Electrochemical reduction of Tc(VII) on a mercury electrode in alkali solutions

Reduction of Tc(IV) in 0.1-4.0 M NaOH was studied by tast polarography and differential pulse polarography on a stationary dropping mercury electrode and by cyclic voltammetry on a suspended mercury drop, At NaOH concentration from 0.1 to 2.0 M the polarograms contain two reduction waves I and II at halfwave potentials from -0.775 to -0.705 and from -1.07 to -1.00 V (vs, Ag/AgCl), respectively. The ratio between the limiting currents of waves II and I decreases with increasing NaOH concentration in the solution. Wave II disappears in 4 M NaOH. Technetium(VII) reduction described by wave I is irreversible and is controlled by diffusion. Wave II is of adsorption nature. As calculated by logarithmic analysis of the tast-polarographic waves and peaks of the differential pulse polarography, the number of electrons involved in the electrode reaction in 0.1 and 4 M NaOH is 1.05 and 2.5, respectively, These values determined by the Cottrell's equation are 3.24 and 2.44, respectively, The difference indicates that electrolytic reduction of Tc(VII) involves disproportionation of Tc(VI) and Tc(V), Technetium(VII) can be determined by the differential pulse polarography with a detection limit of 10 mu g l(-1) in alkali solutions containing nitrate, nitrite, and carbonate ions and containing no chromate ions which are reduced at the potentials close to the reduction potential of Tc(VII

Physicochemical behavior of uranium and technetium in some new stages of the nuclear fuel cycle

Recently published results of the cooperative studies executed by the Institute of Physical Chemistry and Electrochemistry of Russian Academy of Sciences (IPCE RAS), Research Center Vallée du Rhone (CEA, France), Institute of Nuclear Physics Orsay and University Bordeaux I [Centre Nationale de Recherches Scientifiques (CNRS), France] are reviewed. The review includes data obtained for the first time on the electrochemical properties and anodic dissolution of uranium monocarbide considered among possible bases of the fuel for the reactors of the IVth generation. The results of the investigations in the field of the synthesis of tetraalkyl ammonium pertechnetates, their physicochemical properties and thermal decomposition with formation of Tc metal and Tc monocarbide are summarized. The electrochemical reactions with participation of Tc ions in various oxidation states and their application in the nuclear fuel cycle are described. The behavior of technetium in natural waters near the locations of the radwastes long-term storage and in the areas surrounding nuclear power plants in RF and France was studied