Oak Ridge X-10: 1943- Graphite Reactor Goes Critical

US DEPARTMENT OF ENERGY

The X-10 Graphite Reactor is located on the secure grounds of Oak Ridge National Laboratory (ORNL). In-person visitation is only authorized via guided tours.

Text at the top of this panel reads,“At 5 am on November 4, spontaneous nuclear chain reactions begin at the Graphite Reactor.”

To the left is an image of the wall mural at the entrance to this room showing a night scene in which a man rushes towards a small house where another man peeps from the door. To the right is a diagram showing the fission cascade of uranium-235. At top a neutron hits a U-235 nucleus. Arrows from that show two fission fragments, a uranium-238 nucleus, which changes to plutonium, and one to three neutrons from the fission process. One of those neutrons hits another U-235 nucleus and the process repeats. The caption reads,“Schematic diagram of chain reaction from fission, neglecting effect of neutron speed. In an explosive reaction, the number of neutrons multiplies indefinitely. In a controlled reaction, the number of neutrons builds up to a certain level and then remains constant.”

Below to the left is a photograph of two men in coveralls leaning over the sides of a sunken enclosure with two heavy metal open boxes at the bottom. One man uses a long metal pole to maneuver the items below. Text reads,“The first uranium slugs were transferred from the reactor to the pilot plant for processing to extract plutonium. A third of a ton of uranium has been irradiated.”

At bottom left is a photograph of a small crate in the open back of a truck. A man kneels beside the crate writing with a pen. To the left a man in a guard’s uniform looks on. Text reads,“A secret courier transports 1.54 milligrams of purified plutonium from Oak Ridge to the University of Chicago.”

At bottom right is a photograph of the loading face of the Graphite Reactor with two operators using a push rod at one of the channels. Two other men can be seen through the windows of the control room at upper left. A smaller photograph shows a man next to the loading face putting a metal cylinder into a channel as he holds several other cylinders in his other hand. Text reads,“After going critical the Graphite Reactor serves as a research site and pilot plant for full-scale plutonium production reactors being built at Hanford, Washington. It also produces gram quantities of plutonium for use at Los Alamos, New Mexico, in testing fission bomb designs.”