Leningrad NPP II Unit 2 with VVER-1200 has completed welding of the perlite section and heat treatment of butts of the main circulation pipeline (MCP). All pipeline components have been connected and welded to the reactor pressure vessel, steam generators and main coolant pumps.
Specialists of the general contractor did this thermal installation job for 85 days. This is 23 days less than required for such operation at Unit 1 in 2015.
Aleksander Belyaev, Chief Engineer of Leningrad NPP under Construction, said that these works had been shortened due to several factors: highly skilled workers who had MCP welding experience at Unit 1 (VVER-1200), clear-cut process, optimization of welding and heat treatment pre-heating operations, as well as enhancement of interaction between assembling and welding sections of the contractor. The Leningrad NPP Management executes controls over welding of the pipeline that played the critical part.
“During the MCP welding, the main focus was on quality of the work. The main circulation pipeline is the essential equipment. During operation it will pump the primary coolant. Welds must withstand significant temperature and hydraulic loads during the entire design service life of the power unit, which is 60 years. I am sure, so be it!” Aleksander Belyaev added.
At the present time, the installation work of the main circulation pipeline of Unit 2 (VVER-1200) continues. Specialists apply special overlays on welds to protect them from corrosion and improve strength characteristics. Besides, specialists of the metal flaw finding and technical control department of the plant under construction, jointly with the general contractor’s staff, inspect each separate weld by non-destructive techniques (visual, measurement, X-ray, dye penetrant and ultrasonic).
The inspection is carried out by process flow charts developed and approved by JSC NIKIMT-Atomstroy (leading material study organization of ROSATOM). Alexey Aksenov, Deputy Head of Metal Flaw Finding and Technical Control Department, said by date 80% of welds have been inspected and their high quality fully confirmed.
It is planned that the entire volume of works on the main circulation pipeline will be completed by the end of this month.