The data on the uranium metal corrosion rate in the solutions of nitric acid (0,1 – 4M) and effect of complex forming agents on uranium corrosion properties are presented. The increase of HNO 3 concentration caused the shift of corrosion potential from 38mV to 446mV and the increase of the corrosion rate from 0,02 to 0,62mg.cm -2 h -1 . Transpassivation potential of U metal was found weakly effected by HNO 3 concentration varying from 448 to 470mV/Ag/AgCl. The addition of HCOOH to the electrolytes containing less than 3M HNO 3 found to shift the values of corrosion potentials about 500mV towards negative direction reducing the passivation of U metal. The data on the kinetics of oxidative dissolution of PuO 2 using Ag(II) and Am(VI,V) as mediators and the effect of the mediator generation techniques are discussed. The electrochemical properties of UC in the solutions 2 – 4M HNO 3 , results of the quantitative determination of “oxidizable carbon” in dissolver solutions are presented. The results of corrosion and dissolution studies of Tc metal and Tc - Ru alloys containing from 19 to 70 at.% Ru in 0.5 0– 6M HNO3 indicate the formation of passive films of Tc(IV) – Ru(III,IV) hydroxides at the electrode surface in the solutions containing less than 2M HNO 3 at the potentials less than 650mV/Ag/AgCl. The increase of HNO3 concentration to values exceeding 3M and the shift of the electrode potential towards positive direction causes the transition of the Tc and Tc-Ru alloys to transpassive state. The values of transpassivation potentials increase with the increasing with HNO 3 concentration. Quantitative dissolution of Tc metal without application of oxidation potential becomes possible in the electrolytes, containing more than 4M HNO 3 . The rate of Tc – Ru alloys dissolution is noticed to slow down with the increase of Ru content in the alloy.