Conditions Extrêmes et Matériaux : Haute Température et Irradiation
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2011

ACL
doi

M.Numakura, N.Sato, Catherine Bessada, Y.Okamoto, H.Akatsuka, A.Nezu, Y.Shimohara, K.Tajima, H.Kawano, T.Nakahagi, H.Matsuura, 'Structural investigation of thorium in molten lithiumecalcium fluoride mixtures for salt treatment process in molten salt reactor', Prog. Nucl. Energy 53 994-998 (2011) doi:10.1016/j.pnucene.2011.04.026

X-ray absorption fine structure (XAFS) measurements on thorium fluoride in molten lithiumecalcium fluoride mixtures and molecular dynamics (MD) simulation of zirconium and yttrium fluoride in molten lithiumecalcium fluoride mixtures have been carried out. In the molten state, coordination number of thorium (Ni) and inter ionic distances between thorium and fluorine in the first neighbor (ri) are nearly constant in all mixtures. However the fluctuation factors (DebyeeWaller factor (s2) and C3 cumulant) increase until xCaF2 ¼ 0.17 and decrease by addition of excess CaF2. It means that the local structure around Th4þ is disordered until xCaF2 ¼ 0.17 and stabilized over xCaF2 ¼ 0.17. The variation of fluctuation factors is related to the number density of F in ThF4 mixtures and the stability of local structure around Th4þ increases with decreasing the number density of F in ThF4 mixtures. This tendency is common to those in the ZrF4 and YF3 mixtures. However, in the case of YF3 mixtures, the local structure around Y3þ becomes disordered until xCaF2 ¼ 0.40 and it becomes stabilized by addition of excess CaF2. The difference between ThF4 mixtures and YF3 mixtures is related to the difference of Coulumbic interaction between Th4þ eF and Y3þ eF . Therefore, the variation of local structure around cation is related to not only number density of F in molten salts but also the Coulumbic interaction between cation and anion.