A new gel-liqnid extraction technique using a thermosensitive gel was proposed. The thermosensitive gel shows the conformational change of polymer network with temperature, which is known as the phase transition phenomena of gel. The extraction rate and equilibrium of Am(III) in an aqueous solution containing nitrate ion were measured batchwise by using a thermosensitive gel, N-isopropylacrylamide (NIPA) copolymerized with 2-methacryloyloxy- ethylacidphosphate (MR). The effects of the conformational change of polymer network on the extraction rate and equilibrium were discussed.
  The distribution ratio of Am(III) showed a large value at higher than LCST (low critical solution temperature; 34°C) and was decreased by the phase transition of gel from shrinking to swelling with decreasing temperature. The extraction of Am(III) in the aqueous solution and the release of Am(III) extracted in the gel were repeated stably by the temperature swing operation between 40 and 3°C. The extraction mechanism of Am(III) was described simply as
                                Am³⁺ ＋3R－OH＝ (R－O)₃Am＋3H⁺ (R-OH: MR).
The equilibrium constant at the shrinking state (40°C) was more than 3 times of that at swelling state (3°C). The gel-phase diffusivity of Eu(III) used as a substitute of Am(III) was evaluated as the order of 10^-12 m²/s at either of 3 or 40°C, which was similar to those for practical extraction chromatographic resins. The temperature-response of gel for the extraction of Eu(III) was very excellent without delay even for the rapid temperature change at 10°C/min. These results suggest that the extraction and release of Am(III) in an aqueous solution can be controlled by the conformational change of polymer network of thermosensitive gel.

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  This paper reviews recent R&D activities in Japan about nuclear waste disposal, reprocessing, and partitioning and transmutation.

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  Ab initio Hartree Fock (HF) theory and Density Functional theory (DFT) have been used to predict the Gibbs free energy of formation (ΔG_f⁰) for uranium (VI) hydrolysis complexes. B3LYP is a better method to calculate the chemical properties of the complex and large molecules. The calculations were performed in the presence of solvent (water) by using the dielectric continuum modeling PCM method as well as the revised Born model. The pressure parameter p=1354atm was used to reproduce the entropy of ions in solution. The calculated energy demonstrates that PCM model is better than Born model in calculating the hydration energy. The primary hydration shell has been included in the calculation. It shows that the B3LYP calculated results inclusive of the primary hydration shell and the PCM hydration energy have reasonable agreement with experiments.

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  A new cesium ion-sieve (Cs-IS) was developed by cesium ion extraction/introduction reaction with ZMPP. The investigation on its properties showed that Cs-IS not only remains the similar microcrystalline structure of ZMPP, but also carries forward the large exchange capacity for cesium and good chemical stability in the medium of 3mol/dm³ HNO₃ from ZMPP. In the static exchange with the strong acidic simulated HLLW, Cs-IS exhibits high exchange rate for cesium and large separation factor β_Cs/M.

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  Water-glass and water-granite interactions in Beishan Area, a potential area for China HLW repository, have been studied using EQ3/6, a geochemical software package developed by the Lawrence Livermore Laboratory for use in modeling the complex geochemical processes that occur when aqueous solutions react with soil, rock, or solid waste materials, and the results of calculation are reported in this paper. The modeling shows that a lot of secondary minerals which contain the components of the glass could be formed due to the interaction between glass and groundwater of Beishan Wuyi well. The formation of the secondary minerals could not only decrease the concentrations of the radionuclides in the groundwater, but also fill and block the pores in the rock, and reduce the groundwater flow rate. These processes are very important to prevent the nuclides from migrating into the human’s environment. The most significant feature for the interaction between groundwater and granite from Beishan area is the precipitation of large amount of clay minerals, such as montmorillonite, smectite, nontronite, beidellite and so on, in the later stage of the reaction. All of them have very strong adsorptivity for the nuclides. So it is thought that the granite of Beishan Area is favorable to the construction of HLW repository.

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  Sodalite is characterized by an ordered aluminosilicate framework of AlO₄ and SiO₄ tetrahedra which involves Na⁺ and Cl^-ions in cubo-octahedral cages.
  And sodalite can be synthesized at temperature less than 1000℃. Considering those properties of sodalite, we examined experimentally fixation of iodine and cadmium as sodalite wastes.
  Fixation performance of sodalite waste depends strongly upon reaction temperature pattern. In this study, we examined relation between fixation performance and reaction temperature pattern. We employed not PID control algorithm with linear action but sliding mode control algorithm with nonlinear action for reaction temperature control.

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