This week, an important event took place that could potentially revolutionize energy – on July 28 in the south of France, scientists began assembling the international experimental tokamak ITER (International Thermonuclear Experimental Reactor), which should prove in practice the viability of the concept of a commercial thermonuclear reactor capable of generating more energy. what to spend. The official ceremony for the start of the ITER assembly on July 28, which was broadcast on YouTube, was attended by French President Emmanuel Macron and top officials of ITER partner countries.
Controlled Fusion is the Holy Grail of sustainable energy, a potentially unlimited source of clean energy. The technology is seen as a more efficient and safer alternative to nuclear power plants, which account for about 10% of the world’s electricity generation. Modern nuclear power plants are known to convert the thermal energy released during the decay of radioactive isotopes into electric current. Thermonuclear reactors, on the other hand, operate on a completely different principle, based not on fission, but on the synthesis of heavier elements from lighter ones. In the most general sense, such a scheme is analogous to the reactions taking place in the cores of stars. The main concepts are tokamak and stellarator. The main problem with such installations is the creation and maintenance of suitable conditions.
ITER is not the first experimental reactor, but the largest project of its kind. In total, 35 countries participate in it, including the USA, China, Great Britain, Switzerland, India, Japan, South Korea and 27 member states of the European Union. The ITER design is considered one of the most complex ever developed by man. The total mass of the reactor is estimated at 23 thousand tons. The installation itself will occupy an entire building. Work on this project began back in 1992, and the building permit was obtained 14 years ago. Preparatory work started in 2007 at the Cadarache research center, and at the end of May 2020, the base of a cryostat with a total mass of 1250 tons was lowered into the reactor shaft, which, in fact, is the starting point of the process of creating the reactor itself.
Internal structure of the ITER reactor
According to the scientific publication N + 1, ITER is a tokamak-type magnetic trap, in which a cord of deuterium-tritium plasma heated to several hundred million kelvin, located inside a vacuum chamber, is kept from expanding and touching the walls by a magnetic field of a certain configuration created by a superconducting system coils. Before starting work, the vacuum chamber is pumped out by a pump system, after which the working gas mixture is pumped into it. Then, with the help of an inductor, a breakdown of the gas mixture is created and a discharge is ignited, after which the plasma temperature begins to rise (an increase in the energy of ions and electrons) using a number of methods.
In the course of the reaction, the nuclei of deuterium and tritium merge together to form an alpha particle and a neutron, while 17.6 megaelectronvolts of energy are released, which is distributed between the reaction products. Alpha particles, gradually diffusing from the center of the plasma column to its periphery, eventually enter the divertor region, from where they are removed from the plasma. Neutrons enter the blanket, where they slow down, heating the coolant (water) or participate in the production of tritium from lithium. The entire vacuum chamber, together with magnetic coils, an inductor, pumping systems, fuel supply, plasma heating and diagnostics of its parameters, are enclosed in a cryostat, which plays the role of a supporting structure and a kind of vacuum thermos. The cryostat, in turn, is surrounded by concrete bio-shielding, several meters thick, to ensure radiation safety.
According to the plan, the completion of work and the receipt of the first plasma at ITER will take place in December 2025. At the same time, full-scale experiments with deuterium-tritium plasma will begin only in 2035, during which the reactor will have to hold the high-temperature plasma for 400 seconds and reach the full thermal power of 500 megawatts.
ITER is already five years behind schedule, and the current project cost estimate is three times higher than the initial one at € 20 billion.
It is important to note that the ITER unit will not be a power plant – it is intended solely for developing technologies, and the heat generated by it is planned to be dissipated. The next DEMO tokamak may become the first real thermonuclear power plant, but its construction will not be completed until 2040.
In recent years, there has been a surge in research in the field of thermonuclear energy. There are thermonuclear reactors of various designs in many countries of the world, including the USA, Germany, China and South Korea. If we talk about achievements, there are also a lot of them. In 2016, the team of the KSTAR (Korean Superconducting Tokamak Advanced Research) experimental reactor managed to set a new world record for plasma confinement – 70 seconds. Then, in 2017, the team of the Chinese experimental tokamak EAST managed to surpass this result by holding the plasma cord for more than 100 s. The British are also developing their own STEP (Spherical Tokamak for Energy Production) project, but its construction is planned only by 2040.
Source: Science Alert and N + 1