Chicago Pile-1

Reactor · 1942

Year: 1942
Kind: Reactor
Materials: 45 tonnes of uranium, 360 tonnes of graphite, cadmium rods, and a man with an axe to cut a rope holding a safety rod.
Efficiency: It made no useful power; it proved the reaction.
Used In: The proof that led to every reactor since.
Power Density: Half a watt.
Cycle: None

How It Works

Uranium lumps in a lattice of graphite blocks, stacked by hand under a squash court. The graphite slowed neutrons enough for uranium-235 to capture them; cadmium rods soaked up neutrons to hold the reaction; on 2 December 1942 the rods were withdrawn and the chain reaction sustained itself for 28 minutes at half a watt.

Inventors

Enrico Fermi

Equations

Half-Life Radioactive Decay Law Mass–Energy Equivalence

Elements

Carbon Uranium Cadmium

Referenced by

element

Cadmium Carbon Uranium

equation

Half-Life Mass–Energy Equivalence Radioactive Decay Law

researcher

Enrico Fermi

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From the Machines database in Notion, last edited 2026-08-16. This page is the row, rendered by the build; nothing on it is written by hand.