Electrochemical behavior of neptunium in NaCl-2CsCl melt

Hayashi, Hirokazu ; Minato, Kazuo*

For a basis of the future nuclear fuel cycle, understanding the behavior of transuranium elements (TRU: Np, Pu, Am, Cm) is important. Experimental study on pyrochemical reprocessing of the fuels containing TRU is one of the important topics. But limited data are available on the behavior of TRU in some molten salts including NaCl-2CsCl melt which is considered to be used for pyrochemical reprocessing of MOX fuels in RIAR process. Only the electrochemical behavior of NpNp redox couple has been reported for Np ions in NaCl-2CsCl melt. In the present study, behavior of Np ions including the reduction of Np in NaCl-2CsCl melt was investigated. A typical cyclic voltammogram shows 2 groups of the signals corresponding to Np species. They were assigned to the redox reactions of Np/Np and NpNp, respectively by comparing with those observed in LiCl-KCl melt. The redox potentials and the diffusion coefficients obtained by various transient electrochemical techniques will be presented.