The redox behavior of technetium is central to its mobility, separation, and long-term containment

Abstract Technetium is part of the fission products of uranium formed during the operation of a nuclear reactor. The accumulation of technetium in the fuel of modern NPPs with VVER-100 type reactors is about 1,090 g/t-U with a burnup of 40 GW·day/t U or 4 % of heavy atoms. the presence of Tc has a significant impact on the processes occurring during SNF reprocessing, since this element is characterized by the half-life is 212 thousand years and the presence of multiple valence forms, as well as catalytic activity and the ability to interact with reducing agents, including those used in Purex, and its removal into radioactive waste together with relatively short-lived ( T 1/2 = 30–50 years) fission products, the handling of which involves near-surface storage, seems unacceptable. Therefore, the removal of technetium into a separate stream at the hydrometallurgical stage and its subsequent isolation in a form suitable for long-term controlled storage in anticipation of transmutation or for deep burial in geological formations are important technological tasks. Interest in redox transformations of technetium is due to the development of new approaches to the processes of spent nuclear fuel reprocessing, radioactive waste management, and the emergence of new redox reagents for the technology of spent nuclear fuel. This review considers the main redox processes that determine the behavior of technetium in SNF reprocessing and in the environment.