The installation of some main equipment components of the reactor facility has been completed in the reactor building of the 1st Power Unit of Akkuyu Nuclear Power Plant (NGS). Among the main components whose installation was completed, in addition to the nuclear reactor pressure vessel, whose assembly was completed in 2021, there were pressure vessels of the main circulation pumps units (ASPU), emergency core cooling system (ADKS) hydraulic tanks and steam generators in the reactor building. In addition, the main circulation pipeline (ASBH) blocks, which were pre-assembled in a specially equipped workshop at the NGS construction site, were also sent to the assembly site.
The assembly process is done using “Open Top” technology, which is based on lowering the equipment from the open upper cylindrical section of the reactor building with the aid of a heavy-packed crane, type Liebherr LR 13000.
Making a statement on the subject, AKKUYU NÜKLEER A.Ş First Deputy General Manager and NGS Construction Director Sergey Butckikh said, “By installing the steam generators, we are one step closer to the welding process of the main circulation pipeline, where the circulation of the first cycle cooler will take place, which is the milestone of the construction of the first power unit. Builders will now need to equip the so-called clean assembly area. During the welding process of the main circulation pipeline, the cleanliness of the premises, air quality and humidity must be ensured, because the predetermined special requirements for the quality of the welded joints of the main circulation pipeline must be strictly observed.
The pressure vessels of the main circulation pump units, which are among the equipment whose assembly has been completed, are first class safety products. The main circulation pump unit provides the circulation of the refrigerant (treated water) at a temperature of 300 degrees Celsius and a pressure of approximately 160 atmospheres in the nuclear power plant. A single pressure vessel weighs over 31 tons, is 3.5 meters high and 3 meters wide. A single power unit of nuclear power plants with VVER-1200 type reactors is equipped with four main circulation pump units. However, the safe operation of the NPP is ensured by reducing the capacity of the power unit with two pumps in operation.
Emergency core cooling system hydraulic tanks stand out as one of the most important elements of the NGS security system. Four tanks made of carbon steel weighing 78 tons each are installed, one in each loop of the main circulation pipeline. During operation, these tanks containing 60 tons of aqueous boric acid solution are connected to the reactor pressure vessel.
The emergency core cooling system is equipment designed to automatically transfer the cooling boric acid solution to the reactor core in case of refrigerant leakage. The system ensures that residual heat from the reactor is safely removed in the event of an emergency where the pressure of the first cycle drops.
Steam generators, which are the main equipment of the circulation cycle of the reactor facility, stand out as equipment designed to transfer the heat released in the reactor core to the second cycle where water steam is produced, which rotates the turbine of the power unit.
After the installation of the steam generators is completed, the preparatory stage for welding works of the main circulation pipeline connecting the main equipment of the first cycle of the NPP begins. The welding phase of the main circulation pipeline, which is extremely important to ensure the safe operation of the power unit, takes about 3 months. Welding work is scheduled to begin in the spring of 2022.