Nuclear Fusion: A Clean Energy Breakthrough

Julia Kim

For the first time in the nearly 70-year history of controlled fusion research, scientists at Lawrence Livermore National Laboratory (LLNL) have successfully effected a fusion reaction that produced more energy than what it took to ignite it. U.S. officials have reported this promising result could eventually accelerate the world’s transition to renewable energy, thereby helping to mitigate climate change. Yet, what is nuclear fusion and how might it differ from its similar-sounding counterpart, nuclear fission?

To put it simply, nuclear fusion is a nuclear process in which two lighter elements are joined together at very high temperatures and pressures to form a heavier element. According to Albert Einstein’s Mass-Energy Equivalence Principle, such a reaction always releases energy, as the mass of the product is smaller than the mass of the reacting nuclei. Of particular concern is the fusion reaction at the LLNL, in which 192 high-powered laser beams were fired at a capsule containing deuterium and tritium –– two of the three most stable isotopes of hydrogen –– thereby heating them to temperatures and pressures high enough to simulate the extraordinary conditions of a star. Upon the ejection of high-energy neutrons and alpha (or helium) particles, three mega-joules of energy were also released, which, compared to the two mega-joules required to spark the reaction, meant a substantial net gain of energy of roughly 1 to 1.5 mega-joules. 

Nuclear fussion is not to be confused with nuclear fission, in which a heavier element is split into lighter fragments, resulting also in the release of energy. In fact, all nuclear power plants use nuclear fission, often irradiating uranium-235 with neutrons, splitting them into more neutrons and other atoms with smaller atomic numbers. The emitted energy, which averages at about 82 tera-joules per kilogram of uranium-235, can be harnessed as an important source of non-renewable heat and electricity, similar to conventional fossil fuel power plants.

And why should these differences between nuclear fusion and fission matter? As discussed above, the fusion reactions of today mainly use deuterium and tritium, which are found in the chemical structure of water, H₂O. Accordingly, the reagents that generate this kind of energy are virtually limitless, carbon-free, and clean. Moreover, fusion produces no long-lived nuclear waste; the alpha (or helium) particles that are ejected form an inert gas known to have no negative polluting effects upon the environment. 

By contrast, nuclear fission power plants require uranium-235, a non-renewable, toxic, and highly polluting energy source as a main reagent. In fact, the mining of uranium has been shown in studies to imperil various endangered species, to pose cancerous effects on human health, and to contaminate air and nearby aquatic ecosystems for hundreds of years. Further, nuclear fission power plants generate unstable radioactive nuclei, some of which have half-lives of millions of years!

Knowing the promising advantages of nuclear fusion over fission as well as over other conventional energy sources, how long might it be until fusion becomes a viable energy source for the public? Though humanity is on a race against the clock to fight climate change, scientists are predicting that it may take years or perhaps decades before fusion may be used as an economically viable contributor to the electric grid. 

Launched in 1985, an extensive international collaboration, ITER, is designing and building a fusion reactor in the south of France, which will test, improve, and advance the feasibility of fusion as a large-scale, affordable, carbon-free, and dependable source of clean energy. Though highly promising, developmental, scientific, and regulatory issues mean that years, if not decades, are required before commercial entities develop their own fusion reactors and make this form of energy a viable power plant for the public. 

But with this new breakthrough from the LLNL, the world has at least witnessed, for the first time in history, that the dream of fusion is indeed possible for humanity.