Fusion vs. Fission

 

Fusion

To understand the technology behind plasma fusion, fusion itself must be understood. Fusion is the combining of two or more atoms of low mass, which are initially attracted to each other, to form one atom of greater mass. When two atoms combine to form a single atom, they have fused. This fusing releases a large amount of energy with respect to the amount of mass and energy that was initially put into the reaction. This combination releases energy in the form of light and heat.

 

 
Provided by: Physics with Modern Physics for Scientists and Engineers (Fig. 1)
Energy is created in a fusion reaction through the loss of atomic mass from the beginning to the end of the reaction. The mass of the two atoms is significantly more than the mass of the new atom, which they fused together to form. This loss of mass is subsequently converted into pure energy in the form of light and heat. The reason for this amazing discovery is that mass is just a concentrated form of energy. This understanding between the relationship of mass and energy was discovered by Albert Einstein and illustrated in his famous equation E=mc^2, where E is energy, m is mass, and c is the speed of light. Through this equation the amount of energy held within a mass can be determined. In a plasma fusion reaction between two hydrogen atoms the decrease in mass is about 4x10^-29 kg. This mass is then converted to energy, equaling 23.9 MeV. "To appreciate the magnitude of this result note that if 1g of [hydrogen] is converted to helium, the energy released… would be worth about $70,000" (Physics for scientist and Engineers 1276).

Fission

In a fission event an example of a reaction at an atomic level is an (A)tomic-bomb. The A-bomb harnesses the power of an atom through an uncontrolled reaction. This reaction is fission, which is the opposite of fusion. In an A-bomb, atoms are being separated, not combined, which also creates a massive release of energy but causes a large amount of nuclear waste when harnessed as a source of power. Nuclear waste is created when any type of matter comes in contact with an atom that has gone through a fission reaction. The water that cools the system and the room that occupies the reaction all become radioactive nuclear waste. The collision from the neutron in the fission reaction causes the atom to become unstable, resulting in a radioactive substance. From this instability the atoms become radioactive and create instabilities within any other atom that they come in contact with. Not only does fusion lack this step in its process, but through fusion studies, scientists have been able to learn new and efficient ways to clean up the process of fission.
provided by: Physics with Modern Physics for Scientists and Engineers (Fig. 2)

Fusion Waste

In both types of fusion reactions, inertial and magnetic, the wastes that are produced are basically the same. Before the fusion process is started, deuterium (3^H) needs to be extracted from water molecules, resulting in hydrogen and oxygen by-products. Both elements are absorbed into the air with no negative effect. After deuterium is created the fusion process can begin. When the deuterium and tritium atoms fuse together they create a surge of energy. As a result of their fusing a helium atom is created and a neutron is released (as illustrated in Fig. 1). Helium is a completely harmless gas that can be released into the atmosphere, but the neutron is currently a serious problem for plasma scientist.
After the neutron is released, due to the fusion of the 2^H and 3^H atoms, it travels at a high velocity until it hits something. The neutron will sometimes hit the lithium in the chamber, which creates more deuterium, but most often it collides into the walls of the reactor. Since the neutron is a neutrally charged particle it can travel through the magnetic fields that surround the plasma. This is a serious problem for the chamber. From the collisions of the neutrons the walls of the reactor break down and become very brittle. One of the ways scientist are going about combating this problem is by developing a new type of metal that can withstand a neutron collision. This development is an example of the many spin-off technologies that have been created to keep fusion technology moving into the future.