Oak Ridge National Lab’s graphite reactor, an APS Historic Site, powered plutonium production for the Manhattan Project
The reactor, which achieved criticality in just nine months, had both wartime and peacetime utility.
As U.S. scientists raced to develop the first atomic weapons at the height of World II, one group of researchers, tasked with producing plutonium, had to grapple with its own internal discord.
The Manhattan Project needed vast quantities of plutonium, key to the creation of the bomb. In early 1943, two teams of researchers — scientists from the University of Chicago's Metallurgical ("Met") Laboratory and engineers from the chemical company DuPont — were directed to design a machine for the job at Oak Ridge National Laboratory in Tennessee.
The technical challenges were enormous. The researchers needed to scale the production of plutonium from miniscule amounts to kilogram quantities, a feat that would require creating a nuclear reactor more powerful than any before. But although the two teams were united in their mission, they faced friction.
"There were matters of culture, there were matters of practice, and there were matters of prejudice," says Sherrell Greene, retired ORNL director of nuclear technology programs and research reactor development programs. Many of the University of Chicago scientists who were European were wary of getting involved with military projects because of "the distrust of the industrial military complex that evolved in Europe after World War I," he says. Some of the engineers were distrustful of the scientists.
The scientists also underestimated the challenges involved with plutonium production, including uncertainty around how much plutonium would be needed. "The Manhattan project was about turning the discovery of a physical phenomenon — actually, multiple physical phenomena — into an industrial-scale machine," Greene adds. "It's one thing to do an experiment in a room the size of your garage; it's another thing to produce a machine that runs 24 hours a day, seven days a week, cranking out product."
Still, the team forged ahead, building trust through "the passage back and forth of blueprints, drawings, letters, memos and meetings," Greene says.
On Nov. 4, 1943, just nine months after construction began, the Oak Ridge graphite reactor became the world’s second nuclear reactor to achieve criticality — meaning that enough neutrons are released to sustain an ongoing series of reactions — and the first designed for continuous use. Within a few months, the team was producing the world’s first few grams of plutonium.
The graphite reactor, also called the X-10 Pile or Clinton Pile, churned out plutonium for the Manhattan Project. The researchers "almost achieved, from an engineering perspective, irreducible complexity,” says Greene.
After World War II, concerns arose that the site that's now ORNL would be shuttered. However, the graphite reactor "was a life-preserver for the laboratory," Greene says. Even in peacetime, it was used to achieve “an astounding range of applicability” in nuclear energy and medicine, Greene says.
"It had proven itself in wartime, and what it did — by being immediately turned to the production of a wide variety of radioisotopes, both medical and industrial experimental isotopes — is it gave a reason to keep the laboratory operating while it continued to explore and understand the capabilities of the reactors for research and also to build new missions for itself," Greene says.
Mickey Wade, associate laboratory director for ORNL’s fusion and fission energy and science directorate and an APS Fellow and member, championed the reactor’s designation as an APS Historic Site, in part because of the reactor’s far-reaching impacts — including its role in the development of nuclear energy.
"It was truly a demonstration of the ability to generate energy from a nuclear reactor for electricity purposes,” Wade says. The graphite reactor had other broad research applications as well. "One of the earliest things that was done on the graphite reactor was to put a neutron diffraction capability on it, which now we call neutron scattering” — a technique that has since been used to study fuels, batteries, and other materials.
The graphite reactor was shut down in 1963 and has been a museum since then. Today, ORNL visitors can explore the history and impact of the sleeping giant.
According to Wade and Greene, the graphite reactor is an example of what can be achieved through multidisciplinary collaboration. "[It] was not imagined to be a neutron scattering device or an isotope production device," Wade says. "This is all about the learning process, the discovery process we have as scientists, as we take what's available to us.”
By first learning "one thing or two things," he adds, the result is "a cascading effect" that results in "a capability that's world-changing."
Learn more about the APS Historic Sites program and APS’ work to celebrate physics history, or become a member to advance your career and shape the future of physics.