Material scientists from NUST MISIS commissioned by JSC Atomenergoproekt have started to carry out certification studies of the existing material and select a new one for the manufacture of a “melt localization device” — a capsule located in the containment building of nuclear reactors — for the largest domestic and foreign projects of Rosatom Corporation. The melt localization device is one of the nuclear safety passive protection systems and provides isolation of the foundation and soil from the corium — the melt of the reactor vessel and its core — in case of man-made accidents.
At present, Russia is building nuclear power plants in Turkey, Finland, China, Belarus, India, Bangladesh, etc. Rosatom’s foreign orders portfolio includes 36 power units. Additional passive protection systems, the so-called “melt containment devices”, are planned to ensure the increased safety of generation 3+ reactors.
A melt localization device (“melt trap”) is a steel capsule with a special filler located in the containment building of a nuclear reactor, designed to localize the melt of a nuclear reactor vessel, internals and the core of a nuclear reactor in severe accidents, which provides soil and foundation isolation, and also cools the melt.
In the event of a severe loss of coolant accident — as in the largest incidents at the Chernobyl and Fukushima nuclear power plants — the reactor vessel can melt. In this case, the remnants of the core radioactive toxic materials fall into this trap, where they are cooled to temperatures at which the rescue teams will be able to work.
Specialists of the Department of Metallurgy and Strength Physics at NUST MISIS, together with the Hybrid Nanostructured Materials Research Laboratory, are working on a project to select a new material for the melt trap, which will guarantee the required performance of the reactor, including extreme modes.
In Russian protection systems, a “melt trap” is built directly under the reactor (at the bottom of the mine) and is a cone-shaped metal structure with a total weight of about 750 tons. The trap is filled with a special, so-called “sacrificial material” (filler), consisting mainly of iron and aluminum oxides. The filler is dissolved in the fuel melt to reduce its volumetric energy release and increase the heat exchange surface, and water fills this mass through special pipelines in the trap body.
“In our laboratory, we managed to simulate the emergency operation of a nuclear reactor and track the behavior of various materials proposed for making a trap, — explained Alexander Komissarov, head of the Hybrid nanostructured materials laboratory. — Analysis of the materials’ behavior will make it possible to calculate the minimum level of strength of the trap case, which ensures guaranteed and safe elimination of the consequences of the reactor core melting. The trap is capable of preventing the grave consequences of an accident at a nuclear power plant, but I am sure that with the development of today’s nuclear safety technologies, it will never have to be used.”