The melt localisation device (ULR – Ustroistvo Lokalizatsii Rasplava) has been delivered to Leningrad NPP for unit 7 from Tyazhmash in Syzran, Samara Region. 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.
The melt trap, a unique Russian technology, is one of the passive safety systems of the VVER-1200 generation 3+ project. In the event of a hypothetical accident with melting, the core trap – filled with a special sacrificial material – will reliably hold the entire highly radioactive fuel melt until it completely cools and crystallises, eliminating its contact with the environment.
“One of the most important functions of the trap is to ensure the subcriticality of the melt: molten fuel and debris from reactor structural elements under conditions which make the formation of a chain reaction will be impossible. It is also important that the capture into the trap will occur without the participation of nuclear power plant personnel, but only under the influence of gravity. This is precisely what determines the passivity of the system”, explained the acting head of the reactor shop of Leningrad NPP-2 Oleg Mukhin.
The melt trap travelled more than 2,000 kilometres to Sosnovy Bor. The total weight of the cargo is more than 730 tones. “Natural waterways and canals were used to transport the large cargo,” said Evgeniy Milushkin, Deputy Director for Capital Construction and Head of the Capital Construction Department at Leningrad-II. “We have repeatedly used this delivery method during the construction of the first two Leningrad-II units power units ith VVER-1200 reactors, since it has a number of advantages. For example, there is the large carrying capacity of water transport and the large carrying capacity of the deep-sea routes, as well as the economic efficiency of such transportation and no need to use specialised vehicles and infrastructure.”
During the last stage, the URL will be transported by road to the construction site where it will undergo an acceptance control procedure before being installed in the reactor shaft of unit 7, which is planned to be completed by the end of November.
