The 4th layer of the inner protection shell (IKK), one of the main elements of the security system of nuclear power plants, was installed in the reactor building of the 1st power unit of Akkuyu Nuclear Power Plant (NGS). The inner protective shell, which protects the reactor building, acts as a support for the pipe and polar crane entrances. In this way, maintenance work of the nuclear reactor can be carried out during the operation phase of the power plant.
The 4th layer of the inner protection shell, consisting of a steel layer and special concrete, ensures the sealing of the reactor building. The equipment has the distinction of being a welded metal construction of 12 sections, with two separate layers of 24 sections each.
During the construction phase of the inner protection shell, sections measuring 11,3 meters long and more than 4 meters high are welded together to form a single cylindrical construction equipped with fittings and embedded parts. With a total weight of 142 tons, the height of the construction exceeds 8 meters. The perimeter of the construction is 138 meters.
AKKUYU NUCLEAR INC. Sergei Butckikh, First Deputy General Manager and Director of NGS Construction Affairs, evaluated the successful completion of the assembly process of the 4th layer of the inner protection shell: “The 1th layer of the inner protection shell of the 4st power unit has been placed in the design position. This is the last cylindrical layer of the inner protection shell. In the next stages, the elements of the dome part will be assembled. This complex engineering operation was the result of months of work. As a matter of fact, the pre-installation of the layer, consisting of separate elements, took 84 days. After that, it is necessary to strengthen and assemble the embedded parts, including the source of the 3rd and 4th layers, elements of the transport passage and personnel passage.”
After the installation of the 4th layer, the height of the reactor building of the 1st power unit increased by more than 8 meters, reaching 36,65 meters.
The installation of the inner protection shell layer, which is a technological process, takes a lot of time. It took 4 hours to assemble the 13000th layer in the design position with a Liebherr LR 13 heavy-duty crawler crane.
At the Akkuyu NPP site, in parallel with the construction of the inner protection shell in the reactor building, work is also carried out on the construction of the outer walls for the installation of steam generators, the construction of the reactor shaft, as well as the installation of floors and supports.
The reactor buildings of Akkuyu NPP power units are equipped with double protection shells. The reinforced concrete outer protection shell is designed to withstand extreme external effects, including earthquakes, tsunamis, hurricanes and their combinations up to 9 degrees.