Very Basic Physics of Fusion Energy

1- Deuterium - deuterium fusion reaction of the sun

Fusion occurs in plasma, the fourth state of matter. Consider the familiar 3 states: solids, liquids, and gases. Now imagine hydrogen gas heated to 10s of millions of degrees C, the temperature of the surface of the sun. The size of the sun is responsible for the tremendous force of gravity on hydrogen. The combination of temperature and gravity causes hydrogen to ionize into proton/neutron nuclei and free electrons. The plasma proton-proton nuclei circulate and fuse at great speed, overcoming the Coulomb law effect. This proton-proton fusion reaction releases energy that we see and feel from the sun. The mass of the nuclei is less after the collision and the energy released is proportional to the loss of mass as per Einstein's E=mc(squared). Fusion also occurs in lightning, the Aurora Borealis, and between 2 touching grapes that are cooking in a microwave oven (eventually destroys the microwave).

In the sun deuterium nuclei fuse to produce energy, a neutron and Helium. This occurs countless number of times.

2- Deuterium/Tritium Reaction – used by most fusion energy projects on earth

The deuterium-deuterium fusion reaction of the sun will not work on earth as we can not generate enough input energy from temperature and gravity to start the reaction we see in the sun. We, however can manufacture fusion from different isotopes/ions of hydrogen. Please see previous blog re:General Fusion - One of the most promising Fusion projects .

Deuterium is produced from water, Tritium comes from heavy water in Canadian Candu Fission Reactors (5.2 pound per year, one of the few sources on earth). One deuterium ion collision with one tritium ion generates 17.6 *106 eV or 2.8 *10-12 joules of energy. That is impressively small, but the number of collisions in a few microseconds of a plasma firing is mind-bending. There will be no meltdown from fusion as the reaction lasts as long as there is enough temperature, enough pressure and enough time for a reaction. Fusion smashes small light positively charged particles like hydrogen ions/nuclei together to release heavier atoms like helium. The core of the sun is iron, the end result of the fusion reactions.

3- The Helium-3 reaction with deuterium has been used to eliminate the neutrons produced from the previous 2 methods and makes energy capture more efficient. This is bleeding edge and so has not much more to report.

4- The protium - Boron-11 reaction similarly is aneutronic and places much stiffer specifications on making it work.

Fission is the antithesis of fusion. Fission breaks up heavy metal atoms like uranium to release energy and the radioactive isotopes eventually become lead.

The atom of Uranium is one of the heaviest. A neutron starts the split of a uranium atom and then a chain reaction begins.