Portal:Nuclear technology/Articles

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On 21 January 1968, an aircraft accident, sometimes known as the Thule affair or Thule accident (/ˈtuːli/; Danish: Thuleulykken), involving a United States Air Force (USAF) B-52 bomber occurred near Thule Air Base in the Danish territory of Greenland. The aircraft was carrying four B28FI thermonuclear bombs on a Cold War "Chrome Dome" alert mission over Baffin Bay when a cabin fire forced the crew to abandon the aircraft before they could carry out an emergency landing at Thule Air Base. Six crew members ejected safely, but one who did not have an ejection seat was killed while trying to bail out. The bomber crashed onto sea ice in North Star Bay, Greenland, causing the conventional explosives aboard to detonate and the nuclear payload to rupture and disperse, resulting in radioactive contamination of the area.

The United States and Denmark launched an intensive clean-up and recovery operation, but the secondary stage of one of the nuclear weapons could not be accounted for after the operation was completed. USAF Strategic Air Command "Chrome Dome" operations were discontinued immediately after the accident, which highlighted the safety and political risks of the missions. Safety procedures were reviewed, and more stable explosives were developed for use in nuclear weapons.

In 1995, a political scandal arose in Denmark after a report revealed the government had given tacit permission for nuclear weapons to be located in Greenland, in contravention of Denmark's 1957 nuclear-free zone policy. Workers involved in the clean-up program campaigned for compensation for radiation-related illnesses they experienced in the years after the accident. (Full article...)

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The Alsos Mission was an organized effort by a team of British and United States military, scientific, and intelligence personnel to discover enemy scientific developments during World War II. Its chief focus was on the German nuclear energy project, but it also investigated chemical and biological weapons and the means to deliver them.

The Alsos Mission was created after the September 1943 Allied invasion of Italy as part of the Manhattan Project's mission to coordinate foreign intelligence related to enemy nuclear activity. The team had a twofold assignment: search for personnel, records, material, and sites to evaluate the above programs and prevent their capture by the Soviet Union. Alsos personnel followed close behind the front lines in Italy, France, and Germany, occasionally crossing into enemy-held territory to secure valuable resources before they could be destroyed or scientists escape or fall into rival hands.

The Alsos Mission was commanded by Colonel Boris Pash, a former Manhattan Project security officer, with Samuel Goudsmit as chief scientific advisor. It was jointly staffed by the Office of Naval Intelligence (ONI), the Office of Scientific Research and Development (OSRD), the Manhattan Project, and Army Intelligence (G-2), with field assistance from combat engineers assigned to specific task forces.

Alsos teams were successful in locating and removing a substantial portion of the German research effort's surviving records and equipment. They also took most of the senior German research personnel into custody, including Otto Hahn, Max von Laue, Werner Heisenberg and Carl Friedrich von Weizsäcker. (Full article...)

Portal:Nuclear technology/Articles/3 The Ames Project was a research and development project that was part of the larger Manhattan Project to build the first atomic bombs during World War II. It was founded by Frank Spedding from Iowa State College in Ames, Iowa as an offshoot of the Metallurgical Laboratory at the University of Chicago devoted to chemistry and metallurgy, but became a separate project in its own right. The Ames Project developed the Ames Process, a method for preparing pure uranium metal that the Manhattan Project needed for its atomic bombs and nuclear reactors. Between 1942 and 1945, it produced over 1,000 short tons (910 t) of uranium metal. It also developed methods of preparing and casting thorium, cerium and beryllium. In October 1945 Iowa State College received the Army-Navy "E" Award for Excellence in Production, an award usually only given to industrial organizations. In 1947 it became the Ames Laboratory, a national laboratory under the Atomic Energy Commission. (Full article...)

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Britain initiated the first research project to design an atomic bomb in 1941 and helped the United States to recognise how important this type of research was and get the Manhattan Project started in 1942 as well as contributing to carrying this through to successful completion in August 1945 by supplying crucial expertise to the project.

Following the discovery of nuclear fission in uranium, scientists Rudolf Peierls and Otto Frisch at the University of Birmingham calculated, in March 1940, that the critical mass of a metallic sphere of pure uranium-235 was as little as 1 to 10 kilograms (2.2 to 22.0 lb), and would explode with the power of thousands of tons of dynamite. The Frisch–Peierls memorandum prompted Britain to create an atomic bomb project, known as Tube Alloys. Mark Oliphant, an Australian physicist working in Britain, was instrumental in making the results of the British MAUD Report known in the United States in 1941 by a visit in person. Initially the British project was larger and more advanced, but after the United States entered the war, the American project soon outstripped and dwarfed its British counterpart. The British government then decided to shelve its own nuclear ambitions, and participate in the American project.

In August 1943, the Prime Minister of the United Kingdom, Winston Churchill, and the President of the United States, Franklin D. Roosevelt, signed the Quebec Agreement, which provided for cooperation between the two countries. At this point, British research into the physics required for a bomb was more advanced. The Quebec Agreement established the Combined Policy Committee and the Combined Development Trust to coordinate the efforts of the United States, the United Kingdom and Canada. The subsequent Hyde Park Agreement in September 1944 extended this cooperation to the postwar period. A British Mission led by Wallace Akers assisted in the development of gaseous diffusion technology in New York. Britain also produced the powdered nickel required by the gaseous diffusion process. Another mission, led by Oliphant who acted as deputy director at the Berkeley Radiation Laboratory, assisted with the electromagnetic separation process. As head of the British Mission to the Los Alamos Laboratory, James Chadwick led a multinational team of distinguished scientists that included Sir Geoffrey Taylor, James Tuck, Niels Bohr, Peierls, Frisch, and Klaus Fuchs, who was later revealed to be a Soviet atomic spy. Four members of the British Mission became group leaders at Los Alamos. William Penney observed the bombing of Nagasaki and participated in the Operation Crossroads nuclear tests in 1946.

Cooperation ended with the Atomic Energy Act of 1946, known as the McMahon Act, and Ernest Titterton, the last British government employee, left Los Alamos on 12 April 1947. Britain then proceeded with High Explosive Research, its own nuclear weapons programme, and became the third country to test an independently developed nuclear weapon in October 1952. (Full article...)

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Chicago Pile-1 (CP-1) was the world's first artificial nuclear reactor. On 2 December 1942, the first human-made self-sustaining nuclear chain reaction was initiated in CP-1 during an experiment led by Enrico Fermi. The secret development of the reactor was the first major technical achievement for the Manhattan Project, the Allied effort to create nuclear weapons during World War II. Developed by the Metallurgical Laboratory at the University of Chicago, CP-1 was built under the west viewing stands of the original Stagg Field. Although the project's civilian and military leaders had misgivings about the possibility of a disastrous runaway reaction, they trusted Fermi's safety calculations and decided they could carry out the experiment in a densely populated area. Fermi described the reactor as "a crude pile of black bricks and wooden timbers".

After a series of attempts, the successful reactor was assembled in November 1942 by a team of about 30 that, in addition to Fermi, included scientists Leo Szilard (who had previously formulated an idea for non-fission chain reaction), Leona Woods, Herbert L. Anderson, Walter Zinn, Martin D. Whitaker, and George Weil. The reactor used natural uranium. This required a very large amount of material in order to reach criticality, along with graphite used as a neutron moderator. The reactor contained 45,000 ultra-pure graphite blocks weighing 360 short tons (330 tonnes) and was fueled by 5.4 short tons (4.9 tonnes) of uranium metal and 45 short tons (41 tonnes) of uranium oxide. Unlike most subsequent nuclear reactors, it had no radiation shielding or cooling system as it operated at very low power – about one-half watt.

The pursuit of a reactor had been touched off by concern that Nazi Germany had a substantial scientific lead. The success of Chicago Pile-1 provided the first vivid demonstration of the feasibility of the military use of nuclear energy by the Allies, as well as the reality of the danger that Nazi Germany could succeed in producing nuclear weapons. Previously, estimates of critical masses had been crude calculations, leading to order-of-magnitude uncertainties about the size of a hypothetical bomb. The successful use of graphite as a moderator paved the way for progress in the Allied effort, whereas the German program languished partly because of the belief that scarce and expensive heavy water would have to be used for that purpose. The Germans had failed to account for the importance of boron and cadmium impurities in the graphite samples on which they ran their test of its usability as a moderator, while Leo Szilard and Enrico Fermi had asked suppliers about the most common contaminations of graphite after a first failed test. They consequently ensured that the next test would be run with graphite entirely devoid of them. As it turned out, both boron and cadmium were strong neutron poisons.

In 1943, CP-1 was moved to Site A, a wartime research facility outside Chicago, where it was reconfigured to become Chicago Pile-2 (CP-2). There, it was operated for research until 1954, when it was dismantled and buried. The stands at Stagg Field were demolished in August 1957; the site is now a National Historic Landmark and a Chicago Landmark. (Full article...)

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The Clinton Engineer Works (CEW) was the production installation of the Manhattan Project that during World War II produced the enriched uranium used in the 1945 bombing of Hiroshima, as well as the first examples of reactor-produced plutonium. It consisted of production facilities arranged at three major sites, various utilities including a power plant, and the town of Oak Ridge. It was in East Tennessee, about 18 miles (29 km) west of Knoxville, and was named after the town of Clinton, eight miles (13 km) to the north. The production facilities were mainly in Roane County, and the northern part of the site was in Anderson County. The Manhattan District Engineer, Kenneth Nichols, moved the Manhattan District headquarters from Manhattan to Oak Ridge in August 1943. During the war, Clinton's advanced research was managed for the government by the University of Chicago.

Construction workers were housed in a community known as Happy Valley. Built by the Army Corps of Engineers in 1943, this temporary community housed 15,000 people. The township of Oak Ridge was established to house the production staff. The operating force peaked at 50,000 workers just after the end of the war. The construction labor force peaked at 75,000 and the combined employment peak was 80,000. The town was developed by the federal government as a segregated community; black residents lived only in an area known as Gamble Valley, in government-built "hutments" (one-room shacks) on the south side of what is now Tuskegee Drive. (Full article...)

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The Hanford Site is a decommissioned nuclear production complex operated by the United States federal government on the Columbia River in Benton County in the U.S. state of Washington. It has also been known as Site W and the Hanford Nuclear Reservation. Established in 1943 as part of the Manhattan Project, the site was home to the Hanford Engineer Works and B Reactor, the first full-scale plutonium production reactor in the world. Plutonium manufactured at the site was used in the first atomic bomb, which was tested in the Trinity nuclear test, and in the Fat Man bomb used in the bombing of Nagasaki.

During the Cold War, the project expanded to include nine nuclear reactors and five large plutonium processing complexes, which produced plutonium for most of the more than sixty thousand weapons built for the U.S. nuclear arsenal. Nuclear technology developed rapidly during this period, and Hanford scientists produced major technological achievements. The town of Richland, established by the Manhattan Project, became self-governing in 1958, and residents were able to purchase their properties. After sufficient plutonium had been produced, the production reactors were shut down between 1964 and 1971.

Many early safety procedures and waste disposal practices were inadequate, resulting in the release of significant amounts of radioactive materials into the air and the Columbia River, resulting in higher rates of cancer in the surrounding area. The Hanford Site became the focus of the nation's largest environmental cleanup. A citizen-led Hanford Advisory Board provides recommendations from community stakeholders, including local and state governments, regional environmental organizations, business interests, and Native American tribes. Cleanup activity was still ongoing in 2023, with over 10,000 workers employed on cleanup activities.

Hanford hosts a commercial nuclear power plant, the Columbia Generating Station, and various centers for scientific research and development, such as the Pacific Northwest National Laboratory, the Fast Flux Test Facility and the LIGO Hanford Observatory. In 2015 it was designated as part of the Manhattan Project National Historical Park. Tourists can visit the site and B Reactor. (Full article...)

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The British hydrogen bomb programme was the ultimately successful British effort to develop hydrogen bombs between 1952 and 1958.

During the early part of the Second World War, Britain had a nuclear weapons project, codenamed Tube Alloys. At the Quebec Conference in August 1943, British prime minister Winston Churchill and United States president Franklin Roosevelt signed the Quebec Agreement, merging Tube Alloys into the American Manhattan Project, in which many of Britain's top scientists participated. The British government trusted that America would share nuclear technology, which it considered to be a joint discovery, but the United States Atomic Energy Act of 1946 (also known as the McMahon Act) ended technical cooperation. Fearing a resurgence of American isolationism, and the loss of Britain's great power status, the British government resumed its own development effort, which was codenamed "High Explosive Research".

The successful nuclear test of a British atomic bomb in Operation Hurricane in October 1952 represented an extraordinary scientific and technological achievement. Britain became the world's third nuclear power, reaffirming the country's status as a great power, but hopes that the United States would be sufficiently impressed to restore the nuclear Special Relationship were soon dashed. In November 1952, the United States conducted the first successful test of a true thermonuclear device or hydrogen bomb. Britain was therefore still several years behind in nuclear weapons technology. The Defence Policy Committee, chaired by Churchill and consisting of the senior Cabinet members, considered the political and strategic implications in June 1954, and concluded that "we must maintain and strengthen our position as a world power so that Her Majesty's Government can exercise a powerful influence in the counsels of the world." In July 1954, Cabinet agreed to proceed with the development of thermonuclear weapons. (Full article...)

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The Manhattan Project was a program of research and development undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and with support from Canada. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the U.S. Army Corps of Engineers. The nuclear physicist J. Robert Oppenheimer was the director of the Los Alamos Laboratory that designed the bombs. The Army component was designated the Manhattan District, as its first headquarters were in Manhattan; the name gradually superseded the official codename, Development of Substitute Materials, for the entire project. The project absorbed its earlier British counterpart, Tube Alloys. The Manhattan Project grew rapidly and employed nearly 130,000 people at its peak and cost nearly US$2 billion (equivalent to about $24 billion in 2021). Over 90 percent of the cost was for building factories and to produce fissile material, with less than 10 percent for development and production of the weapons. Research and production took place at more than 30 sites across the United States, the United Kingdom, and Canada.

The project led to the development of two types of atomic bombs, both developed concurrently, during the war: a relatively simple gun-type fission weapon and a more complex implosion-type nuclear weapon. The Thin Man gun-type design proved impractical to use with plutonium, so a simpler gun-type design called Little Boy was developed that used uranium-235. Three methods were employed for uranium enrichment: electromagnetic, gaseous and thermal. In parallel with the work on uranium was an effort to produce plutonium. After the feasibility of the world's first artificial nuclear reactor, the Chicago Pile-1, was demonstrated in 1942 at the Metallurgical Laboratory in the University of Chicago, the project designed the X-10 Graphite Reactor and the production reactors at the Hanford Site, in which uranium was irradiated and transmuted into plutonium. The Fat Man plutonium implosion-type weapon was developed in a concerted design and development effort by the Los Alamos Laboratory.

The project was also charged with gathering intelligence on the German nuclear weapon project. Through Operation Alsos, Manhattan Project personnel served in Europe, sometimes behind enemy lines, where they gathered nuclear materials and documents, and rounded up German scientists. Despite the Manhattan Project's tight security, Soviet atomic spies successfully penetrated the program.

The first nuclear device ever detonated was an implosion-type bomb during the Trinity test, conducted at New Mexico's Alamogordo Bombing and Gunnery Range on 16 July 1945. Little Boy and Fat Man bombs were used a month later in the atomic bombings of Hiroshima and Nagasaki, respectively, with Manhattan Project personnel serving as bomb assembly technicians and weaponeers on the attack aircraft. In the immediate postwar years, the Manhattan Project conducted weapons testing at Bikini Atoll as part of Operation Crossroads, developed new weapons, promoted the development of the network of national laboratories, supported medical research into radiology and laid the foundations for the nuclear navy. It maintained control over American atomic weapons research and production until the formation of the United States Atomic Energy Commission (UNAEC) in January 1947. (Full article...)

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The Metallurgical Laboratory (or Met Lab) was a scientific laboratory at the University of Chicago that was established in February 1942 to study and use the newly discovered chemical element plutonium. It researched plutonium's chemistry and metallurgy, designed the world's first nuclear reactors to produce it, and developed chemical processes to separate it from other elements. In August 1942 the lab's chemical section was the first to chemically separate a weighable sample of plutonium, and on 2 December 1942, the Met Lab produced the first controlled nuclear chain reaction, in the reactor Chicago Pile-1, which was constructed under the stands of the university's old football stadium, Stagg Field.

The Metallurgical Laboratory was established as part of the Metallurgical Project, also known as the "Pile" or "X-10" Project, headed by Chicago professor Arthur H. Compton, a Nobel Prize laureate. In turn, this was part of the Manhattan Project – the Allied effort to develop the atomic bomb during World War II. The Metallurgical Laboratory was successively led by Richard L. Doan, Samuel K. Allison, Joyce C. Stearns and Farrington Daniels. Scientists who worked there included Enrico Fermi, James Franck, Eugene Wigner and Glenn Seaborg. At its peak on 1 July 1944, it had 2,008 staff.

Chicago Pile-1 was soon moved by the lab to Site A, a more remote location in the Argonne Forest preserves, where the original materials were used to build an improved Chicago Pile-2 to be employed in new research into the products of nuclear fission. Another reactor, Chicago Pile-3, was built at the Argonne site in early 1944. This was the world's first reactor to use heavy water as a neutron moderator. It went critical in May 1944, and was first operated at full power in July 1944. The Metallurgical Laboratory also designed the X-10 Graphite Reactor at the Clinton Engineer Works in Oak Ridge, Tennessee, and the B Reactor at the Hanford Engineer Works in the state of Washington.

As well as the work on reactor development, the Metallurgical Laboratory studied the chemistry and metallurgy of plutonium, and worked with DuPont to develop the bismuth phosphate process used to separate plutonium from uranium. When it became certain that nuclear reactors would involve radioactive materials on a gigantic scale, there was considerable concern about the health and safety aspects, and the study of the biological effects of radiation assumed greater importance. It was discovered that plutonium, like radium, was a bone seeker, making it especially hazardous. The Metallurgical Laboratory became the first of the national laboratories, the Argonne National Laboratory, on 1 July 1946. The work of the Met Lab also led to the creation of the Enrico Fermi Institute and the James Franck Institute at the university. (Full article...)

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The Montreal Laboratory in Montreal, Quebec, Canada, was established by the National Research Council of Canada during World War II to undertake nuclear research in collaboration with the United Kingdom, and to absorb some of the scientists and work of the Tube Alloys nuclear project in Britain. It became part of the Manhattan Project, and designed and built some of the world's first nuclear reactors.

After the Fall of France, some French scientists escaped to Britain with their stock of heavy water. They were temporarily installed in the Cavendish Laboratory at the University of Cambridge, where they worked on reactor design. The MAUD Committee was uncertain whether this was relevant to the main task of Tube Alloys, that of building an atomic bomb, although there remained a possibility that a reactor could be used to breed plutonium, which might be used in one. It therefore recommended that they be relocated to the United States, and co-located with the Manhattan Project's reactor effort. Due to American concerns about security (many of the scientists were foreign nationals) and patent claims by the French scientists and Imperial Chemical Industries (ICI), it was decided to relocate them to Canada instead.

The Canadian government agreed to the proposal, and the Montreal Laboratory was established in a house belonging to McGill University; it moved to permanent accommodation at the Université de Montréal in March 1943. The first eight laboratory staff arrived in Montreal at the end of 1942. These were Bertrand Goldschmidt and Pierre Auger from France, George Placzek from Czechoslovakia, S. G. Bauer from Switzerland, Friedrich Paneth and Hans von Halban from Austria, and R. E. Newell and F. R. Jackson from Britain. The Canadian contingent included George Volkoff, Bernice Weldon Sargent and George Laurence, and promising young Canadian scientists such as J. Carson Mark, Phil Wallace and Leo Yaffe.

Although Canada was a major source of uranium ore and heavy water, these were controlled by the Americans. Anglo-American cooperation broke down, denying the Montreal Laboratory scientists access to the materials they needed to build a reactor. In 1943, the Quebec Agreement merged Tube Alloys with the American Manhattan Project. The Americans agreed to help build the reactor. Scientists who were not British subjects left, and John Cockcroft became the new director of the Montreal Laboratory in May 1944. The Chalk River Laboratories opened in 1944, and the Montreal Laboratory was closed in July 1946. Two reactors were built at Chalk River. The small ZEEP went critical on 5 September 1945, and the larger NRX on 21 July 1947. NRX was for a time the most powerful research reactor in the world. (Full article...)

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The Windscale Piles were two air-cooled graphite-moderated nuclear reactors on the Windscale nuclear site in Cumberland (now known as Sellafield site, Cumbria) on the north-west coast of England. The two reactors, referred to at the time as "piles", were built as part of the British post-war atomic bomb project and produced weapons-grade plutonium for use in nuclear weapons.

Windscale Pile No. 1 became operational in October 1950 followed by Pile No. 2 in June 1951. They were intended to last five years, but operated for seven until shut down following the Windscale fire on 10 October 1957. Nuclear decommissioning operations commenced in the 1980s and are estimated to last beyond 2040. Visible changes have been seen as the chimneys were slowly dismantled from top-down; Pile 2's chimney being reduced to the height of adjacent buildings in the early 2000s. However, the demolition of pile 1 chimney has taken much longer as it was significantly contaminated after the 1957 fire. The reactor cores still remain to be dismantled. (Full article...)

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Following the success of Operation Grapple in which the United Kingdom became the third nation to acquire thermonuclear weapons after the United States and the Soviet Union, Britain launched negotiations with the US on a treaty under in which both could share information and material to design, test and maintain their nuclear weapons. This effort culminated in the 1958 US–UK Mutual Defence Agreement. One of the results of that treaty was that Britain was allowed to use United States' Nevada Test Site for testing their designs and ideas, and received full support from the personnel there, in exchange for the data "take" from the experiment, a mutual condition. In effect the Nevada Test Site became Britain's test ground, subject only to advance planning and integrating their testing into that of the United States. This resulted in 24 underground tests at the Nevada Test Site from 1958 through the end of nuclear testing in the US in September 1992.

The United Kingdom signed the Comprehensive Nuclear Test Ban Treaty in 1996 and ratified it in 1998, confirming the British commitment towards ending nuclear test explosions in the world. (Full article...)

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Operation Crossroads was a pair of nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. They were the first nuclear weapon tests since Trinity in July 1945, and the first detonations of nuclear devices since the atomic bombing of Nagasaki on August 9, 1945. The purpose of the tests was to investigate the effect of nuclear weapons on warships.

The Crossroads tests were the first of many nuclear tests held in the Marshall Islands, and the first to be publicly announced beforehand and observed by an invited audience, including a large press corps. They were conducted by Joint Army/Navy Task Force One, headed by Vice Admiral William H. P. Blandy rather than by the Manhattan Project, which had developed nuclear weapons during World War II. A fleet of 95 target ships was assembled in Bikini Lagoon and hit with two detonations of Fat Man plutonium implosion-type nuclear weapons of the kind dropped on Nagasaki in 1945, each with a yield of 23 kilotons of TNT (96 TJ).

The first test was Able. The bomb was named Gilda after Rita Hayworth's character in the 1946 film Gilda, and was dropped from the B-29 Superfortress Dave's Dream of the 509th Bombardment Group on July 1, 1946. It detonated 520 feet (158 m) above the target fleet and caused less than the expected amount of ship damage because it missed its aim point by 2,130 feet (649 m).

The second test was Baker. The bomb was known as Helen of Bikini and was detonated 90 feet (27 m) underwater on July 25, 1946. Radioactive sea spray caused extensive contamination. A third deep-water test named Charlie was planned for 1947 but was canceled primarily because of the United States Navy's inability to decontaminate the target ships after the Baker test. Ultimately, only nine target ships were able to be scrapped rather than scuttled. Charlie was rescheduled as Operation Wigwam, a deep-water shot conducted in 1955 off the coast of Mexico (Baja California).

Bikini's native residents were evacuated from the island on board the LST-861, with most moving to the Rongerik Atoll. In the 1950s, a series of large thermonuclear tests rendered Bikini unfit for subsistence farming and fishing because of radioactive contamination. Bikini remains uninhabited , though it is occasionally visited by sport divers. Planners attempted to protect participants in the Operation Crossroads tests against radiation sickness, but one study showed that the life expectancy of participants was reduced by an average of three months. The Baker test's radioactive contamination of all the target ships was the first case of immediate, concentrated radioactive fallout from a nuclear explosion. Chemist Glenn T. Seaborg, the longest-serving chairman of the Atomic Energy Commission, called Baker "the world's first nuclear disaster." (Full article...)

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The Salt Wells Pilot Plant was a facility established by the Manhattan Project at the Naval Ordnance Test Station (NOTS) at Inyokern, California, where non-nuclear explosive components of nuclear weapons were manufactured. The first explosives were melted, mixed and poured on 25 July 1945. Between 1945 and 1954, it manufactured explosive components of the Fat Man, Mark 4, Mark 5 and Mark 12 nuclear bombs. The Salt Wells Pilot Plant also helped design, equip, and train workers for the Burlington AEC Plant in Iowa and the Pantex Plant in Texas. The Salt Wells Pilot Plant closed on 30 June 1954. (Full article...)

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The Oppenheimer security hearing conducted by the United States Atomic Energy Commission (AEC) over four weeks in 1954 explored the background, actions, and associations of J. Robert Oppenheimer, the American scientist who directed the Los Alamos Laboratory during World War II as part of the Manhattan Project to develop the atomic bomb. The hearing resulted in Oppenheimer's Q clearance being revoked. This marked the end of his formal relationship with the government of the United States, and generated considerable controversy regarding whether the treatment of Oppenheimer was fair, or whether it was an expression of anti-communist McCarthyism.

Doubts about Oppenheimer's loyalty dated back to the 1930s, when he was a member of numerous Communist front organizations, and was associated with Communist Party USA members, including his wife, brother and sister-in-law. These associations were known to Army Counterintelligence at the time he was made director of the Los Alamos Laboratory in 1942, and chairman of the influential General Advisory Committee of the AEC in 1947. In this capacity, Oppenheimer became involved in bureaucratic conflict between the Army and Air Force over the types of nuclear weapons the country required, technical conflict between the scientists over the feasibility of the hydrogen bomb, and personal conflict with AEC commissioner Lewis Strauss.

The proceedings were initiated after Oppenheimer refused to voluntarily give up his security clearance while working as an atomic weapons consultant for the government, under a contract due to expire at the end of June 1954. Several of his colleagues testified at the hearings. As a result of the two-to-one decision of the hearing's three judges, he was stripped of his security clearance one day before his consultant contract was due to expire. The panel found that he was loyal and discreet with atomic secrets, but did not recommend that his security clearance be reinstated.

The loss of his security clearance ended Oppenheimer's role in government and policy. He became an academic exile, cut off from his former career and the world he had helped to create. The reputations of those who had testified against Oppenheimer were tarnished as well, though Oppenheimer's reputation was later partly rehabilitated by Presidents John F. Kennedy and Lyndon B. Johnson. The brief period when scientists were viewed as a "public policy priesthood" ended, and thereafter would serve the state only to offer narrow scientific opinions. Scientists working in government were on notice that dissent was no longer tolerated.

The fairness of the proceedings has been a subject of controversy, and on December 16, 2022, United States Secretary of Energy Jennifer Granholm nullified the 1954 decision, saying that it had been the result of a "flawed process" and affirming that Oppenheimer had been loyal. (Full article...)

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Project E was a joint project between the United States and the United Kingdom during the Cold War to provide nuclear weapons to the Royal Air Force (RAF) until sufficient British nuclear weapons became available. It was subsequently expanded to provide similar arrangements for the British Army of the Rhine. A maritime version of Project E known as Project N provided nuclear depth bombs used by the RAF Coastal Command.

The British nuclear weapons project, High Explosive Research, successfully tested a nuclear weapon in Operation Hurricane in October 1952, but production was slow and Britain had only ten atomic bombs on hand in 1955 and fourteen in 1956. The Prime Minister of the United Kingdom, Winston Churchill, approached the President of the United States, Dwight D. Eisenhower, with a request that the US supply nuclear weapons for the strategic bombers of the V bomber fleet until sufficient British weapons became available. This became known as Project E. Under an agreement reached in 1957, US personnel had custody of the weapons, and performed all tasks related to their storage, maintenance and readiness. The bombs were held in secure storage areas (SSAs) on the same bases as the bombers.

The first bombers equipped with Project E weapons were English Electric Canberras based in Germany and the UK that were assigned to NATO. These were replaced by Vickers Valiants in 1960 and 1961 as the long-range Avro Vulcan and Handley Page Victor assumed the strategic nuclear weapon delivery role. Project E weapons equipped V-bombers at three bases in the UK from 1958. Due to operational restrictions imposed by Project E, and the consequential loss of independence of half of the British nuclear deterrent, they were phased out in 1962 when sufficient British megaton weapons became available, but remained in use with the Valiants in the UK and RAF Germany until 1965.

Project E nuclear warheads were used on the sixty Thor Intermediate Range Ballistic Missiles operated by the RAF from 1959 to 1963 under Project Emily. The British Army acquired Project E warheads for its Corporal missiles in 1958. The US subsequently offered the Honest John missile as a replacement. They remained in service until 1977 when Honest John was superseded by the Lance missile. Eight-inch and 155 mm nuclear artillery rounds were also acquired under Project E. The last Project E weapons were withdrawn from service in 1992. (Full article...)

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Uranium is a chemical element with symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium radioactively decays by emitting an alpha particle. The half-life of this decay varies between 159,200 and 4.5 billion years for different isotopes, making them useful for dating the age of the Earth. The most common isotopes in natural uranium are uranium-238 (which has 146 neutrons and accounts for over 99% of uranium on Earth) and uranium-235 (which has 143 neutrons). Uranium has the highest atomic weight of the primordially occurring elements. Its density is about 70% higher than that of lead, and slightly lower than that of gold or tungsten. It occurs naturally in low concentrations of a few parts per million in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite.

Many contemporary uses of uranium exploit its unique nuclear properties. Uranium-235 is the only naturally occurring fissile isotope, which makes it widely used in nuclear power plants and nuclear weapons. However, because of the extreme scarcity of concentrations of uranium-235 in naturally occurring uranium (which is, overwhelmingly, mostly uranium-238), uranium needs to undergo enrichment so that enough uranium-235 is present. Uranium-238 is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissile plutonium-239 in a nuclear reactor. Another fissile isotope, uranium-233, can be produced from natural thorium and is studied for future industrial use in nuclear technology. Uranium-238 has a small probability for spontaneous fission or even induced fission with fast neutrons; uranium-235, and to a lesser degree uranium-233, have a much higher fission cross-section for slow neutrons. In sufficient concentration, these isotopes maintain a sustained nuclear chain reaction. This generates the heat in nuclear power reactors, and produces the fissile material for nuclear weapons. Depleted uranium (²³⁸U) is used in kinetic energy penetrators and armor plating.

The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth, who named the new element after the recently discovered planet Uranus. Eugène-Melchior Péligot was the first person to isolate the metal, and its radioactive properties were discovered in 1896 by Henri Becquerel. Research by Otto Hahn, Lise Meitner, Enrico Fermi and others, such as J. Robert Oppenheimer starting in 1934 led to its use as a fuel in the nuclear power industry and in Little Boy, the first nuclear weapon used in war. An ensuing arms race during the Cold War between the United States and the Soviet Union produced tens of thousands of nuclear weapons that used uranium metal and uranium-derived plutonium-239. Dismantling of these weapons and related nuclear facilities is carried out within various nuclear disarmament programs and costs billions of dollars. Weapon-grade uranium obtained from nuclear weapons is diluted with uranium-238 and reused as fuel for nuclear reactors. The development and deployment of these nuclear reactors continue on a global base as they are powerful sources of CO₂-free energy. Spent nuclear fuel forms radioactive waste, which mostly consists of uranium-238 and poses significant health threat and environmental impact. (Full article...)

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The Los Alamos Laboratory, also known as Project Y, was a secret laboratory established by the Manhattan Project and operated by the University of California during World War II. Its mission was to design and build the first atomic bombs. Robert Oppenheimer was its first director, serving from 1943 to December 1945, when he was succeeded by Norris Bradbury. In order to enable scientists to freely discuss their work while preserving security, the laboratory was located in a remote part of New Mexico. The wartime laboratory occupied buildings that had once been part of the Los Alamos Ranch School.

The development effort initially concentrated on a gun-type fission weapon using plutonium called Thin Man. In April 1944, the Los Alamos Laboratory determined that the rate of spontaneous fission in plutonium bred in a nuclear reactor was too great due to the presence of plutonium-240 and would cause a predetonation, a nuclear chain reaction before the core was fully assembled. Oppenheimer then reorganized the laboratory and orchestrated an all-out and ultimately successful effort on an alternative design proposed by John von Neumann, an implosion-type nuclear weapon, which was called Fat Man. A variant of the gun-type design known as Little Boy was developed using uranium-235.

Chemists at the Los Alamos Laboratory developed methods of purifying uranium and plutonium, the latter a metal that only existed in microscopic quantities when Project Y began. Its metallurgists found that plutonium had unexpected properties, but were nonetheless able to cast it into metal spheres. The laboratory built the Water Boiler, an aqueous homogeneous reactor that was the third reactor in the world to become operational. It also researched the Super, a hydrogen bomb that would use a fission bomb to ignite a nuclear fusion reaction in deuterium and tritium.

The Fat Man design was tested in the Trinity nuclear test in July 1945. Project Y personnel formed pit crews and assembly teams for the atomic bombings of Hiroshima and Nagasaki and participated in the bombing as weaponeers and observers. After the war ended, the laboratory supported the Operation Crossroads nuclear tests at Bikini Atoll. A new Z Division was created to control testing, stockpiling and bomb assembly activities, which were concentrated at Sandia Base. The Los Alamos Laboratory became Los Alamos Scientific Laboratory in 1947. (Full article...)

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The S-50 Project was the Manhattan Project's effort to produce enriched uranium by liquid thermal diffusion during World War II. It was one of three technologies for uranium enrichment pursued by the Manhattan Project.

The liquid thermal diffusion process was not one of the enrichment technologies initially selected for use in the Manhattan Project, and was developed independently by Philip H. Abelson and other scientists at the United States Naval Research Laboratory. This was primarily due to doubts about the process's technical feasibility, but inter-service rivalry between the United States Army and United States Navy also played a part.

Pilot plants were built at the Anacostia Naval Air Station and the Philadelphia Navy Yard, and a production facility at the Clinton Engineer Works in Oak Ridge, Tennessee. This was the only production-scale liquid thermal diffusion plant ever built. It could not enrich uranium sufficiently for use in an atomic bomb, but it could provide slightly enriched feed for the Y-12 calutrons and the K-25 gaseous diffusion plants. It was estimated that the S-50 plant had sped up production of enriched uranium used in the Little Boy bomb employed in the atomic bombing of Hiroshima by a week.

The S-50 plant ceased production in September 1945, but it was reopened in May 1946, and used by the United States Army Air Forces Nuclear Energy for the Propulsion of Aircraft (NEPA) project. The plant was demolished in the late 1940s. (Full article...)

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On 29 August 2007, six AGM-129 ACM cruise missiles, each loaded with a W80-1 variable yield nuclear warhead, were mistakenly loaded onto a United States Air Force (USAF) B-52H heavy bomber at Minot Air Force Base in North Dakota and transported to Barksdale Air Force Base in Louisiana. The nuclear warheads in the missiles were supposed to have been removed before the missiles were taken from their storage bunker. The missiles with the nuclear warheads were not reported missing and remained mounted to the aircraft at both Minot and Barksdale for 36 hours. During this period, the warheads were not protected by the various mandatory security precautions for nuclear weapons.

The incident was reported to the top levels of the United States military and referred to by observers as a Bent Spear incident, which indicates a nuclear weapon incident below the more severe Broken Arrow tier.

In response to the incident, the United States Department of Defense (DoD) and USAF conducted an investigation, the results of which were released on 19 October 2007. The investigation concluded that nuclear weapons handling standards and procedures had not been followed by numerous USAF personnel involved in the incident. As a result, four USAF commanders were relieved of their commands, numerous other USAF personnel were disciplined or decertified to perform certain types of sensitive duties, and further cruise missile transport missions from—and nuclear weapons operations at—Minot Air Force Base were suspended. In addition, the USAF issued new nuclear weapons handling instructions and procedures.

Separate investigations by the Defense Science Board and a USAF "blue ribbon" panel reported that concerns existed on the procedures and processes for handling nuclear weapons within the Department of Defense but did not find any failures with the security of United States nuclear weapons. Based on this and other incidents, on 5 June 2008, Secretary of the Air Force Michael Wynne and Chief of Staff of the Air Force General T. Michael Moseley were asked for their resignations, which they gave. In October 2008, in response to recommendations by a review committee, the USAF announced the creation of Air Force Global Strike Command to control all USAF nuclear bombers, missiles, and personnel. (Full article...)

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Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen, silicon, and hydrogen. When exposed to moist air, it forms oxides and hydrides that can expand the sample up to 70% in volume, which in turn flake off as a powder that is pyrophoric. It is radioactive and can accumulate in bones, which makes the handling of plutonium dangerous.

Plutonium was first synthetically produced and isolated in late 1940 and early 1941, by a deuteron bombardment of uranium-238 in the 1.5-metre (60 in) cyclotron at the University of California, Berkeley. First, neptunium-238 (half-life 2.1 days) was synthesized, which subsequently beta-decayed to form the new element with atomic number 94 and atomic weight 238 (half-life 88 years). Since uranium had been named after the planet Uranus and neptunium after the planet Neptune, element 94 was named after Pluto, which at the time was considered to be a planet as well. Wartime secrecy prevented the University of California team from publishing its discovery until 1948.

Plutonium is the element with the highest atomic number to occur in nature. Trace quantities arise in natural uranium-238 deposits when uranium-238 captures neutrons emitted by decay of other uranium-238 atoms.

Both plutonium-239 and plutonium-241 are fissile, meaning that they can sustain a nuclear chain reaction, leading to applications in nuclear weapons and nuclear reactors. Plutonium-240 exhibits a high rate of spontaneous fission, raising the neutron flux of any sample containing it. The presence of plutonium-240 limits a plutonium sample's usability for weapons or its quality as reactor fuel, and the percentage of plutonium-240 determines its grade (weapons-grade, fuel-grade, or reactor-grade). Plutonium-238 has a half-life of 87.7 years and emits alpha particles. It is a heat source in radioisotope thermoelectric generators, which are used to power some spacecraft. Plutonium isotopes are expensive and inconvenient to separate, so particular isotopes are usually manufactured in specialized reactors.

Producing plutonium in useful quantities for the first time was a major part of the Manhattan Project during World War II that developed the first atomic bombs. The Fat Man bombs used in the Trinity nuclear test in July 1945, and in the bombing of Nagasaki in August 1945, had plutonium cores. Human radiation experiments studying plutonium were conducted without informed consent, and several criticality accidents, some lethal, occurred after the war. Disposal of plutonium waste from nuclear power plants and dismantled nuclear weapons built during the Cold War is a nuclear-proliferation and environmental concern. Other sources of plutonium in the environment are fallout from numerous above-ground nuclear tests, which are now banned. (Full article...)

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Silverplate was the code reference for the United States Army Air Forces' participation in the Manhattan Project during World War II. Originally the name for the aircraft modification project which enabled a B-29 Superfortress bomber to drop an atomic weapon, "Silverplate" eventually came to identify the training and operational aspects of the program as well. The original directive for the project had as its subject line "Silver Plated Project" but continued usage of the term shortened it to "Silverplate".

Testing began with scale models at the Naval Proving Ground in Dahlgren, Virginia, in August 1943. Modifications began on a prototype Silverplate B-29 known as the "Pullman" in November 1943, and it was used for bomb flight testing at Muroc Army Air Field in California commencing in March 1944. The testing resulted in further modifications to both the bombs and the aircraft.

Seventeen production Silverplate aircraft were ordered in August 1944 to allow the 509th Composite Group to train with the type of aircraft they would have to fly in combat, and for the 216th Army Air Forces Base Unit to test bomb configurations. These were followed by 28 more aircraft that were ordered in February 1945 for operational use by the 509th Composite Group. This batch included the aircraft which were used in the atomic bombings of Hiroshima and Nagasaki in August 1945. Including the Pullman B-29, 46 Silverplate B-29s were produced during and after World War II. An additional 19 Silverplate B-29s were ordered in July 1945, which were delivered between the end of the war and the end of 1947. Thus, 65 Silverplate B-29s were made.

The use of the Silverplate codename was discontinued after the war, but modifications continued under a new codename, Saddletree. Another 80 aircraft were modified under this program. The last group of B-29s was modified in 1953, but never saw further service. (Full article...)

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The Smyth Report (officially Atomic Energy for Military Purposes) is the common name of an administrative history written by American physicist Henry DeWolf Smyth about the Manhattan Project, the Allied effort to develop atomic bombs during World War II. The subtitle of the report is A General Account of the Development of Methods of Using Atomic Energy for Military Purposes. It was released to the public on August 12, 1945, just days after the atomic bombings of Hiroshima and Nagasaki on August 6 and 9.

Smyth was commissioned to write the report by Major General Leslie R. Groves, Jr., the director of the Manhattan Project. The Smyth Report was the first official account of the development of the atomic bombs and the basic physical processes behind them. It also served as an indication as to what information was declassified; anything in the Smyth Report could be discussed openly. For this reason, the Smyth Report focused heavily on information, such as basic nuclear physics, which was either already widely known in the scientific community or easily deducible by a competent scientist, and omitted details about chemistry, metallurgy, and ordnance. This would ultimately give a false impression that the Manhattan Project was all about physics.

The Smyth Report sold almost 127,000 copies in its first eight printings, and was on The New York Times best-seller list from mid-October 1945 until late January 1946. It has been translated into over 40 languages. (Full article...)

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Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is light silver and tarnishes olive gray when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high melting point. Thorium is an electropositive actinide whose chemistry is dominated by the +4 oxidation state; it is quite reactive and can ignite in air when finely divided.

All known thorium isotopes are unstable. The most stable isotope, ²³²Th, has a half-life of 14.05 billion years, or about the age of the universe; it decays very slowly via alpha decay, starting a decay chain named the thorium series that ends at stable ²⁰⁸Pb. On Earth, thorium and uranium are the only elements with no stable or nearly-stable isotopes that still occur naturally in large quantities as primordial elements. Thorium is estimated to be over three times as abundant as uranium in the Earth's crust, and is chiefly refined from monazite sands as a by-product of extracting rare-earth metals.

Thorium was discovered in 1828 by the Norwegian amateur mineralogist Morten Thrane Esmark and identified by the Swedish chemist Jöns Jacob Berzelius, who named it after Thor, the Norse god of thunder. Its first applications were developed in the late 19th century. Thorium's radioactivity was widely acknowledged during the first decades of the 20th century. In the second half of the century, thorium was replaced in many uses due to concerns about its radioactivity.

Thorium is still being used as an alloying element in TIG welding electrodes but is slowly being replaced in the field with different compositions. It was also material in high-end optics and scientific instrumentation, used in some broadcast vacuum tubes, and as the light source in gas mantles, but these uses have become marginal. It has been suggested as a replacement for uranium as nuclear fuel in nuclear reactors, and several thorium reactors have been built. Thorium is also used in strengthening magnesium, coating tungsten wire in electrical equipment, controlling the grain size of tungsten in electric lamps, high-temperature crucibles, and glasses including camera and scientific instrument lenses. Other uses for thorium include heat-resistant ceramics, aircraft engines, and in light bulbs. Ocean science has utilised ²³¹Pa/²³⁰Th isotope ratios to understand the ancient ocean. (Full article...)

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Trinity was the code name of the first detonation of a nuclear weapon, conducted by the United States Army at 5:29 a.m. MWT (11:29:21 GMT) on July 16, 1945, as part of the Manhattan Project.

The test was of an implosion-design plutonium bomb, nicknamed the "gadget", of the same design as the Fat Man bomb later detonated over Nagasaki, Japan, on August 9, 1945. Concerns about whether the complex Fat Man design would work led to a decision to conduct the first nuclear test. The code name "Trinity" was assigned by J. Robert Oppenheimer, the director of the Los Alamos Laboratory, inspired by the poetry of John Donne.

The test, both planned and directed by Kenneth Bainbridge, was conducted in the Jornada del Muerto desert about 35 miles (56 km) southeast of Socorro, New Mexico, on what was the Alamogordo Bombing and Gunnery Range (renamed the White Sands Proving Ground just before the test). The only structures originally in the immediate vicinity were the McDonald Ranch House and its ancillary buildings, which scientists used as a laboratory for testing bomb components. Fears of a fizzle prompted construction of "Jumbo", a steel containment vessel that could contain the plutonium, allowing it to be recovered; but ultimately Jumbo was not used in the test. On May 7, 1945, a rehearsal was conducted, during which 108 short tons (98 t) of high explosive spiked with radioactive isotopes was detonated.

Some 425 people were present on the weekend of the Trinity test. Observers included Vannevar Bush, James Chadwick, James B. Conant, Thomas Farrell, Enrico Fermi, Hans Bethe, Richard Feynman, Isidor Isaac Rabi, Leslie Groves, Robert Oppenheimer, Frank Oppenheimer, Geoffrey Taylor, Richard Tolman, Edward Teller, and John von Neumann. The Trinity bomb released the explosive energy of 25 kilotons of TNT (100 TJ) ± 2 kilotons of TNT (8.4 TJ), and a large cloud of fallout. Thousands of people lived closer to the test than would have been allowed under guidelines adopted for subsequent tests, but no one living near the test was evacuated before or afterward.

The test site was declared a National Historic Landmark district in 1965, and listed on the National Register of Historic Places the following year. (Full article...)

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United States of America v. Progressive, Inc., Erwin Knoll, Samuel Day, Jr., and Howard Morland, 467 F. Supp. 990 (W.D. Wis. 1979), was a lawsuit brought against The Progressive magazine by the United States Department of Energy (DOE) in 1979. A temporary injunction was granted against The Progressive to prevent the publication of an article written by activist Howard Morland that purported to reveal the "secret" of the hydrogen bomb. Though the information had been compiled from publicly available sources, the DOE claimed that it fell under the "born secret" clause of the Atomic Energy Act of 1954.

Although the case was filed in the Western District of Wisconsin, the judge there recused himself as a friend of the magazine. The case was therefore brought before Judge Robert W. Warren, a judge in the Eastern District of Wisconsin. Because of the sensitive nature of information at stake in the trial, two separate hearings were conducted, one in public, and the other in camera. The defendants, Morland and the editors of The Progressive, would not accept security clearances, as they would have had to sign non-disclosure agreements that would have put restraints on their free speech (including, significantly, in written form), and so were not present at the in camera hearings. Their lawyers did obtain clearances so that they could participate, but were forbidden from conveying anything they heard there to their clients.

The article was eventually published after the government lawyers dropped their case during the appeals process, calling it moot after other information was independently published. Despite its indecisive conclusion, law students still study the case, which "could have been a law school hypothetical designed to test the limits of the presumption of unconstitutionality attached to prior restraints". (Full article...)

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The X-10 Graphite Reactor is a decommissioned nuclear reactor at Oak Ridge National Laboratory in Oak Ridge, Tennessee. Formerly known as the Clinton Pile and X-10 Pile, it was the world's second artificial nuclear reactor (after Enrico Fermi's Chicago Pile-1), and the first designed and built for continuous operation. It was built during World War II as part of the Manhattan Project.

While Chicago Pile-1 demonstrated the feasibility of nuclear reactors, the Manhattan Project's goal of producing enough plutonium for atomic bombs required reactors a thousand times as powerful, along with facilities to chemically separate the plutonium bred in the reactors from uranium and fission products. An intermediate step was considered prudent. The next step for the plutonium project, codenamed X-10, was the construction of a semiworks where techniques and procedures could be developed and training conducted. The centerpiece of this was the X-10 Graphite Reactor. It was air-cooled, used nuclear graphite as a neutron moderator, and pure natural uranium in metal form for fuel.

DuPont commenced construction of the plutonium semiworks at the Clinton Engineer Works in Oak Ridge on February 2, 1943. The reactor went critical on November 4, 1943, and produced its first plutonium in early 1944. It supplied the Los Alamos Laboratory with its first significant amounts of plutonium, and its first reactor-bred product. Studies of these samples heavily influenced bomb design. The reactor and chemical separation plant provided invaluable experience for engineers, technicians, reactor operators, and safety officials who then moved on to the Hanford site. X-10 operated as a plutonium production plant until January 1945, when it was turned over to research activities, and the production of radioactive isotopes for scientific, medical, industrial and agricultural uses. It was shut down in 1963 and was designated a National Historic Landmark in 1965. (Full article...)

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Northeast of San Francisco, California, on 5 August 1950, a United States Air Force Boeing B-29 Superfortress bomber carrying a Mark 4 nuclear bomb crashed shortly after takeoff from Fairfield-Suisun Air Force Base with 20 men on board. Twelve men were killed in the crash, including the commander of the 9th Bombardment Wing, Brigadier General Robert F. Travis, and another seven were killed on the ground when the aircraft exploded. The base was later renamed for Travis. (Full article...)

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ZETA, short for Zero Energy Thermonuclear Assembly, was a major experiment in the early history of fusion power research. Based on the pinch plasma confinement technique, and built at the Atomic Energy Research Establishment in the United Kingdom, ZETA was larger and more powerful than any fusion machine in the world at that time. Its goal was to produce large numbers of fusion reactions, although it was not large enough to produce net energy.

ZETA went into operation in August 1957 and by the end of the month it was giving off bursts of about a million neutrons per pulse. Measurements suggested the fuel was reaching between 1 and 5 million kelvins, a temperature that would produce nuclear fusion reactions, explaining the quantities of neutrons being seen. Early results were leaked to the press in September 1957, and the following January an extensive review was released. Front-page articles in newspapers around the world announced it as a breakthrough towards unlimited energy, a scientific advance for Britain greater than the recently launched Sputnik had been for the Soviet Union.

US and Soviet experiments had also given off similar neutron bursts at temperatures that were not high enough for fusion. This led Lyman Spitzer to express his scepticism of the results, but his comments were dismissed by UK observers as jingoism. Further experiments on ZETA showed that the original temperature measurements were misleading; the bulk temperature was too low for fusion reactions to create the number of neutrons being seen. The claim that ZETA had produced fusion had to be publicly withdrawn, an embarrassing event that cast a chill over the entire fusion establishment. The neutrons were later explained as being the product of instabilities in the fuel. These instabilities appeared inherent to any similar design, and work on the basic pinch concept as a road to fusion power ended by 1961.

In spite of ZETA's failure to achieve fusion, the device went on to have a long experimental lifetime and produced numerous important advances in the field. In one line of development, the use of lasers to more accurately measure the temperature was tested on ZETA, and was later used to confirm the results of the Soviet tokamak approach. In another, while examining ZETA test runs it was noticed that the plasma self-stabilised after the power was turned off. This has led to the modern reversed field pinch concept. More generally, studies of the instabilities in ZETA have led to several important theoretical advances that form the basis of modern plasma theory. (Full article...)

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Beryllium is a chemical element with the symbol Be and atomic number 4. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to form minerals. Gemstones high in beryllium include beryl (aquamarine, emerald, red beryl) and chrysoberyl. It is a relatively rare element in the universe, usually occurring as a product of the spallation of larger atomic nuclei that have collided with cosmic rays. Within the cores of stars, beryllium is depleted as it is fused into heavier elements. Beryllium constitutes about 0.0004 percent by mass of Earth's crust. The world's annual beryllium production of 220 tons is usually manufactured by extraction from the mineral beryl, a difficult process because beryllium bonds strongly to oxygen.

In structural applications, the combination of high flexural rigidity, thermal stability, thermal conductivity and low density (1.85 times that of water) make beryllium metal a desirable aerospace material for aircraft components, missiles, spacecraft, and satellites. Because of its low density and atomic mass, beryllium is relatively transparent to X-rays and other forms of ionizing radiation; therefore, it is the most common window material for X-ray equipment and components of particle detectors. When added as an alloying element to aluminium, copper (notably the alloy beryllium copper), iron, or nickel, beryllium improves many physical properties. For example, tools and components made of beryllium copper alloys are strong and hard and do not create sparks when they strike a steel surface. In air, the surface of beryllium oxidizes readily at room temperature to form a passivation layer 1–10 nm thick that protects it from further oxidation and corrosion. The metal oxidizes in bulk (beyond the passivation layer) when heated above 500 °C (932 °F), and burns brilliantly when heated to about 2,500 °C (4,530 °F).

The commercial use of beryllium requires the use of appropriate dust control equipment and industrial controls at all times because of the toxicity of inhaled beryllium-containing dusts that can cause a chronic life-threatening allergic disease in some people called berylliosis. Berylliosis causes pneumonia and other associated respiratory illness. (Full article...)

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The Dayton Project was a research and development project to produce polonium during World War II, as part of the larger Manhattan Project to build the first atomic bombs. Work took place at several sites in and around Dayton, Ohio. Those working on the project were ultimately responsible for creating the polonium-based modulated neutron initiators which were used to begin the chain reactions in the atomic bombs.

The Dayton Project began in 1943 when Monsanto's Charles Allen Thomas was recruited by the Manhattan Project to coordinate the plutonium purification and production work being carried out at various sites. Scientists at the Los Alamos Laboratory calculated that a plutonium bomb would require a neutron initiator. The best-known neutron sources used radioactive polonium and beryllium, so Thomas undertook to produce polonium at Monsanto's laboratories in Dayton. While most Manhattan Project activity took place at remote locations, the Dayton Project was located in a populated, urban area. It ran from 1943 to 1949, when the Mound Laboratories were completed in nearby Miamisburg, Ohio, and the work moved there.

The Dayton Project developed techniques for extracting polonium from the lead dioxide ore in which it occurs naturally, and from bismuth targets that had been bombarded by neutrons in a nuclear reactor. Ultimately, polonium-based neutron initiators were used in both the gun-type Little Boy and the implosion-type Fat Man used in the atomic bombings of Hiroshima and Nagasaki respectively. The fact that polonium was used as an initiator was classified until the 1960s, but George Koval, a technician with the Manhattan Project's Special Engineer Detachment, penetrated the Dayton Project as a spy for the Soviet Union. (Full article...)

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High-level radioactive waste management concerns how radioactive materials created during production of nuclear power and nuclear weapons are dealt with. Radioactive waste contains a mixture of short-lived and long-lived nuclides, as well as non-radioactive nuclides. There was reportedly some 47,000 tonnes (100 million pounds) of high-level nuclear waste stored in the United States in 2002.

The most troublesome transuranic elements in spent fuel are neptunium-237 (half-life two million years) and plutonium-239 (half-life 24,000 years). Consequently, high-level radioactive waste requires sophisticated treatment and management to successfully isolate it from the biosphere. This usually necessitates treatment, followed by a long-term management strategy involving permanent storage, disposal or transformation of the waste into a non-toxic form. Radioactive decay follows the half-life rule, which means that the rate of decay is inversely proportional to the duration of decay. In other words, the radiation from a long-lived isotope like iodine-129 will be much less intense than that of short-lived isotope like iodine-131.

Governments around the world are considering a range of waste management and disposal options, usually involving deep-geologic placement, although there has been limited progress toward implementing long-term waste management solutions. This is partly because the timeframes in question when dealing with radioactive waste range from 10,000 to millions of years, according to studies based on the effect of estimated radiation doses.

Thus, engineer and physicist Hannes Alfvén identified two fundamental prerequisites for effective management of high-level radioactive waste: (1) stable geological formations, and (2) stable human institutions over hundreds of thousands of years. As Alfvén suggests, no known human civilization has ever endured for so long, and no geologic formation of adequate size for a permanent radioactive waste repository has yet been discovered that has been stable for so long a period. Nevertheless, avoiding confronting the risks associated with managing radioactive wastes may create countervailing risks of greater magnitude. Radioactive waste management is an example of policy analysis that requires special attention to ethical concerns, examined in the light of uncertainty and futurity: consideration of 'the impacts of practices and technologies on future generations'.

There is a debate over what should constitute an acceptable scientific and engineering foundation for proceeding with radioactive waste disposal strategies. There are those who have argued, on the basis of complex geochemical simulation models, that relinquishing control over radioactive materials to geohydrologic processes at repository closure is an acceptable risk. They maintain that so-called "natural analogues" inhibit subterranean movement of radionuclides, making disposal of radioactive wastes in stable geologic formations unnecessary. However, existing models of these processes are empirically underdetermined: due to the subterranean nature of such processes in solid geologic formations, the accuracy of computer simulation models has not been verified by empirical observation, certainly not over periods of time equivalent to the lethal half-lives of high-level radioactive waste. On the other hand, some insist deep geologic repositories in stable geologic formations are necessary. National management plans of various countries display a variety of approaches to resolving this debate.

Researchers suggest that forecasts of health detriment for such long periods should be examined critically. Practical studies only consider up to 100 years as far as effective planning and cost evaluations are concerned. Long term behaviour of radioactive wastes remains a subject for ongoing research. Management strategies and implementation plans of several representative national governments are described below. (Full article...)

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Operation Mosaic was a series of two British nuclear tests conducted in the Montebello Islands in Western Australia on 16 May and 19 June 1956. These tests followed the Operation Totem series and preceded the Operation Buffalo series. The second test in the series was the largest ever conducted in Australia.

The purpose of the tests was to explore increasing the yield of British nuclear weapons through boosting with lithium-6 and deuterium, and the use of a natural uranium tamper. Although a boosted fission weapon is not a hydrogen bomb, which the British Government had agreed would not be tested in Australia, the tests were connected with the British hydrogen bomb programme.

The Operation Totem tests of 1953 had been carried out at Emu Field in South Australia, but Emu Field was considered unsuitable for Operation Mosaic. A new, permanent test site was being prepared at Maralinga in South Australia, but would not be ready until September 1956. It was decided that the best option was to return to the Montebello Islands, where Operation Hurricane had been conducted in 1952. To allow the task force flagship, the tank landing ship HMS Narvik, to return to the UK and refit in time for Operation Grapple, the planned first test of a British hydrogen bomb, 15 July was set as the terminal date for Operation Mosaic. The British Government was anxious that Grapple should take place before a proposed moratorium on nuclear testing came into effect. The second test was therefore conducted under time pressure.

At the time of the Royal Commission into British nuclear tests in Australia it was claimed that the second test was of a significantly higher yield than suggested by the official figures: 98 kilotonnes of TNT (410 TJ) as compared to 60 kilotonnes of TNT (250 TJ), but this remains unsubstantiated. (Full article...)

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Operation Totem was a pair of British atmospheric nuclear tests which took place at Emu Field in South Australia in October 1953. They followed the Operation Hurricane test of the first British atomic bomb, which had taken place at the Montebello Islands a year previously. The main purpose of the trial was to determine the acceptable limit on the amount of plutonium-240 which could be present in a bomb.

In addition to the two main tests, there was a series of five subcritical tests called "Kittens". These did not produce nuclear explosions, but used conventional explosives, polonium-210, beryllium and natural uranium to investigate the performance of neutron initiators. (Full article...)

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The RaLa Experiment, or RaLa, was a series of tests during and after the Manhattan Project designed to study the behavior of converging shock waves to achieve the spherical implosion necessary for compression of the plutonium pit of the nuclear weapon. The experiment used significant amounts of a short-lived radioisotope lanthanum-140, a potent source of gamma radiation; the RaLa is a contraction of Radioactive Lanthanum. The method was proposed by Robert Serber and developed by a team led by the Italian experimental physicist Bruno Rossi.

The tests were performed with 1⁄8 inch (3.2 mm) spheres of radioactive lanthanum, equal to about 100 curies (3.7 TBq) and later 1,000 Ci (37 TBq), located in the center of a simulated nuclear device. The explosive lenses were designed primarily using this series of tests. Some 254 tests were conducted between September 1944 and March 1962. In his history of the Los Alamos project, David Hawkins wrote: “RaLa became the most important single experiment affecting the final bomb design”. (Full article...)

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The Rocky Flats Plant, a former U.S. nuclear weapons production facility located about 15 miles (24 km) northwest of Denver, caused radioactive (primarily plutonium, americium, and uranium) contamination within and outside its boundaries. The contamination primarily resulted from two major plutonium fires in 1957 and 1969 (plutonium is pyrophoric, and shavings can spontaneously combust) and from wind-blown plutonium that leaked from barrels of radioactive waste. Much lower concentrations of radioactive isotopes were released throughout the operational life of the plant from 1952 to 1992, from smaller accidents and from normal operational releases of plutonium particles too small to be filtered. Prevailing winds from the plant carried airborne contamination south and east, into populated areas northwest of Denver.

The contamination of the Denver area by plutonium from the fires and other sources was not publicly reported until the 1970s. According to a 1972 study coauthored by Edward Martell, "In the more densely populated areas of Denver, the Pu contamination level in surface soils is several times fallout", and the plutonium contamination "just east of the Rocky Flats plant ranges up to hundreds of times that from nuclear tests." As noted by Carl Johnson in Ambio, "Exposures of a large population in the Denver area to plutonium and other radionuclides in the exhaust plumes from the plant date back to 1953."

Weapons production at the plant was halted after a combined FBI and EPA raid in 1989 and years of protests. The plant has since been shut down, with its buildings demolished and completely removed from the site. The Rocky Flats Plant was declared a Superfund site in 1989 and began its transformation to a cleanup site in February 1992. Removal of the plant and surface contamination was largely completed in the late 1990s and early 2000s. Nearly all underground contamination was left in place, and measurable radioactive environmental contamination in and around Rocky Flats will probably persist for thousands of years. The land formerly occupied by the plant is now the Rocky Flats National Wildlife Refuge. Plans to make this refuge accessible for recreation have been repeatedly delayed due to lack of funding and protested by citizen organizations.

The Department of Energy continues to fund monitoring of the site, but private groups and researchers remain concerned about the extent and long-term public health consequences of the contamination. Estimates of the public health risk caused by the contamination vary significantly, with accusations that the United States government is being too secretive and that citizen activists are being alarmist. (Full article...)

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The P-9 Project was the codename given during World War II to the Manhattan Project's heavy water production program. The Cominco operation at Trail, British Columbia, was upgraded to produce heavy water. DuPont built three plants in the United States: at the Morgantown Ordnance Works, near Morgantown, West Virginia; at the Wabash River Ordnance Works, near Dana and Newport, Indiana; and at the Alabama Ordnance Works, near Childersburg and Sylacauga, Alabama. The American plants operated from 1943 until 1945. The Canadian plant at Trail continued in operation until 1956. Three nuclear reactors were built using the heavy water produced by the P-9 Project: Chicago Pile 3 at Argonne, and ZEEP and NRX at the Chalk River Laboratories in Canada. (Full article...)

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Operation Peppermint was the codename given during World War II to preparations by the Manhattan Project and the European Theater of Operations United States Army (ETOUSA) to counter the danger that the Germans might disrupt the June 1944 Normandy landings with radioactive poisons.

In response, the Metallurgical Laboratory in Chicago and the Victoreen Instrument Company in Cleveland developed portable radiation detection devices suitable for use in the field. In 1944, Major General Leslie R. Groves, Jr., director of the Manhattan Project, sent Major Arthur V. Peterson to brief General Dwight D. Eisenhower and his senior staff officers at the Supreme Headquarters Allied Expeditionary Force (SHAEF).

In response, ETOUSA initiated Operation Peppermint. Special equipment was prepared. Eleven survey meters and a Geiger counter were shipped to England in early 1944, along with 1,500 film packets, which were used to measure radiation exposure. Another 25 survey meters, 5 Geiger counters and 1,500 film packets were held in storage in the United States, but in readiness to be shipped by air with the highest priority. Chemical Warfare Service teams were trained in its use, and Signal Corps personnel in its maintenance. The equipment was held in readiness, but the preparations were not needed, because the Germans had not developed such weapons. (Full article...)

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Project Alberta, also known as Project A, was a section of the Manhattan Project which assisted in delivering the first nuclear weapons in the atomic bombing of Hiroshima and Nagasaki during World War II.

Project Alberta was formed in March 1945, and consisted of 51 United States Army, Navy, and civilian personnel, including one British scientist. Its mission was three-fold. It first had to design a bomb shape for delivery by air, then procure and assemble it. It supported the ballistic testing work at Wendover Army Air Field, Utah, conducted by the 216th Army Air Forces Base Unit (Project W-47), and the modification of B-29s to carry the bombs (Project Silverplate). After completion of its development and training missions, Project Alberta was attached to the 509th Composite Group at North Field, Tinian, where it prepared facilities, assembled and loaded the weapons, and participated in their use. (Full article...)

Portal:Nuclear technology/Articles/41 The US–UK Mutual Defense Agreement, or 1958 UK–US Mutual Defence Agreement, is a bilateral treaty between the United States and the United Kingdom on nuclear weapons co-operation. The treaty's full name is Agreement between the Government of the United States of America and the Government of the United Kingdom of Great Britain and Northern Ireland for Cooperation on the uses of Atomic Energy for Mutual Defense Purposes. It allows the US and the UK to exchange nuclear materials, technology and information. The US has nuclear co-operation agreements with other countries, including France and other NATO countries, but this agreement is by far the most comprehensive. Because of the agreement's strategic value to Britain, Harold Macmillan (the Prime Minister who presided over the United Kingdom's entry into the agreement) called it "the Great Prize".

The treaty was signed on 3 July 1958 after the Soviet Union had shocked the American public with the launch of Sputnik on 4 October 1957, and the British hydrogen bomb programme had successfully tested a thermonuclear device in the Operation Grapple test on 8 November. The special relationship proved mutually beneficial, both militarily and economically. Britain soon became dependent on the United States for its nuclear weapons since it agreed to limit their nuclear program with the agreement of shared technology. The treaty allowed American nuclear weapons to be supplied to Britain through Project E for use by the Royal Air Force and British Army of the Rhine until the early 1990s when the UK became fully independent in designing and manufacturing its own warheads.

The treaty provided for the sale to the UK of one complete nuclear submarine propulsion plant, as well as ten years' supply of enriched uranium to fuel it. Other nuclear material was also acquired from the US under the treaty. Some 5.4 tonnes of UK-produced plutonium was sent to the US in return for 6.7 kilograms (15 lb) of tritium and 7.5 tonnes of highly enriched uranium (HEU) between 1960 and 1979, but much of the HEU was used not for weapons but as fuel for the growing fleet of British nuclear submarines. The treaty paved the way for the Polaris Sales Agreement, and the Royal Navy ultimately acquired entire weapons systems, with the UK Polaris programme and Trident nuclear programme using American missiles with British nuclear warheads.

The treaty has been amended and renewed nine times. The most recent renewal extended it to 31 December 2024. (Full article...)

Portal:Nuclear technology/Articles/42 The Frisch–Peierls memorandum was the first technical exposition of a practical nuclear weapon. It was written by expatriate German-Jewish physicists Otto Frisch and Rudolf Peierls in March 1940 while they were both working for Mark Oliphant at the University of Birmingham in Britain during World War II.

The memorandum contained the first calculations about the size of the critical mass of fissile material needed for an atomic bomb. It revealed that the amount required might be small enough to incorporate into a bomb that could be delivered by air. It also anticipated the strategic and moral implications of nuclear weapons.

It helped send both Britain and America down a path which led to the MAUD Committee, the Tube Alloys project, the Manhattan Project, and ultimately the atomic bombings of Hiroshima and Nagasaki. (Full article...)

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K-25 was the codename given by the Manhattan Project to the program to produce enriched uranium for atomic bombs using the gaseous diffusion method. Originally the codename for the product, over time it came to refer to the project, the production facility located at the Clinton Engineer Works in Oak Ridge, Tennessee, the main gaseous diffusion building, and ultimately the site. When it was built in 1944, the four-story K-25 gaseous diffusion plant was the world's largest building, comprising over 5,264,000 square feet (489,000 m²) of floor space and a volume of 97,500,000 cubic feet (2,760,000 m³).

Construction of the K-25 facility was undertaken by J. A. Jones Construction. At the height of construction, over 25,000 workers were employed on the site. Gaseous diffusion was but one of three enrichment technologies used by the Manhattan Project. Slightly enriched product from the S-50 thermal diffusion plant was fed into the K-25 gaseous diffusion plant. Its product in turn was fed into the Y-12 electromagnetic plant. The enriched uranium was used in the Little Boy atomic bomb used in the atomic bombing of Hiroshima. In 1946, the K-25 gaseous diffusion plant became capable of producing highly enriched product.

After the war, four more gaseous diffusion plants named K-27, K-29, K-31 and K-33 were added to the site. The K-25 site was renamed the Oak Ridge Gaseous Diffusion Plant in 1955. Production of enriched uranium ended in 1964, and gaseous diffusion finally ceased on the site on 27 August 1985. The Oak Ridge Gaseous Diffusion Plant was renamed the Oak Ridge K-25 Site in 1989, and the East Tennessee Technology Park in 1996. Demolition of all five gaseous diffusion plants was completed in February 2017. (Full article...)

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High Explosive Research (HER) was the British project to develop atomic bombs independently after the Second World War. This decision was taken by a cabinet sub-committee on 8 January 1947, in response to apprehension of an American return to isolationism, fears that Britain might lose its great power status, and the actions by the United States to withdraw unilaterally from sharing of nuclear technology under the 1943 Quebec Agreement. The decision was publicly announced in the House of Commons on 12 May 1948.

HER was a civil project, not a military one. Staff were drawn from and recruited into the Civil Service, and were paid Civil Service salaries. It was headed by Lord Portal, as Controller of Production, Atomic Energy, in the Ministry of Supply. An Atomic Energy Research Establishment was located at a former airfield, Harwell, in Berkshire, under the direction of John Cockcroft. The first nuclear reactor in the UK, a small research reactor known as GLEEP, went critical at Harwell on 15 August 1947. British staff at the Montreal Laboratory designed a larger reactor, known as BEPO, which went critical on 5 July 1948. They provided experience and expertise that would later be employed on the larger, production reactors.

Production facilities were constructed under the direction of Christopher Hinton, who established his headquarters in a former Royal Ordnance Factory at Risley in Lancashire. These included a uranium metal plant at Springfields, nuclear reactors and a plutonium processing plant at Windscale, and a gaseous diffusion uranium enrichment facility at Capenhurst, near Chester. The two Windscale reactors became operational in October 1950 and June 1951. The gaseous diffusion plant at Capenhurst began producing highly enriched uranium in 1954.

William Penney directed bomb design from Fort Halstead. In 1951 his design group moved to a new site at Aldermaston in Berkshire. The first British atomic bomb was successfully tested in Operation Hurricane, during which it was detonated on board the frigate HMS Plym anchored off the Monte Bello Islands in Australia on 3 October 1952. Britain thereby became the third country to test nuclear weapons, after the United States and the Soviet Union. The project concluded with the delivery of the first of its Blue Danube atomic bombs to Bomber Command in November 1953, but British hopes of a renewed nuclear Special Relationship with the United States were frustrated. The technology had been superseded by the American development of the hydrogen bomb, which was first tested in November 1952, only one month after Operation Hurricane. Britain went on to develop its own hydrogen bombs, which it first tested in 1957. A year later, the United States and Britain resumed nuclear weapons cooperation. (Full article...)

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The MAUD Committee was a British scientific working group formed during the Second World War. It was established to perform the research required to determine if an atomic bomb was feasible. The name MAUD came from a strange line in a telegram from Danish physicist Niels Bohr referring to his housekeeper, Maud Ray.

The MAUD Committee was founded in response to the Frisch–Peierls memorandum, which was written in March 1940 by Rudolf Peierls and Otto Frisch, two physicists who were refugees from Nazi Germany working at the University of Birmingham under the direction of Mark Oliphant. The memorandum argued that a small sphere of pure uranium-235 could have the explosive power of thousands of tons of TNT.

The chairman of the MAUD Committee was George Thomson. Research was split among four different universities: the University of Birmingham, University of Liverpool, University of Cambridge and the University of Oxford, each having a separate programme director. Various means of uranium enrichment were examined, as was nuclear reactor design, the properties of uranium-235, the use of the then-hypothetical element plutonium, and theoretical aspects of nuclear weapon design.

After fifteen months of work, the research culminated in two reports, "Use of Uranium for a Bomb" and "Use of Uranium as a Source of Power", known collectively as the MAUD Report. The report discussed the feasibility and necessity of an atomic bomb for the war effort. In response, the British created a nuclear weapons project, code named Tube Alloys. The MAUD Report was made available to the United States, where it energised the American effort, which eventually became the Manhattan Project. The report was also revealed to the Soviet Union by its atomic spies, and helped start the Soviet atomic bomb project. (Full article...)

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The Nassau Agreement, concluded on 21 December 1962, was an agreement negotiated between President of the United States, John F. Kennedy, and Harold Macmillan, the Prime Minister of the United Kingdom, to end the Skybolt Crisis. A series of meetings between the two leaders over three days in the Bahamas followed Kennedy's announcement of his intention to cancel the Skybolt air-launched ballistic missile project. The US agreed to supply the UK with Polaris submarine-launched ballistic missiles for the UK Polaris programme.

Under an earlier agreement, the US had agreed to supply Skybolt missiles in return for allowing the establishment of a ballistic missile submarine base in the Holy Loch near Glasgow. The British Government had then cancelled the development of its medium-range ballistic missile, known as Blue Streak, leaving Skybolt as the basis of the UK's independent nuclear deterrent in the 1960s. Without Skybolt, the V-bombers of the Royal Air Force (RAF) were likely to have become obsolete through being unable to penetrate the improved air defences that the Soviet Union was expected to deploy by the 1970s.

At Nassau, Macmillan rejected Kennedy's other offers, and pressed him to supply the UK with Polaris missiles. These represented more advanced technology than Skybolt, and the US was not inclined to provide them except as part of a Multilateral Force within the North Atlantic Treaty Organization (NATO). Under the Nassau Agreement the US agreed to provide the UK with Polaris. The agreement stipulated that the UK's Polaris missiles would be assigned to NATO as part of a Multilateral Force, and could be used independently only when "supreme national interests" intervened.

The Nassau Agreement became the basis of the Polaris Sales Agreement, a treaty which was signed on 6 April 1963. Under this agreement, British nuclear warheads were fitted to Polaris missiles. As a result, responsibility for Britain's nuclear deterrent passed from the RAF to the Royal Navy. The President of France, Charles de Gaulle, cited Britain's dependence on the United States under the Nassau Agreement as one of the main reasons for his veto of Britain's application for admission to the European Economic Community (EEC) on 14 January 1963. (Full article...)

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The United Kingdom's Polaris programme, officially named the British Naval Ballistic Missile System, provided its first submarine-based nuclear weapons system. Polaris was in service from 1968 to 1996.

Polaris itself was an operational system of four Resolution-class ballistic missile submarines, each armed with 16 Polaris A-3 ballistic missiles. Each missile was able to deliver three ET.317 thermonuclear warheads. This configuration was later upgraded to carry two warheads hardened against the effects of radiation and nuclear electromagnetic pulse, along with a range of decoys.

The British Polaris programme was announced in December 1962 following the Nassau Agreement between the US and the UK. The Polaris Sales Agreement provided the formal framework for cooperation. Construction of the submarines began in 1964, and the first patrol took place in June 1968. All four boats were operational in December 1969. They were operated by the Royal Navy, and based at Clyde Naval Base on Scotland's west coast, a few miles from Glasgow. At least one submarine was always on patrol to provide a continuous at-sea deterrent.

In the 1970s it was considered that the re-entry vehicles were vulnerable to the Soviet anti-ballistic missile screen concentrated around Moscow. To ensure that a credible and independent nuclear deterrent was maintained, the UK developed an improved front end named Chevaline. There was controversy when this project became public knowledge in 1980, as it had been kept secret by four successive governments while incurring huge expenditure. Polaris patrols continued until May 1996, by which time the phased handover to the replacement Trident system had been completed. (Full article...)

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The Polaris Sales Agreement was a treaty between the United States and the United Kingdom which began the UK Polaris programme. The agreement was signed on 6 April 1963. It formally arranged the terms and conditions under which the Polaris missile system was provided to the United Kingdom.

The United Kingdom had been planning to buy the air-launched Skybolt missile to extend the operational life of the British V bombers, but the United States decided to cancel the Skybolt program in 1962 as it no longer needed the missile. The crisis created by the cancellation prompted an emergency meeting between the President of the United States, John F. Kennedy, and the Prime Minister of the United Kingdom, Harold Macmillan, which resulted in the Nassau Agreement, under which the United States agreed to provide Polaris missiles to the United Kingdom instead.

The Polaris Sales Agreement provided for the implementation of the Nassau Agreement. The United States would supply the United Kingdom with Polaris missiles, launch tubes, and the fire control system. The United Kingdom would manufacture the warheads and submarines. In return, the US was given certain assurances by the United Kingdom regarding the use of the missile, but not a veto on the use of British nuclear weapons. The British Resolution-class Polaris ballistic missile submarines were built on time and under budget, and came to be seen as a credible deterrent.

Along with the 1958 US–UK Mutual Defence Agreement, the Polaris Sales Agreement became a pillar of the nuclear Special Relationship between Britain and the United States. The agreement was amended in 1982 to provide for the sale of the Trident missile system. (Full article...)

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Project Emily was the deployment of American-built Thor intermediate-range ballistic missiles (IRBMs) in the United Kingdom between 1959 and 1963. Royal Air Force (RAF) Bomber Command operated 60 Thor missiles, dispersed to 20 RAF air stations, as part of the British nuclear deterrent.

Due to concerns over the buildup of Soviet missiles, US President Dwight D. Eisenhower met Prime Minister Harold Macmillan in Bermuda in March 1957 to explore the possibility of short-term deployment of IRBMs in the United Kingdom until the long-range intercontinental ballistic missiles (ICBMs) were deployed. The October 1957 Sputnik crisis caused this plan to be expedited. The first Thor missile arrived in the UK on a Douglas C-124 Globemaster II transport aircraft in August 1958, and was delivered to the RAF in September.

RAF crews periodically visited the United States for training, culminating in 21 operational training launches from Vandenberg Air Force Base. During the Cuban Missile Crisis in October 1962, 59 of the missiles, with their W49 1.44-megaton-of-TNT (6.0 PJ) thermonuclear warheads, were brought to operational readiness. The Thor missile force was disbanded in 1963, and the missiles were returned to the United States, where most were expended in military space shots.

In October 2012 the former launch sites at RAF Harrington and RAF North Luffenham were granted listed status. (Full article...)

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The Quebec Agreement was a secret agreement between the United Kingdom and the United States outlining the terms for the coordinated development of the science and engineering related to nuclear energy and specifically nuclear weapons. It was signed by Winston Churchill and Franklin D. Roosevelt on 19 August 1943, during World War II, at the First Quebec Conference in Quebec City, Quebec, Canada.

The Quebec Agreement stipulated that the US and UK would pool their resources to develop nuclear weapons, and that neither country would use them against the other, or against other countries without mutual consent, or pass information about them to other countries. It also gave the United States a veto over post-war British commercial or industrial uses of nuclear energy. The agreement merged the British Tube Alloys project with the American Manhattan Project, and created the Combined Policy Committee to control the joint project. Although Canada was not a signatory, the Agreement provided for a Canadian representative on the Combined Policy Committee in view of Canada's contribution to the effort.

British scientists performed important work as part of the British contribution to the Manhattan Project, and in July 1945 British permission required by the agreement was given for the use of nuclear weapons against Japan. The September 1944 Hyde Park Aide-Mémoire extended Anglo-American co-operation into the post-war period, but after the war ended, American enthusiasm for the alliance with Britain waned. The McMahon Act (1946) ended technical co-operation through its control of "restricted data". On 7 January 1948, the Quebec Agreement was superseded by a modus vivendi, an agreement which allowed for limited sharing of technical information between the United States, Britain and Canada. (Full article...)

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Tube Alloys was the research and development programme authorised by the United Kingdom, with participation from Canada, to develop nuclear weapons during the Second World War. Starting before the Manhattan Project in the United States, the British efforts were kept classified, and as such had to be referred to by code even within the highest circles of government.

The possibility of nuclear weapons was acknowledged early in the war. At the University of Birmingham, Rudolf Peierls and Otto Robert Frisch co-wrote a memorandum explaining that a small mass of pure uranium-235 could be used to produce a chain reaction in a bomb with the power of thousands of tons of TNT. This led to the formation of the MAUD Committee, which called for an all-out effort to develop nuclear weapons. Wallace Akers, who oversaw the project, chose the deliberately misleading code name "Tube Alloys". His Tube Alloys Directorate was part of the Department of Scientific and Industrial Research.

The Tube Alloys programme in Britain and Canada was the first nuclear weapons project. Due to the high costs and the fact that Britain was fighting a war within bombing range of its enemies, Tube Alloys was ultimately subsumed into the Manhattan Project by the Quebec Agreement with the United States, under which the two nations agreed to share nuclear weapons technology, and to refrain from using it against each other, or against other countries without mutual consent. However, the United States did not provide complete details of the results of the Manhattan Project to the United Kingdom. The Soviet Union gained valuable information through its atomic spies, who had infiltrated both the British and American projects.

The United States terminated co-operation after the war ended, under the Atomic Energy Act of 1946. That prompted the United Kingdom to relaunch its own project, High Explosive Research. Production facilities were established and British scientists continued their work under the auspices of an independent British programme. In 1952, Britain performed a nuclear test under the codename "Operation Hurricane" and became the third nuclear-weapon state. In 1958, in the wake of the Sputnik crisis, and the British demonstration of a two-stage thermonuclear bomb, the United Kingdom and the United States signed the US–UK Mutual Defence Agreement, which resulted in a resumption of Britain's nuclear Special Relationship with the United States. (Full article...)

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Trident, also known as the Trident nuclear programme or Trident nuclear deterrent, covers the development, procurement and operation of nuclear weapons in the United Kingdom and their means of delivery. Its purpose as stated by the Ministry of Defence is to "deter the most extreme threats to our national security and way of life, which cannot be done by other means". Trident is an operational system of four Vanguard-class submarines armed with Trident II D-5 ballistic missiles, able to deliver thermonuclear warheads from multiple independently targetable re-entry vehicles (MIRVs). It is operated by the Royal Navy and based at Clyde Naval Base on the west coast of Scotland. At least one submarine is always on patrol to provide a continuous at-sea capability. The missiles are manufactured in the United States, while the warheads are British.

The British government initially negotiated with the Carter administration for the purchase of the Trident I C-4 missile. In 1981, the Reagan administration announced its decision to upgrade its Trident to the new Trident II D-5 missile. This necessitated another round of negotiations and concessions. The UK Trident programme was announced in July 1980 and patrols began in December 1994. Trident replaced the submarine-based Polaris system, in operation from 1968 until 1996. Trident is the only nuclear weapon system operated by the UK since the decommissioning of tactical WE.177 free-fall bombs in 1998.

NATO's military posture was relaxed after the collapse of the Soviet Union in 1991. Trident warheads have never been aimed at specific targets on an operational patrol, but await co-ordinates that can be programmed into their computers and fired with several days' notice. Although Trident was designed as a strategic deterrent, the end of the Cold War led the British government to conclude that a sub-strategic—but not tactical—role was required.

A programme for the replacement of the Vanguard class is under way. On 18 July 2016 the House of Commons voted by a large majority to proceed with building a fleet of Dreadnought-class submarines, to be operational by 2028, with the current fleet completely phased out by 2032. (Full article...)

Portal:Nuclear technology/Articles/53 In 1952, the United Kingdom became the third country (after the United States and the Soviet Union) to develop and test nuclear weapons, and is one of the five nuclear-weapon states under the Treaty on the Non-Proliferation of Nuclear Weapons.

The UK initiated a nuclear weapons programme, codenamed Tube Alloys, during the Second World War. At the Quebec Conference in August 1943, it was merged with the American Manhattan Project. The British government considered nuclear weapons to be a joint discovery, but the American Atomic Energy Act of 1946 (McMahon Act) restricted other countries, including the UK, from access to information about nuclear weapons. Fearing the loss of Britain's great power status, the UK resumed its own project, now codenamed High Explosive Research. On 3 October 1952, it detonated an atomic bomb in the Monte Bello Islands in Australia in Operation Hurricane. Eleven more British nuclear weapons tests in Australia were carried out over the following decade, including seven British nuclear tests at Maralinga in 1956 and 1957.

The British hydrogen bomb programme demonstrated Britain's ability to produce thermonuclear weapons in the Operation Grapple nuclear tests in the Pacific, and led to the amendment of the McMahon Act. Since the 1958 US–UK Mutual Defence Agreement, the US and the UK have cooperated extensively on nuclear security matters. The nuclear Special Relationship between the two countries has involved the exchange of classified scientific data and fissile materials such as uranium-235 and plutonium. The UK has not had a programme to develop an independent delivery system since the cancellation of the Blue Streak in 1960. Instead, it purchased US delivery systems for UK use, fitting them with warheads designed and manufactured by the UK's Atomic Weapons Establishment (AWE) and its predecessor. Under the 1963 Polaris Sales Agreement, the US supplied the UK with Polaris missiles and nuclear submarine technology. The US also supplied the Royal Air Force and British Army of the Rhine with nuclear weapons under Project E in the form of aerial bombs, missiles, depth charges and artillery shells until 1992. Nuclear-capable American aircraft had been based in the UK since 1949, but the last US nuclear weapons were withdrawn in 2008.

In 1982, the Polaris Sales Agreement was amended to allow the UK to purchase Trident II missiles. Since 1998, when the UK decommissioned its tactical WE.177 bombs, the Trident has been the only operational nuclear weapons system in British service. The delivery system consists of four Vanguard-class submarines based at HMNB Clyde in Scotland. Each submarine is armed with up to sixteen Trident II missiles, each carrying warheads in up to eight multiple independently targetable re-entry vehicles (MIRVs). With at least one submarine always on patrol, the Vanguards perform a strategic deterrence role and also have a sub-strategic capability. (Full article...)

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