Construction of inner containment begins at Unit 4 of Leningrad Nuclear Power Plant II

Construction of the inner containment of the reactor building at Unit 4 of the Leningrad Nuclear Power Plant II in Russia has commenced. The unit features a VVER-1200 reactor, and the inner containment is a key component of the unit's passive safety system, as well as part of the plant's confinement safety system.

Construction workers have installed the first tier of vertical sealed steel liner to its design position. The steel structure weighs approximately 97 tonnes, and the lifting and positioning operations were carried out using a heavy crawler crane, with the entire installation process lasting about 7 hours. The contractor, TITAN-2 Holding Company, stated that the preparatory work took several months, including component fabrication, protective coating application, on-site assembly and welding, and structural quality inspection. After the steel liner was positioned, the constructor also rechecked its planar and elevation coordinates.

According to the construction schedule, over the next week, workers will weld the installed vertical steel liner to the embedded parts within the floor slab of the reactor building's annular gallery, and then weld it to the horizontal sealed steel liner at the foundation level, closing the sealed contour from below.

The project team stated that the installation of the first tier of sealed steel liner is only the first step in the construction of the inner containment. Manufacturing of the second tier of inner containment components has already begun, with installation planned for completion within the year. Thereafter, the steel structure will be erected tier by tier upward until the top elevation of the reactor building dome, forming a closed sealed space at the upper part. On the outside of the steel liner, a wall composed of rebar and special concrete will be poured, further reinforced with steel tendons to meet the containment functional requirements of the reactor building under various operating conditions.

All construction work on the inner containment of Unit 4 at Leningrad Nuclear Power Plant II is scheduled for completion in 2029, with the outer containment planned for completion in 2030. The outer containment is primarily designed to withstand external impacts caused by natural and man-made factors.

Units 3 and 4 of the Leningrad Nuclear Power Plant II both feature VVER-1200 reactors and are scheduled to commence operation in 2030 and 2032, respectively. Once the two new units are completed, they will replace some of the older units using RBMK-1000 reactors, providing electricity to the northwestern region of Russia.

The VVER-1200 is a Generation III+ improved pressurized water reactor design from Russia, equipped with both active and passive safety systems. Its double-layer containment structure consists of an inner containment and an outer containment: the former ensures the tightness of the internal space of the reactor building, while the latter enhances the reactor plant's ability to withstand external events. The Leningrad Nuclear Power Plant is located on the coast of the Gulf of Finland near the town of Sosnovy Bor in Leningrad Oblast, Russia, and is currently one of the largest nuclear power plants in Russia by installed capacity.