Rosatom has delivered the first large component – the melt trap (ULR – Ustroystvo Lokalizatsii Rasplava) – to the construction site of the Paks II NPP in Hungary. The manufacture of the core melt localisation device was completed in Volgodonsk, Russia, in March after specialists from Atomstroyexport (ASE – part of Rosatom’s Engineering Division and general contractor) and representatives of the Hungary’s Paks II finalised acceptance checks. Production was constantly monitored by Hungarian experts including officials of the National Atomic Energy Authority.
The 730-tonne cone-shaped device, manufactured using thermally resistant steel has a maximum diameter of 11 metres and a height of more than 15 metres. It is the most important element of the passive safety system of generation 3+ NPPs. The ULR is installed at the bottom of the concrete reactor shaft directly below the reactor vessel and is capable of containing the melted core in the event of a breach. It helps to reduce hydrogen production and the release of radioactive material into the environment. The vessel contains a fusion charge containing alumina and iron oxide, which when mixed with the core melt, reduces its specific heat.
The device was transported by water in a journey that covered a total of 3,200 kilometres via the Black Sea and the Danube River, and took 48 days to complete. Hungary’s Foreign Minister Peter Szijjártó commented: “Typically, an international project involves international transport and this was no exception. The transport was organised by an Austrian company, and the melt trap arrived in Paks on a Slovakian ship.”
The Paks II project was launched in 2014 by an inter-governmental agreement between Hungary and Russia for two VVER-1200 reactors to be supplied by Rosatom. The contract was supported by a Russian state loan to finance the majority of the project. The Hungarian Atomic Energy Authority issued the licence for the units in August 2022. The Paks NPP comprises four VVER-440 power units. Paks currently provides half of all generated and one third of the consumed electricity in Hungary.
Preparatory work for the construction of unit 5 (also known as Paks II unit 1), for which the melt localisation device is intended, is on schedule. Currently, soil strengthening is being completed, and preparations are underway for excavating soil from the pit to the design level of 23 metres, which is required for the start of preparation of the foundation slab or the new power facility.
“It is deeply symbolic that the first large-sized equipment that arrived at the Paks II NPP construction site is an element of the plant’s safety systems,” noted Vitaly Polyanin, Vice President of ASE JSC and Director of the Paks NPP Construction Project. “The reliability and safety of the new Hungarian NPP is thus ensured long before operation begins. We are making every effort to be able to start building the power units and subsequently installing the molten core catcher – an important element of the passive safety of the new Hungarian NPP – at the end of this year or the beginning of next year.”
Paks II NPP is an international project. As well as Russian and Hungarian companies, European companies and companies from third countries are also working at the construction site. “Our common goal with the general contractor is to build a safely operating nuclear power plant in the shortest possible time.” said Gergely Jakli, President and CEO of Paks II. Zrt. “We have passed important milestones: last year we completed the construction of a 2.7-kilometer impervious curtain, soil stabilisation continues, and excavation to the design level began with testing. We are increasing the pace of work on the site and in the area of the construction and installation base. There are currently 900 specialists working on site.”
