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What is Fusion Power?

Fusion is a nuclear process. We do, of course, have nuclear power today, based on the fissioning of uranium, that is, the splitting of uranium into parts. Fusion is the process that generates light and heat in the Sun, and in the other stars, and, as such, it is the dominant energy source in the universe. It is a nuclear process, but it is the combining of atoms, rather than the splitting of atoms, which is fusion.

It’s most easily achieved on Earth by combining the heavy isotopes of hydrogen, deuterium, and tritium. Hydrogen is the lightest of all the elements. Deuterium is heavy hydrogen. Tritium is three times heavy hydrogen. These isotopes of hydrogen, when combined, form helium, which is the next heaviest element in the Periodic Table.

Deuterium, the heavy isotope of hydrogen, is found one part in 6,000 in ordinary water, and hence it’s universally available, and eliminates the problem of the unequal geographical distribution of fuel resources. There will be fuel for fusion as long as there’s water on the planet, which means that there will be fusion fuel available to all nations, as long as there’s life on the planet.

Whatisfusion_2

Two atoms, deuterium and tritium, fuse together, forming a helium nucleus, a neutron and lots of energy

Let’s look at the fusion reaction itself . You see deuterium and tritium, the two heavy isotopes of hydrogen, schematically fused, and when they do, they disassemble themselves into the helium product, and a fast neutron. Mass is converted from the mass of two heavy isotopes of hydrogen, into the products, and in the process, mass disappears and comes out as kinetic energy of the products, according to Einstein’s formula: E=mc2

As we said earlier, fusion is a nuclear process, and as such, it gives out much more energy per pound than the burning of fossil fuels. Fusion fuel, for example, releases about 10 million times more energy per pound than the burning of fossil fuels, and about ten times more per pound than the fissioning of uranium.

Multiple Uses

The primary goal of the fusion program worldwide has been, and is, the production of electricity in a central station power plant. However, that is not the only possible use for fusion. In competition with other energy sources, fusion may also be useful for the production of hydrogen, for the desalination of water, for the production of fuel for fission reactors, and for the deactivation of fission reactor waste.

A conventional heat-exchange system removes heat from the moderator blanket. Heat is converted by a conventional power conversion system. Source: Fusion Power Associates

A conventional heat-exchange system removes heat from the
moderator blanket. Heat is converted by a conventional power conversion
system. Source: Fusion Power Associates

Why fusion?
Fusion fuel comes from water, and hence is abundant, widely available, and easily extracted from the water at low cost. The fusion reaction itself is environmentally friendly. It produces no CO2 emissions, no radioactive waste from the fusion reaction itself, although the fast neutron does activate the structure of the fusion reaction; but those products have relatively low hazard potential, and relatively short half-life, and therefore do not require deep geological storage for many, many thousands of years.

Who cares?
Scientists have sought to make fusion work on earth for over 40 years. If we are successful, we will have an energy source that is inexhaustible. One out of every 6500 atoms of hydrogen in ordinary water is deuterium, giving a gallon of water the energy content of 300 gallons of gasoline. In addition, fusion would be environmentally friendly, producing no combustion products or greenhouse gases. While fusion is a nuclear process, the products of the fusion reaction (helium and a neutron) are not radioactive, and with proper design a fusion power plant would be completely passively safe, and would produce no high level radioactive waste. Design studies show that electricity from fusion should be about the same cost as present day sources.

We’re getting close!
While fusion sounds simple, the details are difficult and exacting. Heating, compressing and confining hydrogen plasmas at 100 million degrees is a significant challenge. A lot of science and engineering had to be learned to get fusion to where we are today.

Going back to the 1960’s, the product of the density, the confinement time, and the temperature, was quite low. Over the years, in experiments around the world, that product has gradually gotten higher and higher and higher.

Fusion Reactor History

General Atomics

1960s – DIII & DIII–D: Tokamak Experiment

Massachusetts Institute of Technology

1991- Alcator C

PPPL: Princeton Plasma Physics Laboratory

1976 – PDX: Poloidal Divertor Experiment
1982-1997 TFTR: Tokamak Fusion Test Reactor

TFTR was the first in the world to use 50/50 mixtures of deuterium-tritium, yielding an unprecedented 10.7 million watts of fusion power.

Japan

1985-2010 – JT–60U: Japanese Tokamak Experiment

In 2010 JT-60 was disassembled and is currently under construction to be upgraded to JT-60SA by using niobium-titanium superconducting coils.

Europe

1983 – JET: Joint European Torus

The largest tokamak in the world, it is the only operational fusion experiment capable of producing fusion energy.

Today we are very close to the regime we need to be in, called the burning plasma regime, and there are two facilities that will produce net amounts of fusion energy for the first time, hopefully in the next one or two decades. One is called the National Ignition Facility (NIF), the laser-based inertial confinement facility, which currently in operation in California. The other is called ITER, the International Thermonuclear Experimental Reactor, which is also being built in Cadarache, in France.

The NIF and ITER Projects

2010 – NIF:  National Ignition Facility
Under Construction – ITER: International Thermonuclear Experiment Reactor

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