The dome of the internal containment shell (VZO – Vnutrennei Zatsitnoi Obolochki) has been installed at unit 2 of the Akkuyu NPP under construction in Türkiye. This completes construction of the reactor building. The VZO hemispherical dome consists of 15 mounting sections made of special structural steel. Assembly of the dome on took about four months. To lift the structure, a special traverse was designed taking into account the geometry and mass of the dome.
The lifting and installation of the dome, which took about seven hours, was carried out using a heavy self-propelled crawler crane. Some 40 specialists were involved in the operation, providing slinging, securing and balancing the metal structure, as well as guiding and securing it in place.
The VZO is formed from seven tiers. The seventh tier (dome) weighs about 215 tonnes, and the total weight of the structure during lifting, including the service platforms for conductors and the sprinkler system welded to it, exceeds 250 tonnes. Securing, lifting and moving the component is carried out using a special traverse weighing 66 tonnes, which makes it possible to accurately adjust the position of the structure attached to the crane.
“Installation of the internal containment dome is one of the most technically complex and critical operations in the construction of a reactor building,” said Sergei Butskikh, Director General of project company Akkuyu Nukleer. “A team of builders and installers has been preparing for it for several months. A lot of work was involved – manufacturing, delivery of VZO sections to the site by road and sea, enlarged assembly of the structure, welding of its elements and preparation for lifting. The successful completion of the operation is the result of the work of hundreds of specialists: engineers, installers, welders, slingers, crane operators and other specialists.”
The builders will now weld the dome and the cylindrical part of the VZO, which will form a sealed volume of the reactor compartment, and will also continue work on reinforcing and concreting the shell.
The Akkuyu reactors have a double containment system. The VZO consists of a steel lining that ensures the tightness of the reactor compartment and special concrete. It ensures the stability of the reactor compartment, serves as a support for pipeline passages and a polar crane. The outer containment (NZO – Naruzhnoi Zatsitnoi Obolochki) is formed from reinforced concrete and designed to withstand any extreme external influences.
Akkuyu, Türkiye’s first NPP, will eventually host four Russian-designed VVER-1200 reactors. The pouring of first concrete for unit 1 took place in April 2018, for unit 2 in June 2020, for unit 3 in March 2021, and for unit 4 in July 2022. Rosatom is constructing the reactors according to a build-own-operate model. Unit 1 is expected to begin operation in 2025. In July Akkuyu NPP reported that some 70% of the equipment and systems installed at unit 1 had already undergone commissioning.
