Atommash, the Volgodonsk branch of Russia’s AEM-Technologies (part of Rosatom’s mechanical engineering division Atomenergomash) has begun welding the hulls and bottoms of the passive core bay system (SPZAZ) for unit 1 of the Akkuyu NPP (under construction in Turkey, Atomenergomash said on 25 August. Specialists assembled and welded stainless steel shells 60mm thick. Inside each tank, decks were installed, which are a prefabricated welded structure from a round bar with a diameter of 4 metres and a mass of 495kg. The platforms are designed for the safe movement of service personnel inside the tanks.

The final stage in the assembly of the hulls is the welding of the two heads with the hull. To manufacture of SPZAZ tanks, Atommash specialists applied fully automatic welding and root extraction modes. All circumferential seams were automatically welded outside and inside. Thus, the manufacturing time for the vessels was reduced by 300 standard hours. Welding of end seams on one product is now performed nine days faster.

The SPZAZ belongs to the second stage of passive NPP safety systems. The system includes eight hydraulic tanks with a volume of 120 cubic metres. During operation at the station, an aqueous solution of boric acid, heated to 60 degrees Celsius, is stored in tanks. When the pressure in the primary circuit drops below a certain level, the liquid is automatically supplied to the reactor and the core is cooled.

The weight of the SPZAZ tank is 77 tons, the height is 10.5 metres, and the diameter is 4.24 metres. Atommash will manufacture SPZAZ hydraulic tanks for Akkuyu 1&3.

Rosatom is building four VVER-1200 reactors at Akkuyu, under a build-own-operate model. Construction of the first unit began in 2018, with start-up planned for 2023. The 4800 MWe plant when completed is expected to meet about 10% of Turkey's electricity needs.