In the reactor compartment of the 1st Power Unit of Akkuyu NPP, the fifth layer of the inner protection shell (IKK), which is one of the main elements of the safety system, providing the protection of the reactor building, acting as a support for the pipe and polar crane inlets that serve during the operation of the nuclear reactor, was installed.
The IKK consists of a steel layer and special concrete that seals the reactor building. The fifth layer of the IKK is a welded metal structure consisting of 12 sections. The partitions weighing 10,75 tons and height 6,45 meters were welded together on a special platform, forming a single ring with a total weight of 129 tons and a diameter of 44 meters in the wide (bottom) part. The finished ring was then lifted off the ground with the aid of a heavy crane and placed at the design level in the reactor building.
First Deputy General Manager – NGS Construction Director Sergei Butckikh evaluated the completion of the assembly process of the 5th layer of the IKK as follows: “The main challenge in performing the installation was that the fifth layer was a transition element between the cylindrical and domed parts of the shell. A comprehensive preparation was made one day after the procedure, taking into account many parameters such as the weight of the load, the distance to which the load will be carried, the hanger connection diagrams, the weather conditions on the day of installation, and many other factors. The technical process was successfully completed and the load was transported to the installation site with an accuracy of one millimeter. In the next step, builders will need to assemble 60 consoles that will act as supports for the pole crane's rail track. This is an important structural element of the reactor building, they will carry the main loads from oversized equipment and crane-lifted loads.”
After the installation of the fifth layer, the height of the reactor building of the 1st Power Unit increased by 6,5 meters, reaching 43,1 meters.
The installation of the IKK layer is a time-consuming technological operation. It took 13000 hours to assemble the fifth layer in the design position with a Liebherr LR 12 heavy-duty crawler crane.
Parallel to the construction of the inner protection shell in the reactor building, the outer and inner walls are being built, and the assembly of vehicle, pedestrian crossings and spare crossings continues. In the turbine building, the floors of the first floor at an elevation of 8,4 meters are being built, and the construction of the walls and columns continues.
The reactor buildings of Akkuyu NPP power units are equipped with double protection shells. The reinforced concrete outer protection shell is designed to withstand a 9-magnitude earthquake, tsunami, hurricane and extreme external impacts combined with these.