(Oak Ridge: Clinton, 1942-1943)
The Uranium Path to the
Although the Lewis Report had placed gaseous
diffusion ahead of the electromagnetic
approach, many were still betting in early 1943 that Ernest Lawrence
(right) and his "calutron" would eventually predominate.
Lawrence and his laboratory of mechanics at the University of
California, Berkeley, continued to experiment with the giant
magnet, trying to reach a consensus on which shims, sources, and
collectors to incorporate into the Y-12 Electromagnetic Plant
that was to be built at Oak
Ridge. Research on magnet size and placement and beam
resolution led Lawrence and his group in fall 1942 to propose an arrangement
of huge electromagnetic coils connected by a bus bar in an oval racetrack
configuration, as seen from above. Forty-eight gaps in the racetrack
between the coils would each contain two vacuum tanks. With two racetracks
per building, ten buildings would be necessary to provide the estimated
2,000 sources and collectors needed to separate 100 grams of uranium-235
daily. The Berkeley researchers hoped that improvements in calutron
design, or placing multiple sources and collectors in each tank, might
increase efficiency and reduce the number of tanks and buildings required,
but experimental results were inconclusive even as Stone & Webster of
Boston, the Y-12 contractor at Oak Ridge, prepared to break
At a meeting of Leslie Groves
(right), Lawrence, and John R. Lotz of Stone & Webster in Berkeley late
in December 1942, Y-12 plans took shape. It was agreed that Stone
& Webster would take over design and construction of a 500-tank
facility, while Lawrence's laboratory would play a supporting role by
supplying experimental data. By the time another summit conference on
Y-12 took place in Berkeley on January 13 and 14, Groves had persuaded the
Tennessee Eastman Corporation to sign on as plant operator and arranged for
various parts of the electromagnetic equipment to be manufactured by the
Westinghouse Electric and Manufacturing Company, the Allis-Chalmers
Manufacturing Company, and the Chapman Valve Manufacturing Company.
General Electric agreed to provide electrical equipment.
On January 14, after a
day of presentations and a demonstration of the experimental tanks, Groves
stunned the Y-12 contractors by insisting that the first racetrack of
ninety-six tanks be in operation by July 1 and that 500 tanks be delivered
by year's end. Given that each of the five planned racetracks was 122
feet long, 77 feet wide and 15 feet high; that the completed plant was to
consist of three 450-feet long buildings, each housing two racetracks
placed end-to-end on the second floor; that tank design was in flux; and
that separate chemistry buildings also would be needed for preparing charge
materials and separating uranium recovered from the tanks, Groves's demands
were little less than shocking. Nonetheless, Groves maintained that
his schedule could be met.
For the next two months Lawrence, the contractors, and the Army
negotiated over the final design. While all involved could see
possible improvements, there simply was not enough time to incorporate
every suggested modification. Y-12 design was finalized at a March 17
meeting in Boston, with one major modification -- the inclusion of a second
stage of the electromagnetic process. The purpose of this second stage
was to take the enriched uranium-235 derived from several runs of the first
stage and use it as the sole feed material for a second stage of racetracks
containing tanks approximately half the size of those in the first.
Groves approved this arrangement and work began on both the Alpha
(first-stage) and Beta (second-stage) tracks.
Sources and notes for this page.
The text for this page was adapted from,
and portions were taken directly from the Office of History and Heritage
Resources publication: F.
G. Gosling, The Manhattan Project: Making the Atomic Bomb
(DOE/MA-0001; Washington: History Division, Department of Energy, January
1999), 20-22. See also the History Office publication: Richard G.
Hewlett and Oscar E. Anderson, Jr., The New World, 1939-1946: Volume
I, A History of the United States Atomic Energy Commission
(Washington: U.S. Atomic Energy Commission, 1972), 141-52. The
photograph of Ernest
Lawrence slumping in his chair from fatigue is courtesy the Lawrence Berkeley National Laboratory.
The diagram illustrating the electromagnetic method is reproduced
from the Department of Energy report Linking
Legacies: Connecting the Cold War Nuclear Weapons Production Processes to
their Environmental Consequences (Washington: Center for Environmental
Management Information, Department of Energy, January 1997), 138.
The photograph of Leslie
Groves at his desk is reprinted in the inside front cover of
Vincent C. Jones, Manhattan: The Army and the Atomic Bomb, United
States Army in World War II (Washington: Center of Military History, United
States Army, 1988). The photograph of the Y-12 calutron is courtesy
Oak Ridge National Laboratory (via the Lawrence Berkeley National Laboratory). The
photograph of the Y-12 racetrack construction is courtesy the Department
Home | History
Office | OpenNet | DOE | Privacy and Security Notices
About this Site | How to Navigate this Site | Note on Sources |
Site Map | Contact Us