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In January, 1939 a Physics Conference took place in Washington in the United
States. A great deal of discussion concerned the possibility of producing an
atomic bomb. Some scientists argued that the technical problems involved in
producing such a bomb were too difficult to overcome, but the one thing they
were agreed upon was that if such a weapon was developed, it would give the
country that possessed it the power to blackmail the rest of the world. Several
scientists at the conference took the view that it was vitally important that all
information on atomic power should be readily available to all nations to stop this
happening.
On 2nd August, 1939, three Jewish scientists who had fled to the United States
from Europe, Albert Einstein, Leo Szilard and Eugene Wigner, wrote a joint letter
to President Franklin D. Roosevelt, about the developments that had been taking
place in nuclear physics. They warned Roosevelt that scientists in Nazi Germany
were working on the possibility of using uranium to produce nuclear weapons.
Roosevelt responded by setting up a scientific advisory committee to investigate
the matter. He also had talks with the British government about ways of
sabotaging the German efforts to produce nuclear weapons.
In May, 1940, the German Army invaded Denmark, the home of Niels Bohr, the
world's leading expert on atomic research. It was feared that he would be forced
to work for Nazi Germany. With the help of the British Secret Service he escaped
to Sweden before being moving to the United States.
In 1942 the Manhattan Engineer Project was set up in the United States under
the command of Brigadier General Leslie Groves. Scientists recruited to produce
an atom bomb included Robert Oppenheimer (USA), David Bohm (USA), Leo
Szilard (Hungary), Eugene Wigner (Hungary), Rudolf Peierls (Germany), Otto
Frisch (Germany), Niels Bohr (Denmark), Felix Bloch (Switzerland), James
Franck (Germany), James Chadwick (Britain), Emilio Segre (Italy), Enrico Fermi
(Italy), Klaus Fuchs (Germany) and Edward Teller (Hungary).
Winston Churchill and Franklin D. Roosevelt were deeply concerned about the
possibility that Germany would produce the atom bomb before the allies. At a
conference held in Quebec in August, 1943, it was decided to try and disrupt the
German nuclear programme.
In February 1943, SOE saboteurs successfully planted a bomb in the Rjukan
nitrates factory in Norway. As soon as it was rebuilt it was destroyed by 150 US
bombers in November, 1943. Two months later the Norwegian resistance
managed to sink a German boat carrying vital supplies for its nuclear
programme.
Meanwhile the scientists working on the Manhattan Project were developing
atom bombs using uranium and plutonium. The first three completed bombs were
successfully tested at Alamogordo, New Mexico on 16th July, 1945.
By the time the atom bomb was ready to be used Germany had surrendered. Leo
Szilard and James Franck drafted a petition signed by just under 70 scientists
opposed to the use of the bomb on moral grounds. However, the advice was
ignored by Harry S. Truman, the USA's new president, and he decided to use the
bomb on Japan.
On 6th August 1945, a B29 bomber dropped an atom bomb on Hiroshima. It has
been estimated that over the years around 200,000 people have died as a result
of this bomb being dropped. Japan did not surrender immediately and a second
bomb was dropped on Nagasaki three days later. On 10th August the Japanese
surrendered. The Second World War was over.
(10) Harry S. Truman, Year of Decisions (1955)
The task of creating the atomic bomb had been entrusted to a special unit of the
Army Corps of Engineers, the so-called Manhattan District, headed by Major
General Leslie R. Groves. The primary effort, however, had come from British
and American scientists, working in laboratories and offices scattered throughout
the nation.
Dr. J. Robert Oppenheimer, the distinguished physicist from the University of
California, had set up the key establishment in the whole process at Los Alamos,
New Mexico. More than any other one man, Oppenheimer is to be credited with
the achievement of the completed bomb.
My own knowledge of these developments had come about only after I became
President, when Secretary Stimson had given me the full story. He had told me
at that time that the project was nearing completion and that a bomb could be
expected within another four months. It was at his suggestion, too, that I had then
set up a committee of top men and had asked them to study with great care the
implications the new weapon might have for us.
At Potsdam, as elsewhere, the secret of the atomic bomb was kept closely
guarded. We did not extend the very small circle of Americans who knew about
it. Churchill naturally knew about the atomic bomb project from its very beginning,
because it had involved the pooling of British and American technical skill.
On July 24th I casually mentioned to Stalin that we had a new weapon of special
destructive force. The Russian Premier showed no unusual interest. All he said
was that he was glad to hear it and hoped we would make "good use of it against
the Japanese".
The final decision of where and when to use the atomic bomb was up to me. Let
there be no mistake about it. I regarded the bomb as a military weapon and
never had any doubt that it should be used.
(11) General Dwight Eisenhower, the Supreme Allied Commander, told
President Harry S. Truman that he was opposed to the dropping of the
atom bomb on Japan.
I voiced to him my grave misgivings, first on the basis of my belief that Japan
was already defeated and that dropping the bomb was completely unnecessary,
and secondly because I thought that our country should avoid shocking world
opinion by the use of a weapon whose employment was, I thought, no longer
mandatory as a measure to save American lives. It was my belief that Japan
was, at that very moment, seeking some way to surrender with a minimum loss
of "f
The Manhattan Project
In 1939, the Nazis were rumored to be developing
an atomic bomb. The United States initiated its own
program under the Army Corps of Engineers in
June 1942. America needed to build an atomic
weapon before Germany or Japan did.
General Leslie R. Groves, Deputy Chief of
Construction of the U.S. Army Corps of Engineers,
was appointed to direct this top-secret project.
General Leslie R. Groves
(1896-1970)
General Leslie R. Groves directed the Manhattan Project. More
University of Chicago
Meanwhile, experiments in a small laboratory beneath the University of
Chicago's abandoned Stagg Field were expanding understanding of
atomic theory. The first controlled nuclear reaction occurred under
Stagg Field. More
Copyright © 2003,
National Atomic Museum.
Oak Ridge, Tennessee
Scientists now had to create the fuel for an atomic bomb. The Oak Ridge facility separated
the nuclear fuel U-235 from U-238, natural uranium. More
Hanford, Washington
The Hanford Engineer Works produced plutonium. More
J. Robert Oppenheimer
(1904-1967)
Theoretical physicist Oppenheimer, who would direct Los Alamos research, identified top scientists
and engineers from universities nationwide. More
Los Alamos, New Mexico
At Los Alamos, an international team of scientists and engineers labored
around the clock to create the first atomic weapons. More
Los Alamos, New Mexico
By March 1943, Los Alamos had became an intellectual boomtown. More
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Uranium Fission
1938
Otto Hahan and Fritz Strassmann's discovery of fission steered Germany toward developing an atomic weapon. This
motivated the U.S. to launch the Manhattan Project.
The Race for the Atomic Bomb Begins
1939-1941
World War II started September 1, 1939, when Germany attacked Poland. By 1941, the Germans were leading the
race for the atomic bomb. They had a heavy-water plant, high-grade uranium compounds, a nearly complete cyclotron,
capable scientists and engineers, and the greatest chemical engineering industry in the world.
The Research Effort Struggles
1941-1945
Factors including internal struggles, a major scientific error, and the devastation of total war compromised any
successful research toward a German atom bomb. Unlike the American program, the Germans never had a clear
mission under continuously unified leadership.
The First Controlled Nuclear Reaction
1942
At the University of Chicago reactor, Enrico Fermi oversaw the first controlled energy release from the nucleus of the
atom.
U-235 Output Begins
1945
After intense effort, the Y-12 plant in Oak Ridge, Tenn., began to produce bomb-grade U-235, which was shipped to
Los Alamos, N.M. U-235 was used in the Little Boy bomb and plutonium was used in the Fat Man bomb produced at
Los Alamos.
ace".
Oak Ridge, Tennessee
Scientists needed to find fuel, for the reactors, which meant using uranium (U-235) or plutonium (Pu-238), the only suitable substances
know by 1942. Project leaders did not know how quickly or how much of each they could produce, so they decided to produce both at
the same time.
Primitive living arrangements found in rural East Tennessee at
Copyright © 2003,
National Atomic Museum.
the time.
Three methods existed for extracting U-235: an electromagnetic process, gaseous diffusion and thermal diffusion. Oak Ridge crews built
a plant for each method. The electromagnetic process at the facility, called Y-12, was the most promising.
The process of extracting U-235 from natural uranium started at the Clinton Engineer Works, 20 miles west of Knoxville, TN. Work began
on the plant in 1942. In 1943, the facility name was changed to Oak Ridge. This Appalachian site spanned 59,000 acres of wilderness
and farmland.
The Clinch River provided hydroelectric power through the Tennessee Valley Authority (TVA). To build on of the largest U.S. industrial
complexes, more than 1,000 rural families were relocated from their farms.
By the time President Roosevelt authorized the Manhattan Project on
December 28, 1942, work on the east Tennessee site where the first production
facilities were to be built was already underway.
On Saturday, September 19, Groves had approved the acquisition of 59,000
acres of land along the Clinch River, 20 miles west of Knoxville, Tennessee.
Also approved was the removal of relatively few families on the marginal
farmland and extensive site preparation to provide the transportation,
communications, and utility needs of the town and production plants that would
occupy the previously undeveloped area. At first, this location was known as
"Site X" and later changed to the Clinton Engineer Works, named after the
nearest town. After the war, the name was again changed officially to Oak
Ridge.
Original plans called for the military reservation to house approximately
13,000 people in prefabricated housing, trailers, and wood dormitories. By the
time the Manhattan Engineer District headquarters were moved from
Washington DC to Tennessee in the summer of 1943 (Groves kept the
Manhattan project's office in Washington and placed Col. Kenneth D. Nichols
in command at Tennessee), estimates for the town of Oak Ridge had been
revised upward to 45,000 people. (Note: The name Oak Ridge did not come
into usage until after World War II but will be used here to avoid confusion).
By the end of the war, Oak Ridge was the fifth largest city in Tennessee and
was consuming 1/7 of all the electrical power being produced in the United
States. While the Army and its contractors tried desperately to keep up with
the rapid influx of workers and their families, services always lagged behind
demand.
The three production facility sites were located in valleys away from the
town. This provided security and containment in case of accidental
explosions. The Y-12 area, home of the electromagnetic plant, was closest to
Oak Ridge, being one ridge away to the south. Farther to the south and west
lay both the X-10 area, which contained the experimental plutonium pile and
separation facilities, and K-25, site of the gaseous diffusion plant and later the
S-50 thermal diffusion plant
General History of the Oak Ridge Facility
The mission of Oak Ridge was to produce enriched uranium for the
first atomic bombs. The site was selected because the Clinch River
provided ample supplies of water, nearby Knoxville was a good source
of labor, and the TVA could supply the huge amounts of electricity
needed. Gen. Groves ordered acquisition of the 56,200 acre site on 19
September 1942 in a tightly controlled security area spanning three
Appalachian valleys.
At that time, two methods of uranium enrichment were under
consideration: gaseous diffusion and electromagnetic separation. Since
no one could say which was more likely to succeed, both were tried,
an enormous undertaking under wartime conditions. The Y-12 plant
utilized calutrons for the electromagnetic separation method, and the
K-25 plant used gaseous diffusion. A third facility known as X-10
housed a graphite plutonium production reactor and the facilities
needed to extract the plutonium from the irradiated fuel.
The Oak Ridge X-10 Site
The original portion of the Oak Ridge facility, built in 1942 as the
Clinton Engineer Works, is known as X-10, comprising 2,900 acres in
Melton and Bethel Valleys, 10 miles southwest of the City of Oak
Ridge.
The Manhattan Project plan was to create two atomic weapons--one
fueled by plutonium, the other by enriched uranium. Hanford,
Washington, was selected as the site for plutonium production, but
before a facility could be built there, the X-10 pilot plant was
necessary to prove the feasibility of scaling up from laboratory
experiments. The Graphite Reactor was built for this purpose in only
11 months, designed to show that plutonium could be extracted from
irradiated uranium slugs.
Workers began loading uranium into the reactor during the afternoon
of 3 November 1943 and at 5AM the next morning, Enrico Fermi saw
the reactor go critical. Four months later, Oak Ridge chemists
produced the world's first few grams of plutonium.
The Oak Ridge Y-12 Plant
Construction on Y-12 began in February 1943 to implement the
electromagnetic separation method, with first production in November
of the same year (although construction continued through 1945).
Tennessee Eastman took over operation of Y-12 in June 1943.
At Y-12, nine main processing buildings and over two hundred support
buildings were constructed to house the process. The primary process
used calutrons--large arrangements of electro-magnets which
separated weapons grade U-235 out of naturally more abundant U238. Because of the war time shortage of copper, 14,700 tons of silver
from the U.S. Treasury were used in the calutron windings and
associated electrical conductors. Y-12 employed 22,000 workers in the
peak war years period, but the gaseous diffusion process at the K-25
Plant proved to be more effective for uranium enrichment and Y-12
was mothballed at the end of the war. Later the massive Y-12 facility
became a nuclear weapons production facility and large scale lithium
separation plant, a material critical to the hydrogen bomb.
The Oak Ridge K-25 Site
Carbide and Carbon Chemicals Corp. (subsidiary of Union Carbide) K-25 Plant 1945.
The K-25 Site occupies a 1,700-acre area adjacent to the Clinch River,
approximately 13 miles west of Oak Ridge. The K-25 Plant was
authorized in late 1942, and was the last of the big Oak Ridge sites to
become operational. It was the world's first gaseous diffusion plant,
the method of uranium enrichment with the best theoretical basis,
championed by the British, but which had never been tried in practice.
K-25 was huge, even by Oak Ridge standards, with fifty four-story
buildings totaling 2,000,000 square feet, in a U-shape measuring a
2,600 feet long by 1,000 feet wide. Covering some 44 acres, the K-25
building was the world's largest roofed structure when it was
completed in March 1945. Housing and service facilities were built for
the population that eventually reached 15,000.
Inside K-25, a series of over
1,000 huge cells were linked in a
cascade through which uranium
hexafluoride gas traveled, with
small fractions of the U-235
isotope separated by a barrier
material with microscopic pores.
Production problems at K-25 led
to an August 1943 decision that
K-25 would not fully enrich uranium but would produce partially
enriched feeder material for Y-12. A key production problem was
developing a suitable diffusion barrier, material with millions of tiny
holes that would also withstand the extremely corrosive gas involved.
That problem was not solved until 1944 enabling production in 1945.
Both the Y-12 and K-25 plants failed to meet expectations. Early in
1944 neither plant was producing anything usable, but Gen. Groves
and his team pushed forward nonetheless. This was an enormous
gamble with fantastic sums of money and scarce resources being
poured into the Oak Ridge project. Gen. Groves decided to invest in a
third technique, thermal diffusion, developed by Philip Abelson for the
Navy. A contractor, H.K. Ferguson Company of Cleveland, was given
just 90 days to construct the S-50 themal diffusion facility, involving
2,142 columns, each over 40 feet tall.
As of April 1945, none of the processes worked well, but Oppenheimer
devised a desperate solution. He ordered that Oak Ridge's three
enrichment processes be run serially. The thermal diffusion process
achieved less than two percent enrichment but this slightly enriched
material greatly increased the efficiency of the gaseous diffusion
process. When this product, enriched to about 23 percent U-235, was
fed into the calutrons of the electromagnetic separation process, the
result was 84 to 89 percent enrichment, good enough for weapons.
Delivery to Los Alamos
By the spring of 1945, Oak Ridge had shipped approximately 132
pounds of enriched uranium to Los Alamos where the bomb was
designed and would be assembled. The Oak Ridge uranium was used
in "Little Boy", the bomb dropped on Hiroshima on 6 August 1945.
With few exceptions, fission weapons since the end of World War II
have used plutonium, not uranium. The Oak Ridge plants were either
shut down or converted to other nuclear weapons production
processes.
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