Higher Tier Only: Why Fusion Is Difficult to Achieve on Earth

🎓 Higher Tier Only: Why Fusion Is Difficult to Achieve on Earth

For fusion to occur, nuclei must be brought within ~1 fm (femtometre = 10⁻¹⁵ m) of each other so the strong nuclear force can overcome electrostatic repulsion. This requires kinetic energies equivalent to temperatures above 10⁸ K.

At these temperatures, atoms are fully ionised — all electrons have been stripped away. The result is a plasma (superheated ionised gas). No material container can hold plasma at 100 million°C without melting. Solutions being tested:

• Tokamak (ITER, JET): Strong magnetic fields contain the plasma in a donut-shaped vessel
• Inertial confinement (NIF, USA): Laser beams compress a tiny pellet of deuterium-tritium very rapidly

The major challenge is achieving "net energy gain" — the fusion must release more energy than was put in to heat and confine the plasma. As of 2024, NIF has achieved this briefly; a commercial reactor is still decades away.