Main coolant pipeline (MCP) welding started at Akkuyu
NPP Unit 2 (being built by Rosatom).
During the process, specialists are going to weld 32 pipeline joints and install about 260 tons of pipes and metal structures. The works are being performed using a proven technology, and observing the quality requirements and safety standards. Welders, fitters, flaw detection and heat treatment specialists, as well as quality control department employees are engaged in the works.
The process stages are performed in a strict sequence. All the inspection results are documented. High-grade professionals only, who have passed special training and qualification, perform MCP welding. Every welded joint has marking that to track all the history of manufacture, inspections and acceptance. The information on all jobs performed is recorded in the as-built documentation and is kept along the entire power unit life cycle. Following the welding completion, every joint undergoes a series of inspections, applying various test methods, including ultrasonic, penetrant, and radiographic ones.
"Welding of the main coolant pipeline relates to the most essential operations during the power unit construction. There are special requirements for the materials and work performance technology and for the personnel's qualification as well. A big team of professionals contributed their efforts into every welded joint. Every joint undergoes a multi-stage inspection, with all work stages being documented. Such an approach ensures a high level of the primary circuit equipment reliability throughout the NPP operation life", Akkuyu Nuclear JSC Chief Executive Officer Sergei Butckikh noted.
The next stage is heat treatment of welded joints at a high temperature, which allows for the internal metal stress relief and provision with the required performance characteristics of the pipeline. Special corrosion-protection deposition is made on the internal surface of a welded joint at the final stage of welding.
The main coolant pipeline is the key component of a
reactor plant. Demineralized water with the temperature of up to 330 Co
at the pressure of about 160 atmospheres will circulate in the pipeline during
operation; this is why the quality of installation and welded joints matters
that much. The total length of MCP pipes exceeds 150 meters; the
wall thickness is 70 millimeters. The main coolant pipeline is intended for the
coolant circulation between the reactor, steam generators and reactor coolant
pumps. In the process of power unit operation, the primary
circuit coolant transfers thermal energy through the heat exchanging surfaces
of steam generators to water of the secondary circuit, where steam is generated
for the turbine generator operation.
Akkuyu NPP is the first nuclear power plant being built in the Republic of Türkiye. The Akkuyu NPP project includes four power units equipped with Generation 3+ VVER reactors of Russian design.
The capacity of each power unit is 1200 MW. Akkuyu NPP is the first project in the global nuclear industry being implemented according to the Build-Own-Operate business model.
