In fast neutron reactors helium and hydrogen are formed in the result of transmutation reactions in the structural materials. Austenitic steel, used for the manufacture of fuel claddings of fast reactors, does not provide a burnup of heavy atoms in the fuel more than 12-13% due to the high level of radiation swelling. MEPhI is working on the search for promising materials that could replace this steel.
Associate Professor of the Department “Physical problems of materials science” Maxim S. Staltsov won the competition for a scholarship of the President of the Russian Federation for young scientists for 2016-2018 for the project “Regularities of gas and vacancy porosity development in promising vanadium alloys under simulation ion irradiation of various masses and energies”. “Our task is to conduct a preliminary selection of new materials for thermonuclear fusion reactors and fast neutron reactors. We conduct the first assessment of the possibility of their application in reactors in relation to swelling”, said Maxim Sergeevich.
Constructional materials with body-centred crystal lattice may be promising for fast reactors of the new generation. As the head of the Center “Nuclear systems and materials” B.A. Kalin said, alloys of vanadium are alternative material for ferritic-martensitic steels, and the Center conducts study of their swelling in relation to fuel pin claddings of fast neutron reactors. “They combine high high-temperature strength and resistance to swelling. Maxim’s work will let to obtain new knowledge on vanadium alloys”, he stressed.
The materials of the reactor’s first wall will exercise impact of ions and atoms of helium and hydrogen, and neutrons. Vanadium alloys are considered as candidate materials for the body of the discharge chamber of a thermonuclear reactor. They will be able to work in an environment of large neutron flux, which enable the formation of high density of defects and production of significant quantities of transmutation gases, as well as gases implanted from plasma, which will result in vacancy and gas swelling of the materials. “It is known that pure vanadium is characterized by a high gel swelling, but it can be reduced through alloying, for example, Ti or Fe. However it exerts negative effects on some other properties of vanadium. It is planned that this work will investigate the effect of alloying by such elements as Ta, W, Cr, and double alloying on the ability to suppress helium swelling of vanadium”.
Another problem is assessment of radiation resistance of materials under simultaneous accumulation of helium and radiation action, which damages the structure of the metal. One way to solve this problem in such conditions is the simultaneous or sequential irradiation by heavy ions, which allows to simulate the neutron irradiation, and helium ions. “Our work reveals the regularity in vacancy and gas swelling of vanadium alloys depending on chemical composition during the simulation experiments on the irradiation of ions of various masses and energies. We have to establish the relative resistance of vanadium alloys against radiation swelling”, said Maksim Sergeevich.
The task of research is achieved by conducting simulation experiments on the implantation of heavy ions in the ion accelerators. The main method of swelling studying is transmission electron microscopy. According to Maxim Staltsov, this work will result in recommendations on creation of radiation-resistant vanadium alloys.
