Akkuyu Nuclear Power Plant’s First Reactor Circuit Successfully Completes Hydrostatic Testing
The equipment has demonstrated its strength and leak-tightness even under loads exceeding normal operating conditions. The launch of Türkiye’s first nuclear power plant, being built in partnership with Rosatom, has moved a step closer.
The primary circuit of the VVER-1200 reactor includes the reactor pressure vessel, four steam generators, main circulation pumps and the large-diameter pipes connecting them. Hydrostatic testing is a mandatory and critical stage of pre-startup verification. It checks for microscopic leaks, metal flaws and deformation in welded joints.
During the tests, pressure in the circuit was gradually raised to 24.5 MPa, 1.5 times the nominal operating pressure. At the same time, the water temperature was brought to 135°C. These combined conditions place substantial mechanical and thermal stress on welds and support structures.
The equipment remained under peak load for an extended period. Engineers carried out visual and instrument-based inspections of all flanged connections, access openings and welded joints. The successful pressure test confirmed the high quality of installation work and the reliability of the Russian-supplied equipment.
Main Circulation Pump Operation
The main circulation pump units played a key role in the hydrostatic tests. They maintain the continuous flow of coolant through the reactor core and steam generators. During testing, the pumps kept the water circulating at the specified rate.
Operating the pumps in a closed circuit also helped maintain the required temperature. Some of the mechanical energy from the rotating impellers is converted into heat, helping warm the massive metal structures evenly. Uniform heating prevents dangerous thermal stresses from developing and helps protect the metal from damage under high pressure.
The pumps operated under extreme conditions without malfunction, indicating that they are ready for extended industrial operation. Their vibration and acoustic characteristics remained within design limits.
Digital Monitoring
Safe execution of tests of this kind requires continuous monitoring of hundreds of parameters. A Russian-made automated process control system (APCS) handled this task, collecting real-time telemetry from thousands of sensors installed on the reactor pressure vessel, piping and steam generators.
The APCS algorithms analysed readings from strain gauges, pressure gauges and thermocouples, detecting even the slightest deviations in pressure or temperature from the prescribed test profile. If any parameter approached a critical threshold, the system immediately displayed warnings on the operators’ screens in the unit control room.
All test data are automatically stored in secure digital archives. These detailed electronic records will form a core part of the unit’s technical documentation. In the future, analysts will use them as a baseline against which to compare the results of periodic inspections throughout the nuclear plant’s service life.
Final Stage
Pressure testing is one of the last and most critical milestones before startup. The unit is now fully prepared to contain radioactive materials under any conditions, including the most severe accident scenarios.
Work is now moving on to inspections of the reactor’s internal components and final preparations for the safety systems. Meanwhile, Turkish personnel continue training to operate the unit control room. Engineers are rehearsing both normal and abnormal operating scenarios on a full-scope digital simulator, a virtual twin of the actual power unit.
Akkuyu Nuclear Power Plant is being built under a distinctive international build-own-operate (BOO) model. It will comprise four power units equipped with Rosatom’s flagship Generation III+ VVER-1200 reactors. The plant’s total capacity will be 4,800 MW, enough to meet around 10% of Türkiye’s electricity needs. Bringing the first unit online will provide the country with a stable source of low-carbon baseload power and reduce the economy’s reliance on imports of expensive natural gas and coal. Successful completion of hydrostatic testing brings the delivery of fresh nuclear fuel to the site and the launch of Türkiye’s first nuclear power plant closer.
