At the construction site of the Kursk NPP-2 in the reactor building of the 2nd power unit, one of the key events was completed – welding of the main circulation pipeline (MCP), which connects the main equipment of the reactor plant into a single technological system, forming the 1st circuit.
The main purpose of the MCP is the circulation of water in the 1st circuit from the reactor to the steam generators. At the stage of industrial operation of Kursk NPP-2, coolant with a temperature of up to 330 degrees will circulate in the main circulation center.
The MCP consists of 20 blocks with a total mass of more than 250 tons, which are assembled by welded joints. On power units of the PWR-TOI type, the main circulation pipeline is connected by 32 joints. In other projects, for example PWR -1200, there are 28 welded joints. This difference is due to the location of the steam generators relative to the reactor vessel in a sealed volume - in connection with this, the number of blocks has increased by 4. The wall thickness is 70 mm - this is the main difficulty in welding work.
The schedule allocated 70 days to complete this technological operation, but welding and heat treatment of all welded joints were completed in 50 days - this is an absolute record. A similar operation at Unit 1 was completed last year in 55 days. Such a record reduction in time is associated with competent preliminary preparation, optimization of the work schedule, as well as with the parallel implementation of several processes - specialists of Energospetsmontazh JSC took into account the previously gained experience in welding the main circuit at power unit No. 1 of Kursk NPP-2 and other nuclear power plants.
“Welding of MCP is a large complex of related work. Preparations for implementation begin a year in advance. We try to provide that welders do not change and are present from block to block. This gives us confidence in the high quality of the work, and their experience guarantees a reduction in welding time - we confirmed this today,” said Ildar Tleubaev, director of the MSU-5 branch of Energospetsmontazh JSC.
During the welding process, specialists performed step-by-step control of all operations performed: visual, measuring, radiographic, capillary and ultrasonic. The quality of the seams meets all the requirements in nuclear energy.
“Completion of the MCP welding opens up the possibility of starting the installation of safety systems and other technological systems that are adjacent to them. In fact, preparations are beginning for the upcoming key event - the beginning of the spill of safety systems into the open reactor,” said Oleg Shperle, vice-president of Atomstroyexport JSC, director of the project for the construction of Kursk NPP-2.
For reference:
The Kursk NPP-2 is a replacement station that includes 2 units with a capacity of 1255 MW each. The construction of power units No. 1 and No. 2 of the replacement station Kursk NPP-2 is carried out within the framework of the Federal project “Design and construction of reference power units of nuclear power plants” of the Comprehensive program “Development of equipment, technologies and scientific research in the sphere of use of atomic energy in the Russian Federation for the period until 2024.
The Russian nuclear industry has transformed from a piece manufacturer into a conveyor of nuclear technologies, a “reactor factory,” which allows Russia to occupy a leading position in the world in the export of nuclear technologies. Today, the share of power generated by nuclear power plants in Russia’s energy balance is about 20%, and by 2045 it should reach 25%. This instruction was given to the State Corporation Rosatom by the President of Russia.

Source: Press service of Electric Power Division of ROSATOM