[en] During the last years a special electrochemical procedure was developed for the decontamination of large or inmobil equipments using movable cathodes. Three electrochemical, remotely operated decontamination equipments have been developed in Hungary for the Paks NPP. Considering the good decontamination results achieved by the above mentioned equipments the development of the electrochemical method has been extended for the decontamination of the main pipeline. The following experimental methods were used: Development of a weak acidic electrolyte on the base of laboratory equipments; design of a crawler as a carriere of testing and decontamination devises (decontamination head, isotope container, TV-cameras, etc); construction and testing of the crawler and its accessories. The results obtained are: using an electrolyte containing oxalic and citric acid (pH 3.5) the achievable decontamination factor was relatively high (20-500) and the corrosion rate was low; the crawler was tested in horizontal, vertical and apple pipes under inactive circumstances. 14 figs