MBIR. Installation of the dome of the reactor building has begun at the construction site of the world’s most powerful fast research reactor MBIR. The process includes installation of 22 arches about 12 meters high, each of which weighs 74 tons. “The work includes 22 stages, each of which is a complex technological operation and requires a lot of preparation. In total, more than 100 builders were involved,” said Sergey Kiverov, deputy director of RIAR for facilities under construction. The MBIR unique capabilities will expand the study of technologies for two-component nuclear power and closing the fuel cycle, as well as help accelerate and justify the creation of safe fourth-generation nuclear power plants.