Commissioning at a nuclear power plant is the process in which it is proven, step by step, that the systems of a unit whose construction is complete operate according to design. It begins with cold and hot functional tests without fuel; after the operating licence is granted, fuel is loaded, the reactor is brought to criticality for the first time, the generator is connected to the grid and power is increased gradually until commercial operation begins.
At what point in construction does commissioning start?
Commissioning is not a single event that begins after the last concrete is poured. Systems are taken over one by one while construction is still under way: first power distribution, pump stations and emergency diesel generators, then the reactor installation. For Akkuyu Unit 1, the Nuclear Regulatory Authority (Nükleer Düzenleme Kurumu) granted the commissioning permit in December 2023; this permit cleared the way for pre-start-up and adjustment work. At this stage, the site operates both as a construction site and as a facility preparing for operation.
The stages step by step
- Pre-tests without fuel: Auxiliary systems, electrical equipment and the automated process control system are commissioned and adjusted.
- Dummy fuel loading: At Akkuyu Unit 1, 163 dummy fuel assemblies were loaded into the reactor in June 2026. These assemblies have the same design, weight and dimensions as real fuel but contain no nuclear material (see dummy fuel assembly).
- Cold hydrostatic test: The primary circuit is filled with demineralised water and the pressure is raised. In the tests at Akkuyu 1, which started in June 2026 and were completed in October 2026, the circuit was brought to 24.5 MPa, about 1.5 times the normal operating pressure.
- Hot functional test: Equipment is tested at temperatures and pressures close to operating conditions; the four main circulation pumps are checked at a minimum of 260 °C.
- Fuel loading and physical start-up: After the operating licence is obtained, real fuel is loaded. The reactor is brought to criticality for the first time at the lowest controllable power level, and the physical parameters of the core are measured.
- Power start-up: The turbine is rolled, the generator is synchronised with the grid and power is increased gradually; a separate test programme is applied at each power level.
- Trial and commercial operation: After stable operation at full power has been demonstrated for a certain period, the unit is put into commercial operation.
In Russian practice, step 5 is called physical start-up and step 6 power start-up. You will therefore come across the same terms in documents from Russian suppliers.
Who manages it, and who approves it?
The tests are carried out by the licence holder Akkuyu Nükleer A.Ş. and its contractors; the NDK inspects every critical step. The dummy fuel loading was also carried out under NDK supervision. Under the amendment of 2 October 2026 to the Regulation on Authorisations for Nuclear Facilities (Nükleer Tesislere İlişkin Yetkilendirmeler Yönetmeliği), the assessment of the operating licence also covers the final report of the commissioning tests. The regulation further stipulates that fuel may not be loaded into the reactor until the measures in the nuclear security plan have been implemented. Approval points in the tests work on the logic of hold points and witness points.
Why does logistics intensify during this period?
In commissioning, the challenge is not heavy cargo but time. A small seal or sensor that needs replacing during a test can halt the entire programme until a new one arrives.
- Spare parts: Sealing elements, filters, measuring sensors and valve parts must reach the site quickly.
- Chemicals: Some of the reagents used for water chemistry fall under dangerous goods rules and are transported under ADR.
- Temporary equipment: Test and measuring instruments often return to the manufacturer; the temporary admission procedure should be planned from the outset.
- Service teams: The tool kits and calibrated instruments of the manufacturer's specialists are separate shipments as well.
How does Voltim Global support this?
For an urgent sensor or seal arriving during the test period, it is not always possible to wait for a vessel departure. If a Ro-Ro sailing is not suitable, Voltim Global can switch the same cargo to the road route via Upper Lars–Georgia or via Iran and have the paperwork prepared while the vehicle is on the road. This flexibility is part of the Russia–Akkuyu supply line.
Frequently Asked Questions
When will Akkuyu Unit 1 generate electricity?
What is the difference between commissioning and commercial operation?
Is the cargo arriving at the plant during commissioning radioactive?
Sources
- World Nuclear News – Hydraulic tests completed at Turkey's Akkuyu 1
- Akkuyu Nükleer – Dummy fuel assemblies loading operation completed at Unit 1
- Akkuyu Nükleer – Commissioning permit for the first power unit received
- Resmî Gazete 02.10.2026 – Nükleer Tesislere İlişkin Yetkilendirmeler Yönetmeliğinde Değişiklik (amendment to the Regulation on Authorisations for Nuclear Facilities)