Fusion Power

Fusion Power

Generating electricity from fusion rather than fission of atoms has been a dream ever since the first hydrogen bomb was exploded.

What was originally seen as an easily solvable scientific problem, i.e., how to control the plasma, has turned out to be far more difficult than originally envisioned.

Basic science of fusion

Fusion, as envisioned for the generation of electricity, was to utilize the energy released when two atoms of hydrogen were combined to form one atom of helium.

Hydrogen, for the most part, is not found free of entanglements on Earth. It’s almost always found in combination with another element, such as carbon.  For example, methane, CH4, consists of one carbon atom and four hydrogen atoms.

Hydrogen also has isotopes, with Deuterium being an isotope potentially used for fusion power. Deuterium has a proton and a neutron, while the most common hydrogen only has a proton. All hydrogen atoms have an electron so the atom is electrically neutral.

An isotope is an atom that has a different number of neutrons than protons. Oxygen normally has 8 protons and 8 neutrons, while the isotope Oxygen-18 has 8 protons and 10 neutrons.

When two Deuterium atoms are combined through fusion, they will form Helium. However, some loss of mass will occur, which is what produces the energy from the fusion of the two elements. (The mass of two Deuterium atoms is greater than the mass of a Helium atom.)

It’s also possible to use Tritium, a second Hydrogen isotope having two neutrons, thereby increasing the amount of mass lost during the fusion process.

Diagram from ITER web site

It’s necessary that temperatures be extremely high for fusion to take place, temperatures akin to those found in the sun’s interior where there are also strong magnetic forces.

With extremely high temperatures, the energy between the parts of an atom increases and the atom breaks apart, forming the fourth state of matter, plasma.

Out of that plasma soup, that acts like a gas, the particles of two Deuterium or Tritium atoms form a helium atom with a resulting loss of mass and ejection of energy.

The plasma also has magnetic properties, which would, theoretically, allow a strong magnet to hold the plasma in place.

Problem with using fusion for generating electricity

For fusion to occur, we need the plasma, as described above, contained at extremely high temperatures by magnets so that the plasma floats within the magnetic field, never touching any part of the device forming the magnetic field.

While it was originally thought it would be a simple matter to produce a magnet for constraining the plasma, it has turned out to be extremely difficult.

The international effort to develop such a device is being done collectively by thirty-five nations, including the United States, in France at the ITER (International Thermonuclear Experimental Reactor) facility.

“‘Toroidal magnetic confinement fusion’ is the advanced technology that is the main approach for fusion research and is at the heart of the ITER experiment.”

ITER is using a tokamak, a doughnut-shaped magnet with a vacuum chamber where the plasma is to be contained. Heat from the release of energy is to be transmitted through the walls of the tokamak where it can be captured and used to produce steam for use in a steam turbine generator.

“‘Tokamak comes from a Russian acronym that stands for ‘toroidal chamber with magnetic coils.’”

ITER Tokamak from ITER Web Site

The entire Tokamak unit, consisting of electromagnets, vacuum vessel, blanket modules, solenoid (transformer) and correction coils, is contained in a cryogenic vessel, depicted above, which is essentially a thermal insulating blanket, 91 feet tall, 89 feet in diameter, and weighing 23,000 tons with an estimated total cost of $50 billion.

The ITER plan calls for the first plasma to be produced in 2035.

For fusion to actually generate electricity, the ITER tokomak must work as designed, and there must be significantly more energy produced than consumed by the magnetic coils.

Others, such as Lockheed Martin and the University of Washington, are also working on the fusion process for generating electricity. A British company, Tokamak Energy, has said it will be able to generate electricity by 2030. 

Lockheed Martin received a patent for its containment process, which differs from the ITER tokomat, on February 18, 2018. Lockheed claims it will generate electricity from its compact fusion reactor (CFR) sooner than any competitor. Lockheed also claims its CFR will generate 100 MW of power, but says nothing about cost. 

If fusion is successful, it could revolutionize energy production for the benefit of all mankind.

However, fusion power must be able to produce electricity at below 10 cents per kWh if it is to be economically successful.

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4 Replies to “Fusion Power”

  1. One problem with the D+T fusion is that it produces an undesirable 14.7 million electron volt neutron, that can create all sorts of problems in a reactor.
    As you mention, all fusion reactions require very large energies to initiate. At such temperatures, the hot plasma can become difficult to control. Not clear if laser fusion can yield the needed large power required.
    There is a considerable range among various fusion reactions in the energy required to initiate. The D+T is the lowest energy, because the distance for quantum probability for particle location exceeds the physical quantum repulsion of the proton. In fact, the Cockcroft-Walton accelerator requires only 200,000 volt acceleration to produce fusion, and earned the inventors a Noble Prize in the late 1930s. The 14.7 MeV neutron enable artificial production and thus study of many, many radioactive nuclides not previously known. This became a main study theme in nuclear chemistry. (I used a C-W some as a graduate student.)
    Several other fusion reactions are possible in principle, but whereas some do not produce undesirable and energetic particle emissions, they all require greater temperatures to initiate fusion.

    As for promises some give as to how close fusion power now is – how long have we been hearing that?

    • Thanks. As always, good additional information.
      I tend to thing ITER is a boondoggle, spending $50 billion.
      Fusion has always been just around the corner for fifty years, and might still be.
      As for Lockheed Martin, they have stuck their necks out by being so bullish … But maybe they have something, we’ll know in a couple of years.

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