What is a steam generator and how is it transported?

What does a steam generator do?

The primary circuit water heated in the reactor core does not boil because it is kept under high pressure. This water passes through thousands of thin tubes inside the steam generator. The secondary circuit water surrounding the outside of the tubes heats up and turns into steam; the steam goes to the turbine. The two circuits never mix at any point. The steam generator is therefore part of both the energy transfer and the barrier separating the radioactive primary circuit from the turbine side. It belongs to the highest safety class.

What is different about the VVER type?

In most Western-design pressurised water reactors, steam generators are vertical. The VVER-1200, however, uses a horizontal type: a horizontal cylindrical shell with two elliptical heads, two collectors in the middle that bring in and take out the coolant, heat-exchanger tubes at the bottom and the steam space at the top. Each unit has four steam generators; a total of 16 were manufactured for Akkuyu's four units.

How is it transported from the factory to the site?

1. Factory acceptance: Before shipment it undergoes hydraulic and vacuum tests.
2. Preservation: Nozzle and collector openings are sealed and the internal volume is protected against moisture. In equipment of this kind, the internal volume kept dry is often filled with a dry gas such as slightly pressurised nitrogen; the method to be applied is set by the manufacturer's preservation instructions (see equipment preservation).
3. Factory to quay: It is taken by road from Atommash to the berth on the Tsimlyansk Reservoir. The equipment is carried horizontally on a multi-axle trailer, seated in saddles matching the shape of the shell.
4. Loading onto the vessel: A 650-tonne gantry crane was used for the Unit 1 set. Additional dredging was carried out at the berth for the Unit 2 set.
5. Sea voyage: About 3,000 km via the Don River, the Sea of Azov, the Black Sea, the Turkish Straits, the Aegean and the Mediterranean. For the Unit 1 set, the equipment was chained down in closed holds; the gross weight of the Unit 2 consignment exceeded 1,800 tonnes.
6. Discharge: It is unloaded at the plant's Eastern Cargo Terminal with a heavy crawler crane (a Liebherr LR 1800 for Unit 1).
7. On-site transport and acceptance: For the Unit 4 set, the equipment was taken to the temporary storage area on self-propelled modular transporters (SPMT). There, a commission with representatives of the manufacturer, designer and contractor checks quality, preservation and documentation.

What needs attention during transport?

• Saddle position: The shell is supported only at the points specified by the manufacturer; support at the wrong point creates stress in the shell.
• Lifting points: The stowage plan, saddle positions and crane rigging arrangement are matched to one another.
• Shock and tilt records: The shipment is monitored with sensors throughout; the records are attached to the delivery documents (see shock and tilt sensors).
• Installation sequence: Steam generators are placed after the columns and supports are installed and before the main circulation pipeline is welded.

How does Voltim Global support this?

The main transport of the steam generator is the manufacturer's responsibility and is carried out by ship. Voltim Global, a Mersin-based nuclear project transport supplier, has made more than 450 shipments from Russia to Akkuyu since March 2024.

Published: 30.10.2026 · Voltim Global