Containment is main difficulty with fusion power

Thermonuclear reactions deep in the sun’s interior consistently generate the same amount of energy as 2.5 billion 500-megawatt generators, the largest on Earth. In one short second the sun produces enough energy to power New York City for 100 years.

Fusion reactions are thermonuclear (thermo = temperature) because they take place at temperatures in the millions of degrees. The pressure is also unimaginably high in the star’s interior as gravity contains the hot plasma with its immense gravity due to its mass.

All stars exist in a give and take, quid pro quo state of equilibrium. Gravity prevents the star from exploding, while nuclear fusion in the core prevents gravity from crushing it.

The reactions require insanely high temperatures and pressures. 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: ­nucleosynthesis.

Hydrogen ions are just protons. In the plasma, electrons are too energetic for the nuclei to hold them, so the plasma is a sea of free protons and electrons.

The beauty of fusion is that when you weigh the pieces before and after, they do not add up. The helium nucleus weighs less by a small amount than the protons that created it. The excess mass is released in the form of energy according to Einstein’s mass-energy equivalence, E=mc².

Each fusion releases only a minuscule 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.

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 water. There is enough in the ocean to provide the entire planet for a million years. 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, to have the temperature and pressure high enough to force protons to fuse.

The last part of the fusion process is containment, which is the most difficult. It occurs naturally in the sun where gravity does the job. In the lab or on a factory floor, there is no known substance that remains solid to contain the reaction at the 30 million degrees required for fusion.

Of all containment solutions attempted to date, magnetic fields have shown the most promise.

To generate a magnetic field powerful enough to contain the multimillion-­degree plasma requires a powerful superconducting electromagnet, which requires a very high current to create and maintain the powerful fields.

Most systems use high-­intensity laser beams to put pressure on small plasma samples while in the containment of the magnetic field.

As promising as it sounds, virtually all attempts to generate more power than is used for the containment have failed.

Experiments using magnetic fields shaped like doughnuts or spheres are underway. Even so, many skeptics say we will never get a working fusion reactor because the containment technology is insurmountable.

Richard Brill is a professor of science at Honolulu Community College. His column runs on the first and third Fridays of the month. Email questions and comments to brill@hawaii.edu.