Manhattan project
The Manhattan Project (in English: Manhattan Project) was a research and development project carried out during World War II that produced the first nuclear weapons, led by by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project was directed by Major General Leslie Groves of the United States Army Corps of Engineers, while nuclear physicist Robert Oppenheimer was the director of the Los Alamos National Laboratory, where the the nuclear bombs themselves. The military unit participating in the project received the designation Manhattan District (in English: Manhattan District), a name that gradually replaced the official code name, Development of Substitute Materials (in English: Development of Substitute Materials). In its course the project absorbed its previous British equivalent, the Tube Alloys project. The Manhattan Project started modestly, growing progressively to over 130,000 employees and reaching a cost of nearly $2 billion. Over 90% of the budget went to building factories and producing fissile materials, with Less than 10% earmarked for weapons development and production. Research and production took place at more than 30 locations throughout the United States, United Kingdom, and Canada.
Two types of atomic bombs were developed simultaneously during the war: a relatively simple ballistic fission weapon and a more complex implosion nuclear weapon. The fission design of the Thin Man bomb proved impractical for use with plutonium, so a simpler weapon called the Little Boy was developed using uranium-235., an isotope that makes up only 0.7% of uranium in its natural state. Project workers had difficulty separating this isotope from uranium-238 because of its chemical and mass similarities. Three methods were used for uranium enrichment: the use of calutrons, gaseous diffusion and thermophoresis. Most of this work was carried out at the Clinton Engineer Works facilities in Oak Ridge (Tennessee).
Parallel to the uranium research, the project continued work on plutonium production. After the feasibility of the world's first artificial nuclear reactor was demonstrated in Chicago at the Metallurgical Laboratory, the X-10 graphite reactor was designed at Oak Ridge and the production reactors at the Hanford Engineer Works facility, where uranium was irradiated and transmuted into plutonium, to later chemically separate the plutonium from the uranium. The Fat Man implosion nuclear weapon was developed through concerted design and development at the Los Alamos laboratory.
The project also performed counterintelligence work on the German nuclear weapons program. Through Operation Alsos, several members of the Manhattan Project served in Europe, sometimes behind enemy lines, seizing nuclear materials and documentation and transporting German scientists to Allied countries. Moreover, despite the tight security of the project, several Soviet "atom spies" managed to infiltrate the program.
The first nuclear device detonated was a bomb from the Trinity test implosion, conducted at the Alamogordo bombing and firing range on July 16, 1945. Two other Little Boy type bombs and Fat Man were used respectively a month later in the atomic bombings of Hiroshima and Nagasaki. In the immediate post-war years, the Manhattan Project conducted various weapons tests on Bikini Atoll as part of Operation Crossroads, developed new weapons, promoted the development of the national laboratory network, supported medical research on radiology and laid the foundations for nuclear weapons. The project maintained control over American nuclear weapons research and production until the formation of the United States Atomic Energy Commission in January 1947.
Origin
The discovery of nuclear fission by German chemists Otto Hahn and Fritz Strassmann in 1938, along with its theoretical explanation by Lise Meitner and Otto Robert Frisch, made the development of an atomic bomb a theoretical possibility.. It was feared that the Germans would be the first to develop one of these bombs through their own project, especially by refugee scientists from Nazi Germany and other fascist countries. In August 1939, Hungarian-born physicists Leó Szilárd and Eugene Wigner wrote the Einstein-Szilárd letter, warning of the potential development of "extremely powerful bombs of a new class." In it they urged the United States to take steps to acquire uranium ore reserves and speed up research by Enrico Fermi and other scientists into nuclear chain reactions. Albert Einstein signed this letter, which was delivered to President Franklin D. Roosevelt. Roosevelt asked Lyman Briggs of the National Standards Institute to lead the Uranium Advisory Committee to investigate the issues noted in this letter. Briggs arranged a meeting on October 21, 1939, which was attended by Szilárd, Wigner, and Edward Teller. The committee informed Roosevelt in November that the uranium would "provide a possible source of bombs with a far greater destructive capacity than any previously known."
The Uranium Advisory Committee became the National Defense Research Committee (NDRC) on June 27, 1940. Briggs proposed spending $167 $000 for uranium research, particularly the uranium-235 isotope, and the newly discovered plutonium. On June 28, 1941, Roosevelt signed Executive Order 8807, creating the Office of Scientific Research and Development (in English: Office of Scientific Research and Development, OSRD) with Vannevar Bush serving as director. This office had the power to pursue large engineering projects in addition to research. The Uranium Committee became the S-1 section of the OSRD, dropping the word "uranium" from the name for security reasons.
In June 1939 in the UK, Frisch and Rudolf Peierls of the University of Birmingham had made significant progress in investigating the critical mass of uranium-235. Their calculations indicated that the critical mass would be within the order of magnitude of 10 kg (22 lb), an amount small enough to carry loaded on a bomber. His Frisch-Peierls memorandum of March 1940 initiated the British atomic project and its MAUD Committee, which unanimously recommended pursuing further development. of an atomic bomb. In July 1940 the United Kingdom offered the United States access to its scientific research and John Cockcroft was commissioned to inform American scientists about British developments, as part of the Tizard Mission. Cockcroft then learned that the American project was smaller than the British one and not as advanced.
As part of the scientific exchange, the findings of the MAUD Committee were conveyed to the United States. One of its members, the Australian physicist Mark Oliphant, flew to the United States in late August 1941 and learned that the data supplied by the committee had not reached a number of leading American scientists. Oliphant sought to understand why these discoveries were apparently being ignored. He met with the S-1 section of the OSRD and visited Berkeley, California, speaking persuasively with Ernest Lawrence. Lawrence was impressed enough to start his own uranium research. Oliphant continued to meet with other researchers, including James B. Conant, Arthur Compton, and George B. Pegram, thus making leading American physicists aware of the potential of atomic bombs.
On October 9, 1941, President Roosevelt approved the atomic program after a meeting with Vannevar Bush and Vice President Henry A. Wallace. To control the program, he created a Senior Political Group consisting of himself—although he never attended any of their meetings—Wallace, Bush, Conant, Secretary of War Henry L. Stimson, and Army Chief of Staff George C. Marshall. Roosevelt selected the Army to lead the project over the Navy since the Army had more experience handling large-scale construction projects. He also agreed to coordinate work with the British, sending a message to Prime Minister Winston Churchill on October 11, 1941, in which he suggested that they agreed on atomic issues.
Viability
Proposals
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The S-1 Committee held a meeting on December 18, 1941 "permeated with an atmosphere of enthusiasm and urgency" following the attack on Pearl Harbor and the subsequent declaration of war by the United States on Japan and Germany. There was ongoing research on three isotope separation techniques to separate uranium-235 from the more abundant uranium-238. Lawrence and his team at the University of California investigated electromagnetic separation, while the team of Eger Murphree and Jesse Wakefield Beams investigated gaseous diffusion at Columbia University, and Philip Abelson led research on thermal diffusion at the Carnegie Institution of Washington. D.C. and later at the Naval Research Laboratory. Murphree also led another unsuccessful separation research project, using a gas centrifuge.
At the same time there were two lines of research underway for nuclear reactor technology, with Harold Urey continuing heavy water research at Columbia, while Arthur Compton brought together the scientists working under his supervision from Columbia, California, and Princeton University in his team at the University of Chicago, where he organized the Metallurgical Laboratory in early 1942 to study plutonium and reactors using graphite as a neutron moderator. Briggs, Compton, Lawrence, Murphree, and Urey met on May 23, 1942 to finalize the recommendations of the S-1 Committee, urging pursuit of the five technologies. The proposed measures were approved by Bush, Conant, and Brigadier General Wilhelm D. Styer, Chief of Staff of Supply Services to Major General Brehon B. Somervell, who had been designated the Army's representative on nuclear affairs. Bush and Conant took the recommendations to the Senior Policy Group with a proposed budget of $54 million for construction by the US Army Corps of Engineers, $31 million for research and development for OSRD, and $5 million for of dollars for contingencies in the fiscal year of 1943. The Group sent this proposal to the president on June 17, 1942, and it was finally approved.
Pump Design Concepts
Compton asked theoretical physicist Robert Oppenheimer of the University of California to take over the research on fast neutron calculations—which were the key to the critical mass and weapons detonation calculations. — by Gregory Breit, who had resigned on May 18, 1942, concerned about lax operational security. John H. Manley, one of the physicists at the Metallurgical Laboratory, was tasked with assisting Oppenheimer by contacting and coordinating groups of experimental physicists scattered throughout throughout the country. Oppenheimer and Robert Serber of the University of Illinois examined the problems of neutron diffusion—how neutrons move in a nuclear chain reaction—and hydrodynamics—how the explosion produced by the reaction would behave. in chain- To review this work and the general theory of fission reactions, Oppenheimer and Enrico Fermi held several meetings at the University of Chicago in June and at the University of California in July, together with theoretical physicists Hans Bethe, John Van Vleck, Edward Teller, Emil Konopinski, Robert Serber, Stan Frankel and Eldred C. Nelson, the last three former students of Oppenheimer himself, and with the experimental physicists Emilio Segrè, Felix Bloch, Franco Rasetti, John Henry Manley and Edwin McMillan. The group tentatively confirmed that a fission bomb was theoretically possible.
However, many factors remained unknown to scientists. The properties of pure uranium-235 were relatively unknown, as were those of plutonium, an element that had been discovered in February 1941 by Glenn Seaborg and his team. Scientists at the Berkeley conference had a vision of creating plutonium in nuclear reactors where uranium-238 atoms would absorb neutrons emitted from the fission of uranium-235 atoms. At that time no reactor had yet been built and only small amounts of plutonium obtained by means of a cyclotron were available. By December 1943 only 2 mg of this element had been produced. The simplest way to carry fissile material even a critical mass was to shoot a "cylindrical plug" into a sphere of "active material" with a "lock", a dense material that would focus neutrons inward and hold the reactive mass together to increase its efficiency. They also explored spheroid designs, a primitive form of "implosion" suggested by Richard C. Tolman, as well as the possibility of carrying out autocatalytic methods that would increase the efficiency of the bomb during its explosion.
Considering that the fission bomb idea was theoretically settled, at least until more experimental data was obtained, the Berkeley conference veered in a new direction. Edward Teller promoted the debate about a more powerful bomb, the so-called "super", later known as a "hydrogen bomb", which would use the explosive force of a fission bomb detonation to start a nuclear fusion reaction of deuterium and tritium. Teller proposed various schemes, all of which were rejected by Bethe, and the idea of fusion was set aside to concentrate on the production of fission bombs. Teller also noted the speculative possibility that an atomic bomb could "ignite" the atmosphere at caused by a hypothetical fusion reaction of nitrogen nuclei. Bethe calculated that this could not happen, and in a report co-authored by Teller they showed that "there is no potential for it to initiate a self-propagating nuclear chain reaction". In Serber's words, Oppenheimer mentioned this to Arthur Compton, who "didn't have enough common sense to keep quiet about it...somehow he ended up in a document that was sent to Washington", and "the matter was never put to rest".
Organization
Manhattan District
In June 1942, the Chief of Engineers, Major General Eugene Reybold, chose Colonel James C. Marshall to lead the Army portion of the project. Marshall created a liaison office in Washington, D.C., although he established his headquarters at 270 18th Broadway in New York, from where he could receive administrative support from the North Atlantic Division of the Corps of Engineers. It was also close to the Manhattan office of Stone & Webster, the main contractor on the project, and Columbia University. He also had permission to transfer personnel from his previous command, the Syracuse District, and began by recruiting Lt. Col. Kenneth Nichols, who happened to be second to him.
Since much of the project involved construction, Marshall worked cooperatively with the head of the Construction Division of the Corps of Engineers, Major General Thomas M. Robbins, and his deputy, Colonel Leslie Groves. Eugene Reybold, Brehon B. Somervell, and Wilhelm D. Styer decided to call the project "Development of Substitute Materials," but Groves felt that this name would attract too much attention. Since engineering districts were often named after the city in which they were located, Marshall and Groves agreed to name the Army section of this project the Manhattan District. This name became official on August 13 when Reybold issued an order for the creation of the new district. More informally it was also known as the Manhattan Engineering District (English: Manhattan Engineer District, MED). Unlike other districts it had no geographical boundaries and Marshall had the authority of a divisional engineer. The name Substitute Materials Development was retained as the official code name for the project as a whole, but was eventually replaced by "Manhattan".
Marshall later stated: "I had never heard of atomic fission but I did know you couldn't build a plant, let alone four of them, for $90 million." Nichols had been commissioned to build one. TNT plant shortly before in Pennsylvania at a cost of $128 million. They were also unimpressed by estimates to the nearest order of magnitude, which Groves likened to telling a caterer to prepare for ten to a thousand guests. A survey team from Stone & Webster had already scouted a location for production plants. The War Production Board recommended locations near Knoxville, Tennessee, an isolated region where the Tennessee Valley Authority could provide high electrical capacity and where rivers could supply water for reactor cooling. After examining several locations, the survey team selected one near Elza, Tennessee. Conant proposed that the land be acquired immediately, and Styer agreed, but Marshall delayed the matter awaiting the results of Conant's reactor experiments before taking action. Of all the processes on the horizon, only electronic separation of Lawrence seemed far enough along in his definition for construction to begin.
Marshall and Nichols began to gather the resources they needed. The first step was to obtain a high priority classification for the project. The highest ratings ranged from AA-1 to AA-4 in descending order, although there was also a special AAA rating reserved for emergencies. The AA-1 and AA-2 ratings were reserved for essential equipment and weaponry, so Colonel Lucius D. Clay, deputy chief of staff in the Department of Services and Supply, felt that the highest rating he could give the The project was AA-3, although he was willing to give AAA rating on request for critical materials if the need arose. Nichols and Marshall were disappointed with this, as AA-3 was the same priority that the TNT plant had been given. of Nichols in Pennsylvania.
Military Policy Committee
Vannevar Bush was dissatisfied with the slow progress of the project under Colonel Marshall and more specifically with the inability to acquire the Tennessee site, the low priority the Army had given the project, and the location of the headquarters in New York. He felt the project needed more aggressive leadership and met with Harvey Bundy and Generals Marshall, Somervell, and Styer to discuss their concerns. Bush wanted the project to be under a higher political committee, with a senior officer as CEO, preferably Styer.
Somervell and Styer chose Groves for this position, informing him of the decision and his promotion to brigadier general on 17 September, as they felt the title "general" would be more influential to academics working in the project. Groves was thus placed directly under Somervell's command instead of Reybold and with Colonel Marshall under his command. Groves established his headquarters in Washington, D.C., on the fifth floor of the New Department of Defense Building. War, where Colonel Marshall had his liaison office. He assumed command of the Manhattan Project on September 23, and that same day attended a meeting called by Stimson, at which a Bush-composed Military Policy Committee (with Conant as substitute), Styer, and Vice Admiral William R. Purnell. Tolman and Conant were later appointed as Groves' science advisors.
On September 19, Groves met with Donald Nelson, chairman of the War Production Board, asking him for greater authority to assign a AAA rating when necessary. Nelson was initially opposed to this, but agreed when Groves threatened to take the matter to the President of the US Groves promised that he would not use this classification unless absolutely necessary. However, it turned out that the AAA rating was too high for the routine requirements of the project, while the AA-3 was too low. After a long campaign, Groves was finally rated AA-1 on July 1, 1944. According to Groves: "In Washington the importance of top priority became known. Almost everything that is proposed in the Roosevelt administration would have top priority. That would last for about a week or two and then something else would take top priority".
One of Groves' first problems was finding a director for Project Y, the group that would design and build the bomb. The obvious choice for him was one of the heads of the three labs, Urey, Lawrence, or Compton, but Groves couldn't afford to move them. Compton recommended Oppenheimer, who was already familiar with bomb design concepts. However, Oppenheimer had very little administrative experience, and unlike the other three lab heads, he had not won a Nobel Prize, something many scientists felt the head of such an important lab should have. There were also concerns about Oppenheimer's security status, as many of his associates were communists, including his brother Frank Oppenheimer, his wife Kitty, and Robert's girlfriend, Jean Tatlock. Following a conversation during a train ride in October 1942, Groves and Nichols were convinced that Oppenheimer understood the challenges of setting up a laboratory in a remote area and that he should be made director. Groves personally waived the security requirements and gave Oppenheimer clearance on July 20, 1943.
Collaboration with the United Kingdom
The British and Americans exchanged nuclear information but did not initially join forces. The UK rejected attempts by Bush and Conant in 1941 to increase cooperation with their own project, codenamed Tube Alloys, as they were unwilling to share their technological lead in helping the US develop its own atomic bomb. Churchill did not reply to a personal letter from Roosevelt offering to pay the costs of all research and development for an Anglo-American project, so the United States decided in April 1942 that they would go ahead alone. Having made significant contributions early in the war, they no longer possessed the resources to continue such a research program while fighting for their survival, so the Tube Alloys project fell behind in comparison to its American equivalent. On 30 July 1942 John Anderson, the minister responsible for the Tube Alloys project, told Churchill: "D We must face the fact that... our pioneering work... is a dwindling asset and that, if we don't capitalize on it quickly, we will be at a disadvantage. Now we have a real contribution for a “union”. Before long we will have little or none." That same month Churchill and Roosevelt reached an informal, unwritten agreement for collaboration on the atomic question.
However, the opportunity for equal collaboration no longer existed, as demonstrated in August 1942 when the British unsuccessfully applied for substantial control over the project without covering any costs. By 1943, the roles of the two countries had been reversed compared to how they had been at the end of 1941. In January Conant notified the British that they would no longer receive information on atomic research except in certain areas. The British were shocked by the abrogation of the previous agreement between Churchill and Roosevelt, but the head of Canada's National Research Council C.J. Mackenzie was not so surprised, going so far as to say: "I can't help feeling that the UK group gave too much emphasis on the importance of their contribution compared to the Americans". As Conant and Bush told the British, the order came "from above".
The British bargaining position had worsened. American scientists had decided that the United States no longer needed foreign aid and tried to prevent the United Kingdom from taking advantage of commercial applications for atomic energy after the war. The American committee agreed, with Roosevelt's support, to restrict the flow of information to the United Kingdom during the war, especially regarding bomb design, even if doing so would slow down the American project. In early 1943, the British stopped sending research and scientists to the United States, and as a result, the Americans stopped sharing information. The British considered cutting off supplies of uranium and heavy water from Canada to force the Americans to share information, but Canada needed American supplies to produce these items. The British also investigated the possibility of an independent nuclear program, but they concluded that it would not be ready in time to affect the outcome of the war in Europe.
In March 1943 Conant decided that British assistance would be beneficial in some areas of the project. James Chadwick and other British scientists were important enough to be needed for the Los Alamos bomb design team, despite the risk of disclosure of weapons design secrets. In August 1943 Churchill and Roosevelt negotiated the Quebec Agreement, resuming cooperation between scientists from the two countries. The United Kingdom agreed to the reporting restrictions on the construction of large-scale production plants necessary for the bomb. The subsequent Hyde Park Agreement in September 1944 extended this cooperation into the postwar period. The Quebec Agreement established the Combined Policy Committee to coordinate the efforts of the United States, the United Kingdom, and Canada. Stimson, Bush and Conant were the American members of this committee, Field Admiral John Dill and Colonel J. J. Llewellin were the British members, and C. D. Howe the Canadian. Llewellin returned to the UK in late 1943 and was replaced on the committee. by Ronald Ian Campbell, who in turn was later succeeded by British Ambassador to the United States Lord Halifax in early 1945. John Dill died in Washington, D.C. in November 1944 and was succeeded by Field Admiral Henry Maitland Wilson.
Cooperation resumed after the Quebec Agreement and the British were surprised by the spending and progress made by the Americans. The United States had spent more than 1 billion dollars, while the United Kingdom had invested 500,000 pounds. Chadwick lobbied for the British to become fully involved in the Manhattan Project, abandoning any hope of a British project during the war. With the support of Churchill, he tried to ensure that all Groves' requests for help were met. The British mission that arrived in the United States in December 1943 included Niels Bohr, Otto Frisch, Klaus Fuchs, Rudolf Peierls, and Ernest Titterton. More scientists arrived in early 1944. While those assigned to gaseous diffusion marched in In the fall of 1944, the 35 who worked with Lawrence at Berkeley were assigned to existing laboratory groups and remained until the end of the war. The 19 who had been sent to Los Alamos also joined already existing groups, mainly concerned with the assembly and explosion of the bomb, but not with those concerned with plutonium. Part of the Quebec Accord specified that nuclear weapons would not be used against any other country without mutual consent. In June 1945 Wilson agreed that the use of nuclear weapons against Japan would be recorded as a decision of the Combined Policy Committee.
The Combined Policy Committee created the Combined Development Fund in June 1944, with Groves as chairman, to procure uranium and thorium ore on international markets. The Belgian Congo and Canada held much of the world's uranium outside of Eastern Europe, and the Belgian government-in-exile was then in London. The United Kingdom agreed to give the United States most of the Belgian ore, as they could not use it without restricted research by the Americans. In 1944 the Fund purchased 1,560,000 kg of uranium oxide ore from mining companies. in the Belgian Congo. In order to avoid informing US Treasury Secretary Henry Morgenthau Jr. about the project, they used a special bank account not subject to the usual audits and controls that these types of funds had to go through. Between 1944 and the time he resigned from the Fund in 1947, Groves deposited a total of $37.5 million into the Fund's account.
Groves appreciated the early British atomic research and the contributions of British scientists to the project, but stated that the United States would have been just as successful without them. He also said that Churchill was "the best friend the nuclear project had." the atomic bomb, [since] it held Roosevelt's interest... He stirred him up all the time by telling him how important he thought the project was."
British wartime involvement in the project was crucial to the success of the UK's independent nuclear weapons program after the war, when the 1946 McMahon Act temporarily ended US nuclear cooperation.
Project locations
Oak Ridge
The day after taking control of the project, Groves took a train to Tennessee with Colonel Marshall to inspect the proposed site there and was impressed upon arrival. On September 29, 1942, the United States Deputy Secretary of War Robert P. Patterson authorized the Corps of Engineers to acquire 23,000 ha of land by eminent domain at a cost of $3.5 million, with a subsequent acquisition of another 1,200 ha of land. Around a thousand families were affected by the eminent domain order, which became effective on October 7. Various demonstrations, legal appeals, and a congressional consultation in 1943 were unsuccessful. In mid-November the sheriffs eviction signs began to be taped to farm gates two weeks in advance, and construction contractors began to arrive. Some families received two weeks' notice to leave their farms where they had lived for generations, while others had settled there after being evicted by the creation of the Great Smoky Mountains National Park in the 1920s or the construction of Norris Dam in the 1930s. The final cost of land acquisition in the area, a process that was not finalized until March 1945, was for $2.6 million. When presented with Public Proclamation Number Two, which listed Oak Ridge as a no-go area that no one could enter without military permission, Tennessee Governor Prentice Cooper angrily broke 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 focused on the production facility, the Skidmore architecture and engineering firm, Owings & Merrill designed and built a residential community for 13,000 people, located in the foothills of Black Oak Ridge, from which the new town of Oak Ridge took its name. The Army presence in Oak Ridge increased in August 1943 when Nichols took over from Marshall as head of the Manhattan District. One of his first tasks was to move the district headquarters to Oak Ridge, although the name of the district was not changed. In September 1943 the management of the communal facilities was subcontracted to Turner Construction through a subsidiary, Roane -Anderson Company (for Roane and Anderson counties, in which Oak Ridge was located). At these facilities, several chemical engineers were involved in the production of uranium-235 enriched between 10% and 12%, known with the code name "tuballoy tetroxide" (English: tuballoy tetroxide ), under heavy security measures and rapid approvals of requests for supplies and materials. The population of Oak Ridge increased more than planned initially reaching 75,000 residents in May 1945, with about 82,000 people working at the Clinton Engineer Works and another 10,000 at Roane-Anderson.
Los Alamos
The idea of locating Project Y in Oak Ridge was first considered, but it was ultimately decided that this project should be done in a remote location. On Robert Oppenheimer's recommendation, the search for a suitable location was limited to the area around Albuquerque in New Mexico, where Oppenheimer owned a ranch. In October 1942 Officer John H. Dudley was sent to survey the area, recommending a site near Jemez Springs. On November 16 Oppenheimer, Groves, Dudley, and others visited the recommended area. Oppenheimer was concerned that the high boulders surrounding the site could make the workers feel claustrophobic, while the engineers were concerned about the potential for flooding. The group then moved to the vicinity of Los Alamos Ranch School. Oppenheimer was impressed and expressed a strong fondness for this location, citing its natural beauty and views of the Sierra de la Sangre de Cristo. Engineers were concerned about the poor access road to this area and whether the water supply would be ideal, but indicated that otherwise the location was ideal.
Patterson approved the land acquisition on November 25, 1942, authorizing about $440,000 for the purchase of a 22,000 ha piece of land, all but 3,600 ha of which were already owned by the federal government. Secretary of Agriculture Claude R. Wickard relinquished the use of another 40,000 acres of land belonging to the United States Forest Service to the Department of War "as long as military necessity continues". new highway and later rights-of-way for a new 40 km power line, eventually led to the land acquisition of some 40,000 acres, although the expense was only $414,971. Construction was assigned to the company M. M. Sundt Company of Tucson, with Willard C. Kruger and Associates of Santa Fe as architects and engineers. Work began in December 1942. Groves initially allocated about $300,000 for construction, triple Oppenheimer's estimate, with an estimated completion date of March 15, 1943. The scope of Project Y was greater than initially expected and by the time the works were completed on November 30, 1943 the cost had risen to more than 7 million dollars.
Because it was secret, Los Alamos was given the names "Place Y" or "La Colina". Birth certificates for those born in Los Alamos during the war indicated their place of birth in Santa Fe. Los Alamos was originally going to be a military laboratory with Oppenheimer and other researchers commissioned to the military, but two of the project's key physicists, Robert Bacher and Isidor Rabi, rejected this idea. Conant, Groves, and Oppenheimer then defined a compromise whereby the laboratory would be operated by the University of California under a contract with the War Department.
Chicago
At an Army and OSRD council meeting on June 25, 1942, it was decided to build a pilot plant for the production of plutonium at Red Gate Woods, southeast of Chicago. In July Nichols agreed to a 1000 acre cession from the Cook County Forest Preservation District, and Captain James F. Grafton was appointed area engineer in Chicago. Before long it became apparent that the scale of the planned operations was too large for the terrain, so it was ultimately decided to build the plant in Oak Ridge and maintain a research and testing facility in Chicago.
Delays in establishing the plant at Red Gate Woods prompted Compton to authorize the Metallurgical Laboratory to build the first nuclear reactor under the bleachers of the football field at Stagg Field at the University of Chicago. This reactor required a large number of graphite blocks and uranium pellets. At that time the availability of pure uranium was limited. Frank Spedding of Iowa State University was able to produce just two short tons of pure uranium. An additional three short tons of uranium metal was supplied by a Westinghouse Electric-owned Bloomfield, New Jersey, lamp factory, produced quickly using a makeshift process. Goodyear built a large square balloon to encase the reactor. On December 2, 1942, a team led by Enrico Fermi started the first self-sustaining artificial nuclear chain reaction in an experimental reactor known as Chicago Pile-1. The point at which the reaction becomes self-sustaining came to be called the "critical point." Compton reported this success to Conant, who was in Washington, D.C., by coded phone call, saying, "Italian navigator [Fermi] has just landed in the new world."
In January 1943 Grafton's successor, Arthur V. Peterson, ordered the Chicago Pile-1 reactor dismantled and reassembled at Red Gate Woods, as he considered reactor operation too dangerous to remain in a densely populated area. At the Argonne location, Chicago Pile-3, the first heavy water reactor, reached critical point on May 15, 1944. After the war, operations still continuing at Red Gate were moved to to the new location of Argonne National Laboratory, about 6 miles away.
Hanford
In December 1942 concerns were raised that even Oak Ridge was too close to a major population center (Knoxville) in the event of a major nuclear accident. In November of that year Groves had requested the services of DuPont as the main contractor for the construction of the plutonium production complex. The job offer for DuPont included a standard contract, but the company's president, Walter S. Carpenter, Jr., did not want to profit from it, so he requested that the contract be adjusted to explicitly exclude the job offer from DuPont. company may acquire any patent rights. For legal reasons they had to agree to a fee of one dollar and after the war DuPont requested the termination of the contract before the initially agreed date and had to repay 33 cents.
DuPont recommended that the site be located away from the uranium production facilities already built at Oak Ridge. In December 1942 Groves sent Colonel Franklin Matthias and several DuPont engineers to probe potential locations. Matthias reported that the Hanford Site near Richland, Washington, was "ideal in virtually all respects." It was isolated and close to the Columbia River, which could supply enough water to cool the reactors that would produce the plutonium. Groves visited the site in January and the Hanford Engineer Works (HEW) was established, codenamed "Site W".
Deputy Secretary Patterson gave his approval on February 9, 1943, appropriating $5 million for the acquisition of 4,000 acres of land in the area. The federal government relocated some 1,500 residents of White Bluffs, Hanford, and other towns in the area, in addition to the Wanapum and other native people present in the area. There were disputes with various farmers requesting compensation for crops, which they had already planted before the government acquired the land, and the army allowed them to finish harvesting some of these crops in ad hoc cases. The land acquisition process was extended in time and was not completed before the end of the Manhattan Project in December 1946.
Although progress on the design of the reactors at the Metallurgical Laboratory and DuPont was not far enough along to accurately predict the scope of the project, work on the facility began in April 1943 with an estimate of 25,000 workers, with half of these living on site. As of July 1944, some 1,200 buildings had been built and almost 51,000 people lived in the construction camp. As area engineer, Matthias exercised overall control of the site. At its peak, the construction field became the third most populous town in the state of Washington. Hanford operated a fleet of more than 900 buses, more than in the city of Chicago. Similar to Los Alamos and Oak Ridge, Richland was a gated community with restricted access, although it was more like the rapidly growing American populations of the time, in that the military profile was lower and elements Physical security such as fencing and guard towers were less evident.
Canada
British Columbia
The Cominco company had been producing electrolytic hydrogen in Trail, British Columbia since 1930. In 1941 Urey suggested that it could also produce heavy water. Secondary electrolysis cells were added to the existing $10 million plant consisting of 3,215 cells with a power consumption of 75 MW 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 catalysis process for the first three stages, while Urey developed a nickel-chromium oxide process for the fourth stage tower. The final cost was $2.8 million and the Government of Canada was not officially aware of this project until August 1942. Heavy water production at Trail began in January 1944 and continued until 1956. This heavy water was used at Chicago Pile-3, the first nuclear reactor to use heavy water and natural uranium, which reached critical point on May 15, 1944.
Ontario
The Chalk River Laboratories in Ontario were established to house the Allied effort at the Montreal Laboratory away from urban areas. A new community was built in Deep River, Ontario to provide residences and facilities for team members. The site was chosen because of its proximity to the industrial area of Ontario and Quebec and its proximity to a train line adjacent to the Petawawa Garrison military base. Situated on one side of the Ottawa River, this site also had access to sufficient water. The first director of the new laboratory was Hans von Halban, succeeded in May 1944 by John Cockcroft and later by Bennett Lewis in September 1946. The first Canadian reactor was the pilot reactor known as the ZEEP reactor (English: zero-energy experimental pile), also being the first to be completed outside the United States when it reached its critical point in September 1945. The ZEEP reactor remained in use until 1970. In July 1947 it was completed and achieved the critical point a larger 10 MW reactor, the so-called NRX, which was designed during the war.
Northwest Territories
The Eldorado Mine at Port Radium in the Northwest Territories was a source of uranium ore.
Heavy water
Although DuPont's preferred designs for nuclear reactors were helium-cooled and used graphite as a nuclear moderator, DuPont expressed interest in using heavy water as a contingency support should the reactor design fail. graphite was unfeasible for whatever reason. For this purpose it was estimated that about 3 tons of heavy water per month would be required. Project P-9 was the government code name for the heavy water production program. Since the Trail plant, which was still under construction, could produce a half ton per month, additional capacity was required. Groves authorized DuPont to establish heavy water production facilities at the Morgantown Ordnance Works near Morgantown, West Virginia; at the Wabash River Ordnance Works, near Dana and Newport, Indiana; and finally at the Alabama Ordnance Works, near Childersburg and Sylacuga, Alabama. Although known as the Ordnance Works and paid for by contracts in the name of the Ordnance Department, they were built and operated by the Army Corps of Engineers. The US plants used a different production process than Trail, in which the heavy water was extracted by distillation, taking advantage of the slightly higher boiling point of heavy water.
Uranium
Ore
The main material for the project was uranium, used as fuel for nuclear reactors, as a source for its transformation into plutonium and, in its enriched form, in the atomic bomb itself. In 1940 there were four known major uranium deposits: in Colorado, in northern Canada, in Joachimsthal (Czechoslovakia), and in the Belgian Congo, all but Joachimsthal in Allied hands. An investigation in November 1942 determined that the quantities of uranium available were sufficient to satisfy the project's requirements. Nichols defined, together with the Department of State, a series of export controls on uranium oxide and negotiated the purchase of 1,200 tons of uranium ore from the Belgian Congo that was stored in a Staten Island warehouse along with the remaining stocks of ore mined in the Congo. He negotiated with Eldorado Gold Mines the acquisition of ore from its refinery in Port Hope (Ontario) and its delivery in batches of 100 tons. The Canadian government later bought shares in this company until it gained control of it.
Although these acquisitions ensured a supply sufficient for wartime needs, American and British leaders concluded that it was in their respective countries' interests to gain control of the largest number of uranium deposits in the world as were possible. The most abundant source of ore was the Shinkolobwe mine in the Belgian Congo, but it was flooded and closed. Nichols unsuccessfully attempted to negotiate with Edgar Sengier, director of the Upper Katanga Mining Union, the company that owned the mine. The Combined Policy Committee then became involved. As 30% of the shares of the Mining Union were controlled by British interests, they took the lead in the negotiations. John Anderson and Ambassador John Gilbert Winant reached an agreement with Sengier and the Belgian government in May 1944 to reopen the mine and purchase some 1,750 tons of ore at a price of $1.45 per pound. To avoid dependency of the British and Canadians to obtain the mineral, Groves agreed to acquire the uranium reserves of the US Vanadium Corporation in Uravan, Colorado. Uranium mining in Colorado produced about 800 short tons (710 t) of ore.
Mallinckrodt Incorporated in St. Louis, Missouri received the ore and dissolved it in nitric acid to produce uranium nitrate. He then added an ether in a liquid-liquid extraction process to separate impurities from the nitrate. This was heated to form uranium trioxide, which was then reduced to a high purity uranium dioxide. By July 1942 Mallinckrodt was producing a ton of high purity oxide per day, but initially the process for converting the oxide in uranium metal proved more difficult for contractors Westinghouse Electric and Metal Hydrides. Production was too slow and quality too low. A special branch of the Metallurgical Laboratory was then established at Iowa State University at Ames under the leadership of Frank Spedding to investigate alternatives to this initial process. This became known as Project Ames, and the new Ames process became available from 1943.
- Defined uranium in Ames
A “bomb” (pressure recipient) with uranium halure and sacrifible metal, probably magnesium, being introduced into a boiler.
After the reaction the inside of the “bomb” was covered with the remnant slag.
A "gallet" of uranium metal obtained after the reduction reaction.
Isotope Separation
Natural uranium is made up of 99.3% uranium-238 and 0.7% uranium-235, but only uranium-235 is fissile. Both being chemically identical, uranium-235 had to be physically separated from the other, more abundant isotope. Various methods for uranium enrichment were considered during the project, most of them carried out at the Oak Ridge facility.
Centrifugation failed, but electromagnetic separation, gaseous diffusion, and thermal diffusion all succeeded and contributed to the project. In February 1943 Groves had the idea of using the production of some of the plants as the product to be used in others.
Centrifugation
Until April 1942, the centrifugation process was considered the only promising method of separation. Jesse Beams had developed this process at the University of Virginia during the 1930s, but had encountered technical difficulties. The process required high rotation speeds, but when passing through certain speeds, harmonic vibrations were created that could break the machinery. Therefore, it was necessary to obtain rapid acceleration to overcome these speeds. In 1941 Beams began working with uranium hexafluoride, the only gaseous compound of uranium, and succeeded in separating uranium-235. At Columbia, Urey asked Karl Cohen to investigate the process and he produced a body of mathematical theory that made possible the design of a centrifugal separation unit, Westinghouse taking charge of its construction.
Scaling this process to a production facility was a major technical challenge. Urey and Cohen estimated that producing one kilogram of uranium-235 per day would require up to 50,000 spins with 1-meter rotors, or 10,000 spins with 4-meter rotors, assuming it was possible to build the latter. The ability to keep so many rotors operating continuously at high speed was challenging, and when Beams started his experimental apparatus he only got 60% of the expected output. Beams, Urey, and Cohen then began working on a series of improvements to increase the efficiency of the process. However, frequent failures at high speeds of the motors, shafts, and mounts delayed work on the pilot plant. In November 1942 the Military Policy Committee abandoned the centrifugation process following a recommendation by Conant, Nichols, and August C. Klein de Stone & Webster.
Electromagnetic separation
Electromagnetic isotope separation was developed by Ernest Lawrence at the University of California Radiation Laboratory. This method used a device known as a calutron, a hybrid between a standard laboratory mass spectrometer and a cyclotron. The name of the device is derived from the words "California", "university", and "cyclotron". In the electromagnetic process, a magnetic field deflects charged particles according to mass. This process was not considered scientifically elegant or industrially efficient. Compared to a gaseous diffusion plant or a nuclear reactor, an electromagnetic separation plant consumed scarcer materials, required more labor to operate, and cost more to build. However, the process was authorized as it was based on previously proven technology and therefore presented less risk. Furthermore, it could be built in phases and achieve industrial capacity quickly.
Marshall and Nichols concluded that this electromagnetic isotope separation process would require about 4,500 tons of copper, of which there was a significant lack of supply. On the other hand, they could use silver as a substitute, at a ratio of 11 to 10. On August 3, 1942, Nichols met with Deputy Secretary of the Treasury Daniel W. Bell and requested the transfer of 6,000 tons of silver bullion from the Silver Depository. West Point Bullion." They would eventually use some 13,300 tons of silver. in strips 15.9 mm thick, 76 mm wide and 12 m long. The Allis-Chalmers company of Milwaukee, Wisconsin, was responsible for winding the strips into magnetic coils. After the war all the machinery was dismantled and cleaned, extracting and burning the floor plates beneath it to recover as much silver as possible, of which only 1/3,600,000 would ultimately be lost.
The S-1 committee assigned Stone & Webster was responsible for the design and construction of the electromagnetic separation plant, designated Y-12, in June 1942. The design called for five first-stage processing units, called Alpha circuits, and two final processing units, called Beta circuits. Construction began in February 1943, and in September 1943 Groves authorized the construction of four more circuits, designated Alfa II.
When the plant came online for a scheduled test in October of that year, the 14-tonne vacuum tanks were pushed out of alignment by the power of the magnets and had to be more firmly secured. Later a bigger problem arose when the magnetic coils began to short-circuit. In December of that year, Groves ordered one of the magnets to be dismantled for inspection, finding a large amount of rust inside it. Following this discovery, Groves ordered the circuitry dismantled and the magnets sent back to the factory for cleaning. An acid pickling facility was established at the plant itself to clean pipes and other equipment. The second Alpha I circuit was not operational until late January 1944, the first Beta and the first and third Alpha I became available in March. of that same year, and the fourth Alfa I became operational in April. The four Alpha II circuits were completed between July and October 1944.
Tennessee Eastman was contracted to manage the Y-12 plant under a standard cost plus fixed rate contract, with a rate of $22,500 per month plus $7,500 per circuit for the first seven circuits and $4,000 for each circuit additional. The calutron was initially operated by Berkeley scientists to eliminate glitches and achieve a reasonable operational rate. They were eventually replaced by operators trained by Tennessee Eastman who had only received a high school education. Nichols compared unit production data, telling Lawrence that the hillbilly operators were doing better than his PhDs. The two agreed to go on a "production run" which Lawrence lost, which brought a morale boost to Tennessee Eastman workers and supervisors. According to Nichols himself, the young operators "were trained as soldiers not to reason why", while "scientists could not avoid getting into long investigations into the cause of fluctuations in measuring instruments, even the smallest of them".
Initially the Y-12 plant enriched uranium-235 to 13-15%, shipping the first few hundred grams of this product to Los Alamos in March 1944. Only 1 part in 5825 of uranium product consumed emerged as end product. Much of the rest was splattered on the equipment during the process. Several arduous reclamation jobs helped raise production to 10% of the uranium-235 consumed in January 1945. In February of that same year, the Alpha circuits began using a slightly more enriched input product (1.4%) from the new S-50 thermal diffusion plant. The following month it received an upgraded product (5%) from the K-25 gaseous diffusion plant and by August this K-25 plant was producing uranium enriched enough to be used directly in the Beta circuits.
Gas Diffusion
The most promising, but also the most complicated, method of separating isotopes 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 container containing a semi-permeable membrane and a mixture of two gases, the lighter molecules will leave the container. faster than heavier molecules. The gas that comes out of the container is enriched in the lightest molecules, while the residual gas is depleted. The idea proposed was that these containers could be arranged in a cascade of pumps and membranes, with each successive stage containing a slightly more enriched mixture. Investigation of this 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 December 14, M. W. Kellogg accepted an offer to build the plant, which was given the code name K-25. They negotiated a contract at cost plus fixed rate, eventually coming up with a total of $2.5 million. A separate corporate entity called Kellex was created for this project, headed by Percival C. Keith, one of M. W. Kellogg's vice presidents. The process ran into great technical difficulties. They had to use the highly corrosive uranium hexafluoride as the gas, as no substitute could be found, and the motors and pumps would have to be vacuum-sealed and surrounded by inert gas. The biggest problem was the design of the barrier, which had to be strong, porous and resistant to corrosion. The best choice for this purpose seemed to be nickel. Edward Adler and Edward Norris created a mesh barrier out of electroplated nickel. A six-stage pilot plant was built at Columbia to test this process, but the Norris-Adler prototype proved too fragile. Kellex, Bell Telephone Laboratories, and the Bakelite Corporation developed a pulverized nickel-based barrier, and in January 1944 Groves ordered production of this barrier.
Kellex's design for the K-25 plant was a long U-shaped structure 800 meters long, containing 54 adjoining buildings. These buildings were divided into nine sections and within these were cells of six stages. The cells could be operated independently or consecutively within a section. Similarly, the sections could be operated separately or as part of a single cascade. A survey party began construction marking the 2 km² location in May 1943. Work on the main building began in October of that same year and the six-stage pilot plant was ready for operation on April 17, 1944. In 1945 Groves canceled the plant's upper stages, directing Kellex to design a 540-stage supplementary power unit instead, which became known as the K-27. Kellex transferred the last unit to the operation's contractor, Union Carbide and Carbon, on September 11, 1945. The total cost, including completion of the K-27 plant after the war, was $480 million.
The production plant began its operation in February 1945 and as the waterfalls began to be operational, the quality of the product improved. By April 1945 the K-25 plant had achieved 1.1% enrichment and began using the output of the S-50 thermal diffusion plant as an input. Some of the next month's production achieved almost 7% enrichment. In August of that year, the last of the 2,892 stages began to operate. The K-25 and K-27 plants reached their full potential in the early postwar years, eclipsing other production plants and becoming prototypes for a new generation of uranium enrichment plants.
Thermal diffusion
The process of thermal diffusion was based on the theory of Sydney Chapman and David Enskog, which explains that when a mixed gas passes through a temperature gradient, the heavier gas tends to concentrate at the cold end and the lighter at the hot end. Since hot gases tend to rise and cold gases tend to fall, this can be used as a means of separating isotopes. This process was first demonstrated by Klaus Clusius and Gerhard Dickel in Germany in 1938. The method was developed by United States Army scientists, but was not one of the uranium enrichment technologies initially selected for use in the Manhattan Project, as there were doubts about its technical feasibility, although internal rivalry between the army and navy services also played a role in this initial decision.
The Naval Research Laboratory continued this research under the direction of Philip Abelson, but contact with the Manhattan Project was minimal until April 1944 when Captain William S. Parsons, the naval officer in charge of ordnance development in Los Alamos informed Oppenheimer of promising progress in the Navy's experiments on thermal diffusion. Oppenheimer wrote to Groves suggesting that the output from a thermal diffusion plant could be used as an input product for the Y-12 plant. Groves created a committee consisting of Warren K. Lewis, Eger Murphree, and Richard Tolman to investigate this idea, coming up with an estimate that a $3.5 million thermal diffusion plant could enrich 50 kg of uranium per week. until obtaining a uranium-235 of 0.9%. Groves approved its construction on June 24, 1944.
Groves contracted with the H. K. Ferguson Company of Cleveland to build the thermal diffusion plant, called S-50. Groves's advisers, Karl Cohen and W. I. Thompson of Standard Oil, estimated that construction would take six months to complete, but Groves gave only four months. According to the plans, they had to install 2,142 diffusion columns 15 meters high arranged on 21 platforms and inside each column there would be three concentric tubes. Steam obtained from the nearby K-25 power plant, at a pressure of 6 900 kPa and a temperature of 285 °C, flowed down through the innermost 32 mm nickel tube, while water at 68 °C it flowed up through the outermost iron tube. The separation of the isotopes took place in the uranium hexafluoride gas, between the nickel and copper tubes.
Construction work began on July 9, 1944, and the S-50 plant began partial operation in September of that same year. Ferguson operated the plant through its subsidiary Fercleve. By October the plant had produced 4.8 kg of 0.852% uranium-235. Various leaks limited production and forced total stoppages over the next few months, but by June 1945 it achieved a production of 5,770 kg. By March 1945 all 21 production platforms were operating. Initially, the output of the S-50 plant was used to feed the Y-12 plant, but from March 1945 the three enrichment processes began to be carried out in series. The S-50 became the first stage, enriching uranium from 0.71% to 0.89%. This material was used in the gaseous diffusion process at the K-25 plant, producing a product enriched up to 23%, which in turn fed the Y-12 plant, reaching up to 89% there, enough for weapons. nuclear.
Total production of uranium-235
As of July 1945, about 50 kg of uranium enriched to 89% uranium-235 had been delivered to Los Alamos. This entire 50 kg, along with additional 50% enriched uranium, gave a resulting average of 85% enriched uranium, which were used in the Little Boy bomb.
Plutonium
The second line of development pursued by the Manhattan Project used plutonium as a fissile element. Although there are small amounts of plutonium in its natural state, the best way to obtain large amounts of this element is in a nuclear reactor, bombarding the uranium with neutrons. Uranium-238 transmutes to uranium-239, which rapidly decays first to neptunium-239 and then to plutonium-239. Only a small amount of uranium-238 is transformed, so the plutonium has to be chemically separated from the remaining uranium, from the initial impurities and from the products of nuclear fission.
X-10 Graphite Reactor
In March 1943 DuPont began construction of a plutonium plant on a 0.5 km² piece of land in Oak Ridge. Initially intended to serve as a pilot plant for Hanford's larger production facility, it included the air-cooled X-10 graphite reactor, a chemical separation plant, and support facilities. Due to the later decision to build water-cooled reactors at Hanford, only the chemical separation plant operated as a true pilot. The X-10 reactor consisted of a large block of graphite 7.3 m wide on each side, weighing about 1,500 tons and surrounded by 2.1 m thick high-density concrete as a radiation shield.
The main difficulty they encountered was related to the uranium casings produced by Mallinckrodt and Metal Hydrides. These had to be lined with aluminum to prevent corrosion and the escape of fission products into the cooling system. The Grasselli Chemical Company tried to develop a hot-dip tinning process without success, while Alcoa tried a canning process. A new process for fluxless soldering was then developed, and 97% of the cases passed a standard vacuum test, but high-temperature tests indicated a failure rate greater than 50%. Despite this, production began in June 1943. The Metallurgical Laboratory eventually developed an improved welding technique with the assistance of General Electric, a technique that was incorporated into the production process in October 1943.
Supervised by Fermi and Compton, the X-10 graphite reactor went critical on November 4, 1943 with about 30 tons of uranium. A week later the charge was increased to 37 tons, increasing its power to 500 kW, and by the end of the month the first 500 milligrams of plutonium had been created. Modifications made over time increased the power to 4,000 kW in July. 1944. The X-10 reactor operated as a production plant until January 1945, when it was used for research activities.
Reactors at Hanford
Although an air-cooled design had been chosen for the Oak Ridge reactor to expedite construction, this would be unfeasible for larger production reactors. Initial designs by the Metallurgical Laboratory and DuPont used helium for cooling, before they determined that a water-cooled reactor would be simpler, cheaper, and faster to build. The new design was not available until October 4, 1943. Meanwhile Matthias concentrated on improvements to the Hanford site by building accommodation, improving roads, building a rail interchange line and upgrading electricity, water and telephone lines.
As at Oak Ridge, the main difficulty encountered was related to canning the uranium shells, a process that began at Hanford in March 1944. These were pickled to remove dirt and impurities, then given molten baths made of bronze, tin, and an aluminium-silica alloy, they were canned using hydraulic dams and subsequently sealed with arc welding under an argon atmosphere. Finally they carried out a series of tests to detect holes or imperfect welds. Most of the projectiles did not pass these tests, so in the beginning few units were obtained per day that were useful for the process. Progress was made progressively until in June 1944 production was increased to the point where they would have enough shells to activate Reactor B on schedule in August 1944.
Work on the B reactor, the first of six planned 250 MW reactors, began on October 10, 1943. The reactor complexes were given letter designations A through F, with B, D and F the first to be built, as this maximized the distance between reactors. These three were the only ones built during the Manhattan Project. The 37-meter-tall building required about 400 tons of steel, 13,300 m³ of concrete, 50,000 concrete blocks, and 71,000 concrete bricks.
Construction of the reactor itself began in February 1944. Overseen by Compton, Matthias, DuPont's Crawford Greenewalt, Leona Woods, and Fermi, who inserted the first bullet, the reactor was started on September 13, 1944. Over the next few days 838 tubes were loaded and the reactor reached critical point. Shortly after midnight on September 27, operators began to remove the control rods to start production. At first everything seemed to be going well, but around 03:00 the power level started to drop and by 06:00 the reactor had completely stopped. They investigated the cooling water to try to determine if there was a leak or contamination. The next day they restarted the reactor, which came to a complete stop again in the same way.
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. However, DuPont engineer George Graves had deviated from the Metallurgical Laboratory's original design, in which the reactor would have 1,500 tubes arranged in a circle, adding another 504 additional tubes to fill the corners. Scientists had considered this over-engineering and a waste of time and money, but Fermi learned that if they charged all 2,004 tubes the reactor could achieve the required power level and produce plutonium efficiently. The reactor D was started on December 17, 1944, and the F reactor on February 25, 1945.
Separation process
Chemists considered the problem of how to separate plutonium from uranium without knowing its chemical properties. Working with the trace amounts of plutonium available at the Metallurgical Laboratory in 1942, a team led by Charles M. Cooper developed a lanthanum fluoride process to separate the uranium and plutonium, chosen for the pilot separation plant. Glenn Seaborg and Stanly G. Thomson later developed a second separation process, the bismuth phosphate process. The operation of this process was to switch plutonium between its +4 and +6 oxidation states in bismuth phosphate solutions. In the first state, plutonium precipitated and in the last one it was kept in solution, precipitating other products.
Greenewalt favored the bismuth phosphate process due to the corrosive nature of lanthanum fluoride, and this process was chosen for the Hanford separation plants. As soon as the X-10 reactor began producing plutonium, the pilot plant of separation began its tests. The first batch was processed with an efficiency of 40%, which increased in the following months to 90%.
At Hanford, the facility in area 300 was given top priority. This contained buildings for testing materials, uranium preparation, and instrument assembly and calibration. One of the buildings contained canning equipment for uranium bullets, while another contained a small test reactor. Despite the high priority assigned, work in the 300 area was delayed according to the initial plan by the unique nature and complexity of the facilities, as well as a wartime lack of workers and materials.
Initial plans called for the construction of two separation plants in each of the areas known as 200-West and 200-East. Later the plan was reduced to only two plants, the T and U plants, in the 200-West area, and one, the B plant, in the 200-East area. Each separation plant was made up of four buildings: a building of processing cells or "cannon" (known as 221), a concentration building (224), a purification building (231) and a charger warehouse (213). The canyons were 240 m long and 20 m wide each and consisted of 40 cells measuring 5.4 x 4 x 6.1 m.
Work on buildings 221-T and 221-U began in January 1944, completing the first in September and the other in December of the year. Building 221-B was the next to be completed, in March 1945. Because of the high levels of radioactivity, all work in the separation plants had to be done remotely using closed-circuit television. Maintenance was carried out with the help of an overhead crane and tools specifically designed for this purpose. The 224 buildings were smaller as they had to process less material and it was less radioactive. Buildings 224-T and 224-U were completed on October 8, 1944, and 224-B on February 10, 1945. The purification methods that would eventually be used in 231-W were still unknown when the building was built. The same began on April 8, 1944, but the plant was completed at the end of the same year with the methods already selected. On February 5, 1945 Matthias delivered the first shipment of 80 grams of pure plutonium nitrate at 95 % to a courier from Los Alamos in Los Angeles.
Weapon Skins
In 1943, design efforts were aimed at developing a ballistic-type fission weapon with plutonium called the Thin Man. Initial research into 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 Álamos received the first sample of plutonium from the Clinton X-10 reactor in April 1944, and three days after that, Emilio Segrè discovered a problem: the plutonium generated in the reactor had a higher concentration of plutonium-240, which gave as The result was a rate of spontaneous fission five times greater than cyclotron-generated plutonium. Seaborg had already correctly predicted in March 1943 that some plutonium-239 would absorb a neutron to become plutonium-240.
This rendered reactor-generated plutonium useless for use in a ballistic-type weapon. The plutonium-240 would start the chain reaction too early, causing a predetonation that would release enough energy to disperse the critical mass with only a minimal amount of reacted plutonium (a long fire). Scientists suggested a faster weapon, but it turned out to be unfeasible. The possibility of separating the isotopes was also considered and rejected, since plutonium-240 is even more difficult to separate from plutonium-239 than uranium-235 from uranium-238.
Work on an alternative method of bomb design, known as implosion, had already begun earlier under the direction of physicist Seth Neddermeyer. The implosion used explosives to crush a subcritical sphere of fissile material into a smaller, denser form. When fissile atoms are squeezed together, the rate of neutron capture increases and the mass becomes critical. The metal needs to travel only a very short distance, so the critical mass is assembled in much less time than it would take with a ballistic method. Early investigations of the Neddermeyer implosion in 1943 and early 1944 were promising, but also they made it clear that the problem would be much more difficult from an engineering and theoretical perspective than for the weapon design itself. In September 1943 John von Neumann, who already had experience with shaped charges used in armor-piercing projectiles, argued that the Implosion would not only reduce the danger of predetonation and long fire, but would also make more efficient use of fissile material, and he proposed using a spherical configuration instead of the cylindrical one Neddermeyer was working on.
In July 1944 Oppenheimer concluded that plutonium could not be used in a ballistic design and opted for the implosion design. The accelerated design effort for an implosion design, codenamed Fat Man, began in August 1944 when Oppenheimer put into operation a reorganization of the Los Alamos Laboratory. Two new groups were created. in the laboratory, Division X (for explosives) led by explosives expert George Kistiakowsky and Division G (for "gadget") under the leadership of Robert Bacher. The new design which had been designed by Von Neumann and the T (for theoretical) Division, mainly Rudolf Peierls, used explosive lenses to focus the explosion into a spherical shape using a combination of fast and slow-explosion elements.
Designing lenses that would detonate with the proper shape and velocities proved slow, difficult, and frustrating for scientists. They tried various explosives until settling on composition B as the fast explosive and barbarol as the slow explosive. The final design It looked like a soccer ball, with 20 hexagonal and 12 pentagonal lenses, each weighing about 36 kg. Achieving the correct detonation required fast, reliable, and electrically safe detonators, two for each lens for reliability. Therefore, they decided to use explosive jumper wire detonators, a new invention developed at Los Alamos by a group led by Luis Walter Álvarez. The Raytheon company was contracted to manufacture these devices.
To study the behavior of converging shock waves, Robert Serber devised the RaLa experiment, which used the short-lived radioisotope lanthanum-140, a powerful source of gamma radiation. The gamma ray source was located in the center of a metal sphere surrounded by the exploding lenses, which in turn were inside an ionization chamber. This allowed an X-ray movie of the implosion to be filmed. The explosive lenses were designed primarily using the results of this series of tests. In his history of the Los Alamos project, David Hawkins wrote: "RaLa became the most important experiment to affect the final design of the bomb."
Inside the explosives were 110mm-thick aluminum reflectors that provided a smooth transition from the lower-density explosive to the next layer, a 76mm-thick natural uranium lock. Its main function was to keep the critical mass together for as long as possible, but it would also reflect neutrons back into the nucleus and part of it could fission as well. To prevent predetonation from external neutrons, it had a safety coated with a thin layer of boron. A polonium-beryllium modulated neutron initiator was developed, known as an "urchin" (hedgehog) because its shape resembled that of a hedgehog. of sea, to start the chain reaction at the right time. This work on the chemistry and metallurgy of radioactive polonium was led by Charles Allen Thomas of the Monsanto company and became known as the Dayton Project. The tests required up to 500 curies per month of polonium, which Monsanto could supply. The assembled assembly was encased in a duralumin bomb casing to protect it from bullets and anti-aircraft fire.
The biggest challenge for metallurgists was figuring out how to shape plutonium into a sphere. The difficulties became apparent when attempts to measure the density of plutonium yielded inconsistent results. Scientists initially believed these inconsistencies were due to contamination, but they soon determined that multiple allotropes of plutonium existed. The unstable α phase that exists at room temperature changes to a plastic β phase at higher temperatures. The scientists focused on the more malleable δ phase that exists in the temperature range between 300°C and 450°C. This was stable at room temperature in an alloy with aluminium, but aluminum emits neutrons when bombarded with alpha particles, which would exacerbate the predetonation problem. The scientists obtained a plutonium-gallium alloy that stabilized this δ phase and could be hot-pressed into the desired spherical shape, which was given a layer of nickel to prevent the plutonium from corroding.
These jobs were dangerous and by the end of the war half the experienced chemists and metallurgists had to be discharged due to high levels of plutonium appearing in their urine. A small fire at Los Alamos in January In 1945, concerns were raised that the plutonium laboratory could contaminate the entire town, so Groves authorized the construction of a new plutonium chemistry and metallurgy facility, which became known as the DP site. The first plutonium core hemispheres were produced and delivered on July 2, 1945, with three more hemispheres produced on July 23 and delivered three days later.
Try Trinity
Due to the complexity of an implosion weapon it was decided that, despite the expense of fissile material, an initial test would be necessary. Groves passed this test, provided the active material could be recovered. Scientists considered causing a long controlled fire, but Oppenheimer opted for a full nuclear test, codenamed "Trinity".
In March 1944 Kenneth Bainbridge, professor of physics at Harvard University, was assigned to plan the test under Kistiakowsky's direction. Bainbridge chose the bombing range near Alamogordo Army Airport as the site for the test. Bainbridge worked with Captain Samuel P. Davalos on the construction of Trinity Base Camp and its facilities, which included barracks, warehouses, workshops, a powder keg and a curator.
Groves was not enthusiastic about explaining the loss of billions of dollars worth of plutonium to a Senate committee, so they built a containment vessel codenamed "Jumbo" to recover the material active in case of test failure. At 7.6m long and 3.7m wide, this device was manufactured from 217 tons of iron and steel at the Babcock & Wilcox in Barberton, Ohio. It was transported by special railway to a siding in Pope, New Mexico, and from there it was driven the last 40 km to the test site pulled by two tractors. When it arrived at the site, confidence that the implosion method would work was high and the availability of plutonium sufficient, so Oppenheimer decided not to use it. Instead they placed it on top of a steel tower 730m away from the weapon to gauge how powerful the explosion would be. Upon testing the Jumbo survived, despite the fact that the tower it was on did not, furthering the belief that the Jumbo might have been enough to contain a long fire in the explosion.
On May 7, 1945, they conducted an initial test explosion to calibrate the instruments. They erected a wooden platform about 730m from ground zero and heaped 100 tons of TNT with the addition of trace amounts of nuclear fission products in the form of irradiated uranium from Hanford, which had been dissolved and poured into the explosive. Oppenheimer oversaw this explosion alongside Groves's new deputy commander, Brigadier General Thomas Farrell. The data they obtained in this initial test turned out to be vital to the Trinity test.
For the test, they hoisted the weapon, codenamed "the gadget," on top of a 100-foot steel tower, since detonation at that height would give a better indication of how the weapon would behave when launched from a bomber. Detonation in the air would maximize the energy applied directly to the target, and would generate less radioactive waste. The instrument was set up under the supervision of Norris Bradbury in the nearby McDonald Ranch House building on July 13 and precariously winched up the next day. Observers for the test included Bush, Chadwick, Conant, Farrell, Fermi, Groves, Lawrence, Oppenheimer, and Tolman. At 05:30 on July 16, 1945, the instrument exploded with an energy equivalent to about 20 kilotons of TNT, leaving a crater of trinitite (radioactive crystal) in the desert 76 m wide. The shock wave was felt up to 160 km away and the mushroom cloud reached 12 km in height. The detonation was heard in the city of El Paso, Texas, so Groves had to spread a story about an explosion in a powder magazine in the Alamogordo field to cover up the evidence.
Oppenheimer later recalled that, while witnessing the explosion, he thought of a verse from the Hindu holy book, the Bhagavad-gītā (XI,12):
-の ा ा。 ा。 ा。 ा。 ा。 ा。 ा。 ा。 ा。 ा。 ा。 प。 ि。 ि。 ि。 ि。 ं。 ं。 ा。 ा。 ा。 ा。 ा。 ा。 -。 -。 -。 -。 -。 -。 -。 -。 -。 - -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 - -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 - -。 -。 -。 -。 -。 -。 -。 -。 -。 -。 -If the radiance of a thousand suns exploded at the same time in the sky, it would be like the splendor of the mighty...
Years later, he would explain that another verse had also crossed his mind at that time:
We knew the world wouldn't be the same. Some people laughed, others wept. Most people stayed silent. I remembered the line of the Hindu scriptures, the Bhagavad Gita; Vishnu is trying to persuade the Prince that he must do his duty and, to impress him, adopts his omniform and says: "Now I have become Death, the destroyer of worlds." I guess we all think that one way or another. Oppenheimer read the original text in Sanskrit (XI,32),
Staff
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 slowed, the workforce dropped to 100,000 employees a year later, even as military personnel increased to 5,600. Recruiting the required number of workers, especially highly-skilled ones, in competition with other vital wartime programs, proved to be very difficult. In 1943 Groves was given special priority for the work of the War Personnel Commission and in In March 1944 both this commission and the War Production Board gave the project the highest priority.
Tolman and Conant, in their role as scientific advisors to the project, developed a list of candidate scientists who were vetted by other scientists already working on the project. Groves then sent a personal letter to the presidents of their universities or heads of their companies asking them to be released to do essential war work. At the University of Wisconsin–Madison, Stanislaw Ulam had to advance Joan Hinton one of her exams so she could go to work on the project. A few months later, Ulam himself received a letter from Hans Bethe, inviting him to join the project, while Conant personally convinced Kistiakowsky to join as well.
One of the sources of qualified personnel was the army itself, particularly its Specialized Training Program. In 1943 the Special Engineering Detachment was created, with an authorized force of 675 troops. Technicians and skilled workers conscripted into the army were assigned to this detachment. Another source of personnel was the Women's Army Corps. Prepared at first for office tasks in the handling of classified material, soon after the personnel of this body were also assigned to scientific and technical tasks.
An associate professor of radiology at the University of Rochester, Stafford L. Warren, was made a colonel in the Army Medical Corps and appointed head of the project's medical section, as well as Groves' medical advisor. His initial assignment was directing medical staff at Oak Ridge, Richland, and Los Alamos hospitals.The Medical Section was responsible for medical research and health and safety programs. This posed a great challenge, as workers handled a variety of toxic chemicals, used dangerous liquids and gases under high pressure, worked with high voltages, and conducted experiments with explosives, in addition to the unknown dangers of radioactivity and material handling. However, in December 1945 the National Security Council awarded the Manhattan Project the Distinguished Service to Security Honor Award in recognition of its security record. Between January 1943 and June 1945 there were 62 fatalities and 3,879 incapacitated injuries on the project, 62% below the rate for private industry.
Secrecy
A 1945 article in Life magazine estimated that before the atomic bombings of Hiroshima and Nagasaki "probably no more than a few dozen men in the whole country knew the full significance of the Manhattan Project." and perhaps only a thousand others knew that it was work on atoms.' The magazine wrote that more than 100,000 employees on the project "worked like moles in the dark." Warned that divulging project secrets was punishable by 10 years in jail or a fine of $10,000 (about $102,000 today), workers saw huge amounts of raw material entering the factories without anything leaving. and they supervised "valves and switches while behind the thick concrete walls mysterious reactions took place" without knowing the purpose of their work.
Uncle Sam's taken off his hat and he's taking off. On the wall in front of it there are three monkeys and the motto: What you see here
What you do here
What you hear here
When you get out of here
Stay here.
Oak Ridge security staff considered any private party with more than seven people suspicious, and residents — who believed government agents were secretly infiltrated among them — avoided repeatedly inviting the same guests. Although the original residents of the area could be buried in existing cemeteries, all coffins had to be opened in front of a member of the security force for inspection. All residents, including senior officers, and their cars, they had to go through a search when entering and leaving the project facilities. An Oak Ridge worker publicly stated that “if you were inquisitive, secret government agents would call you in less than two hours. Usually those who called to give explanations accompanied us with the suitcases to the front door and ordered them to continue walking. However, despite being told that their work would help end the war and perhaps all future wars, they did not see or understand the results of their tedious tasks, the typical side effects of factory work, and the end of the war in Europe without the use of their labor caused serious problems in the morale of the workers and spread many rumors. One manager said that after the war:
Well, it wasn't hard work... it was confusing. No one knew what was being done in Oak Ridge, not even me, and many people thought he was was was wasting time here. It was up to me to explain to the dissatisfied workers that they were doing a very important job. When they asked me what it was, I had to tell them a secret. But I almost went crazy trying to figure out what was going on.
Another worker told how, working in a laundry, she passed a “special instrument” to the uniforms every day that made a “click”. It was not until after the war that this worker learned that she had been performing the task of looking for radiation with a Geiger counter. To improve morale among these workers, an extensive system of intramural sports leagues was created at Oak Ridge, including 10 baseball teams, 81 softball teams, and 26 football teams.
Censorship
Voluntary censorship of atomic data began before the Manhattan Project. After the start of the war in Europe in 1939, American scientists began to avoid publication of military-related research, and in 1940 scientific journals began asking the National Academy of Sciences to approve the publication of certain articles. William L. Laurence of The New York Times wrote an article for The Saturday Evening Post on atomic fission in September 1940, later learning that in 1943 various government agents had requested libraries across the country to withdraw that number. The Soviets learned of this silence, and in April 1942 nuclear physicist Georgy Fliorov wrote to Joseph Stalin advising him of the absence of articles on nuclear fission in American publications.. This triggered the Soviet Union to set up its own project for an atomic bomb.
The Manhattan Project operated under tight security to try to prevent its discovery from inducing the Axis powers, especially Germany, to accelerate their own nuclear projects or carry out covert operations against the project. The government's Censorship Office relied on the press to abide by a voluntary code of conduct in their publications, and the project initially went largely unnoticed. Beginning in 1943, newspapers began running reports of major construction in Tennessee and Washington based on public records, and the office began reviewing with project management how they could maintain secrecy. In June the Censorship Office asked newspapers and broadcasters to avoid discussing "atom crushing, atomic energy, atomic fission, atomic separation, or any of their equivalents," as well as "the use for military purposes of radium or materials radioactive, heavy water, high voltage discharge equipment or cyclotrons. The office also asked to avoid discussions about "polonium, uranium, ytterbium, hafnium, protactinium, radium, rhenium, thorium, and deuterium"; although only the uranium was classified, it was listed along with other elements to hide its importance.
Soviet espionage
The possibility of sabotage was present throughout the project, suspicion arose at times when equipment failures occurred. Although some problems were confirmed to have been caused by dissatisfied or negligent employees, there were no confirmed cases of Axis-instigated sabotage. However, on 10 March 1945 a Japanese incendiary balloon crashed into a power line, causing a power surge. which caused the temporary stoppage of three reactors at Hanford. With a very high number of people involved in the project, its safety was a complicated task. A special task force called the Counter-Intelligence Corps was formed to deal with the security problems of the project. By 1943 the Americans were certain that the Soviet Union was trying to infiltrate the project. Lt. Col. Boris T. Pash, head of the Western Defense Command's counterintelligence branch, investigated suspected Soviet espionage at the Radiation Laboratory in Berkeley. Oppenheimer confirmed to Pash that a fellow Berkeley professor, Haakon Chevalier, had requested some information from him to pass on to the Soviet Union.
The most successful Soviet spy was Klaus Fuchs, a member of the British mission with a prominent role at Los Alamos. The disclosure in 1950 of his espionage activities damaged US nuclear cooperation with the UK and Canada. Other espionage cases were subsequently uncovered, resulting in the arrests of Harry Gold, David Greenglass, and Ethel and Julius Rosenberg. Other spies such as George Koval and Theodore Hall went undiscovered for several decades. The value of these actions espionage is difficult for historians to quantify, since the main constraint on the Soviet atomic bomb project was the scarcity of uranium ore. The general consensus is that espionage saved the Soviets a year or two of investigation.
Foreign intelligence
In addition to developing the atomic bomb, the Manhattan Project was tasked with gathering intelligence on the German nuclear power project. The Americans believed that Japan's nuclear weapons program was not very advanced since Japan had access to very little uranium ore, but they did fear that Germany was very close to developing its own nuclear weapons. Instigated by the Manhattan Project, a campaign of bombing and sabotage was carried out against heavy water plants in German-occupied Norway. A small mission was created with personnel from the Office of Naval Intelligence, OSRD, the Project itself. Manhattan and the G-2 Army Intelligence Group to investigate enemy scientific developments, not limited to those related to nuclear weapons. Army Intelligence Chief Maj. Gen. George V. Strong assigned Boris Pash to the command of the unit, which received the code name "Alsos", a word of Greek origin meaning "grove".
In Italy, the so-called Alsos mission interrogated the staff of the Sapienza University of Rome's physics laboratory after the city's capture in June 1944. Meanwhile, Pash formed a combined division of the British and American mission, in London, under the command of Captain Horace K. Calvert to participate in Operation Overlord. Groves considered that the risk that the Germans might try to stop the Normandy landings with radioactive poisons was enough to warn General Dwight of this. D. Eisenhower sending an officer to report to his chief of staff, Lieutenant General Walter Bedell Smith. Codenamed Operation Peppermint, special equipment was prepared and Chemical Warfare Service teams trained to use it.
Following the first advances of the Allied armies in Europe, Pash and Calvert met with Frédéric Joliot-Curie to ask him about the activities of German scientists. They also spoke with officials from the Upper Katanga Mining Union about uranium shipments being sent to Germany. They located 68 tons of ore in Belgium and another 30 tons in France. Interrogations of several German prisoners indicated that the uranium and thorium were being processed in Oranienburg, about 20 miles from Berlin, so Groves ordered its bombing on March 15, 1945.
A team from the Alsos mission traveled to Stassfurt in the Soviet occupation zone and recovered 11 tons of uranium ore from the facilities of the Wirtschaftliche Forschungsgesellschaft company. In April 1945 Pash, commanding a known composite force as T-Force, it carried out Operation Harborage, a sweep behind enemy lines of the cities of Hechingen, Bisingen, and Haigerloch that comprised the heart of the German nuclear effort. T-Force captured nuclear laboratories, documentation, equipment, and supplies, including heavy water and 1.5 tons of uranium metal.
Several teams from the Alsos mission were also responsible for capturing several German scientists, including Kurt Diebner, Otto Hahn, Walther Gerlach, Werner Heisenberg and Carl Friedrich von Weizsäcker, who were taken to England and interned in Farm Hall, a guarded residence in Godmanchester. Following the detonation of the bombs in Japan, the Germans were forced to face the fact that the Allies had done what they could not.
Atomic bombings of Hiroshima and Nagasaki
Preparations
Beginning in November 1943, the Air Force Materiel Command at Wright Field, Ohio, began the Silverplate program, the code name for the Boeing B-29 Superfortress aircraft modification to carry bombs. They conducted bombing tests at Muroc Army Airfield and at the Inyokern, California Naval Weapons Test Station. Groves met with the head of the United States Army Air Forces (USAAF), General Henry H. Arnold, in March 1944 to discuss the delivery of the completed bombs. The 150cm wide >Fat Man was the British Avro Lancaster, but using a British aircraft would cause maintenance difficulties. Groves hoped that the American B-29 Superfortress could be modified to carry a Thin Man bomb by joining its two bomb bays together. Arnold promised him that they would do everything possible to modify the B-29s and appointed the Major General Oliver P. Echols as USAAF liaison officer for the Manhattan Project. Subsequently, Echols appointed Colonel Roscoe C. Wilson as his replacement, and Wilson became the primary USAAF contact for the Manhattan Project. President Roosevelt instructed Groves that if the atomic bombs were ready before the end of war with Germany, it should prepare to launch them in Germany.
The 509th Composite Group was activated on December 17, 1944 at Wendover Air Force Base in Utah, under the command of Colonel Paul W. Tibbets. This base, near the Nevada border, was given the code name "Kingman" or "W-47." Training took place in Wendover and at the San Antonio de los Baños Air Base in Cuba, where the 393rd Bomber Squadron practiced long-distance flights over the sea and dropped test pumpkin bombs. A special unit known as Project Alberta was formed at Los Alamos under the command of Navy Captain William S. Parsons of Project Y, as part of the Manhattan Project's duties to assist in the preparations and delivery of the bombs. Commander Frederick L. Ashworth of Alberta met with Fleet Admiral Chester W. Nimitz in Guam in February 1945 to inform him of the project. While there Ashworth chose North Field on Tinian Island in the Pacific as a base for the 509th Composite Group and reserved site for the group and the necessary buildings, deploying it there in July 1945. Farrell arrived on Tinian on 30 July as a representative of the Manhattan Project.
Most of the components of the Little Boy bomb left San Francisco on the cruise ship USS Indianapolis on July 16, arriving at Tinian on July 26. Four days later the ship was sunk by the Japanese submarine I-58. The rest of the components, including six uranium-235 rings, were delivered by three Douglas C-54 Skymasters of the 320 Troop Carrier Squadron of the 509 Group. Two Fat Man assemblies were brought to Tinian on specially modified B-29 aircraft belonging to the 509 Group and the first plutonium core was flown in a special C-54. A joint targeting committee was established between the Manhattan District and the USAAF to determine which cities in Japan should be targeted, recommending the cities of Kokura, Hiroshima, Niigata and Kyoto. It was then that Secretary of War Henry L. Stimson intervened, announcing that he would make the decision on the objectives and that he would not authorize the bombing of Kyoto due to its historical and religious importance. Groves then asked Arnold to remove Kyoto not only from the nuclear target list, but also from the conventional bombing target list. One of the cities chosen as a possible substitute target for Kyoto was Nagasaki.
Bombing
In May 1945, the Interim Committee was created to advise on the wartime and postwar use of nuclear energy. Its president was Stimson, with James F. Byrnes, former senator and later secretary of state, as the personal representative of President Harry S. Truman; Ralph A. Bard, Deputy Secretary of the Navy; William L. Clayton, Assistant Secretary of State; Vannevar Bush; Karl T. Compton; James B. Conant and George L. Harrison, Stimson's assistant and president of New York Life Insurance Company. This committee established a panel of scientists consisting of Arthur Compton, Fermi, Lawrence, and Oppenheimer to advise on scientific questions. In their presentation before the Interim Committee, the panel of scientists gave their opinion not only on the likely physical effects of an atomic bomb, but also on its likely military and political impact.
During the Potsdam conference in Germany, Truman received the news that the Trinity test had been a success. There he told Stalin that the United States had a new superweapon, without giving further details. This was the first official communication to the Soviet Union about the bomb, although Stalin already knew about it from his spies. With the authorization to use the bomb against Japan already granted, no alternative was considered following the Japanese rejection of the declaration. from Potsdam.
On August 6, 1945, a Boeing B-29 Superfortress named Enola Gay of the 393rd Bomber Squadron, flown by Tibbets, took off from North Field carrying the Little Boy bomb. > in its cargo hold. Hiroshima was the mission's primary objective as it was the headquarters of the 2nd General Army, 5th Division and was a shipping port, with Kokura and Nagasaki as alternatives. With Farrell's permission, Parsons, the lead gunner for the mission, completed the assembly of the bomb in the air to minimize risk during takeoff. The bomb detonated at an altitude of 530 m with an explosion estimated to be equivalent to about 13 kilotons of TNT. An area of approximately 12 km² was destroyed. Japanese officials determined that 69% of Hiroshima's buildings were destroyed and another 6–7% were damaged. Between 70,000 and 80,000 people, 20,000 of these Japanese soldiers and another 20,000 Korean slave laborers, 30% of Hiroshima's population at the time, died immediately, with another 70,000 injured.
On the morning of August 9, 1945, the B-29 Bockscar, flown by the commander of the 393rd Bomber Squadron, Major Charles Sweeney, took off with the Fat Man in its cargo hold. This time Ashworth was the gunner and Kokura was the primary target. Sweeney took off with the bomb already assembled but with the electrical safety systems still activated. By the time they reached Kokura a cloud cover had obscured the city, preventing them from carrying out the visual approach required by the orders. After three passes over the city and with increasingly low fuel, they headed towards the secondary objective, Nagasaki. Ashworth decided to use a radar approach in case the target was obscured, but the clouds parted over Nagasaki at the last moment, allowing them to make a visual approach on orders. The Fat Man bomb was dropped on the city's industrial valley halfway between the Mitsubishi steel and weapons facilities in the south and the Mitsubishi-Urakami artillery facilities in the north. The resulting explosion had an equivalent of about 21 kilotons of TNT, about the same as the Trinity test, but was confined to the Urakami Valley and a large part of the city was protected by the intervening mountains, resulting in the destruction of 44% of the city approx. The bombardment also severely limited the industrial production capacity of the city and between 23,200 and 28,200 industrial workers were killed along with 150 Japanese soldiers. In all, between 35,000 and 40,000 people were killed and another 60,000 injured.
Groves expected to have another atomic bomb ready for use on August 19, along with three more in September and three more in October. Two more Fat Man bomb assemblies scheduled for leave Kirtland Air Force Base to Tinian on August 11 and 14. At Los Alamos, technicians worked 24 successive hours to mold another plutonium core that would still need pressing and coating, so it would not be ready until August. August 16. However, on August 10 Truman requested that no more atomic bombs be dropped on Japan without his express authorization. Groves suspended shipment of this third core using his own authority on August 13.
On August 11, Groves phoned Warren to order him to organize a new survey team to investigate the damage and radioactivity in Hiroshima and Nagasaki. A party equipped with portable Geiger counters arrived in Hiroshima on 8 September, led by Farrell and Warren, with Japanese Vice Admiral Masao Tsuzuki acting as translator. They remained in Hiroshima until September 14, and then sounded Nagasaki from September 19 to October 8. This exploration, along with subsequent scientific missions in Japan, provided valuable historical and scientific data.
The necessity of the bombings of Hiroshima and Nagasaki became a controversial issue among historians. Some of them questioned whether "atomic diplomacy" would not have achieved the same goals and debated whether the bombing raids or the Soviet declaration of war against Japan were decisive. The Franck Report of June 1945 was the main effort to prevent the bombing, but it was rejected by the scientific panel of the Interim Committee. The Szilárd petition, drafted in July 1945 and signed by dozens of scientists working on the Manhattan Project, was a belated attempt to warn President Truman of the responsibility required for the use of of this type of weaponry.
Post-war and dissolution
Seeing that work they did not quite understand had produced the bombings of Hiroshima and Nagasaki, the Manhattan Project workers were as surprised as the rest of the world. Newspapers in Oak Ridge with the announcement of the Hiroshima bombing sold for $1 (about $11 today). Despite the fact that the existence of the bomb was already public, the secrecy in the project continued, many of them workers continued to ignore the purpose of their work, and many Oak Ridge residents continued to avoid discussing "the stuff" in common conversation.
In anticipation of the bombing, Groves ordered Henry DeWolf Smyth to prepare a story for the public. Atomic Energy for Military Purposes, better known as the "Smyth report", was published on August 12, 1945. Groves and Nichols awarded the Army-Navy "E" Award to major contractors, involved in the project in secret until then. More than 20 Presidential Medals of Merit were also awarded to contractors and scientists, including Bush and Oppenheimer. Military personnel were awarded the Legion of Merit, including Women's Army Corps detachment commander Captain Arlene G. Scheidenhelm.
At Hanford, plutonium production decreased due to the exhaustion of reactors B, D and F, poisoned by fission products and inflammation of the graphite moderator, something known as the Wigner effect. The inflammation damaged the loading tubes where the uranium was irradiated to produce the plutonium, rendering them useless. To maintain the supply of polonium for the "hedgehog" starters, production was limited and the oldest unit, Stack B, was shut down so that at least one of the reactors would be available in the future. Research continued, with DuPont and the Metallurgical Laboratory developing a redox solvent extraction process as an alternative plutonium extraction technique to the bismuth-phosphate process, leaving the unspent uranium in a state from which it could not be readily recovered.
Bomb engineering was continued by Division Z, named for its director Jerrold R. Zacharias of Los Alamos. Z Division was originally located in Wendover but moved to Oxnard Field, New Mexico, in September 1945 to be closer to Los Alamos. This marked the beginning of the Sandia Base. The airbase near Kirtland was used as the B-29 base for aircraft compatibility and launch testing. By October all of Wendover's facilities and personnel had been transferred to Sandia and reserve officers who were demobilized they were replaced by about 50 hand-selected regular officers.
Nichols recommended shutting down the S-50 plant and the Alpha circuits of the Y-12 plant, completing this in September. Despite peak performance, the Alpha circuits could not compete with the plants K-25 and the new K-27, which had started operations in January 1946. In December the Y-12 plant was closed, thus reducing Tennessee Eastman's daily wage costs from $8,600 to $1,500, which meant a saving of about 2 million dollars a month.
The main demobilization problem was at Los Alamos, where there was an exodus of talent despite still more work being required. They needed to make bombs like those used on Hiroshima and Nagasaki simpler, safer, and more reliable. It was also necessary to develop implosion methods for uranium, thus replacing the less efficient ballistic method, and they needed uranium-plutonium composite nuclei due to the lack of supplies of the latter due to problems with the reactors. However, uncertainty about the future of the laboratory was a problem in getting the workers to stay there. Oppenheimer returned to his job at the University of California, and Groves named Norris Bradbury as interim replacement, who would ultimately remain in this position for the next 25 years. Groves attempted to combat dissatisfaction caused by lack of services with a construction program which included an improved water supply system, three hundred new residences and recreational facilities.
In July 1946, two Fat Man bombs were detonated at Bikini Atoll as part of Operation Crossroads to investigate the effect of nuclear weapons on warships. The "Able" bomb was detonated at an altitude of 158 m on July 1, 1946, and the "Baker" bomb was detonated 27 m underwater on July 25, 1946.
After the bombings of Hiroshima and Nagasaki, several physicists from the Manhattan Project founded the Bulletin of the Atomic Scientists, initiated as an emergency action by scientists who saw an urgent need for an immediate educational program on atomic weapons. After seeing the destructive power of these new weapons and anticipating a nuclear arms race, several of the members of the project, including Bohr, Bush and Conant, expressed the opinion that an agreement was necessary on the international control of nuclear research and nuclear weapons. The Baruch plan, revealed in a speech to the newly formed United Nations Atomic Energy Commission in June 1946, proposed the establishment of an international authority for atomic development, but the proposal was not adopted.
Following internal debate over the ongoing administration of the nuclear program, the United States Atomic Energy Commission was created by the Atomic Energy Act of 1946, taking over the functions and assets of the Manhattan Project. This commission established civilian control over atomic development and separated the development, production, and control of nuclear weapons from the military, while military issues were taken over by the Armed Forces Special Weapons Project. The Manhattan Project ceased to operate. existed on December 31, 1946, while the Manhattan District remained until its dissolution on August 15, 1947.
Cost
| Cost ($ in 1945) | Cost ($ in 2016) | % of total | |
|---|---|---|---|
| Oak Ridge | 1190 million | 41 billion | 62.9 % |
| Hanford | 390 million | 13.7 billion | 20.6 % |
| Special operations materials | 103 million | 3640 million | 5.5 % |
| The Alamos | 74.1 million | 2610 million | 3.9 per cent |
| Research and development | 69.7 million | 2450 million | 3.7 % |
| Government expenditure | 37.3 million | 1310 million | 2.0 % |
| Heavy water plants | 26.8 million | 942 million | 1.4 % |
| Total | 1890 million | 66.5 billion |
Total expenditure for the project as of October 1, 1945, reached $1.845 billion, the equivalent of less than nine days of normal wartime expenditure, and reached $2.191 billion when the Commission on Atomic Power took over on January 1, 1947. The total budget was $2.4 billion. More than 90% of the cost was due to the construction of the plants and the production of the fissile materials, with less than 10% for the development and production of the weapons.
By the end of 1945, a total of four bombs had been produced (the Trinity test «instrument», the Little Boy bomb, the Fat Man bomb, and a unused fourth bomb), putting the average cost of a bomb at $500 million in 1945. By comparison, the total cost of the project at the end of 1945 was 90% of the total spent on weapons production small (not counting ammunition) by the United States and 34% of the total spent on American tanks during the same period. Taken together, it was the second most expensive weapons project undertaken by the United States in World War II, behind only the design and production of the Boeing B-29 Superfortress.
Legacy
The cultural and political impact of the development of nuclear weapons is considered profound and far-reaching. William L. Laurence of The New York Times, the first person to use the expression "atomic age", became the official correspondent for the Manhattan Project in the spring of 1945. In 1943 and 1944 he had attempted to unsuccessfully persuading the Bureau of Censorship to allow him to write about the explosive potential of uranium, so government officials felt he had won the right to report on the war's biggest secret. Laurence witnessed both the Trinity test and the bombing of Nagasaki and wrote the official press releases for both events. He subsequently wrote a series of articles praising the virtues of the new weapon. His articles before and after the bombings helped publicize the potential of nuclear technology and were one of the motivations for its development in the United States and the Soviet Union.
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The Manhattan Project left a legacy in the form of a network of national laboratories: Lawrence Berkeley National Laboratory, Los Alamos National Laboratory, Oak Ridge National Laboratory, Argonne National Laboratory, and Ames Laboratory. Groves established two more shortly after the war, the Brookhaven National Laboratory in Upton, New York, and the Sandia National Laboratories in Albuquerque. Groves allocated $72 million for research activities in fiscal year 1946–1947. This network of laboratories was at the forefront of large-scale investigations known as "Big Science," a term coined by Alvin Weinberg, director of the Laboratory. Oak Ridge National.
The Naval Research Laboratory had been interested in the possibility of using nuclear energy to power warships for some time, so it tried to create its own nuclear project. In May 1946 Chester Nimitz, by then Chief of Naval Operations, decided that the Navy should work in conjunction with the Manhattan Project. He assigned a group of naval officers to Oak Ridge, the most senior being Captain Hyman G. Rickover, who became assistant director there. These officers focused on the study of nuclear power, laying the foundation for a nuclear weapon. A similar group of Air Force personnel arrived at Oak Ridge in September 1946 with the intention of developing nuclear aircraft. Nuclear Energy for the Propulsion of Aircraft (NEPA) faced great technical difficulties and was eventually cancelled.
The ability of new reactors to create radioactive isotopes in previously impossible amounts ignited a revolution in nuclear medicine in the immediate post-war years. Beginning in mid-1946, Oak Ridge began distributing radioisotopes to hospitals and universities. Most of the orders were for iodine-131 and phosphorus-32, used in the diagnosis and treatment of cancer. In addition to medicine, these types of isotopes have been used in biological, industrial, and agricultural research.
At the time of relinquishing control of nuclear weapons to the Atomic Energy Commission, Groves gave a valedictory speech to personnel who had worked on the Manhattan Project:
Five years ago, the idea of atomic energy was just a dream. You made this dream a reality. You took over some of the most confusing ideas and translated them into realities. You built cities where none were known before. You built industrial plants of a magnitude and with precision that was previously considered impossible. You built the weapon that ended the war and therefore saved countless American lives. With regard to applications in times of peace, you raised the curtain for the vision of a new world.
In 2014, the United States Congress passed a law creating a national park dedicated to the history of the Manhattan Project, finally created as the Manhattan Project National Historical Park on November 10, 2015.