This was the final reactor assembly stage prior to the hydraulic tests performed to check reactor unit strength and consistency.

The assembled upper block weighs 138 tonnes. As all the rest reactor pressure vessel components, it was moved to the cavity with the polar crane. Upon upper block installation, JSC MSU-90 specialists commenced main reactor joint sealing with steel studs. Driving of studs and main reactor joint tensioning are performed using special high precision tool - wrench.

JSC Titan-2 Holding employees have been assembling the reactor since February. All the core internals were delivered to the site and lifted to the +26.000 elevation of the reactor building. Since the delivery, they underwent depreservation, tilting, installation into the inspection cavity. Assemblability of the reactor was checked.

“After installation of the upper block, primary circuit from the reactor side will be fully sealed. Therefore, we will be able to fill it with water and increase the pressure up to testing parameters”, - noted Alexander Kotelnikov, JSC MSU-90 Deputy Head of the Nuclear Island Department.

Furthermore, MSU-90 specialists are preparing the main circulation pumps for start-up and flushing. One of the pumps has already been rotated at idle speed. The second circuit pipes, ventilation systems and auxiliary equipment are also under installation.


Titan-2 Holding is the largest in the North-West group of companies, constructing the most important nuclear industry and power facilities. The company performs a full range of construction and installation works from engineering to commissioning.

Titan-2 Holding is the general contractor for the construction of the Leningrad NPP-2 power units. The Holding Companies perform all the civil, installation, and electrical works at a construction site. The works are carried out in the reactor, turbine, power supply, water supply, heat cogeneration buildings and other power unit structures.