Artificial (terrestrial) fusion schemes, on the other hand, are restricted to much lower particle densities and much more fleeting energy confinement, and are therefore compelled to use the heavier neutron-rich isotopes of hydrogen known as deuterium and tritium-which are 24 orders of magnitude more reactive than ordinary hydrogen. Scaling down the sun. As noted above, fusion reactions in the sun burn ordinary hydrogen at enormous density and temperature, sustained by an effectively infinite confinement time, and the reaction products are benign helium isotopes. I concluded that a fusion reactor would be far from perfect, and in some ways close to the opposite.

Collaborative, multinational physics projects in this area include the International Thermonuclear Experimental Reactor (ITER) joint fusion experiment in France, which broke ground for its first support structures in 2010-with the first experiments on its fusion machine, or tokamak, expected to begin in 2025.Īs we move closer to our goal, however, it is time to ask: Is fusion really a “perfect” energy source? After having worked on nuclear fusion experiments for 25 years at the Princeton Plasma Physics Lab, I began to look at the fusion enterprise more dispassionately in my retirement.

In experiments to date, the energy input required to produce the temperatures and pressures that enable significant fusion reactions in hydrogen isotopes has far exceeded the fusion energy generated.īut through the use of promising fusion technologies such as magnetic confinement and laser-based inertial confinement, humanity is moving much closer to getting around that problem and achieving that breakthrough moment when the amount of energy coming out of a fusion reactor will sustainably exceed the amount going in, producing net energy. But to replicate that process of fusion here on Earth-where we don’t have the intense pressure created by the gravity of the sun’s core-we would need a temperature of at least 100 million degrees Celsius, or about six times hotter than the sun.

Our sun constantly does fusion reactions all the time, burning ordinary hydrogen at enormous densities and temperatures. These pro-fusion advocates also say that fusion reactors would be incapable of generating the dangerous runaway chain reactions that lead to a meltdown-all drawbacks to the current fission schemes in nuclear power plants.Īnd, like fission, a fusion-powered nuclear reactor would have the enormous benefit of producing energy without emitting any carbon to warm up our planet’s atmosphere.īut there is a hitch: While it is, relatively speaking, rather straightforward to split an atom to produce energy (which is what happens in fission), it is a “grand scientific challenge” to fuse two hydrogen nuclei together to create helium isotopes (as occurs in fusion). Proponents claim that when useful commercial fusion reactors are developed, they would produce vast amounts of energy with little radioactive waste, forming little or no plutonium byproducts that could be used for nuclear weapons. Fusion reactors have long been touted as the “perfect” energy source.

Fission fusion