Nuclear fusion is when small atoms combine to form larger ones, releasing enormous energy. It's how the sun works. Scientists are trying to recreate it on Earth for unlimited clean energy — we're getting close but not quite there yet.
Everything around you is made of tiny, tiny pieces called atoms. They're so small you can't see them even with a magnifying glass.
The sun is super hot — so hot that atoms crash into each other really, really hard. When they crash hard enough, they stick together and become a bigger atom.
When atoms stick together like this, they release a HUGE amount of energy. That's why the sun is so bright and warm!
Scientists want to do the same thing here on Earth to make electricity. It's like having a tiny piece of the sun in a special container.
Fusion is literally creating new elements — something medieval alchemists dreamed of. When two hydrogen atoms fuse, they become helium plus energy.
The challenge: atoms are positively charged and repel each other like magnets with the same pole. To overcome this, you need extreme conditions:
1920s: Scientists realize the sun runs on fusion. 1952: First hydrogen bomb proves fusion works (uncontrolled). 1958: First fusion reactor designs. 2022: First "ignition" — more energy out than laser energy in (NIF). 2025: Multiple startups race toward commercial reactors.
The promise: One gallon of seawater contains enough hydrogen for fusion energy equivalent to 300 gallons of gasoline.
The most accessible fusion reaction uses deuterium (D) and tritium (T), both hydrogen isotopes:
This releases 17.6 MeV per reaction — about 4x more energy per nucleon than fission. The neutron carries most of the energy, which is captured as heat.
Two main approaches to confinement:
For net energy gain, you need: n × τ × T > threshold
Where n = plasma density, τ = confinement time, T = temperature. This "triple product" must exceed ~3×10²¹ keV·s/m³ for D-T fusion.
The fusion community distinguishes between different definitions of "breakeven":
NIF's 2022 "ignition" achieved Qplasma > 1, but Qeng was about 0.01 (the lasers consumed 300 MJ to deliver 2 MJ to the target). Commercial viability requires Qeng > 10-20.
14.1 MeV neutrons cause severe radiation damage to reactor walls. Options include:
• Reduced-activation ferritic-martensitic steels (RAFM)
• Silicon carbide composites
• Liquid metal blankets (Li, PbLi) for neutron moderation and tritium breeding
Tritium is rare (12.3 year half-life). Reactors must breed it: Li⁶ + n → T + He⁴. Achieving tritium self-sufficiency (breeding ratio > 1) is a critical unsolved challenge.
While D-T offers the lowest ignition threshold, advanced fuel cycles avoid the neutron problem:
Novel confinement concepts gaining traction:
Levelized cost targets: <$50/MWh to compete with renewables+storage. Key variables:
• Capital cost (dominant — current estimates $5-15B for first plants)
• Capacity factor (tokamaks: pulsed vs. steady-state operation)
• Availability (neutron damage limits component lifetime to ~5-10 years)
Private investment exceeded $6B by 2024, with 40+ companies pursuing various approaches.
The consensus timeline has shifted from "30 years away forever" to potential pilot plants by 2030-2035, with commercial deployment possible by 2040 if current progress continues.