American researchers’ major breakthrough in nuclear fusion: Achieving a net energy gain

Scientists have just announced a breakthrough in the field of nuclear fusion ignition. In this news, it was announced that for the first time in the heart of a powerful fusion reactor, the energy produced for a short time was more than the energy consumed. However, experts look at this news with caution and believe that although the recent progress is very important, we still have a long way to go before reaching safe and unlimited nuclear fusion energy.

Yesterday, Tuesday, physicists at the National Combustion Facility (NIF) at Lawrence Livermore National Laboratory in California announced that they were able to fire a laser carrying approximately 2 megajoules of energy into a fuel ball composed of two hydrogen isotopes, turning the atoms into plasma and at a 50 percent increase. produce 3 megajoules of energy.

Scientists are excited about the results, but refrain from exaggerating about them too much. In fact, the reactor in question is a general unit Net energy gain (that is, the released energy is more than the consumed energy) has not reached. For a fusion reaction to be truly useful, the tens of megajoules of energy drawn from the power grid and converted into laser beams fired into the reactor core must be significantly less than the energy released from the plasma.

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The recent breakthrough in plasma ignition involves only the input laser energy and the output plasma energy, and in the meantime, ignores significant losses from the conversion of electricity to light.

Furthermore, the above reaction takes place in a tiny pellet of fuel inside the world’s largest laser, lasts only a few billionths of a second, and can only be repeated every six hours. These limitations make the reaction very inefficient for practical purposes.

Ian Lowe, physicist and professor emeritus at Griffith University in Australia, believes that “achieving net energy gain is the turning point of consumption; But if we take a further look, we’ll see that fusion is where it’s at right now Enrico Fermi About eighty years ago, it was with the nuclear fission operation. The big technical problem is keeping the plasma mass at a temperature of several million degrees to enable fusion while still extracting enough heat to provide useful energy. “I have yet to see a valid schematic diagram of a fusion reactor that achieves this.”

NIF laser

National Ignition Facility (NIF) laser locators target.

How do fusion reactors work?

Existing fusion reactors can be divided into two general categories:

  • Bare confinement fusion reactors such as NIF contain plasma heated by lasers or particle beams.
  • Magnetically confined reactors such as the Joint European Project Taurus (JET) in the United Kingdom, the International Thermonuclear Experimental Reactor (ITER) in Europe, and China’s Advanced Superconducting Tokamak (EAST) that shape plasma into various torus-like shapes with strong magnetic fields. The field that confines the burning plasma in Project Ether will be 280,000 times stronger than the magnetic field around Earth.

Different types of reactors employ different strategies to overcome the daunting technical hurdles of fusion. The purpose of magnetically confined reactors, known as tokamaks, is to keep the plasma burning continuously for long periods of time. For example, the goal set in ITER is to do this within 400 seconds. With all the progress and despite approaching the desired limits, tokamaks have not yet been able to produce a net benefit from their plasma.

On the other hand, bare confinement systems such as the NIF reactor, which are also used to test nuclear thermal explosions for military purposes, produce bursts of energy by rapidly burning small pellets of fuel in rapid succession. However, we must note that the fuel used in these systems comes in the form of individual pellets, and scientists have not yet been able to find a way to quickly replace them and maintain the reaction for longer than the smallest fraction of a second. Yves Martinvice president of the Swiss Plasma Center at the Polytechnic Federal Center of Lausanne, points out:

This is very difficult because we need to be able to shoot the next bullet when the cloud [پلاسما] It is expanding inside the chamber, let’s place it. The diameter of this bullet is usually one millimeter and it should be placed in a room with a width of 9 meters. As far as I know, each bullet still costs tens of thousands of dollars to make, and why [در عمل] To become an interesting idea, the total cost should be reduced to a dollar or even less.

Very expensive isotope

Another problem facing fusion reactors is the depletion of tritium reserves. Tritium is the key isotope that combines with deuterium as the reaction fuel. Tritium was once a common and unintended byproduct of open-air nuclear weapons testing and nuclear fission. Tritium’s half-life of 3.12 years means that many of its existing reserves are already on their way to being unusable, making tritium one of the most expensive materials on Earth at $30,000 per gram.

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Physicists have proposed other methods for making tritium; Methods such as growing this material in nuclear reactors with the approach of trapping stray neutrons. Although some experiments were conducted on a smaller scale, rapidly increasing costs meant that plans to experiment with growing tritium in ether had to be shelved.

Fusion researchers believe that if there is political will and engineering challenges are solved, the first stable fusion reactors can enter the cycle by 2040. But that date is still 10 years behind the target set to keep global warming below the 1.5°C target by 2030. According to Lu:

Decision makers are more eager for the holy grail of clean energy from an endless source. Having spent huge sums of money on fusion research, they are unwilling to give up; Just like spending decades chasing fantasy Breeder reactor [رآکتوری شکافتی با توانایی تولید انرژی بیشتر از انرژی مصرفی] they did

Despite all the challenges, recent years have seen a steady stream of advances in fusion technology. The successful experiment of artificial intelligence to control the plasma inside a tokamak was among the most interesting recent achievements. Given these developments, physicists insist that multiple strategies are necessary for a long-term solution to the climate crisis, and that fusion will become a vital component of a future carbon-free energy system.

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