Nuclear fusion is the most promising energy alternative of our era. It works by mimicking the mechanisms in the stars’ core at insanely high temperatures and pressures. The biggest challenge in building modern fusion reactors lies in the difficulty and current technological limitations to efficiently and safely reproduce in the laboratory, an environment as extreme as the burning core of a star.
The science and other stuff to know
Inside experimental nuclear reactors such as Tokamak or ITER, the deuterium and tritium plasma that acts as fuel is at 150 million degrees Celcius. A challenging technical problem is keeping plasma away from reactor walls — so if it contacts with the plasma, it would melt — and with the instabilities of the plasma, which bubbles like boiling sauce.
The reactor is designed to create a magnetic field within which the hot plasma is confined so that it does not touch the walls but remains levitating. Although there’s much to do before finding the most optimal combination of materials and engineering models for a stable and efficient reactor, scientists at MIT and other collaborators are making considerable progress in this direction.
Challenges related to controlling plasma instabilities remain to be resolved since one of its “bubbles” could pass through the magnetic field and reach the reactor walls. However, a collaboration between the Max Planck Institute and the Vienna University of Technology has found a potentially successful answer to this problem. In a study recently published in Physical Review Letters, Dr. Elisabeth Wolfrum’s team has devised an efficient way to control plasma instabilities. It uses magnetic coils that slightly deform the plasma, making it denser in the regions adjacent to the reactor, that is, on its walls. This way, experts can monitor and control many harmless small instabilities instead of dealing with one or two large, dangerous bubbles. It’s like lowering the heat to the pot of sauce and seeing how the bubbles become more frequent but less powerful, avoiding filling the kitchen with tomato.
“It’s a bit like a pot with a lid, where the water starts to boil. If the pressure increases, the lid will lift and vibrate strongly due to escaping steam. But if you tilt the lid slightly, steam can continually escape, and the lid remains stable and does not vibrate,” explains Georg Harrer, lead author of the paper to Phys.org.
Developing new techniques that ensure the efficient operation of nuclear fusion reactors is critical to commercializing fusion energy. As a result, industries and governments worldwide can use fusion reactors as the primary energy source so that we stop emitting greenhouse gases that are leading to global warming. Otherwise — or if we fail to optimize the use of other renewable sources — we will soon have no escape.
Nuclear fusion has the potential to be the main form of energy for our civilization by the middle of this century.
ITER, IFMIF, and DEMO — currently the experiments/prototypes working with fusion technology — promise to become fully operational in the coming decades and face commercial foray by 2060. ITER plans to make fusion from deuterium and tritium plasma viable from 2035, and by 2040 DEMO should have shown that commercial nuclear fusion is feasible and profitable.