The second tier of the internal containment shell, which refers to the main components of the nuclear power plant's safety system, was installed in the reactor building of the second power unit of Akkuyu NPP. ICS ensures protection of the reactor compartment and acts as support for pipeline penetrations and the polar crane, which is used to carry out nuclear reactor maintenance operations at the NPP operation stage.ICS consists of steel liner, which ensures leak-tightness of the reactor compartment, and special concrete. Second tier of the ICS is a welded metal structure consisting of 24 sections, with two tiers each containing 12 sections. 6-metre-high and 5-to-7-ton sections are welded to each other and assembled into a single cylindrical structure equipped with rebars and embedded parts. The total weight of this 12-metre-hight structure is 321.9 tons, while its circumferential length is 138 metres. Installation of an ICS tier is a complex and time-consuming operation. Installation of the second tier in the design position using Liebherr LR 13000 heavy crawler crane took 12 hours.Upon installation of the second tier, the height of the Unit 2 reactor building rose 12 metres and reached 16.95-metre elevation. Afterwards the builders will weld the first tier and the second tier to each other and carry out additional reinforcement and concrete pouring of the shell. The thickness of concrete-enveloped walls of ICS cylindrical part will be 1.2 metres. Once installation of all components and concrete pouring of the containment are completed, it will be subjected to leak-tightness tests.