When President Roosevelt in December 1942 authorized the
Manhattan Project, the Oak Ridge site in eastern Tennessee had
already been obtained and plans laid for an air-cooled
experimental pile, a pilot chemical separation plant, and
support facilities. The X-10 Graphite Reactor, designed and
built in ten months, went into operation on November 4, 1943.
The X-10 used neutrons emitted in the fission of uranium-235 to
convert uranium-238 into a new element, plutonium-239. The
reactor consists of a huge block of graphite, measuring 24 feet
on each side, surrounded by several feet of high-density
concrete as a radiation shield. The block is pierced by 1,248
horizontal diamond-shaped channels in which rows of cylindrical
uranium slugs formed long rods. Cooling air circulated through
the channels on all sides of the slugs. After a period of
operation, operators pushed fresh slugs into the channels from
the face of the pile and the irradiated slugs would fall from
the back wall through a chute into an underwater buck