220-614: 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
440-696: A Cockcroft–Walton generator . Cockcroft and Walton used this to perform the first artificial disintegration of an atomic nucleus , a feat popularly known as splitting the atom . During the Second World War Cockcroft became Assistant Director of Scientific Research in the Ministry of Supply , working on radar . He was also a member of the committee formed to handle issues arising from the Frisch–Peierls memorandum , which calculated that an atomic bomb could be technically feasible, and of
660-513: A misnomer , as their energy comes from the nucleus of the atom, just as it does with fusion weapons. In fission weapons, a mass of fissile material ( enriched uranium or plutonium ) is forced into supercriticality —allowing an exponential growth of nuclear chain reactions —either by shooting one piece of sub-critical material into another (the "gun" method) or by compression of a sub-critical sphere or cylinder of fissile material using chemically fueled explosive lenses . The latter approach,
880-665: A policy of deliberate ambiguity , it does not acknowledge having them. Germany , Italy , Turkey , Belgium , the Netherlands , and Belarus are nuclear weapons sharing states. South Africa is the only country to have independently developed and then renounced and dismantled its nuclear weapons. The Treaty on the Non-Proliferation of Nuclear Weapons aims to reduce the spread of nuclear weapons, but there are different views of its effectiveness. There are two basic types of nuclear weapons: those that derive
1100-437: A proton source for them. A crucial moment came when Cockcroft read a paper by George Gamow on quantum tunnelling . Cockcroft realised that as a result of this phenomenon, the desired effect could be achieved with much lower voltages than first thought. In fact, he calculated that protons with energy of just 300,000 electronvolts would be able to penetrate a boron nucleus. Cockcroft and Walton worked on their accelerator for
1320-545: A "hot" radioactive laboratory was not built until 1949, although a small hot laboratory was pressed into service in 1948. A pilot plant was established at the Chalk River Laboratories , which ran until 1950. Despite concerns over whether the process would work, numerous minor changes, and construction problems related to the steel used, the plant was completed on schedule in April 1951. The first active material
1540-535: A British atom bomb was therefore at that stage essential to our defence. You must remember this was all prior to NATO . NATO has altered things. But at that time although we were doing our best to make the Americans understand the realities of the European situation—the world situation—we couldn't be sure we'd succeed. In the end we did. But we couldn't take risks with British security in the meantime. The decision
1760-696: A conference—called for in the manifesto—in Pugwash, Nova Scotia , Eaton's birthplace. This conference was to be the first of the Pugwash Conferences on Science and World Affairs , held in July 1957. By the 1960s, steps were taken to limit both the proliferation of nuclear weapons to other countries and the environmental effects of nuclear testing . The Partial Nuclear Test Ban Treaty (1963) restricted all nuclear testing to underground nuclear testing , to prevent contamination from nuclear fallout, whereas
1980-439: A cost of £250,000. The gaseous diffusion plant at Capenhurst, which cost £14 million, started production in 1953, but only produced low-enriched uranium, and did not produce highly enriched uranium until 1954. By 1957 it was capable of producing 125 kg of highly enriched uranium per annum. British designs at this time used large amounts of enriched uranium; 87 kg for Green Bamboo , 117 kg for Orange Herald . At
2200-483: A division of uranium ore production, with everything up to March 1946 going to the United States, and supplies being shared equally thereafter. At the Combined Policy Committee meeting on 31 July 1946, the financial arrangements were adjusted. Previously, the two countries had split the costs equally; henceforth each would pay for only what they actually received. Britain was therefore able to secure
2420-458: A faster and less vulnerable attack, the development of long-range intercontinental ballistic missiles (ICBMs) and submarine-launched ballistic missiles (SLBMs) has given some nations the ability to plausibly deliver missiles anywhere on the globe with a high likelihood of success. More advanced systems, such as multiple independently targetable reentry vehicles (MIRVs), can launch multiple warheads at different targets from one missile, reducing
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#17327801790652640-614: A few nations possess such weapons or are suspected of seeking them. The only countries known to have detonated nuclear weapons—and acknowledge possessing them—are (chronologically by date of first test) the United States , the Soviet Union (succeeded as a nuclear power by Russia ), the United Kingdom , France , China , India , Pakistan , and North Korea . Israel is believed to possess nuclear weapons, though, in
2860-492: A fission bomb to initiate them. Such a device might provide a simpler path to thermonuclear weapons than one that required the development of fission weapons first, and pure fusion weapons would create significantly less nuclear fallout than other thermonuclear weapons because they would not disperse fission products. In 1998, the United States Department of Energy divulged that the United States had, "...made
3080-536: A former Royal Ordnance Factory at Risley in Lancashire on 4 February 1946. Portal also created a position of Deputy Controller (Technical Policy), to which he appointed Michael Perrin . This created ill-feeling, as Perrin had been junior to Hinton at ICI. Portal also created a Technical Committee to replace the old Tube Alloys Technical Committee. To give the Ministry of Supply's control over atomic energy
3300-638: A full exchange of atomic information, and in return for ending the production of atomic bombs in Britain, American bombs would be stored in Britain under British control. This would have given Britain nuclear weapons much sooner than its own target date of late 1952. The opposition of several key officials, including the United States Atomic Energy Commission 's Lewis Strauss , and Senators Bourke B. Hickenlooper and Arthur Vandenberg , coupled with security concerns aroused by
3520-421: A fusion weapon as of January 2016 , though this claim is disputed. Thermonuclear weapons are considered much more difficult to successfully design and execute than primitive fission weapons. Almost all of the nuclear weapons deployed today use the thermonuclear design because it results in an explosion hundreds of times stronger than that of a fission bomb of similar weight. Thermonuclear bombs work by using
3740-495: A higher neutron flux . British staff at the Montreal Laboratory had designed BEPO in 1945 and 1946; Risley handled the engineering and construction. The key choices in reactor design are the selection of the fuel, the neutron moderator, and the coolant. Since enriched uranium was unavailable, the only available fuel was natural uranium. Similarly, while the Montreal Laboratory had experience with designing and building
3960-706: A joint discovery. On 8 August 1945 the Prime Minister, Clement Attlee , sent a message to President Harry Truman in which he referred to themselves as "heads of the Governments which have control of this great force". Roosevelt had died on 12 April 1945, and the Hyde Park Aide-Mémoire was not binding on subsequent administrations. In fact, the American copy was temporarily physically lost. When Field Marshal Henry Maitland Wilson raised
4180-778: A legal form, a bill was introduced into the House of Commons on 1 May 1946 that became law as the Atomic Energy Act 1946 on 6 November 1946. During the war, Chadwick, Cockcroft, Oliphant, Peierls, Harrie Massey and Herbert Skinner had met in Washington, D.C., in November 1944, and drawn up a proposal for a British atomic energy research establishment, which they had calculated would cost around £1.5 million. The Tube Alloys Committee endorsed their recommendation in April 1945, and Attlee announced its creation in
4400-431: A lithium target and noticed what he thought might be alpha particles. Cockcroft and then Rutherford were summoned, and confirmed that this was indeed the case. That evening, Cockcroft and Walton met at Rutherford's home and produced a letter for Nature in which they announced their results, the first artificial disintegration of an atomic nucleus, which can be described thus: This feat was popularly known as splitting
4620-472: A nation's economic electronics-based infrastructure. Because the effect is most effectively produced by high altitude nuclear detonations (by military weapons delivered by air, though ground bursts also produce EMP effects over a localized area), it can produce damage to electronics over a wide, even continental, geographical area. Research has been done into the possibility of pure fusion bombs : nuclear weapons that consist of fusion reactions without requiring
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#17327801790654840-537: A new nuclear strategy, one that is distinct from that which gave relative stability during the Cold War. Since 1996, the United States has had a policy of allowing the targeting of its nuclear weapons at terrorists armed with weapons of mass destruction . Robert Gallucci argues that although traditional deterrence is not an effective approach toward terrorist groups bent on causing a nuclear catastrophe, Gallucci believes that "the United States should instead consider
5060-663: 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
5280-596: A new wing to house it. Cockcroft supervised the work. The cyclotron was in operation by October 1938, and the new wing was completed in 1940. Oliphant felt that the cyclotron was not big enough, and commenced construction of a larger 60-inch cyclotron at the University of Birmingham . Its construction was delayed by the outbreak of the Second World War in Europe in 1939, and it too would be obsolescent when it
5500-425: A nuclear war between two nations would result in mutual annihilation. From this point of view, the significance of nuclear weapons is to deter war because any nuclear war would escalate out of mutual distrust and fear, resulting in mutually assured destruction . This threat of national, if not global, destruction has been a strong motivation for anti-nuclear weapons activism. Critics from the peace movement and within
5720-411: A nuclear weapon from another country by threatening nuclear retaliation is known as the strategy of nuclear deterrence . The goal in deterrence is to always maintain a second strike capability (the ability of a country to respond to a nuclear attack with one of its own) and potentially to strive for first strike status (the ability to destroy an enemy's nuclear forces before they could retaliate). During
5940-465: A nuclear weapon is a gravity bomb dropped from aircraft ; this was the method used by the United States against Japan in 1945. This method places few restrictions on the size of the weapon. It does, however, limit attack range, response time to an impending attack, and the number of weapons that a country can field at the same time. With miniaturization, nuclear bombs can be delivered by both strategic bombers and tactical fighter-bombers . This method
6160-409: A nuclear weapon to its target is an important factor affecting both nuclear weapon design and nuclear strategy . The design, development, and maintenance of delivery systems are among the most expensive parts of a nuclear weapons program; they account, for example, for 57% of the financial resources spent by the United States on nuclear weapons projects since 1940. The simplest method for delivering
6380-433: A nuclear weapon with suitable materials (such as cobalt or gold ) creates a weapon known as a salted bomb . This device can produce exceptionally large quantities of long-lived radioactive contamination . It has been conjectured that such a device could serve as a "doomsday weapon" because such a large quantity of radioactivities with half-lives of decades, lifted into the stratosphere where winds would distribute it around
6600-476: A painful bureaucratic battle over personnel like Challens, whose expertise was wanted for research on both nuclear weapons and guided missiles . In the end, HER kept 25 of the 30 key personnel that ARE wanted, including Challens. The site was taken over on 1 April 1950. Penney became Chief Superintendent High Explosive Research (CSHER). The first stage of work at Aldermaston was completed in December 1951, but
6820-421: A policy of expanded deterrence, which focuses not solely on the would-be nuclear terrorists but on those states that may deliberately transfer or inadvertently leak nuclear weapons and materials to them. By threatening retaliation against those states, the United States may be able to deter that which it cannot physically prevent.". Graham Allison makes a similar case, arguing that the key to expanded deterrence
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7040-537: A price, warrants our retaining that position; and indeed it places a duty upon us to continue to retain it. I am not aware of any suggestion, seriously advanced, that by a sudden stroke of fate, as it were, we have overnight ceased to be a great power. In his 1961 memoirs, Attlee explained his decision: At that time we had to bear in mind that there was always the possibility of [the United States] withdrawing and becoming isolationist again. The manufacture of
7260-631: A proposed organisation chart, detailed his staffing requirements, and listed his accommodation requirements, which he felt could be met at Fort Halstead, the Royal Arsenal at Woolwich , and Shoeburyness . In July 1946, the Chiefs of Staff Committee considered the issue of nuclear weapons, and recommended that Britain acquire them. This recommendation was accepted by the Cabinet Defence Committee on 22 July 1946. The Chief of
7480-640: A reactor. By this time, there was interest from the scientists in making better use of uranium fuel by re-enrichment of spent fuel rods. A gaseous diffusion plant was costed at somewhere between £30 and £40 million. The Gen 75 Committee considered the proposal in October 1946. Perrin, who was present, later recalled that: The meeting was about to decide against it on grounds of cost, when [Ernest] Bevin arrived late and said "We've got to have this thing. I don't mind it for myself, but I don't want any other Foreign Secretary of this country to be talked at or to by
7700-654: A request for developing a new, separate site for HER on grounds of safety, security and economy. This was approved, but it took another six months to locate a suitable site. An airbase, RAF South Cerney in Gloucestershire was chosen, but the RAF refused to relinquish the site. A former airbase, RAF Aldermaston , was then selected. At the same time, it was decided to separate HER from the Armaments Research Establishment (ARE). This resulted in
7920-484: A research student at the Cavendish Laboratory on the recommendation of Miles Walker and the director of research at Metropolitan Vickers. Cockcroft enrolled as a PhD student in 1924, with a Foundation Scholarship of St John's College, and a State Scholarship. Under Rutherford's supervision, he wrote his doctoral thesis "On phenomena occurring in the condensation of molecular streams on surfaces", which
8140-669: A response to an immediate military threat but rather something fundamental and almost instinctive—a feeling that Britain must possess so climactic a weapon in order to deter an atomically armed enemy, a feeling that Britain as a great power must acquire all major new weapons, a feeling that atomic weapons were a manifestation of the scientific and technological superiority on which Britain's strength, so deficient if measured in sheer numbers of men, must depend. This represented deep-rooted British political and strategic ideas. The war had left Britain impoverished. Its gold and dollar reserves had been depleted. A third of its merchant ships now lay on
8360-518: A result, extraordinary measures had to be taken to provide Penney with a first shipment of plutonium in June 1952, and sufficient quantity for a core by the 1 August 1952 deadline. Improvements in the bomb design ultimately meant that he could get by with 15 per cent less plutonium. Starting in 1953, the Windscale reactors were able to use slightly enriched uranium as a fuel. They were shut down after
8580-419: A resumption of cooperation on nuclear energy were disappointed. The Americans soon made it clear that cooperation was restricted to basic scientific research. The next meeting of the Combined Policy Committee on 15 April 1946 produced no accord on collaboration, and resulted in an exchange of cables between Truman and Attlee. Truman cabled on 20 April that he did not see the communiqué he had signed as obligating
8800-406: A scholarship to St. John's College, Cambridge , Walker's alma mater. Cockcroft was successful, winning a £30 scholarship and a £20 bursary awarded to undergraduates of limited means. Metropolitan Vickers gave him £50 subject to his returning after completing his degree. Walker and an aunt made up the balance of the £316 fee. As a graduate of another university, he was allowed to skip the first year of
9020-447: A significant portion of their energy from fission reactions used to "trigger" fusion reactions, and fusion reactions can themselves trigger additional fission reactions. Only six countries—the United States , Russia , the United Kingdom , China , France , and India —have conducted thermonuclear weapon tests. Whether India has detonated a "true" multi-staged thermonuclear weapon is controversial. North Korea claims to have tested
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9240-502: A site at Chalk River , Ontario, on the south bank of the Ottawa River some 110 miles (180 km) north west of Ottawa. The Chalk River Laboratories opened in 1944, and the Montreal Laboratory was closed in July 1946. ZEEP went critical on 5 September 1945, becoming the first operating nuclear reactor outside the United States. The larger NRX followed on 21 July 1947. With five times the neutron flux of any other reactor, it
9460-550: A substantial investment" in the past to develop pure fusion weapons, but that, "The U.S. does not have and is not developing a pure fusion weapon", and that, "No credible design for a pure fusion weapon resulted from the DOE investment". Nuclear isomers provide a possible pathway to fissionless fusion bombs. These are naturally occurring isotopes ( Hf being a prominent example) which exist in an elevated energy state. Mechanisms to release this energy as bursts of gamma radiation (as in
9680-404: Is a dwindling asset and that, unless we capitalise it quickly, we shall be outstripped. We now have a real contribution to make to a 'merger.' Soon we shall have little or none." The British considered producing an atomic bomb without American help, but the project would have needed overwhelming priority, the projected cost was staggering, disruption to other wartime projects was inevitable, and it
9900-420: Is a thermonuclear weapon that yields a relatively small explosion but a relatively large amount of neutron radiation . Such a weapon could, according to tacticians, be used to cause massive biological casualties while leaving inanimate infrastructure mostly intact and creating minimal fallout. Because high energy neutrons are capable of penetrating dense matter, such as tank armor, neutron warheads were procured in
10120-721: Is an explosive device that derives its destructive force from nuclear reactions , either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb ), producing a nuclear explosion . Both bomb types release large quantities of energy from relatively small amounts of matter . The first test of a fission ("atomic") bomb released an amount of energy approximately equal to 20,000 tons of TNT (84 TJ ). The first thermonuclear ("hydrogen") bomb test released energy approximately equal to 10 million tons of TNT (42 PJ). Nuclear bombs have had yields between 10 tons TNT (the W54 ) and 50 megatons for
10340-456: Is analogous to identifying a criminal by fingerprints. "The goal would be twofold: first, to deter leaders of nuclear states from selling weapons to terrorists by holding them accountable for any use of their weapons; second, to give leaders every incentive to tightly secure their nuclear weapons and materials." According to the Pentagon's June 2019 " Doctrine for Joint Nuclear Operations " of
10560-403: Is coming up with ways of tracing nuclear material to the country that forged the fissile material. "After a nuclear bomb detonates, nuclear forensics cops would collect debris samples and send them to a laboratory for radiological analysis. By identifying unique attributes of the fissile material, including its impurities and contaminants, one could trace the path back to its origin." The process
10780-481: Is for the purpose of achieving different yields for different situations , and in manipulating design elements to attempt to minimize weapon size, radiation hardness or requirements for special materials, especially fissile fuel or tritium. Some nuclear weapons are designed for special purposes; most of these are for non-strategic (decisively war-winning) purposes and are referred to as tactical nuclear weapons . The neutron bomb purportedly conceived by Sam Cohen
11000-503: Is no evidence that it is feasible beyond the military domain. However, the U.S. Air Force funded studies of the physics of antimatter in the Cold War , and began considering its possible use in weapons, not just as a trigger, but as the explosive itself. A fourth generation nuclear weapon design is related to, and relies upon, the same principle as antimatter-catalyzed nuclear pulse propulsion . Most variation in nuclear weapon design
11220-409: Is not a fusion bomb. In the boosted bomb, the neutrons produced by the fusion reactions serve primarily to increase the efficiency of the fission bomb. There are two types of boosted fission bomb: internally boosted, in which a deuterium-tritium mixture is injected into the bomb core, and externally boosted, in which concentric shells of lithium-deuteride and depleted uranium are layered on the outside of
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#173278017906511440-490: Is not clear that this has ever been implemented, and their plausible use in nuclear weapons is a matter of dispute. The other basic type of nuclear weapon produces a large proportion of its energy in nuclear fusion reactions. Such fusion weapons are generally referred to as thermonuclear weapons or more colloquially as hydrogen bombs (abbreviated as H-bombs ), as they rely on fusion reactions between isotopes of hydrogen ( deuterium and tritium ). All such weapons derive
11660-454: Is the primary means of nuclear weapons delivery; the majority of U.S. nuclear warheads, for example, are free-fall gravity bombs, namely the B61 , which is being improved upon to this day. Preferable from a strategic point of view is a nuclear weapon mounted on a missile , which can use a ballistic trajectory to deliver the warhead over the horizon. Although even short-range missiles allow for
11880-672: The Atomic Energy Act of 1946 (McMahon Act) in August 1946, made it clear that the UK would no longer be allowed access to the United States' atomic research. This partly resulted from the arrest for espionage of Alan Nunn May in February 1946. Cockcroft helped negotiate a new, more informal and unsigned agreement with the Americans that was announced on 7 January 1948, known as the Modus Vivendi . The renewed cooperation that he hoped for under
12100-665: The Berkeley Radiation Laboratory , assisted with the electromagnetic separation process. Cockcroft became the director of the Anglo-Canadian Montreal Laboratory . The British mission to the Los Alamos Laboratory led by James Chadwick , and later Peierls, included distinguished scientists such as Geoffrey Taylor , James Tuck , Niels Bohr , William Penney , Frisch, Ernest Titterton and Klaus Fuchs , who
12320-689: The Combined Policy Committee and the Combined Development Trust to coordinate their efforts. The 19 September 1944 Hyde Park Aide-Mémoire extended both commercial and military cooperation into the post-war period. A British mission led by Akers assisted in the development of gaseous diffusion technology at the SAM Laboratories in New York. Another, led by Oliphant, who acted as deputy director at
12540-578: The Isle of Sheppey in October 1943 conclusively demonstrated that SCR-584 was superior. This made Cockcroft very unpopular at the Ministry of Supply, but he had intelligence that the Germans were planning to deploy the V-1 flying bomb . On 1 January 1944, Lieutenant-General Sir Ronald Weeks sent Washington an urgent request for 134 SCR-584 sets. The proximity fuze had been pioneered by Alan Butement . The idea
12760-734: The MAUD Committee which succeeded it. In 1940, as part of the Tizard Mission , he shared British technology with his counterparts in the United States. Later in the war, the fruits of the Tizard Mission came back to Britain in the form of the SCR-584 radar set and the proximity fuze , which were used to help defeat the V-1 flying bomb . In May 1944, he became director of the Montreal Laboratory , and oversaw
12980-421: The MAUD Committee , of which Cockcroft was also a member, in June 1940. This committee directed the ground-breaking early research in Britain. In August 1940, Cockcroft travelled to the United States as part of the Tizard Mission . Because Britain had developed many new technologies but lacked the industrial capacity to fully exploit them, it was decided to share them with the United States, although that nation
13200-570: The Officers' Training Corps there, but did not wish to become an officer . During the summer break he worked at a YMCA canteen at Kinmel Camp in Wales. He enlisted in the British Army on 24 November 1915. On 29 March 1916, he joined the 59th Training Brigade, Royal Field Artillery , where he was trained as a signaller . He was then posted to B Battery, 92nd Field Artillery Brigade, one of
13420-688: The Prime Minister of Canada , Mackenzie King , went to Washington, D.C., to confer with Truman about future cooperation in nuclear weapons and nuclear power. A Memorandum of Intention they signed replaced the Quebec Agreement. It made Canada a full partner; continued the Combined Policy Committee and Combined Development Trust; and reduced the obligation to obtain consent for the use of nuclear weapons to merely requiring consultation. The three leaders agreed that there would be full and effective cooperation on atomic energy, but British hopes for
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#173278017906513640-620: The Secretary of State of the United States as I have just been in my discussion with Mr Byrnes . We've got to have this thing over here, whatever it costs ... We've got to have the bloody Union Jack flying on top of it." Penney had joined the Los Alamos Laboratory in 1944, and had served on the Target Committee that had selected cities to be attacked. He had been in the observation plane Big Stink during
13860-695: The Starfish Prime high-altitude nuclear test in 1962, an unexpected effect was produced which is called a nuclear electromagnetic pulse . This is an intense flash of electromagnetic energy produced by a rain of high-energy electrons which in turn are produced by a nuclear bomb's gamma rays. This flash of energy can permanently destroy or disrupt electronic equipment if insufficiently shielded. It has been proposed to use this effect to disable an enemy's military and civilian infrastructure as an adjunct to other nuclear or conventional military operations. By itself it could as well be useful to terrorists for crippling
14080-472: The Treaty on the Non-Proliferation of Nuclear Weapons (1968) attempted to place restrictions on the types of activities signatories could participate in, with the goal of allowing the transference of non-military nuclear technology to member countries without fear of proliferation. John Cockcroft Sir John Douglas Cockcroft (27 May 1897 – 18 September 1967) was an English physicist who shared
14300-554: The Tsar Bomba (see TNT equivalent ). A thermonuclear weapon weighing as little as 600 pounds (270 kg) can release energy equal to more than 1.2 megatonnes of TNT (5.0 PJ). A nuclear device no larger than a conventional bomb can devastate an entire city by blast, fire, and radiation . Since they are weapons of mass destruction , the proliferation of nuclear weapons is a focus of international relations policy. Nuclear weapons have been deployed twice in war , both by
14520-676: The Tsar Bomba of the USSR, which released an energy equivalent of over 50 megatons of TNT (210 PJ), was a three-stage weapon. Most thermonuclear weapons are considerably smaller than this, due to practical constraints from missile warhead space and weight requirements. In the early 1950s the Livermore Laboratory in the United States had plans for the testing of two massive bombs, Gnomon and Sundial , 1 gigaton of TNT and 10 gigatons of TNT respectively. Fusion reactions do not create fission products, and thus contribute far less to
14740-699: The University of Brighton ; and the Cockcroft building of the University of Salford . The oldest building at the Research School of Physical Sciences and Engineering , Australian National University, the Cockcroft building, is named after him. Cockcroft's papers are held at the Churchill Archives Centre in Cambridge, and are accessible to the public. They include his lab books, correspondence, photographs (with dozens depicting
14960-492: The Windscale fire in October 1957. Cartridges of uranium were irradiated in the Windscale reactors to produce plutonium. The cartridges were pushed through the reactor, and exited on the other side, where they fell into submerged steel skips which were pulled into a deep cooling pond. After being irradiated, each cartridge contained as many as 180 isotopes of 35 different chemical elements . Less than half of one per cent of
15180-746: The ZEEP heavy-water reactor in Canada, no heavy water was available in the UK, so graphite was the only choice for a neutron moderator. That left cooling, and for an experimental reactor, air cooling was the obvious choice. The resulting reactor was thus quite similar to the American X-10 Graphite Reactor . BEPO, which went critical on 5 July 1948, used 40 long tons (41 t) of metallic uranium and 850 long tons (860 t) of graphite, encased in 600 long tons (610 t) of steel and 3,000 long tons (3,000 t) of concrete. For
15400-608: The bombing of Nagasaki , and had done damage assessment on the ground following Japan's surrender. He had returned to England in November 1945 intending to resume his academic career, but was approached by C. P. Snow , one of the Civil Service Commissioners , and asked to become Chief Superintendent Armament Research (CSAR, pronounced "Caesar"), in charge of the Ministry of Supply's Armaments Research Department (ARD) at Fort Halstead in Kent. His appointment as CSAR
15620-443: The chivalric orders , but he was created a Knight Commander of the Order of the Bath in May 1953. Perhaps because this was rare, scientists normally regarded becoming a member of the Order of Merit as a greater honour; Cockcroft became an Order of Merit member in December 1956. He also received the Royal Medal in 1954, the Faraday Medal in 1955, the American Medal of Freedom in 1947 and Atoms for Peace Award in 1961, He
15840-424: The hafnium controversy ) have been proposed as possible triggers for conventional thermonuclear reactions. Antimatter , which consists of particles resembling ordinary matter particles in most of their properties but having opposite electric charge , has been considered as a trigger mechanism for nuclear weapons. A major obstacle is the difficulty of producing antimatter in large enough quantities, and there
16060-614: The head of government or head of state . Despite controls and regulations governing nuclear weapons, there is an inherent danger of "accidents, mistakes, false alarms, blackmail, theft, and sabotage". In the late 1940s, lack of mutual trust prevented the United States and the Soviet Union from making progress on arms control agreements. The Russell–Einstein Manifesto was issued in London on July 9, 1955, by Bertrand Russell in
16280-450: The tamper . Test firings of explosive lenses were conducted at Foulness by a team under the direction of Roy Pilgrim. To achieve near-simultaneous detonations of the lenses, the Americans had developed the exploding-bridgewire detonator ; this had to be duplicated. Ernest Mott and Cecil Bean developed them, while Challens devised the firing circuits. Work on the plutonium core had to wait until Windscale delivered sufficient product, which
16500-670: The tripos . He sat the tripos exam in June 1924, achieved a B* as a wrangler , and was awarded his BA degree. Cockcroft married Elizabeth Crabtree on 26 August 1925, in a ceremony at the Bridge Street United Methodist Church in Todmorden. They had six children. The first, a boy known as Timothy, died in infancy. They subsequently had four daughters, Joan Dorothea (Thea), Jocelyn, Elisabeth Fielden and Catherine Helena; and another son, Christopher Hugh John. Ernest Rutherford accepted Cockcroft as
16720-436: The tropopause into the stratosphere , where the calm non-turbulent winds permit the debris to travel great distances from the burst, eventually settling and unpredictably contaminating areas far removed from the target of the explosion. There are other types of nuclear weapons as well. For example, a boosted fission weapon is a fission bomb that increases its explosive yield through a small number of fusion reactions, but it
16940-537: The "implosion" method, is more sophisticated and more efficient (smaller, less massive, and requiring less of the expensive fissile fuel) than the former. A major challenge in all nuclear weapon designs is to ensure that a significant fraction of the fuel is consumed before the weapon destroys itself. The amount of energy released by fission bombs can range from the equivalent of just under a ton to upwards of 500,000 tons (500 kilotons ) of TNT (4.2 to 2.1 × 10 GJ). All fission reactions generate fission products ,
17160-461: 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
17380-654: The 1951 Nobel Prize in Physics with Ernest Walton for splitting the atomic nucleus , which was instrumental in the development of nuclear power . After service on the Western Front with the Royal Field Artillery during the Great War , Cockcroft studied electrical engineering at Manchester Municipal College of Technology whilst he was an apprentice at Metropolitan Vickers Trafford Park and
17600-533: The 1980s (though not deployed in Europe) for use as tactical payloads for US Army artillery shells (200 mm W79 and 155 mm W82 ) and short range missile forces. Soviet authorities announced similar intentions for neutron warhead deployment in Europe; indeed, they claimed to have originally invented the neutron bomb, but their deployment on USSR tactical nuclear forces is unverifiable. A type of nuclear explosive most suitable for use by ground special forces
17820-528: The 2 February 1950 arrest of Fuchs, who was working at Harwell, as a Soviet spy, caused the proposal to be rejected. By this time, most of the original 1,350 long tons (1,370 t) allocated to Britain had been used up, and the Americans agreed to allocate 505 long tons (513 t) from the Springfields stockpile. Britain was allocated a further 561 long tons (570 t) in 1951, and 500 long tons (510 t) in 1952. Due to increased production, and
18040-462: The Air Staff, Lord Tedder , officially requested an atomic bomb on 9 August 1946. The Chiefs of Staff estimated that 200 bombs would be required by 1957. Despite this, and the research and construction of facilities that had already been approved, there was still no official decision to proceed with making atomic bombs. Portal submitted his proposal to do so at the 8 January 1947 meeting of
18260-414: The Americans would assist with the construction of a heavy water - moderated nuclear reactor in Canada, and would provide technical assistance with matters such as corrosion and the effects of radiation on materials. They would not provide details about plutonium chemistry or metallurgy, although irradiated uranium slugs were made available for the British to work it out for themselves. A sticking point
18480-534: The Atomic Energy (Defence Research) Committee AE(DR), which came under the DRPC, and was chaired by Tizard; and the Atomic Energy (Review of Production) Committee, which was answerable to Portal. But Tizard failed to gain control of atomic energy policy. An early debate among the scientists was whether the fissile material for an atomic bomb should be uranium-235 or plutonium . Tube Alloys had performed much of
18700-676: The British, and not as far advanced. The British and American projects exchanged information, but did not initially combine their efforts. British officials did not reply to an August 1941 American offer to create a combined project. In November 1941, Frederick L. Hovde , the head of the London liaison office of the American Office of Scientific Research and Development (OSRD), raised the issue of cooperation and exchange of information with Anderson and Lord Cherwell , who demurred, ostensibly over concerns about American security. Ironically, it
18920-650: The Chalk River Laboratories, was a Soviet spy. In August 1947, Cockcroft was one of the scientists who signed a petition urging that Nunn May's ten-year prison sentence be reduced, an act he later regretted. In April 1945, Cockcroft and Oliphant scouted a site for a similar establishment in Britain, settling on RAF Harwell . Cockcroft was offered the directorship of the Atomic Energy Research Establishment (AERE) at Harwell on 9 November 1945. The official announcement
19140-425: The Cold War, policy and military theorists considered the sorts of policies that might prevent a nuclear attack, and they developed game theory models that could lead to stable deterrence conditions. Different forms of nuclear weapons delivery (see above) allow for different types of nuclear strategies. The goals of any strategy are generally to make it difficult for an enemy to launch a pre-emptive strike against
19360-461: The Council , became the minister responsible, and Wallace Akers from Imperial Chemical Industries (ICI) was appointed the director of Tube Alloys. In July 1940, Britain had offered to give the United States access to its scientific research, and Cockcroft, as part of the Tizard Mission , briefed American scientists on British developments. He discovered that the American project was smaller than
19580-658: The Council of CERN as well as Chairman of the Nuclear Physics Sub-Committee of the Department of Scientific and Industrial Research . In addition to winning, along with Walton, the Hughes Medal and 1951 Nobel Prize in Physics, Cockcroft received numerous awards and accolades over the years. He became a knight bachelor in January 1948. This was normal: scientists were seldom inducted into
19800-471: The Gen 163 Committee, another ad hoc committee, which agreed to proceed with the development of atomic bombs. It also endorsed Portal's proposal to place Penney in charge of the bomb development effort, although Penney was not informed of this decision until May. Of the decision, Margaret Gowing wrote: The British decision to make an atomic bomb had "emerged" from a body of general assumptions. It had not been
20020-585: The House of Commons on 29 October 1945, informing the House that it would cost about £1 million to build and £500,000 per annum to run. The obvious choices for a director of the new establishment were Chadwick and Cockcroft, and the former urged that the latter be appointed. Cockcroft agreed, subject to stipulation in writing that he would be answerable only to the Minister and his Permanent Secretary , and, except where subject to requirements for military secrecy,
20240-494: The Joint Chiefs of Staffs website Publication, "Integration of nuclear weapons employment with conventional and special operations forces is essential to the success of any mission or operation." Because they are weapons of mass destruction, the proliferation and possible use of nuclear weapons are important issues in international relations and diplomacy. In most countries, the use of nuclear force can only be authorized by
20460-580: The Ministry of Defence in November 1946, and in January 1947 he also became the chairman of the Defence Research Policy Committee (DRPC), which was established to advise the Minister of Defence and the Chiefs of Staff on matters of scientific policy. Tizard attempted to gain some control over nuclear weapons policy. Anderson's advisory committee was abolished at the end of 1947, and two new committees were established in its place,
20680-568: The Ministry of Defence in the 1960s, noted that "the word folly did not seem appropriate after the accident". On 24 January 1959, Churchill College, Cambridge , was formally recognised by the University. Two days later, the Trustees announced that Cockcroft would be its first Master. Although it would also teach the humanities and social sciences, 70 per cent of the student body would study science and technology related subjects. He nominated
20900-652: The Mond Laboratory after Kapitza, who had returned to the Soviet Union . He supervised the installation of new cryogenic equipment, and supervised low temperature research. He was elected a Fellow of the Royal Society in 1936, and in 1939 was elected the Jacksonian Professor of Natural Philosophy , effective 1 October 1939. Cockcroft and Walton were well aware of the limits of their accelerator. A much better design had been developed in
21120-503: The Nuclear Age (1961) that mere possession of a nuclear arsenal was enough to ensure deterrence, and thus concluded that the spread of nuclear weapons could increase international stability . Some prominent neo-realist scholars, such as Kenneth Waltz and John Mearsheimer , have argued, along the lines of Gallois, that some forms of nuclear proliferation would decrease the likelihood of total war , especially in troubled regions of
21340-504: The Theoretical Physics; Robert Spence, Cockcroft's deputy at Montreal Laboratory, became head of Chemistry; H.W.B. Skinner, of General Physics; Otto Frisch, of Nuclear Physics; and John Dunworth, of Reactor Physics. Fuchs was later arrested as a Soviet spy on 3 February 1950. The low-powered, graphite-moderated GLEEP , which stood for Graphite Low Energy Experimental Pile, was designed by the Montreal Laboratory, and became
21560-483: The Tizard Mission, but work continued in Britain, where a team was established at Christchurch under Charles Drummond Ellis in February 1942. Work proceeded fitfully, and by 1943, production was still two years away. On a visit to the United States in November 1943, Cockcroft discussed adapting the American proximity fuze for British use with Merle Tuve . As a result, 150,000 fuzes for QF 3.7-inch AA guns were ordered on 16 January 1944. The fuzes arrived in time to engage
21780-440: The UK, a small 100 kW research reactor known as GLEEP , went critical at Harwell on 15 August 1947. It was fuelled by 12 long tons (12 t) of uranium metal and 21 long tons (21 t) of uranium dioxide, and used 505 long tons (513 t) of nuclear graphite as a neutron moderator . This was fine for some experimental work, but the production of radioactive isotopes required a more powerful 6,000 kW reactor with
22000-664: The USAAF detonated a plutonium implosion-type fission bomb nicknamed " Fat Man " over the Japanese city of Nagasaki . These bombings caused injuries that resulted in the deaths of approximately 200,000 civilians and military personnel . The ethics of these bombings and their role in Japan's surrender are to this day, still subjects of debate . Since the atomic bombings of Hiroshima and Nagasaki , nuclear weapons have been detonated over 2,000 times for testing and demonstration. Only
22220-777: The USAF AIR-2 Genie , the AIM-26 Falcon and US Army Nike Hercules . Missile interceptors such as the Sprint and the Spartan also used small nuclear warheads (optimized to produce neutron or X-ray flux) but were for use against enemy strategic warheads. Other small, or tactical, nuclear weapons were deployed by naval forces for use primarily as antisubmarine weapons. These included nuclear depth bombs or nuclear armed torpedoes. Nuclear mines for use on land or at sea are also possibilities. The system used to deliver
22440-527: The United States against the Japanese cities of Hiroshima and Nagasaki in 1945 during World War II . Nuclear weapons have only twice been used in warfare, both times by the United States against Japan at the end of World War II . On August 6, 1945, the United States Army Air Forces (USAAF) detonated a uranium gun-type fission bomb nicknamed " Little Boy " over the Japanese city of Hiroshima ; three days later, on August 9,
22660-812: The United States and Britain resumed nuclear weapons cooperation . The neutron was discovered by James Chadwick at the Cavendish Laboratory at the University of Cambridge in February 1932. In April 1932, his Cavendish colleagues John Cockcroft and Ernest Walton split lithium atoms with accelerated protons . Enrico Fermi and his team in Rome conducted experiments involving the bombardment of elements by slow neutrons, which produced heavier elements and isotopes . Then, in December 1938, Otto Hahn and Fritz Strassmann at Hahn's laboratory in Berlin-Dahlem bombarded uranium with slowed neutrons, and discovered that barium had been produced, and therefore that
22880-510: The United States by Ernest Lawrence , which he called the cyclotron . The Cavendish Laboratory was able to keep ahead of the Americans despite having an inferior accelerator with clever physics, but Cockcroft pressed Rutherford to obtain a cyclotron for the Cavendish laboratory. Rutherford baulked at the price tag, but a £250,000 gift from Lord Austin enabled a 36-inch (910 mm) cyclotron, based on Lawrence's design, to be built, along with
23100-440: The United States to assist Britain in designing, constructing and operating an atomic energy plant. The passing of the Atomic Energy Act of 1946 (McMahon Act) in August 1946, which was signed by Truman on 1 August 1946, and went into effect at midnight on 1 January 1947, ended technical cooperation. Its control of "restricted data" prevented the United States' allies from receiving any information. This partly resulted from
23320-594: The United States, Britain and Canada. Under this agreement, all the Congo ore from 1948 and 1949 was shipped to the United States. The Trust was renamed the Combined Development Agency in January 1948. The first Soviet atomic bomb test in August 1949 was embarrassing to the British (who had not expected a Soviet atomic weapon until 1954) for having been beaten, but it was for the Americans another reason for cooperation. The agreement on raw materials
23540-654: The United States, as had that captured in Europe by the Alsos Mission , even though some of it passed through British hands. The entire output of the Shinkolobwe mine was contracted to the Combined Development Trust until 1956, but in March 1946 there were fears that the mine might be exhausted in 1947, resulting in a severe uranium shortage. After some negotiation, Groves and Chadwick agreed on
23760-526: The United States. Small, two-man portable tactical weapons (somewhat misleadingly referred to as suitcase bombs ), such as the Special Atomic Demolition Munition , have been developed, although the difficulty of combining sufficient yield with portability limits their military utility. Nuclear warfare strategy is a set of policies that deal with preventing or fighting a nuclear war. The policy of trying to prevent an attack by
23980-858: The V-1 flying bombs in August 1944, shooting down 97 per cent of them. For his services, he was made a Commander of the Order of the British Empire in June 1944. In August 1943, the Quebec Agreement subsumed the British Tube Alloys project into the Manhattan Project , and established the Combined Policy Committee to control the Manhattan Project. A final agreement was spelt out on 20 May 1944. Under it,
24200-439: The advantage of being only 25 miles (40 km) from Risley. One decision was that instead of producing uranium hexafluoride using elemental fluorine, which was difficult and hazardous to transport, it was produced at Springfields from chlorine trifluoride . This process was untried and did not work properly, and when production commenced in February 1952, the hexafluoride plant did not perform adequately. It had to be redesigned at
24420-628: The agreement proved illusory. The development of the independent British nuclear deterrent led to the Atomic Energy Act being amended in 1958, and to a resumption of the nuclear Special Relationship between America and Britain under the 1958 US–UK Mutual Defence Agreement . Under Cockcroft's direction, AERE took part in frontier fusion research in the post-war years, including the ZETA program. Sir George Paget Thomson began research in nuclear fusion at Imperial College London in 1946. This
24640-504: The arrest for espionage of British physicist Alan Nunn May , who had worked in the Montreal Laboratory, in February 1946, while the legislation was being debated. The remaining British scientists working in the United States were denied access to papers that they had written just days before. Attlee had created a cabinet sub-committee , the Gen 75 Committee (known informally by Attlee as the "Atomic Bomb Committee"), on 10 August 1945 to examine
24860-649: The atom . For this accomplishment, Cockcroft and Walton were awarded the Hughes Medal in 1938, and the Nobel Prize in Physics in 1951. They went on to disintegrate carbon , nitrogen and oxygen using protons, deuterons and alpha particles. They demonstrated that they had produced radioactive isotopes , including carbon-11 and nitrogen-13 . In 1929, Cockcroft was appointed a Supervisor in Mechanical Sciences at St John's College. He
25080-499: The bottom of the ocean. About 250,000 homes had been destroyed and another 3 million had been damaged while hardly any had been built for years. In early 1947, factories suspended production for want of coal. The United States had abruptly terminated Lend-Lease when the war ended. In its place was a $ 3.75 billion loan from the United States and a $ 1.25 billion loan from Canada, most of which had been spent by August 1947. Nonetheless, there remained an implacable belief that
25300-485: The chance of a successful missile defense . Today, missiles are most common among systems designed for delivery of nuclear weapons. Making a warhead small enough to fit onto a missile, though, can be difficult. Tactical weapons have involved the most variety of delivery types, including not only gravity bombs and missiles but also artillery shells, land mines , and nuclear depth charges and torpedoes for anti-submarine warfare . An atomic mortar has been tested by
25520-415: The chemical separation plant. At Hanford, the Americans had used a bismuth phosphate process to separate the plutonium from the uranium. This was wasteful; the plutonium was retrieved, but the uranium was left in a state from which it could not easily be recovered. A team at the Montreal Laboratory investigated this problem, and had devised a new process similar to that used with uranium. They had tried out
25740-611: The chimney stacks of the Windscale plutonium production reactors be fitted, at great expense, with high-performance filters. That was in response to a report that uranium oxide had been found in the vicinity of the X-10 Graphite Reactor in Oak Ridge , Tennessee. Because it was decided to fit them after the stacks had been designed, the filters became pronounced lumps at the top of the chimneys. The reactors had been designed to remain clean and uncorroded during use, so it
25960-503: The company that owned the mine, was controlled by British interests. In May 1944, Sir John Anderson and US Ambassador John Winant negotiated a deal with the Belgian government in exile and Edgar Sengier , the director of Union Minière, for the mine to be reopened and 1,720 long tons (1,750 t) of ore to be purchased at $ 1.45 a pound. American and British leaders concluded that it was in their best interest to gain control of as much of
26180-435: The creation of nuclear fallout than fission reactions, but because all thermonuclear weapons contain at least one fission stage, and many high-yield thermonuclear devices have a final fission stage, thermonuclear weapons can generate at least as much nuclear fallout as fission-only weapons. Furthermore, high yield thermonuclear explosions (most dangerously ground bursts) have the force to lift radioactive debris upwards past
26400-455: The decision process. The prospect of mutually assured destruction might not deter an enemy who expects to die in the confrontation. Further, if the initial act is from a stateless terrorist instead of a sovereign nation, there might not be a nation or specific target to retaliate against. It has been argued, especially after the September 11, 2001, attacks , that this complication calls for
26620-470: The decision was taken to build a small reactor in order to test the Montreal Laboratory's calculations relating to such matters as lattice dimensions, sheathing materials, and control rods , before proceeding with the full-scale NRX reactor. This was named ZEEP , for Zero Energy Experimental Pile. Building reactors in downtown Montreal was out of the question; the Canadians selected, and Groves approved,
26840-469: 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,
27060-477: The densely-populated British Isles the only such locations were in the north and west of Scotland. By April 1947, Hinton had convinced Portal of the advantages of a gas-cooled system. Helium was at first the preferred choice as a coolant gas, but the main source of it was the United States, and under the McMahon Act, the United States would not supply it for nuclear weapons production, so, in the end, air cooling
27280-474: The design for the proximity fuze , details of Frank Whittle 's jet engine and the Frisch–Peierls memorandum describing the feasibility of an atomic bomb. Though these may be considered the most significant, many other items were also transported, including designs for rockets, superchargers, gunsights and submarine detection devices. He returned to Britain in December 1940. Soon after his return, Cockcroft
27500-521: The development of the ZEEP and NRX reactors, and the creation of the Chalk River Laboratories . After the war Cockcroft became the director of the Atomic Energy Research Establishment (AERE) at Harwell , where the low-powered, graphite-moderated GLEEP became the first nuclear reactor to operate in western Europe when it was started on 15 August 1947. This was followed by the British Experimental Pile 0 (BEPO) in 1948. Harwell
27720-506: The discovery and development of new sources of uranium in Portugal, South Africa and Australia, there was sufficient uranium for the United States, British and Canadian programmes, although Britain had to cancel a reactor in 1949. Between January 1946 and March 1953, £44 million was spent on constructing nuclear weapons facilities. Staff were drawn from and recruited into the Civil Service , and were paid Civil Service salaries. During
27940-549: The end of 1961, having produced between 3.8 and 4.9 tonnes of highly enriched uranium, it was switched over to low-enriched uranium production for civil nuclear power. Key staff recruited to work at Fort Halstead included John Challens , who commenced on 1 January 1948. By mid-1948, it became clear that Penney's initial estimate that he would require 220 staff was wide of the mark, and that he would need nearly 500. This meant not only taking personnel from other projects, but scrapping some entirely. In October 1948, Penney submitted
28160-469: The energy of a fission bomb to compress and heat fusion fuel. In the Teller-Ulam design , which accounts for all multi-megaton yield hydrogen bombs, this is accomplished by placing a fission bomb and fusion fuel ( tritium , deuterium , or lithium deuteride ) in proximity within a special, radiation-reflecting container. When the fission bomb is detonated, gamma rays and X-rays emitted first compress
28380-499: The establishment would be run like a university, with free exchange of views and the publication of papers. His appointment was announced in November 1945, although he did not leave Canada until September 1946. The Atomic Energy Research Establishment (AERE) did not come under Portal's control until January 1950. A committee selected a site for the AERE at RAF Harwell , an airfield about 13 miles (21 km) south of Oxford . The airfield
28600-507: The expertise in the design of nuclear reactors to produce it, nor the requisite knowledge of plutonium chemistry or metallurgy to extract it. However, the Montreal Laboratory had designed and was building pilot reactors, and had carried out some work on separating plutonium from uranium. The Manhattan Project had pursued both avenues, and the scientists who had worked at Los Alamos were aware of work there with composite cores that used both; but there were concerns that Britain might not have
28820-679: The feasibility of a nuclear weapons programme. To provide technical advice, Attlee created an Advisory Committee on Atomic Energy, with Anderson as its chairman. Anderson was an independent Member of Parliament for the Scottish Universities who sat on the Opposition Front Bench . As chairman of the Advisory Committee on Atomic Energy, Anderson had his own office in the Cabinet Office , and
29040-403: The feed would have been converted to plutonium, but about 5 per cent was now radioactive fission products , the remainder being slightly depleted uranium. After being stored underwater for 150 days, the short-lived isotopes had decayed, leaving significant quantities of about 20 radioactive isotopes. Using remote handling , the cartridges were placed in lead-lined "coffins" and transported to
29260-433: The first fellows, and he oversaw the initial construction. Controversy arose over the chapel. A 1961 plan to build it at the entrance to the college, as was traditional at Cambridge, led to the immediate resignation of Francis Crick , a staunch atheist, as a fellow. The first undergraduates arrived in 1961, and the college, still incomplete, was formally opened by Prince Philip, Duke of Edinburgh , on 5 June 1964. Cockcroft
29480-473: The first nuclear reactor to operate in Western Europe when it was started on 15 August 1947. This was followed by BEPO, a 6 MW research reactor designed by AERE, on 3 July 1948. Because heavy water was unavailable in Britain, BEPO was designed and built as a graphite-moderated reactor. Harwell was involved in the design of reactors at Windscale , and the chemical separation plant there. The passage of
29700-563: The first year of the course. He received his BSc in June 1920. Miles Walker, the professor of electrical engineering there, persuaded him to take up an apprenticeship with Metropolitan Vickers . He obtained a 1851 Exhibition Scholarship from the Royal Commission for the Exhibition of 1851 , and submitted his MSc thesis on the "Harmonic Analysis for Alternating Currents" in June 1922. Walker then suggested Cockcroft sit for
29920-455: The fission bomb core. The external method of boosting enabled the USSR to field the first partially thermonuclear weapons, but it is now obsolete because it demands a spherical bomb geometry, which was adequate during the 1950s arms race when bomber aircraft were the only available delivery vehicles. The detonation of any nuclear weapon is accompanied by a blast of neutron radiation . Surrounding
30140-420: The fusion fuel, then heat it to thermonuclear temperatures. The ensuing fusion reaction creates enormous numbers of high-speed neutrons , which can then induce fission in materials not normally prone to it, such as depleted uranium . Each of these components is known as a "stage", with the fission bomb as the "primary" and the fusion capsule as the "secondary". In large, megaton-range hydrogen bombs, about half of
30360-435: The future would be like the past. Bevin told the House of Commons on 16 May 1947 that: His Majesty's Government does not accept the view ... that we have ceased to be a great power, or the contention that we have ceased to play that role. We regard ourselves as one of the powers most vital to the peace of the world, and we still have a historic part to play. The very fact we have fought so hard for liberty, and paid such
30580-535: The globe, would make all life on the planet extinct. In connection with the Strategic Defense Initiative , research into the nuclear pumped laser was conducted under the DOD program Project Excalibur but this did not result in a working weapon. The concept involves the tapping of the energy of an exploding nuclear bomb to power a single-shot laser that is directed at a distant target. During
30800-700: 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
31020-496: The majority of their energy from nuclear fission reactions alone, and those that use fission reactions to begin nuclear fusion reactions that produce a large amount of the total energy output. All existing nuclear weapons derive some of their explosive energy from nuclear fission reactions. Weapons whose explosive output is exclusively from fission reactions are commonly referred to as atomic bombs or atom bombs (abbreviated as A-bombs ). This has long been noted as something of
31240-511: The matter in a Combined Policy Committee meeting in June, the American copy could not be found. The British sent Secretary of War , Henry L. Stimson a photocopy on 18 July 1945. Even then, Groves questioned the document's authenticity until the American copy was located years later in the papers of Vice Admiral Wilson Brown Jr. , Roosevelt's naval aide, apparently misfiled by someone unaware of what Tube Alloys was, and thought it had something to do with naval guns. On 9 November 1945, Attlee and
31460-461: The metal pipes. Moreover, there were concerns about safety. Water absorbs neutrons, so if there is a sudden loss of cooling water this will result in an increase in the neutron flux and the reactor temperature, and possibly a catastrophic nuclear meltdown . Such an event did indeed occur in the Chernobyl disaster in 1986. The American solution was to locate the facility in a remote location, but in
31680-407: The midst of the Cold War. It highlighted the dangers posed by nuclear weapons and called for world leaders to seek peaceful resolutions to international conflict. The signatories included eleven pre-eminent intellectuals and scientists, including Albert Einstein , who signed it just days before his death on April 18, 1955. A few days after the release, philanthropist Cyrus S. Eaton offered to sponsor
31900-545: The military establishment have questioned the usefulness of such weapons in the current military climate. According to an advisory opinion issued by the International Court of Justice in 1996, the use of (or threat of use of) such weapons would generally be contrary to the rules of international law applicable in armed conflict, but the court did not reach an opinion as to whether or not the threat or use would be lawful in specific extreme circumstances such as if
32120-408: The missiles before they land or implementing civil defense measures using early-warning systems to evacuate citizens to safe areas before an attack. Weapons designed to threaten large populations or to deter attacks are known as strategic weapons . Nuclear weapons for use on a battlefield in military situations are called tactical weapons . Critics of nuclear war strategy often suggest that
32340-402: The money, resources or skilled manpower for this. In the end, it came down to economics; a reactor could be built more cheaply than a separation plant that produced an equivalent quantity of enriched uranium, and made more efficient use of uranium fuel. A reactor and separation plant capable of producing enough plutonium for fifteen bombs per year was costed at around £20 million. The facility
32560-664: The next two years. Rutherford obtained a £1,000 grant from the University of Cambridge for them to buy a transformer and other equipment they needed. Cockcroft was elected a Fellow of St. John's College on 5 November 1928. He and Walton began operating their accelerator in March 1932, bombarding lithium and beryllium with high-energy protons. They expected to see gamma rays , which French scientists had reported, but none were found. In February 1932, James Chadwick demonstrated that what had been observed were actually neutrons . Cockcroft and Walton then switched to looking for alpha particles instead. On 14 April 1932, Walton bombarded
32780-579: The offices, giving the area the nickname "the Cage". With Portal's appointment came consideration of splitting Anderson's committee, which functioned as both an advisory and an interdepartmental body. In August 1946, a new standing committee was created, the Atomic Energy Official Committee, which assumed the interdepartmental function. In March 1947, Roger Makins became its chairman. Anderson's committee declined in influence, and
33000-455: The pioneering research on gaseous diffusion for uranium enrichment , and Oliphant's team in Berkeley were well-acquainted with the electromagnetic process. The staff that had remained in Britain strongly favoured uranium-235; but the scientists that had worked in the United States argued for plutonium on the basis of its greater efficiency as an explosive, despite the fact that they had neither
33220-419: The plutonium processing building was only handed over in April 1952, the month that the first plutonium was due to arrive from Windscale. At the peak of construction in 1953, over 4,000 personnel were working on the site. The choice of plutonium for the fissile component of the bomb meant that Penney's HER team at Fort Halstead had to design an implosion-type nuclear weapon . The Los Alamos Laboratory had solved
33440-496: The plutonium-producing production reactors, the same reasons mandated the use of natural uranium fuel and graphite as a moderator; but it was originally assumed that they would be water-cooled like the American reactors at the Hanford Site. A water-cooled reactor of the required size would require about 30,000 imperial gallons (140,000 L; 36,000 US gal) of water per day, preferably very pure so as to avoid corroding
33660-611: The post, as he felt that he lacked administrative experience outside the Royal Air Force , but eventually accepted it for a two-year term, commencing in March 1946. In this role he had direct access to the Prime Minister. Portal ran the project until 1951, when he was succeeded by Sir Frederick Morgan . He established his headquarters at Shell Mex House on the Strand, London , where the wartime Tube Alloys had been. Special security barriers were installed to close off this section of
33880-474: The power of thousands of tons of dynamite. Oliphant took the Frisch–Peierls memorandum to Sir Henry Tizard , the chairman of the Tizard Committee , and the MAUD Committee was established to investigate further. It directed an intensive research effort, and in July 1941, produced two comprehensive reports that concluded an atomic bomb was not only technically feasible, but could be produced before
34100-469: The problem of doing this with explosive lenses . The involvement of several British scientists gave HER a solid base of experience to work from. The British design would hew to that of the American Fat Man as closely as possible. An important change would be the substitution of RDX , an ARD product, for Composition B as the fast explosive component of the lenses; Baratol would still provide
34320-503: The process, which they believed could be employed on an industrial scale, to extract 20 mg of plutonium from a spent Hanford fuel rod. The cartridges were dissolved in nitric acid and dibutyl carbitol was used to remove the plutonium. After 1946, the only source of plutonium was from the NRX reactor in Canada, and irradiated rods from there did not arrive in Britain until mid-1948. Nor would Harwell have been able to handle them if they had;
34540-428: The remains of the split atomic nuclei. Many fission products are either highly radioactive (but short-lived) or moderately radioactive (but long-lived), and as such, they are a serious form of radioactive contamination . Fission products are the principal radioactive component of nuclear fallout . Another source of radioactivity is the burst of free neutrons produced by the weapon. When they collide with other nuclei in
34760-407: The same grave as his son Timothy. A memorial service was held at Westminster Abbey on 17 October 1967. Several buildings in the United Kingdom are named after him: the Cockcroft building at the New Museums Site of the University of Cambridge , comprising a lecture theatre and several hardware laboratories; the Cockcroft Institute at Daresbury Laboratory in Cheshire; the Cockcroft building of
34980-470: The services of its secretariat. He accompanied Attlee on his November 1945 trip to the United States. A 2 September 1945 Admiralty study of "The Influence of the Atomic Bomb on War" forecast that an enemy could build 500 bombs during ten years of peace, and warned that if 10 per cent of the arsenal was used on the United Kingdom, "over night the main base of the British Empire could be rendered ineffective", with enough left for other British forces around
35200-415: The site of a former poison gas plant, at a cost of £5.5 million. The first uranium metal was produced in October 1948. Uranium ore was crushed and dissolved in acids. Impurities were separated and uranium oxide was precipitated. Radium was returned to Union Minière under the contract with the company. The uranium oxide was then purified. It was dissolved in nitric acid to produce uranyl nitrate . This
35420-421: The slow component. This was handled by the explosives experts at Woolwich, who devised the machining processes and produced prototypes of the lenses and moulds. Production was then handled by two Royal Ordnance Factories. The first lenses were delivered in 1952, and there were enough for two sets for the Operation Hurricane assemblies. Woolwich provided the supercharge, the spherical shell of explosive that encases
35640-426: The smaller Sceptre by Allibone's AEI group. James L. Tuck 's group at the Los Alamos Laboratory was also researching fusion, and Cockcroft struck an agreement with the Americans that they would release their results together, which was done in 1958. Despite Cockcroft's perennial optimism that a breakthrough was imminent, fusion power remained an elusive goal. As director of the AERE, Cockcroft famously insisted that
35860-405: The structure of atomic nuclei. To explore it further, he needed an artificial means of creating particles with a velocity high enough to overcome the charge of the nucleus. This opened a new line of research at the Cavendish Laboratory. He assigned Cockcroft, Thomas Allibone and Ernest Walton to the problem. They built what became known as a Cockcroft–Walton accelerator . Mark Oliphant designed
36080-402: The surrounding material, the neutrons transmute those nuclei into other isotopes, altering their stability and making them radioactive. The most commonly used fissile materials for nuclear weapons applications have been uranium-235 and plutonium-239 . Less commonly used has been uranium-233 . Neptunium-237 and some isotopes of americium may be usable for nuclear explosives as well, but it
36300-498: The survival of the state were at stake. Another deterrence position is that nuclear proliferation can be desirable. In this case, it is argued that, unlike conventional weapons, nuclear weapons deter all-out war between states, and they succeeded in doing this during the Cold War between the U.S. and the Soviet Union . In the late 1950s and early 1960s, Gen. Pierre Marie Gallois of France, an adviser to Charles de Gaulle , argued in books like The Balance of Terror: Strategy for
36520-399: The system fully operational. In 1940, he became part of the Advisory Council for Scientific Research and Technical Development. In April 1940, along he became a member of the Committee for the Scientific Study of Air Warfare formed to handle issues arising from the Frisch–Peierls memorandum , which calculated that an atomic bomb could be technically feasible. This committee was succeeded by
36740-425: The units of the 20th (Light) Division , on the Western Front . Cockcroft participated in the Advance to the Hindenburg Line and the Third Battle of Ypres . He applied for a commission, and was accepted. He was sent to Brighton in February 1918 to learn about gunnery, and in April 1918, to the Officer Candidate School in Weedon Bec in Northamptonshire , where he was trained as a field artillery officer. He
36960-422: The uranium nucleus had been split. Hahn wrote to his colleague Lise Meitner , who, with her nephew Otto Frisch , developed a theoretical justification for the process, which they published in Nature in 1939. By analogy with the division of biological cells , they named the process " fission ". The discovery of fission raised the possibility that an extremely powerful atomic bomb could be created. The term
37180-458: The uranium it needed without having to outbid the United States, and paid for it in sterling . Meanwhile, because the adjustment applied retrospectively to VJ Day, it received reimbursement for the supplies allocated to the United States, thus easing Britain's dollar shortage. By the end of 1946, Britain had received 1,350 long tons (1,370 t), and another 500 was stockpiled for the Trust at Springfields , near Preston in Lancashire. Uranium ore
37400-409: The war ended, perhaps in as little as two years. The Committee unanimously recommended pursuing the development of an atomic bomb as a matter of urgency, although it recognised that the resources required might be beyond those available to Britain. A new directorate known by the deliberately misleading name of Tube Alloys was created to coordinate this effort. Sir John Anderson , the Lord President of
37620-435: The war, Chadwick had arranged for ICI to build a small plant to produce uranium. By 1947, it was operational and producing 3,000 pounds (1,400 kg) per week. This would be used in BEPO, the experimental reactor built at Harwell, but the plant required uranium oxide feed, and the export of this from the United States was banned under the McMahon Act. Hinton and his staff at Risley built a new uranium plant at Springfields, on
37840-446: The weapon system and difficult to defend against the delivery of the weapon during a potential conflict. This can mean keeping weapon locations hidden, such as deploying them on submarines or land mobile transporter erector launchers whose locations are difficult to track, or it can mean protecting weapons by burying them in hardened missile silo bunkers. Other components of nuclear strategies included using missile defenses to destroy
38060-631: The world where there exists a single nuclear-weapon state. Aside from the public opinion that opposes proliferation in any form, there are two schools of thought on the matter: those, like Mearsheimer, who favored selective proliferation, and Waltz, who was somewhat more non- interventionist . Interest in proliferation and the stability-instability paradox that it generates continues to this day, with ongoing debate about indigenous Japanese and South Korean nuclear deterrent against North Korea . The threat of potentially suicidal terrorists possessing nuclear weapons (a form of nuclear terrorism ) complicates
38280-412: The world's uranium deposits as possible. The Combined Development Trust was established for this purpose on 14 June 1944. It consisted of three American, two British and one Canadian members, with an American, initially Groves, as chairman. By the end of the war, it had control of 97 per cent of the world's uranium and 65 per cent of the thorium . During the war, all the uranium from the Congo had gone to
38500-440: The world. In October 1945, the Gen 75 Committee considered the issue of ministerial responsibility for atomic energy. The Cabinet Secretary , Sir Edward Bridges , and the Advisory Committee on Atomic Energy both recommended that it be placed within the Ministry of Supply . Developing atomic energy would require an enormous construction effort, which the Ministry of Supply was best equipped to undertake. The Tube Alloys Directorate
38720-624: The yield comes from the final fissioning of depleted uranium. Virtually all thermonuclear weapons deployed today use the "two-stage" design described to the right, but it is possible to add additional fusion stages—each stage igniting a larger amount of fusion fuel in the next stage. This technique can be used to construct thermonuclear weapons of arbitrarily large yield. This is in contrast to fission bombs, which are limited in their explosive power due to criticality danger (premature nuclear chain reaction caused by too-large amounts of pre-assembled fissile fuel). The largest nuclear weapon ever detonated,
38940-400: Was a modern one, with a long runway, and the Air Ministry was reluctant to release it until the Prime Minister intervened. Responsibility for the development of atomic bombs lay outside the realm of the Ministry of Defence . One reason for this was that it was only created in October 1946, by which time Portal had already been appointed as CPAE. Tizard became the Chief Scientific Adviser to
39160-441: Was already familiar to the British public through the writings of H. G. Wells , in his 1913 novel The World Set Free . George Paget Thomson , at Imperial College London , and Mark Oliphant , an Australian physicist at the University of Birmingham , were tasked with carrying out a series of experiments on uranium. By February 1940, Thomson's team had failed to create a chain reaction in natural uranium, and he had decided that it
39380-405: Was also a member of their research staff. He then won a scholarship to St. John's College, Cambridge , where he sat the tripos exam in June 1924, becoming a wrangler . Ernest Rutherford accepted Cockcroft as a research student at the Cavendish Laboratory , and Cockcroft completed his doctorate under Rutherford's supervision in 1928. With Walton and Mark Oliphant , he built what became known as
39600-521: Was announced on 1 January 1946, but Groves asked him to assist in the American Operation Crossroads nuclear tests at Bikini Atoll . Penney left for the United States in March 1946, and did not return to Britain until October 1946. Portal then asked him to draw up a scheme for an Atomic Weapons Section within the Armaments Research Department which would design, develop and construct atomic bombs. In his 1 November 1946 report to Portal, which he had to type himself for security reasons, Penney provided
39820-528: Was appointed Chief Superintendent of the Air Defence Research Development Establishment (ADRDE) at Christchurch , Hampshire. His focus was on the use of radar for shooting down enemy aircraft. The GL Mk. III radar was developed as a target tracking and predicting radar, but by 1942 the SCR-584 radar developed for the same purpose in the United States became available, and Cockcroft recommended that it be acquired under Lend-Lease . On his own initiative, he acquired SCR-584 sets for testing, and trials conducted on
40040-408: Was appointed a Supervisor in Physics in 1931, and in 1933 became the junior bursar , making him responsible for the upkeep of the buildings, many of which were suffering from neglect. The college gatehouse had to be partly taken down in order to repair damage done by deathwatch beetles , and Cockcroft supervised rewiring of the electrics. In 1935, Rutherford appointed him the director of research at
40260-423: Was approved by the Gen 75 committee on 18 December 1945 "with the highest urgency and importance". A few months later, Portal, who had not been appointed when this decision was taken, began to have doubts. Word reached him of problems with the Hanford Site reactors, which had been all but completely shut down due to Wigner's disease . On a visit to the United States in May 1946, Groves advised Portal not to build
40480-563: Was at the Church of England school in Walsden from 1901 to 1908, at Todmorden Elementary School from 1908 to 1909, and at Todmorden Secondary School from 1909 to 1914, where he played football and cricket . Among the girls at the school was his future wife, Eunice Elizabeth Crabtree. In 1914, he won a County Major Scholarship, West Riding of Yorkshire , to the Victoria University of Manchester , where he studied mathematics . The Great War broke out in August 1914. Cockcroft completed his first year at Manchester in June 1915. He joined
40700-414: Was carried out at Harwell, as the hot laboratory at Aldermaston was not completed until May 1952. The first plutonium billet was cast there from plutonium nitrate from the Chalk River Laboratories in 1951. The metallurgists chose to alloy the plutonium with gallium to stabilise it in the malleable δ phase allotrope . Not until the first billet arrived from Harwell in 1951 were they able to confirm that this
40920-404: Was chosen. With the need for a remote site obviated, it was decided to build the facility on the coast of Cumberland at a former Royal Ordnance Factory, ROF Drigg . This was soon switched to a more suitable site at the nearby former ROF Sellafield . To avoid any confusion with Springfields, the name was changed to Windscale. Construction began in September 1947. The danger of the Wigner Effect
41140-408: Was commissioned as a lieutenant in the Royal Field Artillery on 17 October 1918. After the war ended, Cockcroft was released from the Army in January 1919. He elected not to return to the Victoria University of Manchester, but to study electrical engineering at Manchester Municipal College of Technology . Because he had completed a year at Victoria University of Manchester, he was allowed to skip
41360-416: Was completed after the war. At the outbreak of the Second World War, Cockcroft took up the post of Assistant Director of Scientific Research in the Ministry of Supply , working on radar . In 1938, Sir Henry Tizard showed Cockcroft Chain Home , the ring of coastal early warning radar stations built by the Royal Air Force (RAF) to detect and track aircraft. Now, he helped deploy scientists to help get
41580-411: Was disbanded when he departed at the end of 1947. During the war, Christopher Hinton had been seconded from ICI to the Ministry of Supply and had become Deputy Director General of Filling Factories . He was due to return to ICI at the end 1945, but agreed to oversee the design, construction and operation of the new facilities at a salary far below that offered by ICI. He established his headquarters in
41800-403: Was due to expire at the end of the year. The Americans offered to make bombs in the United States available for Britain to use if the British agreed to end their atomic bomb programme. This offer was rejected on the grounds that it was not "compatible with our status as a first class power to depend on others for weapons of this supreme importance." Instead, the British suggested that there would be
42020-405: Was fed into the plant on 25 February 1952. The plant performed well for twelve years, exceeding its designed production targets, and was only decommissioned when a larger facility was required. The first plutonium billet was cast on 31 March 1952, but it was impure, and could not be used in a bomb. Further work at Harwell and Windscale was required to perfect the process. The gaseous diffusion plant
42240-440: Was involved in the design of the reactors and the chemical separation plant at Windscale . Under his direction it took part in frontier fusion research, including the ZETA program. His insistence that the chimney stacks of the Windscale reactors be fitted with filters was mocked as Cockcroft's Folly until the core of one of the reactors ignited and released radionuclides during the Windscale fire of 1957. From 1959 to 1967, he
42460-506: Was later revealed to be a Soviet spy. As overall head of the British Mission, Chadwick forged a close and successful partnership with Brigadier General Leslie R. Groves , the director of the Manhattan Project. He ensured that British participation was complete and wholehearted. With the end of the war the Special Relationship between Britain and the United States "became very much less special". The British government had trusted that America would share nuclear technology, which it considered
42680-426: 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
42900-407: Was made a Chevalier de la Légion d'Honneur by France in 1952, and was awarded the Knight Commander of the Military Order of Christ by Portugal in 1955, and the Grand Cross of the Order of Alfonso X by Spain in 1958. Cockcroft died from a heart attack at his home at Churchill College, Cambridge, on 18 September 1967. He is buried at the Parish of the Ascension Burial Ground in Cambridge, in
43120-452: Was made on 29 January 1946, but the news leaked two months before the announcement, and before the Canadian government was informed, creating a diplomatic incident. It was agreed that Cockcroft would not depart until a successor was found, and he did not depart Chalk River for Harwell until 30 September 1946. In the meantime he recruited staff for the new laboratory. Klaus Fuchs from the Manhattan Project's Los Alamos Laboratory became head of
43340-400: Was not overlooked. Walter Zinn visited Britain in 1948 and provided crucial information. New calculations based on this meant that the layout of the graphite blocks, which were already being machined, had to be changed. The two Windscale reactors became operational in October 1950 and June 1951. Due to faulty calculations at the design stage, the reactors did not produce the expected output. As
43560-534: Was not until late 1951. The uranium tamper proved more of a challenge for the metallurgists than anticipated, due to a shortage of machine tools and moulds, and difficulty with the vacuum furnace . The first spheres were cast in December 1951, and while they were spherical to within 0.75 thou (0.019 mm ), there were some casting defects, and it was feared they would hinder the implosion process. The defects were repaired, and two castings were prepared for Operation Hurricane. Work on plutonium chemistry and metallurgy
43780-586: Was not worth pursuing; but at Birmingham, Oliphant's team had reached a strikingly different conclusion. Oliphant had delegated the task to two German refugee scientists, Rudolf Peierls and Frisch, who could not work on the university's secret projects like radar because they were enemy aliens and therefore lacked the necessary security clearance. They calculated the critical mass of a metallic sphere of pure uranium-235 , and found that instead of tons, as everyone had assumed, as little as 1 to 10 kilograms (2.2 to 22.0 lb) would suffice, which would explode with
44000-412: Was not yet at war. The information provided by the Tizard Mission contained some of the greatest scientific advances made during the war. The shared technology included radar technologies, in particular the greatly improved cavity magnetron designed by Oliphant's group at Birmingham, which the American historian James Phinney Baxter III described as "the most valuable cargo ever brought to our shores",
44220-430: Was practical. The first plutonium at Aldermaston was cast in an argon atmosphere in a cerium sulphide crucible. The other radioactive element in use was polonium , which was used in the initiator . It was one of the parts of the Manhattan Project that the British mission had not been involved in, and little was known about its chemistry and properties, except that it had a half-life of 138 days. A disturbing discovery
44440-405: Was president of the Institute of Physics from 1954 to 1956, and of the British Association for the Advancement of Science . He served as chancellor of the Australian National University in Canberra from 1961 to 1965, a largely symbolic post that involved a visit once a year for degree conferring ceremonies. He delivered the Rutherford Memorial Lecture in 1944. He was the British delegate on
44660-419: Was publicly announced in the House of Commons on 12 May 1948 by the Minister of Defence , Albert Alexander , albeit in an oblique answer to a pre-arranged question from George Jeger , a Labour Party backbencher . D notice No. 25 prohibited the publication of details on the design, construction or location of atomic weapons. The project was hidden under the cover name "Basic High Explosive Research". "Basic"
44880-517: Was published in the Proceedings of the Royal Society . He was awarded his doctorate on 6 September 1925. During this time he was an assistant to the Russian physicist Peter Kapitza , who was working on the physics of magnetic fields in extremely low temperatures. Cockcroft helped with the design and construction of helium liquefiers. In 1919, Rutherford had succeeded in disintegrating nitrogen atoms with alpha particles emitted from decaying radium atoms. This and subsequent experiments hinted at
45100-440: Was soon dropped and it became simply "High Explosive Research" (HER). Uranium was the only known fuel for nuclear reactors, so securing an adequate supply was crucial to the British atomic energy programme. During the war, Britain took the lead in reopening the world's richest uranium mine, the Shinkolobwe mine in the Belgian Congo , which had been flooded and closed, as 30 per cent of the stock in Union Minière du Haut Katanga ,
45320-453: Was stockpiled in Britain because the McMahon Act did not permit it to be exported from the United States. Groves extended the arrangement into 1947, and another 1,400 long tons (1,400 t) was shipped to Britain, all of which was added to the Springfields stockpile. Its growing size was the principal reason the Americans reopened the negotiations resulting in the Modus Vivendi , which allowed for limited sharing of technical information between
45540-400: Was subsequently transferred to the Associated Electrical Industries Laboratory at Aldermaston , under Allibone's direction. Research independently began at Oxford University under Peter Thonemann. In 1951, Cockcroft arranged for the Oxford group to be transferred to Harwell. Cockcroft approved the construction of ZETA (Zero Energy Thermonuclear Assembly) by the Thonemann's Harwell group, and
45760-415: Was that if a shell could explode when it was near an enemy aircraft, a near miss would be nearly as effective as a direct hit. The technical problem was to miniaturise a radar set, and make it sturdy enough to be fired from a gun barrel. The second problem had been solved by the Germans; a dud German bomb was salvaged that had valves that could withstand the acceleration. Plans were given to the Americans by
45980-493: Was that motes of polonium could propel themselves through the air using their own alpha particle emissions. Safety procedures had to be tightened. It was produced at Windscale by irradiation of bismuth . A special plant was built there to extract it, but it was not operational until June 1952. The final product was just 500 curies (18,000 GBq) of polonium, less than 1 mg. It was only just available on time for Operation Hurricane. Atomic bomb A nuclear weapon
46200-744: Was the Special Atomic Demolition Munition , or SADM, sometimes popularly known as a suitcase nuke . This is a nuclear bomb that is man-portable, or at least truck-portable, and though of a relatively small yield (one or two kilotons) is sufficient to destroy important tactical targets such as bridges, dams, tunnels, important military or commercial installations, etc. either behind enemy lines or pre-emptively on friendly territory soon to be overtaken by invading enemy forces. These weapons require plutonium fuel and are particularly "dirty". They also demand especially stringent security precautions in their storage and deployment. Small "tactical" nuclear weapons were deployed for use as antiaircraft weapons. Examples include
46420-444: Was the British project that had already been penetrated by atomic spies for the Soviet Union . The United Kingdom did not have the manpower or resources of the United States, and despite its early and promising start, Tube Alloys fell behind its American counterpart and was dwarfed by it. On 30 July 1942, Anderson advised the Prime Minister, Winston Churchill , that: "We must face the fact that ... [our] pioneering work ...
46640-445: Was the director of the Montreal Laboratory , Hans von Halban , who was a poor administrator, did not work well with the Canadians, and was regarded as a security risk by the Americans. In April 1944 a Combined Policy Committee meeting at Washington agreed that Montreal Laboratory scientists who were not British subjects would leave, and Cockcroft would become the new director of the Montreal Laboratory in May 1944. On 24 August 1944,
46860-464: Was the first Master of Churchill College, Cambridge . He was also chancellor of the Australian National University in Canberra from 1961 to 1965. John Douglas Cockcroft, also known as "Johnny W.", was born in Todmorden , West Riding of Yorkshire , England, on 27 May 1897, the eldest son of a mill owner, John Arthur Cockcroft, and his wife Annie Maude née Fielden. He had four younger brothers; Eric, Philip, Keith and Lionel. His early education
47080-438: Was the junior partner in the Grand Alliance . The British considered the Quebec Agreement to be the best deal they could have struck under the circumstances, and the restrictions were the price they had to pay to obtain the technical information needed for a successful post-war nuclear weapons project. Margaret Gowing noted that the "idea of the independent deterrent was already well entrenched." The Quebec Agreement established
47300-452: Was the most complicated of all from an engineering point of view. Uranium hexafluoride gas was pumped into a cascade , becoming richer in uranium-235 at each stage as it passed through a series of membranes. Procuring the nickel powder used by the Manhattan Project was not a problem, as it came from a British firm. Once again, a Royal Ordnance Factory was chosen as the site, in this case ROF Capenhurst at Capenhurst , near Chester , which had
47520-419: Was the most powerful research reactor in the world. Originally designed in July 1944 with an output of 8 MW, the power was raised to 10 MW through design changes such as replacing uranium rods clad in stainless steel and cooled by heavy water with aluminium-clad rods cooled by light water. Cockcroft was shocked when he was informed on 10 September 1945 that the British physicist Alan Nunn May , who worked at
47740-511: Was then dissolved in ether , drawn off and precipitated by the addition of ammonia, producing ammonium diuranate . The ammonium diuranate was heated in a furnace and reduced with hydrogen and hydrofluoric acid to produce uranium tetrafluoride . Heating and mixing with calcium metal reduced it to metallic uranium, leaving calcium fluoride behind as a slag . The metallic uranium was then cast into billets . These were extruded into rods and sealed in aluminium cans. The first nuclear reactor in
47960-427: Was thought there would be no particulate for the filters to catch. As well, the uranium oxide at Oak Ridge turned out to be from the chemical plant and not the reactor. The filters therefore became known as "Cockcroft's Folly". However, when the core of one of the two reactors ignited the Windscale fire of 1957, the filters prevented a far worse release of radioactive material. Terence Price, future scientific advisor at
48180-417: Was transferred from the Department of Scientific and Industrial Research to the Ministry of Supply effective 1 November 1945. To coordinate the atomic energy effort, it was decided to appoint a Controller of Production, Atomic Energy (CPAE). The Minister of Supply , John Wilmot , suggested Marshal of the Royal Air Force Lord Portal , the wartime Chief of the Air Staff . Portal was reluctant to accept
48400-411: Was unlikely to be ready in time to affect the outcome of the war in Europe . The unanimous response was that before embarking on this, another effort should be made to secure American cooperation. At the Quadrant Conference in August 1943, Churchill and the American President, Franklin Roosevelt , signed the Quebec Agreement , which merged the two national projects. Its terms made it clear that Britain
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