Isotopes are really important for making nuclear energy. They help with two main processes: nuclear fission and fusion. Let's break these down.

1. Fissionable Isotopes:

   • The biggest players here are Uranium-235 (U-235) and Plutonium-239 (Pu-239). These isotopes are mainly used in nuclear power plants.
   • U-235 is found in nature at about 0.72%. However, it can be enriched, which means made stronger, to over 3% for use in reactors.

2. Nuclear Reaction:

   • In nuclear fission, when a neutron hits U-235, it can make the atom split apart. This splitting releases a lot of energy—about 200 million electron volts (MeV) each time it happens!

3. Fusion Isotopes:

   • For fusion, we use Deuterium (D) and Tritium (T). These are special forms of hydrogen. When they combine, they produce a large amount of energy.
   • In fact, fusion energy gives off about 17.6 MeV for each reaction, showing how powerful it could be for our future energy needs.

So, to sum it up, isotopes are key for the growth of nuclear energy technologies.