The DV Efremov Institute of Electrophysical Apparatus (NIIEFA Nauchno Issledovatelskii Institut Elektrofizicheskoi Apparaturi), part of Rosatom, has manufactured and tested a high temperature superconductor (HTSC) wire for the electromagnetic system (EMS) of the TRT (tokamak with reactor technologies) reactor being developed by NIIEFA.
“The department of cryogenic technology and applied superconductivity … produced a full-size piece of wire 5 metres long, which consists of 240 HTSC tapes placed in a copper stabilising matrix,” explained Andrey Mednikov, head of the research department of superconducting systems. “Inside the matrix there is a channel for pumping refrigerant at a temperature of 5-20 Kelvin [approximately minus 268 to minus 253 degrees C]. On the outside the structure is protected by a durable casing made of high-strength stainless steel. In fact, this is a short version of the wire that will be used in the installation to carry a current of up to 65 kA [kiloamperes] in a magnetic field of approximately 18 Tesla [a measure of magnetic field strength]. Such record parameters have never been achieved before.”
The sample was tested at liquid nitrogen temperature. It was found that after cooling to a temperature of about minus 196 °C, the wire went into a superconducting state. An operating current was introduced into the sample, the limiting (critical) value of which was calculated based on the initial characteristics of HTSC tapes. The condition of the wire was monitored using diagnostic lines, and all parameters were recorded on a special measuring stand.
“For comparison, the low-temperature superconductor for the International Thermonuclear Experimental Reactor (ITER) was made from niobium-titanium (NbTi) and niobium-tin (Nb) wires, operating at a temperature of about 4.5 Kelvin, a magnetic field of up to 8 and 13 Tesla, respectively, a current of up to 48 and 68 kA, respectively, with dimensions of about 54×54 mm. The wires developed for TRT will be made from yttrium–barium copper oxide tapes operating at temperatures of 5-20 Kelvin, magnetic fields up to 20 Tesla, currents up to 80 kA, and measuring about 26×26 mm. Thus, TRT wires will be made of fundamentally different materials and will be superior to ITER wires in most characteristics,” Mednikov said.
NIIEFA said a number of studies important for the project can be carried out at temperatures of around minus196 °C although the operating temperature in the TRT is expected to be minus 250 to minus 270 °C). This will significantly reduce the cost and simplify testing, and will also allow testing of a larger number of samples in less time, which will reduce the development time of the TRT tokamak.
In 2026, it is planned to manufacture and test two more wires, each more than 60 metres long (in total, the TRT is expected to use several tens of kilometres of wire and more than 30 coils of various sizes). And in 2027, these wires will be used to make a full-scale mock-up coil of the central solenoid with a diameter of about one metre, consisting of 40 turns laid in two layers.
The preliminary design work for the TRT began in 2022 based among other things, on experience and knowledge gained from participation in the international ITER project. A concept paper describes the project as being “developed to facilitate fast and economically sound transition to the pure fusion reactor as well as to the fusion neutron source for a hybrid fusion-fission system”.
The project, led by Rosatom’s Department of Scientific & Technical Programmes & Projects, is part of the Comprehensive Programme for the Development of Engineering, Technology & Scientific Research (RTTN – Razvitii Tekhniki Tekhnologii I Nauchnikh Issledovanii) in the field of the use of atomic energy in the Russian Federation.
TRT will be built at the Troitsk Institute of Innovative & Thermonuclear Research (TRINITI) site where the TSP strong-field tokamak is now located. The TSP tokamak began operation in 1987 but was suspended due to lack of funds following the collapse of the USSR. It has four satellite buildings with auxiliary infrastructure. Major reconstruction is planned as part of the RTTN programme.
TRINITI is now preparing the necessary infrastructure for TRT construction. TRT will be used to study plasma behaviour in quasi-stationary modes close to ignition and improve methods of additional plasma heating, fuel supply, and blanket technologies. The device will also be helpful in developing new diagnostic techniques and tritium technologies.
