An advanced reprocessing process with the nuclide separations in HCl system and the nuclide separation processes from high-level radioactive liquid wastes generated from the existing or its improved reprocessing process have been proposed and developed by using the ion exchange techniques. In addition, the ion exchange techniques and the synthesis methods of ion exchange adsorbents developed in our nuclide separation studies were applied to the decontamination techniques for the contaminated water generated by severe accidents.

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Extraction behavior of Sr(II) from nitric acid solution has been investigated using crown ether (18C6 derivative) as an extractant in combination with ionic liquid [C₄mim-NfO] as solvent, where [C₄mim]⁺ is 1-butyl-3-methylimidazolium and [NfO]^－ is nonafluorobutane-sulfonate. For comparison, extraction studies have also been carried out with benzo-18-crown-6 (B18C6), dibenzo18-crown-6 (DB18C6), dicyclohexano-18-crown-6 (DCH18C6) and 4,4′,(5′)-di-(t-butyl)-dicyclohexano-18-crown-6 (DtBuCH18C6). DCH18C6 derivative in C₄mim-NfO system exhibits extremely an high extraction ability for Sr(II) than B18C6 and DB18C6 in concentration of nitric acid, even at high a concentration of inorganic salts. With the present system, extraction behavior has been revealed, which may provide an alternative way for extraction of Sr(II) under HLLW conditions.

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A novel chemosensor based on benzocrown-bipyridine conjugate appending an octadecyl group, 1, was prepared to investigate its ion sensing ability in acetonitrile. The addition of Li⁺ as the guest caused change in color of 1 from yellow to colorless. This is owing to blue shift in intramolecular charge transfer (CT) absorption at around 400 nm, which is associated with the a 1:1 host-guest complex formation. The guest-induced color change of 1 was used for alkali and alkaline metal ion sensing. It was found that 1 detected Ca²⁺ with highest sensitivity.

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