Construction sites. The work began at El Dabaa Unit 1 to install the first tier of the inner containment. The first tier consists of 12 ‘petal’ blocks, each weighing between 60 to 80 tonnes. The installation was preceded by concreting the lower foundation plate. The inner containment ensures nuclear and environmental safety of the reactor unit. When completed, the inner containment will be a cylinder-shaped reinforced concrete structure covered with a hemispherical dome, which houses the nuclear reactor and primary circuit equipment of the power unit. In case of emergency, the inner containment prevents the release of radioactive substances into the environment. Rosatom is building four VVER-1200 reactor units at El Dabaa, with construction works running in parallel in all the four of them.