Nuclear Fusion and Energy
Nuclear fusion works completely differently - instead of splitting atoms apart, it smashes tiny, light nuclei together to form heavier ones. This is exactly what happens inside stars! Two hydrogen nuclei combine under extreme temperatures and pressure to create a helium nucleus.
Fusion actually releases more energy than fission and uses hydrogen isotopes that are relatively easy to find. The amazing thing is that some of the mass of the original nuclei gets converted directly into energy - this follows Einstein's famous E=mc² equation.
The tricky bit with fusion is that you need incredibly high temperatures and pressures to force the nuclei together. That's why we can harness fission in power stations today, but fusion power is still being developed by scientists.
For your exams, remember that chain reactions in fission occur because each splitting nucleus releases multiple neutrons. When control rods absorb more neutrons, fewer are available to cause splits, so the reaction slows down.
Top Tip: Don't say nuclei "react" together in fusion - they "join" or "combine" together. Getting the terminology right shows examiners you really understand the process!