The bottom plate, the last element of the melt localisation device (melt trap), has been installed in the reactor building of Leningrad NPP unit 7 (also known as Leningrad-II unit 3). The equipment weighing 120 tonnes was installed in a concrete reactor shaft supported on a console truss. General Contractor Titan-2 specialists completed the complex operation in one work shift.
Currently Leningrad NPP has four units in operation – units 3&4 with Soviet RBMK-1000 reactors, as well units 5&6 with new VVER-1200 units (also known as Leningrad-II 1&2). Units 5&6 replaced the RBMK-1000 reactors at units 1&2, which were decommissioned in 2018 and 2020. New VVER-1200 units (7&8), now under construction, will replace units 3&4.
The Melt trap consists of several pieces of large-sized equipment and blocks filled with special material. Each of them has its own special function; together they ensure the highest level of safety of the power unit for NPP workers, the population living nearby and the environment in the event of an unlikely hypothetical accident.
“The likelihood that someday this passive safety system will actually be required is extremely low,” said Alexey Mochalov, Deputy Chief Engineer of Leningrad-II. “All decisions made in the design of domestic power units with VVER-1200 reactors, the high-quality construction, installation and commissioning work, as well as the qualifications and responsibility of nuclear plant personnel will leave the trap for the entire design life of the unit in standby mode.”
Konstantin Khudyakov, Director of the program for Leningrad NPP facilities at Titan-2 noted: “Today, the unit 3 reactor shaft is 55% ready and filled with almost 900 tonnes of equipment. However, the most important operations of this key building structure are still ahead. In future, we will install thermal insulation, support and thrust trusses, and other equipment, install measuring channels, concrete the shaft to the design height, in order to install the reactor vessel next year. Now more than 1,400 people and 190 pieces of equipment are working at 53 facilities on the construction site. The work is progressing on schedule, some ahead of schedule.”
