Chicago Pile-1 by Ciro Santilli 34 Updated +Created
The first human-made nuclear chain reaction.
Video 1.
Getting funding for the Chicago Pile Edward Teller interview by Web of Stories (1996)
Source.
Video 2.
German graphite from The Genius Behind the Bomb (1992)
Source. Graphite was expensive because it had to be boron-free, since boron absorbs neutrons. But a boron process was the main way to make graphite. This type of pure graphite is known as nuclear graphite.