Nuclear Fission

NUCLEAR FISSION is the SPLITTING of heavy atomic nuclei (usually uranium-235 or plutonium-239) into smaller pieces. The split releases ENORMOUS energy — millions of times more per atom than chemical reactions. Fission powers NUCLEAR REACTORS (controlled) and ATOMIC BOMBS (uncontrolled). Discovered in 1938, it changed history.

How it works. A neutron strikes a U-235 nucleus. The nucleus becomes unstable, splits into smaller nuclei (like Krypton and Barium), and releases 2-3 neutrons + huge energy. Those neutrons can hit other U-235 nuclei → CHAIN REACTION. In a reactor, control rods (which absorb neutrons) keep the chain reaction at a steady, manageable rate. In a bomb, no control — explosive growth.

Pros and cons of nuclear power. PROS: Low CO2 emissions; high power density; reliable baseload. CONS: Radioactive waste (lasts thousands of years); accident risks (Chernobyl, Fukushima); high construction costs; weapons proliferation concerns. Modern reactors (Generation IV designs) are safer and produce less waste. Nuclear's role in addressing climate change is hotly debated.

Nuclear fission is one of the 20th century's most consequential discoveries — for both peaceful uses and weapons. Its future role in energy is one of our most important policy questions.