The power of the furnaces can be doubled (following the amendment of the Basic Law)

fusion nucleaire nouvelle limite greenwald puissance double tokamak couv

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Nuclear fusion is one of the most promising energy sources of tomorrow, especially in the context of a climate crisis. Physicists at the EPFL (Ecole Polytechnique Fédérale de Lausanne) have recently revised one of the basic rules for nuclear fusion, within a broader European collaboration, to the “Greenwall limit”. For three decades, this law has been the basis of plasma and fusion research, and also governs the design of mega projects such as the ITER (International Thermonuclear Experimental Reactor). A team of physicists has discovered that hydrogen injected into a thermonuclear reactor can produce twice as much energy. This finding redefines fusion limits, some experts believe First furnaces Profits for industrial use will only be available from 2040-2050.

The Nuclear fusion Combining the two atoms together releases a considerable amount of energy. This is the process that works within the sun. Hydrogen atoms combine to form helium atoms that heat up, making them heavier.

In France, in the Bouches-du-Rhône sector, 35 countries are involved in the construction of the largest Tokamak ever designed as part of the ITER project. Tokamak is a test engine designed to use fusion energy. In the case of a Tokamak envelope, the energy generated by the fusion of the nuclei is absorbed by the walls of the vacuum chamber, in the form of heat. Like conventional power plants, a fusion power plant uses this heat to produce steam, which then generates electricity through turbines and generators.

ITER aims to demonstrate that fusion – the “energy of the stars” – can be used as large-scale, CO2-free energy to generate electricity. Its primary purpose is to create high-temperature plasma that provides an environment conducive to fusion and energy production. The results of the ITER science project will be crucial in paving the way for tomorrow’s power generation fusion power plants.

As part of the continuous improvement of these reactors, EPLF physicists revealed that, under complete protection, higher amounts of hydrogen could be used, thereby obtaining more energy than possible. This revision of the Greenwall range will be implemented for testing while the ITER reactor is in operation. The new equation, which improves this range, has been published in the journal Physical Review Letters.

New range for Tokamas to produce clean energy in the future

Scientists have been working for more than 50 years to obtain a potentially controlled fusion. Unlike nuclear fission, which produces energy by breaking up very large nuclei, nuclear fusion can generate more energy by fusing smaller molecules. In addition, the fusion process produces far less (almost none) radioactive waste than fission, and more hydrogen-rich NeutronsUsed as a fuel, it is relatively easy to obtain.

As mentioned earlier, the nuclear reaction here is similar to the reaction that takes place inside the sun using hydrogen atoms. On Earth, however, the pressure at the heart of a star cannot be regenerated. This pressure is required to convert hydrogen into plasma – the medium by which hydrogen atoms can melt and generate energy. Therefore it is necessary to bring the gases to a temperature 10 times higher than the sun, i.e. about 150 million degrees Celsius.

As a result, under the influence of extreme temperature and pressure, hydrogen gas is transformed into plasma at the heart of a tocopherol formed by a loop-shaped vacuum chamber. In the enclosure, the energy generated by the fusion of the nuclei is absorbed in the form of heat by the walls of the vacuum chamber. Very strong magnetic fields are used to control and regulate plasma.

tokomak cut iter
Simplified area of ​​the reactor with a loop-shaped vacuum chamber. © US ITER

Many fusion power projects are now a Advanced status. Nevertheless, ITER is, in essence, not designed to produce electricity, but to test production limits and define the optimal conditions for carrying out such fusion reactions. However, ITER-based tokamakes, also known as demo furnaces, will be operational by 2050 to produce electricity.

Palo Ricci from the Swiss Plasma Center (EPFL) explains Was contacted : ” To create plasma for fusion, three components must be taken into account: high temperature, high density of hydrogen and a good seal. This is why one of the limitations of plasma production at Tokama is the amount of hydrogen injected into it. In fact, the higher the density, the more difficult it is to keep the obtained plasma stable.

More precisely, as more fuel is injected at the same temperature, certain parts of the plasma become cooler, and it is more difficult for current to flow through the latter, thus causing disturbances. Paulo Richie explains in simple words: “ We lose control completely and the plasma goes nowhere. In the 1980s, we tried to find a kind of law that would allow us to predict the maximum concentration of hydrogen that could be injected at Tokamak. “It was discovered by physicist Martin Greenwall in 1988 and establishes a correlation between the density of the fuel, the small radius of the Tokamak (the radius of the inner circle of the ring) and the current circulating inside the plasma. It is at the heart of the ITER construction strategy.

Plasma history

Scientists have long doubted that the Greenwald range could be improved. To test their hypothesis, the Swiss Plasma Center, in collaboration with groups of other Tokamas, designed and conducted a revolutionary experiment that enabled the use of highly sophisticated technology aimed at precisely controlling the amount of fuel injected at Tokama. Massive tests have been carried out on the world’s largest tokamaks, the Joint European Torus (JET) in the UK, the ASDEX upgrade in Germany (Max Planck Institute) and the TCV tokamak in the EPFL.

At the same time, Mauricio Giacomo, a doctoral student in Paulo Richie’s group, began to analyze the physics processes that control density at Tokamax in order to establish a basic law that allows the correlation of fuel density and Tokomac size. Part of this work involves advanced plasma simulation performed using a computer model.

It is important to find that plasma supports higher fuel densities as the energy output of the fusion reaction increases. In other words, Tokomas like ITER can use almost twice as much fuel to produce plasmas. Paulo Ricci says: This result is important because it shows that the attainable density at Tokamak increases with the force required to drive it. The demo operates at significantly higher power than the current tokamaks and ITER, which means it can add more fuel density without restricting production contrary to the intent of Greenwall’s law. That is very good news “.

Source: Physical Review Letters

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