At the second power unit with VVER-1200 reactor of Leningrad NPP, the welding of the pearlite part and heat treatment of the joints of the main circulation pipeline (MCP) have been completed. All elements of the pipeline are interconnected and welded to the reactor shell, steam generators and main circulation pumps.

The general contractor’s specialists have handled this important heat installation in 85 days. This is 23 days less than it took to perform a similar operation at the first VVER-1200 power unit in 2015.

As the Chief Engineer of Leningrad NPP Alexandr Belyaev said, the shortening of the period for managing this work had been achieved due to several factors, including the availability of high-quality specialists who have experience in welding the MCP at the VVER-1200 power unit No 1, a clear organization of the entire process, welding and heat treatment, increasing the level of interaction between contractor’s assembly and welding departments. The management of Leningrad NPP played great part in the process by ensuring reliable functioning of the pipeline welding control system.

“The main emphasis in the course of the MCP welding was on the quality of the work. The main circulation pipeline is the equipment of paramount importance: in the process of operation, the coolant of the primary circuit will be pumped through it. Welded joints must withstand considerable temperature and hydraulic loads during the entire design life of the unit (60 years). And I am sure it will be so!” Alexandr Belyaev added.

At present, the work on the installation of the main circulation pipeline of the VVER-1200 power unit No 2 continues: the specialists apply special weldings to welded joints to protect them from corrosion and improve their strength characteristics. In addition, the specialists of the Metal Inspection and Technical Control Department of LNPP under construction, together with the general contractor specialists, test each individual welded joint using non-destructive methods (visual, measuring, radiographic, capillary and ultrasonic).

The tests are carried out according to the technological maps developed and approved by NIKIMT-Atomstroy JSC (main material science organization of Rosatom SC). According to Alexey Aksyonov, the Deputy Head of the Metal Inspection and Technical Control Department of Leningrad NPP under construction, as of today, 80% of welded joints have been tested. The high quality of their finish is fully confirmed.

It is planned that the entire amount of work on the main circulation pipeline will be completed by the end of this month.