The talk will tell about the fundamentals of the concept – application of electrochemical approach to multi-component systems that include aqueous medium, radionuclides, organic matter and living organisms. These will include explanation of basic electrochemical notions and terminology, analysis of multi-component systems and characteristics of their element as well as detection of their key electrochemical properties. The result of these considerations will be justification of an idea about non-specific nature of microbial/radionuclide redox interactions, which will provide the scope and background for the further in-depth discussion. The second part of the seminar will be dedicated to presentation of the first tool of the concept – Pourbaix diagrams and their adaptation to analysis of radionuclide behavior in biological environment which will include explanation of limits for biological systems, transformation of stability fields into reaction equation towards metal ions and radionuclides, identification of essential conditions for running redox reaction and use of the pH – Eh coordinates to determine the characteristics of the reaction under various environmental conditions. Finally, few examples will be given to demonstrate the application of the approach to detect conditions for non-specific reduction of radionuclides and radioactive metal isotopes.