感温性高分子ゲルを用いた新規なゲル／液抽出法を提案した．感温性ゲルは体積相転移現象を起こし，温度によってゲルの高分子ネットワーク構造が変化する．N-isopropylacrylamide(NIPA)に2-methacryloyloxyethylacidphosphale(MR)を共重合した感温性ゲルを合成し，硝酸塩水溶液中のAm(III)抽出を行い，Am(III)抽出平衡及び抽出速度に対する高分子ネットワークの構造変化の影響を調べた．
  ゲル/液間のAm(III)の分配比はLCST(下限臨界共溶温度;34°C)以上で大きな値を示し，温度低下に伴う収縮から膨潤へのゲルの体積相転移によって低下した．3°C～40°C聞の温度スイング試験を行ったところ，水溶液中のAm(III)の抽出と抽出されたAm(III)の放出を安定して繰り返すことができた．Am(III)の抽出機構は共重合されたMR(R-OH)に対して
                                        Am³⁺ ＋3R－OH＝ (R－O)₃Am＋3H⁺
と記述され，収縮状態(40°C)の摘出定数は膨潤状態(3°C)の3倍以上の値を示した．Am(III)の代替物質としてEu(III)を用いて， Eu(III)のゲル相内拡散係数を求めた．Eu(III)の拡散係数は40°C，3°Cいずれも10^-12m²/sのオーダーであり，実用的な抽出クロマト樹脂の値と同等であった．また，10°C/minの速い温度変化に対しでもEu(III)抽出容量はよい温度追従性を示した．これらの結果は感温性ゲルの高分子ネットワークの構造変化によってAm(III)抽出及び放出が制御できることを示唆している．

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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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  ゼオライトの一種であるソーダライトは，SiO₄四面体とAlO₄四面体とが頂点を共有してつくる三次元網目状の構造をしており，その空孔にアルカリ，アルカリ土類金属およびハロゲン元素が入ることになる．また，ソーダライトは1000℃以下の低温で合成することができる．これらの性質を利用して重金属類や放射性ヨウ素をソーダライトに固定化することを検討した．
  有害物質の固定化性能はソーダライトの焼成温度パターンに大きく影響される．本研究ではソーダライトの有害物質固定化性能と焼成温度パターンの関係を実験的に検討した．温度制御には線形動作のPID制御ではなく，非線型動作のスライディングモード制御を採用した．

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