By Irina Slav
For years nuclear fusion was the stuff of sci-fi books and movies, but technology has brought it, like so many other things, closer to reality. So close, in fact, that there are plans to build the first nuclear fusion reactor by 2025 – a reactor that could yield a lot more energy than is fed into it and provide vast amounts of clean, sustainable energy.
Nuclear fusion, unlike fission, involves smashing particles together to generate energy. Basically, as Bloomberg Energy author Jing Cao explained in a detailed June overview, it’s like recreating the Sun on Earth.
An international team of scientists is working on the biggest project in nuclear fusion in France, to build the largest magnetic fusion machine – a tokamak – and test the commercial-scale viability of this clean energy source. The ITER project is based on the pretty simple premise that the larger the vessel in which fusion reactions occur, the more of them occur, generating more energy.
The ITER tokamak will be ten times larger than the largest existing such device, capable, as per plans, to produce 500 MW of fusion power. To compare, the record so far, set by European tokamak JET (the largest existing one), is 16 MW, from input of 24 MW. The goal of the ITER team is to produce these 500 MW from an input of just 50 MW. Recently, a team of researchers from the MIT published a paper that suggests this achievement is realistic.
The MIT team tweaked the “recipe” for nuclear fusion in such a way that the output of power was ten times greater than with the original composition, which consists of 95 percent deuterium ions and 5 percent hydrogen ions, forming plasma heated to incredibly high temperatures in the tokamak from the movement of the ions.
The tokamak produces magnetic fields that keep the superhot plasma inside and keep it moving – and hot – but controlling it for ever-longer periods of time and making it move faster to produce more energy has been a challenge. Now, the MIT scientists may have found the secret ingredient in an isotope of helium, helium-3.
The team, from the Plasma Science and Fusion Center of the MIT, added trace amounts – 1 percent – of helium-3 to the traditional combination and tested the new combination at the Alcator C-Mod tokamak. The results showed that the hydrogen-deuterium-helium plasma got wrigglier and hotter, producing 10 times more energy than before. The amount of energy produced after the addition of helium, the researchers explained, increased output by an order of magnitude, bringing it into the realm of megaelectronvolts.
One of the scientists involved in the project, John C. Wright, explains,
“These higher energy ranges are in the same range as activated fusion products. To be able to create such energetic ions in a non-activated device — not doing a huge amount of fusion — is beneficial, because we can study how ions with energies comparable to fusion reaction products behave, how well they would be confined.”
The test results were so exciting that another team, the one working with the JET in the UK, decided to replicate them. The replication confirmed the results, raising hopes that a fully functional nuclear fusion reactor may indeed be on the horizon. This horizon is still far, or near, depending on your perspective. According to the head of the Alcator C-Mod project, Earl Marmar, we could see fusion reactors in the 2030s. The main problem: keeping the process going.