Thermonuclear reactions deep in the sun’s interior generate the same amount of energy as 2.5 billion 500-megawatt generators, the largest on Earth. In one second the sun produces enough energy to power New York for 100 years.
Fusion reactions are thermonuclear because they take place at temperatures in the millions of degrees. The pressure is unimaginably high in the star’s core as the gravity from the star’s immense mass contains the hot plasma.
All stars exist in a quid pro quo state of equilibrium. Gravity prevents the star from exploding, while fusion in the core prevents gravity from crushing it.
In order for fusion to occur, two hydrogen ions must collide with just the right dynamics for the strong nuclear force to overcome the repulsive electric force.
This initiates what is arguably the most important process in the universe when fusion begins the creation of heavier elements: nucleosynthesis.
Hydrogen ions are just protons with electrons stripped off. In the plasma state, electrons are too energetic for the nuclei to hold them, so the plasma is actually a sea of free protons and electrons.
The beauty of fusion is that when you weigh the atomic nuclei before and after, they do not add up. The helium nucleus weighs less than the protons that created it by less than 1 percent. The excess mass is released in the form of energy according to Einstein’s mass-energy equivalence, E=mc2.
Each fusion releases only a miniscule amount of energy, too small to be perceptible. Yet because of its tremendous size, the sun produces 35,000 times more energy than all electricity use on Earth as about 4 million tons of the sun vanishes every second.
Scientists and technologists would like to re-create the conditions in a fusion reactor to generate electricity.
Fusion power sounds too good to be true. It uses deuterium, or heavy hydrogen, which is plentiful in Earth’s oceans. It is clean. There is no nuclear waste, only helium.
The keys to commercially producing large amounts of fusion energy are to have a large number of protons in the plasma, to have the best configuration of protons to maximize the fusion and to have the temperature and pressure high enough to force protons to fuse.
Containment of the fusion process at the 30 million to
100 million degrees required is the challenge. It is not a problem in the sun where gravity does the job. On Earth, however, there is no substance that can withstand those temperatures. Of all containment solutions attempted to date, magnetic fields have shown the most promise. Several types of toroidal (doughnut-shaped) confinement systems seem to have potential.
Although uncomplicated in description, engineers have yet to build a working, scalable fusion reactor after 70 years of being “only 50 years away.” Virtually all attempts to generate more power than is used for the equipment have failed.
Many skeptics say we will never get a working fusion reactor because the containment problem is insurmountable.
Others look ahead to the possibility of solving Earth’s energy problem, with no carbon or radioactive waste production.
Richard Brill is a professor of science at Honolulu Community College. His column runs on the first and third Friday of the month. Email questions and comments to brill@hawaii.edu.
