報告書番号

N05064

タイトル（和文）

コロイド-岩石間でのセシウムの分配 -実験系の構築とコロイド-岩石間の分配の観察-

タイトル（英文）

Distribution of Cesium between colloid-rock phases-establishment of experimental system and investigation of Cs distribution between colloid and rock-

概要 （図表や脚注は「報告書全文」に掲載しております）

コロイド-岩石-水の3相で核種がどのように分配されるかを、定量的に評価できる系を確立し、セシウムのコロイド（方沸石、ベントナイト）－岩石（マスコバイト）－水の3相それぞれへの分配を定量的に明らかにした。3相間での水相中Cs濃度に対する吸着量と2相（コロイド-水あるいは岩石-水）間の吸着・脱離において評価された値は異なっていた。さらに、コロイド相に対する核種の吸着が不可逆的に吸着を含む場合、液相に核種を添加するケースとコロイドに核種を吸着させて再分配するケースとでは、各相への分配係数が大きく異なることを明らかにした。これらの結果から、2相間で得られた吸着等温線や分配係数を、3相間での分配の定量的な予測に用いることが不適切であることが分かった。

概要 （英文）

Distribution and re-distribution of cesium between 3-phases (colloid, rock and water) was investigated. Analcite and bentonite colloid ware used as colloid phase and muscovite was used as rock phase. Before investigating the distribution between 3-phases, sorption and desorption behavior of Cs on analcite colloid, bentonite colloid and muscovite was investigated. It was found some fraction of Cs sorbed irreversibly on analcite colloid, while Cs sorbed reversibly on bentonite colloid. The experimental system was established for assessment of the distribution of nuclides between 3-phases by using combination of membrane filter and experimental cell. Since colloid and muscovite were separated by membrane filter, sorption of colloid on muscovite could be prevented and we could obtain distribution of Cs as ion. The distribution of Cs between 3-phases were obtained by this experimental system. Furthermore, re-distribution experiment was also carried out by using this system. After 7 days contact of colloid with Cs, distribution of sorbed Cs on colloid to liquid or muscovite phase was investigated. Comparing sorption and desorption isotherm with the distribution of Cs between 3-phases, it was found that Kd value of colloid (ratio of Cs concentration in liquid phase to amount of sorbed Cs on colloid phase) estimated in 2-phases (water and colloid) is different from that in 3-phases. Furthermore, in the case of analcite colloid, Kd value of colloid obtained in 3-phases distribution experiment was different from that obtained in re-distribution experiment. This is considered because of the irreversibility of Cs sorption on analcite colloid. Thus, it was found distribution of Cs in 3-phases was not predictable from sorption and desorption isotherm or Kd value of 2-pases (water-rock, water-colloid).

報告者

キーワード