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Chapter 1: Wartime Laboratory

Spreading out along broad valleys cut by the Clinch River and framed by the foothills of the
Appalachian Mountains, Oak Ridge seems an unlikely setting for events that would change the course of history. 

Clinton Laboratories, X-10 site, including the Graphite Reactor, under construction in October 1943.
Clinton Laboratories, X-10 site, including the Graphite Reactor, under construction in October 1943.

At the time of the Japanese attack on Pearl Harbor on December 7, 1941, century-old family farms and small crossroads communities such as Scarborough, Wheat, Robertsville, and Elza occupied what was about to become the Oak Ridge Reservation. Outsiders considered the region a quaint reminder of the 19th-century frontier that time and progress had passed by. (See related article, Atoms in Appalachia.)

In truth, the area experienced enormous change during the early 20th century. On the up side, it felt the effects of Henry Ford's automobile and shared, to some extent, the comforts afforded by electricity; on the down side, it reeled from the aftershocks of the Great Depression that rocked the economy and exerted additional pressures on the region's fragile natural resources. Located just 25 miles from the Tennessee Valley Authority's (TVA's) corporate headquarters at Knoxville and just a few miles below TVA's huge Norris Dam on the Clinch River, the area was, in fact, a focal point of one of the nation's boldest experiments in social and economic engineering. The tiny Wheat community, for example, had been selected for a TVA inspired venture in cooperative agriculture. (See related article, ORNL and TVA: Partnership for East Tennessee.)

Residents of the Oak Ridge area in 1941 did not feel bypassed by history. But even the advent 
of the automobile, the introduction of electricity, the hardships of the Great Depression, and 
direct participation in an unprecedented government-sponsored social experiment did not prepare them for what was about to happen. 

In early 1942, the Army Corps of Engineers designated a 59,000-acre (146,000-hectare) swatch of land between Black Oak Ridge to the north and the Clinch River to the south as a federal reserve to serve as one of three sites nationwide for the development of the atomic bomb. About 3000 residents received court orders to vacate within weeks the homes that their families had occupied for generations. Thousands of scientists, engineers, and workers swarmed into Oak Ridge to build and operate three huge facilities that would change the history of the region and the world forever. 

On the reservation's western edge rose K-25, or the gaseous diffusion plant, a warehouse like 
building covering more area than any structure ever built. Completed at a cost of $500 million 
and operated by 12,000 workers, the K-25 Plant separated uranium-235 from uranium-238.    On its northern edge grew the workers' city named Oak Ridge; south of the city rose the Y-12 Plant, where an electromagnetic method was used to separate uranium-235. Built for $427 million, the Y-12 Plant employed 22,000 workers. Near the reservation's southwest corner, about 10 miles from Y-12, was the third plant, X-10. 

Oak Ridge area farmers on the rugged Appalachian ridges and valleys still plowed with mules before 1942.
Oak Ridge area farmers on the rugged Appalachian ridges and valleys still plowed with mules before 1942.

Built between February and November 1943 for $12 million and employing only 1513 people during the war, X-10 was much smaller than K-25 and Y-12. As a pilot plant for the larger plutonium plant built at Hanford, Washington, X-10 used neutrons emitted in the fission of uranium-235 to convert uranium-238 into a new element, plutonium-239. During the war, X-10 was called Clinton Laboratories, named after the nearby county seat of rural Anderson County; in 1948, Clinton Laboratories became Oak Ridge National Laboratory.

The Laboratory, which celebrated its 50th anniversary in 1993, has evolved from a war emergency pilot plant operated under the cloak of secrecy into one of the nation's outstanding centers for energy, environmental, and basic scientific research and technology development. It currently employs about 4500 people, including many scientists recognized internationally as experts in their fields. Laboratory endeavors range from studies of nuclear chemistry and physics to inquiries into global warming, energy conservation, high-temperature superconductivity, and new materials. Its institutional roots, however, lie with the awesome power released by the splitting of atoms. 

The Laboratory's nuclear roots run deep and nourish much of its research on improving the safety of commercial nuclear power, identifying effective methods of managing nuclear waste, and achieving practical fusion power. The roots are not only deep, they are broadly international.

The rural lifestyle of the Oak Ridge area was forever changed by the local Manhattan Project
The rural lifestyle of the Oak Ridge area was forever changed by the local Manhattan Project plants.
Supreme irony marks the Laboratory's history. The institution was born during war and was propelled by a sense of high-stakes competition and urgency: if Hitler's scientists had developed the atomic bomb first, Nazi Germany might have placed the entire world under a fascist fist. Yet, the Laboratory's present scientific excellence could not have been achieved without the camaraderie and sense of collective purpose that propels international science. Created to build a weapon capable of unprecedented destruction, the Laboratory became an institution that nurtures the ability of people to understand and transform their universe for the better. For this reason and more, its story should be told.


The history of Oak Ridge National Laboratory begins in three distinctly different places: Albert Einstein's retreat on Long Island, New York; the executive offices of the White House in Washington, D.C.; and university laboratories throughout the nation and overseas, especially at the University of Chicago. 

At its highest level, the scientific community is international in scope. As fascist dictators seized power in Europe during the 1930s, some of the continent's greatest scientists fled to join colleagues in Britain and America. Among them were the German, Albert Einstein; the Italian, Enrico Fermi; and Hungarians, Edward Teller, Leo Szilard, John von Neumann, and Eugene Wigner. (See related article, Revolving Door of Success.)

These brilliant minds joined cooperative international efforts to develop atomic weapons and, later, nuclear energy, significantly influencing 20th-century history in general and the history of Oak Ridge National Laboratory in particular. Eugene Wigner, in fact, has been called the "patron saint" of the Laboratory. 

Eugene Wigner, a pioneering chemical engineer and physicist from Budapest, may have been the least known of the immigrant scientists. Completing a chemical engineering degree in Berlin in 1925, Wigner took a job at a Budapest tannery where his father also worked. Physics was his evening and weekend hobby. His friend John von Neumann called his attention to mathematical group theory, and Wigner soon published a series of technical papers that applied symmetry principles to problems of quantum mechanics. After two years at the tannery, he accepted an assistantship in theoretical physics in Berlin at the princely salary of $32 per month.

In Berlin, Wigner established an international reputation as a physicist, and in 1930 Princeton University hired both him and von Neumann, each on a half-time basis. For a few years, the two friends commuted every six months between Berlin and Princeton until the Nazi government terminated their employment. 

Wigner then went to the University of Wisconsin to work. There he devised a fundamental formula that enabled scientists to understand a neutron's energy variations when channeled through materials having different absorption capabilities. At Wisconsin, he also discovered a university life that reached beyond academic circles to plain people who grew potatoes and milked cows, and he met scientists who repaired their cars and made home improvements. He later said that at Wisconsin he came to love his adopted country.

Returning to Princeton, he studied solid-state physics and supervised the work of graduate students. His first student, Frederick Seitz, later became president of the National Academy of Sciences and of Rockefeller University; his second, John Bardeen, developed the transistor and twice received the Nobel Prize for physics.

The increasing strength of fascist governments in Europe troubled Wigner deeply. As a youngster, he had seen Hungary's enfeebled monarchy supplanted by brutal communist and then fascist governments. From personal experience, he developed an implacable enmity toward totalitarian regimes. When he learned in early 1939 that two German chemists had discovered nuclear fission in uranium, Wigner recognized that this discovery could lead to both weapons of mass destruction and abundant energy for mass consumption. Fearing Nazi Germany would initiate a crash program to develop atomic weapons, Wigner urged the United States government to support research on nuclear fission. He found an ally in his fellow countryman Leo Szilard, who in Hungary had attended the same schools as Wigner before emigrating to the United States.

Studying nuclear fission with Enrico Fermi at Columbia University in New York City, Szilard needed additional funds to continue his experiments with uranium and graphite. Wigner gladly lent his support to Szilard's efforts. Because other scientists were lobbying authorities with their own weapon schemes, Wigner and Szilard found their campaign for nuclear fission research moved so slowly they seemed to be "swimming in syrup." 

Albert Einstein signed a letter to President Roosevelt in 1939 that called for the investigation of uranium fission as a potential weapon.
Albert Einstein signed a letter to President Roosevelt in 1939 that called for the investigation of uranium fission as a potential weapon.

Thinking that Washington officials would be more likely to listen to the famous Albert Einstein, an old acquaintance from Berlin, Wigner and Szilard sought him out in July 1939. Learning he had left Princeton to vacation on Long Island, they drove there, found Einstein's cabin, and explained to him why the United States should initiate fission research before German scientists developed an atomic weapon. As Wigner later recalled:

Einstein understood it in half a minute. It was really uncanny how he dictated a letter in German with enormous readiness. It is not easy to formulate and phrase things at once in a printable manner. He did. I translated that into English. Szilard and Teller went out, and Einstein signed it. Alexander Sachs took it to Washington. This helped greatly in initiating the uranium project.

In October 1939, President Franklin Roosevelt appointed a committee of prominent scientists and government administrators to manage federally funded scientific research. Wigner, Szilard, and Edward Teller met with the committee and requested $6000 to purchase graphite for fission experiments. They listened to an Army officer on the committee expound at length upon his theory that civilian and troop morale, not experimental weapons, won wars. 

Szilard later recalled that "suddenly Wigner, the most polite of us, interrupted him. He said in his high-pitched voice that it was very interesting for him to hear this, and if this is correct, perhaps one should take a second look at the budget of the Army, and maybe the budget should be cut." The officer glared in silence at Wigner, and the committee agreed to provide funds for the experiment.

Four nuclear physicists who advanced our understanding of nuclear power: left to right, Walter
Zinn, Leo Szilard, Eugene Wigner, and Alvin Weinberg.
Four nuclear physicists who advanced our understanding of nuclear power: left to right, Walter Zinn, Leo Szilard, Eugene Wigner, and Alvin Weinberg.

 This first $6000 of federal funding for nuclear energy research launched a vast, multibillion-dollar program that has continued unabated under the successive management of the U.S. Army, Atomic Energy Commission, Energy Research and Development Administration, and Department of Energy. The program has had direct and lasting ties to atomic research, development, and production sites across the United States, including Oak Ridge.

The initial funds for the uranium and graphite experiments, however, were not released until late 1940. Wigner became increasingly exasperated as the irreplaceable months passed. After the war, he contended that the delay, largely the result of bureaucratic footdragging, cost many lives and billions of dollars.

American scientists, nevertheless, made vital advances in the interim. At Columbia University, in March 1940, John Dunning and his colleagues demonstrated that fission occurred more readily in the isotope uranium-235 than in uranium-238, but only one of 140 uranium atoms was the 235 isotope. 

Using cyclotrons at the University of California, in 1940 Edwin McMillan and Philip Abelson discovered element 93, the first element heavier than uranium, atomic number 92. They named this transuranium element neptunium. A year later, Glenn Seaborg and colleagues discovered element 94 (the decay product of newly synthesized number 93), named it plutonium (in the planetary sequence Uranus, Neptune, Pluto) and demonstrated its fissionability. Two doors to the atomic weapons and energy thus were opened for future exploration: uranium-235 could be separated from uranium-238 for weapons use, and uranium-238 could be bombarded with neutrons—in a nuclear pile or reactor—to produce plutonium that could then be chemically extracted for weapons production.


The day after the Japanese attacked Pearl Harbor, Arthur Compton, a Nobel laureate at the University of Chicago, contacted Eugene Wigner to discuss the possibility of consolidating nationwide plutonium research efforts in Chicago. At meetings in January 1942, Compton brought together scientists experimenting with nuclear chain reactions at Princeton and Columbia universities with those investigating plutonium chemistry at the University of California to outline the plutonium project's objectives. Compton's schedule called for determining the feasibility of a nuclear chain reaction by July 1942, achieving the first self-sustaining chain reaction by January 1943, extracting the first plutonium from irradiated uranium-238 by January 1944, and producing the first atomic bomb by January 1945. In the end, all these deadlines were met except the last, which occurred six months later than planned.

To accomplish these objectives, Compton formed a "Metallurgical Laboratory" as cover at the University of Chicago and brought scientists from the east and west coasts to this central location to develop chain-reacting "piles" for plutonium production, devise methods for extracting plutonium from the irradiated uranium, and design a weapon. Remaining in charge of the overall project, Compton selected Richard Doan as director of the Metallurgical Laboratory. An Indiana native, Doan had earned a physics degree from the University of Chicago in 1926 and had been a researcher for Western Electric and Phillips Petroleum before the war.

Compton also placed Glenn Seaborg in charge of the research on plutonium chemistry and assigned him the task of devising methods to separate plutonium from irradiated uranium in quantities sufficient for bomb production. To coordinate the theoretical and experimental phases of research associated with a chain reaction, Compton chose Eugene Wigner, Enrico Fermi, and Samuel Allison. Fermi continued his experiments with ever-larger piles of uranium and graphite, while Samuel Allison directed a cyclotron group, including Canadian Arthur Snell, who assessed nuclear activities in uranium and graphite piles. Wigner and Snell later joined the X-10 staff.

Eugene Wigner headed the theoretical physics group crowded into Eckart Hall on the University of Chicago campus. His "brain trust" of 20 scientists studied the arrangement, or lattice, of uranium and control materials for achieving a chain reaction and planned the design of nuclear reactors. Among Wigner's group were Gale Young, Kay Way, and Alvin Weinberg, all of whom later moved to Oak Ridge.

Under this University of Chicago football stadium, scientists achieved the world's first nuclear chain reaction.
Under this University of Chicago football stadium, scientists achieved the world's first nuclear chain reaction.

Having a chemical engineering background, Wigner also offered advice to Glenn Seaborg and his staff of University of California chemists, who were seeking to separate traces of plutonium from uranium irradiated in cyclotrons. This task was particularly challenging because to that point no one had isolated even a visible speck of plutonium. By September 1942, the team had obtained a few micrograms of plutonium for experimentation, but they needed much more for additional analysis.

In 1942, Compton brought Martin Whitaker, a North Carolinian who chaired New York University's physics department, to Chicago to help Enrico Fermi and Walter Zinn build subcritical uranium and graphite piles. He later put Whitaker in charge of a laboratory under construction in the Argonne forest preserve on Chicago's southwest side. It was here that Compton initially planned to bring the first nuclear pile to critical mass. A strike by construction workers, however, prevented the laboratory's timely completion. As a result, Compton and Fermi decided to build a graphite pile housed in a squash court under the stands of the University of Chicago's stadium.

Arthur Compton and his assistant Richard Doan headed the Metallurgical Laboratory at the
University of Chicago. Compton made Doan research director at Clinton Laboratories
in 1943.
Arthur Compton and his assistant Richard Doan headed the Metallurgical Laboratory at the University of Chicago. Compton made Doan research director at Clinton Laboratories in 1943.

Leo Szilard and later Norman Hilberry were placed in charge of supplying materials for the pile experiments. They obtained impurity-free graphite from the National Carbon Company in Cleveland, Ohio, and the purest uranium metal available from Frank Spedding's research team at Ames, Iowa. George Boyd and chemists at Chicago analyzed the materials to ensure the absence of impurities that might interfere with a nuclear reaction, and Fermi and his colleagues put the materials into a series of subcritical uranium and graphite piles built in what was to become the world's most famous squash court. Fermi called them piles because, as the name implies, they were stacks or piles of graphite blocks with lumps of uranium interspersed between them in specific lattice arrangements. Uranium formed the "core," or source of neutrons, and graphite served as a "moderator," slowing the neutrons to facilitate nuclear fission. In truth, the piles were small, subcritical nuclear reactors cooled by air, but the name reactor did not replace pile until 1952. Fermi gradually built larger subcritical piles, carefully measuring and recording neutron activity within them, edging toward the point at which the pile would reach "critical mass" and the reaction would be self-sustaining.

On December 2, 1942, Fermi, Whitaker, and Zinn piled tons of graphite and uranium on the squash court to demonstrate a controlled nuclear reaction for visiting dignitaries standing on a balcony. Controlling the reaction with a rod coated with cadmium, a neutron-absorbing material,  Fermi directed the phased withdrawal of the rod, carefully monitoring the increased neutron flux within the pile. The pile went "critical," achieving self-sustaining status at 3:20 p.m., an event later hailed as the dawn of the Atomic Age. Having no shield to prevent a release of radiation, Fermi briefly operated this Chicago Pile 1, disassembled it, and in 1943 rebuilt it with concrete radiation-protecting shielding as Chicago Pile 2 at the Argonne laboratory.

Physicist Enrico Fermi directed design of the Chicago Pile 1 and Graphite Reactor at Oak Ridge.
Physicist Enrico Fermi directed design of the Chicago Pile 1 and Graphite Reactor at Oak Ridge.

Richard Fox, who rigged the control-rod mechanism for Fermi's pile, stood behind Fermi worrying throughout the first critical experiment. "The manual speed control was nothing more elaborate than a variable resistor," Fox recalled, "with a piece of cotton clothesline over a pulley and two lead weights to make it `fail-safe' and return to its zero position when released." Once the experiment succeeded and his concern that the clothesline would slip off the pulley proved unfounded, Fox recalled his elation: "It was as though we had discovered fire!"

After the dignitaries departed, Wigner brought out a bottle of Italian Chianti in honor of Fermi's achievement and shared toasts with the workers. He had carried the bottle from Princeton and later claimed it had taken more foresight to anticipate that the war would make Chianti a rare wine than to predict that Fermi's chain reaction would succeed. Among the celebrants were Richard Fox and Ernest Wollan, who had monitored and recorded the radiation emitted by the reaction. Both left Chicago for Oak Ridge in 1943. Wollan conducted neutron diffraction experiments, and Fox applied his talents in the Instrumentation and Controls Division, where he worked for half a century.

Sketch of the
1942 scene when the nuclear pile under the University of Chicago stadium
went critical.
Sketch of the 1942 scene when the nuclear pile under the University of Chicago stadium went critical.

Producing sufficient plutonium for weapons required the construction of large reactors operating at high power levels and releasing large amounts of heat and radiation. Metallurgical Laboratory engineers Thomas Moore and Miles Leverett, both recruited from the Humble Oil Company, began an intensive investigation of potentially larger reactor designs. Scaling up Fermi's pile would not do, because extracting plutonium from the uranium would require tearing the pile apart each time and then reassembling it—a risky, time-consuming exercise. Moore and Leverett developed a new design that used helium gas under pressure as the coolant to remove heat from the pile during a nuclear reaction. To extract the uranium without disassembling the graphite moderator, they designed holes or channels that extended through the graphite to allow the insertion of uranium rods. The rods could then be removed after they had been irradiated.

Scientists agreed that thick shells of concrete could contain the radiation from reactors, but they disagreed about methods for removing the heat. Fermi wanted an air-cooled reactor, with fans forcing air through channels alongside the uranium rods. Moore and Leverett preferred using helium gas under pressure. Szilard favored a liquid bismuth metal coolant, similar to the system he and Einstein had patented for refrigerators. And Wigner preferred plain river water, with uranium rods encased in aluminum to protect them against water corrosion. Wigner's water-cooling plan eventually was adopted for use in large reactors, but not before the decision to build Fermi's air-cooled graphite and uranium pilot reactor at Oak Ridge had been made.

The proposed pilot reactor would test control and operations procedures and provide the larger quantities of plutonium required by the project's chemists. In mid-1942, Glenn Seaborg's group had used a lanthanum fluoride carrier process to separate micrograms of plutonium from uranium irradiated in cyclotrons; they now sought a means to achieve the separation on an industrial scale. In addition, Isadore Perlman, Charles Coryell, Milton Burton, George Boyd, and James Franck headed teams investigating the chemical and radiation novelties of plutonium, radiation, and fission products created during nuclear reactions. 

Among the various methods investigated for separating plutonium were the ion-exchange and solvent-extraction processes. Although not adopted in 1943, these studies provided foundations for the postwar separation of radioisotopes and the widely used solvent-extraction methods for recovering uranium and plutonium from spent nuclear fuel. In 1943, Seaborg and Du Pont chemist Charles Cooper settled on a small pilot plant using the lanthanum fluoride carrier built on the Chicago campus and another pilot plant using a bismuth phosphate carrier planned for Oak Ridge. In both cases, the separation would have to be conducted by remote control in "hot cells" encased in thick concrete to protect the chemists from radiation.


As the Metallurgical Laboratory's research continued, studies began of potential sites for the planned industrial-scale uranium separation plants and pilot plutonium production and separation facilities. An isolated inland site with plenty of water and abundant electric power was desired. 

At the recommendation of the War Production Board, Compton's chief of engineering, Thomas Moore, and two consulting engineers visited East Tennessee in April 1942. They found a desirable site bordering the Clinch River between the small towns of Clinton and Kingston that was served by two railroads and Tennessee Valley Authority electric power. Arthur Compton then inspected the site, approved it, and visited David Lilienthal, chairman of the TVA, to describe the unfolding plans to purchase the land.

Lilienthal was dismayed by news that land near Clinton would be taken. He objected that the site included land selected for an agricultural improvement program and proposed instead that Compton choose a site in western Kentucky near Paducah.

Fifty years after the momentous events at Chicago's Stagg Field, a piece of history was found at ORNL. Kermit Campbell holds a plastic bag containing uranium-238, shipped
from Stagg Field, in the can in his arm.
Fifty years after the momentous events at Chicago's Stagg Field, a piece of history was found at ORNL. Kermit Campbell holds a plastic bag containing uranium-238, shipped from Stagg Field, in the can in his arm.

Compton refused to consider Lilienthal's proposal and advised him that the land in East Tennessee would be taken through court action for immediate use. He urged Lilienthal not to question his judgment or inquire into the reasons for the purchase. "It was a bad precedent," Lilienthal later complained. "That particular site was not essential; another involving far less disruption in people's lives would have served as well, but arbitrary bureaucracy, made doubly powerful by military secrecy, had its way."

In June 1942, President Roosevelt assigned to the Army the management of uranium and plutonium plant construction and nuclear weapons production. High-ranking Army officials, in turn, delegated this duty to Colonel James Marshall, commander of the Manhattan Engineer District headquartered initially in New York City and later relocated to Oak Ridge. Because Fermi had not yet achieved a self-sustaining chain reaction, Marshall and Army authorities postponed their efforts to acquire the land. The delay disturbed some scientists anxious not to lose ground to the Germans. It also perturbed the hard-driving deputy chief of the U.S. Army Corps of Engineers, Brigadier General Leslie Groves. (See related article, Leslie R. Groves: Manhattan Project's Main Man.)

Given command of the Manhattan Project in September 1942, Groves ordered the immediate purchase of the reservation, first given the code name Kingston Demolition Range after the town south of the reservation and later renamed Clinton Engineering Works after the town to the north. The Army sent an affable Kentuckian, Fred Morgan, to open a real estate office near the site and purchase the land through court condemnation, thereby securing clear title for its immediate use. About 1000 families on the reservation were paid for their land and forced to relocate. Existing structures were demolished or converted to other, war-related uses. New Bethel Baptist Church at the X-10 site, for example, was used for storage, meetings, and experiments.

Richard Fox participated in the achievement of the first nuclear chain reaction at the University of Chicago in December 1942 and then transferred to Oak Ridge, where he stayed for half a century.
Richard Fox participated in the achievement of the first nuclear chain reaction at the University of Chicago in December 1942 and then transferred to Oak Ridge, where he stayed for half a century.

To speed production of weapons materials, Groves selected experienced industrial contractors to build and operate the plants. In January 1943, he persuaded Du Pont to initiate construction of both the pilot facilities at X-10 in Oak Ridge and the full-scale reactors to be built later in Hanford, Washington. Involved in too many military projects and reluctant to undertake the work at X-10, Du Pont executives were persuaded to accept Groves' request partly through appeals to their patriotism. The contract stipulated that Du Pont would withdraw from the job at war's end, accept no work-related patents, and receive no payment other than their costs plus a $1 profit. After the war, Groves reported with amusement that government auditors allowed Du Pont a profit of only 66 cents because the company had finished its job ahead of schedule.

Groves called on the University of Chicago to operate the pilot plutonium plant planned at X-10. Scientists at the Metallurgical Laboratory in Chicago expressed initial dissatisfaction with this proposal. Wigner and others had wanted to design and construct the plants, and they were not interested in operating them after Du Pont had been given the jobs they had sought. Also, university scientists and administrators preferred building the pilot plant in the Argonne forest convenient to Chicago; the prospect of operating industrial facilities 500 miles from their campus in the remote hills of Tennessee did not elicit much enthusiasm.

Groves and the Army again used appeals to patriotism to help persuade the university to accept the challenge. The compromise called for Chicago to supply the managers and scientists needed for the operations and for Du Pont to mobilize construction and support personnel.


On February 1, 1943, Du Pont started clearing the X-10 site, installing utility systems, and building the first temporary buildings, mostly wooden barracks. In March, construction of six hot cells for plutonium and fission product separation began. The cells had thick concrete walls with removable slab tops for equipment replacement. The cell nearest the nuclear reactor housed a tank for dissolving uranium brought from the reactor through an underground canal; four other cells housed equipment for successive chemical treatment of the uranium—precipitation, oxidation, reduction; a sixth cell stored contaminated equipment removed from the other cells. An adjoining frame structure housed the remote operating gallery and offices.

Other structures rising at X-10 housed chemistry, physics, and health physics laboratories; machine and instrument shops; warehouses; and administration buildings. Because construction of the Y-12 and K-25 plants on the reservation also began in 1943, Du Pont had difficulty finding enough workers. It remedied the shortage by dispatching recruiters throughout the region.

Including the smallest structures, about 150 buildings were completed that summer by 3000 construction workers, at an initial cost of $12 million. Construction materials included 30,000 cubic yards of concrete, 4 million board feet of lumber, 4500 gallons of paint, and 1716 kegs of nails. Buildings went up rapidly, but needs so outran accommodations that a workers' cafeteria operated in a striped circus tent and an old schoolhouse served as office space and a dormitory.

Foundation excavations for the Graphite Reactor began in late April 1943; the reactor's 2-meter- (7-foot)-thick concrete front face was in place by June, and the side and rear walls were constructed in July. The National Carbon Company delivered graphite of the required purity to X-10, where Du Pont built a fabrication shop to machine graphite blocks to the desired dimensions. In September, a crew stacked the first of 73 layers of graphite blocks within the concrete shield to form a cube 7.3 meters (24 feet) on a side and at month's end installed steel trusses to support the concrete lid capping the reactor. Under government contract, the Aluminum Company of America began encasing 60,000 uranium slugs in aluminum for the reactor. Mounted in a building near the reactor, two of the world's largest fans sucked outside air through the reactor and then up a stack. The stack and the black building that housed the reactor (called the "black barn") were prominent features everyone noticed when arriving at X-10 during the war.

Because Wigner had changed the cooling system design for the larger reactors built at Hanford, Washington, from helium to water, the air-cooled X-10 reactor was not truly a pilot plant for Hanford's water-cooled reactors. Instead, Du Pont officials viewed the hot cells of the separations building adjacent to the X-10 reactor as a pilot plant for similar facilities to be built at Hanford, and they considered development of chemical separations processes the most daunting mission at X-10.

The need for safe plutonium separation challenged chemical engineers to design, fabricate, and test equipment for remotely transferring and evaporating liquids, dissolving and separating solids, and handling toxic gases. Instrumentation was needed for remote measurements of volumes, densities, and temperatures in a hazardous environment. Techniques to separate microscopic amounts of radioactive elements from volumes of liquid thousands of times larger had to be invented. The unknown effects of intense radiation on the solvents had to be identified and handled. Disposal of contaminated equipment and unprecedented volumes of radioactive wastes had to be addressed. These were a few of the difficulties facing Clinton Laboratories personnel as work progressed at X-10 during the autumn of 1943.

Charles Coryell of MIT, one of many brilliant chemists who served at Clinton Laboratories
during the war.
Charles Coryell of MIT, one of many brilliant chemists who served at Clinton Laboratories during the war.

The organization of Clinton Laboratories was in constant flux during the war. Scientists and technicians moved from Chicago to Oak Ridge to Hanford and Los Alamos as if they were in a revolving door. Many members of the original Oak Ridge research staff came from Chicago. The Du Pont Company brought its construction and operations personnel to Oak Ridge for training, then moved them to Hanford. Most Du Pont personnel came to X-10 from ordnance plants the company had constructed before 1943. Wartime employment at Clinton Laboratories leveled off in 1944 at 1513 scientists, technicians, and operating personnel, including 113 soldiers from the Army's Special Engineering Detachment assigned to the Manhattan Project.

Organization of the Laboratory proceeded in 1943, with Martin Whitaker as its director and Richard Doan as its associate director for research. Reporting directly to Whitaker were research manager Doan, Simeon Cantril (and later John Wirth) of the Health Division, and plant manager S. W. Pratt, who brought many Du Pont personnel to Oak Ridge. When its initial organization took shape, Clinton Laboratories had units for chemistry, health, engineering, and accounting, together with sections devoted to physics and radiation biology. (See related article, Safety Margins.)


By Halloween in 1943, when Du Pont had completed the final engineering of the Graphite Reactor, Whitaker brought Compton and Fermi from Chicago to witness its first operation. Three days later, workers began to insert thousands of uranium slugs into the reactor. The sequence involved loading a ton or two, withdrawing control rods to measure the increase in neutron flux, reinserting the rods into the pile, loading another batch of uranium, then stopping again to assess activity, each time attempting to estimate when the reactor would achieve a self-sustaining chain reaction. A second shift continued this tedious procedure into the night, with Henry Newsom and George Weil plotting the flux curve. Weil had manipulated the control rod when Fermi brought Chicago Pile 1 to criticality the previous December, and he had come from Chicago to help achieve the same result in Oak Ridge.

Main office building of Clinton Laboratories under construction in May 1943.
Main office building of Clinton Laboratories under construction in May 1943.

The day shift loaded nearly 10 tons of slugs, and the night shift set out to beat this record, working at both ends of the scaffold elevator at the reactor's face under the supervision of Kent Wyatt. In the middle of the night, Newsom and Weil, in the plotting room, recognized that one more batch of slugs would bring the reactor to the critical point, and they stopped the loading. Before dawn on November 4, Louis Slotin drove to the Guest House to awaken the two Nobel laureates, Compton and Fermi, known by the aliases Holley and Farmer in Oak Ridge. In the dark, they raced down Bethel Valley Road to witness the reactor going critical at 5:00 a.m. Scientists aware that the world's first powerful nuclear reactor had gone critical that morning were thrilled. John Gillette, a Du Pont engineer on the graveyard shift that had loaded the last 20 tons of uranium slugs, was "too pooped to care."

Arthur Rupp of the Engineering Division had been dubious of Wigner's theoretical calculations of the amount of heat that uranium would emit during fission. To test the computations, he and his colleagues calibrated the air flow through the reactor and installed temperature, humidity, and barometric instruments. They then compared the uranium fission rate with the amount of heat released. When the experimental value proved nearly the same as the theoretical prediction, Rupp's skepticism ended. "I knew then," he said, "the atomic bomb was going to work!"

As Wigner and Alvin Weinberg at Chicago had predicted during the design phase, the reactor had gone critical when about half its 1248 channels were loaded. Initially called the X-10 or Clinton Pile, it became known as the Graphite Reactor. Noted for its reliability, it worked with few operational difficulties throughout 20 years of service. Near the end of November 1943, it discharged the first uranium slugs for chemical separation. By year's end, the chemists had successfully extracted 1.54 milligrams of plutonium from the slugs and dispatched them to Chicago, by secret courier, in a container resembling a penlight. Blocking empty channels in the graphite (to concentrate the cooling air) allowed an increase in the reactor's thermal power to 1800 kilowatts in early 1944. Subsequent air-flow modification, plus the installation of larger fans for cooling, permitted its operation at more than 4000 kilowatts, nearly four times the original design capacity, with corresponding increases in plutonium production.

Constructing the concrete hot cells of the chemical separations building in November
Constructing the concrete hot cells of the chemical separations building in November 1943. In 1992, this Radiochemical Development Facility (Building 3019) was designated a Nuclear Historic Landmark by the American Nuclear Society.


In February 1944, the first plutonium shipment went from Oak Ridge to Los Alamos. By spring, the chemists had improved the bismuth phosphate separation process to the point that 90% of the plutonium in the slugs was recovered. In early 1945, when plutonium separation ceased at X-10, the Graphite Reactor and separations plant had produced a total of 326.4 grams of plutonium, a substantial contribution to nuclear research and ultimately to weapons development.

In early 1945, Robert Oppenheimer urgently asked Clinton Laboratories to supply Los Alamos with large quantities of pure radioactive lanthanum, called "RaLa," the decay product of radioactive barium-140. Clinton's chemists separated the first quantity of this isotope from the reactor's fission products in glass equipment in the chemistry laboratory. To obtain larger amounts safely, Martin Whitaker assigned Miles Leverett the job of designing, constructing, and operating a barium-140 production facility. With support from the Chemistry Division, Leverett, Charles Coryell, and Henri Levy met the schedule and Oppenheimer's requirements. "I believe," Leverett later speculated, "that this was the first production of a radioisotope on a large scale."

Remote controls for the plutonium separations process in the adjacent hot cells in 1944.
Remote controls for the plutonium separations process in the adjacent hot cells in 1944.

To assist with the design of Hanford's plutonium production reactors, many experiments were performed at the Graphite Reactor during 1944. One test involved laminated steel and masonite radiation shields designed for Hanford. The shield samples were set in an opening in the Graphite Reactor to study the interactions between the samples and radiation. Brass, neoprene, bakelite, rubber, and ordinary construction materials to be used at Hanford also were exposed to radiation in the Graphite Reactor to analyze their performance. Because the Hanford reactors were to be water cooled, tubes were installed in the Graphite Reactor to circulate water and observe its cooling and corrosive effects.

The conventional relationship between pilot plant and production plant existed between the Clinton Laboratories' hot cells and similar concrete structures built at Hanford. George Boyd, John Swartout, and other chemists from Chicago moved to Oak Ridge in October 1943, where they continued their investigations of plutonium separation processes and the properties of plutonium. The Clinton experience indicated the bismuth phosphate carrier process was not entirely suitable for the plutonium separation process, but Seaborg's other process, using lanthanum fluoride, worked well. This process was incorporated into Hanford's separation facilities. So was the experience of hundreds of personnel trained at Clinton Laboratories.

Uranium slugs encased in aluminum fell from the back of the Graphite Reactor into a canal.
Uranium slugs encased in aluminum fell from the back of the Graphite Reactor into a canal. Shielded from radiation by the water, workers pulled buckets full of uranium slugs into the nearby separations building for the extraction of plutonium. 

Physicist John Wheeler worried that unwanted isotopes capable of stopping chain reactions would be found in the irradiated uranium. Like the boron and cadmium used in reactor control rods, the isotopes would have a large neutron-capture cross section—that is, they might absorb enough neutrons to kill a nuclear chain reaction. This problem occurred at the first Hanford reactor during its trial run, a nasty surprise to Fermi and all concerned. After the chain reaction became self-sustaining, the reactor stalled. A few hours later, the reactor, for unexplained reasons, started again. Fermi and Wheeler suspected that the isotope xenon-135 was the culprit because the time required for this short-lived isotope to decay was roughly equal to the duration of the reactor's shutdown.

Urgent, around-the-clock efforts to measure the neutron-absorption cross section xenon-135 began at the Argonne and Clinton laboratories. Scientists worked 40 hours at a stretch to separate xenon-135 from its parent iodine, place samples in the Graphite Reactor, and obtain rough estimates of its ability to capture neutrons, an ability measured in "barns" (from the folk idiom "big as the broad side of a barn").

They measured xenon-135 at four million barns; that is, tiny amounts of xenon could shut down large reactors, which would start again after the xenon decayed. 

Clinton Laboratories was criticized for not detecting xenon's effects during earlier Graphite Reactor operations. A decline of reactivity resulting from xenon poisoning had occurred in the Graphite Reactor, but the reactor's conservative design had overcome the poisoning effects. The reactor did not shut down, and the staff did not notice its decline in reactivity. 

Fortunately, at Hanford the DuPont engineers had designed reactors larger than necessary. This overdesign allowed the insertion of sufficient uranium fuel to overcome xenon's poisoning effects and to continue production of the plutonium later used in the "Trinity" test in July 1945 and in the bomb that devastated Nagasaki, Japan, on August 9. 


Announcing the bombing of Hiroshima, President Harry Truman mentioned the weapons facilities built at Oak Ridge, Hanford, and Los Alamos, commenting: "The battle of the laboratories held fateful risks for us as well as the battles of the air, land, and sea, and we have now won the battle of the laboratories as we have won the other battles."

 This news came as a surprise even to some employees at Clinton Laboratories. Before he heard the president's announcement, reactor operator Willie Schuiten did not believe co-workers who told him the reactor's work was tied to a new weapon. He later commented, "The people in charge really did a good job of keeping the project a secret." 

Many Oak Ridge scientists, however, knew or surmised the purposes of the project. News of the bomb's success elated them, especially if they had relatives serving in the armed forces in the Pacific. One physicist commented that "we had helped to do a bold and difficult job, and had stopped a war in its tracks." He added, "That was enough for the moment. Second thoughts came later."

The end of World War II brought great public relief and considerable concern about the future of Oak Ridge.
The end of World War II brought great public relief and considerable concern about the future of Oak Ridge. 

A few days later came Japan's surrender and the end of World War II. Staff members drifted about Clinton Laboratories, gathering and talking, seemingly bereft of energy. "Everyone," admitted one scientist, "felt a sense of disorientation, of slackness, of loss of direction."

The war's end had come while Clinton Laboratories was in the throes of a management change. In July 1945, one month before the first atomic bomb was dropped, the University of Chicago withdrew as the contract operator, and the Army selected Monsanto Chemical Company as the new operator. This major change, combined with the fact that many scientists planned to return to the universities and their prewar research, raised a fundamental question: "What would become of the Lab?"


Winning the war left the staff of Clinton Laboratories with both a pride in their accomplishment and a sense of anxiety. Their prime task of guiding the Hanford facility in producing and separating plutonium for use in an atomic bomb had been accomplished on schedule. But with this task successfully completed, the future looked uncertain. Could the research facility be as useful and productive in peace as it had been in war? Would its scientists be content to remain in the hills of East Tennessee, or would they opt to return to more cosmopolitan settings in Chicago, New York, and California? Would the federal government be willing to invest as much money in the peaceful uses of nuclear energy as it had in weapons production? Would its scientists be content to remain in the hills of East Tennessee, or would they opt to return to more cosmopolitan settings in Chicago, New York, and California? Would the federal government be willing to invest as much money in the peaceful uses of nuclear energy as it had in weapons production? (See related article, The Silver Lining of the Calutrons.)

Although the Oak Ridge facility had shed its wartime cloak of secrecy to emerge as a heroic place, its future was still uncertain. Impressed by the bucolic atmosphere and substantial record of accomplishment, Wigner thought Clinton Laboratories did indeed have a future. In late 1944, he drew up a plan for an expanded postwar laboratory for nuclear research with perhaps 3500 personnel and an associated school of reactor technology. Furthermore, he hoped he and his theoretical group in Chicago would be transferred as a unit to Oak Ridge. When that was not done, he persuaded some of his staff in Chicago to move south, starting in May 1945 with Alvin Weinberg. Wigner followed in 1946, marking the opening of a volatile era in the Laboratory's history. Like the rest of America and the world, the Laboratory, whose energies and resources had been focused exclusively on war, would have to learn to live with peace.

Aerial view of Clinton Laboratories after the war. Just right of the center is the Graphite Reactor, and immediately to its right is the long, concrete separations building.

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