Main complex completed in China’s ‘artificial sun’ project: Assembly phase begins at BEST reactor

A significant milestone has been reached in BEST, one of China’s next-generation projects in the field of controlled nuclear fusion. The main complex of the reactor, which is being built in the city of Hefei and is publicly known as an “artificial sun,” has been completed; this marks the transition from the building construction phase to the assembly of reactor components.

BEST, an acronym for Burning Plasma Experimental Superconducting Tokamak, is seen as one of the critical projects in China’s goal of moving fusion energy from laboratory scale to power generation demonstration. The work, which began in 2023, is planned to be completed by the end of 2027.

Images released on October 1 revealed that the facility’s main complex is complete and has entered the operational phase. Since July, the reactor’s core components—the vacuum vessel, cold shield, and toroidal field magnets—have been transported to the facility. It was reported that the assembly of the four-part vacuum vessel has been completed and the first toroidal field magnet has undergone testing.

PLASMA IS HEATED TO OVER 100 MILLION DEGREES

What distinguishes BEST from previous experimental setups is its goal of not only producing high-temperature plasma but also researching “burning plasma” conditions using hydrogen isotopes called deuterium and tritium. The project aims to reach a fusion power between 20 and 200 megawatts and to demonstrate that the fusion reaction produces more energy than is spent to heat the plasma.

Nuclear fusion is based on mimicking the Sun’s energy production mechanism on Earth in a controlled manner. While fission, used in current nuclear power plants, involves splitting atomic nuclei, fusion involves the merging of light atomic nuclei, a process that releases large amounts of energy. However, for this to occur, the plasma must be heated to over 100 million degrees and confined in a stable manner.

In tokamak-type reactors, this task falls to powerful magnetic fields. In BEST, superconducting magnets will keep the extremely hot plasma away from the reactor walls. While the main section where fusion reactions will take place operates under high vacuum, the cold shield will provide thermal insulation between the magnets, which must operate at approximately minus 269 degrees Celsius, and the plasma, which reaches millions of degrees.

When the deuterium-tritium fuel mixture merges under appropriate temperature and density conditions, a helium nucleus and a high-energy neutron are produced. The released energy contributes to maintaining the plasma’s temperature, allowing for the study of conditions under which the reaction can sustain itself.

Although the completion of the main complex is an important engineering milestone, the most challenging part of the project will be assembling the reactor’s sensitive systems in the correct order. The success of BEST will not mean a commercial fusion power plant; however, it will form an important experimental stepping stone for continuous and larger-scale fusion power systems.