THE ELECTROREDUCTION OF NEPTUNIUM(Ⅴ) IN SYNTHETIC HIGH LEVEL RADIOACTIVE WASTE

The electroreduction of Np(Ⅴ) is studied in the N2H5NO3-Fe (Ⅲ) -HNO3 system. Various factors effecting the electrolytic reduction rate of Np(Ⅴ) are studied, and they are acidity of feed solution, temperature, hydrazine and iron ion concentration etc. The electrolytic reduction reaction of Np(Ⅴ) has a first order relationship with respect to Np(Ⅴ) concentration, ie. dNp(Ⅴ)/ dt=k Np(Ⅴ). When the electrolytic solution contains 1.5mol/l HNO3, 0.2mol/l N2H,NO3 and 2g/l Fe3+, the current density is 29mA/cm2, at 30℃, the apparent rate constant k= 3.42×10-2 min-1, the activation energy is 38kJ/mol. The increase of nitric acid concentration improves both the reduction fraction and reduction fate. The electrolytic reduction of Np(Ⅴ) is greatly enhanced in synthetic high active waste solution., the apparent electrolytic reduction rate constant K is 7-10 times as great as that in N2H5NO3-Fe(Ⅲ)-HNO3 system with the same HNO3 concentrations.