JP2013190257A - Immobilizing material for radioactive substance and processing method of radioactive contaminant - Google Patents
Immobilizing material for radioactive substance and processing method of radioactive contaminant Download PDFInfo
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本発明は、放射性セシウム等の放射性物質を固定化できる材料と、該材料を用いて放射性汚染物、特に低レベルの放射性汚染物を処理する方法に関する。
ここで、低レベルの放射性汚染物とは、使用済み核燃料の再処理操作で分離された放射性廃液やそのガラス固化体等の高レベル放射性廃棄物を除いたものをいい、例えば、放射性物質を含む、土壌（以下「汚染土」という。）、灰（以下「汚染灰」という。）、およびダスト（以下「汚染ダスト」という。）などの放射性汚染物が挙げられる。
The present invention relates to a material capable of immobilizing a radioactive substance such as radioactive cesium and a method of treating radioactive contaminants, particularly low-level radioactive contaminants, using the material.
Here, the low-level radioactive contaminants are those excluding high-level radioactive wastes such as radioactive liquid waste and vitrified substances separated by reprocessing operation of spent nuclear fuel, including, for example, radioactive substances , Radioactive contaminants such as soil (hereinafter referred to as “contaminated soil”), ash (hereinafter referred to as “contaminated ash”), and dust (hereinafter referred to as “contaminated dust”).
福島第一原子力発電所の事故により、膨大な量の放射性物質が福島県を中心に広い範囲に拡散した。この放射性物質の中でも放射性セシウム（セシウム１３７）は、半減期が３０年と長く残存量が多いため、長期の放射線被爆による住民の健康被害や農林畜産物の汚染が懸念されている。したがって、かかる状況に対応するため、迅速かつ広範囲にわたる除染作業が必要とされている。しかし、除染に伴い大量に集積する汚染土の保管場所や搬出先の確保、および汚染土を移送する際の飛散防止が難しく、除染等による汚染土の処理には多くの課題がある。 Due to the accident at the Fukushima Daiichi Nuclear Power Station, a huge amount of radioactive material spread over a wide area, mainly in Fukushima Prefecture. Among these radioactive substances, radioactive cesium (cesium 137) has a long half-life of 30 years and a large residual amount. Therefore, there are concerns about the health damage of residents and the contamination of agricultural, forestry and livestock products due to long-term radiation exposure. Therefore, in order to cope with such a situation, quick and extensive decontamination work is required. However, it is difficult to secure a storage place and a delivery destination for contaminated soil that accumulates in large quantities along with decontamination, and to prevent scattering when transporting the contaminated soil, and there are many problems in processing contaminated soil by decontamination.
また、前記発電所から遠く離れた首都圏内の焼却場でも、放射性物質を含む下水汚泥等の焼却により放射性物質が濃縮された汚染灰が、日々大量に発生している。しかし、放射線量が１ｋｇ当たり８千ベクレルを超える放射性汚染物は受け入れ先の確保が難しいため、現在、汚染灰は焼却場に保管されたままである。 In addition, even in incineration sites in the Tokyo metropolitan area far from the power plant, a large amount of contaminated ash is generated every day by incineration of radioactive materials including sewage sludge containing radioactive materials. However, since radioactive contaminants with a radiation dose exceeding 8,000 becquerels per kg are difficult to secure a recipient, the contaminated ash is still stored in the incinerator.
また、放射性汚染物から放射性物質を分離して、問題のないレベルになった非汚染物を原位置に埋め戻したり、処分場に埋め立てたりすることも考えられる。該分離手段として、例えば、重金属の分離・回収に有用な塩化揮発法等の適用が考えられる。しかし、該手段では、放射性物質が濃縮した汚染物（ダスト）のさらなる処理が、最終課題として残る。 It is also possible to separate radioactive substances from radioactive contaminants and backfill non-contaminated substances at a problem-free level in the original position or to landfill in a disposal site. As the separation means, for example, a chloride volatilization method useful for separation and recovery of heavy metals can be considered. However, with this measure, further processing of contaminants (dust) enriched with radioactive material remains as a final challenge.
従来、天然粘土鉱物を含む膨張性ベントナイトや多孔質ゼオライトが、地層における放射性廃棄物の処理や、放射性物質の濾過等に用いられてきた。
ところで、最近、前記事故で生じた汚染土を調べたところ、汚染土中の天然粘土鉱物が放射性セシウムを強く吸着して固定化し、セシウムは地表に長く留まることが確認できたため、セシウムの地中への移行や農作物による吸収は遅いと予想されている。かかるセシウムの固定化メカニズムは、層状構造を有する粘土鉱物の、層間の陰イオンサイトに存在するカリウム等の陽イオンに対し、より結合力の強いセシウムイオンがイオン交換して固定化するとされている。したがって、天然粘土鉱物を用いて、汚染土中のセシウムを固定化することも考えられる。
しかし、天然粘土鉱物は希少資源であり、大量に使用すると資源の枯渇が懸念されるほか、比較的高価なため汚染土の処理材として大量に消費する用途には、経済的理由からも適さない。
Conventionally, expansive bentonite and porous zeolite containing natural clay minerals have been used for the treatment of radioactive waste in the formation, filtration of radioactive substances, and the like.
By the way, recently, when the contaminated soil caused by the accident was examined, it was confirmed that the natural clay mineral in the contaminated soil strongly adsorbed and fixed radioactive cesium, and the cesium remained on the surface for a long time. Migration to and absorption by crops is expected to be slow. The cesium immobilization mechanism is said to be that cesium ions with stronger binding force are ion-exchanged and immobilized to cations such as potassium existing in the anion sites between layers of clay minerals having a layered structure. . Therefore, it is conceivable to fix cesium in contaminated soil using natural clay minerals.
However, natural clay minerals are scarce resources, and when used in large quantities, there is concern about the depletion of resources, and because they are relatively expensive, they are not suitable for uses that consume a large amount as a treatment for contaminated soil for economic reasons. .
そこで、特許文献１では、廃棄物である石炭灰を用いた放射性セシウムの捕集方法が提案されている。具体的には該方法は、石炭灰を単位長さ当りの気孔数が１０〜３０個になる多孔性板状捕集材等に加工した捕集材を利用して、気相のセシウム化合物と７００〜１３００℃で反応させ、セシウムアルミノシリケート化合物の形態に放射性セシウムを固定するセシウムの捕集方法である。しかし、該方法は７００〜１３００℃の高温域で行うため、放射性汚染物の大量処理には不適切である。
また、特許文献２では、モノリス内の化学結合形成により、該モノリス中への放射性廃棄物等の封入を含んでなる、安定なモノリスの製造法であって、該廃棄物はジオポリマー（アルミノシリケートを主成分とする無機ポリマー）の前駆体を含むものが提案されている（請求項１、５、９）。そして、最適な結果は８０℃で達成されると記載されている（段落００２２）。しかし、前記方法は８０℃の加熱を必要とするから、放射性汚染物の大量処理にはまだ十分とはいえない。
したがって、低温域で大量の放射性汚染物を容易に処理できる手段が望まれている。
Therefore, Patent Document 1 proposes a method for collecting radioactive cesium using coal ash which is waste. Specifically, the method uses a cesium compound in a gas phase using a collecting material obtained by processing coal ash into a porous plate-like collecting material having 10 to 30 pores per unit length. This is a cesium collection method in which reaction is performed at 700 to 1300 ° C., and radioactive cesium is fixed in the form of a cesium aluminosilicate compound. However, since this method is performed in a high temperature range of 700 to 1300 ° C., it is not suitable for mass treatment of radioactive contaminants.
Patent Document 2 discloses a method for producing a stable monolith comprising encapsulating radioactive waste or the like in the monolith by forming a chemical bond in the monolith, wherein the waste is a geopolymer (aluminosilicate). A material containing a precursor of (an inorganic polymer containing as a main component) has been proposed (claims 1, 5, and 9). And it is stated that optimal results are achieved at 80 ° C. (paragraph 0022). However, since the method requires heating at 80 ° C., it is not yet sufficient for mass treatment of radioactive contaminants.
Therefore, a means for easily treating a large amount of radioactive contaminants at a low temperature is desired.
そこで、本発明は、低温域で放射性汚染物を大量かつ容易に処理できる処理材を提供することを目的とする。 Then, an object of this invention is to provide the processing material which can process a radioactive contaminant in large quantities easily in a low temperature range.
本発明者は、前記目的にかなう処理材を鋭意検討した結果、特定のフィラーと特定のアルカリ活性剤を含むジオポリマーは、放射性物質の固定化材として優れていることを見い出し、本発明を完成させた。 As a result of intensive investigation of a treatment material that meets the above purpose, the present inventor found that a geopolymer containing a specific filler and a specific alkali activator is excellent as a radioactive material immobilization material, and completed the present invention. I let you.
すなわち、本発明は、以下のとおりである。
［１］（Ａ）石炭灰、およびスラグから選ばれる少なくとも１種以上のフィラーと、（Ｂ）水酸化ナトリウム、水酸化カリウム、珪酸ナトリウム、および珪酸カリウムから選ばれる少なくとも１種以上のアルカリ活性剤と、（Ｃ）水とを含む、放射性物質の固定化材。
［２］（Ｂ）アルカリ活性剤／（Ａ）フィラーの質量比が０．０５〜１である、前記［１］に記載の放射性物質の固定化材。
［３］（Ｂ）アルカリ活性剤中のアルカリ金属／（Ｃ）水のモル比が０．１以上である、前記［１］または［２］に記載の放射性物質の固定化材。
［４］前記固定化材／放射性汚染物の質量比が０．１〜１５となるように混合して放射性物質を固定化する、放射性汚染物の処理方法。
［５］前記放射性汚染物が、汚染ダスト、汚染土、および汚染灰から選ばれる少なくとも１種以上である、前記［４］に記載の放射性汚染物の処理方法。
That is, the present invention is as follows.
[1] (A) at least one filler selected from coal ash and slag; and (B) at least one alkali activator selected from sodium hydroxide, potassium hydroxide, sodium silicate, and potassium silicate. And (C) a radioactive material immobilization material comprising water.
[2] The radioactive substance immobilization material according to [1], wherein the mass ratio of (B) alkali activator / (A) filler is 0.05 to 1.
[3] The radioactive substance immobilization material according to [1] or [2], wherein the molar ratio of alkali metal / (C) water in the alkali activator (B) is 0.1 or more.
[4] A method for treating radioactive contaminants, wherein the radioactive material is immobilized by mixing so that the mass ratio of the immobilizing material / radiological contaminant is 0.1 to 15.
[5] The radioactive contaminant treatment method according to [4], wherein the radioactive contaminant is at least one selected from contaminated dust, contaminated soil, and contaminated ash.
本発明に係る放射性物質の固定化材と放射性汚染物の処理方法は、低温域でも放射性物質を大量かつ容易に固定化処理でき、また、石炭灰やスラグの有効利用を図ることができる。 The radioactive substance immobilization material and the radioactive contaminant treatment method according to the present invention can immobilize radioactive substances in a large amount and easily even at low temperatures, and can effectively utilize coal ash and slag.
本発明は、前記のとおり、（Ａ）石炭灰、およびスラグから選ばれる少なくとも１種以上のフィラーと、（Ｂ）水酸化ナトリウム、水酸化カリウム、珪酸ナトリウム、および珪酸カリウムから選ばれる少なくとも１種以上のアルカリ活性剤と、（Ｃ）水とを含む放射性物質の固定化材、および該固定化材を用いた放射性汚染物の処理方法である。
以下、本発明について、固定化材と処理方法に分けて説明する。なお、％は特に示さない限り質量％である。
As described above, the present invention includes (A) at least one filler selected from coal ash and slag, and (B) at least one selected from sodium hydroxide, potassium hydroxide, sodium silicate, and potassium silicate. This is a radioactive material immobilization material containing the above alkali activator and (C) water, and a method for treating radioactive contaminants using the immobilization material.
Hereinafter, the present invention will be described separately for the fixing material and the processing method. In addition, unless otherwise indicated,% is the mass%.
１．放射性物質の固定化材
（１）石炭灰
石炭灰は、フライアッシュ、クリンカアッシュ、これらの混合物、およびこれらの粉砕物等が挙げられる。フライアッシュは、燃焼ガス中を浮遊する石炭灰の溶融粒子が温度低下によりボイラー出口付近で固化して生成したガラス状球形粒子を回収したものであり、クリンカアッシュは、赤熱状態の石炭灰がボイラ底部の水槽に落下して固化した塊状物を破砕して粒度を調整したものある。
フライアッシュやクリンカアッシュ等の石炭灰は、ジオポリマーにおいて活性度の高いフィラーとして機能するほか、主成分であるＳｉＯ２やＡｌ２Ｏ３がアルカリ活性剤により溶出して、ジオポリマーの構成元素であるＳｉやＡｌの供給源として機能する。これらの中でも、フライアッシュは前記機能が高いため好ましく、ＪＩＳ Ａ ６２０１に規定するＩ種〜ＩＶ種のフライアッシュが使用できる。
該フライアッシュ中のＳｉＯ２の含有率は４０％以上が好ましく、４５〜６５％がより好ましく、５０〜６０％がさらに好ましい。該値が４０％未満では、ＳｉＯ２の供給量が少なく、フライアッシュの活性が十分でない。また、フライアッシュ中のＡｌ２Ｏ３の含有率は１０％以上が好ましく、１５〜３５％がより好ましく、２０〜３０％がさらに好ましい。該値が１０％未満では、Ａｌ２Ｏ３の供給量が少なく、フライアッシュの活性が十分でない。
1. Radioactive substance immobilization material (1) Coal ash Examples of coal ash include fly ash, clinker ash, a mixture thereof, and a pulverized product thereof. Fly ash is a collection of glassy spherical particles produced by coal ash floating in the combustion gas solidified near the boiler outlet due to a drop in temperature. Clinker ash is a red hot coal ash that is recovered from boilers. The particle size is adjusted by crushing the lump that has fallen into the bottom water tank and solidified.
Coal ash such as fly ash and clinker ash functions as a highly active filler in geopolymers, and the main components SiO 2 and Al 2 O 3 are eluted by alkaline activators and are constituent elements of geopolymers. It functions as a source of certain Si and Al. Among these, fly ash is preferable because of its high function, and types I to IV fly ash specified in JIS A 6201 can be used.
The content of SiO 2 in the fly ash is preferably 40% or more, more preferably 45 to 65%, and still more preferably 50 to 60%. If the value is less than 40%, the amount of SiO 2 supplied is small and the activity of fly ash is not sufficient. The content of Al 2 O 3 in the fly ash is preferably at least 10%, more preferably 15% to 35%, more preferably 20-30%. If the value is less than 10%, the amount of Al 2 O 3 supplied is small, and the activity of fly ash is not sufficient.
石炭灰のブレーン比表面積は１５００ｃｍ２／ｇ以上が好ましく、２５００ｃｍ２／ｇ以上がより好ましく、３０００ｃｍ２／ｇ以上がさらに好ましく、３５００ｃｍ２／ｇ以上が特に好ましい。該値が１５００ｃｍ２／ｇ未満では、ＳｉＯ２やＡｌ２Ｏ３の溶出が遅い傾向にある。 Blaine specific surface area of the coal ash is preferably at least 1500 cm 2 / g, more preferably at least 2500 cm 2 / g, more preferably not less than 3000cm 2 / g, 3500cm 2 / g or more is particularly preferable. When the value is less than 1500 cm 2 / g, elution of SiO 2 and Al 2 O 3 tends to be slow.
（２）スラグ
スラグは、高炉スラグ、製鋼スラグ、下水汚泥溶融スラグ、および石炭ガス化溶融スラグ等から選ばれる少なくとも１種以上が挙げられる。スラグは、石炭灰と同様に、ジオポリマーにおいて活性度の高いフィラーとして機能するほか、ＳｉやＡｌの供給源として機能する。これらのスラグの中でも、高炉スラグおよび石炭ガス化溶融スラグは、前記機能が高いため好ましい。
高炉スラグ中のＳｉＯ２の含有率は２０％以上が好ましく、２５〜４５％がより好ましく、３０〜４０％がさらに好ましい。該値が２０％未満では、ＳｉＯ２の供給量が少なく、高炉スラグの活性が十分でない。また、高炉スラグ中のＡｌ２Ｏ３の含有率は１０％以上が好ましく、１２〜２５％がより好ましく、１４〜２０％がさらに好ましい。該値が１０％未満では、Ａｌ２Ｏ３の供給量が少なく、高炉スラグの活性が十分でない。
また、石炭ガス化溶融スラグ中のＳｉＯ２の含有率は４０％以上が好ましく、４５〜６５％がより好ましく、５０〜６０％がさらに好ましい。該値が４０％未満では、ＳｉＯ２の供給量が少なく、石炭ガス化溶融スラグの活性が十分でない。また、石炭ガス化溶融スラグ中のＡｌ２Ｏ３の含有率は１０％以上が好ましく、１５〜３５％がより好ましく、２０〜３０％がさらに好ましい。該値が１０％未満では、Ａｌ２Ｏ３の供給量が少なく、石炭ガス化溶融スラグの活性が十分でない。
(2) Slag The slag includes at least one selected from blast furnace slag, steelmaking slag, sewage sludge molten slag, coal gasified molten slag, and the like. Slag, like coal ash, functions as a highly active filler in geopolymers and also functions as a source of Si and Al. Among these slags, blast furnace slag and coal gasification molten slag are preferable because of their high functions.
The content of SiO 2 in the blast furnace slag is preferably 20% or more, more preferably 25 to 45%, and still more preferably 30 to 40%. If the value is less than 20%, the supply amount of SiO 2 is small, and the activity of the blast furnace slag is not sufficient. The content of Al 2 O 3 in the blast furnace slag is preferably at least 10%, more preferably 12-25%, more preferably 14 to 20%. If the value is less than 10%, the supply amount of Al 2 O 3 is small, and the activity of the blast furnace slag is not sufficient.
The content of SiO 2 in the coal gasification molten slag is preferably at least 40%, more preferably 45-65%, more preferably 50 to 60%. If the value is less than 40%, the supply amount of SiO 2 is small, and the activity of the coal gasification molten slag is not sufficient. Further, the content of Al 2 O 3 of coal gasification molten slag is preferably at least 10%, more preferably 15% to 35%, more preferably 20-30%. If the value is less than 10%, the supply amount of Al 2 O 3 is small, and the activity of the coal gasification molten slag is not sufficient.
高炉スラグの塩基度は１．４以上が好ましく、１．６以上がより好ましく、１．８以上がさらに好ましい。該値が１．４未満では高炉スラグの活性が低い傾向にある。なお、塩基度は、通常、蛍光Ｘ線分析による、ＣａＯ、ＭｇＯ、Ａｌ２Ｏ３、およびＳｉＯ２の各成分の分析値（質量％）に基づき下記式により算出する。
塩基度＝（ＣａＯ＋ＭｇＯ＋Ａｌ２Ｏ３）／ＳｉＯ２
また、高炉スラグのガラス化率は９８〜１００％が好ましい。該値が９８％未満では高炉スラグの活性が低い傾向にある。なお、ガラス化率は、通常、偏光顕微鏡を用いて高炉スラグ中の結晶化部分とガラス化部分をポイントでカウントし、全ポイント数に対するガラス化部分のポイント数の割合で表わす。
The basicity of the blast furnace slag is preferably 1.4 or more, more preferably 1.6 or more, and further preferably 1.8 or more. If the value is less than 1.4, the activity of the blast furnace slag tends to be low. Note that basicity is usually calculated by a fluorescent X-ray analysis, CaO, MgO, Al 2 O 3, and the following equation based on the analytical values of the components of SiO 2 (wt%).
Basicity = (CaO + MgO + Al 2 O 3 ) / SiO 2
Moreover, 98-100% of the vitrification rate of blast furnace slag is preferable. If the value is less than 98%, the activity of the blast furnace slag tends to be low. The vitrification rate is usually represented by the ratio of the number of points of the vitrified portion to the total number of points by counting the crystallized portion and vitrified portion in the blast furnace slag with a polarizing microscope.
スラグのブレーン比表面積は、２０００〜８０００ｃｍ２／ｇが好ましく、２５００〜６０００ｃｍ２／ｇがより好ましく、３５００〜５５００ｃｍ２／ｇがさらに好ましい。該値が２０００ｃｍ２／ｇ未満では、ＳｉＯ２やＡｌ２Ｏ３の溶出が遅く、８０００ｃｍ２／ｇを超えるとコスト高になる。 Blaine specific surface area of the slag, preferably 2000~8000cm 2 / g, more preferably 2500~6000cm 2 / g, more preferably 3500~5500cm 2 / g. When the value is less than 2000 cm 2 / g, elution of SiO 2 or Al 2 O 3 is slow, and when it exceeds 8000 cm 2 / g, the cost increases.
（３）アルカリ活性剤
本発明に用いるアルカリ活性剤は、水酸化ナトリウム、水酸化カリウム、珪酸ナトリウム、および珪酸カリウムから選ばれる少なくとも１種以上が挙げられる。これらの中で、水酸化ナトリウムと珪酸ナトリウムの組合せは、ジオポリマーの圧縮強度が高く、低コストであるため好ましい。
（Ｂ）アルカリ活性剤／（Ａ）フィラーの質量比は０．０５〜１が好ましく、０．１〜０．９がより好ましく、０．３〜０．８がさらに好ましく、０．４６〜０．７が特に好ましい。該比が０．０５〜１の範囲でジオポリマーの強度発現性が良好になる。
(3) Alkali activator Examples of the alkali activator used in the present invention include at least one selected from sodium hydroxide, potassium hydroxide, sodium silicate, and potassium silicate. Among these, the combination of sodium hydroxide and sodium silicate is preferable because the compressive strength of the geopolymer is high and the cost is low.
The mass ratio of (B) alkali activator / (A) filler is preferably 0.05 to 1, more preferably 0.1 to 0.9, still more preferably 0.3 to 0.8, and 0.46 to 0. .7 is particularly preferred. When the ratio is in the range of 0.05 to 1, the strength development of the geopolymer becomes good.
（４）水
本発明で用いる水は、限定されず、水道水、再生水、海水等が挙げられる。
また、（Ｂ）アルカリ活性剤中のアルカリ金属／（Ｃ）水のモル比は、０．１０以上が好ましく、０．１５〜０．５０がより好ましく、０．２０〜０．４５がさらに好ましく、０．２４〜０．４０が特に好ましい。該比が０．１０未満ではジオポリマーの強度発現性が不十分になる。
また、アルカリ活性剤のｐＨは９以上が好ましく、１０以上がより好ましく、１１以上がさらに好ましく、１２以上が特に好ましい。該値が９以上であれば、フィラーの活性が高まる。
(4) Water The water used in the present invention is not limited, and examples thereof include tap water, reclaimed water, seawater and the like.
Further, the molar ratio of (B) alkali metal / (C) water in the alkali activator is preferably 0.10 or more, more preferably 0.15 to 0.50, and further preferably 0.20 to 0.45. 0.24 to 0.40 is particularly preferable. When the ratio is less than 0.10, the strength development of the geopolymer becomes insufficient.
Further, the pH of the alkali activator is preferably 9 or more, more preferably 10 or more, further preferably 11 or more, and particularly preferably 12 or more. When the value is 9 or more, the activity of the filler is increased.
（５）その他の構成成分
本発明の放射性物質の固定化材は、ジオポリマーの強度をより高めるために、シリケートアニオンやアルミネートアニオンを架橋する成分を含んでもよい。該成分は、２価以上の金属が好ましく、例えば、カルシウム、マグネシウム、アルミニウム、および鉄等の塩、水酸化物、および酸化物などが挙げられ、具体的には、塩化カルシウム、水酸化カルシウム、酸化カルシウム、硫酸カルシウム、塩化マグネシウム、水酸化マグネシウム、酸化マグネシウム、硫酸マグネシウム、（ポリ）塩化アルミニウム、硫酸アルミニウム、塩化第一鉄、塩化第二鉄、酸化第一鉄、酸化第二鉄、硫酸第一鉄、および硫酸第二鉄等から選ばれる少なくとも１種以上が挙げられる。
また、本発明の放射性物質の固定化材は、ジオポリマーの強度が低下しない範囲で、さらに、シリカヒューム、シリカ粉末、石灰石粉末等を含んでもよい。
(5) Other components The radioactive material immobilization material of the present invention may contain a component that crosslinks a silicate anion or an aluminate anion in order to further increase the strength of the geopolymer. The component is preferably a metal having a valence of 2 or more, and examples thereof include salts such as calcium, magnesium, aluminum, and iron, hydroxides, and oxides. Specifically, calcium chloride, calcium hydroxide, Calcium oxide, calcium sulfate, magnesium chloride, magnesium hydroxide, magnesium oxide, magnesium sulfate, (poly) aluminum chloride, aluminum sulfate, ferrous chloride, ferric chloride, ferrous oxide, ferric oxide, sulfuric acid Examples thereof include at least one selected from ferrous iron and ferric sulfate.
Further, the radioactive material immobilization material of the present invention may further contain silica fume, silica powder, limestone powder and the like as long as the strength of the geopolymer does not decrease.
２．放射性汚染物の処理方法
該処理方法は、固定化材と放射性汚染物を混練した後、必要に応じて養生して硬化させ、得られたジオポリマー硬化体を保管するものである。固定化材／放射性汚染物の質量比は、放射性汚染物の性状等にも拠るが、通常、０．１〜１５が好ましく、０．５〜１０がより好ましい。
また、本発明における処理対象物は、使用済み燃料の再処理操作で分離された放射性廃液やそのガラス固化体等の高レベル放射性廃棄物を除いた、低レベルの放射性汚染物であり、例えば、汚染ダスト、汚染土、および汚染灰等である。
2. Method for treating radioactive contaminants In this treatment method, the immobilizing material and radioactive contaminants are kneaded, and then cured and cured as necessary, and the resulting geopolymer cured product is stored. The mass ratio of the immobilizing material / radioactive contaminant depends on the properties of the radioactive contaminant, etc., but is usually preferably from 0.1 to 15, and more preferably from 0.5 to 10.
In addition, the object to be treated in the present invention is a low-level radioactive contaminant excluding a high-level radioactive waste such as a radioactive liquid waste or a vitrified substance thereof separated by a reprocessing operation of spent fuel, for example, Contaminated dust, contaminated soil, contaminated ash, etc.
以下、本発明を実施例により説明するが、本発明はこれらの実施例に限定されない。
１．模擬汚染ダストの調製
ブレーン比表面積が２０００ｃｍ２／ｇのクリンカダストに塩化セシウム（試薬１級）を混合して、セシウムの含有率が１００ｐｐｍの模擬汚染ダストを調製した。ここで、クリンカダストとは、セメントキルンの窯尻からボトムサイクロンに至るまでの排ガスの流路から、排ガスの一部を抽気し冷却して得たダストであり、アルカリ金属、特にカリウムを比較的多く含む点に特徴がある。用いたクリンカダストの主な化学組成を以下に示す。
ＳｉＯ２；８．９％、Ａｌ２Ｏ３；３．８％、Ｆｅ２Ｏ３；２．１％、ＣａＯ；５６．５％、ＳＯ３；１０．３％、Ｎａ２Ｏ；０．７７％、Ｋ２Ｏ；９．３％、Ｃｌ；５．８％
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.
1. Preparation of Simulated Contaminated Dust Clinic dust having a Blaine specific surface area of 2000 cm 2 / g was mixed with cesium chloride (reagent grade 1) to prepare a simulated contaminated dust having a cesium content of 100 ppm. Here, clinker dust is dust obtained by extracting and cooling a part of the exhaust gas from the exhaust gas flow path from the bottom of the kiln of the cement kiln to the bottom cyclone. It is characterized by many points. The main chemical composition of the clinker dust used is shown below.
SiO 2; 8.9%, Al 2 O 3; 3.8%, Fe 2 O 3; 2.1%, CaO; 56.5%, SO 3; 10.3%, Na 2 O; 0.77 %, K 2 O; 9.3%, Cl; 5.8%
２．セシウムの固定化試験等
表１に示す配合に従い、クリンカダストを含むスラリーを調製した後、３０℃で２４時間養生してジオポリマー硬化体を作製した。次に、該硬化体の圧縮強度をＪＩＳ Ａ １１０８に準じて測定し、また、該硬化体からのセシウムの溶出量を環境庁告示４６号に準じて測定した。また、比較のために、普通ポルトランドセメントを用いて、蒸気養生（６０℃で８時間）して作製したセメント硬化体からのセシウムの溶出量等を前記と同様にして測定した。これらの結果を表１に示す。
なお、試験に用いた粉体のブレーン比表面積は、フライアッシュが３１００ｃｍ２／ｇ、高炉スラグが４０００ｃｍ２／ｇであった。
2. Cesium immobilization test, etc. A slurry containing clinker dust was prepared according to the formulation shown in Table 1, and then cured at 30 ° C. for 24 hours to prepare a cured geopolymer. Next, the compressive strength of the cured product was measured according to JIS A 1108, and the amount of cesium eluted from the cured product was measured according to Environmental Agency Notification No. 46. For comparison, the amount of cesium eluted from a hardened cement body produced by steam curing (8 hours at 60 ° C.) using ordinary Portland cement was measured in the same manner as described above. These results are shown in Table 1.
Incidentally, the Blaine specific surface area of the powder used in the test, the fly ash is 3100 cm 2 / g, blast furnace slag was 4000 cm 2 / g.
表１に示すように、セシウムの溶出率は、セメント硬化体では１．２％（比較例１）と２．３％（比較例２）であるのに対し、本発明の固定化材では検出限界以下（０．０２ｍｇ/ｌ未満）であった。したがって、本発明の固定化材は、カリウム等の塩類を多く含む放射性汚染物に対しても、セシウムの固定化能が高いことがわかる。 As shown in Table 1, the elution rate of cesium is 1.2% (Comparative Example 1) and 2.3% (Comparative Example 2) in the hardened cement, whereas it is detected in the fixing material of the present invention. Below limit (less than 0.02 mg / l). Therefore, it can be seen that the immobilization material of the present invention has a high cesium immobilization ability even against radioactive contaminants containing a large amount of salts such as potassium.
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