JP4225659B2 - Decontamination method of radioactive liquid waste - Google Patents
Decontamination method of radioactive liquid waste Download PDFInfo
- Publication number
- JP4225659B2 JP4225659B2 JP36021799A JP36021799A JP4225659B2 JP 4225659 B2 JP4225659 B2 JP 4225659B2 JP 36021799 A JP36021799 A JP 36021799A JP 36021799 A JP36021799 A JP 36021799A JP 4225659 B2 JP4225659 B2 JP 4225659B2
- Authority
- JP
- Japan
- Prior art keywords
- radioactive
- waste
- iron
- liquid
- waste liquid
- 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.)
- Expired - Lifetime
Links
Images
Landscapes
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Water Treatment By Sorption (AREA)
Description
【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。
【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。
【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。
【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。
【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。
【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。
【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。
【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。
【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５−６６２９１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。
【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（Ｕ3Ｏ8）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。
【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１００ｐｐｍ、硝酸濃度が１．２Ｎの模擬の放射性廃液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＝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１０）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４０ｍｇの割合で添加して２時間攪拌した。
【００１２】
＜実施例１１〜２０＞
鉄の濃度を５００ｐｐｍ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１４）、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。
【００１３】
＜実施例２１〜３０＞
鉄の濃度を１０００ｐｐｍ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２４）、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。
【００１４】
＜実施例３１〜４０＞
鉄の濃度を５０００ｐｐｍ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３４）、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。
【００１５】
＜実施例４１〜５０＞
鉄の濃度を１００００ｐｐｍ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４４）、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。
【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０．２〜０．３ｍｍ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。
【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。
【図面の簡単な説明】
【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。
【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。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for decontaminating radioactive liquid waste, which removes the radioactive element from a strongly acidic radioactive liquid waste in which mainly radioactive elements such as uranium and iron are dissolved. More particularly, the present invention relates to a decontamination method for reducing each radioactive concentration of waste liquid and radioactive solid waste generated from the waste liquid.
[0002]
[Prior art]
In general, in nuclear fuel processing facilities mainly using uranium and nuclear fuel reprocessing facilities using plutonium, radioactive elements such as uranium adhering to the equipment surface and inside the piping are dissolved with mineral acids such as nitric acid and sulfuric acid. In this way, radioactive elements are decontaminated. 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 recovered, the waste liquid is generally treated by a coagulation precipitation 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. After this process, a radioactive element such as uranium and iron are coagulated and precipitated by a coprecipitation phenomenon. The aggregated sediment is separated into solid and liquid to reduce the radioactive concentration of the waste liquid. Then, if necessary, secondary treatment by evaporative distillation or ion exchange is performed to bring the radioactive concentration below the wastewater management standard, and then the waste liquid is discharged outside the facility. The aggregated precipitate generated at this time is dried and then handled as radioactive solid waste having a relatively high radioactivity concentration.
In the primary treatment, for the purpose of reducing the load in the secondary treatment, the pH value is increased to the alkali side, or an agglomeration aid is added to enhance the agglomeration effect. For this reason, the transfer rate of radioactive elements such as uranium into the aggregated precipitate generated by the primary treatment is high.
On the other hand, according to the radioactive concentration of radioactive solid waste and the amount of long-lived nuclides, separate disposal of waste, whether to dispose of radioactive solid waste in a shallow underground layer or in a deep layer, has recently been studied. Has been. Therefore, when considering the transport of radioactive solid waste to the buried facility and the final disposal form, the rate of transfer of radioactive elements such as uranium into the radioactive solid waste is reduced as much as possible economically. It is desirable to keep it.
[0003]
[Problems to be solved by the invention]
However, although the concentration of radioactive elements such as uranium in the waste liquid can be reduced by the conventional coagulation sedimentation method, there is a problem that the radioactive concentration of radioactive solid waste that is coagulation sediment is high and the disposal cost of waste is high. .
In addition, it has been difficult to recover and reuse radioactive elements such as uranium in the waste liquid.
[0004]
The objective of this invention is providing the decontamination method of the radioactive waste liquid which can reduce the radioactive concentration of a waste liquid.
Another object of the present invention is to provide a method for decontaminating radioactive liquid waste that can reduce the radioactive concentration of radioactive solid waste produced from the liquid waste.
[0005]
[Means for Solving the Problems]
The invention according to
When neutralizing a weakly acidic radioactive liquid waste containing radioactive elements and iron to make it weakly acidic, most of the iron ions become colloidal and float in the liquid, and some of the radioactive elements colloid due to the cohesive force of iron. Most of them are present in the liquid as radioactive ions. When particulate insoluble tannin is added to and mixed with the waste liquid in this state, the insoluble tannin adsorbs radioactive ions. By separating insoluble tannin from the waste liquid, the radioactive concentration of the waste liquid can be reduced.
[0006]
The invention according to
Since the radioactivity concentration of the waste liquid from which insoluble tannin has been separated is low, the radioactivity concentration of the aggregated precipitate of this waste liquid is also low.
[0007]
DETAILED DESCRIPTION OF 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 mainly radioactive elements and iron are dissolved. To illustrate this waste liquid, waste liquid produced when wet decontamination such as washing or electrification decontamination with nitric acid or sulfuric acid is performed on iron equipment or piping in nuclear fuel processing facilities or nuclear fuel reprocessing facilities, or iron The waste liquid generated when acid decontamination is performed for the purpose of removing surface contamination when disassembling the equipment itself. Examples of radioactive elements include actinide elements such as uranium, thorium, and transuranium elements (neptunium, plutonium, americium, curium).
[0008]
Examples of the aqueous alkaline solution added to the waste liquid include aqueous solutions such as NaOH and aqueous ammonia. The amount of the alkaline aqueous solution added to the radioactive liquid waste is an area where the pH value of the strongly acidic radioactive liquid waste is suitable for adsorption of the insoluble tannin to the radioactive element, and is preferably an amount that makes the pH 3 or more, and iron is added. This is the amount of colloid from the ionic state by neutralization with an aqueous alkali solution. Specifically, an amount in which iron is hydrolyzed and the iron ion concentration is reduced to 1/100 or less is preferable, and a weakly acidic region having a pH of less than 7 is preferable at most.
When the addition amount of the alkaline aqueous solution is less than the above amount, iron colloid is not sufficiently generated, and ionic iron is adsorbed by insoluble tannin, so that the separation effect of iron and radioactive elements cannot be expected. When the amount of the alkaline aqueous solution added is larger than the above amount, the agglomeration effect of the iron colloid is promoted, and a starch is formed together with the radioactive element, and the radioactive element itself is further hydrolyzed and is insoluble in an ionic state. Unable to adsorb to tannin.
Depending on the concentration of iron in the waste liquid, the amount of insoluble tannin adsorbed on the radioactive element varies, but if the molar concentration ratio of iron and radioactive element in the waste liquid is 5 to 1 or less, the pH is reduced to about 4-6. When neutralized, the insoluble tannin adsorbs nearly 90% of the radioactive element in the waste liquid, and the iron concentration accompanying the adsorbed radioactive element can be suppressed to several% or less. At this time, 90% or more of iron is transferred into the residual liquid, but the transfer rate of radioactive elements is reduced to about several to 10%.
[0009]
Examples of the particulate insoluble tannin added to the radioactive liquid waste produced with the iron colloid include insoluble tannin disclosed in JP-A-5-66291 and JP-A-5-177135. The former insoluble tannin is obtained by dissolving a condensed tannin powder in an alkaline aqueous solution and mixing this solution with an aldehyde aqueous solution to form a gel-like composition. The gel-like composition is aged at room temperature or stable by heating. It is made by making. The latter insoluble tannin is a hydrolyzable insoluble tannin, which is obtained by dissolving hydrolyzable tannin powder in aqueous ammonia, mixing an aqueous aldehyde solution with this solution to form a precipitate, heating the precipitate, It is made by immersing the heated precipitate in a mineral acid such as nitric acid and then filtering. “Insoluble tannin” means tannin that does not dissolve 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 employed, and the screen has a mesh that cannot pass only insoluble tannin. If the particle size of insoluble tannin is 0.5 mm or more, a screen having a mesh size of about 0.2 to 0.3 mm is selected. Since the colloidal effect of the iron colloid in the weakly acidic region has not progressed, the iron colloid easily passes through this screen.
[0010]
Further, an aqueous alkaline solution is added to the radioactive waste liquid from which the insoluble tannin has been separated to agglomerate and precipitate iron contained in the waste liquid. In other words, the radioactive waste liquid after separation of insoluble tannin contains iron in a colloidal state. However, if the aqueous solution such as NaOH and aqueous ammonia is added to and mixed with this waste liquid, the pH is further shifted to the alkali side. Part of the iron element coagulates and precipitates as iron hydroxide. This waste liquid is filtered and solid-liquid separated. Since the radioactive concentration of the separated solid (precipitate) is reduced, the disposal cost of this solid can be reduced. If the radioactive concentration of the filtrate is below the wastewater management standard for nuclear fuel processing facilities, it is discharged outside the facility, and if it exceeds the wastewater management standard, further secondary treatment is performed until it falls below the wastewater management standard. Do.
On the other hand, the insoluble tannin adsorbed with the radioactive element separated from the waste liquid is dried and then heated to 600 ° C. or more to burn. This combustion burns away insoluble tannins, leaving radioactive elements as oxides. 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 hydrogen peroxide is added to the liquid to precipitate uranium as uranium peroxide. By separating this liquid into solid and liquid, highly purified uranium peroxide can be recovered, and uranium resources can be reused.
[0011]
【Example】
Next, embodiments 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 to prepare 2000 ml of a simulated radioactive liquid waste having a uranium concentration of 500 ppm, an iron concentration of 100 ppm, and a nitric acid concentration of 1.2 N. The molar ratio of iron and uranium in this simulated waste liquid was Fe: U = 0.85: 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 1), 3.0 (Example 2), 3.5 (Example 3), 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 Adjusted to 8.0 (Example 10). At this concentration, a clear iron colloid was generated when pH = 3.5 or more.
Insoluble tannin shown in JP-A-5-66291 having a particle size of 0.5 mm or more was added to these liquids at a ratio of 40 mg to 200 ml of simulated waste liquid and stirred for 2 hours.
[0012]
<Examples 11 to 20>
A simulated radioactive liquid waste 2000 ml was prepared in the same manner as in Examples 1 to 10 except that the iron concentration was 500 ppm. The molar ratio of iron and 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 and mixed to each, and the pH is adjusted to 2.5 (Example 11), 3.0 (Example 12), 3.5 (Example 13), 4.0 ( Examples 14), 4.5 (Example 15), 5.0 (Example 16), 5.5 (Example 17), 6.0 (Example 18), 7.0 (Example 19) and Adjusted to 8.0 (Example 20). At this concentration, iron colloids were formed in all 10 liquids.
To these liquids, the same insoluble tannin as in Examples 1 to 10 was added at a ratio of 40 mg to 200 ml of the simulated waste liquid and stirred for 2 hours.
[0013]
<Examples 21 to 30>
A simulated radioactive liquid waste 2000 ml was prepared in the same manner as in Examples 1 to 10 except that the iron concentration was 1000 ppm. The molar ratio of iron and uranium in this simulated waste liquid was Fe: U = 8.52: 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 21), 3.0 (Example 22), 3.5 (Example 23), 4.0 ( Examples 24), 4.5 (Example 25), 5.0 (Example 26), 5.5 (Example 27), 6.0 (Example 28), 7.0 (Example 29) and Adjusted to 8.0 (Example 30). Iron colloids were formed in all 10 liquids.
To these liquids, the same insoluble tannin as in Examples 1 to 10 was added at a ratio of 40 mg to 200 ml of the simulated waste liquid and stirred for 2 hours.
[0014]
<Examples 31 to 40>
A simulated radioactive liquid waste 2000 ml was prepared in the same manner as in Examples 1 to 10 except that the iron concentration was 5000 ppm. The molar ratio of iron and uranium in this simulated waste liquid was Fe: U = 42.7: 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 31), 3.0 (Example 32), 3.5 (Example 33), 4.0 ( Examples 34), 4.5 (Example 35), 5.0 (Example 36), 5.5 (Example 37), 6.0 (Example 38), 7.0 (Example 39) and Adjusted to 8.0 (Example 40). Iron colloids were formed in all 10 liquids.
To these liquids, the same insoluble tannin as in Examples 1 to 10 was added at a ratio of 40 mg to 200 ml of the simulated waste liquid and stirred for 2 hours.
[0015]
<Examples 41-50>
A simulated radioactive liquid waste 2000 ml was prepared in the same manner as in Examples 1 to 10 except that the iron concentration was 10,000 ppm. The molar ratio of iron and 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 ( Examples 44), 4.5 (Example 45), 5.0 (Example 46), 5.5 (Example 47), 6.0 (Example 48), 7.0 (Example 49) and Adjusted to 8.0 (Example 50). Iron colloids were formed in all 10 liquids.
To these liquids, the same insoluble tannin as in Examples 1 to 10 was added at a ratio of 40 mg to 200 ml of the simulated waste liquid and stirred for 2 hours.
[0016]
<Comparison evaluation>
The insoluble tannin-added solutions of Examples 1 to 50 were first filtered to separate iron colloid and insoluble tannin using No. 6 filter paper. Next, insoluble tannin and iron colloid were fractionated using a screen having a mesh size of 0.2 to 0.3 mm, and the uranium partition ratio in the insoluble tannin, iron colloid and filtrate was determined.
Of the above distribution rates, the uranium distribution rate to insoluble tannin is shown in FIG. FIG. 2 shows the purity of uranium in the oxide (U 3 O 8 ) obtained by burning the recovered insoluble tannin.
As is apparent from FIG. 1, the uranium recovery rate tends to deteriorate in an acidic region having a low pH or a neutral or higher region. On the other hand, it was found that 95% or more of uranium can be recovered in the weakly acidic region, particularly in Examples 3 to 7 and 13 to 16 where the iron concentration is low.
As is clear from FIG. 2, the uranium purity in the recovered oxide also showed a high value of about 90% when the iron concentration was 100 ppm (Examples 3 to 10) and 500 ppm (Examples 15 to 20). .
[0017]
【The invention's effect】
As described above, in the past, most radioactive elements including uranium have been transferred to radioactive solid waste as agglomerated precipitates to increase disposal costs, whereas according to the decontamination method of the present invention, By adding insoluble tannin to the waste liquid of iron colloid and adsorbing radioactive elements to the insoluble tannin, the radioactive concentration of the waste liquid is reduced, and the secondary treatment of this waste liquid is not required, or the secondary treatment The load can be reduced.
Moreover, since the radiation performance degree of the radioactive solid waste produced from the waste liquid after adsorbing the radioactive element with 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 have a relatively high purity, they can be purified by a relatively simple and economical method such as uranium peroxide precipitation. Nuclear fuel resources can also be reused.
[Brief description of the drawings]
FIG. 1 is a graph showing the uranium recovery rate to insoluble tannins in Examples.
FIG. 2 is a graph showing the uranium purity in the oxide after burning the insoluble tannin in the example.
Claims (2)
(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。generating a colloidal iron by (a) radioactive elements and iron to the waste liquid was added to and mixed with an aqueous alkali solution a strongly acidic radioactive liquid waste that dissolve in slightly acidic,
(b) adding and mixing granular insoluble tannin to the radioactive liquid waste that produced the iron colloid;
(c) separating the insoluble tannin from the waste liquid, and a method for decontaminating the radioactive liquid waste.
(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記載の放射性廃液の除染方法。(d) adding and mixing an alkaline aqueous solution to the waste liquid from which insoluble tannin has been separated to agglomerate and precipitate the iron contained in the waste liquid;
(e) decontamination method of radioactive liquid waste according to claim 1, further comprising a step of the to iron aggregation precipitated waste to solid-liquid separation was.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP36021799A JP4225659B2 (en) | 1999-12-20 | 1999-12-20 | Decontamination method of radioactive liquid waste |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP36021799A JP4225659B2 (en) | 1999-12-20 | 1999-12-20 | Decontamination method of radioactive liquid waste |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2001174587A JP2001174587A (en) | 2001-06-29 |
| JP4225659B2 true JP4225659B2 (en) | 2009-02-18 |
Family
ID=18468423
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP36021799A Expired - Lifetime JP4225659B2 (en) | 1999-12-20 | 1999-12-20 | Decontamination method of radioactive liquid waste |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP4225659B2 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101316925B1 (en) * | 2012-10-08 | 2013-10-18 | 한국수력원자력 주식회사 | Treatment method of spent uranium catalyst |
| CN105006263B (en) * | 2015-06-19 | 2017-11-03 | 华东理工大学 | A kind of method of in-situ preparation mangano-manganic oxide processing nuclear power plant radioactive liquid waste |
| SG11201907115TA (en) * | 2017-02-09 | 2019-09-27 | Minoru Mizuno | Method for reducing amount of radioactivity of liquid |
| CN116282611B (en) * | 2021-12-17 | 2024-05-14 | 昆明理工大学 | Method for treating industrial high-salt uranium-containing wastewater |
| CN116354314B (en) * | 2021-12-27 | 2024-10-18 | 核工业北京化工冶金研究院 | Method for improving nitric acid solubility of uranium peroxide product |
-
1999
- 1999-12-20 JP JP36021799A patent/JP4225659B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JP2001174587A (en) | 2001-06-29 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JPS60636B2 (en) | Treatment method for radioactive waste liquid | |
| JP2014077774A (en) | Method for separating and removing radioactive cesium from discharge water and stably storing the same | |
| JP2000512759A (en) | Method for removing cesium from radioactive liquid waste and method for producing hexacyanoferrate | |
| JP6327782B2 (en) | Method for removing radioactive cesium from wastewater containing radioactive cesium | |
| JP6173396B2 (en) | Method and apparatus for treating radioactive liquid waste generated during a major nuclear accident | |
| JP4225659B2 (en) | Decontamination method of radioactive liquid waste | |
| US4349513A (en) | Process for recovering uranium and/or thorium from a liquid containing uranium and/or thorium | |
| JPS62266499A (en) | Method of processing radioactive waste liquor | |
| CN102930914A (en) | Processing method of radioactive waste liquid containing uranium | |
| CN111087114A (en) | Treatment method of tantalum-niobium production wastewater | |
| EP0454028B1 (en) | Waste treatment process for alkaline waste liquid | |
| JP2001239138A (en) | Device for treating liquid | |
| McGinnis et al. | Caustic leaching of high-level radioactive tank sludge: a critical literature review | |
| JPS58223798A (en) | Method of processing concentrated salt liquid waste containing radioactive material | |
| WO2002013202A1 (en) | Oil scale volume reduction | |
| JPH06130188A (en) | Processing method for radioactive waste liquid | |
| JP2938287B2 (en) | Treatment of radioactive liquid waste | |
| JP3143839B2 (en) | Treatment of radioactive liquid waste | |
| JPS62176913A (en) | Process for separation and recovery of cesium from treating liquid containing sodium salt | |
| JPH0326999A (en) | Disposal of waste containing radioactive organic matter | |
| JPH0720285A (en) | Removing method of underwater radioactive substance | |
| JP2561909B2 (en) | Treatment method of radioactive liquid waste | |
| US20080142448A1 (en) | Treatment of metal-containing liquids | |
| JPH04260495A (en) | Separation of transition metal in solution | |
| JPS642917B2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20061025 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20080326 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20080909 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20081028 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20081125 |
|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20081125 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20111205 Year of fee payment: 3 |
|
| R150 | Certificate of patent or registration of utility model |
Ref document number: 4225659 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20111205 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20121205 Year of fee payment: 4 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20121205 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20131205 Year of fee payment: 5 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| EXPY | Cancellation because of completion of term |