Clean fusion?

While fusion may have great potential, it will be a long time before we are able to fully harness it.

In mid-December, scientists for the first time reported a successful nuclear fusion experiment that produced more energy than made it happen. A friend who is a physics professor at the University of Waterloo was bubbling with excitement when he shared its implications with me. Ever since I was in high school, about 60 years ago, I have heard about the promise of fusion energy as a clean and potentially abundant source of energy that could end our dependence on fossil fuels.

Fusion, in theory, is a simple idea. Two light hydrogen atoms are fused into a larger helium atom, releasing energy. Unlike nuclear fission (the process used in our current nuclear power plants) where a large atom is split into two, with fusion no radioactive by-products are produced, making it a much cleaner energy source. The difficulty, however, is in the details.

The long road ahead

Getting two hydrogen atoms to fuse takes a lot of heat and pressure, which is the initial energy input needed. Until now, all fusion experiments required more energy going in than was generated by the resulting fusion. This recent experiment is exciting to scientists and engineers because it proves that, in principle, fusion has energy-producing potential. But while the energy going in (2.05 megajoules) was less than the energy produced (3.15 MJ), these numbers were dwarfed by the energy required to set up and run the experiment (322 MJ). This is only a tiny step toward fusion technology becoming a day-to-day reality. Engineers need to do much more work to make fusion a viable energy source.

Fusion also faces a fuel problem. 99.98% of hydrogen has one proton and no neutrons in its nucleus and is unsuitable for fusion. Two rare hydrogen isotopes are needed.  Deuterium, which has a single proton and one neutron, is reasonably common and can be found in heavy water. It is used in Canadian CANDU fission reactors, which converts a minuscule amount of the deuterium into tritium. This process is one of the few sources of tritium, an isotope with a single proton and two neutrons. Tritium is necessary for fusion. Currently, one gram of tritium costs about $400,000 and there is only a small supply, made mainly in our CANDU reactors. This fuel-availability problem may limit fusion power.

These realities have led everyone to recognize that while fusion may have great potential, it will be a long time before we are able to fully harness it. In the meantime, the reality of climate change, due to the increasing amounts of carbon dioxide in our atmosphere, can be seen in our more extreme weather events. Fusion may someday become a common clean energy source, but that will not happen quickly enough to prevent further increases in carbon dioxide if we do not change our current energy use. As Christians who realize that we are only stewards of God’s earth, we need to be at the forefront of efforts to reduce our carbon use. Fusion may happen, but it is not a solution to our current climate problems.


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