The “calutron” named Alpha I at Oak Ridge Laboratory; also called a “racetrack”, this device used huge magnets to separate uranium for the Manhattan Project.
Via: Los Alamos National Labs (including very high-resolution version)
Nuclear Explosion
Strange, super-minimalistic raw film of a test nuclear explosion from 1953. After several minutes of flickering gray and quiet ambient sound, the blast fills the screen all-white, then receeds to a silent, washed-out mushroom cloud. This is followed nearly a minute later by a sharp, dull blast sound (since the speed of sound is much slower than light). The video concludes with several minutes of gray clouds.
Via: Nuclear Secrecy blog