Hydraulic strength tests of the secondary circuit have
been successfully completed at the first power unit of Akkuyu NPP (being built
by Rosatom). In the course of three days, tests were conducted on the steam
generators, steam valve assemblies, and feedwater pipelines. All four steam generators and their associated piping were tested at a
pressure of 12.6 MPa, which is 15% higher than the operating pressure specified
in the design. For example, in the natural environment comparable pressure
level can be found in the ocean at a depth of about 1.25 kilometers.
Before increasing the pressure, the steam generators were heated to 126 °C, and the maximum water temperature during the tests was 135 °C. The pressure was increased in stages, and at each stage, specialists carefully monitored the equipment parameters and the leak-tightness of the connections. It was held at a maximum pressure of 12.6 MPa, then reduced to 10.1 MPa for a final examination. The inspection confirmed the equipment's resistance to high pressure and its readiness for further testing under operating conditions.
"The tests conducted confirmed the strength of the secondary circuit equipment, as well as the quality of the installation and welded joints. This is a result of extensive collaborative efforts by builders, installers, adjusters, and operating personnel, as well as representatives fr om Rosatom’s external expert organizations, who conducted technical inspections directly during the tests. The results we've obtained allow us to begin preparations for the hot run-in of the first power unit," Akkuyu Nuclear JSC Chief Executive Officer Sergei Butсkikh noted.
The work involved staff from the technical department of Akkuyu Nuclear, as well as technical inspection specialists from relevant organizations within Rosatom – Atomtechenergo JSC and Rosatom Service JSC – as well as representatives of the regulatory authority, the Nuclear Regulatory Authority of Türkiye (NDK).
Power units with the VVER-1200 reactors have two
circuits. The reactor is part of the closed and leak-tight primary
circuit. The nuclear fission reaction in the reactor releases a large amount of
thermal energy. It heats the coolant (demineralized water) as it flows through
the primary circuit under high pressure (16.2 MPa) and temperature (up to
330 °C). The coolant circulates within the primary circuit due to the
operation of the reactor coolant pumps. Heated water from the reactor comes into the steam generators, wh ere it
transfers its heat to the secondary circuit water causing it to boil and
produce steam. The dual-circuit design ensures that the circuits are
completely isolated from one another: The water from the reactor transfers
thermal energy through the heat exchange surface and does not physically come
into contact with the water in the steam generators. The steam produced drives
the steam turbine shaft. The rotation of the shaft is transmitted to the
electric generator which generates electricity as it rotates. The electricity
generated by the generator is supplied to step-up transformers, after which it
travels through SF6-insulated bus ducts to the switchgear and is then fed into
the grid.
Akkuyu NPP is the first nuclear power plant under construction in the Republic of Türkiye. The Akkuyu NPP project consists of four power units with Russian-designed VVER generation 3+ reactors. The capacity of each power unit will be 1,200 MW. Akkuyu NPP construction is the first project in the global nuclear industry implemented on the basis of the Build-Own-Operate business model.
