The third tier of the internal containment (VZO) has been installed at unit 2 of the Akkuyu NPP under construction in Turkey. The VZO provides protection for the reactor compartment and is a support for pipeline penetrations and a polar crane, which is used to service the reactor during its operation.
The VZO consists of steel cladding, which ensures the tightness of the reactor compartment, and special concrete. The third tier of the VZO is a welded metal structure comprising 24 sections - two tiers of 12 sections each. The sections, each weighing 5-7 tons and 6 metres high, are welded together and assembled into a single cylindrical structure weighing 321.9 tons, 12 metres high and with a circumference of138 metres.
After the installation of the third tier, the height of the reactor building at unit 2 increased by 12 metres and 28.95 metres. specialists will now join the second and third tiers, reinforce and concrete the shell. As soon as the installation of all elements is completed, the shell will be tested for tightness. The installation of the VZO stage is a lengthy technological operation. It took more than 12 hours to install the third tier in the design position using a Liebherr LR 13000 heavy crawler crane.
Sections of the inner containment were delivered by sea from St. Petersburg to the Akkuyu NPP construction site and assembled into a single tier. The pre-assembly of the VZO sections into a single construct took about four months.
Sergey Butskikh, First Deputy General Director and Director of the NPP under construction said another important key event in 2022 has been completed. Following installation of the third tier work will be carried out to build walls inside the containment area up to a mark of 8 metres. “In parallel with the construction of the internal containment at the main facilities of the unit 2, work is underway to build contour walls and walls of the building, as well as work on the arrangement of the reactor shaft,” he noted.
The reactor buildings at the Akkuyu NPP units all have double containment. The outer protective shell is formed from reinforced concrete and designed to withstand any extreme external impact - earthquakes up to magnitude 9, tsunamis, hurricanes, as well as any combination of these impacts.
Meanwhile, specialists of the NA Dollezhal Scientific Research and Design Institute of Power Engineering (Nikiet – part of Rosatom) completed the manufacture and shipment of the first batch of equipment for the automated vibration monitoring and diagnostics system (ASVD) for Akkuyu units 1&2. Before shipment, the equipment passed an acceptance inspection by representatives of Akkuyu Nuclear.
The ASVD is designed to control the vibration state and mechanical values ??of the main and additional rotary equipment (feeding electric pumps, circulation pumps, etc.) in continuous mode. It is a part of the automated process control system (APCS) of the unit. Earlier, representatives of the Nuclear Regulatory Agency of the Republic of Turkey confirmed the compliance of Nikiet’s products with international quality standards, regulatory documentation and safety requirements. Nikiet will supply the ASVD for all four Akkuyu units.
Rosatom is building four VVER-1200 reactors at the site, under a build-own-operate model. Construction of the first unit began in 2018, with start-up planned for 2023. The 4800MWe plant when completed is expected to meet about 10% of Turkey's electricity needs.
Image: The Akkuyu NPP, currently under construction in Turkey (photo courtesy of Akkuyu Nuclear)