The melt trap housing has been installed in the reactor building of the unit 7 of Russia’s Leningrad NPP (also known as unit 3 of the Leningrad-II NPP). 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 units 1&2 with RBMK-1000 reactors, which were decommissioned in 2018 and 2020. New VVER-1200 units (7&8), now under construction, will replace units 3&4.
Specialists from general contractor Titan-2 installed the melt trap housing, weighing 157 tonnes into the reactor shaft. The task was completed almost a month ahead of schedule.
“By installing the melt trap housing in the design position, we have completed the last of the key tasks assigned to our team by industry management for the current year, noted Leningrad NPP Director Vladimir Pereguda. “But we do not plan to slow down, especially since we have several more stages ahead, when the remaining elements related to the trap will be installed. These include filler blocks, a service platform, a truss-console and a bottom plate with a total weight of almost 600 tonnes. The work ahead is large-scale and, given the importance of the trap for ensuring the safety of the power unit, very responsible…. There are qualified personnel, all the necessary resources and technical means to do this.”
Installation of the housing was completed in eight hours. The work was carried out using a heavy crawler crane with a lifting capacity of 2000 tonnes. About 50 specialists from the general contractor were involved in this operation. The progress of work was monitored by the inspection services of the NPP Titan-2, as well as employees of the Capital Construction Department and the reactor shop of the Leningrad-II NPP.
Installation required the highest accuracy: permissible deviations during installation of equipment were only a couple of millimetres. Considering the significant dimensions and weight of the housing, Titan-2 management used personnel with extensive experience in carrying out similar work Leningrad units 5&6 and at the reference units being built today in Turkey.
“We have carefully worked through all operations with surveyors, installers, crane operators, electric welders and concrete workers,” said Konstantin Khudyakov, Director of the programme for Leningrad facilities at Titan-2. “We have trained eight teams that will work in shifts. In total, this is almost 90 people, true professionals. Additional training was provided to those who will supervise this work and to those who will be involved in the manufacture, installation and dismantling of temporary building structures.”
The melt localisation device is not only the first large-sized component to be installed at Leningrad 7, but also one of its most important passive safety systems. In the event of a hypothetical accident with core melting, a device filled with a special sacrificial material will reliably hold the entire highly radioactive fuel melt until it completely cools, crystallises and reduces radioactivity and will ensure the safety of NPP personnel, people living near the plant and the environment.
