The article presents the results of work on dismantling the large installation equipment of Research Building B at the Bochvar High-technology Research Institute of Inorganic Materials (Bochvar Institute). The works were carried out as part of Building B preparation for decommissioning. The purpose of dismantling the large-sized capacitive equipment was to reconstruct the large installation site for managing radioactive waste generated during Building B decommissioning. The works on decommissioning a radioactively contaminated building within a densely populated district of megalopolis were carried out for the first time. The characteristics of the large-sized capacitive equipment are presented. Radioactive contamination of the capacitive equipment is determined by long-lived a-emitting isotopes: 235U, 238U, 239Pu. The sequence of works on dismantling the radiation-contaminated capacitive equipment includes preparatory work, dismantling the tank piping, localizing radioactive contamination of the external surface of the equipment as well as dismantling and moving it into a transport container. Dismantling and decontamination of the large-sized capacitive equipment was carried out by the Bochvar Institute Decommissioning Department. The following tools were used during the works: (1) a mobile foam decontamination facility to perform decontamination works and (2) a mobile high pressure facility to apply localizing and decontaminating film coatings. The tanks were dismantled by means of low-spark tools, i.e., reciprocating saws. Crane runways were made in order to move the dismantled equipment into transport containers: the movement was carried out with the help of a winch. The main results of dismantling and decontaminating the radioactively contaminated tanks are the dismantling of four units of long-length column-type equipment with heights from 4.2 to 6.4 m and 26 units of capacitive equipment (maximum capacity = 8 m3) as well as decontamination of the internal surfaces of radiation-contaminated equipment (decontamination factor = 25–70). As a result, the activity of the accumulated radioactive waste was reduced (the RW class was changed from 3 to 4). The main conclusion regarding the managment of large-sized radiation-contaminated tanks during Building B decommissioning is as follows: the works were organized and carried out at a high technical level, using modern decontamination and dismantling equipment and modern methods to ensure work safety at the Bochvar Institute site in the city of Moscow.