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Tube Alloys was the code-name for the British nuclear weapon directorate during World War II, when the development of nuclear weapons was kept at such a high level of secrecy that it had to be referred to by code even in the highest circles of government. Later in the war, tube alloy came to refer specifically to the synthetic element plutonium, whose very existence was secret until its use in the atomic bombing of Nagasaki.

The Tube Alloys programme in Britain and Canada, effectively the first nuclear weapons project of its type, was eventually subsumed into the American Manhattan Project. However the programme had its origins in France and Germany.

The Paris Group

Otto Hahn in Germany and Lise Meitner, exiled in Swedenmarker, reported nuclear fission in uranium in 1938. This was followed up by a group of scientists at the Collège de Francemarker in Parismarker: Frédéric Joliot-Curie, Hans von Halban, Lew Kowarski, and Francis Perrin. In February 1939, the Paris Group showed that when fission occurs in a uranium nucleus, two or three extra neutrons are also given off. This important observation suggested that a self-sustaining chain reaction might be possible. It was immediately apparent to many scientists that, in theory, an extremely powerful explosive could be created, an atomic bomb, but many scientists thought a practical bomb was an impossibility.

Francis Perrin of the Paris Group then defined a critical mass of uranium to be the smallest amount that could sustain a chain reaction. However, it was found that natural uranium cannot sustain a chain reaction without a moderator to slow down the fast-moving neutrons given off by the fission.

Early in 1940, the Paris Group decided on theoretical grounds that heavy water would be an ideal moderator. They asked the French Minister of Armaments to obtain as much heavy water as possible from the only source, the large hydroelectric station at Vemorkmarker in Norwaymarker. The French then discovered that Germany had already offered to purchase the entire stock of Norwegian heavy water, indicating that Germany might also be researching an atomic bomb. The French told the Norwegian government of the possible military significance of heavy water. Norway then gave the entire stock to a French Secret Service agent, who secretly brought it to France via England, just before Germany invaded Norway in April 1940. When Germany invaded France in May 1940, the Paris Group moved to Cambridgemarker and brought the heavy water inventory of 188 litres. Joliot-Curie remained in France and became an active worker in the French Resistance movement.

Frisch and Peierls

At first British research correctly concluded that an atomic bomb using natural uranium is impossible with fast neutrons, because too many neutrons get lost or captured by the uranium-238 atoms. However, in February 1940, Otto Frisch and Rudolf Peierls, two exiled German scientists living in England realised that an atomic bomb could be built and detonated using only a few kilograms of uranium-235, the lighter rare isotope of uranium, using only fast neutrons. Frisch and Peierls reported in their famous Frisch-Peierls memorandum that if uranium-235 is completely separated from uranium-238, there is no need to slow the neutrons down, so no moderator was required.

Frisch and Peierls reported to their professor Mark Oliphant who informed Henry Tizard who formed, in April 1940, a top-secret committee of experts (later known as the MAUD Committee) to investigate the feasibility of an atomic bomb. The memo prompted the MAUD Report which in turn led to the Tube Alloys project, part of which included secret development work carried out by Britain's Imperial Chemical Industries Ltd (ICI) based at Billingham, Northeast England.Evidence in a TV programme transmitted by Tyne Tees Television (Northern Life) established a connection between work carried out at ICI and nuclear material.

The USSR got details of British initial research, from Klaus Fuchs and possibly also Austrian expatriate Engelbert Broda, and John Cairncross, though Alan Nunn May was recruited later in Canada. Lavrenty Beria’s report to Stalin of March 1942 had the MAUD report and other British documents.

Tizard Mission

The heavy water team from France was invited to continue its slow neutron research at Cambridge Universitymarker; but the project was given a low priority since it was not expected to produce a bomb.

A delegation (the Tizard Mission) was sent in September 1940 to North America to exchange technology in all fields, such as radar, jet engines and nuclear research. They also explored the possibility of relocating the British military research facilities in North America, out of reach of the German bombers.

When the Tizard Mission returned they reported on the slow neutron researches being conducted in Cambridge (by the Paris Group), at Columbia University by Enrico Fermi and in Canada by George Laurence. They concluded that they were irrelevant to the war effort.

Isotopic separation

The biggest problem faced by the MAUD Committee was to find a way to separate the 0.7% of uranium-235 from the 99.3% of uranium-238. This is difficult because the two types of uranium are chemically identical. However, Franz Simon had been commissioned by MAUD to investigate methods. Simon reported in December 1940 that gaseous diffusion was feasible, calculating the size and cost of the industrial plant needed. The MAUD Committee realised that an atomic bomb was "not just feasible; it was inevitable".

The chemical problems of producing gaseous compounds of uranium and pure uranium metal were studied at the University of Birminghammarker and Imperial Chemical Industries (ICI). Dr Philip Baxter at ICI made the first small batch of gaseous uranium hexafluoride for Professor James Chadwick in 1940. ICI received a formal contract later in 1940 to make 3 kg of this vital material for the future work.


The breakthrough with plutonium was at the Cavendish Laboratorymarker by Egon Bretscher (1901-1973) and Norman Feather (1904-1978).They realised that a slow neutron reactor fuelled with uranium would in theory produce substantial amounts of plutonium-239 as a by-product. This is because U-238 absorbs slow neutrons so forming a new isotope U-239. The new isotope's nucleus rapidly emits an electron through beta decay producing a new element with a mass of 239 and an atomic number of 93. This element's nucleus then also emits an electron and becomes a new element of mass 239 but with an atomic number 94 and a much greater half-life. Bretscher and Feather showed theoretically feasible grounds that element 94 would be readily 'fissionable' by both slow and fast neutrons, and had the added advantage of being chemically different from uranium and therefore could easily be separated from it.

This new development was also confirmed in independent work by Edwin M. McMillan and Philip Abelson at Berkeley Radiation Laboratory also in 1940. Nicholas Kemmer of the Cambridge team proposed the names neptunium for the new element 93 and plutonium for 94 by analogy with the outer planets Neptune and Pluto beyond Uranus (uranium being element 92). The Americans fortuitously suggested the same names. The production and identification of the first sample of plutonium in 1941 is generally credited to Glenn Seaborg, who used a cyclotron rather than a reactor.

Oliphant's visit to the United States

When there was no reaction from America to the reports of the MAUD Committee, Mark Oliphant crossed the Atlantic in an unheated bomber in August 1941. He found that Lyman Briggs had not circulated the reports to the Uranium Committee, but had kept them in a safe. Oliphant then contacted Ernest Lawrence, James Conant, Enrico Fermi and Arthur Compton and managed to increase the urgency of the American research programs. The MAUD Reports finally made a big impression. Overnight the Americans changed their minds about the feasibility of an atomic bomb and suggested a cooperative effort with Britain. Harold C. Urey and George Braxton Pegram were sent to the UK in November 1941, to confer but Britain did not take up the offer of collaboration. The offer lapsed without any action being taken.

Montreal Laboratory

The American effort increased rapidly and soon outstripped the British. However, separate research continued in each country with some exchange of information. Several of the key British scientists visited the USA early in 1942 and were given full access to all of the information available. They were astounded at the momentum that the American atomic bomb project had then assumed.

In June 1942 the US Army took over process development, engineering design, procurement of materials and site selection for pilot plants. As a result the information flow to Britain dried up. The Americans stopped sharing any information on heavy water production, the manufacture of uranium hexafluoride, the method of electromagnetic separation, the physical or chemical properties of plutonium, the details of bomb design, or the facts about fast neutron reactions. This was a major disappointment which hindered the British and the Canadians, who were collaborating on heavy water production and several other aspects of the research program.

The slow neutron research at the Cavendish Laboratorymarker, Cambridge University which the British had thought was not relevant to bomb-making, suddenly acquired military significance, because it provided the route to plutonium. The British Government wanted the Cambridge team to be relocated in Chicago, where the American research was being done but the Americans had become very security-conscious. Only one of the six senior scientists in the Cambridge group, which had originated in Paris, was British. They were therefore sent to Montrealmarker, Canada.

The first eight staff arrived in Montreal at the end of 1942, and occupied a house belonging to McGill Universitymarker. Three months later they moved into a 200 square metre area in a new building at the University of Montrealmarker. The laboratory grew quickly to over 300 staff; about half were Canadians recruited by George Laurence. A subgroup of theoreticians was recruited and headed by a Czechoslovak physicist George Placzek. Placzek proved to be a very capable group leader, and generally regarded as the only member of the staff with the stature of the highest scientific rank and close personal contacts to many key physicists involved in the Manhattan project. The Director of the laboratory was Hans von Halban, but he proved to be an unfortunate choice as he was a poor administrator, and did not work well with the National Research Council of Canadamarker. The Americans saw him as a security risk, and objected to the French atomic patents claimed by the Paris Group (in association with ICI).

The Montreal team in Canada depended on the Americans for supplies of heavy water from the US heavy water plant in Trail, British Columbiamarker (which was under American contract), as well as technical information about plutonium. The Americans said that they would give heavy water to the Montreal group only if it agreed to direct its research along the limited lines suggested by du Pont. Despite doing much good work, by June 1943 work at the Montreal Lab had come to a complete standstill. Morale was low and the Canadian Government proposed cancelling the project. The Quebec Agreement in 1943 had led to more co-operation with America, though most of the British Mission scientists were based at Berkeley or Los Alamos.

In April 1944 a Combined Policy Committee meeting at Washington agreed that Canada would build a heavy water reactor. Scientists who were not British subjects would leave, and John Cockcroft would become the new Director of the Montreal Laboratory. The Americans fully supported the project with information and visits. They also supplied material e.g. uranium and heavy water. The Chalk River Laboratoriesmarker opened in 1944, and in 1946 the Montreal Laboratory was closed. The project developed the ZEEP reactor.

The Quebec Agreement

Winston Churchill then sought information about building Britain's own diffusion plant, a heavy water plant and an atomic reactor in Britain, despite its immense cost. However, in July 1943, in London, American officials cleared up some major misunderstandings about British motives, and after many months of negotiations the Quebec Agreement was finally signed by Churchill and U.S. President Franklin D. Roosevelt on 19 August 1943. The British then handed over all of their material to the Americans and in return received the copies of all the American progress reports to the President. The British effort was then subsumed into the Manhattan Project until after the war.

In a section of the Quebec Agreement formally entitled "Articles of Agreement governing collaboration between the authorities of the U.S.A. and UK in the matter of Tube Alloys", Britain and the USA agreed to share resources "to bring the Tube Alloys [i.e. the Atomic Bomb] project to fruition at the earliest moment."

The leaders agreed that
  • "we will never use this agency against each other,
  • "we will not use it against third parties without each other's consent, and
  • "we will not either of us communicate any information about Tube Alloys to third parties except by mutual consent."

It was also agreed that any post-war advantages of an industrial or commercial nature would be decided at the discretion of the U.S. President.

William Penney, one of the Tube Alloys scientists was an expert in shock-waves. In June 1944 he went to America to work at Los Alamos as part of the British delegation to the Manhattan Project. His leadership qualities and his ability to work in harmony with others resulted in him being added to the core group of scientists who made all key decisions in the direction of the program.

In 1945, U.S. President Harry S. Truman had agreed to Churchill's request that British observers could witness the dropping of the bomb on Japan. But when Group Captain Leonard Cheshire and Professor William Penney went to Tinian, they were not allowed by Groves and/or LeMay to go on the Hiroshima flight, and only after protests went in the observation plane Big Stink on the Nagasaki flight. While Penney knew much of the theory of the Project, so did other members of Project Alberta who also flew over Japan.

The Smyth Report was issued by the U.S. War Department on 12 August 1945, giving the story of the atomic bomb and including the technical details that could now be made public. It made few references to the British contribution to the bomb, and a White Paper, Statements Relating to the Atomic Bomb was hurriedly drafted by Michael Perrin. This account was issued just after Attlee had replaced Churchill as Prime Minister, and was the only official statement on the British contribution for fifteen years.


The Atomic Energy Research Establishmentmarker (AERE or the Harwell Laboratory) near Harwell, Oxfordshiremarker was established by John Cockcroft in 1946 as the main centre for military and civilian atomic energy research and development in Britain. Former RAF bases were selected for AERE and AWRE as they were isolated, with large hangars. Hans von Halban was invited back to the UK by Frederick Lindemann (Lord Cherwell) to lead a team at the nearby Clarendon Laboratorymarker in Oxford Universitymarker, and worked there for eight years until 1955.

At the end of the war the British government believed that America would share the technology, which the British saw as a joint discovery. However, the passing of the McMahon Act (Atomic Energy Act) by the Truman administration in August 1946 made it clear that Britain would be no longer be allowed access to US atomic research. This partly resulted from the arrest for espionage of Alan Nunn May in 1946.

Clement Attlee's government decided that Britain required the atomic bomb to maintain its position in world politics. In the words of Foreign Secretary Ernest Bevin - "That won't do at all .. we've got to have this .. I don't mind for myself, but I don't want any other Foreign Secretary of this country to be talked to or at by a Secretary of State in the United States as I have just had in my discussions with Mr Byrnes. We've got to have this thing over here whatever it costs .. We've got to have the bloody Union Jack on top of it." Dr Penney left the United States and returned to the UK where he initiated his plans for an Atomic Weapons Section. The project was code-named High Explosive Research (or HER). In May 1947, Dr Penney was appointed to lead the project, based at the Royal Armament Research Development Establishment (RARDE) at Fort Halsteadmarker and the Royal Arsenalmarker at Woolwich (AWE).

In April 1950 an abandoned World War II airfield, RAF Aldermastonmarker in Berkshire was selected as the permanent home for Britain's nuclear weapons program. This was to become the Atomic Weapons Research Establishmentmarker (AWRE). On 3 October 1952, under the code-name "Operation Hurricanemarker", the first British nuclear device was successfully detonated off the west coast of Australia in the Monte Bello Islands.

In 1958 the US-UK Mutual Defence Agreement was signed, providing for nuclear weapons cooperation with the United States.

Other people

Other people associated with Tube Alloys are:
  • Boris Davison: Mathematician involved in critical mass calculations, see

External links



General references

  • Statements Relating to the Atomic Bomb (August 1945, HMSO; British Government White Paper)
  • Cathcart, Brian Test of Greatness: Britain's Struggle for the Atom Bomb (1995, John Murray, London) ISBN 0719552257
  • Clark, Ronald W. The Birth of the Bomb: Britain’s part in the weapon that changed the World (1961, Phoenix House, London)
  • Ehrman, J The Atomic Bomb: An Account of British Policy in the Second World War (1953, Cabinet Office, London)
  • Gowing, Margaret Britain and Atomic Energy 1939-1945 (1964, Macmillan, London)
  • Paul, Septimus H Nuclear Rivals: Anglo-American Atomic Relations, 1941-1952 (2000, Ohio State University Press, USA) ISBN 0-8142-0852-5
  • Szasz, Ferenc Morton British Scientists and the Manhattan Project: The Los Alamos Years (1992, Macmilllan, London & St Martin's Press, New York) ISBN 0312061676

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