- In practice only a fraction of the energy locked in matter can
be tapped by nuclear reactions.
- Only by combining equal amounts of matter and antimatter can
complete conversion occur.
- Nuclear fission releases a tiny fraction of the available
energy by breaking heavy nuclei like Uranium apart.
- This process is the basis of nuclear reactors and power
- Nuclear fusion releases a tiny fraction of the
available energy by building up heavier nuclei from lighter
ones (e.g. Hydrogen combines to build Helium)
- This process is the basis of thermonuclear explosions
- At the moment, science has not found a way to control
fusion reactions for power generation. Fusion is
difficult to control because the reactions happen at
temperatures of millions of degrees.
- When fusing 4 Hydrogens to make Helium 0.7% of the mass
is converted into energy.
- A Helium nucleus consists of 2 protons and 2 neutrons.
- To make Helium from Hydrogen four hydrogen nuclei (protons) must
be combined to to yield Helium + energy. Two of the protons
will be converted to neutrons in the process.
- The first step is to fuse two Hydrogen nuclei -- (protons)
- Protons, however, are positively charged and repel one another (like
- The repulsion gets stronger with decreasing separation
- Two protons thrown gently at each other will bounce off.
- If they get close enough, however, they will they will stick
- They must be thrown together at extremely high speeds.
- High temperatures imply high speeds for gas particles.
- The temperature at the center of the Sun is 10 million degrees.
- This temperature is just right to impart sufficient
velocity to the protons so that fusion can occur.
- The final product, helium, is produced by a chain of reactions
that gradually builds Helium from 4 Hydrogen nuclei.
- In the Sun this reaction is called the Proton-Proton Chain.
Updated April 20, 2005