By Kaiya Palmer
There are many options currently available for renewable energy: wind, solar, hydroelectric, nuclear fission and more. Nuclear fusion releases a huge amount of energy and very little radioactive waste, making it an appealing option, but the problem is that it requires conditions of extreme temperature and pressure, and until now we have not been able to produce more energy in a fusion experiment than the energy used to create these conditions. But a fusion experiment on the 5th December 2022 at the National Ignition Facility in California released 50% more energy than was used to heat the fuel. So the use of nuclear energy may not be as far off in the future as was previously thought.
What is nuclear fusion?
Nuclear fusion is, in simple terms, the fusion of two smaller nuclei into one larger nucleus. Nuclei are located at the centre of every atom, where they contain the protons and neutrons, and are surrounded by shells of electrons.
Nuclei repel each other because they are positively charged, and like charges repel, so they can only get close enough to fuse in conditions of very high temperature and pressure, like the centre of stars.
When the two nuclei fuse, the mass of the larger nucleus is slightly smaller than the combined masses of the two smaller nuclei. This is because some of the mass becomes energy (E=mc2). So the products of the reaction will be the larger nucleus, neutrons and energy. Unlike nuclear fission, nuclear fusion does not produce long-lasting radioactive waste that has to be buried, making it a much safer process.
Nuclear fission, the process of splitting a larger atom into two smaller atoms, releasing energy, has been used commercially for a long time, but it has also resulted in disasters like Chernobyl, due to the dangerous radioactive material that is used. If a nuclear fission experiment gets out of hand and the reactor is faulty, it might result in a catastrophic event. These risks led countries like Germany, which obtained a quarter of its energy from 17 nuclear fission reactors until March 2011, to shut down the vast majority of those reactors, with only three being active now and plans to shut all of them down. Nuclear fusion reactions, on the other hand, could not possibly get out of control because it requires so much energy to even maintain the conditions required.
The experiment at the NIF
The experiment on the 5th December 2022 was a massive breakthrough as ignition – a nuclear reaction that creates more energy than it consumes – was achieved. 2.05 megajoules – about the same amount of energy in five bananas – was concentrated onto a gold can containing a frozen pellet of deuterium and tritium (heavier isotopes of hydrogen) by 192 lasers, creating extraordinarily high temperatures comparable to those of stars. This process is called indirect drive, where the lasers are focused onto a gold cylinder which generates x-rays that reach the fuel, resulting in fusion.
3.15 megajoules of energy were released, meaning around 50% more energy was produced than consumed in the reaction.
These results are not only significant in the future of renewable energy, but also to other areas such as research about what happens in an explosion created by a nuclear weapon.
However, although ignition is a major milestone towards using nuclear fusion as a mainstream energy source, much more work has to be done: 322 megajoules of energy were consumed by the lasers heating the fuel, far more than the 3.15 megajoules released in the reaction. Scientists will need to work to make the lasers more efficient, and perhaps consider a direct drive approach, where lasers fire directly onto the fuel rather than a gold cylinder, as is used by the Laboratory for Laser Energetics at the University of Rochester.
This experiment proved that nuclear fusion is a possible renewable energy source and has produced useful data that scientists can now use to achieve the goal faster.
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