Deoxidation kinetics

The second part of Table 10.22 gives equations for the concentration ratio of tetravalent to pentavalent neptunium calculated for the three reductants listed there. In the older Purex plants the ferrous sulfamate used to reduce plutonium to inextractable Pu reduced neptunium partly to inextractable Np(V) and partly to extractable Np(IV). The reductants now preferred, tetravalent uranium (possibly made electrolytically) or hydroxylamine, are sufficiently strong, in sufficient time, to make neptunium almost completely tetravalent, but the reactions are much slower than reduction of tetravalent plutonium, because of slow deoxidation of the NpOj radical. Kinetics of these reductions are also discussed in Sec. 7.5. 

Gaskell and Saelim [56] reported that the rate of desulphurisation was greater than that calculated from the diffusion of S in Fe and attributed this enhanced rate to Marangoni turbulence at the interface. However, deoxidation and desulphurisation reactions will lead, sequentially, to rapid mass transfer, a low, dynamic interfacial tension, emulsification, and very rapid kinetics. However, emulsification will also lead to a higher inclusion content in the steel. 

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