The electrochemical properties of neptunium, dissolved in LiCl-KCl eutectic, were investigated, using cyclic voltammetry and chronopotentiometry, on inert tungsten electrodes. It was shown that Np4+ was reduced to Np0 via a two-step mechanism, corresponding to the transitions of Np4+/Np3+ and Np3+/Np0. At 673 to 823K, the diffusion coefficients of Np3+ and Np4+ were of similar magnitude:

Np3+:     D(cm2/s) = 9.47 x 10-4exp[-23.6(kJ/mol)/RT]

Np4+:     D(cm2/s) = 2.14 x 10-4exp[-14.1(kJ/mol)/RT]

Electrochemical Behaviour of Neptunium in the Molten LiCl-KCl Eutectic. P.Masset, C.Apostolidis, R.J.M.Konings, R.Malmbeck, J.Rebizant, J.Serp, J.P.Glatz: Journal of Electroanalytical Chemistry, 2007, 603[2], 166-74

Table 104

Diffusion of Pu4+ Ions in Eutectic LiCl-KCl Melts