RAF Harwell was a Royal Air Force airfield in Berkshire, England, near the village of Harwell.
From its opening in February 1937 until March 1944 various bomber squadrons were stationed at the airfield. On the outbreak of war it became part of No. 38 Group RAF, initially used for leaflet dropping missions over France using Wellington bombers, then later for bombing raids on Bremen, Cologne and Essen. There were numerous Luftwaffe raids on the airfield from August 1940 until September 1941. The original grass field was replaced with concrete runways between July and November 1941, but the runway was never very satisfactory: it ran over a hill on the downs above the village of Harwell, the end of the runway was not visible from the dispersal point (i.e. an aircraft commencing its run could not see if the end of the runway was clear), and the ammunition dump was at the end of the runway!
In March 1944 it was reallocated to 30 Group Airborne Forces, mainly flying tug aircraft towing Horsa gliders. These gliders were used in a number of operations including carrying troops into Normandy to secure vital strategic positions in advance of the main landings on D-Day; indeed the first glider-borne troops to arrive in Normandy on D-Day came from RAF Harwell. A memorial to the men from RAF Harwell who were killed on this operation can be seen at one edge of the old airfield site, and a memorial service is held there annually. The airfield was also used briefly for SOE operations between July and September 1944.
Dates and operations:
02/37 to 09/39: Bomber Command station with 105, 107 and 226 Sqns in training.
09/39 to 03/44: No. 3 Group Pool with Wellingtons, then No. 15 OTU from 04/40. Flew many leaflet missions to France, later bombing raids to Bremen, Cologne and Essen.
08/40 to 09/41: Many Luftwaffe attacks on the airfield.
07/41 to 11/41: 15 OTU moved to Mount Farm while the airfield closed and new concrete runways were built.
04/44 to 09/44: No. 38 Group Airborne Forces, 295 and 570 Squadrons with Albermarles (Stirlings after D-Day) towing Horsa gliders in training for drops on D-Day, and for the unsuccessful crossing of the Rhine at Nijmegen ("A bridge too far").
07/44 to 09/44: secret operations over Europe for SOE.
10/45 to 07/45: No. 13 OTU training with Mitchells, Bostons then Mosquitoes.
07/45 to 12/45: Transport Command briefly used the airfield before its closure.
Atomic Bomb Research and Development
Just as the “phoney war” ended in Europe the planned end of the war was seen to be atomic weapons. Two recently exiled atomic scientists, Otto Frisch and Rudolf Peierls wrote a memorandum on the construction of "a radioactive super-bomb". Forwarded to the Ministry of Aircraft Production, it caused the British Government to establish the secret Maud Committee to evaluate the possibilities and to oversee nuclear research. Similar steps had already been taken in the United States (the "Manhattan Project"), all of which eventually led to an operational atomic bomb.
British scientists worked initially alone on the atomic bomb. The report on nuclear research by the Maud Committee led to the setting up of a development programme by Imperial Chemical Industries with the cover codename of "Tube Alloys". It oversaw both atomic bomb and reactor work.
Anglo-US Talks: Winston Churchill flew to Washington DC for another series of meetings with President Roosevelt. They agreed to share nuclear research and to concentrate the work in the United States. The resulting "Manhattan Project" was put under military control in September 1942.
The world's first atomic reactor went critical at Chicago University. By now problems had arisen over the sharing of the US work with Britain.
British Politics: Winston Churchill's Conservative Party was swept from power and the Labour Party under Clement Attlee took over the reins of the wartime Coalition Government. The new Prime Minister travelled to Potsdam for the rest of the conference.
United States: Franklin Roosevelt died in America on the 12th and Vice President Truman was sworn in as President of the United States. Britain and especially Winston Churchill lost a great friend who did much to bolster the country at a time when the British Empire stood alone, and many Americans were staunchly isolationist. Harry Truman was soon faced with the decision whether or not to use the A-bomb.
The world's first A-bomb was successfully exploded at Alamogordo, New Mexico on the 16th July in Operation 'Trinity'.
6th August: B-29 Superfortress "Enola Gay", flying from Tinian dropped the first atomic bomb on Hiroshima. The equivalent of 20,000 tons of TNT killed 80,000 people.
9th August: The second A-bomb was detonated over Nagasaki and over 40,000 people died.
Britain goes it alone
It was US refusal to continue nuclear cooperation with the UK after World War II (the McMahon Act restricting foreign access to US nuclear technology was passed in 1946) which eventually prompted the building of a British bomb. President Truman met with Clement Attlee, and Attlee's request for the sharing of nuclear research secrets, as had been agreed between Churchill and Roosevelt, was not honoured - the original papers for the agreement had been "lost". However, in 1958 the "Agreement For Cooperation on the Uses of Atomic Energy for Mutual Defence Purposes" also known as the "Mutual Defence Agreement" was established, and this was renewed in 1994 and again in 2005.
The United Kingdom started independently developing nuclear weapons again shortly after the war. Labour Prime Minister Clement Attlee set up a cabinet sub-committee, the GEN.75 Committee (GEN.75), known informally as the "Atomic Bomb Committee", to examine the feasibility as early as 29 August 1945. In October 1946 Attlee called a small cabinet sub-committee meeting to discuss the building of a gaseous diffusion plant to enrich uranium. 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 the Secretary of State of the US as I have just been... 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." The committee, under pressure from Hugh Dalton and Sir Stafford Cripps to opt out of building the bomb due to its cost, eventually decided to go ahead not just because of considerations of Britain's prestige but also because of the likely industrial importance of atomic energy.
William Penney, a physicist specialising in hydrodynamics, was asked in October 1946 to prepare a report on the viability of building a UK weapon. He had joined the Manhattan project in 1944, had been in the observation plane Big Stink over Nagasaki, and had also done damage assessment on the ground following Japan's surrender. He had subsequently participated in the American Operation Crossroads test at Bikini Atoll. As a result of his report, the decision to proceed was formally made on 8th January 1947 at a meeting of the GEN.163 Committee of six cabinet members, including Prime Minister Clement Attlee, and Penney was appointed to take charge of the programme. The project was hidden under the name High Explosive Research (HER) and was based initially at the Ministry of Supply's Armament Research and Development Establishment (ARDE) at Fort Halstead, Kent.
So the project to build a British atomic bomb began in 1946 under the control of the Atomic Energy Research Establishment (incorporated into the United Kingdom Atomic Energy Authority (UKAEA) in 1954). It was civilian in character, but was also tasked with the job of producing the fissile material, initially only plutonium Pu-239, that was expected to be required for a military programme. Plants would be required for:
1. Research & Development
2. uranium ore processing
3. uranium and plutonium refining to weapons grade, and
4. bomb assembly.
These requirements were eventually filled by:
1. Harwell (then in Berkshire, but now Oxfordshire)
2. a former Royal Ordnance Factory (ROF) at Risley (Cheshire)
3. Capenhurst (Cheshire), and Calder Hall (Windscale, now called Sellafield, used to produce weapons grade Pu-239), and
4. a new site at AWRE Aldermaston, Berkshire, to which Penney's organisation had moved in 1950 from Fort Halstead. It was built in 1949 on the site of a former World War II Royal Air Force base and converted to nuclear weapons research, design and development in the 1950s. Although some early test devices were probably assembled on this site, final assembly of service-engineered weapons took place at the nearby site of Burghfield, built in 1941 and used for the nuclear programme from the early 1950s. Aldermaston was established by the Ministry of Supply, later becoming the Weapons Division of the (civilian) UKAEA, before being subsumed into the Ministry of Defence in the 1970s.
ROF Cardiff was used as part of the nuclear programme from 1961 until its closure in 1997. The site was used for the task of recycling old nuclear weapons and precisely shaping U-235 and metallic beryllium components for the boosted fission devices used as triggers in modern thermonuclear weapons.
An 8 Km² test range at Foulness was also used, and this was closed in 1996.
Although the British scientists knew the areas of the Manhattan Project in which they had been directly involved, they only had the sketchiest details of other parts, so these had to be independently researched. The gaseous diffusion plant at Capenhurst started production in 1953, producing low enriched uranium (LEU). By 1957 it was capable of annually producing 125Kg of highly enriched uranium (HEU). The capacity was further increased, and by 1959 was as high as 1600Kg per year. At the end of 1961 having produced between 3.8 and 4.9 tonnes of HEU it was switched back to LEU production for civil use. The Magnox electricity-producing power stations at Calder Hall (1956) and eight other electricity generating Magnox reactors at Chapelcross (1959) could produce Plutonium for use in the UK military nuclear programme. Seven other Magnox reactors came online between 1964 and 1971, although these were not necessarily used to generate material for warheads.
The choice of Harwell
The criteria for selection of a Research & Development site involved finding somewhere remote, with a good water supply, but within reach of good transport links and a university with a nuclear physics laboratory. This more or less limited the choice to Oxford or Cambridge. It had been decided that an RAF airfield would be chosen, the aircraft hangars being ideal to house the large atomic piles that would be needed. Although Cambridge University had the better nuclear physics facility (the Cavendish Laboratory), the RAF did not want to abandon any of the RAF stations in East Anglia (such as RAF Stradishall near Cambridge) since these were by now required to be V-bomber stations for the Cold War against the USSR. Eventually RAF Harwell was chosen: it had the necessary water supply and hangars requirements, was near Didcot for rail transport to London, and it was 16 miles from Oxford University. The RAF station was closed at the end of 1945 and the site transferred to the Ministry of Supply on 1 January 1946, becoming the Atomic Energy Research Establishment. It was a very bleak and muddy construction site during the hard winter of 1947. Many of the people who came to live in the parish of Harwell in the next two decades, causing the population to grow significantly, arrived for employment at the Harwell Laboratory or one of the other institutions on the "site" (e.g. the Rutherford Appleton Laboratory).
The Atomic Energy Research Establishment (known as AERE or colloquially Harwell) near Harwell, Oxfordshire, was the main centre for atomic energy research and development in the United Kingdom from the 1940s to the 1990s.
In 1945 John Cockcroft was asked to set up a research laboratory to further the use of nuclear fission for both military purposes and generating energy. The scientists mostly took over both accommodation and work buildings from the departing RAF.
The early laboratory had several specialist divisions: Chemistry (initially headed by Egon Bretscher, later by Robert Spence), General Physics (H.W.B. Skinner), Nuclear Physics (initially headed by Otto Frisch, later E. Bretscher), Reactor Physics (John Dunworth), Theoretical Physics (Klaus Fuchs, later Brian Flowers), Isotopes (Henry Seligmann) and Engineering (Harold Tongue, later Robert Jackson). Directors after Cockcroft included Basil Schonland, Arthur Vick and Walter Marshall.
Such was the interest in nuclear power and the priority devoted to it in those days that the first reactor, GLEEP, was operating by 15 August 1947. GLEEP (Graphite Low Energy Experimental Pile) was a low energy (3 kilowatt) graphite-moderated air-cooled reactor. It was the first reactor in Western Europe.
GLEEP used 11,500 natural uranium fuel aluminium-clad rods inserted into 676 horizontal fuel channels. It was initially used for investigations into reactor design and operation, and later for the calibration of instruments for measuring neutron flux. It was remarkably long-lived, operating until 1990. The fuel was removed in 1994 and the control rods and external equipment in 1995. A project to completely dismantle it was started in 2003 and completed in October 2004.
A successor to GLEEP, called BEPO (British Experimental Pile 0) built on the experiences with GLEEP, commenced operation in 1948. BEPO was shut down in 1968.
The BEPO chimney, a well-known landmark before its demolition in 2000. The brickwork at the base of this chimney formed an effective shield from cosmic rays, and consequently was used for housing the Radiocarbon Laboratory, where radiocarbon dates were calculated for archaeological material. The data processing for this in the 1980s was handled by a Research Machines RML380Z.
BEPO was a forerunner of the Windscale Piles and was used to demonstrate that commercial power reactors could be viable. It was primarily used for the production of radio-isotopes and for scientific research. At one time it was Europe’s main supplier of medical isotopes and in doing so assisted the evolution of the NHS. BEPO was an air-cooled reactor with a graphite moderator, and was fuelled by natural or low enriched uranium which generated a significant amount of heat. BEPO was a well known landmark on the Oxfordshire skyline as it had a 56m chimney. The volume of air pumped through the chimney was so large that it often acted as a giant organ pipe! Some inhabitants of Harwell village thought that the site workers could not be doing much, because there was never any smoke coming out of the chimney. BEPO closed after 20 years operation in 1968 when it was replaced by the material Testing Reactors DIDO and PLUTO. The fuel, coolant, fans and non-fixed items were removed as part of the Stage One decommissioning in 1969. The air outlet ducts leading from the reactor to the fan house and chimney were decontaminated in 1993/94 by the removal of their linings and filters.
Specialist demolition of the BEPO chimney, fan house, and administration block, former home of the Radiocarbon Laboratory
In 2000 specialist steeplejacks demolished the chimney. The bricks were monitored for contamination, and once proven radioactively clean were crushed and used as backfill material across the site. The 6m deep foundation of reinforced steel was dug out and monitored for contamination. The land surrounding BEPO has finally been restored as a nature reserve.
There is now no trace of BEPO or the Radiocarbon Laboratory
LIDO was an enriched uranium thermal swimming pool reactor which operated from 1956 to 1974 and was mainly used for shielding and nuclear physics experiments. It was fully dismantled and returned to a green field site in 1995.
A pair of larger 26 MW reactors, DIDO and PLUTO, which used enriched uranium with a heavy water moderator came online in 1956 and 1957 respectively. These small reactors were used primarily for testing the behaviour of different materials under intense neutron irradiation to help decide the most suitable materials for reactor components. Samples were irradiated for a few months to simulate the radiation dose that would be received over the lifetime of a power reactor. They also took over commercial isotope production from BEPO after that reactor was shut down. DIDO and PLUTO themselves were shut down in 1990 and the fuel, moderator and ancillary buildings removed. The current plans are to decommission the DIDO and PLUTO reactors by 2020.
One of the most significant experiments to occur at AERE was the ZETA fusion power experiment. An early attempt to build a large-scale nuclear fusion reactor, the project was started in 1954, and the first successes were achieved in 1957. In 1958 the project was shut down, as it was believed that no further progress could be made with the kind of design that ZETA represented. However, European tokomak fusion research has continued at the neighbouring site of Culham (the Joint European Torus (JET) and its successors).
Harwell Organisational History
In the turmoil following the Klaus Fuchs debacle a new proposal to construct a computer more or less went through "on the nod". This was to replace laborious engineering design calculations up to then produced using mechanical calculators and printed mathematical tables. Thus in 1951 the "Harwell Computer" (later the Harwell Dekatron Computer) was commissioned (see below). In 1954 AERE was incorporated into the newly formed United Kingdom Atomic Energy Authority (UKAEA). Harwell and the other laboratories were to assume responsibility for atomic energy research and development, and were part of the Department of Trade and Industry (DTI). At the end of the 1950s there were over 6,000 people working at Harwell and the reputation of the site changed from a "secret atomic station" to a world renowned laboratory solving technical problems. During the 1980s the slowdown of the British nuclear energy program resulted in a greatly reduced demand for the kind of work being done by the UKAEA. Pressures on government spending also reduced the funding available. Reluctant to merely disband a quality scientific research organisation, UKAEA was required to divert its research effort to the solving of scientific problems for industry by providing paid consultancy or services. UKAEA was ordered to operate on a Trading Fund basis, i.e. to account for itself financially as though it was a private corporation, while remaining fully government owned. By 1985 it was earning £50m a year from contracts which included finding defects in railway lines, radiocarbon dating and metal fatigue in Big Ben!
After several years of transition, UKAEA was divided in the early 1990s. UKAEA retained ownership of all land and infrastructure and of all nuclear facilities, and of businesses directly related to nuclear power. The remaining activities and services were privatised as AEA Technology and floated on the London Stock Exchange. Harwell Laboratory contained elements of both organisations, although the land and infrastructure was still owned by UKAEA.
At the same time the name "Atomic Energy Research Establishment" was dropped, and the site became known as the Harwell International Business Centre. The adjacent site known as Chilton/Harwell Science Campus houses the Rutherford Appleton Laboratory (including the ISIS neutron source and Diamond Light Source). In 2007 both sites started to use the name Harwell Science and Innovation Campus. In February 2009 the nuclear facilities became part of Research Sites Restoration Limited (RSRL), who are decommissioning the site on behalf of the Nuclear Decommissioning Authority.
APPENDIX 1: John Douglas Cockcroft
Sir John Douglas Cockcroft, OM, KCB, CBE (1897 – 1967) was a British physicist. He received the Nobel Prize in Physics for splitting the atomic nucleus, and was instrumental in the development of nuclear power.
Cockcroft was born in Todmorden, England, the eldest son of a mill owner. He was educated at Todmorden Secondary School (1909 – 1914) and studied mathematics at the Victoria University of Manchester (1914 – 1915).
During the First World War he served as a signaller in the Royal Artillery from 1915 to 1918.
After the war ended he studied electrotechnical engineering at Manchester College of Technology from 1919 until 1920, and then read mathematics at St. John's College, Cambridge University until 1924. He began research work under Ernest Rutherford, and in 1929 he was elected a Fellow of St. John's College.
In 1928 he began to work on the acceleration of protons with Ernest Walton. In 1932, they bombarded lithium with high energy protons and succeeded in producing helium and other chemical elements. This was one of the earliest experiments to change the atomic nucleus of one element to a different nucleus by artificial means.
At the outbreak of the Second World War he took up the post of Assistant Director of Scientific Research in the Ministry of Supply, working on radar. In 1944, he took charge of the Canadian Atomic Energy project and became Director of the Montreal Laboratory and Chalk River Laboratories, replacing Hans von Halban, who was considered a security risk.
In 1946, he returned to Britain to set up the Atomic Energy Research Establishment (AERE) at Harwell and other sites, charged with developing Britain's atomic weapons and power programme. As director of the AERE, he famously insisted that the coolant discharge chimney stacks of the Windscale Plutonium production reactors be fitted, at great expense, with high performance filters. The reactors were designed to remain clean and uncorroded during use, so it was not considered that there would be any particles present for the filters to catch. Having been fitted after the chimneys were built, they produced a characteristic bulge, and these filters were known as Cockcroft's Folly right up until the 1957 Windscale disaster, when the core of one of the two reactors caught fire and produced many radioactive particles. The Cockcroft filters prevented a disaster from becoming a catastrophe, at which point the nickname fell out of favour.
Cockcroft was made a Commander of the Order of the British Empire in 1944, and was knighted in 1948. In 1951, Cockcroft, along with Walton, was awarded the Nobel Prize in Physics for his work in the use of accelerated particles to study the atomic nucleus. He was created Knight Commander of the Order of the Bath in 1953. In 1959, he became the first Master of Churchill College, Cambridge. He was president of the Institute of Physics, the Physics Society, and the British Association for the Advancement of Science. Cockcroft served as chancellor of the Australian National University from 1961 to 1965. He received the American Atoms for Peace Award in 1961. He delivered the Rutherford Memorial Lecture in 1944. Named after him are: the Cockcroft building at the New Museums Site of the University of Cambridge; the Cockcroft Institute at Daresbury Laboratory in Cheshire; the Cockroft Hall lecture theatre at the Harwell Science and Innovation Centre; the Cockcroft building of the University of Brighton; the Cockcroft building of the University of Salford; and "Cockcroft Road" in the AERE housing estate in Didcot. Cockcroft died at Churchill College, Cambridge on 18.09.1967.
APPENDIX 2: Klaus Emil Julius Fuchs
Klaus Emil Julius Fuchs (1911 – 1988) was a German-born British theoretical physicist. Fuchs was born in Rüsselsheim, Germany, the third of four children to Lutheran pastor Emil Fuchs and his wife Else Wagner. Fuchs' father was later a professor of theology at Leipzig University. Fuchs attended both Leipzig University and Kiel University, and while at Kiel became active in politics. He joined the Social Democratic Party of Germany and, in 1932, the Communist Party of Germany. In 1933, after a violent encounter with the recently installed Nazis, he fled to France and was then able to use family connections to flee to Bristol, England.
He earned his PhD in Physics from the University of Bristol in 1937, studying under Nevill Mott, and took a DSc at the University of Edinburgh while studying under Max Born. His paper on quantum mechanics, published in the Proceedings of the Royal Society in 1936, helped win him a teaching position at Edinburgh the following year.
At the outbreak of war, German citizens in Britain were interned. Fuchs was put into camps on the Isle of Man and later in Quebec, Canada, from June to December 1940. However, Professor Born intervened on Fuchs' behalf. By early 1941, Fuchs had returned temporarily to Edinburgh. He was approached by Rudolf Peierls of the University of Birmingham to work on the "Tube Alloys" program – the British atomic bomb research project. Despite wartime restrictions, he was granted British citizenship in 1942 and signed an Official Secrets Act declaration form.
In late 1943, Fuchs transferred along with Peierls to Columbia University, in New York City, to work on the Manhattan Project. From August 1944 Fuchs worked in the Theoretical Physics Division at Los Alamos, New Mexico, under Hans Bethe. His chief area of expertise was the problem of imploding the fissionable core of the plutonium bomb. At one point, Fuchs did calculation work that Edward Teller had refused to do because of lack of interest. He was the author of techniques (such as the still-used Fuchs-Nordheim method) for calculating the energy of a fissile assembly which goes highly prompt critical. Later, he also filed a patent with John von Neumann, describing a method to initiate fusion in a thermonuclear weapon with an implosion trigger. Fuchs was one of the many Los Alamos scientists present at the Trinity test. Fuchs returned to England at the Harwell Atomic Energy Research Establishment as the first Head of the Theoretical Physics Division, and no. 2 to Cockcroft.
However, despite these undoubted contributions to nuclear research, Fuchs is chiefly remembered for his espionage and the passing of USA and UK secrets to the USSR. His initial Soviet contact on 10.08.1941 was known as "Sonia" (Ruth Werner, a German communist and a Major in Soviet Military Intelligence). As Fuchs later testified, after Nazi Germany invaded the Soviet Union in 1941 he concluded that the Soviets had a right to know what the United Kingdom (and later the United States) were working on in secret. Hence he began transmitting military intelligence to the USSR. Fuchs's testimony confirms that he contacted a former friend in the Communist Party of Germany, who put him in touch with someone at the Soviet embassy in Britain. His code-name was Rest. From late 1947 to May 1949, Fuchs gave Alexandre Feklisov, his case officer, the principal theoretical outline for creating a hydrogen bomb and the initial drafts for its development as the work progressed in England and America. Meeting with Feklisov six times, he provided the results of the test at Eniwetok Atoll of uranium and plutonium bombs and the key data on U.S. production of uranium-235. By revealing that America was producing just one hundred kilograms of uranium-235 and twenty kilograms of plutonium per month, Fuchs made it easy for Soviet scientists to calculate the number of atomic bombs the United States possessed. Thus the leaders of the Soviet Union knew the United States was not prepared for a nuclear war at the end of the 1940s, or even in the early 1950s. The information Fuchs gave Soviet intelligence in 1948 coincided with Donald Maclean's reports from Washington, D.C. It was obvious to Josef Stalin's strategists that the United States did not have enough nuclear weapons to deal simultaneously with the Berlin blockade and the Communists' victory in China.
Fuchs later testified that he passed detailed information on the project to the Soviet Union through a courier known as "Raymond" (later identified as Harry Gold) in 1945, and further information about the hydrogen bomb in 1946 and 1947. Fuchs attended a conference of the Combined Policy Committee (CPC) in 1947, a committee created to facilitate exchange of atomic secrets between the highest levels of government of the U.S., Great Britain and Canada; Donald Maclean (one of the famous "Cambridge spies"), as British co-secretary of CPC, was also in attendance.
In 1946 when Fuchs returned to England at the Harwell Atomic Energy Research Establishment as the first Head of the Theoretical Physics Division, he was confronted by intelligence officers as a result of the cracking of Soviet ciphers known as the VENONA Project. Under prolonged interrogation by MI5, Fuchs confessed in January 1950 that he was a spy. Fuchs told interrogators that the KGB acquired an agent in Berkeley, California, who informed the Soviet Union about electromagnetic separation research of uranium-235 in 1942 or earlier. He was prosecuted by Sir Hartley Shawcross, convicted on 01.03.1950, and sentenced to fourteen years in prison, the maximum possible for passing military secrets to a friendly nation (although this was in the infancy of the Cold War, the Soviet Union was still classed as an ally, or "friendly nation"). A week after this verdict the Soviet Union issued a terse statement denying that Fuchs had served as a Soviet spy.
Fuchs' statements to British and American intelligence agencies were used to implicate Harry Gold, a key witness in the trials of David Greenglass and Julius and Ethel Rosenberg in the USA. In December 1950 he was stripped of his British citizenship. He was released on 23.06.1959, after serving nine years and four months of his sentence at Wakefield Prison, and promptly emigrated to German Democratic Republic (East Germany). There he married a friend from his years as a student Communist, Margarete Keilson. He continued his scientific career and achieved considerable prominence. He was elected to the Academy of Sciences and the SED central committee, and was later appointed Deputy Director of the Institute for Nuclear Research in Rossendorf near Dresden, where he served until he retired in 1979. He received the Fatherland's Order of Merit and the Order of Karl Marx. He died near Dresden on 28 January 1988.
As a result of Fuchs' information, the first Soviet bomb, RDS-1 closely resembled the U.S.-developed Fat Man bomb. With the start of the Cold War there had been some warming of nuclear relations between the UK and US governments, which led to hopes of American cooperation. However these were quickly dashed by Fuchs' arrest and conviction, and led to the British independent nuclear programme. In East Germany Fuchs gave a tutorial to Chinese physicists, directly helping them to develop the first Chinese atomic bomb.
APPENDIX 3: The Harwell Dekatron Computer
Animated image of a Dekatron in operation
The 1951 Harwell Dekatron Computer.
Left to right: storage rack, ALU rack, and CPU (two racks of relays)
The Harwell Dekatron Computer at Wolverhampton as WITCH
2010 The Harwell Dekatron Computer being restored at Bletchley Park.
From the left there are two storage racks, the ALU rack, the CPU (two racks of relays with curved covers), and the power supply.
The Dekatron (also called three-phase gas counting tube, glow-transfer counting tube or cold cathode tube) is a gas-filled (hydrogen, neon or argon) decade or octal counting tube. Dekatrons were used in computers, calculators and other counting-related devices between the 1940s to 1970s. The base 10 dekatron was useful for computing, calculating and frequency-dividing purposes because one complete revolution of the neon dot in a dekatron meant 10 pulses on the guide electrode(s), and a signal could be derived from one of the ten cathodes in a dekatron to send a pulse, possibly for another counting stage. Dekatrons generally have a maximum input frequency in the high KHz range, 1 MHz being around the maximum possible.
Internal designs vary by the model and manufacturer, but generally a dekatron has ten cathodes arranged in a circle, guide electrodes between each pair of cathodes, and a common anode. When the guide electrode is pulsed, the neon gas will activate near the guide pins then "jump" to the next cathode.
Hydrogen dekatrons require high voltages ranging from 400 to 600 volts on the anode for proper operation; dekatrons with an inert gas usually require about 350 volts. When a dekatron is first powered up, a glowing dot will appear at a random cathode; the tube must be reset to zero state by driving a negative pulse into the designated starting cathode. Dekatrons fell out of practical use when transistor-based counters became reliable and affordable.
The Harwell Dekatron Computer, an early dekatron and relay-based computer, was originally built and used at the Atomic Energy Research Establishment at Harwell, Oxfordshire. The first name for the computer was the "Harwell Computer", but it was changed to the "Harwell Dekatron Computer" when a transistorised computer was purchased. Construction started in 1949, and the Dekatron Computer was operational in April 1951. It was found to be very reliable and performed calculations required for the design of the first UK atomic bomb. At the end of its life at Harwell it was retired for the first time in 1957; the Oxford Mathematical Institute ran a competition to award it to the college that could produce the best case for its future use. This competition was won by the Wolverhampton and Staffordshire College of Technology (which later became Wolverhampton University) where it was used to teach computing until 1973; it was redesignated the Wolverhampton Instrument for Teaching Computing from Harwell (WITCH). Retired a second time, the WITCH computer was donated to the Birmingham Museum of Science and Industry in 1973 and was displayed there for many years, until being disassembled and moved into storage at the Birmingham City Council Museums Collection Centre. In 2008 the Computer Conservation Society began a project to record its history; remarkably, it was found that all the pieces were still identifiable, so that a reconstruction was a realistic possibility. In September 2009 the machine was loaned to The National Museum of Computing at Bletchley Park, where it is to be restored to working order.
The machine used dekatrons for volatile memory (similar to RAM in a modern computer) and paper tape for both input and program storage. Output was to either a Friden teleprinter or to a paper tape punch. The machine used decimal numbers and initially had 20 8-digit dekatron registers for internal storage, later increased to 40 which appeared to be enough for nearly all calculations. It was assembled from components more commonly found in a British telephone exchange. Although it could on occasions act as a true stored-program computer, this was not its normal mode of operation, since instructions were usually read one at a time from paper tape, even for repetitive subroutines (which used a loop of paper tape). Frequent use of the tapes, using paper tape readers which sensed holes by metal plungers, eventually caused extra holes to appear, so modifiying the instructions or data; the damaged tapes then had to be replaced with new tapes, or special linen tapes were sometimes used. The multiplication time was between 5 and 10 seconds. However, it was very reliable, and could be left running for periods of days or even weeks, a remarkable achievement for a machine using thermionic tubes.
APPENDIX 4: The Harwell CADET
The Harwell CADET was a transistorised computer built at the Atomic Energy Research Laboratory, Harwell, Oxfordshire from about 1953 onwards. It was the first fully transistorised computer in Europe, and may have been the first fully transistorised computer in the world. CADET stood for "Computer Automatic Digital Electronic Transistor", which should be read backwards. In the above photograph the cylindrical object in the perspex box on the bench top on the left is the 64 Kbyte magnetic drum memory store with multiple moving heads that had been designed at the National Physical Laboratory. The main circuit boards were laid out in flat planes, unlike later machines which used card racks. This was probably because of the experimental nature of the machine. CADET was one of the few computers that used point-contact transistors, the very earliest type available. Most of the devices used were made by the UK company Standard Telephones and Cables. The machine was obsolete within a few years, due to the rapid evolution of both transistor and computer technology at that time.
By 1953 it was evident that the Harwell Dekatron Computer did not meet AERE's computing needs, and AERE director Sir John Cockcroft therefore encouraged his engineers to design and build a computer using transistors throughout. By the end of 1953 the team had transistor circuits operating to read and write on a small magnetic drum obtained from the Royal Radar Establishment. The machine used a low clock speed of only 58kHz to avoid having to use any valves to generate the clock waveforms. This slow speed was partially offset by the ability to add together eight numbers concurrently. CADET first ran a simple test program in February 1955. The machine was built from a few standardised designs of circuit boards which never got mounted into the planned desktop unit, so it was left in its breadboard form. From August 1956 CADET was offering a regular computing service, during which it often executed continuous computing runs of 80 hours or more.
The machine was described by its makers as being "probably the second fully transistorised computer in the world to be put to use", second to an unnamed IBM machine. Both the Manchester University Transistor Computer and the Bell Laboratories TRADIC machine using transistors were demonstrated before CADET was operational, although both required some vacuum tubes to supply their faster clock power, so those machines were not fully transistorised. In April 1955 IBM announced the IBM 608 transistor calculator, which was claimed to be "the first all solid-state computing machine commercially marketed" and "the first completely transistorised computer available for commercial installation", which may have been demonstrated in October 1954, before the CADET was fully operational.
By 1956 Brian Flowers, head of the theoretical physics division at AERE, was convinced that the CADET provided insufficient computing power for the needs of his numerical analysts and so he ordered a Ferranti Mercury computer. In 1958 Mercury number 4 became operational at AERE to accompany the CADET for another two years before the CADET was retired after four years' operation.
APPENDIX 5: Weapons
All the weapons were known by secret codenames of two words, the first word being a colour, and the second word some cultural allusion to the first word, or a random word with no meaning.
The first UK weapon test, Operation Hurricane, was detonated below the frigate HMS Plym anchored in the Monte Bello Islands on 02.10.1952. This led to the first deployed nuclear fission weapon, the Blue Danube free-fall bomb, in November 1953. The warhead was contained within a bomb casing measuring 1.6m diameter and 7.3m long, and being so large, could only be carried by the V-Bomber fleet. The first Blue Danube weapons issued to the RAF were of 10 – 12 Kiloton-of-TNT (42 – 50 TeraJoule) yield, implosion type, similar to the Nagasaki bomb. This Blue Danube airframe design was also used to house all the devices detonated at the Operation Grapple British nuclear tests of the hydrogen bomb held 1956 — 1958 at Malden Island and Christmas Island in the central Pacific Ocean. Fifty-eight Blue Danube bombs were produced, although archived declassified files indicate that only a small proportion of these were ever serviceable at any one time.
Ivy Mike, Mosaic and Grapple
The first hydrogen bomb was exploded by the USA in October 1952. Code-named Ivy Mike, the thermonuclear fuel consisted of liquid deuterium, contained in a device the
size of a house. Subsequent practical thermonuclear weapons used solid lithium deuteride as the thermonuclear component. On 27.07.1954 the UK Cabinet authorised the Lord President "to proceed with his plans for the production of thermonuclear bombs in this country". The main implications for the Atomic Energy Authority were requirements for thorium, heavy water, tritium and possibly Li-6. Harwell set up Project Crystal, which was targeted with the production of Li-6 in sufficient quantities for Britain’s thermonuclear programme, and experimental devices that included lithium were exploded in the Mosaic series in the summer of 1956, followed by the Grapple series of megaton tests in 1957.
A nuclear landmine dubbed Brown Bunny, later Blue Bunny, and finally Blue Peacock, used the Blue Danube warhead. It was developed from 1954 with the goal of deployment in the Rhine area of Germany. The system would have been set to an eight-day timer in the case of invasion of Western Europe by the Soviets, but this was cancelled in February 1958 with only two built. It was judged that the risks posed by the nuclear fallout and the political aspects of preparing for destruction and contamination of allied territory were simply too high to be justified.
Green Grass and Violet Club
The detonation by both the US and the Soviet Union of thermonuclear devices alarmed the UK government of Winston Churchill, and a decision was made on 27.07.1954 to begin development of a thermonuclear bomb, making use of the more powerful nuclear fusion reaction rather than nuclear fission. There was little or no dissent in the House of Commons. Meanwhile the UK deployed an Interim Megaton Weapon in the V-bomber fleet until a true thermonuclear weapon could be devised from the 1956 - 1958 Christmas Island tests. This never tested interim weapon, derived from the Orange Herald warhead tested at Christmas Island on 31.05.1957 yielding 720 Kt (3.0 PetaJoules), was known as Green Grass and was merely a very large unboosted pure fission weapon yielding 400 Kt (1.7 PJ). It was the largest pure fission weapon ever deployed by any nuclear state. Green Grass was first deployed in a modified Blue Danube casing and known as Violet Club. A later variant was deployed in a Yellow Sun Mk.1 casing.
Under the 1958 US-UK Mutual Defence Agreement 5.4 tonnes of UK produced Plutonium was sent to the US in return for 6.7 Kg of tritium and 7.5 tonnes of HEU over the period 1960 - 1979, replacing the Capenhurst production, although much of the HEU was used not for weapons, but as fuel for the growing UK fleet of about twelve nuclear submarines.
Red Snow and Yellow Sun
Yellow Sun practice bomb, courtesy of the RAF Cosford Reserve Collection, Stafford
the 1958 US-UK Mutual Defence Agreement also made fully developed and service-engineered designs available more quickly and more cheaply. The first of these was the US Mk.28 weapon which was anglicised and manufactured in the UK as Red Snow and quickly deployed as Yellow Sun Mk.2 in the V-bomber fleet.
Blue Steel, Skybolt and Blue Streak
Red Snow became the warhead of choice for the Blue Steel air-launched stand-off missile which remained in service until December 1970, and also for some of the Skybolt missiles purchased from the United States, and intended for carriage by the V-bombers. The Blue Steel extended range upgrade and Blue Streak ballistic missile projects were cancelled because of changing military perceptions of the vulnerability of these Blue Streak land-based liquid-fuelled missiles, the launch sites being too close to Soviet missile launch sites in Eastern Europe.
Similar changed military perceptions led to the removal of Thor intercontinental ballistic missiles in the UK. To some consternation, and considerable protests, the incoming Kennedy administration cancelled Skybolt at the end of 1962 because it was believed by the US Secretary of State for Defense, Robert McNamara, that other delivery systems were progressing better than expected, and a further expensive system was surplus to US requirements.
After the cancellation of Skybolt, the UK purchased Polaris missiles for use in UK-built ballistic missile submarines. The agreement between US President John F. Kennedy and UK Prime Minister Harold Macmillan, the Polaris Sales Agreement, was announced on 21.12.1962 and HMS Resolution sailed on her first Polaris-armed patrol on 14.06.1968.
Blue Danube remained in service until 1963, when it was replaced by Red Beard, a smaller tactical boosted fission weapon that used the same fissile core as Blue Danube, and was deployed on many smaller aircraft than the V-bombers both ashore and at sea aboard aircraft carriers. Stocks of Red Beard were maintained in Cyprus, Singapore, and the UK.
In the 1970s the UK Polaris warheads were vulnerable to the Soviet ABM screen concentrated around Moscow, and the UK developed a Polaris improved-front-end (IFE) codenamed Chevaline, designed to counter this ABM defence which threatened to completely nullify an independent UK deterrent posture. When Chevaline became public knowledge in 1980, it generated huge controversy as it had been kept secret by the four UK governments of Wilson, Heath, Wilson (again) and Callaghan, and was only disclosed by the Thatcher government. By the time it entered service in 1982 it had cost approx £1bn. The final Polaris/Chevaline patrol took place in 1996, two years after the first Trident-carrying submarine sailed on its first patrol.
The UK currently uses Vanguard class submarines armed with nuclear-tipped Trident missiles. The principle of operation is based on maintaining a deterrent effect by always having at least one submarine at sea. This strategy was designed for the Cold War period.
Replacement for Trident
A decision on the replacement of Trident was made on 04.12.2006. UK Prime Minister Tony Blair told MPs that it would be "unwise and dangerous" for the UK to give up its nuclear weapons. He outlined plans to slightly reduce the numbers of submarines and warheads, but said that although the Cold War had ended, the UK needed nuclear weapons, as no-one could be sure that another nuclear threat would not emerge in the future, or from where. The UK continues to permit the US to deploy nuclear weapons from its territory, the first having arrived in 1954. During the 1980s nuclear armed USAF Ground Launched Cruise Missiles were deployed at RAF Greenham Common and RAF Molesworth.
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The Staffordshire University Computing Futures Museum Harwell Page to Dr John
03 27 October 2010 updated by Dr John Wilcock