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101-830: The Windscale Piles were two air-cooled graphite-moderated nuclear reactors on the Windscale nuclear site in Cumberland (now known as Sellafield site , Cumbria ) on the north-west coast of England. The two reactors, referred to at the time as "piles", were built as part of the British post-war atomic bomb project and produced weapons-grade plutonium for use in nuclear weapons . Windscale Pile No. 1 became operational in October 1950 followed by Pile No. 2 in June 1951. They were intended to last five years, but operated for seven until shut down following

202-446: A 1946 paper that the reactor be encased in a pressure vessel. This would make it safer, and it would allow more heat to be obtained from a given core size. Another, by Risley engineers D. W. Ginns, H. H. Gott and J. L. Dickson, put forward a series of proposals to increase the efficiency of an air cooling system. These included adding fins to the aluminium cans containing the uranium fuel elements to increase their surface area; and having

303-663: A 30-mile (48 km) four-lane highway built in order to evacuate the Hanford area in an emergency. If such criteria were applied in the UK, all of England and Wales would have been ruled out, leaving only the north and west of Scotland. The possibility of building reactors in Canada was suggested by Chadwick and Cockcroft, and strongly supported by the Field Marshal Lord Wilson , the Chief of

404-548: A bluff overlooking the Calder River on the site. A single reactor was costed at £20   million, but two could be built for between £30   million and £35   million. The number needed depended on the number of bombs required. In their report to Attlee on 1 January 1946, the Chiefs of Staff recommended that two be built, but for the moment it was fixed at one reactor capable of producing 15 bombs per annum. In his address to

505-495: A build-up of potential energy. The British scientists were aware of this; it was one of the reasons for the choice of air-cooling over water cooling, as the water channels might have become blocked due to the expansion of the graphite. When Walter Zinn , the director of the Argonne National Laboratory , visited the UK in 1948, he provided additional information to the British scientists. The expansion, he informed them,

606-677: A close and successful partnership with Brigadier General Leslie R. Groves , the director of the Manhattan Project, and ensured that the British contribution to the Manhattan Project was complete and wholehearted. After the war ended the Special Relationship between Britain and the United States "became very much less special". The British government had trusted that America would continue to share nuclear technology, which it considered

707-404: A few months to simulate the radiation dose that it would receive over the lifetime of a power reactor. Both reactors were also used for neutron scattering crystallography. They took over commercial isotope production from BEPO after that was shut down. DIDO and PLUTO themselves were shut down in 1990 and the fuel, moderator and some ancillary buildings removed. The GLEEP reactor and the hangar it

808-454: A half years. To correct this, further design changes were mooted, but more tests at Chalk River indicated the expansion was not as great as that predicted from the American data, and on this basis Hinton decided to revert to the 1948 design. The graphite in each reactor was arranged in a 25-by-50-foot (7.6 by 15.2 m) octagonal stack weighing about 2,000 long tons (2,000 t). The reactor

909-486: A joint discovery, but little information was exchanged immediately after the war, and the Atomic Energy Act of 1946 (McMahon Act) officially ended technical cooperation. Its control of "restricted data" prevented the United States' allies from receiving any further research and development information. The British government saw this as a resurgence of United States isolationism akin to that which had occurred after

1010-523: A large one for nuclear power . Hinton estimated that dispensing with the water would reduce the costs by 40 per cent; the design was simpler and the time to build it was less. He recommended to Portal that design work on water-cooled reactors be dropped and all work concentrated on air-cooled and pressurised gas-cooled designs, the latter being seen as the way of the future. Work on water-cooled designs ended in April 1947. The location criteria were now relaxed, and

1111-554: A metallic sphere of pure uranium-235 , and found that as little as 1 to 10 kilograms (2.2 to 22.0 lb) might explode with the power of thousands of tons of dynamite. In response, the British government initiated an atomic bomb project, code-named Tube Alloys . The August 1943 Quebec Agreement merged Tube Alloys with the American Manhattan Project . As overall head of the British Mission, James Chadwick forged

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1212-469: A number of research or test reactors built that use graphite as the moderator. The first artificial nuclear reactor, Chicago Pile-1 , a graphite-moderated device that produced between 0.5 watts and 200 watts , was constructed by a team led by Enrico Fermi in 1942. The construction and testing of this reactor (an " atomic pile ") was part of the Manhattan Project . This work led to the construction of

1313-557: A powerful rush of heat. On 7 May 1952, Pile No. 2 experienced a mysterious rise in core temperature despite the fact that the pile had been shut down. The blowers were started, and the pile cooled down. Then, in September 1952, a rise in temperature was observed in Pile No. 1 while it was shut down. This time, smoke was observed coming from the core, which suggested that the graphite or fuel elements might be smouldering. The obvious means of cooling

1414-514: A proposal from Hinton that the second reactor be a pressurised-gas one. Plans for a third reactor were dropped in 1949 under American pressure to reduce the demand for uranium. The site was divided into three areas: a reactor area; a service area containing offices, boiler rooms , workshops, a fire station and other amenities; and a chemical area where the plant for separating plutonium was located, along with laboratories and other supporting infrastructure. Work commenced in September 1947. At its peak,

1515-436: A reactor, there are three key choices to be made: that of the fuel, the moderator , and the coolant. The first choice, that of fuel, was a Hobson's choice : the only fuel available was natural uranium, since there were no enrichment plants to produce uranium-235, and no reactors to produce plutonium or uranium-233 . This restricted the choice of moderators to heavy water and graphite . Although ZEEP had used heavy water, this

1616-771: A redesign of the reactors. All went well until late 1948, when the quality of the graphite from both companies suddenly and precipitously declined. Both sourced high grade petroleum coke from Sarnia, Ontario , where it was produced from the exceptional pure crude oil from the Loudon Oil Field in Illinois. Hinton flew to Canada and visited the refinery in Sarnia, where it was determined that the Loudon oil had not been properly segregated from oil from other fields. The graphite had to be cut into blocks and arranged so that there were channels through

1717-454: A uranium-235 bomb would require ten times the fissile material as one using plutonium to produce half the TNT equivalent . Estimates of the cost of nuclear reactors varied, but were about half that of a gaseous diffusion plant. Thus, a gaseous diffusion plant would cost ten times as much to produce the same number of atomic bombs each year. The decision was therefore taken in favour of plutonium. Part of

1818-474: Is heated above 250 °C (482 °F) it becomes plastic, and the Wigner dislocations can relax into their natural state. This process was gradual and caused a uniform release which spread throughout the core. This was first carried out when Pile No. 2 was powered down on 9 January 1953. Thermocouples were installed to measure the temperature in the core, and the blowers were shut down at 23:15. The reactor power

1919-799: The British Joint Staff Mission , and the Americans, but was rejected by the British government. Canada was outside the sterling area and construction costs could only be met by further borrowing from Canada. Under the circumstances, the reactors would be owned and controlled by the Canadian government, and this the British government could not accept. A consulting engineer firm was brought in to advise on possible locations. Two were suggested: Harlech in Wales and Arisaig in Scotland. Hinton opposed Harlech on

2020-665: The Chicago Pile-1 , used nuclear graphite as a moderator. Graphite-moderated reactors were involved in two of the best-known nuclear disasters: an untested graphite annealing process contributed to the Windscale fire (but the graphite itself did not catch fire), while a graphite fire during the Chernobyl disaster contributed to the spread of radioactive material. Several types of graphite - moderated nuclear reactors have been used in commercial electricity generation : There have been

2121-658: The Chiefs of Staff Committee recommended that Britain acquire nuclear weapons. They estimated that 200 bombs would be required by 1957. The 8 January 1947 meeting of the Gen 163 Committee, a subcommittee of the Gen 75 Committee, agreed to proceed with the development of atomic bombs, and endorsed Portal's proposal to place William Penney , the Chief Superintendent Armament Research (CSAR) at Fort Halstead in Kent, in charge of

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2222-572: The First World War . This raised the possibility that Britain might have to fight an aggressor alone. It also feared that Britain might lose its great power status, and therefore its influence in world affairs. The Prime Minister of the United Kingdom , Clement Attlee , set up a cabinet sub-committee , the Gen 75 Committee (known informally as the "Atomic Bomb Committee"), on 10 August 1945 to examine

2323-513: The SCRAM (AZ5) button was pressed to shut down the reactor, the control rods jammed in the middle of the core, causing a positive loop, since the nuclear fuel reacted to graphite. This has been dubbed the "final trigger" of events before the rupture. A graphite fire after the main event contributed to the spread of radioactive material. The massive power excursion in Chernobyl during a mishandled test led to

2424-418: The Windscale fire on 10 October 1957. Nuclear decommissioning operations commenced in the 1980s and are estimated to last beyond 2040. Visible changes have been seen as the chimneys were slowly dismantled from top-down; Pile 2's chimney being reduced to the height of adjacent buildings in the early 2000s. However, the demolition of pile 1 chimney has taken much longer as it was significantly contaminated after

2525-464: The X-10 Graphite Reactor at Oak Ridge National Laboratory , which was the first nuclear reactor designed and built for continuous operation, and began operation in 1943. There have been several major accidents in graphite-moderated reactors, with the Windscale fire and the Chernobyl disaster probably the best known. In the Windscale fire, an untested annealing process for the graphite

2626-522: The 1957 fire. The reactor cores still remain to be dismantled. The 1938 discovery of nuclear fission by Otto Hahn and Fritz Strassmann , and its explanation by Lise Meitner and Otto Frisch , raised the possibility that an extremely powerful atomic bomb could be created. During the Second World War , Frisch and Rudolf Peierls at the University of Birmingham calculated the critical mass of

2727-517: The 1970s 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. For example, an Operations Research Group

2828-592: The 1980s and the hostels were demolished or adapted for other uses. The 'Prefab' estates lasted until the early 1990s when the residents were transferred to local authority housing. The RAF prewar NCO married quarter housing at Harwell together other UKAEA housing in Abingdon, Grove, Wantage and Newbury totaling 129 houses were sold in their entirety to the Welbeck Estate Group in 1995 and following extensive refurbishment were sold to local buyers. The remote nature of

2929-605: The Americans had, it was doubtful whether the cash-strapped post-war British economy could afford the money or the skilled manpower that this would require. The scientists who had remained in Britain favoured uranium-235, which could be enriched with gaseous diffusion, and a final electromagnetic step. However, those who had been working at the Los Alamos Laboratory in America were strongly in favour of plutonium. They estimated that

3030-860: The Atomic Energy Research Establishment was formed, coming under the Ministry of Supply . The scientists mostly took over both accommodations 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 and Walter Marshall ), Isotopes (Henry Seligmann), Engineering (Harold Tongue, later Robert Jackson), Chemical Engineering (A.S. White), and Metallurgy (Bruce Chalmers, later Monty Finniston , FRS). Finniston

3131-527: The Electro-Metallurgical Company in Welland, Ontario . The latter had a great deal of technical information about manufacturing pure graphite that it was willing to share. Orders were placed with Welland for 5,000 long tons (5,100 t) and with Acheson for 1,000 long tons (1,000 t). In 1948, Welland rose to an urgent request for another 800 long tons (810 t) for Windscale resulting from

Windscale Piles - Misplaced Pages Continue

3232-462: The Harwell site required AERE workers to be transported by shuttle bus. By 1956, nine contractors to AERE operated a total of 47 mostly second-hand buses and coaches on 41 staff shuttle services, which operated 24 hours a day to shuttle workers as far as Oxford, Newbury, Reading and Swindon to the Harwell site. These buses were initially painted in utilitarian Ministry of Supply grey livery, however by

3333-475: The House exactly what will be the future cost. The programme of work already approved will cost something like £30 million, but the programme is being kept constantly under review, and it may well be that expenditure on a far greater scale may be necessary if we are to play our proper part. With the decision to switch to air cooling, the Gen 75 Committee authorised the construction of two air-cooled reactors, turning down

3434-568: The House of Commons on 8 October 1946, Attlee referred indirectly to the decision to build the piles: As the House knows, the Government have already set up a large research establishment, and we are arranging for the production of fissile material for that establishment, and for other purposes; and the responsibility has been placed with the Minister of Supply; and this Bill will give him the necessary powers to discharge that responsibility. I cannot tell

3535-544: The Montreal Laboratory designed the British Experimental Pile Zero (BEPO). Risley handled the engineering and construction. Hinton designated James Kendall as the engineer in charge of reactor design, both BEPO and the production reactors. His team worked closely with the scientists at Harwell, in particular J. V. Dunworth, F. W. Fenning and C. A. Rennie. For an experimental reactor like BEPO, air cooling

3636-692: The Spanish Vandellòs Nuclear Power Plant – both UNGG graphite-moderated natural uranium reactors – suffered major accidents. Particularly noteworthy is a partial core meltdown on 17 October 1969 and a heat excursion during graphite annealing on 13 March 1980 in Saint-Laurent, which were both classified as INES 4. The Vandellòs NPP was damaged on 19 October 1989, and a repair was considered uneconomical. Atomic Energy Research Establishment The Atomic Energy Research Establishment ( AERE ), also known as Harwell Laboratory ,

3737-558: The United States, but in Britain as well, where ICI had designed a gaseous diffusion production plant, and a pilot plant to produce membranes for it was under construction. Least was known about the production of plutonium in nuclear reactors , or "piles" as they were often known at the time; only Chadwick had been permitted to visit the Manhattan Project's reactors. An early decision had to be taken as to whether High Explosive Research should concentrate on uranium-235 or plutonium. While everyone would have liked to pursue every avenue, like

3838-722: The aircraft hangars being ideal to house the large atomic piles that would need to be built. Although Cambridge University had the better nuclear physics facility (the Cavendish Laboratory ), the RAF did not want to abandon any of its eastern airfields because of its potential involvement in the Cold War , therefore Harwell was chosen when the RAF made the airfield available. RAF Harwell was sixteen miles south of Oxford near Didcot and Harwell (at this time in Berkshire), and on 1 January 1946

3939-399: The basis of its historic associations, and because too many people lived nearby. That left Arisaig, and the remoteness of the site foreshadowed difficulties with communications and finding skilled labour. At this point, Risley began reconsidering the technology of an air-cooled reactor. R. G. Newell, who had been the wartime head of the engineering section at the Montreal Laboratory, proposed in

4040-419: The cooling air enter the reactor centrally so it could flow outwards instead of being pumped from one end to another. These changes allowed the cooling to be conducted with much less pumping power. Harwell engineers J. Diamond and J. Hodge conducted a series of tests which showed that with these innovations, air at atmospheric pressure would suffice for cooling a small reactor for plutonium production, although not

4141-436: The core converted the uranium into a variety of isotopes, including some plutonium, which was separated from the other materials using chemical processing. As this plutonium was intended for weapons purposes, the burnup of the fuel was kept low to reduce production of the heavier plutonium isotopes like plutonium-240 and plutonium-241 . As construction proceeded, Hinton received disturbing news from Cockcroft at Harwell that

Windscale Piles - Misplaced Pages Continue

4242-429: The core under gravity at the flick of a switch. They had more than enough neutron-absorbing capacity to shut down the reactor. Cooling was by convection through a 410-foot (120 m) tall chimney, which could create enough airflow to cool the reactor under normal operating conditions. The chimney was arranged so it pulled air through the channels in the core, cooling the fuel via fins on the cartridges. The first chimney

4343-440: The core was to start the blowers, but forcing air into it could start a fire. In the end, it was decided to start the blowers. The temperature dropped, and the pile cooled without any conflagration. In the investigations that followed the incident, it was determined that the smoke came from lubricating oil from the bearings in the blowers, which was sucked into the core and charred by the heat. The investigations also determined that

4444-439: The core. This required tolerances of 1 ⁄ 1000 inch (0.025 mm). It was important that no impurities would be picked up from dust while the graphite was being machined, so a special facility was established, with a clean environment. The workers wore special clothing. Graphite is dense and quickly wore out the cutting tools. A tungsten tool was developed for the purpose. Similar practices were followed while assembling

4545-470: The critical mass of No. 1 Pile was greater than first thought. No. 2 Pile was in better shape, owing to the use of higher quality graphite. To improve the situation, the amount of neutron-absorbing aluminium was reduced by trimming a 1 ⁄ 16 -inch (1.6 mm) strip off the fins on every fuel cartridge. A million fins were clipped on site in August and September 1950 by a team led by Tom Tuohy . Reactivity

4646-516: The deficit of technical knowledge was addressed by the Montreal Laboratory in Canada, where the ZEEP reactor went critical on 5 September 1945, and the Americans had supplied some irradiated fuel rods for experiments with plutonium separation there. The British scientists were aware that the choices they made at this point might influence British reactor design for many years to come. In designing

4747-432: The development effort, which was codenamed High Explosive Research . Penney contended that "the discriminative test for a first-class power is whether it has made an atomic bomb and we have either got to pass the test or suffer a serious loss of prestige both inside this country and internationally." Through their participation in the wartime Tube Alloys and Manhattan Project, British scientists had considerable knowledge of

4848-525: The development of pilot plants for fuel reprocessing. The site became a major employer in the Oxford area. In the 1990s demand for government-led research had significantly decreased and the site was subsequently gradually diversified to allow private investment, and was known from 2006 as the Harwell Science and Innovation Campus . In 1945 John Cockcroft was asked to set up a research laboratory to further

4949-607: The directorship of John Cockcroft . Christopher Hinton agreed to oversee the design, construction and operation of the new nuclear weapons facilities, which included a uranium metal plant at Springfields in Lancashire , and nuclear reactors and plutonium processing facilities at Windscale in Cumbria . He established his headquarters in a former Royal Ordnance Factory (ROF) at Risley in Lancashire on 4 February 1946. In July 1946,

5050-616: The feasibility of a renewed nuclear weapons programme. The Tube Alloys Directorate was transferred from the Department of Scientific and Industrial Research to the Ministry of Supply on 1 November 1945, and Lord Portal was appointed Controller of Production, Atomic Energy (CPAE), with direct access to the Prime Minister. An Atomic Energy Research Establishment (AERE) was established on 29 October 1945 at RAF Harwell , south of Oxford , under

5151-590: The first sample of British plutonium on 28 March 1952. Enough Windscale plutonium for an atomic bomb was delivered to the weapons division at Aldermaston in August, and Britain's first nuclear device was successfully detonated in the Operation Hurricane test in the Monte Bello Islands in Western Australia on 3 October 1952. Wigner energy , if allowed to accumulate, could escape spontaneously in

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5252-409: The former ROF Drigg site on the coast of Cumberland was selected. One complication was that Courtaulds planned to use the old plant at nearby ROF Sellafield to produce rayon . Considering that the labour market in the area could not sustain two large projects, Courtaulds withdrew, and relinquished the 300-acre (120 ha) site. It was considered a more suitable location for a reactor. The use

5353-427: The graphite to crack before then. Harwell physicist William Marley, who had worked at the Manhattan Project's Los Alamos Laboratory during the war, had warned of the possibility of a fire in a control rod being exacerbated by the release of Wigner energy, and when Edward Teller visited Harwell in 1948, he warned that a Wigner energy release might ignite a fuel rod. The British scientists, however, remained certain that

5454-472: The immediate post-war period in Britain. Two estates of 'Prefabs' were built to the north and south of the site perimeter, along with a road system and parade of shops. In later years, conventional housing was provided on estates built in Abingdon , Grove (near Wantage ) and Newbury for employees. A modern hostel (Rush Common House) was built in Abingdon. The houses were later sold (mainly to their occupants) in

5555-400: The main employers in the post-war period. It also led to an influx of labour from outside the area, putting pressure on already scarce housing stocks. In response to the problem, hostels and temporary housing were established around the site. The hostels were named Icknield Way House ('B' mess, the RAF sergeants' mess), Portway House ('C' Mess, the RAF airmans' mess) and Ridgeway House ('A' Mess,

5656-608: The mid-1950s, the AERE fleet began adopting an azure blue and grey livery with 'AERE' signwriting. 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-power (3   kilowatt ) graphite-moderated air-cooled reactor. The first reactor in Western Europe, it operated until 1990. A successor to GLEEP, called BEPO (British Experimental Pile 0)

5757-455: The nearby establishments to heat offices. This was the first use of nuclear district heating in the UK. BEPO was shut down in 1968. LIDO was an enriched uranium thermal swimming pool reactor which operated from 1956 to 1972 and was mainly used for shielding and nuclear physics experiments. It was fully dismantled and returned to a green field site in 1995. In the same building as LIDO, DAPHNE (Dido And Pluto Handmaiden for Nuclear Experiments)

5858-433: The neutron moderator had to be as pure as possible, as even the smallest impurities could act as neutron poisons that would impede the reactor's operation. Normal industrial graphite would not do. The British had been excluded from the work the Manhattan Project had done in this field, but Union Carbide , the Americans' principal supplier of graphite, had subsidiaries in Britain and Canada, British Acheson at Sheffield , and

5959-545: The officers' mess) provided either single or double room accommodation for staff and were adopted from existing RAF structures on the site. The class distinction was maintained by the UKAEA. A-Mess housed visiting scientists, B-Mess scientific support staff and some post-graduate scientists, and C-Mess industrial support staff. The temporary housing stock consisted of several hundred ' Prefabs ', single storey structures manufactured in parts for quick erection, which were designed originally to help alleviate chronic housing shortages in

6060-418: The operators. Wigner releases were not experiments—they were crucial to the continued operation of the reactors—but they were far from routine either; each was different, and over time releases of Wigner energy became harder to achieve, requiring higher temperatures. The assistant manager, J. L. Phillips, asked Risley if sufficient thermocouples could be supplied to give a complete picture of the temperatures in

6161-643: The other side, where they fell into a skip . From there they were taken to a service pond where they were held until the most radioactive fission products decayed. From there they were sent to the separation plant for decanning and processing. The power level in the core was regulated by 24 control rods made from boron steel . Boron is a powerful neutron absorber; the steel was for strength. Twenty of these were coarse control rods and four for fine tuning. They could be moved individually or in groups. In case of emergency, there were also sixteen vertical fail safe rods held above by electromagnets that could drop down into

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6262-460: The production of fissile materials. The Americans had created two kinds: uranium-235 and plutonium , and had pursued three different methods of uranium enrichment to produce the former. British scientists had been most heavily involved with the electromagnetic isotope separation process, but it was recognised that it might be uneconomical in peacetime. They also knew a great deal about the gaseous diffusion process through work done not just in

6363-434: The reactor, readable in the reactor control room, for monitoring both the graphite and the fuel elements. The best that could be done was to supply 66 thermocouples for graphite measurement during Wigner releases, and 20 for the uranium fuel elements. On 1 March 1955, the prime minister, Winston Churchill , publicly committed the UK to building a hydrogen bomb , and gave the scientists a tight schedule in which to do so. This

6464-508: The reactor, with the workers wearing special clothes, and the air inside the biological shield filtered to remove dust. The British had little experience with the behaviour of graphite when exposed to neutrons. The Hungarian-American physicist Eugene Wigner had discovered while working at the Manhattan Project's Metallurgical Laboratory in Chicago that graphite, when bombarded by neutrons, suffers dislocations in its crystalline structure, causing

6565-418: The risk was slight compared to that of a water-cooled reactor. The core of the reactors consisted of a large block of graphite with horizontal channels drilled through it for the fuel cartridges. Each cartridge consisted of a uranium rod about 30 centimetres (12 in) long encased in an aluminium canister to protect it from the air, as uranium becomes highly reactive when hot and can catch fire. The cartridge

6666-489: The rupture of the reactor vessel and a series of steam explosions, which destroyed the reactor building. Now exposed to both air and the heat from the reactor core, the graphite moderator in the reactor core caught fire, and this fire sent a plume of highly radioactive fallout into the atmosphere and over an extensive geographical area. In addition, the French Saint-Laurent Nuclear Power Plant and

6767-449: The site employed a construction workforce of over 5,000 men, along with 300 professional staff such as architects, engineers and surveyors. It was difficult to find sufficient labour locally, so workers were lured to the site from other areas with the promise of high wages and overtime . Hutted camps were established for them with canteens and other amenities. Engineers were no less hesitant about moving to Windscale. The post of site engineer

6868-498: The speed of the blowers, the control rod positions, and there were various alarms. Static air sampling devices in the air ducts measured radioactive emissions. These could quickly detect, but not locate, a burst cartridge. Burst Cartridge Detector Gear (BCDG) was located at the rear face of each reactor. Each had 32 nozzles that could sample the air from 32 channels at a time. A sweep of all the channels took about 57 minutes. A burst cartridge could thereby be located. Considerable thought

6969-401: The sudden bursts of heat must have been caused by the spontaneous release of Wigner energy. This worried the operators, but decommissioning the reactors would mean there was no plutonium for the nuclear weapons programme, delaying it by up to four years. They turned to the only viable solution, heating the reactor core on a regular basis at shutdown in a process known as annealing . When graphite

7070-415: The telephone any morning to hear the news that one of the piles had gone up." To minimise this risk, the Americans had established strict siting criteria. The reactors were to be located 50 miles (80 km) from any town with a population of over 50,000, 25 miles (40 km) from one of over 10,000, and 5 miles (8.0 km) from one of over 1,000, and were to be built 5   miles apart. Groves also had

7171-426: The top. D. Dick, the structural engineer at the Ministry of Works, produced a design. Construction involved the materials to build them, which included 200 long tons (200 t) of structural steel, plus bricks, concrete and equipment, being hoisted to the top of the 400-foot (120 m) chimneys. They gave the chimneys a distinctive appearance, and were mocked as " Cockcroft's Follies " by the workers and engineers. It

7272-461: The tubes holding the uranium fuel rods. Because water absorbed neutrons, a loss of cooling water would not only mean a rise in temperature, but would also trigger an increase in the number of neutrons in the reactor, creating more fissions and increasing the temperature further, possibly resulting in a nuclear meltdown and the release of radioactive fission products . Groves confided to the British in 1946 that he "would not be surprised to be called to

7373-402: The use of nuclear fission for both military purposes and generating energy. The criteria for selection 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 the areas around Oxford or Cambridge . It had been decided that an RAF airfield would be chosen,

7474-569: The vicinity. He was alarmed enough to order that air filters be installed, as they had been in the Graphite Research Reactor at the Brookhaven National Laboratory . While management at Risley took this calmly, the engineers were unimpressed. The logical place to put air filters was at the bottom of a chimney, but the first 70 feet (21 m) of the chimney of No. 1 Pile had already been built. They therefore had to go on

7575-406: Was also improved by reducing the size of the channels through which the cooling air was forced. New graphite soles were fabricated for the graphite shoes that held the fuel cartridges. The graphite block was pierced by 3,440 fuel channels, arranged in groups of four. Each was loaded with a string of 21 finned aluminium cartridges containing uranium. The cartridges were discharged by pushing them out

7676-412: Was believed that no further progress could be made with the kind of design that ZETA represented (see Timeline of nuclear fusion ). In 1954 AERE was incorporated into the newly formed United Kingdom Atomic Energy Authority (UKAEA). Harwell and other laboratories were to assume responsibility for atomic energy research and development. It was part of the Department of Trade and Industry (DTI). During

7777-407: Was built in the winter of 1950–51. Additional cooling was provided by eight larger blowers, arranged with four in each of two blower houses outside the biological shield. There were also two auxiliary booster fans, and four shutdown fans that were used when the reactor was not running to remove residual heat. Instrumentation included devices for measuring the temperature and neutron flux in the core,

7878-476: Was consistent with planning proposals for the Lake District National Park ; water was available from Wast Water without engineering works; and the site already had a railway siding and some office and service buildings, which saved construction time and effort. To avoid confusion with the nuclear fuel production site at Springfields , the name was changed to Windscale, which was actually the name of

7979-435: Was constructed based on the experience with GLEEP, and commenced operation in 1948. At 6   MW , BEPO was much more powerful than GLEEP. The engineers at Harwell eventually decided that this small reactor should be put to some use, so the air that flowed over it was directed through an underground trench, where there were some pipes filled with water that connected to a secondary group of water-filled pipes that were used by

8080-468: Was constructed to test equipment used in experiments on the two larger reactors. 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 reactors were used primarily for testing the behaviour of different materials under intense neutron irradiation to help decide what materials to build reactor components out of. A sample could be irradiated for

8181-471: Was decided that each reactor would sit atop a reinforced concrete slab 200 feet (61 m) wide, 100 feet (30 m) long and 10 feet (3.0 m) thick. To avoid any chance of it shrinking, the ratio of water to cement was carefully controlled, and the order in which the concrete was poured was done so as to maximise drying time. The structure above had to be sited with a tolerance of 1 ⁄ 2 inch (13 mm) in 100 feet (30 m). The graphite for

8282-491: 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 remainder was privatised as AEA Technology and floated on the London Stock Exchange . Harwell Laboratory contained elements of both organisations, though the land and infrastructure was owned by UKAEA. The name Atomic Energy Research Establishment

8383-654: Was dropped at the same time, and the site became known as the Harwell International Business Centre . The site incorporates the Rutherford Appleton Laboratory which is home to the Science and Technology Facilities Council (including the ISIS neutron source and Diamond Light Source ). In 2006, the name Harwell Science and Innovation Campus was introduced and management of the campus was passed to

8484-489: Was encased in a biological shield of concrete 7-foot (2.1 m) thick, which was lined with steel plates that provided a thermal shield. Given the certainty of the Wigner energy buildup, Hinton estimated that the lifetime of the reactors would be about five years—ten at the most. The scientists were more optimistic, predicting a lifetime of fifteen to thirty-five years, but conceded that Wigner energy-induced expansion might cause

8585-462: Was finned, allowing heat exchange with the environment to cool the fuel rods while they were in the reactor. Rods were pushed in the front of the core, the "charge face", with new rods being added at a calculated rate. This pushed the other cartridges in the channel towards the rear of the reactor, eventually causing them to fall out the back, the "discharge face", into a water filled channel where they cooled and could be collected. The chain reaction in

8686-484: Was given as to what would happen if one of the fuel cartridges were to break open. This would release highly radioactive fission produces, and oxidation of the uranium might cause a fire. With 70,000 cartridges, a failed one seemed inevitable. On a visit to the X-10 Graphite Reactor at the Oak Ridge National Laboratory in the United States, Cockcroft found that uranium oxide particles had been detected in

8787-412: Was given to W. Davies from Harwell, with T. G. Williams and A. Young as his assistants. The reactors and their surrounding structures each weighed 57,000 long tons (58,000 t), and it was extremely important that they not shift owing to ground movement. To determine the load bearing properties of the underlying soil and rock, holes were drilled at various points. On the basis of the results of this, it

8888-561: Was later discovered that the uranium oxide at Oak Ridge had come from the chemical separation plant there, and not the reactor. Pile No. 1 went critical in October 1950, but its performance was about 30 per cent below its designed rating. Pile No. 2 went critical in June 1951, and was soon operating at 90 per cent of its designed power. The piles had been designed to produce 90 kg of plutonium annually. The first irradiated fuel rods were sent for processing in January 1952, and Tom Tuohy retrieved

8989-490: Was later to become chairman of the British Steel Corporation. Directors after Cockcroft included Basil Schonland , Sir Arthur Vick and Walter Marshall . The decision to site AERE at Harwell had huge implications for a rural area which had depended mainly on agriculture for employment before World War II. The site (which quickly became known colloquially amongst the local population as 'The Atomic') became one of

9090-419: Was not available in the UK. The choice therefore narrowed to graphite. The first nuclear reactor in the UK, a small 100 kW research reactor known as GLEEP , went critical at Harwell on 15 August 1947. This was fine for some experimental work, but the production of radioactive isotopes required a more powerful 6,000 kW reactor with a higher neutron flux . For this, British scientists and engineers at

9191-505: Was perpendicular and not parallel to the axes of extrusion. When the engineers at Risley recalculated the expansion of the graphite using the data provided by Zinn, they discovered that their reactor design would not work. This was disappointing, as it was already under construction, and the graphite blocks were already being machined. A redesign was called for, and they came up with an ingenious solution. The graphite blocks were laid on end so there would be no vertical expansion, and each block

9292-419: Was provided with clearance so it could expand horizontally. The blocks were secured in the horizontal plane by lattices of graphite slats cut from the blocks along the axis of extrusion. In March 1949 Harwell reported that British graphite behaved slightly differently to American graphite, and did expand slightly along the horizontal axis. This had the potential to reduce the lifetime of the reactor to just two and

9393-469: Was set up at Harwell, and developed shipping fleet scheduling software that was used to provide a service to British and overseas shipping companies and oil reservoir simulation software to help in the development of the UK's North Sea oil interests. 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. After several years of transition, UKAEA

9494-502: Was situated in were decommissioned 2005. The current plans are to decommission the BEPO, 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 1968 the project was shut down, as it

9595-407: Was subsequently increased to every 30,000   MWhr, and then every 40,000   MWhr. Between August 1953 and July 1957, eight annealings were carried out on Pile No. 1, and seven on Pile No. 2. The maximum graphite temperatures recorded were between 310 °C (590 °F) and 420 °C (788 °F). Scientists from Harwell were on hand for the first two or three, but afterwards it was left to

9696-559: Was that they would differ from BEPO in that they would be water cooled. It was known that this was the approach that the Americans had taken at the Hanford Site , although only Portal was allowed to visit it, and not being a scientist, had not brought back much useful information. It was estimated that a water-cooled reactor the size of the B Reactor at Hanford required about 30 million imperial gallons (140 megalitres) of water per day, and it had to be exceptionally pure lest it corrode

9797-776: Was the main centre for atomic energy research and development in the United Kingdom from 1946 to the 1990s. It was created, owned and funded by the British Government. A number of early research reactors were built here starting with GLEEP in 1947 to provide the underlying science and technology behind the design and building of Britain's nuclear reactors such as the Windscale Piles and Calder Hall nuclear power station. To support this an extensive array of research and design laboratories were built to enable research into all aspects of nuclear reactor and fuel design, and

9898-453: Was the obvious choice. The resulting reactor was thus quite similar to the Manhattan Project's X-10 Graphite Reactor in both design and purpose. BEPO went critical on 5 July 1948. Much was learned from the design and construction of BEPO, which ran continuously until it was decommissioned in December 1968. When it came to the design of the much larger production reactors, the initial assumption

9999-600: Was then hastened after the US and USSR began working on a test ban and possible disarmament agreements which would begin to take effect in 1958. To meet this deadline there was no chance of building a new reactor to produce the required tritium (codenamed AM), so the Windscale Piles produced tritium through irradiation of lithium - magnesium , the latter of which would produce tritium during neutron bombardment. Graphite-moderated reactor The first artificial nuclear reactor,

10100-497: Was then raised to 4   MW to heat the graphite. Two of the thermocouples indicated a sudden rise in temperate at 03:00 on 10 January, and the reactor was shut down. By 17:00 it was reckoned that the accumulated Wigner energy had been released, and the shutdown fans, and then the main blowers, were switched on to cool the core in preparation for restarting. From then on, there were periodic anneals to release Wigner energy. Initially, they were carried out every 20,000   MWhr. This

10201-421: Was used, and that contributed to the accident – however it was the uranium fuel rather than the graphite in the reactor that caught fire. The only graphite moderator damage was found to be localized around burning fuel elements. In the Chernobyl disaster, the graphite was a contributing factor to the cause of the accident. Due to overheating from lack of adequate cooling, the fuel rods began to deteriorate. After

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