Study on encapsulation of radioactive waste elements inside carbon nanocapsules

放射性廃棄物に含まれる元素のカーボンナノカプセルへの内包に関する研究

山本 和典

Yamamoto, Kazunori

カーボンナノカプセルは、その内部空洞にさまざまな元素を内包することが知られている。これまでに内包が報告された元素は、ランタノイドの多く、アクチノイド,アルカリ土類,多くの遷移元素,その他、B, Si, Sなどである。ここで強調すべきことは、典型的な使用済核燃料に含まれる元素のほとんどが、これらのカーボンナノカプセルに内包される元素と重なることである。炭素の化学的安定性とナノカプセルを構成するグラフェンの機械的安定性を考慮すると、このカプセルは放射性核種の放出を完全に防ぐことができるバリアとなるであろう。

Carbon nanocapsules are known to encage many kinds of elements in their inner cavity. The elements that were reported to be encapsulated in carbon nanocapsules are: lanthanides such as La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm and Lu, actinides such as Th and U, alkaline earth such as Ca and Sr, transition elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir, Pt and Au, and some other elements such as B, Si, S, Ge, Se, Sb. The elements that can be encaged in carbon nanocapsules will increase in number, because there are more than 10 elements that have not been tested, such as Tc, Pm, Ac, Pa, Np, Pu, Am, and Cm, each of which is expected to be encaged in carbon nanocapsules. It should be emphasized that most of the elements in a typical nuclear spent fuel also appear in the elemental table where the elements can be encaged in the nanocapsules. Considering chemical stability of carbon and also mechanical stability of graphene wall in nanocapsules, the capsule will act as a perfect barrier to radionuclide release.