Manhattan Project
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The Manhattan Project was a research and development program undertaken during
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
to produce the first
nuclear weapon A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission or atomic bomb) or a combination of fission and fusion reactions (thermonuclear weapon), producing a nuclear exp ...
s. It was led by the United States in collaboration with the United Kingdom and Canada. From 1942 to 1946, the project was directed by Major General
Leslie Groves Leslie Richard Groves Jr. (17 August 1896 – 13 July 1970) was a United States Army Corps of Engineers officer who oversaw the construction of the Pentagon and directed the Manhattan Project, a Classified information#Top_Secret_(TS), top sec ...
of the
U.S. Army Corps of Engineers The United States Army Corps of Engineers (USACE) is the military engineering branch of the United States Army. A direct reporting unit (DRU), it has three primary mission areas: Engineer Regiment, military construction, and civil wor ...
. Nuclear physicist
J. Robert Oppenheimer J. Robert Oppenheimer (born Julius Robert Oppenheimer ; April 22, 1904 – February 18, 1967) was an American theoretical physics, theoretical physicist who served as the director of the Manhattan Project's Los Alamos Laboratory during World ...
was the director of the
Los Alamos Laboratory The Los Alamos Laboratory, also known as Project Y, was a secret scientific laboratory established by the Manhattan Project and overseen by the University of California during World War II. It was operated in partnership with the United State ...
that designed the bombs. The Army program was designated the Manhattan District, as its first headquarters were in
Manhattan Manhattan ( ) is the most densely populated and geographically smallest of the Boroughs of New York City, five boroughs of New York City. Coextensive with New York County, Manhattan is the County statistics of the United States#Smallest, larg ...
; the name gradually superseded the official codename, Development of Substitute Materials, for the entire project. The project absorbed its earlier British counterpart,
Tube Alloys Tube Alloys was the research and development programme authorised by the United Kingdom, with participation from Canada, to develop nuclear weapons during the Second World War. Starting before the Manhattan Project in the United States, the Bri ...
, and subsumed the program from the American civilian
Office of Scientific Research and Development The Office of Scientific Research and Development (OSRD) was an agency of the United States federal government created to coordinate scientific research for military purposes during World War II. Arrangements were made for its creation during May ...
. The Manhattan Project employed nearly 130,000 people at its peak and cost nearly US$2 billion (equivalent to about $ billion in ). The project pursued both
highly enriched uranium Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium-238 (238 ...
and
plutonium Plutonium is a chemical element; it has symbol Pu and atomic number 94. It is a silvery-gray actinide metal that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four ...
as fuel for nuclear weapons. Over 80 percent of project cost was for building and operating the
fissile material In nuclear engineering, fissile material is material that can undergo nuclear fission when struck by a neutron of low energy. A self-sustaining thermal chain reaction can only be achieved with fissile material. The predominant neutron energy i ...
production plants. Enriched uranium was produced at Clinton Engineer Works in
Tennessee Tennessee (, ), officially the State of Tennessee, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Kentucky to the north, Virginia to the northeast, North Carolina t ...
. Plutonium was produced in the world's first industrial-scale
nuclear reactor A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons ...
s at the Hanford Engineer Works in Washington. Each of these sites was supported by dozens of other facilities across the US, the UK, and Canada. Initially, it was assumed that both fuels could be used in a relatively simple atomic bomb design known as the gun-type design. When it was discovered that this design was incompatible for use with plutonium, an intense development program led to the invention of the implosion design. The work on weapons design was performed at the Los Alamos Laboratory in
New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...
, and resulted in two weapons designs that were used during the war:
Little Boy Little Boy was a type of atomic bomb created by the Manhattan Project during World War II. The name is also often used to describe the specific bomb (L-11) used in the bombing of the Japanese city of Hiroshima by the Boeing B-29 Superfortress ...
(enriched uranium gun-type) and
Fat Man "Fat Man" (also known as Mark III) was the design of the nuclear weapon the United States used for seven of the first eight nuclear weapons ever detonated in history. It is also the most powerful design to ever be used in warfare. A Fat Man ...
(plutonium implosion). The first nuclear device ever detonated was an implosion-type bomb during the
Trinity test Trinity was the first detonation of a nuclear weapon, conducted by the United States Army at 5:29 a.m. MWT (11:29:21 GMT) on July 16, 1945, as part of the Manhattan Project. The test was of an implosion-design plutonium bomb, or "gadg ...
, conducted at
White Sands Proving Ground White Sands Missile Range (WSMR) is a United States Army military testing area and firing range located in the US state of New Mexico. The range was originally established in 1941 as the Alamogordo Bombing and Gunnery Range, where the Trinity ( ...
in New Mexico on 16 July 1945. The project also was responsible for developing the specific means of delivering the weapons onto military targets, and were responsible for the use of the Little Boy and Fat Man bombs in the
atomic bombings of Hiroshima and Nagasaki On 6 and 9 August 1945, the United States detonated two atomic bombs over the Japanese cities of Hiroshima and Nagasaki, respectively, during World War II. The aerial bombings killed between 150,000 and 246,000 people, most of whom were civili ...
in August 1945. The project was also charged with gathering intelligence on the German nuclear weapon project. Through
Operation Alsos The Alsos Mission was an organized effort by a team of British and United States military, scientific, and intelligence personnel to discover enemy scientific developments during World War II. Its chief focus was to investigate the progress that ...
, Manhattan Project personnel served in Europe, sometimes behind enemy lines, where they gathered nuclear materials and documents and rounded up German scientists. Despite the Manhattan Project's own emphasis on security, Soviet
atomic spies Atomic spies or atom spies were people in the United States, the United Kingdom, and Canada who are known to have illicitly given information about nuclear weapons production or design to the Soviet Union during World War II and the early Cold W ...
penetrated the program. In the immediate postwar years, the Manhattan Project conducted weapons testing at
Bikini Atoll Bikini Atoll ( or ; Marshallese language, Marshallese: , , ), known as Eschscholtz Atoll between the 19th century and 1946, is a coral reef in the Marshall Islands consisting of 23 islands surrounding a central lagoon. The atoll is at the no ...
as part of
Operation Crossroads Operation Crossroads was a pair of nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. They were the first nuclear weapon tests since Trinity on July 16, 1945, and the first detonations of nuclear devices sinc ...
, developed new weapons, promoted the development of the network of national laboratories, supported medical research into
radiology Radiology ( ) is the medical specialty that uses medical imaging to diagnose diseases and guide treatment within the bodies of humans and other animals. It began with radiography (which is why its name has a root referring to radiation), but tod ...
, and laid the foundations for the nuclear navy. It maintained control over American atomic weapons research and production until the formation of the
United States Atomic Energy Commission The United States Atomic Energy Commission (AEC) was an agency of the United States government established after World War II by the U.S. Congress to foster and control the peacetime development of atomic science and technology. President Harry ...
(AEC) in January 1947.


Origins

The
discovery of nuclear fission Nuclear fission was discovered in December 1938 by chemists Otto Hahn and Fritz Strassmann and physicists Lise Meitner and Otto Robert Frisch. Fission is a nuclear reaction or radioactive decay process in which the atomic nucleus, nucleus of a ...
by
Otto Hahn Otto Hahn (; 8 March 1879 – 28 July 1968) was a German chemist who was a pioneer in the field of radiochemistry. He is referred to as the father of nuclear chemistry and discoverer of nuclear fission, the science behind nuclear reactors and ...
and Fritz Strassmann in 1938, and its theoretical explanation by
Lise Meitner Elise Lise Meitner ( ; ; 7 November 1878 – 27 October 1968) was an Austrian-Swedish nuclear physicist who was instrumental in the discovery of nuclear fission. After completing her doctoral research in 1906, Meitner became the second woman ...
and
Otto Frisch Otto Robert Frisch (1 October 1904 – 22 September 1979) was an Austrian-born British physicist who worked on nuclear physics. With Otto Stern and Immanuel Estermann, he first measured the magnetic moment of the proton. With his aunt, Lise M ...
, made an
atomic bomb A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission or atomic bomb) or a combination of fission and fusion reactions (thermonuclear weapon), producing a nuclear expl ...
theoretically possible. There were fears that a German atomic bomb project would develop one first, especially among scientists who were refugees from
Nazi Germany Nazi Germany, officially known as the German Reich and later the Greater German Reich, was the German Reich, German state between 1933 and 1945, when Adolf Hitler and the Nazi Party controlled the country, transforming it into a Totalit ...
and other
fascist Fascism ( ) is a far-right, authoritarian, and ultranationalist political ideology and movement. It is characterized by a dictatorial leader, centralized autocracy, militarism, forcible suppression of opposition, belief in a natural soci ...
countries. In August 1939, Hungarian-born physicists
Leo Szilard Leo Szilard (; ; born Leó Spitz; February 11, 1898 – May 30, 1964) was a Hungarian-born physicist, biologist and inventor who made numerous important discoveries in nuclear physics and the biological sciences. He conceived the nuclear ...
and
Eugene Wigner Eugene Paul Wigner (, ; November 17, 1902 – January 1, 1995) was a Hungarian-American theoretical physicist who also contributed to mathematical physics. He received the Nobel Prize in Physics in 1963 "for his contributions to the theory of th ...
drafted the Einstein–Szilard letter, which warned of the potential development of "extremely powerful bombs of a new type". It urged the United States to acquire stockpiles of
uranium ore Uranium ore deposits are economically recoverable concentrations of uranium within Earth's crust. Uranium is one of the most common Chemical element, elements in Earth's crust, being 40 times more common than silver and 500 times more common than ...
and accelerate the research of
Enrico Fermi Enrico Fermi (; 29 September 1901 – 28 November 1954) was an Italian and naturalized American physicist, renowned for being the creator of the world's first artificial nuclear reactor, the Chicago Pile-1, and a member of the Manhattan Project ...
and others into
nuclear chain reaction In nuclear physics, a nuclear chain reaction occurs when one single nuclear reaction causes an average of one or more subsequent nuclear reactions, thus leading to the possibility of a self-propagating series or "positive feedback loop" of thes ...
s. They had it signed by
Albert Einstein Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence f ...
and delivered to President
Franklin D. Roosevelt Franklin Delano Roosevelt (January 30, 1882April 12, 1945), also known as FDR, was the 32nd president of the United States, serving from 1933 until his death in 1945. He is the longest-serving U.S. president, and the only one to have served ...
. Roosevelt called on Lyman Briggs of the
National Bureau of Standards The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical sc ...
to head an Advisory Committee on Uranium; Briggs met with Szilard, Wigner and
Edward Teller Edward Teller (; January 15, 1908 – September 9, 2003) was a Hungarian and American Theoretical physics, theoretical physicist and chemical engineer who is known colloquially as "the father of the hydrogen bomb" and one of the creators of ...
in October 1939. The committee reported back to Roosevelt in November that uranium "would provide a possible source of bombs with a destructiveness vastly greater than anything now known." In February 1940, the U.S. Navy awarded
Columbia University Columbia University in the City of New York, commonly referred to as Columbia University, is a Private university, private Ivy League research university in New York City. Established in 1754 as King's College on the grounds of Trinity Churc ...
$6,000, most of which Fermi and Szilard spent on
graphite Graphite () is a Crystallinity, crystalline allotrope (form) of the element carbon. It consists of many stacked Layered materials, layers of graphene, typically in excess of hundreds of layers. Graphite occurs naturally and is the most stable ...
. A team of Columbia professors including Fermi, Szilard, Eugene T. Booth and John Dunning created the first nuclear fission reaction in the Americas, verifying the work of Hahn and Strassmann. The same team subsequently built a series of prototype
nuclear reactor A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons ...
s (or "piles" as Fermi called them) in Pupin Hall at Columbia but were not yet able to achieve a chain reaction. The Advisory Committee on Uranium became the
National Defense Research Committee The National Defense Research Committee (NDRC) was an organization created "to coordinate, supervise, and conduct scientific research on the problems underlying the development, production, and use of mechanisms and devices of warfare" in the U ...
(NDRC) on Uranium when that organization was formed on 27 June 1940. On 28 June 1941, Roosevelt signed Executive Order 8807, which created the
Office of Scientific Research and Development The Office of Scientific Research and Development (OSRD) was an agency of the United States federal government created to coordinate scientific research for military purposes during World War II. Arrangements were made for its creation during May ...
(OSRD), under director
Vannevar Bush Vannevar Bush ( ; March 11, 1890 – June 28, 1974) was an American engineer, inventor and science administrator, who during World War II, World War II headed the U.S. Office of Scientific Research and Development (OSRD), through which almo ...
. The office was empowered to engage in research and large engineering projects. The NDRC Committee on Uranium became the S-1 Section of the OSRD; the word "uranium" was dropped for security reasons. In July 1941, Briggs proposed spending $167,000 on researching uranium, particularly the
uranium-235 Uranium-235 ( or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exists in nat ...
isotope, and
plutonium Plutonium is a chemical element; it has symbol Pu and atomic number 94. It is a silvery-gray actinide metal that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four ...
, which had been isolated for the first time at the
University of California The University of California (UC) is a public university, public Land-grant university, land-grant research university, research university system in the U.S. state of California. Headquartered in Oakland, California, Oakland, the system is co ...
in February 1941. In Britain, Frisch and
Rudolf Peierls Sir Rudolf Ernst Peierls, (; ; 5 June 1907 – 19 September 1995) was a German-born British physicist who played a major role in Tube Alloys, Britain's nuclear weapon programme, as well as the subsequent Manhattan Project, the combined Allied ...
at the
University of Birmingham The University of Birmingham (informally Birmingham University) is a Public university, public research university in Birmingham, England. It received its royal charter in 1900 as a successor to Queen's College, Birmingham (founded in 1825 as ...
had made a breakthrough investigating the
critical mass In nuclear engineering, critical mass is the minimum mass of the fissile material needed for a sustained nuclear chain reaction in a particular setup. The critical mass of a fissionable material depends upon its nuclear properties (specific ...
of uranium-235 in June 1939. Their calculations indicated that it was within an
order of magnitude In a ratio scale based on powers of ten, the order of magnitude is a measure of the nearness of two figures. Two numbers are "within an order of magnitude" of each other if their ratio is between 1/10 and 10. In other words, the two numbers are ...
of , small enough to be carried by contemporary bombers.. Their March 1940 Frisch–Peierls memorandum initiated the British atomic bomb project and its MAUD Committee, which unanimously recommended pursuing the development of an atomic bomb. In July 1940, Britain had offered to give the United States access to its research, and the
Tizard Mission The Tizard Mission, officially the British Technical and Scientific Mission, was a delegation from the United Kingdom that visited the United States during World War II to share secret research and development (R&D) work that had military applicat ...
's
John Cockcroft Sir John Douglas Cockcroft (27 May 1897 – 18 September 1967) was an English nuclear physicist who shared the 1951 Nobel Prize in Physics with Ernest Walton for their splitting of the atomic nucleus, which was instrumental in the developmen ...
briefed American scientists on British developments. He discovered that the American project was smaller than the British, and not as advanced. As part of the scientific exchange, the MAUD Committee's findings were conveyed to the United States. One of its members, the Australian physicist
Mark Oliphant Sir Marcus Laurence Elwin Oliphant, (8 October 1901 – 14 July 2000) was an Australian physicist and humanitarian who played an important role in the first experimental demonstration of nuclear fusion and in the development of nuclear weapon ...
, flew to the US in late August 1941 and discovered that data provided by the MAUD Committee had not reached key American physicists. Oliphant set out to find out why the committee's findings were apparently being ignored. He met with the Uranium Committee and visited
Berkeley, California Berkeley ( ) is a city on the eastern shore of San Francisco Bay in northern Alameda County, California, United States. It is named after the 18th-century Anglo-Irish bishop and philosopher George Berkeley. It borders the cities of Oakland, Cali ...
, where he spoke persuasively to Ernest O. Lawrence. Lawrence was sufficiently impressed to commence his own research into uranium. He in turn spoke to
James B. Conant James Bryant Conant (March 26, 1893 – February 11, 1978) was an American chemist, a transformative President of Harvard University, and the first United States Ambassador to West Germany, U.S. Ambassador to West Germany. Conant obtained a ...
, Arthur H. Compton and George B. Pegram. Oliphant's mission was therefore a success; key American physicists were now aware of the potential power of an atomic bomb. On 9 October 1941, President Roosevelt approved the atomic program after he convened a meeting with Vannevar Bush and Vice President
Henry A. Wallace Henry Agard Wallace (October 7, 1888 – November 18, 1965) was the 33rd vice president of the United States, serving from 1941 to 1945, under President Franklin D. Roosevelt. He served as the 11th U.S. secretary of agriculture and the 10th U.S ...
. He created a Top Policy Group consisting of himself—although he never attended a meeting—Wallace, Bush, Conant,
Secretary of War The secretary of war was a member of the U.S. president's Cabinet, beginning with George Washington's administration. A similar position, called either "Secretary at War" or "Secretary of War", had been appointed to serve the Congress of the ...
Henry L. Stimson, and the Chief of Staff of the Army,
General A general officer is an Officer (armed forces), officer of high rank in the army, armies, and in some nations' air force, air and space forces, marines or naval infantry. In some usages, the term "general officer" refers to a rank above colone ...
George C. Marshall. Roosevelt chose the Army to run the project rather than the Navy, because the Army had more experience with managing large-scale construction. He agreed to coordinate the effort with the British and on 11 October sent a message to Prime Minister
Winston Churchill Sir Winston Leonard Spencer Churchill (30 November 1874 – 24 January 1965) was a British statesman, military officer, and writer who was Prime Minister of the United Kingdom from 1940 to 1945 (Winston Churchill in the Second World War, ...
, suggesting that they correspond on atomic matters..


Feasibility


Proposals

The S-1 Committee meeting on 18 December 1941 was "pervaded by an atmosphere of enthusiasm and urgency" in the wake of the
attack on Pearl Harbor The attack on Pearl HarborAlso known as the Battle of Pearl Harbor was a surprise military strike by the Empire of Japan on the United States Pacific Fleet at Naval Station Pearl Harbor, its naval base at Pearl Harbor on Oahu, Territory of ...
and the
United States declaration of war on Japan On December 8, 1941, at 12:30 PM ET, the United States Congress declared war () on the Empire of Japan in response to its surprise attack on Pearl Harbor and subsequent declaration of war the prior day. The Joint Resolution Declaring that a st ...
and on Germany. Work was proceeding on three techniques for
isotope separation Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes. The use of the nuclides produced is varied. The largest variety is used in research (e.g. in chemistry where atoms of "marker" n ...
: Lawrence and his team at the
University of California The University of California (UC) is a public university, public Land-grant university, land-grant research university, research university system in the U.S. state of California. Headquartered in Oakland, California, Oakland, the system is co ...
investigated electromagnetic separation, Eger Murphree and Jesse Wakefield Beams's team looked into
gaseous diffusion Gaseous diffusion is a technology that was used to produce enriched uranium by forcing gaseous uranium hexafluoride (UF6) through microporous membranes. This produces a slight separation (enrichment factor 1.0043) between the molecules containi ...
at
Columbia University Columbia University in the City of New York, commonly referred to as Columbia University, is a Private university, private Ivy League research university in New York City. Established in 1754 as King's College on the grounds of Trinity Churc ...
, and
Philip Abelson Philip Hauge Abelson (April 27, 1913 – August 1, 2004) was an American physicist, scientific editor and science writer. Trained as a nuclear physicist, he co-discovered the element neptunium, worked on isotope separation in the Manhattan ...
directed research into thermal diffusion at the
Carnegie Institution of Washington The Carnegie Institution for Science, also known as Carnegie Science and the Carnegie Institution of Washington, is an organization established to fund and perform scientific research in the United States. This institution is headquartered in W ...
and later the
Naval Research Laboratory The United States Naval Research Laboratory (NRL) is the corporate research laboratory for the United States Navy and the United States Marine Corps. Located in Washington, DC, it was founded in 1923 and conducts basic scientific research, appl ...
. Murphree also headed an unsuccessful separation project using
gas centrifuge A gas centrifuge is a device that performs isotope separation of gases. A centrifuge relies on the principles of centrifugal force accelerating molecules so that particles of different masses are physically separated in a gradient along the radiu ...
s. Meanwhile, there were two lines of investigation into
nuclear reactor technology A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction. They are used for commercial electricity, marine propulsion, weapons production and research. Fissile nuclei (primarily uranium-235 or plutonium- ...
:
Harold Urey Harold Clayton Urey ( ; April 29, 1893 – January 5, 1981) was an American physical chemist whose pioneering work on isotopes earned him the Nobel Prize in Chemistry in 1934 for the discovery of deuterium. He played a significant role in the ...
researched
heavy water Heavy water (deuterium oxide, , ) is a form of water (molecule), water in which hydrogen atoms are all deuterium ( or D, also known as ''heavy hydrogen'') rather than the common hydrogen-1 isotope (, also called ''protium'') that makes up most o ...
at Columbia, while Arthur Compton organized the Metallurgical Laboratory in early 1942 to study plutonium and reactors using
graphite Graphite () is a Crystallinity, crystalline allotrope (form) of the element carbon. It consists of many stacked Layered materials, layers of graphene, typically in excess of hundreds of layers. Graphite occurs naturally and is the most stable ...
as a
neutron moderator In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, ideally without capturing any, leaving them as thermal neutrons with only minimal (thermal) kinetic energy. These thermal neutrons are immensely ...
. The S-1 Committee recommended pursuing all five technologies. This was approved by Bush, Conant, and Brigadier General Wilhelm D. Styer, who had been designated the Army's representative on nuclear matters. Bush and Conant then took the recommendation to the Top Policy Group with a budget proposal for $54 million for construction by the
United States Army Corps of Engineers The United States Army Corps of Engineers (USACE) is the military engineering branch of the United States Army. A direct reporting unit (DRU), it has three primary mission areas: Engineer Regiment, military construction, and civil wo ...
, $31 million for research and development by OSRD and $5 million for contingencies in fiscal year 1943. They sent it on 17 June 1942, to the President, who approved it by writing "OK FDR" on the document..


Bomb design concepts

Arthur Compton asked theoretical physicist
J. Robert Oppenheimer J. Robert Oppenheimer (born Julius Robert Oppenheimer ; April 22, 1904 – February 18, 1967) was an American theoretical physics, theoretical physicist who served as the director of the Manhattan Project's Los Alamos Laboratory during World ...
of the University of California to take over research into fast neutron calculations—key to calculations of critical mass and weapon detonation—from
Gregory Breit Gregory Breit (, ; July 14, 1899 – September 13, 1981) was an American physicist born in Mykolaiv, Russian Empire (now Mykolaiv, Ukraine). He was a professor at New York University (1929–1934), University of Wisconsin–Madison (1934–194 ...
, who had quit on 18 May 1942 because of concerns over lax operational security. John H. Manley, a physicist at the Metallurgical Laboratory, was assigned to assist Oppenheimer by coordinating experimental physics groups scattered across the country. Oppenheimer and
Robert Serber Robert Serber (March 14, 1909 – June 1, 1997) was an American physicist who participated in the Manhattan Project. Serber's lectures explaining the basic principles and goals of the project were printed and supplied to all incoming scientific st ...
of the
University of Illinois The University of Illinois Urbana-Champaign (UIUC, U of I, Illinois, or University of Illinois) is a public university, public land-grant university, land-grant research university in the Champaign–Urbana metropolitan area, Illinois, United ...
examined the problems of
neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...
diffusion—how neutrons moved in a nuclear chain reaction—and
hydrodynamics In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids – liquids and gases. It has several subdisciplines, including (the study of air and other gases in ...
—how the explosion produced by a chain reaction might behave. To review this work and the general theory of fission reactions, Oppenheimer and Fermi convened meetings at the University of Chicago in June and at the University of California in July 1942 with theoretical physicists
Hans Bethe Hans Albrecht Eduard Bethe (; ; July 2, 1906 – March 6, 2005) was a German-American physicist who made major contributions to nuclear physics, astrophysics, quantum electrodynamics and solid-state physics, and received the Nobel Prize in Physi ...
,
John Van Vleck John Hasbrouck Van Vleck (; March 13, 1899 – October 27, 1980) was an American physicist and mathematician. He was co-awarded the Nobel Prize in Physics in 1977, for his contributions to the understanding of the behavior of electronic magnetis ...
, Edward Teller, Emil Konopinski, Robert Serber, Stan Frankel, and Eldred C. (Carlyle) Nelson, and
experimental physicist Experimental physics is the category of disciplines and sub-disciplines in the field of physics that are concerned with the observation of physical phenomena and experiments. Methods vary from discipline to discipline, from simple experiments and o ...
s
Emilio Segrè Emilio Gino Segrè ( ; ; 1 February 1905 – 22 April 1989) was an Italian-American nuclear physicist and radiochemist who discovered the elements technetium and astatine, and the antiproton, a subatomic antiparticle, for which he was award ...
,
Felix Bloch Felix Bloch (; ; 23 October 1905 – 10 September 1983) was a Swiss-American physicist who shared the 1952 Nobel Prize in Physics with Edward Mills Purcell "for their development of new methods for nuclear magnetic precision measurements and di ...
, Franco Rasetti, Manley, and
Edwin McMillan Edwin Mattison McMillan (September 18, 1907 – September 7, 1991) was an American physicist credited with being the first to produce a transuranium element, neptunium. For this, he shared the 1951 Nobel Prize in Chemistry with Glenn Seaborg. ...
. They tentatively confirmed that a fission bomb was theoretically possible. The properties of pure uranium-235 were relatively unknown, as were those of plutonium, which had only been isolated by
Glenn Seaborg Glenn Theodore Seaborg ( ; April 19, 1912February 25, 1999) was an American chemist whose involvement in the synthesis, discovery and investigation of ten transuranium elements earned him a share of the 1951 Nobel Prize in Chemistry. His work i ...
and his team in February 1941. The scientists at the July 1942 conference envisioned creating plutonium in nuclear reactors where uranium-238 atoms absorbed neutrons that had been emitted from fissioning uranium-235. At this point no reactor had been built, and only tiny quantities of plutonium were available from
cyclotron A cyclotron is a type of particle accelerator invented by Ernest Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Januar ...
s. Even by December 1943, only two milligrams had been produced. There were many ways of arranging the fissile material into a critical mass. The simplest was shooting a "cylindrical plug" into a sphere of "active material" with a "tamper"—dense material to focus neutrons inward and keep the reacting mass together to increase its efficiency. They also explored designs involving
spheroid A spheroid, also known as an ellipsoid of revolution or rotational ellipsoid, is a quadric surface (mathematics), surface obtained by Surface of revolution, rotating an ellipse about one of its principal axes; in other words, an ellipsoid with t ...
s, a primitive form of " implosion" suggested by
Richard C. Tolman Richard Chace Tolman (March 4, 1881 – September 5, 1948) was an American mathematical physicist and physical chemist who made many contributions to statistical mechanics and theoretical cosmology. He was a professor at the California Ins ...
, and the possibility of autocatalytic methods to increase the efficiency of the bomb as it exploded. As the idea of the fission bomb was theoretically settled—at least until more experimental data was available—Edward Teller pushed for discussion of a more powerful bomb: the "super", now usually referred to as a "
hydrogen bomb A thermonuclear weapon, fusion weapon or hydrogen bomb (H-bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lo ...
", which would use the force of a detonating fission bomb to ignite a
nuclear fusion Nuclear fusion is a nuclear reaction, reaction in which two or more atomic nuclei combine to form a larger nuclei, nuclei/neutrons, neutron by-products. The difference in mass between the reactants and products is manifested as either the rele ...
reaction in
deuterium Deuterium (hydrogen-2, symbol H or D, also known as heavy hydrogen) is one of two stable isotopes of hydrogen; the other is protium, or hydrogen-1, H. The deuterium nucleus (deuteron) contains one proton and one neutron, whereas the far more c ...
and
tritium Tritium () or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with a half-life of ~12.33 years. The tritium nucleus (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus of the ...
. Teller proposed scheme after scheme, but Bethe refused each one. The fusion idea was put aside to concentrate on producing fission bombs. Teller raised the speculative possibility that an atomic bomb might "ignite" the atmosphere because of a hypothetical fusion reaction of nitrogen nuclei. Bethe calculated that it was "extremely unlikely". A postwar report co-authored by Teller concluded that "whatever the temperature to which a section of the atmosphere may be heated, no self-propagating chain of nuclear reactions is likely to be started." In Serber's account, Oppenheimer mentioned the possibility of this scenario to
Arthur Compton Arthur Holly Compton (September 10, 1892 – March 15, 1962) was an American particle physicist who won the 1927 Nobel Prize in Physics for his discovery of the Compton effect, which demonstrated the particle nature of electromagnetic radiati ...
, who "didn't have enough sense to shut up about it. It somehow got into a document that went to Washington" and was "never laid to rest".


Organization


Manhattan District

The
Chief of Engineers The Chief of Engineers is a principal United States Army staff officer at The Pentagon. The Chief advises the Army on engineering matters, and serves as the Army's topographer and proponent for real estate and other related engineering programs. ...
, Major General Eugene Reybold, selected Colonel James C. Marshall to head the Army's part of the project in June 1942. Marshall created a liaison office in Washington, D.C., but established his temporary headquarters at 270 Broadway in New York, where he could draw on administrative support from the Corps of Engineers'
North Atlantic Division The North Atlantic Division of the U.S. Army Corps of Engineers is one of the nine permanent divisions within the Corps. Made up of roughly 3,600 employees in six districts and a Division (military), Division headquarters, the North Atlantic ...
. It was close to the Manhattan office of
Stone & Webster Stone & Webster was an American engineering services company based in Stoughton, Massachusetts. It was founded as an electrical testing lab and consulting firm by electrical engineers Charles A. Stone and Edwin S. Webster in 1889. In the earl ...
, the principal project contractor, and to Columbia University. He had permission to draw on his former command, the Syracuse District, for staff, and he started with Lieutenant Colonel Kenneth Nichols, who became his deputy.. Because most of his task involved construction, Marshall worked in cooperation with the head of the Corps of Engineers Construction Division, Major General Thomas M. Robins, and his deputy, Colonel
Leslie Groves Leslie Richard Groves Jr. (17 August 1896 – 13 July 1970) was a United States Army Corps of Engineers officer who oversaw the construction of the Pentagon and directed the Manhattan Project, a Classified information#Top_Secret_(TS), top sec ...
. Reybold, Somervell, and Styer decided to call the project "Development of Substitute Materials", but Groves felt that this would draw attention. Since engineer districts normally carried the name of the city where they were located, Marshall and Groves agreed to name the Army's component the Manhattan District; Reybold officially created this district on 13 August. Informally, it was known as the Manhattan Engineer District, or MED. Unlike other districts, it had no geographic boundaries, and Marshall had the authority of a division engineer. Development of Substitute Materials remained as the official codename of the project as a whole but was supplanted over time by "Manhattan". Marshall later conceded that, "I had never heard of atomic fission but I did know that you could not build much of a plant, much less four of them for $90 million." A single
TNT Troponin T (shortened TnT or TropT) is a part of the troponin complex, which are proteins integral to the contraction of skeletal and heart muscles. They are expressed in skeletal and cardiac myocytes. Troponin T binds to tropomyosin and helps ...
plant that Nichols had recently built in Pennsylvania had cost $128 million. Nor were they impressed with estimates to the nearest order of magnitude, which Groves compared with telling a caterer to prepare for between ten and a thousand guests. A survey team from Stone & Webster had already scouted a site for the production plants. The
War Production Board The War Production Board (WPB) was an agency of the United States government that supervised war production during World War II. President Franklin D. Roosevelt established it in January 1942, with Executive Order 9024. The WPB replaced the Su ...
recommended sites around
Knoxville, Tennessee Knoxville is a city in Knox County, Tennessee, United States, and its county seat. It is located on the Tennessee River and had a population of 190,740 at the 2020 United States census. It is the largest city in the East Tennessee Grand Division ...
, an isolated area where the
Tennessee Valley Authority The Tennessee Valley Authority (TVA) is a federally owned electric utility corporation in the United States. TVA's service area covers all of Tennessee, portions of Alabama, Mississippi, and Kentucky, and small areas of Georgia, North Carolin ...
could supply ample electric power and the rivers could provide cooling water for the reactors. After examining several sites, the survey team selected one near Elza, Tennessee. Conant advised that it be acquired at once, Styer agreed, but Marshall temporized, awaiting the results of Conant's reactor experiments. Of the prospective processes, only Lawrence's electromagnetic separation appeared sufficiently advanced for construction to commence. Marshall and Nichols began assembling the necessary resources. The first step was to obtain a high priority rating for the project. The top ratings were AA-1 through AA-4 in descending order, although there was a special AAA rating reserved for emergencies. Ratings AA-1 and AA-2 were for essential weapons and equipment, so Colonel Lucius D. Clay, the deputy chief of staff at Services and Supply for requirements and resources, felt that the highest rating he could assign was AA-3, although he was willing to provide a AAA rating on request for critical materials if the need arose. Nichols and Marshall were disappointed; AA-3 was the same priority as Nichols' TNT plant in Pennsylvania..


Military Policy Committee

Vannevar Bush became dissatisfied with Colonel Marshall's failure to get the project moving forward expeditiously and felt that more aggressive leadership was required. He spoke to Harvey Bundy and Generals Marshall, Somervell, and Styer about his concerns, advocating that the project be placed under a senior policy committee, with a prestigious officer, preferably Styer, as director. Somervell and Styer selected Groves for the post; General Marshall ordered that he be promoted to brigadier general,. as it was felt that the title "general" would hold more sway with the academic scientists working on the project.. Groves' orders placed him directly under Somervell rather than Reybold, with Colonel Marshall now answerable to Groves. Groves established his headquarters in Washington, D.C., in the New War Department Building, where Colonel Marshall had his liaison office. He assumed command of the Manhattan Project on 23 September 1942. Later that day, he attended a meeting called by Stimson, which established a Military Policy Committee, responsible to the Top Policy Group, consisting of Bush (with Conant as an alternate), Styer and
Rear Admiral Rear admiral is a flag officer rank used by English-speaking navies. In most European navies, the equivalent rank is called counter admiral. Rear admiral is usually immediately senior to commodore and immediately below vice admiral. It is ...
William R. Purnell. Tolman and Conant were later appointed as Groves' scientific advisers. On 19 September, Groves went to Donald Nelson, the chairman of the War Production Board, and asked for broad authority to issue a AAA rating whenever it was required. Nelson initially balked but quickly caved in when Groves threatened to go to the President. Groves promised not to use the AAA rating unless it was necessary. It soon transpired that for the routine requirements of the project the AAA rating was too high but the AA-3 rating was too low. After a long campaign, Groves finally received AA-1 authority on 1 July 1944. According to Groves, "In Washington you became aware of the importance of top priority. Most everything proposed in the Roosevelt administration would have top priority. That would last for about a week or two and then something else would get top priority". One of Groves' early problems was to find a director for
Project Y The Los Alamos Laboratory, also known as Project Y, was a secret scientific laboratory established by the Manhattan Project and overseen by the University of California during World War II. It was operated in partnership with the United State ...
, the group that would design and build the bomb. The obvious choice was one of the three laboratory heads, Urey, Lawrence, or Arthur Compton, but they could not be spared. Compton recommended Oppenheimer, who was already intimately familiar with the bomb design concepts. However, Oppenheimer had little administrative experience, and, unlike Urey, Lawrence, and Compton, had not won a Nobel Prize, which many scientists felt that the head of such an important laboratory should have. There were also concerns about Oppenheimer's security status, as many of his associates were
communists Communism () is a sociopolitical, philosophical, and economic ideology within the socialist movement, whose goal is the creation of a communist society, a socioeconomic order centered on common ownership of the means of production, d ...
, including his wife, Kitty; his girlfriend, Jean Tatlock; and his brother, Frank. A long conversation in October 1942 convinced Groves and Nichols that Oppenheimer thoroughly understood the issues involved in setting up a laboratory in a remote area and should be appointed as its director. Groves personally waived the security requirements and issued Oppenheimer's clearance on 20 July 1943.


Collaboration with the United Kingdom

The British and Americans exchanged nuclear information but did not initially combine their efforts; in 1940–41 the British project (
Tube Alloys Tube Alloys was the research and development programme authorised by the United Kingdom, with participation from Canada, to develop nuclear weapons during the Second World War. Starting before the Manhattan Project in the United States, the Bri ...
) was larger and more advanced. British leadership initially opposed an offer by Bush and Conant in August 1941 to pool the nations' atomic efforts, but the British, who had made significant advances in research early in the war, did not have the resources to carry it into development while devoting a large portion of their economy to the war; Tube Alloys soon fell behind its American counterpart. The roles of the two countries were reversed, and in January 1943 Conant notified the British that they would no longer receive atomic information except in certain areas. The British investigated the possibility of an independent nuclear program but determined that it could not be ready in time to impact the war in Europe. By March 1943 Conant decided that
James Chadwick Sir James Chadwick (20 October 1891 – 24 July 1974) was an English nuclear physicist who received the Nobel Prize in Physics in 1935 for his discovery of the neutron. In 1941, he wrote the final draft of the MAUD Report, which inspired t ...
and one or two other British scientists were important enough that the bomb design team at Los Alamos needed them, despite the risk of revealing weapon design secrets. In August 1943 Churchill and Roosevelt negotiated the
Quebec Agreement The Quebec Agreement was a secret agreement between the United Kingdom and the United States outlining the terms for the coordinated development of the science and engineering related to nuclear power, nuclear energy and specifically nuclear we ...
, which established the Combined Policy Committee to coordinate the efforts of the US and UK; Canada was not a signatory, but the Agreement provided for a Canadian representative on the Combined Policy Committee in view of Canada's contribution to the effort. An agreement between Roosevelt and Churchill known as the Hyde Park Aide-Mémoire, signed in late September 1944, extended the Quebec Agreement to the postwar period and suggested that "when a 'bomb' is finally available, it might perhaps, after mature consideration, be used against the Japanese, who should be warned that this bombardment will be repeated until they surrender". When cooperation resumed after the Quebec Agreement, the Americans' progress and expenditures amazed the British. Chadwick pressed for British involvement in the Manhattan Project to the fullest extent and abandoned hopes of an independent British project during the war. With Churchill's backing, he attempted to ensure that every request from Groves for assistance was honored. The British Mission that arrived in the United States in December 1943 included
Niels Bohr Niels Henrik David Bohr (, ; ; 7 October 1885 – 18 November 1962) was a Danish theoretical physicist who made foundational contributions to understanding atomic structure and old quantum theory, quantum theory, for which he received the No ...
, Otto Frisch,
Klaus Fuchs Klaus Emil Julius Fuchs (29 December 1911 – 28 January 1988) was a German theoretical physicist and atomic spy who supplied information from the American, British, and Canadian Manhattan Project to the Soviet Union during and shortly a ...
, Rudolf Peierls, and Ernest Titterton. More scientists arrived in early 1944. While those assigned to gaseous diffusion left by the fall of 1944, the thirty-five working under Oliphant with Lawrence at Berkeley were assigned to existing laboratory groups and most stayed until the end of the war. The nineteen sent to Los Alamos also joined existing groups, primarily related to implosion and bomb assembly, but not the plutonium-related ones. The Quebec Agreement specified that nuclear weapons would not be used against another country without the mutual consent of the US and UK. In June 1945, Wilson agreed that the nuclear bombing of Japan would be recorded as a decision of the Combined Policy Committee. The Combined Policy Committee created the Combined Development Trust in June 1944, with Groves as its chairman, to procure uranium and thorium ores on international markets. The
Belgian Congo The Belgian Congo (, ; ) was a Belgian colonial empire, Belgian colony in Central Africa from 1908 until independence in 1960 and became the Republic of the Congo (Léopoldville). The former colony adopted its present name, the Democratic Repu ...
and Canada held much of the world's uranium outside Eastern Europe, and the
Belgian Government in Exile The Belgian Government in London (; ), also known as the Pierlot IV Government, was the government in exile of Belgium between October 1940 and September 1944 during World War II. The government was wikt:tripartite, tripartite, involving minis ...
was in London. Britain agreed to give the United States most of the Belgian ore, as it could not use most of the supply without restricted American research. In 1944, the Trust purchased of uranium oxide ore from companies operating mines in the Belgian Congo. To avoid briefing US Secretary of the Treasury Henry Morgenthau Jr., a special account not subject to the usual auditing and controls was used to hold Trust monies. Between 1944 and his resignation from the Trust in 1947, Groves deposited a total of $37.5 million. Groves later said that the British scientists' direct contributions to the Manhattan Project were "helpful but not vital," but "there probably would have been no atomic bomb to drop on Hiroshima" without Britain's (particularly Churchill's) impetus. The British wartime participation was crucial to the success of their independent nuclear weapons program when the
McMahon Act The Atomic Energy Act of 1946 (McMahon Act) determined how the United States would control and manage the nuclear technology it had jointly developed with its World War II allies, the United Kingdom and Canada. Most significantly, the Act ru ...
of 1946 temporarily ended American nuclear cooperation.


Project sites


Oak Ridge

The day after he took over the project, Groves went to Tennessee with Colonel Marshall to inspect the proposed site there, and Groves was impressed. On 29 September 1942, United States Under Secretary of War
Robert P. Patterson Robert Porter Patterson Sr. (February 12, 1891 – January 22, 1952) was an American judge who served as United States Under Secretary of War, Under Secretary of War under President Franklin D. Roosevelt and US Secretary of War, U.S. Secretary of ...
authorized the Corps of Engineers to acquire of land by
eminent domain Eminent domain, also known as land acquisition, compulsory purchase, resumption, resumption/compulsory acquisition, or expropriation, is the compulsory acquisition of private property for public use. It does not include the power to take and t ...
at a cost of $3.5 million. An additional was subsequently acquired. About 1,000 families were affected by the order, which came into effect on 7 October. Protests, legal appeals, and a 1943 Congressional inquiry were to no avail.. By mid-November U.S. Marshals were posting notices to vacate on farmhouse doors, and construction contractors were moving in.. Some families were given two weeks' notice to vacate farms that had been their homes for generations. The ultimate cost of the land acquisition, which was not completed until March 1945, was only about $2.6 million—around $47 an acre. When presented with a proclamation declaring Oak Ridge a total exclusion area that no one could enter without military permission, the
Governor of Tennessee The governor of Tennessee is the head of government of the U.S. state of Tennessee and the commander-in-chief of the U.S. state, state's Tennessee Military Department, military forces. The governor is the only official in the Government of Tenne ...
, Prentice Cooper, angrily tore it up. Initially known as the Kingston Demolition Range, the site was officially renamed the Clinton Engineer Works (CEW) in early 1943. While Stone & Webster concentrated on the production facilities, the architectural and engineering firm
Skidmore, Owings & Merrill SOM, an initialism of its original name Skidmore, Owings & Merrill LLP, is a Chicago-based architectural, urban planning, and engineering firm. It was founded in 1936 by Louis Skidmore and Nathaniel Owings. In 1939, they were joined by engineer ...
developed a residential community for 13,000. The community was located on the slopes of Black Oak Ridge, from which the new town of Oak Ridge got its name. The Army presence at Oak Ridge increased in August 1943 when Nichols replaced Marshall as head of the Manhattan Engineer District. One of his first tasks was to move the district headquarters to Oak Ridge, although the name of the district did not change. In September 1943 the administration of community facilities was outsourced to Turner Construction Company through a subsidiary, the Roane-Anderson Company.. Chemical engineers were part of "frantic efforts" to make 10% to 12% enriched uranium 235, with tight security and fast approvals for supplies and materials. The population of Oak Ridge soon expanded well beyond the initial plans, and peaked at 75,000 in May 1945, by which time 82,000 people were employed at the Clinton Engineer Works,. and 10,000 by Roane-Anderson.


Los Alamos

The idea of locating Project Y at Oak Ridge was considered, but it was decided that it should be in a remote location. On Oppenheimer's recommendation, the search for a suitable site was narrowed to the vicinity of
Albuquerque, New Mexico Albuquerque ( ; ), also known as ABQ, Burque, the Duke City, and in the past 'the Q', is the List of municipalities in New Mexico, most populous city in the U.S. state of New Mexico, and the county seat of Bernalillo County, New Mexico, Bernal ...
, where Oppenheimer owned a ranch. On 16 November 1942, Oppenheimer, Groves, Dudley and others toured the vicinity of the Los Alamos Ranch School. Oppenheimer expressed a strong preference for the site, citing its natural beauty, which, it was hoped, would inspire those working on the project. The engineers were concerned about the poor access road, and whether the water supply would be adequate, but otherwise felt that it was ideal. Patterson approved the acquisition of the site on 25 November 1942, authorizing $440,000 for the purchase of pre-calculated , all but of which were already owned by the Federal Government..
Secretary of Agriculture The United States secretary of agriculture is the head of the United States Department of Agriculture. The position carries similar responsibilities to those of agriculture ministers in other governments The department includes several organiz ...
Claude R. Wickard granted about of
United States Forest Service The United States Forest Service (USFS) is an agency within the United States Department of Agriculture, U.S. Department of Agriculture. It administers the nation's 154 United States National Forest, national forests and 20 United States Natio ...
land to the War Department "for so long as the military necessity continues". Wartime land purchases eventually came to , but only $414,971 was spent. Work commenced in December 1942. Groves initially allocated $300,000 for construction, three times Oppenheimer's estimate, but by the time Sundt finished on 30 November 1943, over $7 million had been spent. During the war, Los Alamos was referred to as "Site Y" or "the Hill". Initially it was to have been a military laboratory with Oppenheimer and other researchers commissioned into the Army, but
Robert Bacher Robert Fox Bacher (August 31, 1905November 18, 2004) was an American nuclear physics, nuclear physicist and one of the leaders of the Manhattan Project. Born in Loudonville, Ohio, Bacher obtained his undergraduate degree and doctorate from the U ...
and Isidor Rabi balked at the idea and convinced Oppenheimer that other scientists would object. Conant, Groves, and Oppenheimer then devised a compromise whereby the laboratory was operated by the University of California under contract to the War Department. Dorothy McKibbin ran the branch office in Santa Fe, where she met new arrivals and issue them with passes.


Chicago

An Army-OSRD council on 25 June 1942 decided to build a
pilot plant A pilot plant is a pre-commercial production system that employs new production technology and/or produces small volumes of new technology-based products, mainly for the purpose of learning about the new technology. The knowledge obtained is then ...
for plutonium production in the Argonne Forest preserve, southwest of Chicago. This was designated Site A. In July, Nichols arranged for a lease of from the Cook County Forest Preserve District, and Captain James F. Grafton was appointed Chicago area engineer. It soon became apparent that the scale of operations was too great for the area, and it was decided to build the pilot plant at Oak Ridge and keep a research and testing facility in Chicago. Delays in establishing the plant at Site A led
Arthur Compton Arthur Holly Compton (September 10, 1892 – March 15, 1962) was an American particle physicist who won the 1927 Nobel Prize in Physics for his discovery of the Compton effect, which demonstrated the particle nature of electromagnetic radiati ...
to authorize the Metallurgical Laboratory to construct the first nuclear reactor beneath the
bleacher Bleachers (North American English), or stands, are raised, tiered rows of benches found at sports-fields and at other spectator events. Stairways provide access to the horizontal rows of seats, often with every other step enabling access to a ...
s of
Stagg Field Amos Alonzo Stagg Field is the name of two successive football fields for the University of Chicago. Beyond sports, the first Stagg Field (1893–1957), named for famed coach, Alonzo Stagg, is remembered for its role in a landmark scientific ac ...
at the University of Chicago. The reactor required an enormous amount of highly purified
graphite Graphite () is a Crystallinity, crystalline allotrope (form) of the element carbon. It consists of many stacked Layered materials, layers of graphene, typically in excess of hundreds of layers. Graphite occurs naturally and is the most stable ...
blocks and uranium in both metallic and powdered oxide forms. At the time, there was a limited source of pure
uranium Uranium is a chemical element; it has chemical symbol, symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Ura ...
metal; Frank Spedding of
Iowa State University Iowa State University of Science and Technology (Iowa State University, Iowa State, or ISU) is a Public university, public land-grant university, land-grant research university in Ames, Iowa, United States. Founded in 1858 as the Iowa Agricult ...
was able to produce only two
short ton The short ton (abbreviation: tn or st), also known as the US ton, is a measurement unit equal to . It is commonly used in the United States, where it is known simply as a ton; however, the term is ambiguous, the single word "ton" being variously ...
s. Three short tons was supplied by Westinghouse Lamp Plant, produced in a rush with makeshift process. A large square balloon was constructed by Goodyear Tire to encase the reactor. On 2 December 1942, a team led by Enrico Fermi initiated the first artificial self-sustaining nuclear chain reaction in an experimental reactor known as
Chicago Pile-1 Chicago Pile-1 (CP-1) was the first artificial nuclear reactor. On 2 December 1942, the first human-made self-sustaining nuclear chain reaction was initiated in CP-1 during an experiment led by Enrico Fermi. The secret development of the react ...
. The point at which a reaction becomes self-sustaining became known as "going critical". Compton reported the success to Conant in Washington, D.C., by a coded phone call, saying, "The Italian navigator ermihas just landed in the new world." In January 1943, Grafton's successor, Major Arthur V. Peterson, ordered Chicago Pile-1 dismantled and reassembled at the Site A in the forest preserve, as he regarded the operation of a reactor as too hazardous for a densely populated area. Site A continued scientific research as a secret extension of the Metallurgical Laboratory at the university. Chicago Pile-3, the first heavy water reactor, also went critical at this site, on 15 May 1944. After the war, operations at Site A were moved about to DuPage County, the current location of the
Argonne National Laboratory Argonne National Laboratory is a Federally funded research and development centers, federally funded research and development center in Lemont, Illinois, Lemont, Illinois, United States. Founded in 1946, the laboratory is owned by the United Sta ...
.


Hanford

By December 1942 there were concerns that even Oak Ridge was too close to a major population center (Knoxville) in the unlikely event of a major nuclear accident. Groves recruited
DuPont Dupont, DuPont, Du Pont, duPont, or du Pont may refer to: People * Dupont (surname) Dupont, also spelled as DuPont, duPont, Du Pont, or du Pont is a French surname meaning "of the bridge", historically indicating that the holder of the surname re ...
in November 1942 to be the prime contractor for the construction of the plutonium production complex. The President of the company, Walter S. Carpenter Jr., wanted no profit of any kind; for legal reasons a nominal fee of one dollar was agreed upon. DuPont recommended that the site be located far from the existing uranium production facility at Oak Ridge. In December 1942, Groves dispatched Colonel Franklin Matthias and DuPont engineers to scout potential sites. Matthias reported that
Hanford Site The Hanford Site is a decommissioned nuclear production complex operated by the United States federal government on the Columbia River in Benton County in the U.S. state of Washington. It has also been known as SiteW and the Hanford Nuclear R ...
near
Richland, Washington Richland () is a city in Benton County, Washington, United States. It is located in southeastern Washington at the confluence of the Yakima River, Yakima and the Columbia River, Columbia Rivers. As of the 2020 census, the city's population was ...
, was "ideal in virtually all respects". It was isolated and near the
Columbia River The Columbia River (Upper Chinook language, Upper Chinook: ' or '; Sahaptin language, Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river headwater ...
, which could supply sufficient water to cool the reactors. Groves visited the site in January and established the Hanford Engineer Works (HEW), codenamed "Site W". Under Secretary Patterson gave his approval on 9 February, allocating $5 million for the acquisition of . The federal government relocated some 1,500 residents of nearby settlements, as well as the
Wanapum The Wanapum (also Wanapam) tribe of Native Americans in the United States, Native Americans formerly lived along the Columbia River from above Priest Rapids down to the mouth of the Snake River in what is now the US state of Washington (state), Was ...
and other tribes using the area. A dispute arose with farmers over compensation for crops, which had already been planted. Where schedules allowed, the Army allowed the crops to be harvested, but this was not always possible.. The land acquisition process dragged on and was not completed before the end of the Manhattan Project in December 1946. The dispute did not delay work. Although progress on the reactor design at Metallurgical Laboratory and DuPont was not sufficiently advanced to accurately predict the scope of the project, a start was made in April 1943 on facilities for an estimated 25,000 workers, half of whom were expected to live on-site. By July 1944, some 1,200 buildings had been erected and nearly 51,000 people were living in the construction camp. As area engineer, Matthias exercised overall control of the site. At its peak, the construction camp was the third most populous town in Washington state. Hanford operated a fleet of over 900 buses, more than the city of Chicago. Like Los Alamos and Oak Ridge, Richland was a gated community with restricted access, but it looked more like a typical wartime American boomtown: the military profile was lower, and physical security elements like high fences and guard dogs were less evident.


Canadian sites

Canada provided research, extraction and production of uranium and plutonium, and Canadian scientists worked at Los Alamos.


British Columbia

Cominco had produced electrolytic hydrogen at
Trail, British Columbia Trail is a city in the western Kootenays region of the British Columbia Interior, Interior of British Columbia, Canada. It was named after the Dewdney Trail, which passed through the area. The town was first called Trail Creek or Trail Creek Lan ...
, since 1930. Urey suggested in 1941 that it could produce heavy water. To the existing $10 million plant consisting of 3,215 cells consuming 75 MW of hydroelectric power, secondary electrolysis cells were added to increase the deuterium concentration in the water from 2.3% to 99.8%. For this process, Hugh Taylor of Princeton developed a platinum-on-carbon
catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...
for the first three stages while Urey developed a nickel- chromia one for the fourth stage tower. The final cost was $2.8 million. The Canadian Government did not officially learn of the project until August 1942. Trail's heavy water production started in January 1944 and continued until 1956. Heavy water from Trail was used for Chicago Pile 3, the first reactor using heavy water and natural uranium, which went critical on 15 May 1944..


Ontario

The Chalk River, Ontario, site was established to rehouse the Allied effort at the Montreal Laboratory away from an urban area. A new community was built at
Deep River, Ontario Deep River is a town in Renfrew County, Ontario, Canada. Located along the Ottawa River, it lies about north-west of Ottawa on the Trans-Canada Highway. Deep River is opposite the Laurentian Mountains and the Province of Quebec. The name "Deep ...
, to provide residences and facilities for the team members. The site was chosen for its proximity to the industrial manufacturing area of Ontario and Quebec, and proximity to a rail head adjacent to a large military base, Camp Petawawa. Located on the Ottawa River, it had access to abundant water. The first director of the new laboratory was
Hans von Halban Hans Heinrich von Halban (24 January 1908 – 28 November 1964) was a French physicist of Austrian-Jewish descent. Family He is a descendant of Polish Jews who left Kraków for Vienna in the 1850s on his father's side. His grandfather, Heinric ...
. He was replaced by John Cockcroft in May 1944, who was succeeded by Bennett Lewis in September 1946. A pilot reactor known as ZEEP (zero-energy experimental pile) became the first Canadian reactor, and the first to be completed outside the United States, when it went critical in September 1945; ZEEP remained in use by researchers until 1970. A larger 10 MW NRX reactor, which was designed during the war, was completed and went critical in July 1947.


Northwest Territories

The Eldorado Mine at Port Radium was a source of uranium ore.


Heavy water sites

Although DuPont's preferred designs for the nuclear reactors were helium cooled and used graphite as a moderator, DuPont still expressed an interest in using heavy water as a backup. The '' P-9 Project'' was the government's codename for the heavy water production program. It was estimated that of heavy water would be required per month. The plant at Trail, then under construction, could produce per month. Groves therefore authorized DuPont to establish heavy water facilities at the Morgantown Ordnance Works, near
Morgantown, West Virginia Morgantown is a city in Monongalia County, West Virginia, United States, and its county seat. It is situated along the Monongahela River in North Central West Virginia and is the home of West Virginia University. The population was 30,347 at the 2 ...
; at the Wabash River Ordnance Works, near Dana and
Newport, Indiana Newport is a town in Vermillion Township, Vermillion County, Indiana, Vermillion Township, Vermillion County, Indiana, Vermillion County, in the U.S. state of Indiana. The population was 515 at the 2010 census. The town is the county seat of Vermi ...
; and at the Alabama Ordnance Works, near Childersburg and Sylacauga, Alabama. Although known as Ordnance Works and paid for under Ordnance Department contracts, they were built and operated by the Army Corps of Engineers. The American plants used a process different from Trail's; heavy water was extracted by distillation, taking advantage of the slightly higher boiling point of heavy water.


Uranium


Ore

The key raw material for the project was uranium, which was used as fuel for the reactors, as feed that was transformed into plutonium, and, in its enriched form, in the atomic bomb itself. There were four known major deposits of uranium in 1940: in Colorado, in northern Canada, in Joachimsthal in Czechoslovakia, and in the
Belgian Congo The Belgian Congo (, ; ) was a Belgian colonial empire, Belgian colony in Central Africa from 1908 until independence in 1960 and became the Republic of the Congo (Léopoldville). The former colony adopted its present name, the Democratic Repu ...
. All but Joachimstal were in Allied hands. A 1942 survey determined that sufficient quantities of uranium were available to satisfy the project's requirements. Nichols arranged with the
State Department The United States Department of State (DOS), or simply the State Department, is an executive department of the U.S. federal government responsible for the country's foreign policy and relations. Equivalent to the ministry of foreign affairs o ...
for export controls to be placed on
uranium oxide Uranium oxide is an oxide of the element uranium. The metal uranium forms several oxides: * Uranium dioxide or uranium(IV) oxide (UO2, the mineral uraninite or pitchblende) * Diuranium pentoxide or uranium(V) oxide (U2O5) * Uranium trioxide or ...
and negotiated for the purchase of of uranium ore from the Belgian Congo that was being stored in a warehouse on
Staten Island Staten Island ( ) is the southernmost of the boroughs of New York City, five boroughs of New York City, coextensive with Richmond County and situated at the southernmost point of New York (state), New York. The borough is separated from the ad ...
and the remaining stocks of mined ore stored in the Congo. He negotiated with Eldorado Gold Mines for the purchase of ore from its refinery in Port Hope, Ontario. The Canadian government subsequently bought up the company's stock until it acquired a controlling interest. Of these ores, those from the Belgian Congo contained the most uranium per mass of rock by far. Beyond their wartime needs, American and British leaders concluded that it was in their countries' interest to control as much of the world's uranium deposits as possible. The
Shinkolobwe Shinkolobwe, or Kasolo, or Chinkolobew, or Shainkolobwe, was a radium and uranium mine in the Haut-Katanga Province of the Democratic Republic of the Congo (DRC), located west of Likasi (formerly Jadotville), south of Kambove, and about northwe ...
mine was flooded and closed, and Nichols unsuccessfully attempted to negotiate its reopening and the sale of the entire future output to the United States with
Edgar Sengier Edgar Edouard Bernard Sengier (9 October 1879 – 26 July 1963) was a Belgian mining engineer and director of the Union Minière du Haut Katanga mining company that operated in the Belgian Congo during World War II. Sengier is credited ...
, the director of the company that owned the mine, the Union Minière du Haut-Katanga. The matter was then taken up by the Combined Policy Committee. As 30 percent of Union Minière's stock was controlled by British interests, the British took the lead in negotiations. Sir John Anderson and Ambassador John Winant hammered out a deal with Sengier and the Belgian government in May 1944 for the mine to be reopened and of ore to be purchased at $1.45 a pound. To avoid dependence on the British and Canadians for ore, Groves also arranged for the purchase of US Vanadium Corporation's stockpile in Uravan, Colorado. The raw ore was dissolved in nitric acid to produce uranyl nitrate, which was processed into uranium trioxide, which was reduced to highly pure uranium dioxide. By July 1942, Mallinckrodt was producing a ton of highly pure oxide a day, but turning this into uranium metal initially proved more difficult. Production was too slow and quality was unacceptably low. A branch of the Metallurgical Laboratory was established at Iowa State College in Ames, Iowa, under Frank Spedding to investigate alternatives. This became known as the Ames Project, and its Ames process became available in 1943.


Isotope separation

Natural uranium consists of 99.3% uranium-238 and 0.7% uranium-235, but as only the latter is fissile it must be physically separated from the more plentiful isotope. Various methods were considered for uranium enrichment, most of which was carried out at Oak Ridge. The most obvious technology, the centrifuge, failed, but electromagnetic separation, gaseous diffusion, and thermal diffusion technologies were all successful and contributed to the project. In February 1943, Groves came up with the idea of using the output of some plants as the input for others.


Centrifuges

The centrifuge process was regarded as the only promising separation method in April 1942. Jesse Beams had developed such a process in the 1930s, but had encountered technical difficulties. In 1941 he began working with uranium hexafluoride, the only known gaseous compound of uranium, and was able to separate uranium-235. At Columbia, Karl P. Cohen produced a body of mathematical theory making it possible to design a centrifugal separation unit, which Westinghouse undertook to construct. Scaling this up to a production plant presented a formidable technical challenge. Urey and Cohen estimated that producing a kilogram (2.2 lb) of uranium-235 per day would require up to 50,000 centrifuges with rotors, or 10,000 centrifuges with rotors, assuming that 4-meter rotors could be built. The prospect of keeping so many rotors operating continuously at high speed appeared daunting, and when Beams ran his experimental apparatus, he obtained only 60% of the predicted yield, indicating that more centrifuges were required. Beams, Urey and Cohen then began work on a series of improvements which promised to increase efficiency. However, frequent failures of motors, shafts and bearings at high speeds delayed work on the pilot plant. In November 1942 the centrifuge process was abandoned by the Military Policy Committee. Successful gas centrifuges of the Zippe-type centrifuge, Zippe-type design were instead developed in the Soviet Union after the war. It eventually became the preferred method of uranium isotope separation, being far more economical.


Electromagnetic separation

Electromagnetic isotope separation was developed at the University of California Radiation Laboratory. This method employed devices known as calutrons. The name was derived from the words ''California'', ''university'' and ''cyclotron''.. In the electromagnetic process, a magnetic field deflected charged particles according to mass. The process was neither scientifically elegant nor industrially efficient.. Compared with a gaseous diffusion plant or a nuclear reactor, an electromagnetic separation plant would consume more scarce materials, require more manpower to operate, and cost more to build. Nonetheless, the process was approved because it was based on proven technology and therefore represented less risk. Moreover, it could be built in stages, and rapidly reach industrial capacity. Marshall and Nichols discovered that the electromagnetic isotope separation process would require of copper, which was in desperately short supply. However, silver could be substituted, in an 11:10 copper to silver ratio. On 3 August 1942, Nichols met with United States Deputy Secretary of the Treasury, Under Secretary of the Treasury Daniel W. Bell and asked for the transfer of 6,000 tons of silver bullion from the West Point Bullion Depository. Ultimately were used. The silver bars were cast into cylindrical billets, extruded into strips, and wound onto magnetic coils.. Responsibility for the design and construction of the electromagnetic separation plant, which came to be called Y-12 National Security Complex, Y-12, was assigned to Stone & Webster in June 1942. The design called for five first-stage processing units, known as Alpha racetracks, and two units for final processing, known as Beta racetracks. In September 1943 Groves authorized construction of four more racetracks, known as Alpha II. Construction began in February 1943. The second Alpha I was operational at the end of January 1944, the first Beta and first and third Alpha I's came online in March, and the fourth Alpha I was operational in April. The four Alpha II racetracks were completed between July and October 1944. Tennessee Eastman was contracted to manage Y-12. The calutrons were turned over to trained Tennessee Eastman operators known as the Calutron Girls. The calutrons initially enriched the uranium-235 content to between 13% and 15%, and shipped the first few hundred grams of this to Los Alamos in March 1944. Only 1 part in 5,825 of the uranium feed emerged as product. Much of the rest was splattered over equipment in the process. Strenuous recovery efforts helped raise production to 10% of the uranium-235 feed by January 1945. In February the Alpha racetracks began receiving slightly enriched (1.4%) feed from the new S-50 thermal diffusion plant, and the next month they received enhanced (5%) feed from the K-25 gaseous diffusion plant. By August, K-25 was producing uranium sufficiently enriched to feed directly into the Beta tracks.


Gaseous diffusion

The most promising but also the most challenging method of isotope separation was gaseous diffusion. Graham's law states that the rate of effusion of a gas is inversely proportional to the square root of its molecular mass, so in a box containing a semi-permeable membrane and a mixture of two gases, the lighter molecules will pass out of the container more rapidly than the heavier molecules. The idea was that such boxes could be formed into a cascade of pumps and membranes, with each successive stage containing a slightly more enriched mixture. Research into the process was carried out at Columbia University by a group that included Harold Urey, Karl P. Cohen, and John R. Dunning. In November 1942 the Military Policy Committee approved the construction of a 600-stage gaseous diffusion plant. On 14 December, M. W. Kellogg accepted an offer to construct the plant, which was codenamed K-25. A separate corporate entity called Kellex was created for the project. The process faced formidable technical difficulties. The highly corrosive gas uranium hexafluoride had to be used as no substitute could be found, and the motors and pumps had to be vacuum tight and enclosed in inert gas. The biggest problem was the design of the barrier, which had to be strong, porous and resistant to corrosion. Edward Adler and Edward Norris created a mesh barrier from electroplated nickel. A six-stage pilot plant was built at Columbia to test the process, but the prototype proved to be too brittle. A rival barrier was developed from powdered nickel by Kellex, the Bell Telephone Laboratories and the Bakelite Corporation. In January 1944, Groves ordered the Kellex barrier into production. Kellex's design for K-25 called for a four-story long U-shaped structure containing 54 contiguous buildings. These were divided into nine sections containing cells of six stages. A survey party began construction by marking out the site in May 1943. Work on the main building began in October 1943, and the six-stage pilot plant was ready for operation on 17 April 1944. In 1945 Groves canceled the upper stages, directing Kellex to instead design and build a 540-stage side feed unit, which became known as K-27. Kellex transferred the last unit to the operating contractor, Union Carbide and Carbon, on 11 September 1945. The total cost, including the K-27 plant completed after the war, came to $480 million. The production plant commenced operation in February 1945, and as cascade after cascade came online, the quality of the product increased. By April 1945, K-25 had attained a 1.1% enrichment, and the output of the S-50 thermal diffusion plant began being used as feed. Some product produced the next month reached nearly 7% enrichment. In August, the last of the 2,892 stages commenced operation. K-25 and K-27 achieved their full potential in the early postwar period, when they eclipsed the other production plants and became the prototypes for a new generation of plants.


Thermal diffusion

The thermal diffusion process was based on Sydney Chapman (mathematician), Sydney Chapman and David Enskog's Chapman–Enskog theory, theory, which explained that when a mixed gas passes through a temperature gradient, the heavier one tends to concentrate at the cold end and the lighter one at the warm end. It was developed by US Navy scientists, but was not one of the enrichment technologies initially selected for use in the Manhattan Project. This was primarily due to doubts about its technical feasibility, but the inter-service rivalry between the Army and Navy also played a part. The Naval Research Laboratory continued the research under Philip Abelson's direction, but there was little contact with the Manhattan Project until April 1944, when Captain (United States O-6), Captain William S. Parsons, the naval officer in charge of ordnance development at Los Alamos, brought Oppenheimer news of encouraging progress on thermal diffusion. Oppenheimer informed Groves, who approved construction of a thermal plant on 24 June 1944. Groves contracted with the H. K. Ferguson Company of Cleveland, Ohio, to build the thermal diffusion plant, which was designated S-50. Plans called for the installation of 2,142 diffusion columns arranged in 21 racks. Inside each column were three concentric tubes. Steam, obtained from the nearby K-25 powerhouse at a pressure of and temperature of , flowed downward through the innermost nickel pipe, while water at flowed upward through the outermost iron pipe. The uranium hexafluoride flowed in the middle copper pipe, and isotope separation of the uranium occurred between the nickel and copper pipes. Work commenced on 9 July 1944, and S-50 began partial operation in September. Leaks limited production and forced shutdowns over the next few months, but in June 1945 the S-50 plant produced of slightly enriched product. By March 1945, all 21 production racks were operating. Initially the output of S-50 was fed into Y-12, but starting in March 1945 all three enrichment processes were run in series. S-50 became the first stage, enriching the uranium from 0.71% to 0.89% uranium-235. This was then fed into the gaseous diffusion process in the K-25 plant, which produced a product enriched to about 23%. In turn, this was fed into Y-12, which boosted it to about 89%, sufficient for use in nuclear weapons. About of uranium enriched to 89% was delivered to Los Alamos by July 1945. The entire 50 kg, along with some 50%-enriched, averaging out to about 85% enriched, were used in the first
Little Boy Little Boy was a type of atomic bomb created by the Manhattan Project during World War II. The name is also often used to describe the specific bomb (L-11) used in the bombing of the Japanese city of Hiroshima by the Boeing B-29 Superfortress ...
bomb..


Plutonium

The second line of development pursued by the Manhattan Project used plutonium. Although small amounts of plutonium exist in nature, the best way to obtain large quantities is via a reactor. Natural uranium is bombarded by neutrons and nuclear transmutation, transmuted into uranium-239, which rapidly decays, first into neptunium-239 and then into plutonium-239. As only a small amount will be transformed, the plutonium must be chemically separated from the remaining uranium, from any initial impurities, and from fission products..


X-10 Graphite Reactor

In March 1943, DuPont began construction of a plutonium plant on a site at Oak Ridge. Intended as a pilot plant for the larger production facilities at Hanford, it included the air-cooled X-10 Graphite Reactor, a chemical separation plant, and support facilities. Because of the subsequent decision to construct water-cooled reactors at Hanford, only the chemical separation plant operated as a true pilot.. The X-10 Graphite Reactor consisted of a huge block of graphite, per side, weighing around , surrounded by of high-density concrete as a radiation shield. The greatest difficulty was encountered with the uranium slugs produced by Mallinckrodt and Metal Hydrides. These had to be coated in aluminum to avoid corrosion and the escape of fission products into the cooling system. The Grasselli Chemical Company attempted to develop a tinning#Hot-dipping, hot dipping process without success. Alcoa tried canning, developing a new process for flux-less welding; 97% of the cans passed a standard vacuum test, but high temperature tests indicated a failure rate of more than 50%. Nonetheless, production began in June 1943. The Metallurgical Laboratory eventually developed an improved welding technique with the help of General Electric, which was incorporated into the production process in October 1943. The X-10 Graphite Reactor went critical on 4 November 1943 with about of uranium. A week later the load was increased to , raising its power generation to 500 kW, and by the end of the month the first 500 mg of plutonium was created. Gradual modifications raised the power to 4,000 kW in July 1944. X-10 operated as a production plant until January 1945, when it was turned over to research..


Hanford reactors

Although an air-cooled design was chosen for the reactor at Oak Ridge to facilitate rapid construction, this was impractical for the much larger production reactors. Initial designs by the Metallurgical Laboratory and DuPont used helium for cooling, before they determined that a water-cooled reactor was simpler, cheaper and quicker to build. The design did not become available until 4 October 1943; in the meantime, Matthias concentrated on improving the Hanford Site by erecting accommodations, improving the roads, building a railway switch line, and upgrading the electricity, water and telephone lines. As at Oak Ridge, the most difficulty was encountered while canning the uranium slugs, which commenced at Hanford in March 1944. They were pickling (metal), pickled to remove dirt and impurities, dipped in molten bronze, tin, and silumin, aluminum-silicon alloy, canned using hydraulic presses, and then capped using arc welding under an argon atmosphere. Finally, they were tested to detect holes or faulty welds. Disappointingly, most canned slugs initially failed the tests, resulting in an output of only a handful per day. But steady progress was made and by June 1944 production increased to the point where it appeared that enough canned slugs was available to start B-Reactor, Reactor B on schedule in August 1944. Work began on Reactor B, the first of six planned 250 MW reactors, on 10 October 1943. The reactor complexes were given letter designations A through F, with B, D and F sites developed first, as this maximized the distance between the reactors. They were the only ones constructed during the Manhattan Project. Some of steel, of concrete, 50,000 concrete blocks and 71,000 concrete bricks were used to construct the high building. Construction of the reactor itself commenced in February 1944. Watched by Compton, Matthias, DuPont's Crawford Greenewalt, Leona Woods and Fermi, who inserted the first slug, the reactor was powered up beginning on 13 September 1944. Over the next few days, 838 tubes were loaded and the reactor went critical. Shortly after midnight on 27 September, the operators began to withdraw the control rods to initiate production. At first all appeared well but around 03:00 the power level started to drop and by 06:30 the reactor had shut down completely. The cooling water was investigated to see if there was a leak or contamination. The next day the reactor started up again, only to shut down once more.. Fermi contacted Chien-Shiung Wu, who identified the cause of the problem as neutron poisoning from xenon-135, which has a half-life of 9.2 hours. Fermi, Woods, Donald J. Hughes and John Archibald Wheeler then calculated the nuclear cross section of xenon-135, which turned out to be 30,000 times that of uranium. DuPont engineer George Graves had deviated from the Metallurgical Laboratory's original design in which the reactor had 1,500 tubes arranged in a circle, and had added an additional 504 tubes to fill in the corners. The scientists had originally considered this overengineering a waste of time and money, but Fermi realized that by loading all 2,004 tubes, the reactor could reach the required power level and efficiently produce plutonium. Reactor D was started on 17 December 1944 and Reactor F on 25 February 1945..


Separation process

Meanwhile, the chemists considered how plutonium could be separated from uranium when its chemical properties were not known. Working with the minute quantities of plutonium available at the Metallurgical Laboratory in 1942, a team under Charles M. Cooper developed a fluoride selective electrode, lanthanum fluoride process which was chosen for the pilot separation plant. A second separation process, the bismuth phosphate process, was subsequently developed by Seaborg and Stanly G. Thomson. Greenewalt favored the bismuth phosphate process due to the corrosive nature of lanthanum fluoride, and it was selected for the Hanford separation plants. Once X-10 began producing plutonium, the pilot separation plant was put to the test. The first batch was processed at 40% efficiency but over the next few months this was raised to 90%. At Hanford, top priority was initially given to the installations in the 300 area: buildings for testing materials, preparing uranium, and assembling and calibrating instrumentation. One of the buildings housed the canning equipment for the uranium slugs, while another contained a small test reactor. Notwithstanding its priority, work on the 300 area fell behind schedule due to the unique and complex nature of the facilities, and wartime shortages of labor and materials. Early plans called for the construction of two separation plants in each of the areas known as 200-West and 200-East. This was subsequently reduced to two, the T and U plants, in 200-West and one, the B plant, at 200-East. Each separation plant consisted of four buildings: a process cell building or "canyon" (known as 221), a concentration building (224), a purification building (231) and a magazine store (213). The canyons were each long and wide. Each consisted of forty cells. Work began on 221-T and 221-U in January 1944, with the former completed in September and the latter in December. The 221-B building followed in March 1945. Because of the high levels of radioactivity involved, work in the separation plants had to be conducted by remote control using closed-circuit television, something unheard of in 1943. Maintenance was carried out with the aid of an overhead crane and specially designed tools. The 224 buildings were smaller because they had less material to process, and it was less radioactive. The 224-T and 224-U buildings were completed on 8 October 1944, and 224-B followed on 10 February 1945. The purification methods that were eventually used in 231-W were still unknown when construction commenced on 8 April 1944, but the plant was complete and the methods were selected by the end of the year. On 5 February 1945, Matthias hand-delivered the first shipment of 80 g of 95%-pure plutonium nitrate to a Los Alamos courier in Los Angeles.


Weapon design

In 1943, development efforts were directed to a gun-type fission weapon with plutonium called Thin Man (nuclear bomb), Thin Man. Initial research on the properties of plutonium was done using cyclotron-generated plutonium-239, which was extremely pure but could only be created in very small amounts. Los Alamos received the first sample of plutonium from the Clinton X-10 reactor in April 1944 and within days Emilio Segrè discovered a problem: the reactor-bred plutonium had a higher concentration of plutonium-240, resulting in up to five times the spontaneous fission rate of cyclotron plutonium. This rendered it unsuitable for use in a gun-type weapon, for the plutonium-240 would start the chain reaction too soon, causing a predetonation that would disperse the critical mass after a minimal amount of plutonium had fissioned (a fizzle (nuclear test), fizzle). A higher-velocity gun was suggested but found to be impractical. The possibility of separating the isotopes was also considered and rejected, as plutonium-240 is even harder to separate from plutonium-239 than uranium-235 from uranium-238, and attempting it "would postpone the weapon indefinitely". Work on an alternative method of bomb design, known as implosion, had begun earlier under the direction of the physicist Seth Neddermeyer. Implosion used explosives to crush a subcritical sphere of fissile material into a smaller and denser form. The critical mass is assembled in much less time than with the gun method. When the fissile atoms are packed closer together, the rate of neutron capture increases, so it also makes more efficient use of fissionable material. Neddermeyer's 1943 and early 1944 investigations showed promise, but also made it clear that an implosion weapon was more complex than the gun-type design from both a theoretical and an engineering perspective. In September 1943, John von Neumann, who had experience with shaped charges, proposed using a spherical configuration instead of the cylindrical one that Neddermeyer was working on. An accelerated effort on the implosion design, codenamed
Fat Man "Fat Man" (also known as Mark III) was the design of the nuclear weapon the United States used for seven of the first eight nuclear weapons ever detonated in history. It is also the most powerful design to ever be used in warfare. A Fat Man ...
, began in August 1944 when Oppenheimer implemented a sweeping reorganization of the Los Alamos laboratory to focus on implosion. Two new groups were created at Los Alamos to develop the implosion weapon, X (for explosives) Division headed by explosives expert George Kistiakowsky and G (for gadget) Division under Robert Bacher. The new design featured explosive lenses that focused the implosion into a spherical shape. The design of lenses turned out to be slow, difficult and frustrating. Various explosives were tested before settling on composition B and baratol. The final design resembled a soccer ball, with 20 hexagonal and 12 pentagonal lenses, each weighing about . Getting the detonation just right required fast, reliable and safe electrical detonators, of which there were two for each lens for reliability. They used exploding-bridgewire detonators, a new invention developed at Los Alamos by a group led by Luis Walter Alvarez, Luis Alvarez. To study the behavior of converging shock waves, Robert Serber devised the RaLa Experiment, which used the short-lived radioisotope lanthanum-140, a potent source of gamma radiation. The gamma ray source was placed in the center of a metal sphere surrounded by the explosive lenses, which in turn were inside in an ionization chamber. This allowed the taking of an X-ray movie of the implosion. The lenses were designed primarily using this series of tests. In his history of the Los Alamos project, David Hawkins (philosopher), David Hawkins wrote: "RaLa became the most important single experiment affecting the final bomb design". Within the explosives was an aluminum pusher, which provided a smooth transition from the relatively low-density explosive to the next layer, the Tamper (nuclear weapons), tamper of natural uranium. Its main job was to hold the critical mass together as long as possible, but it would also reflect neutrons into the core and some of its uranium would fission. To prevent predetonation by an external neutron, the tamper was coated in a thin layer of neutron-absorbing boron. A polonium-beryllium modulated neutron initiator, known as an "urchin", was developed to start the chain reaction at precisely the right moment. This work on the chemistry and metallurgy of radioactive polonium was directed by Charles Allen Thomas of the Monsanto Company and became known as the Dayton Project. Testing required up to 500 Curie (unit), curies per month of polonium, which Monsanto was able to deliver. The whole assembly was encased in a duralumin bomb casing to protect it from bullets and flak.. The ultimate task of the metallurgists was to determine how to cast plutonium into a sphere. The difficulties became apparent when attempts to measure the density of plutonium gave inconsistent results. At first contamination was suspected, but it was soon determined that there were multiple allotropes of plutonium. The brittle α phase that exists at room temperature changes to the plastic β phase at higher temperatures. Attention then shifted to the even more malleable δ phase that normally exists in the 300 °C to 450 °C range. It was found that this was stable at room temperature when alloyed with aluminum, but aluminum emits neutrons when bombarded with alpha particles, which would exacerbate the pre-ignition problem. The metallurgists then hit upon using a plutonium-gallium alloy, which stabilized the δ phase and could be hot pressing, hot pressed into the desired spherical shape. As plutonium was found to corrode readily, the sphere was coated with nickel. The work proved dangerous. By the end of the war, half the chemists and metallurgists had to be removed from work with plutonium when unacceptably high levels of the element was detected in their urine. A minor fire at Los Alamos in January 1945 led to a fear that a fire in the plutonium laboratory might contaminate the whole town, and Groves authorized the construction of a new facility for plutonium chemistry and metallurgy, which became known as the DP-site. The hemispheres for the first plutonium pit (nuclear weapon), pit (or core) were produced and delivered on 2 July 1945. Three more hemispheres followed on 23 July and were delivered three days later. In contrast to the plutonium Fat Man, the uranium gun-type Little Boy weapon was straightforward if not trivial to design. Overall responsibility for it was assigned to Parsons's Ordnance (O) Division, with the design, development, and technical work at Los Alamos consolidated under Lieutenant Commander (United States), Lieutenant Commander Francis Birch (geophysicist), Francis Birch's group. The gun-type design now had to work with enriched uranium only, and this allowed the design to be greatly simplified. A high-velocity gun was no longer required, and a simpler weapon was substituted. Research into the Super was also pursued, although it was considered secondary to the development of a fission bomb. The effort was directed by Teller, who was its most enthusiastic proponent. The F-1 (Super) Group calculated that burning of liquid
deuterium Deuterium (hydrogen-2, symbol H or D, also known as heavy hydrogen) is one of two stable isotopes of hydrogen; the other is protium, or hydrogen-1, H. The deuterium nucleus (deuteron) contains one proton and one neutron, whereas the far more c ...
would release the energy of , enough to devastate . In a final report on the Super in June 1946, Teller remained upbeat about the prospect of it being successfully developed, although that opinion was not universal.


Trinity

Because of the complexity of an implosion-style weapon, it was decided that, despite the waste of fissile material, a full-scale nuclear test was required. Oppenheimer codenamed it "Trinity". In March 1944, planning for the test was assigned to Kenneth Bainbridge, who selected the Alamogordo Bombing Range for the test site. A base camp was constructed with barracks, warehouses, workshops, an explosive magazine and a commissary. A pre-test explosion was conducted on 7 May 1945 to calibrate the instruments. A wooden test platform was erected from future Trinity Ground Zero and piled with about of high explosives spiked with nuclear fission products. Groves did not relish the prospect of explaining to a Senate committee the loss of a billion dollars worth of plutonium, so a cylindrical containment vessel codenamed "Jumbo" was constructed to recover the active material in the event of a failure. It was fabricated at great expense from of iron and steel. By the time it arrived, however, confidence in the implosion method was high enough, and the availability of plutonium was sufficient, that Oppenheimer decided not to use it. Instead, it was placed atop a steel tower from the weapon as a rough measure of the explosion's power. Jumbo survived, although its tower did not, adding credence to the belief that Jumbo would have successfully contained a Fizzle (nuclear explosion), fizzled explosion.. For the actual test, the weapon, nicknamed "the gadget", was hoisted to the top of a steel tower, as detonation at that height would give a better indication of how the weapon would behave when dropped from a bomber. Detonation in the air maximized the energy applied directly to the target and generated less nuclear fallout. The gadget was assembled under the supervision of Norris Bradbury at the nearby McDonald Ranch House on 13 July, and precariously winched up the tower the following day. At 05:30 on 16 July 1945 the gadget exploded with an TNT equivalent, energy equivalent of around 20 kilotons of TNT, leaving a crater of trinitite (radioactive glass) in the desert wide. The shock wave was felt over away, and the mushroom cloud reached in height. It was heard as far away as El Paso, Texas, so Groves issued a cover story about an ammunition magazine explosion at Alamogordo Field involving gas shells. Oppenheimer later claimed that, while witnessing the explosion, he thought of a verse from the Hindu holy book, the ''Bhagavad Gita'' (XI,12): together with verse (XI,32), which he translated as "Now I am become Death, destroyer of worlds". The test was significantly more successful than had been anticipated; this was immediately cabled to Stimson, who was then at the Potsdam Conference, and Groves hastily prepared a lengthier report sent via courier. President Harry S. Truman was powerfully and positively affected by the news. Stimson noted in his diary that when he shared it with Churchill, Churchill remarked: "Now I know what happened to Truman yesterday. I couldn't understand it. When he got to the meeting after having read this report, he was a changed man. He told the Russians just where they got on and off and generally bossed the whole meeting."


Personnel

At its peak in June 1944, the Manhattan Project employed about 129,000 workers, of whom 84,500 were construction workers, 40,500 were plant operators and 1,800 were military personnel. As construction activity declined, the workforce fell to 100,000 a year later, but the number of military personnel increased to 5,600. Procuring the required numbers of workers, especially highly skilled workers, in competition with other vital wartime programs proved very difficult. Due to high turnover, over 500,000 people worked on the project. Most African Americans were employed in low-level jobs, but there were a few African-American scientists and technicians on the Manhattan Project, African-American scientists and technicians. The unique labor and security requirements also resulted in the Manhattan Project having a higher percentage of women in technical roles than later government projects. In 1943, Groves obtained a special temporary priority for labor from the War Manpower Commission. In March 1944, both the War Production Board and the War Manpower Commission gave the project their highest priority. The Kansas commission director stated that from April to July 1944 every qualified applicant in the state who visited a United States Employment Service office was urged to work at the Hanford Site. No other job was offered until the applicant definitively rejected the offer. Tolman and Conant, in their role as the project's scientific advisers, drew up a list of candidate scientists and had them rated by scientists already working on the project. Groves then sent a personal letter to the head of their university or company asking for them to be released for essential war work. One source of skilled personnel was the Army itself, particularly the Army Specialized Training Program. In 1943, the MED created the Special Engineer Detachment (SED), with an authorized strength of 675. Technicians and skilled workers drafted into the Army were assigned to the SED. Another source was the Women's Army Corps (WAC). Initially intended for clerical tasks handling classified material, the WACs were soon tapped for technical and scientific tasks as well. On 1 February 1945, all military personnel assigned to the MED, including all SED detachments, were assigned to the 9812th Technical Service Unit, except at Los Alamos, where military personnel other than SED, including the WACs and Military Police, were assigned to the 4817th Service Command Unit. An associate professor of Radiology at the University of Rochester School of Medicine, Stafford L. Warren, was commissioned as a colonel in the United States Army Medical Corps, and appointed as chief of the MED's Medical Section and Groves' medical advisor. Warren's initial task was to staff hospitals at Oak Ridge, Richland and Los Alamos. The Medical Section was responsible for medical research, but also for the MED's health and safety programs. This presented an enormous challenge, because workers were handling a variety of toxic chemicals, using hazardous liquids and gases under high pressures, working with high voltages, and performing experiments involving explosives, not to mention the largely unknown dangers presented by radioactivity and handling fissile materials. Yet in December 1945, the National Safety Council presented the Manhattan Project with the Award of Honor for Distinguished Service to Safety in recognition of its safety record. Between January 1943 and June 1945, there were 62 fatalities and 3,879 disabling injuries—about 62 percent below the rate of private industry.


Secrecy

The Manhattan Project operated under a mandate of "absolute secrecy" from Roosevelt, meaning that the very existence of the project itself was to be kept secret. This proved a daunting task given the amount of knowledge and speculation about nuclear fission that existed prior to the Manhattan Project, the huge numbers of people involved, and the scale of the facilities. Groves adopted an extreme version of Compartmentalization (information security), compartmentalization (the need-to-know policy): This clashed with the norms of many of the scientists involved, who claimed that science could not operate successfully under such requirements. The Manhattan Project officials also had difficulty with journalists, Congressmen, federal officials who were not "in the know", residents near local sites, judges adjudicating land claims, and other sources of speculation, prying, and leaks, along with concerns about espionage and sabotage. Groves relied on the FBI and his own autonomous G-2 (intelligence), G-2 intelligence unit to investigate potential security violations. Ultimately over 1,500 "loose talk" cases were investigated during the war. Because of its relative success at keeping the story out of newspapers, Byron Price, head of the Office of Censorship, ultimately designated the Manhattan Project "the best-kept secret of the war". In 1945 ''Life (magazine), Life'' estimated that before the Hiroshima and Nagasaki bombings "probably no more than a few dozen men in the entire country knew the full meaning of the Manhattan Project, and perhaps only a thousand others even were aware that work on atoms was involved." The magazine wrote that the more than 100,000 others employed with the project "worked like moles in the dark". Warned that disclosing the project's secrets was punishable by 10 years in prison or a fine of , they monitored "dials and switches while behind thick concrete walls mysterious reactions took place" without knowing the purpose of their jobs. In December 1945 the US Army published a secret report assessing the security apparatus surrounding the Manhattan Project. The report states that the project was "more drastically guarded than any other highly secret war development." The surrounding security infrastructure was so vast and thorough that in the early days of the project in 1943, investigators vetted 400,000 potential employees and 600 companies for potential security risks.


Censorship

Voluntary censorship of atomic information began before the Manhattan Project. After the start of the European war in 1939 American scientists began avoiding publishing military-related research, and in 1940 scientific journals began asking the National Academy of Sciences to clear articles. William L. Laurence of ''The New York Times'', who wrote an article on atomic fission in ''The Saturday Evening Post'' of 7 September 1940, later learned that government officials asked librarians nationwide in 1943 to withdraw the issue. The Soviets noticed the silence, however. In April 1942 nuclear physicist Georgy Flyorov wrote to Joseph Stalin on the absence of articles on nuclear fission in American journals; this resulted in the Soviet Union establishing its own atomic bomb project. The Manhattan Project operated under tight security lest its discovery induce Axis powers, especially Germany, to accelerate their own nuclear projects or undertake covert operations against the project. The Office of Censorship relied on the press to comply with a voluntary code of conduct it published, and the project at first avoided notifying the office. By early 1943 newspapers began publishing reports of large construction in Tennessee and Washington, and the office began discussing with the project how to maintain secrecy. In June it asked newspapers and broadcasters to avoid discussing "atom smashing, atomic energy, atomic fission, atomic splitting, or any of their equivalents. The use for military purposes of radium or radioactive materials, heavy water, high voltage discharge equipment, cyclotrons."


Soviet spies

The prospect of sabotage was always present, and sometimes suspected when there were equipment failures. While there were some problems believed to be the result of careless or disgruntled employees, there were no confirmed instances of Axis-instigated sabotage. However, on 10 March 1945, a Japanese fire balloon struck a power line, and the resulting power surge caused the three reactors at Hanford to be temporarily shut down. With so many people involved, security was difficult. A special Counter Intelligence Corps detachment was formed to handle the project's security issues. By 1943, it was clear that the Soviet Union was attempting to penetrate the project. Lieutenant Colonel Boris T. Pash, the head of the Counter Intelligence Branch of the Western Defense Command, investigated suspected Soviet espionage at the Radiation Laboratory in Berkeley. Oppenheimer informed Pash that he had been approached by a fellow professor at Berkeley, Haakon Chevalier, about passing information to the Soviet Union. The most successful Soviet spy was
Klaus Fuchs Klaus Emil Julius Fuchs (29 December 1911 – 28 January 1988) was a German theoretical physicist and atomic spy who supplied information from the American, British, and Canadian Manhattan Project to the Soviet Union during and shortly a ...
, a physicist and member of the British Mission who was intimately involved in work at Los Alamos on the design of the implosion bomb. His espionage activities were not identified until 1950, as a result of Venona project. The revelation of his espionage activities damaged the United States' nuclear cooperation with Britain and Canada, and other instances of espionage were subsequently uncovered, leading to the arrest of Harry Gold, David Greenglass, and Julius and Ethel Rosenberg. Other spies like George Koval and Theodore Hall remained unknown for decades. The value of the espionage is difficult to quantify, as the principal constraint on the Soviet atomic bomb project was their short supply of uranium ore. It may have saved the Soviets at least one or two years in the development of their own bomb, although some historians have argued the Soviets spent as much time vetting and reduplicating the information as they would have saved had they trusted it.


Foreign intelligence

In addition to developing the atomic bomb, the Manhattan Project was charged with gathering intelligence on the German nuclear energy project. It was believed that the Japanese nuclear weapons program was not far advanced because Japan had little access to uranium ore, but it was initially feared that Germany was very close to developing its own weapons. At the instigation of the Manhattan Project, a Norwegian heavy water sabotage, bombing and sabotage campaign was carried out against heavy water plants in German-occupied Norway. A small mission was created, jointly staffed by the Office of Naval Intelligence, OSRD, the Manhattan Project, and Army Intelligence (G-2), to investigate enemy scientific developments. It was not restricted to those involving nuclear weapons. The Chief of Army Intelligence, Major General George V. Strong, appointed Boris Pash to command the unit, which was codenamed "Alsos" (Greek for "grove"). Samuel Goudsmit was the scientific director of the Alsos mission. The Alsos Mission to Italy questioned physics laboratory staff at the Sapienza University of Rome, University of Rome following the capture of the city in June 1944. Meanwhile, Pash formed a combined British and American Alsos mission in London under the command of Captain Horace K. Calvert to participate in Operation Overlord. Groves considered the risk that the Germans might attempt to disrupt the Normandy landings with radioactive poisons was sufficient to warn General Dwight D. Eisenhower and send an officer to brief his chief of staff, Lieutenant General Walter Bedell Smith. Under the codename Operation Peppermint, special equipment was prepared and Chemical Warfare Service teams were trained in its use. Following in the wake of the advancing Allied armies, the Alsos team interrogated scientists and searched facilities in liberated areas of France and Germany to learn about the German work. Goudsmit concluded in November 1944 that the German nuclear program had never made it beyond the laboratory stage. As he put it later: "The evidence at hand proved definitely that Germany had no atom bomb and was not likely to have one in any reasonable time." Interrogation of German prisoners indicated that uranium and thorium were being processed in Oranienburg, so Groves Auergesellschaft#Russian Alsos, arranged for it to be bombed on 15 March 1945 to deny its capture by the Soviet Union. An Alsos team went to Stassfurt in the Soviet Occupation Zone and retrieved 11 tons of ore from WIFO (Nazi company), WIFO. In April 1945, Pash, in command of a composite force known as T-Force, conducted Operation Harborage, a sweep behind enemy lines of Hechingen, Bisingen, and Haigerloch—the heart of the German nuclear effort. T-Force captured nuclear laboratories, documents, equipment and supplies, including heavy water and 1.5 tons of metallic uranium. Alsos teams rounded up German scientists including Kurt Diebner,
Otto Hahn Otto Hahn (; 8 March 1879 – 28 July 1968) was a German chemist who was a pioneer in the field of radiochemistry. He is referred to as the father of nuclear chemistry and discoverer of nuclear fission, the science behind nuclear reactors and ...
, Walther Gerlach, Werner Heisenberg, and Carl Friedrich von Weizsäcker. They were taken to England and interned at Farm Hall, where they were surreptitiously surveilled.


Atomic bombings of Hiroshima and Nagasaki


Preparations

The only Allied aircraft capable of carrying the long Thin Man or the wide Fat Man was the British Avro Lancaster, but using a British aircraft would have caused difficulties with maintenance. Groves hoped that the American Boeing B-29 Superfortress could be modified to carry a Thin Man by joining its two bomb bays together. This became unnecessary after Thin Man was abandoned, as a Little Boy was short enough to fit into a B-29 bomb bay, but modifications were still required. The Air Force Materiel Command, Army Air Forces Materiel Command at Wright Field, Ohio, began Silverplate, the codename for the modification of the B-29, in November 1943. Test drops were carried out at Muroc Army Air Field and the Naval Ordnance Test Station in California with Thin Man and Fat Man pumpkin bombs to test their ballistic, fuzing and stability characteristics. The 509th Composite Group was activated on 17 December 1944 at Wendover Army Air Field, Utah, under the command of Colonel Paul W. Tibbets. Its 393rd Bombardment Squadron, equipped with Silverplate B-29s, practiced long-distance flights over water and dropped pumpkin bombs. A special unit known as Project Alberta was formed at Los Alamos under Parsons's command to assist in preparing and delivering the bombs. The 509th Composite Group deployed to North Field (Tinian), North Field on Tinian in July 1945. Most of the components for the Little Boy left San Francisco on the cruiser on 16 July and arrived on Tinian on 26 July. The remaining components, which included six highly enriched uranium rings, were delivered by three Douglas C-54 Skymasters of the 509th Group's 320th Troop Carrier Squadron. Two Fat Man assemblies traveled to Tinian in specially modified 509th Composite Group B-29s, and the first plutonium core went in a special C-54. At the end of December 1944, worried by the heavy losses occurring in the Battle of the Bulge, Roosevelt instructed Groves and Stimson that if the atomic bombs were ready before the war with Germany ended, they should be ready to drop them on Germany, but Japan was regarded as more likely. In late April 1945, a targeting committee was established to determine which cities should be targets, and it recommended Kokura, Hiroshima, Niigata (city), Niigata, and Kyoto. Stimson intervened, announcing that he would be making the targeting decision, and that he would not authorize the bombing of Kyoto on the grounds of its historical and religious significance. Nagasaki was ultimately substituted. In May 1945, the Interim Committee was created to advise on wartime and postwar use of nuclear energy. The Interim Committee in turn established a scientific panel consisting of Arthur Compton, Fermi, Lawrence, and Oppenheimer; the scientific panel offered its opinion not just on the likely physical effects of an atomic bomb, but on its probable military and political impact. In a meeting on 1 June, the Interim Committee resolved that "the bomb should be used against Japan as soon as possible; that it be used on a war plant surrounded by workers' homes; and that it be used without prior warning". At the Potsdam Conference in Germany, President Harry S. Truman told Stalin that the US had "a new weapon of unusual destructive force", without giving any details. As he showed "no special interest," Truman erroneously assumed that Stalin did not understand. In reality, Soviet spies had kept Stalin informed of the work and the planned test. A strike order from General Thomas T. Handy to General Carl Spaatz was approved by Marshall and Stimson on 25 July which specified that the "first special bomb" be used "after about 3 August 1945," and that "additional bombs" would be used "as soon as made ready by the project staff". The operational plan was to drop the first bomb on 2 August, the second bomb on 10 August, and a third bomb around 24 August. However, due to weather conditions over Japan and the desire for visual bombing, the date of the first bombing mission was pushed back to 6 August, and the second was moved forward to 9 August.


Bombings

On 6 August 1945, the ''Enola Gay'', a Boeing B-29 Superfortress of the 393d Bombardment Squadron, piloted by Tibbets, lifted off from North Field with a Little Boy in its bomb bay. Hiroshima, the headquarters of the 2nd General Army and 5th Division (Imperial Japanese Army), Fifth Division and a port of embarkation, was the primary target, with Kokura and Nagasaki as alternatives. Parsons, the weaponeer in charge of the mission, completed the bomb assembly in the air to minimize the risks of a nuclear explosion in the event of a crash during takeoff. The bomb detonated at an altitude of with a blast that was later estimated to be the equivalent of 13 kilotons of TNT. An area of approximately was destroyed. Japanese officials determined that 69% of Hiroshima's buildings were destroyed and another 6–7% damaged. Early estimates were that 66,000 people were killed and 69,000 injured; later re-estimations that included people ignored by previous methods, like Korean slave laborers and additional soldiers, concluded there might have been 140,000 dead from the attack by December 1945. On the morning of 9 August 1945, the ''Bockscar'', a second B-29 piloted by the 393d Bombardment Squadron's commander, Major Charles W. Sweeney, lifted off with a Fat Man on board. This time, Ashworth served as weaponeer and Kokura was the primary target. When they reached Kokura, they found cloud cover had obscured the city, prohibiting the visual attack required by orders. After three runs and with fuel running low, they headed for the secondary target, Nagasaki. Ashworth decided that a radar approach would be used if the target was obscured, but a last-minute break in the clouds over Nagasaki allowed a visual approach as ordered. The Fat Man was dropped over the city's industrial valley midway between the Mitsubishi Steel and Arms Works in the south and the Mitsubishi-Urakami Ordnance Works in the north. The resulting explosion had a blast yield equivalent to 21 kilotons of TNT, roughly the same as the Trinity blast, but was confined to the Urakami Valley, and a major portion of the city, including the city center, was protected by the intervening hills. About 44% of the city was destroyed, and estimates of casualties range from 40,000 to 80,000 people killed and at least 60,000 injured. Overall, an estimated 35,000–40,000 people were killed and 60,000 injured. Groves expected to have another atomic bomb ready for use on 19 August, with three more in September and a further three in October. Two more Fat Man assemblies were readied, and scheduled to leave Kirtland Air Force Base, Kirtland Field for Tinian on 11 and 14 August. At Los Alamos, technicians worked 24 hours straight to cast Demon core, another plutonium core. Although cast, it still needed to be pressed and coated, which would take until 16 August. It could therefore have been ready for use on 19 August. On 10 August, Truman was informed that another bomb was being prepared. He ordered that no additional atomic bombs could be used without his express authority. According to
Henry A. Wallace Henry Agard Wallace (October 7, 1888 – November 18, 1965) was the 33rd vice president of the United States, serving from 1941 to 1945, under President Franklin D. Roosevelt. He served as the 11th U.S. secretary of agriculture and the 10th U.S ...
, Truman told his cabinet that "the thought of wiping out another 100,000 people was too horrible. He didn't like the idea of killing, as he said, 'all those kids.'" Groves suspended the third core's shipment on 13 August. On 11 August, Groves phoned Warren with orders to organize a survey team to report on the damage and radioactivity at Hiroshima and Nagasaki as soon as the war ended. A party equipped with portable Geiger counters arrived in Hiroshima on 8 September headed by Farrell and Warren, with Japanese Rear Admiral Masao Tsuzuki, who acted as a translator. They remained in Hiroshima until 14 September and then surveyed Nagasaki from 19 September to 8 October. This and other scientific missions to Japan provided valuable data on the effects of the atomic bomb, and led to the creation of the Atomic Bomb Casualty Commission. In anticipation of the bombings, Groves had commissioned physicist Henry DeWolf Smyth to prepare a sanitized technical history of the project for public consumption. The idea of releasing such information freely was controversial; the decision to do so was made by Truman personally. The "Smyth Report" was released to the public on 12 August 1945. Surrender of Japan, Japan announced its surrender on 15 August. The necessity of the bombings became a debate over the atomic bombings of Hiroshima and Nagasaki, subject of controversy among historians. Some questioned whether "atomic diplomacy" would have attained the same goals, and the relative weight that the bombs and the Soviet–Japanese War (1945), Soviet declaration of war had on the Japanese willingness to surrender. The Franck Report was the most notable effort pushing for a demonstration but was turned down by the Interim Committee's scientific panel. The Szilárd petition, drafted in July 1945 and signed by dozens of scientists working on the Manhattan Project, was a late attempt at warning Truman about his responsibility in using such weapons.


After the war

The Manhattan Project became instantly famous after the bombing of Hiroshima and the partial lifting of its secrecy. It was widely credited with ending the war, and Groves worked to credit its contractors, whose work had hitherto been secret. Groves and Nichols presented them with Army–Navy "E" Awards, and over 20 Presidential Medal for Merit, Presidential Medals for Merit were awarded to key contractors and scientists, including Bush and Oppenheimer. Military personnel received the Legion of Merit. The Manhattan Project persisted until 31 December 1946, and the Manhattan District to 15 August 1947. During this time, it suffered from numerous difficulties caused by technical problems, the effects of rapid demobilization, and a lack of clarity on its long-term mission. At Hanford, plutonium production declined as Reactors B, D and F wore out, poisoned by fission products and swelling of the graphite moderator known as the Wigner effect. The swelling damaged the charging tubes where the uranium was irradiated to produce plutonium, rendering them unusable. Production was curtailed and the oldest unit, B pile, was closed down so at least one reactor would remain available. Research continued, with DuPont and the Metallurgical Laboratory developing a redox solvent extraction process as an alternative nuclear reprocessing, plutonium extraction technique to the bismuth phosphate process, which left unspent uranium in a state from which it could not easily be recovered.. Bomb engineering was carried out by the Z Division, initially located at Wendover Field but moved to Oxnard Field, New Mexico, in September 1945 to be closer to Los Alamos. This marked the beginning of the Sandia Base. Nearby Kirtland Field was used as a B-29 base for aircraft compatibility and drop tests. As reservist officers were demobilized, they were replaced by about fifty hand-picked regular officers. Nichols recommended that S-50 and the Alpha tracks at Y-12 be closed down. This was done in September. Although performing better than ever, the Alpha tracks could not compete with K-25 and the new K-27, which had commenced operation in January 1946. In December, the Y-12 plant was closed, cutting the Tennessee Eastman payroll from 8,600 to 1,500 and saving $2 million a month. Nowhere was demobilization more of a problem than at Los Alamos, where there was an exodus of talent. Much remained to be done. The bombs used on Hiroshima and Nagasaki needed work to make them simpler, safer and more reliable. Implosion methods needed to be developed for uranium in place of the wasteful gun method, and composite uranium-plutonium cores were needed now that plutonium was in short supply. However, uncertainty about the future of the laboratory made it hard to induce people to stay. Oppenheimer returned to his job at the University of California and Groves appointed Norris Bradbury as an interim replacement; Bradbury remained in the post for the next 25 years.. Groves attempted to combat the dissatisfaction caused by the lack of amenities with a construction program that included an improved water supply, three hundred houses, and recreation facilities. Manhattan Project personnel participated in the first postwar nuclear tests,
Operation Crossroads Operation Crossroads was a pair of nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. They were the first nuclear weapon tests since Trinity on July 16, 1945, and the first detonations of nuclear devices sinc ...
, conducted at
Bikini Atoll Bikini Atoll ( or ; Marshallese language, Marshallese: , , ), known as Eschscholtz Atoll between the 19th century and 1946, is a coral reef in the Marshall Islands consisting of 23 islands surrounding a central lagoon. The atoll is at the no ...
in July 1946. Two Fat Man-type bombs were detonated — one as an airburst, one as an underwater burst — to investigate the effect of nuclear weapons on warships. Press and international observers were allowed to attend, making the tests an international spectacle. Following a domestic debate over the peacetime management of the nuclear program, the Atomic Energy Act of 1946 created the
United States Atomic Energy Commission The United States Atomic Energy Commission (AEC) was an agency of the United States government established after World War II by the U.S. Congress to foster and control the peacetime development of atomic science and technology. President Harry ...
to take over the project's functions and assets. It established civilian control over atomic development. Military aspects were taken over by the Armed Forces Special Weapons Project (AFSWP). After the bombings at Hiroshima and Nagasaki, a number of Manhattan Project physicists founded the ''Bulletin of the Atomic Scientists'' (1945) and Emergency Committee of Atomic Scientists (1946), which began as an emergency action undertaken by scientists who saw urgent need for an educational program about atomic weapons. In the face of the destructiveness of the bombs and in anticipation of the nuclear arms race several project members including Bohr, Bush and Conant expressed the view that it was necessary to reach agreement on International control of atomic energy, international control of nuclear research and atomic weapons. The Baruch Plan, unveiled in a speech to the newly formed United Nations Atomic Energy Commission (UNAEC) in June 1946, proposed the establishment of an international atomic development authority, but was not adopted.


Cost

The project expenditure through 1 October 1945 was $1.845 billion, equivalent to less than nine days of wartime spending, and was $2.191 billion when the AEC assumed control on 1 January 1947. The total allocation was $2.4 billion. 84% of the costs through the end of 1945 were spent on the plants at Oak Ridge and Hanford, producing the enriched uranium and plutonium needed to fuel the bombs. At both sites, the majority of the costs were for construction (74% at Oak Ridge, 87% at Hanford), with the rest being for operations. Initial funding for the project was through the general budget of the
Office of Scientific Research and Development The Office of Scientific Research and Development (OSRD) was an agency of the United States federal government created to coordinate scientific research for military purposes during World War II. Arrangements were made for its creation during May ...
. As plans were made to turn the work over to the Army Corps of Engineers, Bush wrote to Roosevelt in late 1942 that "it would be ruinous to the essential secrecy to have to defend before an appropriations committee any request for funds for this project." Instead, initial funding was done through black budget, discretionary funds to which Roosevelt had access. As it grew in size and cost, Congress was deliberately kept ignorant of the project, because of concerns that Congressmen were prone to leaking information, and because it was feared that the project would appear to be a boondoggle. Appropriations requests were quietly slipped into other bills, but the project's mounting costs and large facilities (which appeared to many to produce nothing) attracted scrutiny from several Congressional auditors. The Truman Committee that investigated wartime waste and fraud attempted to audit the project several times, but each time their inquiries were rejected. These Congressional inquiries, along with the need for smooth budgetary approval, led to Bush, Groves, and Stimson agreeing in the spring of 1944 that a few high-ranking Congressmen should be told of the project's purpose. By March 1945, exactly seven Congressmen were officially informed. The funds were hidden into appropriation requests with the inconspicuous headings, frequently "Engineer Service Army" and "Expediting Production." In late May 1945, to further expedite budget issues and assure the cooperation of Albert J. Engel, who had threatened to reveal the existence of the project if he was not told more about it, five additional Congressmen were permitted to visit the Oak Ridge site to assure themselves of "the reasonableness of the various living accommodations which had been provided, [and] that they actually observe the size and scope of the installations and that some of the complexities of the project be demonstrated to them." During the war, the Manhattan Project ultimately produced the three bombs used (the Trinity gadget, Little Boy, and Fat Man), as well as Third Shot, an additional unused Fat Man bomb, making the average wartime cost per bomb around $500 million in 1945 dollars. By comparison, the project's total cost by the end of 1945 was about 90% of the total spent on the production of US small arms (not including ammunition) and 34% of the total spent on US tanks during the same period. It was the second most expensive weapons project undertaken by the United States during the war, behind only the Boeing B-29 Superfortress.


Legacy

The political and cultural impacts of the development of nuclear weapons were profound. William Laurence of ''The New York Times'', the first to use the phrase "Atomic Age", became the official correspondent for the Manhattan Project in spring 1945. He witnessed both the Trinity test and the bombing of Nagasaki and wrote the official press releases on them. He went on to write a series of articles extolling the virtues of the new weapon. His reporting helped to spur public awareness of the potential of nuclear technology and motivated its development in the United States and Soviet Union. The Manhattan Project left a legacy of a network of United States Department of Energy national laboratories, national laboratories: the Lawrence Berkeley National Laboratory, Los Alamos National Laboratory, Oak Ridge National Laboratory,
Argonne National Laboratory Argonne National Laboratory is a Federally funded research and development centers, federally funded research and development center in Lemont, Illinois, Lemont, Illinois, United States. Founded in 1946, the laboratory is owned by the United Sta ...
, and Ames Laboratory. Two more were established by Groves soon after the war, the Brookhaven National Laboratory at Upton, New York, and the Sandia National Laboratories at Albuquerque, New Mexico. They would be in the vanguard of the kind of large-scale research that Alvin Weinberg, the director of the Oak Ridge National Laboratory, would call Big Science. Computational science, especially computational engineering, was influenced by the Manhattan Project; Los Alamos ran one of the most advanced tabulating machine facilities in the world. The Naval Research Laboratory had long been interested in the prospect of using nuclear power for warship propulsion, and sought to create its own nuclear project. In May 1946, Nimitz, now Chief of Naval Operations, decided that the Navy should instead work with the Manhattan Project. A group of naval officers were assigned to Oak Ridge, the most senior of whom was Captain Hyman G. Rickover, who became assistant director there. They immersed themselves in the study of nuclear energy, laying the foundations for a nuclear navy, nuclear-powered navy. A similar group of Air Force personnel arrived at Oak Ridge in September 1946 with the aim of developing nuclear aircraft. Their Aircraft Nuclear Propulsion, Nuclear Energy for the Propulsion of Aircraft project ran into formidable technical difficulties and was ultimately canceled. The ability of the new reactors to create radioactive isotopes in previously unheard-of quantities sparked a revolution in nuclear medicine. Starting in mid-1946, Oak Ridge began distributing radioisotopes to hospitals and universities, primarily iodine-131 and phosphorus-32 for cancer diagnosis and treatment. Isotopes were also used in biological, industrial and agricultural research. Its production sites, operating with new technologies, exotic substances, and under conditions of secrecy and haste, also left a vast legacy of waste and environmental damage. At Hanford, for example, corrosive and radioactive wastes were stored in "hastily fabricated, single-shell, steel-lined, underground storage tanks" that were intended to be temporary, awaiting a more permanent solution. Instead, they were neglected and eventually leaked. Issues of this kind resulted in Hanford becoming "one of the most contaminated nuclear waste sites in North America", and the subject of significant cleanup efforts after it was deactivated in the late Cold War. On handing over control to the Atomic Energy Commission, Groves bid farewell to the people who had worked on the Manhattan Project: The Manhattan Project National Historical Park was established on 10 November 2015.


See also

* * Oppenheimer (TV series) - 1980 TV miniseries * Fat Man and Little Boy (film) - 1989 film starring Paul Newman * Oppenheimer (film) - 2023 film by Christopher Nolan starring Cillian Murphy * Timeline of nuclear weapons development


Notes


Citations


References

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Technical histories

* * * (1967 interview with Groves) * * * * * * * * * * (Available on commons:File:Los Alamos Primer.pdf, Wikimedia Commons) * * * *


Participant accounts

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External links

* * * — Features hundreds of audio/visual interviews with Manhattan Project veterans. * *
Manhattan Project and Allied Scientists Collections
at th
University of Chicago Special Collections Research Center
* {{Authority control Manhattan Project, 1942 establishments in the United States 1946 disestablishments in the United States American secret government programs Atomic bombings of Hiroshima and Nagasaki Explosives engineering History of the Manhattan Project Military history of Canada during World War II Military history of the United Kingdom during World War II Military history of the United States during World War II Nuclear history of the United States Nuclear weapons program of the United States Projects established in 1942 Secret military programs