tannin, in which a hydrolyzable tannin powder is dissolved in aqueous ammonia, an aldehyde aqueous solution is mixed with this solution to generate a precipitate, and the precipitate is heated. It is made by immersing the heated precipitate in a mineral acid such as nitric acid and then filtering. "Insoluble tannin" means a tannin that is insoluble in any of water, acid or alkali. The insoluble tannin having a particle size of preferably 0.5 mm or more is selected. As a method for separating the insoluble tannin adsorbing the radioactive element from the waste liquid, a stainless steel screen is adopted, and the screen has openings that only the insoluble tannin cannot pass. Particle size of insoluble tannin is 0.5mm
If this is the case, a screen having an opening of about 0.2 to 0.3 mm is selected. Since the agglomeration effect of iron colloid in the weakly acidic region has not progressed, the iron colloid easily passes through this opening screen.
【００１０】更に不溶性タンニンを分離した放射性廃液
にアルカリ水溶液を添加して廃液に含まれている鉄を凝
集沈殿させる。即ち不溶性タンニンを分離した後の放射
性廃液には鉄がコロイド状態で含まれているが、この廃
液にＮａＯＨ、アンモニア水等の水溶液を添加混合して
ｐＨを更にアルカリ側に移行させれば、大部分の鉄元素
が水酸化鉄として凝集沈殿する。この廃液をろ過して固
液分離する。分離された固体（沈殿物）の放射能濃度は
低減されているため、この固体の処分費用は軽減するこ
とができる。またろ液の放射能濃度が核燃料加工施設の
排水管理基準以下であれば、そのまま施設外に排出し、
排水管理基準を超えている場合には、排水管理基準以下
になるまで更に二次処理を行う。一方、廃液から分離さ
れた、放射性元素を吸着した不溶性タンニンは乾燥した
後、６００℃以上に加熱して燃焼する。この燃焼により
不溶性タンニンは焼失し、放射性元素は酸化物として残
存する。放射性元素がウランの場合、ウラン酸化物（Ｕ
3Ｏ8）を硝酸に溶解してｐＨ１〜２の液にした後、この
液に過酸化水素水を加えてウランを過酸化ウランとして
沈殿させる。この液を固液分離することにより、純度の
高い過酸化ウランを回収することができ、ウラン資源の
再利用を図ることができる。Further, an aqueous alkali solution is added to the radioactive waste liquid from which the insoluble tannin has been separated to coagulate and precipitate the iron contained in the waste liquid. That is, the radioactive waste liquid after the separation of the insoluble tannin contains iron in a colloidal state. However, if the waste liquid is mixed with an aqueous solution such as NaOH or ammonia water and the pH is further shifted to the alkaline side, it becomes large. Part of the iron element coagulates and precipitates as iron hydroxide. This waste liquid is filtered to be separated into solid and liquid. Since the radioactivity concentration of the separated solid (precipitate) is reduced, the disposal cost of this solid can be reduced. Also, if the radioactivity concentration of the filtrate is below the wastewater management standard of the nuclear fuel processing facility, it is discharged out of the facility as it is,
If the wastewater management standard is exceeded, further secondary treatment is performed until the wastewater management standard is reached. On the other hand, the insoluble tannin adsorbed with a radioactive element, separated from the waste liquid, is dried and then heated to 600 ° C. or more and burned. The insoluble tannin is burned off by this combustion, and the radioactive element remains as an oxide. When the radioactive element is uranium, uranium oxide (U
3 O 8 ) is dissolved in nitric acid to obtain a liquid having a pH of 1 to 2, and then aqueous hydrogen peroxide is added to the liquid to precipitate uranium as uranium peroxide. By separating this liquid into solid and liquid, uranium peroxide with high purity can be recovered, and uranium resources can be reused.
【００１１】[0011]
【実施例】次に本発明の実施例を図面に基づいて説明す
る。 ＜実施例１〜１０＞硝酸ウラニルの水溶液に硝酸鉄を添
加して、ウラン濃度が５００ｐｐｍ、鉄の濃度が１００
ｐｐｍ、硝酸濃度が１．２Ｎの模擬の放射性廃液２００
０ｍｌを準備した。この模擬廃液の鉄とウランのモル比
は、Ｆｅ：Ｕ＝０．８５：１であった。この廃液を１０
等分し、それぞれにアンモニア水を添加混合し、ｐＨを
２．５（実施例１）、３．０（実施例２）、３．５（実
施例３）、４．０（実施例４）、４．５（実施例５）、
５．０（実施例６）、５．５（実施例７）、６．０（実
施例８）、７．０（実施例９）及び８．０（実施例１
０）に調整した。この濃度ではｐＨ＝３．５以上になる
と、明らかな鉄コロイドが発生した。これらの液に粒径
が０．５ｍｍ以上の特開平５−６６２９１号公報に示さ
れる不溶性タンニンを模擬廃液２００ｍｌに対して４０
ｍｇの割合で添加して２時間攪拌した。Next, an embodiment of the present invention will be described with reference to the drawings. <Examples 1 to 10> Iron nitrate was added to an aqueous solution of uranyl nitrate so that the uranium concentration was 500 ppm and the iron concentration was 100.
Simulated radioactive effluent 200 ppm, nitric acid concentration 1.2N
0 ml was prepared. The molar ratio of iron to uranium in this simulated waste liquid was Fe: U = 0.85: 1. This waste liquid is
The mixture was equally divided, and aqueous ammonia was added to each and mixed to adjust the pH to 2.5 (Example 1), 3.0 (Example 2), 3.5 (Example 3), and 4.0 (Example 4). 4.5 (Example 5),
5.0 (Example 6), 5.5 (Example 7), 6.0 (Example 8), 7.0 (Example 9) and 8.0 (Example 1)
Adjusted to 0). At this concentration, when the pH became 3.5 or more, a clear iron colloid was generated. Insoluble tannin having a particle size of 0.5 mm or more described in Japanese Patent Application Laid-Open No. 5-66291 is added to these simulated liquids in an amount of 40 ml per 200 ml of the simulated waste liquid.
mg and stirred for 2 hours.
【００１２】＜実施例１１〜２０＞鉄の濃度を５００ｐ
ｐｍにした以外、実施例１〜１０と同様にして模擬の放
射性廃液２０００ｍｌを準備した。この模擬廃液の鉄と
ウランのモル比は、Ｆｅ：Ｕ＝４．２７：１であった。
この廃液を１０等分し、それぞれにアンモニア水を添加
混合し、ｐＨを２．５（実施例１１）、３．０（実施例
１２）、３．５（実施例１３）、４．０（実施例１
４）、４．５（実施例１５）、５．０（実施例１６）、
５．５（実施例１７）、６．０（実施例１８）、７．０
（実施例１９）及び８．０（実施例２０）に調整した。
この濃度では１０種類の液すべてに鉄のコロイドが生成
した。これらの液に実施例１〜１０と同一の不溶性タン
ニンを模擬廃液２００ｍｌに対して４０ｍｇの割合で添
加して２時間攪拌した。<Examples 11 to 20> The iron concentration was set to 500 p.
2,000 ml of a simulated radioactive waste liquid was prepared in the same manner as in Examples 1 to 10 except that the pm was changed to pm. The molar ratio of iron to uranium in this simulated waste liquid was Fe: U = 4.27: 1.
This waste liquid is divided into 10 equal parts, and ammonia water is added to each and mixed to adjust the pH to 2.5 (Example 11), 3.0 (Example 12), 3.5 (Example 13), 4.0 (Example 13). Example 1
4) 4.5 (Example 15), 5.0 (Example 16),
5.5 (Example 17), 6.0 (Example 18), 7.0
(Example 19) and 8.0 (Example 20).
At this concentration, iron colloids were formed in all ten liquids. The same insoluble tannin as in Examples 1 to 10 was added to these liquids at a ratio of 40 mg to 200 ml of the simulated waste liquid, followed by stirring for 2 hours.
【００１３】＜実施例２１〜３０＞鉄の濃度を１０００
ｐｐｍにした以外、実施例１〜１０と同様にして模擬の
放射性廃液２０００ｍｌを準備した。この模擬廃液の鉄
とウランのモル比は、Ｆｅ：Ｕ＝８．５２：１であっ
た。この廃液を１０等分し、それぞれにアンモニア水を
添加混合し、ｐＨを２．５（実施例２１）、３．０（実
施例２２）、３．５（実施例２３）、４．０（実施例２
４）、４．５（実施例２５）、５．０（実施例２６）、
５．５（実施例２７）、６．０（実施例２８）、７．０
（実施例２９）及び８．０（実施例３０）に調整した。
１０種類の液すべてに鉄のコロイドが生成した。これら
の液に実施例１〜１０と同一の不溶性タンニンを模擬廃
液２００ｍｌに対して４０ｍｇの割合で添加して２時間
攪拌した。<Examples 21 to 30> The iron concentration was set to 1000
A simulated radioactive waste liquid of 2000 ml was prepared in the same manner as in Examples 1 to 10 except that the concentration was set to ppm. The molar ratio of iron to uranium in this simulated waste liquid was Fe: U = 8.52: 1. This waste liquid was divided into 10 equal parts, and ammonia water was added to each and mixed to adjust the pH to 2.5 (Example 21), 3.0 (Example 22), 3.5 (Example 23), 4.0 (Example 23). Example 2
4) 4.5 (Example 25), 5.0 (Example 26),
5.5 (Example 27), 6.0 (Example 28), 7.0
(Example 29) and 8.0 (Example 30).
Iron colloids were formed in all ten liquids. The same insoluble tannin as in Examples 1 to 10 was added to these liquids at a ratio of 40 mg to 200 ml of the simulated waste liquid, followed by stirring for 2 hours.
【００１４】＜実施例３１〜４０＞鉄の濃度を５０００
ｐｐｍにした以外、実施例１〜１０と同様にして模擬の
放射性廃液２０００ｍｌを準備した。この模擬廃液の鉄
とウランのモル比は、Ｆｅ：Ｕ＝４２．７：１であっ
た。この廃液を１０等分し、それぞれにアンモニア水を
添加混合し、ｐＨを２．５（実施例３１）、３．０（実
施例３２）、３．５（実施例３３）、４．０（実施例３
４）、４．５（実施例３５）、５．０（実施例３６）、
５．５（実施例３７）、６．０（実施例３８）、７．０
（実施例３９）及び８．０（実施例４０）に調整した。
１０種類の液すべてに鉄のコロイドが生成した。これら
の液に実施例１〜１０と同一の不溶性タンニンを模擬廃
液２００ｍｌに対して４０ｍｇの割合で添加して２時間
攪拌した。<Examples 31 to 40> The iron concentration was set to 5000
A simulated radioactive waste liquid of 2000 ml was prepared in the same manner as in Examples 1 to 10 except that the concentration was set to ppm. The molar ratio of iron to uranium in this simulated waste liquid was Fe: U = 42.7: 1. This waste liquid was divided into 10 equal parts, and aqueous ammonia was added to each and mixed to adjust the pH to 2.5 (Example 31), 3.0 (Example 32), 3.5 (Example 33), 4.0 (Example 33). Example 3
4) 4.5 (Example 35), 5.0 (Example 36),
5.5 (Example 37), 6.0 (Example 38), 7.0
(Example 39) and 8.0 (Example 40).
Iron colloids were formed in all ten liquids. The same insoluble tannin as in Examples 1 to 10 was added to these liquids at a ratio of 40 mg to 200 ml of the simulated waste liquid, followed by stirring for 2 hours.
【００１５】＜実施例４１〜５０＞鉄の濃度を１０００
０ｐｐｍにした以外、実施例１〜１０と同様にして模擬
の放射性廃液２０００ｍｌを準備した。この模擬廃液の
鉄とウランのモル比は、Ｆｅ：Ｕ＝８５．２：１であっ
た。この廃液を１０等分し、それぞれにアンモニア水を
添加混合し、ｐＨを２．５（実施例４１）、３．０（実
施例４２）、３．５（実施例４３）、４．０（実施例４
４）、４．５（実施例４５）、５．０（実施例４６）、
５．５（実施例４７）、６．０（実施例４８）、７．０
（実施例４９）及び８．０（実施例５０）に調整した。
１０種類の液すべてに鉄のコロイドが生成した。これら
の液に実施例１〜１０と同一の不溶性タンニンを模擬廃
液２００ｍｌに対して４０ｍｇの割合で添加して２時間
攪拌した。<Examples 41 to 50> The iron concentration was set to 1000
A simulated radioactive waste liquid of 2,000 ml was prepared in the same manner as in Examples 1 to 10, except that the amount was set to 0 ppm. The molar ratio of iron to uranium in this simulated waste liquid was Fe: U = 85.2: 1. This waste liquid is divided into 10 equal parts, and ammonia water is added and mixed to each, and the pH is adjusted to 2.5 (Example 41), 3.0 (Example 42), 3.5 (Example 43), 4.0 (Example 43). Example 4
4) 4.5 (Example 45), 5.0 (Example 46),
5.5 (Example 47), 6.0 (Example 48), 7.0
(Example 49) and 8.0 (Example 50).
Iron colloids were formed in all ten liquids. The same insoluble tannin as in Examples 1 to 10 was added to these liquids at a ratio of 40 mg to 200 ml of the simulated waste liquid, followed by stirring for 2 hours.
【００１６】＜比較評価＞実施例１〜５０の不溶性タン
ニン添加液を、最初にNo.６のろ紙を用いて鉄コロイド
と不溶性タンニンをろ別した。次に目開０．２〜０．３
ｍｍのスクリーンを用いて不溶性タンニンと鉄コロイド
を分別し、不溶性タンニン、鉄コロイド、ろ液中のウラ
ン分配率を求めた。上記分配率のうち不溶性タンニンへ
のウラン分配率を図１に示す。また回収した不溶性タン
ニンを燃焼して得られた酸化物（Ｕ3Ｏ8）中のウランの
純度を図２に示す。図１から明らかなように、ｐＨの低
い酸性領域或いは中性以上の領域においてウランの回収
率が悪くなる傾向がみられる。これに対して、弱酸性領
域、特に鉄の濃度が低い実施例３〜７，１３〜１６に於
いてはウランを９５％以上回収できることが判った。ま
た図２から明らかなように、回収された酸化物中のウラ
ン純度も鉄の濃度が１００ｐｐｍ（実施例３〜１０），
５００ｐｐｍ（実施例１５〜２０）では９０％程度の高
い値を示した。<Comparative Evaluation> The insoluble tannin-added liquids of Examples 1 to 50 were first filtered using a No. 6 filter paper to separate iron colloid and insoluble tannin. Next, eye opening 0.2-0.3
The insoluble tannin and iron colloid were separated using a screen of mm, and the uranium partition ratio in the insoluble tannin, iron colloid and filtrate was determined. FIG. 1 shows the uranium distribution ratio to insoluble tannin among the above distribution ratios. FIG. 2 shows the purity of uranium in the oxide (U 3 O 8 ) obtained by burning the recovered insoluble tannin. As is clear from FIG. 1, there is a tendency that the recovery rate of uranium is deteriorated in an acidic region having a low pH or a region having a neutral pH or higher. On the other hand, it was found that uranium could be recovered in an amount of 95% or more in the weakly acidic region, particularly in Examples 3 to 7 and 13 to 16 in which the iron concentration was low. As is clear from FIG. 2, the uranium purity in the recovered oxide was 100 ppm in iron concentration (Examples 3 to 10),
At 500 ppm (Examples 15 to 20), a high value of about 90% was shown.
【００１７】[0017]
【発明の効果】以上述べたように、従来、ウランを初め
として殆どの放射性元素が凝集沈殿物として放射性固体
廃棄物へ移行して処分費用を高めていたのに対して、本
発明の除染方法によれば、鉄コロイドの廃液に不溶性タ
ンニンを添加して、不溶性タンニンに放射性元素を吸着
させることにより、廃液の放射能濃度を低減し、この廃
液の二次処理を不要とするか、或いは二次処理への負荷
を軽減することができる。また不溶性タンニンにより放
射性元素を吸着した後の廃液から生じた放射性固体廃棄
物の放射性能度を低減するため、この放射性固体廃棄物
の処分費用を低減することができる。また不溶性タンニ
ンを燃焼することにより回収されたウラン等の放射性元
素は比較的純度が高いため、過酸化ウラン沈殿法などの
比較的簡便かつ経済的な方法で精製処理することがで
き、ウラン等の核燃料資源の再利用を図ることもでき
る。As described above, conventionally, most of the radioactive elements including uranium have been transferred to radioactive solid waste as coagulated sediment to increase the disposal cost. According to the method, the insoluble tannin is added to the waste liquid of the iron colloid, and the radioactive element is adsorbed on the insoluble tannin, thereby reducing the radioactive concentration of the waste liquid and eliminating the need for secondary treatment of the waste liquid, or The load on the secondary processing can be reduced. Further, since the radiation performance of the radioactive solid waste generated from the waste liquid after the radioactive element is adsorbed by the insoluble tannin is reduced, the disposal cost of the radioactive solid waste can be reduced. In addition, since radioactive elements such as uranium recovered by burning insoluble tannin are relatively high in purity, they can be purified by a relatively simple and economical method such as uranium peroxide precipitation, and can be purified. Nuclear fuel resources can also be reused.
【図１】実施例の不溶性タンニンへのウラン回収率を示
す図。FIG. 1 is a view showing the uranium recovery rate to insoluble tannin in Examples.
【図２】実施例の不溶性タンニン燃焼後の酸化物中のウ
ラン純度を示す図。FIG. 2 is a graph showing uranium purity in oxides after burning insoluble tannins in Examples.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 中村 康雄 茨城県那珂郡東海村大字舟石川622番地１ 三菱原子燃料株式会社内 Ｆターム(参考） 4D024 AA04 AA08 AA09 AB10 AB17 BA16 BA19 BB01 DB03 DB20 DB21 4G066 AB06B AB29B BA09 BA20 CA12 CA45 CA49 DA08 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasuo Nakamura 622-1, Funaishikawa, Tokai-mura, Naka-gun, Ibaraki Prefecture F-term in Mitsubishi Nuclear Fuel Co., Ltd. 4D024 AA04 AA08 AA09 AB10 AB17 BA16 BA19 BB01 DB03 DB20 DB21 4G066 AB06B AB29B BA09 BA20 CA12 CA45 CA49 DA08
Claims (2)
いる強酸性の放射性廃液にアルカリ水溶液を添加混合し
て前記廃液を弱酸性にすることにより鉄のコロイドを生
成する工程と、 (b) 前記鉄のコロイドを生成した放射性廃液に粒状の不
溶性タンニンを添加混合する工程と、 (c) 前記不溶性タンニンを前記廃液から分離する工程と
を含む放射性廃液の除染方法。(A) a step of adding an alkaline aqueous solution to a strongly acidic radioactive waste liquid in which a radioactive element and iron are mainly dissolved to mix and weaken the waste liquid to produce an iron colloid; b) A method for decontaminating radioactive waste liquid, comprising: a step of adding and mixing granular insoluble tannin to the radioactive waste liquid having produced the iron colloid; and (c) a step of separating the insoluble tannin from the waste liquid.
ルカリ水溶液を添加混合して前記廃液に含まれる鉄を凝
集沈殿させる工程と、 (e) 前記鉄を凝集沈殿させた廃液を固液分離する工程と
を更に含む請求項１又は２記載の放射性廃液の除染方
法。2. A step of adding and mixing an aqueous alkali solution to the waste liquid from which the insoluble tannin has been separated to coagulate and precipitate the iron contained in the waste liquid; and (e) a solid-liquid separation of the waste liquid obtained by coagulating and precipitating the iron. 3. The method for decontaminating radioactive waste liquid according to claim 1, further comprising the step of:
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Cited By (5)
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|---|---|---|---|---|
| JP2014077781A (en) * | 2012-10-08 | 2014-05-01 | Korea Atomic Energy Research Inst | Treatment method of spent uranium catalyst |
| CN105006263A (en) * | 2015-06-19 | 2015-10-28 | 华东理工大学 | Method for treating nuclear power plant radioactive liquid waste by generating manganous-manganic oxide in situ |
| CN110268481A (en) * | 2017-02-09 | 2019-09-20 | 水野実 | The method for reducing the amount of the radiant of liquid body |
| CN116282611A (en) * | 2021-12-17 | 2023-06-23 | 昆明理工大学 | Method for treating industrial high-salt uranium-containing wastewater |
| CN116354314A (en) * | 2021-12-27 | 2023-06-30 | 核工业北京化工冶金研究院 | Method for improving nitric acid solubility of uranium peroxide product |
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1999
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014077781A (en) * | 2012-10-08 | 2014-05-01 | Korea Atomic Energy Research Inst | Treatment method of spent uranium catalyst |
| CN105006263A (en) * | 2015-06-19 | 2015-10-28 | 华东理工大学 | Method for treating nuclear power plant radioactive liquid waste by generating manganous-manganic oxide in situ |
| CN110268481A (en) * | 2017-02-09 | 2019-09-20 | 水野実 | The method for reducing the amount of the radiant of liquid body |
| CN116282611A (en) * | 2021-12-17 | 2023-06-23 | 昆明理工大学 | Method for treating industrial high-salt uranium-containing wastewater |
| CN116282611B (en) * | 2021-12-17 | 2024-05-14 | 昆明理工大学 | Method for treating industrial high-salt uranium-containing wastewater |
| CN116354314A (en) * | 2021-12-27 | 2023-06-30 | 核工业北京化工冶金研究院 | Method for improving nitric acid solubility of uranium peroxide product |
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