Incoming links: Nuclear chain reaction
The first human-made nuclear chain reaction.
- youtu.be/mnScq24BEmc?t=114 the main cost for the reactor was the graphite. Presumably they already had the uranium in hand?. Edit, no, it is because it was a specialized graphite: Video 2. "German graphite from The Genius Behind the Bomb (1992)", i.e. nuclear graphite.
Some of the most notable ones:
- 1942: Chicago Pile-1: the first human-made nuclear chain reaction.
- 1943: X-10 Graphite Reactor: an intermediate step between the nuclear chain reaction prototype Chicago Pile-1 and the full blown mass production at Hanford site. Located in the Oak Ridge National Laboratory.
- 1944: B Reactor at the Hanford site produced the plutonium used for Trinity and Fat Man
This was an intermediate step between the nuclear chain reaction prototype Chicago Pile-1 and the full blown plutonium mass production at Hanford site. Located in the Oak Ridge National Laboratory.
Exterior of the X-10 Graphite Reactor in 1950
. Source. 
Workers loading Uranium into the X-10 Graphite Reactor with a rod
. Source. 