Russian scientists have developed a new technology for the production of materials for creating elements of thermonuclear reactors, specifically components facing plasma in fusion power plants. With the help of 3D printing, specialists developed a composite of copper and tungsten, which combined the advantages of both metals. According to experts, the search for suitable materials is one of the most pressing issues in the development of thermonuclear plants, and their solution brings closer the era of thermonuclear energy.
Specialists from the National University of Science & Technology NITU MISiS (Natsionalnii Issledovatelskii Tekhnologicheskii Universitet MISiS (formerly Moscow Institute of Steel & Alloys – Moskovskii Institut Stali i Splavov) together with colleagues from the DV Efremov Institute of Electrophysical Apparatus (NIIEFA Nauchno Issledovatelskii Institut Elektrofizicheskoi Apparaturi), have proposed a new methodology for the production of materials for components facing plasma in thermonuclear reactors.
These are subjected to high temperature and exposure to hydrogen isotopes and special properties are required to withstand these. Hybrid technology, in additive production (3D printing) is combined with classic approaches, makes it possible to obtain a bimetallic composite from tungsten and copper with improved characteristics. It far exceeds the capabilities of currently used analogues.
“Research and development of new methods for the manufacture of tungsten parts is of high practical value,” said Stanislav Chernysheikhin, head of the laboratory for catalysis and processing of hydrocarbons at NITU MISiS. “The technology of selective laser melting (3D metal printing) is one of the most popular and applied methods for the additive production of metal products due to the possibility of synthesising complex parts with high resolution. The production of tungsten products using this method is a difficult task due to the high melting point and the formation of non-melting defects, microcracks and overheating of various components.”
Tungsten is considered one of the main materials for plasma-facing components due to its high melting point and other important characteristics. However, it is difficult to mechanically process due to its extreme hardness and fragility. To make a part of tungsten, classical powder metallurgy methods are usually used, but they do not allow the creation of complex products. Therefore, the traditional design of these elements is a simple multilayer design. Additive production makes it possible to synthesise the product in layers, including with a given porous structure, MISiS noted. The properties of such components can be adapted for a specific task by changing their geometric structure, experts explained.
The NITU MISiS team was able to obtain a relative density of continuous samples of 96.7% using laser synthesis. First, tungsten porous structures were made to create the composite by selective laser melting. Then copper was added to the matrix at temperatures up to 1,350 ° C. Having studied the wetting and kinetics of impregnation of tungsten matrices with copper, scientists established optimal conditions for this operation.
Pure tungsten is a fragile metal subject to minor deformations and cracks. However, mechanical tests showed that the resulting composite turned out to be much more plastic. “In the future, we plan to switch to the production of mock-ups of components facing plasma and heat-loaded cyclic tests. During the tests, impacts close to real operating conditions in thermonuclear plants will be modelled, Chernysheikhin said.
The choice of cladding material is one of the most pressing issues in the development of fusion plants. It must withstand huge flows of heat and particles, neutron damage occurs in reactor conditions, said Yuri Gasparyan acting head of the Department of Plasma Physics at the National Research Nuclear University (NRNU) MEPhI [Moscow Engineering & Physics Institute].
“Plasma-referred elements are usually created from several materials, which adds to the problem of their reliable connection. The new development by MISiS and NIIEFA using additive technologies makes it possible to create composite material from tungsten and copper and to achieve the benefits of each of the materials as well as to organise a special internal structure,” he added.
Much more work remains to be done to optimise the technology to reduce the porosity of the material and to study the functional properties of the material during thermal and plasma exposure. After that, it will be possible to talk more accurately about the prospects for this development, he noted.
According to the head of the expert analytical department for the fuel and energy complex at the Institute of Energy Strategy, Alexei Belogoryev, the development of solutions for fusion reactors is necessary, but their practical application is possible only after several decades. “All leading countries focused on space exploration are engaged in the creation of fusion reactors, since this type of energy is well suited for space flights. And if Russia wants to remain a leader in this area, then we need to develop technology. For civilian energy, fusion must be economically viable. In forecasts for 2050, none of the experts takes it into account, since the uncertainty associated with this approach is still very high,” he noted.
