Can someone explain nuclear fission and fusion to me?

Question

Why are only particular fuels like uranium and plutonium used for energy generation by fission? Also, how is energy released through fusion and does it(the type of energy) have a particular name?

Answer 1

The key to understanding fission and fusion is to understand what is known as the "binding energy per nucleon" or "mass defect." The force (attractive force) that keeps the nuceii of atoms together, called the strong nuclear force, acts differently depending on the configuration of the nucleus. If we divide the total binding energy of this nuclear force for a particular nucleus by the number of nucleons (i.e., protons + neutrons added together), we get a measure of how "stable" the nucleus is. The more binding energy per nucleon, the more stable the nucleus is - that is, the more tightly bound the particles are.

Similarly, the mass defect represents the difference between the relativistic mass of the nucleus and the rest masses of the particles - another way of looking at the binding energy in relativistic (E=mc^2) terms.

Certain nuclei are more stable than others. Ordinary hydrogen, for example, consists only of a single proton - so there is no binding energy per nucleon. Very large nuclei - such as uranium and plutonium - are very unstable because as the nucleus becomes larger, the relative effect of the nuclear force (the "binding energy per nucleon") becomes less and the electromagnetic repulsion of the protons becomes greater.

Our universe tends toward greater stability. When large relatively unstable nuclei such as Uranium or Plutonium are bombarded by free neutrons, there is a probability that some of the nuclei will split into two more stable nuclei (i.e., nuclei with greater binding energy per nucleon). This is fission. The difference in binding energy is converted to kinetic energy (heat) and radiation (gamma rays, light).

Similarly, some very small nuclei such as hydrogen have less binding energy per nucleon than larger nuclei such as helium. When these smaller nuclei are forced together within the range of the strong nuclear force, there is a probability the nuclei will combine (fuse) into a more stable nucleus with greater binding energy per nucleon. This is fusion. Again, the difference in binding energy is converted to kinetic energy (heat) and radiation (gamma rays and light).

Fission and fusion are only sustainable if the resultant nuclei are more stable than the initial nucleii - i.e., if the binding energy per nucleon increases. Also, fission and fusion require some energy input to get them started - Uranium and Plutonium have lower initial energy requirements, so it is easier for them. Similarly, hydrogen fusion into helium is "relatively" easy compared to fusion of other nuclei.

Answer 2

First of all fission is the splitting of atoms which releases energy. The reason that we use uranium or plutonium is because when these molecules are split they release neutrons which bombard the next uranium of plutonium atom causing it to split. It causes a chain reaction until there are trillions of atoms spliting. Those trillions of atoms splitting let go huge amounts of energy.

Fusion is the combining of hydrogen atoms to form helium atoms. It also gives off tons of energy but i dont think that it has a special name

Answer 3

fusion=just joining 2 particles
fission=splitting of 2 particles

because these elements release a very huge amount of energy

Answer 4

fission > energy goes away from core
fusion > energy goes towards core

Answer 5

In simple terms fusion is when we get bigger atoms from smaller atoms while fission we get smaller atoms from larger. An in either we get a lot of energy.

For example the Sun produces helium (He) from fusing hydrogen (H) atoms. Good reference http://en.wikipedia.org/wiki/Nuclear_fusion

For nuclear fusion please see http://en.wikipedia.org/wiki/Nuclear_fission