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188-625: The X-10 Graphite Reactor is a decommissioned nuclear reactor at Oak Ridge National Laboratory in Oak Ridge, Tennessee . Formerly known as the Clinton Pile and X-10 Pile , it was the world's second artificial nuclear reactor (after Enrico Fermi 's Chicago Pile-1 ) and the first designed and built for continuous operation. It was built during World War II as part of the Manhattan Project . While Chicago Pile-1 demonstrated

376-734: A privatdocent at the University of Copenhagen, giving lectures on thermodynamics . Martin Knudsen put Bohr's name forward for a docent , which was approved in July 1913, and Bohr then began teaching medical students. His three papers, which later became famous as "the trilogy", were published in Philosophical Magazine in July, September and November of that year. He adapted Rutherford's nuclear structure to Max Planck 's quantum theory and so created his Bohr model of

564-669: A War Department policy held that, as a rule, munitions facilities should not be located west of the Sierra or Cascade Ranges , east of the Appalachian Mountains , or within 200 miles (320 km) of the Canadian or Mexican borders. In December, it was decided that the plutonium production facilities would not be built at Oak Ridge after all, but at the even more remote Hanford Site in Washington state . Compton and

752-479: A nuclear proliferation risk as they can be configured to produce plutonium , as well as tritium gas used in boosted fission weapons . Reactor spent fuel can be reprocessed to yield up to 25% more nuclear fuel, which can be used in reactors again. Reprocessing can also significantly reduce the volume of nuclear waste, and has been practiced in Europe, Russia, India and Japan. Due to concerns of proliferation risks,

940-703: A semiworks where techniques and procedures could be developed and training conducted. The centerpiece of this was the X-10 Graphite Reactor. It was air-cooled, used nuclear graphite as a neutron moderator , and pure natural uranium in metal form for fuel. DuPont commenced construction of the plutonium semiworks at the Clinton Engineer Works in Oak Ridge on February 2, 1943. The reactor went critical on November 4, 1943, and produced its first plutonium in early 1944. It supplied

1128-455: A subjectivist or a positivist , most philosophers agree that this is a misunderstanding of Bohr as he never argued for verificationism or for the idea that the subject had a direct impact on the outcome of a measurement. Bohr has often been quoted saying that there is "no quantum world" but only an "abstract quantum physical description". This was not publicly said by Bohr, but rather a private statement attributed to Bohr by Aage Petersen in

1316-558: A " neutron howitzer ") produced a barium residue, which they reasoned was created by fission of the uranium nuclei. In their second publication on nuclear fission in February 1939, Hahn and Strassmann predicted the existence and liberation of additional neutrons during the fission process, opening the possibility of a nuclear chain reaction . Subsequent studies in early 1939 (one of them by Szilárd and Fermi), revealed that several neutrons were indeed released during fission, making available

1504-419: A 700-short-ton (640 t), 25-foot (7.6 m) cube of graphite fueled by natural uranium. Its primary mission was applied nuclear research in medicine, biology, chemistry, physics and nuclear engineering. One of the most significant discoveries at this facility was the development of production of molybdenum-99 /technetium-99m, used today in tens of millions of medical diagnostic procedures annually, making it

1692-486: A big step, given that many industrial processes do not easily scale from the laboratory to production size. An intermediate step of building a pilot plant was considered prudent. For the pilot plutonium separation plant, a site was wanted close to the Metallurgical Laboratory, where the research was being carried out, but for reasons of safety and security, it was not desirable to locate the facilities in

1880-424: A certain kinematic or dynamic value to an atomic object are dependent on the apparatus involved, in such a way that these truth conditions have to include reference to the experimental setup as well as the actual outcome of the experiment. Faye notes that Bohr's interpretation makes no reference to a "collapse of the wave function during measurements" (and indeed, he never mentioned this idea). Instead, Bohr "accepted

2068-488: A chemical separation plant, a waste storage area, a training facility for Hanford staff, and administrative and support facilities that included a laundry, cafeteria, first aid center, and fire station. Because of the subsequent decision to construct water-cooled reactors at Hanford, only the chemical separation plant operated as a true pilot. The semiworks eventually became known as the Clinton Laboratories and

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2256-500: A chute into a 20-foot-deep (6.1 m) pool of water that acted as a radiation shield. Following weeks of underwater storage to allow for decay in radioactivity , the slugs were delivered to the chemical separation building. By February 1944, the reactor was irradiating a ton of uranium every three days. Over the next five months, the efficiency of the separation process was improved, with the percentage of plutonium recovered increasing from 40 to 90 percent. Modifications over time raised

2444-399: A comprehensive survey of what was then known about the structure of the atom, including the correspondence principle , which he had formulated. This states that the behaviour of systems described by quantum theory reproduces classical physics in the limit of large quantum numbers . The discovery of Compton scattering by Arthur Holly Compton in 1923 convinced most physicists that light

2632-441: A crucial role in generating large amounts of electricity with low carbon emissions, contributing significantly to the global energy mix. Just as conventional thermal power stations generate electricity by harnessing the thermal energy released from burning fossil fuels , nuclear reactors convert the energy released by controlled nuclear fission into thermal energy for further conversion to mechanical or electrical forms. When

2820-608: A densely populated area like Chicago . Compton selected a site in the Argonne Forest , part of the Forest Preserve District of Cook County , about 20 miles (32 km) southwest of Chicago. The full-scale production facilities would be co-located with other Manhattan Project facilities at a still more remote location in Tennessee. Some 1,000 acres (400 ha) of land was leased from Cook County for

3008-473: A distinction between observed phenomena and a transcendental reality . Jan Faye disagrees with this position and holds that for Bohr, the quantum formalism and complementarity was the only thing we could say about the quantum world and that "there is no further evidence in Bohr's writings indicating that Bohr would attribute intrinsic and measurement-independent state properties to atomic objects [...] in addition to

3196-434: A far higher spontaneous fission rate than plutonium-239. This meant that it would be highly likely that a plutonium gun-type nuclear weapon would predetonate and blow itself apart during the initial formation of a critical mass. The Los Alamos Laboratory was thus forced to turn its development efforts to creating an implosion-type nuclear weapon —a far more difficult feat. The X-10 chemical separation plant also verified

3384-605: A focal point for researchers into quantum mechanics and related subjects in the 1920s and 1930s, when most of the world's best-known theoretical physicists spent some time in his company. Early arrivals included Hans Kramers from the Netherlands, Oskar Klein from Sweden, George de Hevesy from Hungary, Wojciech Rubinowicz from Poland, and Svein Rosseland from Norway. Bohr became widely appreciated as their congenial host and eminent colleague. Klein and Rosseland produced

3572-445: A gas or a liquid metal (like liquid sodium or lead) or molten salt – is circulated past the reactor core to absorb the heat that it generates. The heat is carried away from the reactor and is then used to generate steam. Most reactor systems employ a cooling system that is physically separated from the water that will be boiled to produce pressurized steam for the turbines , like the pressurized water reactor . However, in some reactors

3760-415: A huge block, 24 feet (7.3 m) long on each side, of nuclear graphite cubes, weighing around 1,500 short tons (1,400 t), that acted as a moderator. They were surrounded by seven feet (2.1 m) of high-density concrete as a radiation shield. In all, the reactor was 38 feet (12 m) wide, 47 feet (14 m) deep and 32 feet (9.8 m) high. There were 36 horizontal rows of 35 holes. Behind each

3948-442: A large fissile atomic nucleus such as uranium-235 , uranium-233 , or plutonium-239 absorbs a neutron, it may undergo nuclear fission. The heavy nucleus splits into two or more lighter nuclei, (the fission products ), releasing kinetic energy , gamma radiation , and free neutrons . A portion of these neutrons may be absorbed by other fissile atoms and trigger further fission events, which release more neutrons, and so on. This

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4136-868: A leave of absence from the University of Copenhagen, which he started by taking a holiday in Tyrol with his brother Harald and aunt Hanna Adler . There, he visited the University of Göttingen and the Ludwig Maximilian University of Munich , where he met Sommerfeld and conducted seminars on the trilogy. The First World War broke out while they were in Tyrol, greatly complicating the trip back to Denmark and Bohr's subsequent voyage with Margrethe to England, where he arrived in October 1914. They stayed until July 1916, by which time he had been appointed to

4324-424: A less effective moderator. In other reactors, the coolant acts as a poison by absorbing neutrons in the same way that the control rods do. In these reactors, power output can be increased by heating the coolant, which makes it a less dense poison. Nuclear reactors generally have automatic and manual systems to scram the reactor in an emergency shut down. These systems insert large amounts of poison (often boron in

4512-460: A nuclear weapon was possible with great efforts, and this raised enormous responsibilities on the world's scientists on both sides. When Bohr saw Jungk's depiction in the Danish translation of the book, he drafted (but never sent) a letter to Heisenberg, stating that he deeply disagreed with Heisenberg's account of the meeting, that he recalled Heisenberg's visit as being to encourage cooperation with

4700-570: A number of ways: A kilogram of uranium-235 (U-235) converted via nuclear processes releases approximately three million times more energy than a kilogram of coal burned conventionally (7.2 × 10 joules per kilogram of uranium-235 versus 2.4 × 10 joules per kilogram of coal). The fission of one kilogram of uranium-235 releases about 19 billion kilocalories , so the energy released by 1 kg of uranium-235 corresponds to that released by burning 2.7 million kg of coal. A nuclear reactor coolant – usually water but sometimes

4888-627: A paper presented at the Volta Conference at Como in September 1927, Bohr emphasised that Heisenberg's uncertainty relations could be derived from classical considerations about the resolving power of optical instruments. Understanding the true meaning of complementarity would, Bohr believed, require "closer investigation". Einstein preferred the determinism of classical physics over the probabilistic new quantum physics to which he himself had contributed. Philosophical issues that arose from

5076-465: A patent on reactors on 19 December 1944. Its issuance was delayed for 10 years because of wartime secrecy. "World's first nuclear power plant" is the claim made by signs at the site of the EBR-I , which is now a museum near Arco, Idaho . Originally called "Chicago Pile-4", it was carried out under the direction of Walter Zinn for Argonne National Laboratory . This experimental LMFBR operated by

5264-648: A pile (hence the name) of graphite blocks, embedded in which was natural uranium oxide 'pseudospheres' or 'briquettes'. Soon after the Chicago Pile, the Metallurgical Laboratory developed a number of nuclear reactors for the Manhattan Project starting in 1943. The primary purpose for the largest reactors (located at the Hanford Site in Washington ), was the mass production of plutonium for nuclear weapons. Fermi and Szilard applied for

5452-407: A planned typical lifetime of 30–40 years, though many of those have received renovations and life extensions of 15–20 years. Some believe nuclear power plants can operate for as long as 80 years or longer with proper maintenance and management. While most components of a nuclear power plant, such as steam generators, are replaced when they reach the end of their useful lifetime, the overall lifetime of

5640-481: A preliminary report on water cooling, designated CE-140 in April 1942, followed by a more detailed one, CE-197, titled "On a Plant with Water Cooling", in July 1942. Fermi's Chicago Pile-1 reactor, constructed under the west viewing stands of the original Stagg Field at the University of Chicago, "went critical" on December 2, 1942. This graphite-moderated reactor only generated up to 200 W, but it demonstrated that k

5828-589: A rare-earth element 72, which he called "celtium". At the Institute in Copenhagen, Dirk Coster and George de Hevesy took up the challenge of proving Bohr right and Urbain wrong. Starting with a clear idea of the chemical properties of the unknown element greatly simplified the search process. They went through samples from Copenhagen's Museum of Mineralogy looking for a zirconium-like element and soon found it. The element, which they named hafnium ( hafnia being

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6016-471: A reactor. One such process is delayed neutron emission by a number of neutron-rich fission isotopes. These delayed neutrons account for about 0.65% of the total neutrons produced in fission, with the remainder (termed " prompt neutrons ") released immediately upon fission. The fission products which produce delayed neutrons have half-lives for their decay by neutron emission that range from milliseconds to as long as several minutes, and so considerable time

6204-411: A reminiscence after his death. N. David Mermin recalled Victor Weisskopf declaring that Bohr wouldn't have said anything of the sort and exclaiming, "Shame on Aage Petersen for putting those ridiculous words in Bohr's mouth!" Numerous scholars have argued that the philosophy of Immanuel Kant had a strong influence on Bohr. Like Kant, Bohr thought distinguishing between the subject's experience and

6392-529: A set of theoretical nuclear reactor designs. These are generally not expected to be available for commercial use before 2040–2050, although the World Nuclear Association suggested that some might enter commercial operation before 2030. Current reactors in operation around the world are generally considered second- or third-generation systems, with the first-generation systems having been retired some time ago. Research into these reactor types

6580-434: A site that was so accessible, as they were afraid that it would permit the research staff from the Metallurgical Laboratory to interfere unduly with the design and construction, which they considered their prerogative. A better location, they felt, would be with the remote production facilities at Hanford. In the end a compromise was reached. On January 12, 1943, Compton, Williams, and Brigadier General Leslie R. Groves, Jr. ,

6768-619: A small container of carbon-14 to the director of the Barnard Free Skin and Cancer Hospital, for medical use at the hospital in St. Louis, Missouri . Subsequent shipments of radioisotopes, primarily iodine-131 , phosphorus-32 , carbon-14, and molybdenum-99/ technetium-99m , were for scientific, medical, industrial and agricultural uses. In August 1948, the reactor was used to produce the first electricity derived from nuclear power. Uranium slugs within an aluminum tube were irradiated within

6956-652: A teacher, while Harald became a mathematician and footballer who played for the Danish national team at the 1908 Summer Olympics in London. Niels was a passionate footballer as well, and the two brothers played several matches for the Copenhagen-based Akademisk Boldklub (Academic Football Club), with Niels as goalkeeper . Bohr was educated at Gammelholm Latin School, starting when he

7144-714: A visit to the United States. Bohr offered the refugees temporary jobs at the institute, provided them with financial support, arranged for them to be awarded fellowships from the Rockefeller Foundation, and ultimately found them places at institutions around the world. Those that he helped included Guido Beck , Felix Bloch , James Franck , George de Hevesy, Otto Frisch , Hilde Levi , Lise Meitner , George Placzek, Eugene Rabinowitch , Stefan Rozental , Erich Ernst Schneider, Edward Teller , Arthur von Hippel and Victor Weisskopf . In April 1940, early in

7332-413: Is inserted deeper into the reactor, it absorbs more neutrons than the material it displaces – often the moderator. This action results in fewer neutrons available to cause fission and reduces the reactor's power output. Conversely, extracting the control rod will result in an increase in the rate of fission events and an increase in power. The physics of radioactive decay also affects neutron populations in

7520-574: Is its charge, h is the Planck constant and Z is the atom's atomic number (1 for hydrogen). The model's first hurdle was the Pickering series , lines that did not fit Balmer's formula. When challenged on this by Alfred Fowler , Bohr replied that they were caused by ionised helium , helium atoms with only one electron. The Bohr model was found to work for such ions. Many older physicists, like Thomson, Rayleigh and Hendrik Lorentz , did not like

7708-428: Is known as a nuclear chain reaction . To control such a nuclear chain reaction, control rods containing neutron poisons and neutron moderators are able to change the portion of neutrons that will go on to cause more fission. Nuclear reactors generally have automatic and manual systems to shut the fission reaction down if monitoring or instrumentation detects unsafe conditions. The reactor core generates heat in

X-10 Graphite Reactor - Misplaced Pages Continue

7896-405: Is mined, processed, enriched, used, possibly reprocessed and disposed of is known as the nuclear fuel cycle . Under 1% of the uranium found in nature is the easily fissionable U-235 isotope and as a result most reactor designs require enriched fuel. Enrichment involves increasing the percentage of U-235 and is usually done by means of gaseous diffusion or gas centrifuge . The enriched result

8084-649: Is one of the most delightful things I have ever read." Bohr enjoyed Kierkegaard's language and literary style, but mentioned that he had some disagreement with Kierkegaard's philosophy . Some of Bohr's biographers suggested that this disagreement stemmed from Kierkegaard's advocacy of Christianity, while Bohr was an atheist . There has been some dispute over the extent to which Kierkegaard influenced Bohr's philosophy and science. David Favrholdt argued that Kierkegaard had minimal influence over Bohr's work, taking Bohr's statement about disagreeing with Kierkegaard at face value, while Jan Faye argued that one can disagree with

8272-401: Is produced. Fission also produces iodine-135 , which in turn decays (with a half-life of 6.57 hours) to new xenon-135. When the reactor is shut down, iodine-135 continues to decay to xenon-135, making restarting the reactor more difficult for a day or two, as the xenon-135 decays into cesium-135, which is not nearly as poisonous as xenon-135, with a half-life of 9.2 hours. This temporary state is

8460-448: Is reaching or crossing their design lifetimes of 30 or 40 years. In 2014, Greenpeace warned that the lifetime extension of ageing nuclear power plants amounts to entering a new era of risk. It estimated the current European nuclear liability coverage in average to be too low by a factor of between 100 and 1,000 to cover the likely costs, while at the same time, the likelihood of a serious accident happening in Europe continues to increase as

8648-416: Is required to determine exactly when a reactor reaches the critical point. Keeping the reactor in the zone of chain reactivity where delayed neutrons are necessary to achieve a critical mass state allows mechanical devices or human operators to control a chain reaction in "real time"; otherwise the time between achievement of criticality and nuclear meltdown as a result of an exponential power surge from

8836-453: Is still the best known model of the atom, as it often appears in high school physics and chemistry texts. Bohr did not enjoy teaching medical students. He later admitted that he was not a good lecturer, because he needed a balance between clarity and truth, between "Klarheit und Wahrheit". He decided to return to Manchester, where Rutherford had offered him a job as a reader in place of Darwin, whose tenure had expired. Bohr accepted. He took

9024-507: Is then converted into uranium dioxide powder, which is pressed and fired into pellet form. These pellets are stacked into tubes which are then sealed and called fuel rods . Many of these fuel rods are used in each nuclear reactor. Niels Bohr Niels Henrik David Bohr ( Danish: [ˈne̝ls ˈpoɐ̯ˀ] ; 7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory , for which he received

9212-460: Is used for scientific purposes, such as neutron activation analysis , neutron physics experiments, calibration of nuclear measurement devices and the production of neutron transmutation doped silicon . [REDACTED]  This article incorporates public domain material from X-10 Graphite Reactor . United States Department of Energy . Retrieved December 13, 2015 . Nuclear reactor Nuclear reactors have their origins in

9400-568: The Philosophical Transactions of the Royal Society . Harald became the first of the two Bohr brothers to earn a master's degree , which he earned for mathematics in April 1909. Niels took another nine months to earn his on the electron theory of metals, a topic assigned by his supervisor, Christiansen. Bohr subsequently elaborated his master's thesis into his much-larger Doctor of Philosophy thesis. He surveyed

9588-675: The American Chemical Society . The control room and reactor face are accessible to the public during scheduled tours offered through the American Museum of Science and Energy . The Brookhaven National Laboratory (BNL) Graphite Research Reactor was the first nuclear reactor to be constructed in the United States following World War II. Led by Lyle Benjamin Borst , the reactor construction began in 1947 and reached criticality on August 22, 1950. The reactor consisted of

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9776-508: The Clinton Engineer Works in Tennessee. The Oak Ridge site was selected on the basis of several criteria. The plutonium pilot facilities needed to be two to four miles (3.2 to 6.4 km) from the site boundary and any other installation, in case radioactive fission products escaped. While security and safety concerns suggested a remote site, it still needed to be near sources of labor, and accessible by road and rail transportation. A mild climate that allowed construction to proceed throughout

9964-694: The Finnish Relief Fund , and was auctioned off in March 1940, along with the medal of August Krogh . The buyer later donated the two medals to the Danish Historical Museum in Frederiksborg Castle , where they are still kept, although Bohr's medal temporarily went to space with Andreas Mogensen on ISS Expedition 70 in 2023-2024. Bohr kept the Institute running, but all the foreign scholars departed. Bohr

10152-496: The Los Alamos Laboratory with its first significant amounts of plutonium and its first reactor-bred product. Studies of these samples heavily influenced bomb design. The reactor and chemical separation plant provided invaluable experience for engineers, technicians, reactor operators, and safety officials who then moved on to the Hanford Site . X-10 operated as a plutonium production plant until January 1945, when it

10340-432: The Manhattan Project . Eventually, the first artificial nuclear reactor, Chicago Pile-1 , was constructed at the University of Chicago , by a team led by Italian physicist Enrico Fermi, in late 1942. By this time, the program had been pressured for a year by U.S. entry into the war. The Chicago Pile achieved criticality on 2 December 1942 at 3:25 PM. The reactor support structure was made of wood, which supported

10528-635: The Nobel Prize in Physics in 1922. Bohr was also a philosopher and a promoter of scientific research. Bohr developed the Bohr model of the atom , in which he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level (or orbit) to another. Although the Bohr model has been supplanted by other models, its underlying principles remain valid. He conceived

10716-517: The PWR , BWR and PHWR designs above, and some are more radical departures. The former include the advanced boiling water reactor (ABWR), two of which are now operating with others under construction, and the planned passively safe Economic Simplified Boiling Water Reactor (ESBWR) and AP1000 units (see Nuclear Power 2010 Program ). Rolls-Royce aims to sell nuclear reactors for the production of synfuel for aircraft. Generation IV reactors are

10904-551: The Pauli exclusion principle , which put Bohr's models on a firm theoretical footing. Bohr was then able to declare that the as-yet-undiscovered element 72 was not a rare-earth element but an element with chemical properties similar to those of zirconium . (Elements had been predicted and discovered since 1871 by chemical properties ), and Bohr was immediately challenged by the French chemist Georges Urbain , who claimed to have discovered

11092-524: The U.S. Atomic Energy Commission produced 0.8 kW in a test on 20 December 1951 and 100 kW (electrical) the following day, having a design output of 200 kW (electrical). Besides the military uses of nuclear reactors, there were political reasons to pursue civilian use of atomic energy. U.S. President Dwight Eisenhower made his famous Atoms for Peace speech to the UN General Assembly on 8 December 1953. This diplomacy led to

11280-447: The atom had challenged Thomson's 1904 plum pudding model . Bohr received an invitation from Rutherford to conduct post-doctoral work at Victoria University of Manchester , where Bohr met George de Hevesy and Charles Galton Darwin (whom Bohr referred to as "the grandson of the real Darwin "). Bohr returned to Denmark in July 1912 for his wedding, and travelled around England and Scotland on his honeymoon. On his return, he became

11468-477: The coolant also acts as a neutron moderator . A moderator increases the power of the reactor by causing the fast neutrons that are released from fission to lose energy and become thermal neutrons. Thermal neutrons are more likely than fast neutrons to cause fission. If the coolant is a moderator, then temperature changes can affect the density of the coolant/moderator and therefore change power output. A higher temperature coolant would be less dense, and therefore

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11656-411: The de Broglie hypothesis that matter (like electrons) also behaved like waves. He conceived the philosophical principle of complementarity : that items could have apparently mutually exclusive properties, such as being a wave or a stream of particles, depending on the experimental framework. He felt that it was not fully understood by professional philosophers. In February 1927, Heisenberg developed

11844-430: The scram system. They were suspended from steel cables that were wound around a drum and held in place by an electromagnetic clutch . If power was lost, they would drop into the reactor, halting it. The other four rods were made of boron steel and horizontally penetrated the reactor from the north side. Two of them, known as "shim" rods, were hydraulically controlled. Sand-filled hydraulic accumulators could be used in

12032-402: The "iodine pit." If the reactor has sufficient extra reactivity capacity, it can be restarted. As the extra xenon-135 is transmuted to xenon-136, which is much less a neutron poison, within a few hours the reactor experiences a "xenon burnoff (power) transient". Control rods must be further inserted to replace the neutron absorption of the lost xenon-135. Failure to properly follow such a procedure

12220-516: The (different) apparent frequencies of the Bohr orbits, led Max Born, Werner Heisenberg and Kramers to explore different mathematical models. They led to the development of matrix mechanics , the first form of modern quantum mechanics . The BKS theory also generated discussion of, and renewed attention to, difficulties in the foundations of the old quantum theory. The most provocative element of BKS – that momentum and energy would not necessarily be conserved in each interaction, but only statistically –

12408-580: The 1986 Chernobyl disaster and 2011 Fukushima disaster . As of 2022 , the International Atomic Energy Agency reported there are 422 nuclear power reactors and 223 nuclear research reactors in operation around the world. The US Department of Energy classes reactors into generations, with the majority of the global fleet being Generation II reactors constructed from the 1960s to 1990s, and Generation IV reactors currently in development. Reactors can also be grouped by

12596-742: The 50th anniversary of Hendrick Lorentz receiving his doctorate. When his train stopped in Hamburg , he was met by Wolfgang Pauli and Otto Stern , who asked for his opinion of the spin theory. Bohr pointed out that he had concerns about the interaction between electrons and magnetic fields. When he arrived in Leiden, Paul Ehrenfest and Albert Einstein informed Bohr that Einstein had resolved this problem using relativity . Bohr then had Uhlenbeck and Goudsmit incorporate this into their paper. Thus, when he met Werner Heisenberg and Pascual Jordan in Göttingen on

12784-481: The 60-inch cyclotron there in May 1941 and found that it had 1.7 times the thermal neutron capture cross section of uranium-235. At the time plutonium-239 had been produced in minute quantities using cyclotrons, but it was not possible to produce large quantities that way. Compton discussed with Eugene Wigner from Princeton University how plutonium might be produced in a nuclear reactor , and with Robert Serber how

12972-537: The Born statistical interpretation because he believed that the ψ -function has only a symbolic meaning and does not represent anything real". Since for Bohr, the ψ -function is not a literal pictorial representation of reality, there can be no real collapse of the wavefunction. A much debated point in recent literature is what Bohr believed about atoms and their reality and whether they are something else than what they seem to be. Some like Henry Folse argue that Bohr saw

13160-549: The British physicist Paul Dirac , who came to Copenhagen for six months in September 1926. Austrian physicist Erwin Schrödinger also visited in 1926. His attempt at explaining quantum physics in classical terms using wave mechanics impressed Bohr, who believed it contributed "so much to mathematical clarity and simplicity that it represents a gigantic advance over all previous forms of quantum mechanics". When Kramers left

13348-488: The Chair of Theoretical Physics at the University of Copenhagen, a position created especially for him. His docentship was abolished at the same time, so he still had to teach physics to medical students. New professors were formally introduced to King Christian X , who expressed his delight at meeting such a famous football player. In April 1917, Bohr began a campaign to establish an Institute of Theoretical Physics. He gained

13536-451: The Latin name for Copenhagen), turned out to be more common than gold. In 1922, Bohr was awarded the Nobel Prize in Physics "for his services in the investigation of the structure of atoms and of the radiation emanating from them". The award thus recognised both the trilogy and his early leading work in the emerging field of quantum mechanics. For his Nobel lecture, Bohr gave his audience

13724-461: The Metallurgical Laboratory developed several designs. In November 1942, the DuPont engineers chose helium gas as the coolant for the production plant, mainly on the basis that it did not absorb neutrons but also because it was inert, which removed the issue of corrosion. Not everyone agreed with the decision to use helium. Szilard, in particular, was an early proponent of using liquid bismuth ; but

13912-542: The Metallurgical Laboratory in Chicago in April 1943, by which time DuPont began transferring its technicians to the site. They were augmented by 100 technicians in uniform from the Army's Special Engineer Detachment . By March 1944, there were some 1,500 people working at X-10. Supervised by Compton, Whitaker, and Fermi, the reactor went critical on November 4, 1943, with about 30 short tons (27 t) of uranium. A week later

14100-464: The Nazis considered their family to be Jewish , since their mother was Jewish, and that they were therefore in danger of being arrested. The Danish resistance helped Bohr and his wife escape by sea to Sweden on 29 September. The next day, Bohr persuaded King Gustaf V of Sweden to make public Sweden's willingness to provide asylum to Jewish refugees. On 2 October 1943, Swedish radio broadcast that Sweden

14288-617: The Second World War, Nazi Germany invaded and occupied Denmark . To prevent the Germans from discovering Max von Laue 's and James Franck's gold Nobel medals , Bohr had de Hevesy dissolve them in aqua regia . In this form, they were stored on a shelf at the Institute until after the war, when the gold was precipitated and the medals re-struck by the Nobel Foundation. Bohr's own medal had been donated to an auction to

14476-490: The U.S. Hans  [ da ] became a physician; Erik  [ da ] , a chemical engineer; and Ernest , a lawyer. Like his uncle Harald, Ernest Bohr became an Olympic athlete, playing field hockey for Denmark at the 1948 Summer Olympics in London. In September 1911, Bohr, supported by a fellowship from the Carlsberg Foundation , travelled to England, where most of the theoretical work on

14664-685: The U.S. military sought other uses for nuclear reactor technology. Research by the Army led to the power stations for Camp Century, Greenland and McMurdo Station, Antarctica Army Nuclear Power Program . The Air Force Nuclear Bomber project resulted in the Molten-Salt Reactor Experiment . The U.S. Navy succeeded when they steamed the USS Nautilus (SSN-571) on nuclear power 17 January 1955. The first commercial nuclear power station, Calder Hall in Sellafield , England

14852-660: The UK's follow-on Magnox and AGR designs used carbon dioxide instead. As of 2016, another reactor of similar design to the X-10 Graphite Reactor is still in operation, the Belgian BR-1 reactor of the SCK•CEN , located in Mol, Belgium . Financed through the Belgian uranium export tax, and built with the help of British experts, the 4 MW research reactor went critical on May 11, 1956. It

15040-472: The United States does not engage in or encourage reprocessing. Reactors are also used in nuclear propulsion of vehicles. Nuclear marine propulsion of ships and submarines is largely restricted to naval use. Reactors have also been tested for nuclear aircraft propulsion and spacecraft propulsion . Reactor safety is maintained through various systems that control the rate of fission. The insertion of control rods, which absorb neutrons, can rapidly decrease

15228-415: The United States, and under the 1946 McMahon Act , the United States would not supply it for nuclear weapons production, so in the end air cooling was chosen. Construction began in September 1947, and the two reactors became operational in October 1950 and June 1951. Both were decommissioned after the disastrous Windscale fire in October 1957. They were the last major air-cooled plutonium-producing reactors;

15416-565: The World War II Allied Manhattan Project . The world's first artificial nuclear reactor, Chicago Pile-1, achieved criticality on 2 December 1942. Early reactor designs sought to produce weapons-grade plutonium for fission bombs , later incorporating grid electricity production in addition. In 1957, Shippingport Atomic Power Station became the first reactor dedicated to peaceful use; in Russia, in 1954,

15604-796: The account of the experimental arrangement and of the results of the observations must be expressed in unambiguous language with suitable application of the terminology of classical physics ( APHK , p. 39). According to Faye, there are various explanations for why Bohr believed that classical concepts were necessary for describing quantum phenomena. Faye groups explanations into five frameworks: empiricism (i.e. logical positivism ); Kantianism (or Neo-Kantian models of epistemology ); Pragmatism (which focus on how human beings experientially interact with atomic systems according to their needs and interests); Darwinianism (i.e. we are adapted to use classical type concepts, which Léon Rosenfeld said that we evolved to use); and Experimentalism (which focuses strictly on

15792-516: The area was contaminated, like Fukushima, Three Mile Island, Sellafield, and Chernobyl. The British branch of the French concern EDF Energy , for example, extended the operating lives of its Advanced Gas-cooled Reactors (AGR) with only between 3 and 10 years. All seven AGR plants were expected to be shut down in 2022 and in decommissioning by 2028. Hinkley Point B was extended from 40 to 46 years, and closed. The same happened with Hunterston B , also after 46 years. An increasing number of reactors

15980-609: The arts, as an honorary residence (Danish: Æresbolig ). Harald Høffding had been the first occupant, and upon his death in July 1931, the Royal Danish Academy of Sciences and Letters gave Bohr occupancy. He and his family moved there in 1932. He was elected president of the Academy on 17 March 1939. By 1929 the phenomenon of beta decay prompted Bohr to again suggest that the law of conservation of energy be abandoned, but Enrico Fermi 's hypothetical neutrino and

16168-419: The atom. Planetary models of atoms were not new, but Bohr's treatment was. Taking the 1912 paper by Darwin on the role of electrons in the interaction of alpha particles with a nucleus as his starting point, he advanced the theory of electrons travelling in orbits of quantised "stationary states" around the atom's nucleus in order to stabilise the atom, but it wasn't until his 1921 paper that he showed that

16356-480: The average of 4.3 inches (110 mm). Some 700 short tons (640 t) of graphite blocks were purchased from National Carbon . The construction crews began stacking them in September 1943. Cast uranium billets came from Metal Hydrides, Mallinckrodt and other suppliers. These were extruded into cylindrical slugs and then canned. The fuel slugs were canned to protect the uranium metal from corrosion that would occur if it came into contact with water and to prevent

16544-688: The beginning of his quest to produce the Einstein-Szilárd letter to alert the U.S. government. Shortly after, Nazi Germany invaded Poland in 1939, starting World War II in Europe. The U.S. was not yet officially at war, but in October, when the Einstein-Szilárd letter was delivered to him, Roosevelt commented that the purpose of doing the research was to make sure "the Nazis don't blow us up." The U.S. nuclear project followed, although with some delay as there remained skepticism (some of it from Enrico Fermi ) and also little action from

16732-554: The bismuth-phosphate process that was used in the full-scale separation facilities at Hanford. The reactor and chemical separation plant provided invaluable experience for engineers, technicians, reactor operators, and safety officials who then moved on to the Hanford Site. After the war ended, the graphite reactor became the first facility in the world to produce radioactive isotopes for peacetime use. On August 2, 1946, Oak Ridge National Laboratory director Eugene Wigner presented

16920-426: The chemical properties of each element were largely determined by the number of electrons in the outer orbits of its atoms. He introduced the idea that an electron could drop from a higher-energy orbit to a lower one, in the process emitting a quantum of discrete energy. This became a basis for what is now known as the old quantum theory . In 1885, Johann Balmer had come up with his Balmer series to describe

17108-458: The choices of coolant and moderator. Almost 90% of global nuclear energy comes from pressurized water reactors and boiling water reactors , which use water as a coolant and moderator. Other designs include heavy water reactors , gas-cooled reactors , and fast breeder reactors , variously optimizing efficiency, safety, and fuel type , enrichment , and burnup . Small modular reactors are also an area of current development. These reactors play

17296-669: The classical ones being manifested in measurement." The rise of Nazism in Germany prompted many scholars to flee their countries, either because they were Jewish or because they were political opponents of the Nazi regime. In 1933, the Rockefeller Foundation created a fund to help support refugee academics, and Bohr discussed this programme with the President of the Rockefeller Foundation, Max Mason , in May 1933 during

17484-467: The complexities of handling actinides , but significant scientific and technical obstacles remain. Despite research having started in the 1950s, no commercial fusion reactor is expected before 2050. The ITER project is currently leading the effort to harness fusion power. Thermal reactors generally depend on refined and enriched uranium . Some nuclear reactors can operate with a mixture of plutonium and uranium (see MOX ). The process by which uranium ore

17672-433: The concepts of classical physics are merely a refinement of them. Therefore, for Bohr, classical concepts need to be used to describe experiments that deal with the quantum world. Bohr writes: [T]he account of all evidence must be expressed in classical terms. The argument is simply that by the word 'experiment' we refer to a situation where we can tell to others what we have done and what we have learned and that, therefore,

17860-422: The content of a theory while accepting its general premises and structure. There has been much subsequent debate and discussion about Bohr's views and philosophy of quantum mechanics. Regarding his ontological interpretation of the quantum world, Bohr has been seen as an anti-realist , an instrumentalist , a phenomenological realist or some other kind of realist. Furthermore, though some have seen Bohr as being

18048-487: The contractor had only three-quarters of the required workforce, and there was high turnover and absenteeism, mainly the result of poor accommodations and difficulties in commuting. The township of Oak Ridge was still under construction, and barracks were built to house workers. Special arrangements with individual workers increased their morale and reduced turnover. Furthermore, there was unusually heavy rainfall, with 9.3 inches (240 mm) falling in July 1943, more than twice

18236-404: The desired power level was reached, the reactor was controlled by adjusting the partly inserted shim rod. The first batch of canned slugs to be irradiated was received on December 20, 1943, allowing the first plutonium to be produced in early 1944. The slugs used pure metallic natural uranium, in air-tight aluminum cans 4.1 inches (100 mm) long and 1 inch (25 mm) in diameter. Each channel

18424-565: The director of the Manhattan Project, agreed that the semiworks would be built at the Clinton Engineer Works. Both Compton and Groves proposed that DuPont operate the semiworks. Williams counter-proposed that the semiworks be operated by the Metallurgical Laboratory. He reasoned that it would primarily be a research and educational facility, and that expertise was to be found at the Metallurgical Laboratory. Compton

18612-688: The dissemination of reactor technology to U.S. institutions and worldwide. The first nuclear power plant built for civil purposes was the AM-1 Obninsk Nuclear Power Plant , launched on 27 June 1954 in the Soviet Union . It produced around 5 MW (electrical). It was built after the F-1 (nuclear reactor) which was the first reactor to go critical in Europe, and was also built by the Soviet Union. After World War II,

18800-494: The energy of the neutrons that sustain the fission chain reaction : In principle, fusion power could be produced by nuclear fusion of elements such as the deuterium isotope of hydrogen . While an ongoing rich research topic since at least the 1940s, no self-sustaining fusion reactor for any purpose has ever been built. Used by thermal reactors: In 2003, the French Commissariat à l'Énergie Atomique (CEA)

18988-478: The event of a power failure. The other two rods were driven by electric motors. The cooling system consisted of three electric fans running at 55,000 cubic feet per minute (1,600 m/min). Because it was cooled using outside air, the reactor could be run at a higher power level on cold days. After going through the reactor, the air was filtered to remove radioactive particles larger than 0.00004 inches (0.0010 mm) in diameter. This took care of over 99 percent of

19176-409: The feasibility of nuclear reactors, the Manhattan Project's goal of producing enough plutonium for atomic bombs required reactors a thousand times as powerful, along with facilities to chemically separate the plutonium bred in the reactors from uranium and fission products . An intermediate step was considered prudent. The next step for the plutonium project, codenamed X-10, was the construction of

19364-421: The final attempt at understanding the interaction of matter and electromagnetic radiation on the basis of the old quantum theory, in which quantum phenomena were treated by imposing quantum restrictions on a classical wave description of the electromagnetic field. Modelling atomic behaviour under incident electromagnetic radiation using "virtual oscillators" at the absorption and emission frequencies, rather than

19552-553: The first chairman of the Nordic Institute for Theoretical Physics in 1957. Niels Henrik David Bohr was born in Copenhagen , Denmark, on 7 October 1885, the second of three children of Christian Bohr , a professor of physiology at the University of Copenhagen, and his wife Ellen née Adler, who came from a wealthy Jewish banking family. He had an elder sister, Jenny, and a younger brother Harald . Jenny became

19740-524: The first small nuclear power reactor APS-1 OBNINSK reached criticality. Other countries followed suit. Heat from nuclear fission is passed to a working fluid coolant (water or gas), which in turn runs through turbines . In commercial reactors, turbines drive electrical generator shafts. The heat can also be used for district heating , and industrial applications including desalination and hydrogen production . Some reactors are used to produce isotopes for medical and industrial use. Reactors pose

19928-434: The first version of the uncertainty principle , presenting it using a thought experiment where an electron was observed through a gamma-ray microscope . Bohr was dissatisfied with Heisenberg's argument, since it required only that a measurement disturb properties that already existed, rather than the more radical idea that the electron's properties could not be discussed at all apart from the context they were measured in. In

20116-407: The fission process generates heat, some of which can be converted into usable energy. A common method of harnessing this thermal energy is to use it to boil water to produce pressurized steam which will then drive a steam turbine that turns an alternator and generates electricity. Modern nuclear power plants are typically designed for a lifetime of 60 years, while older reactors were built with

20304-529: The form of boric acid ) into the reactor to shut the fission reaction down if unsafe conditions are detected or anticipated. Most types of reactors are sensitive to a process variously known as xenon poisoning, or the iodine pit . The common fission product Xenon-135 produced in the fission process acts as a neutron poison that absorbs neutrons and therefore tends to shut the reactor down. Xenon-135 accumulation can be controlled by keeping power levels high enough to destroy it by neutron absorption as fast as it

20492-424: The fuel rods. This allows the reactor to be constructed with an excess of fissionable material, which is nevertheless made relatively safe early in the reactor's fuel burn cycle by the presence of the neutron-absorbing material which is later replaced by normally produced long-lived neutron poisons (far longer-lived than xenon-135) which gradually accumulate over the fuel load's operating life. The energy released in

20680-404: The function and outcome of experiments that thus must be described classically). These explanations are not mutually exclusive, and at times Bohr seems to emphasise some of these aspects while at other times he focuses on other elements. According to Faye "Bohr thought of the atom as real. Atoms are neither heuristic nor logical constructions." However, according to Faye, he did not believe "that

20868-447: The idea of nuclear fission as a neutron source, since that process was not yet discovered. Szilárd's ideas for nuclear reactors using neutron-mediated nuclear chain reactions in light elements proved unworkable. Inspiration for a new type of reactor using uranium came from the discovery by Otto Hahn , Lise Meitner , and Fritz Strassmann in 1938 that bombardment of uranium with neutrons (provided by an alpha-on-beryllium fusion reaction,

21056-477: The inevitably victorious Nazis and that he was shocked that Germany was pursuing nuclear weapons under Heisenberg's leadership. Michael Frayn 's 1998 play Copenhagen explores what might have happened at the 1941 meeting between Heisenberg and Bohr. A television film version of the play by the BBC was first screened on 26 September 2002, with Stephen Rea as Bohr. With the subsequent release of Bohr's letters,

21244-495: The institute in 1926 to take up a chair as professor of theoretical physics at the Utrecht University , Bohr arranged for Heisenberg to return and take Kramers's place as a lektor at the University of Copenhagen. Heisenberg worked in Copenhagen as a university lecturer and assistant to Bohr from 1926 to 1927. Bohr became convinced that light behaved like both waves and particles and, in 1927, experiments confirmed

21432-528: The institute's first publication even before it opened. The Bohr model worked well for hydrogen and ionized single-electron helium, which impressed Einstein but could not explain more complex elements. By 1919, Bohr was moving away from the idea that electrons orbited the nucleus and developed heuristics to describe them. The rare-earth elements posed a particular classification problem for chemists because they were so chemically similar. An important development came in 1924 with Wolfgang Pauli 's discovery of

21620-553: The literature on the subject, settling on a model postulated by Paul Drude and elaborated by Hendrik Lorentz , in which the electrons in a metal are considered to behave like a gas. Bohr extended Lorentz's model, but was still unable to account for phenomena like the Hall effect , and concluded that electron theory could not fully explain the magnetic properties of metals. The thesis was accepted in April 1911, and Bohr conducted his formal defence on 13 May. Harald had received his doctorate

21808-407: The load was increased to 36 short tons (33 t), raising its power generation to 500 kW, and by the end of the month the first 500 mg of plutonium were created. The reactor normally operated around the clock, with 10-hour weekly shutdowns for refueling. During startup, the safety rods and one shim rod were completely removed. The other shim rod was inserted at a predetermined position. When

21996-518: The main subject of the meeting was Carl Friedrich von Weizsäcker , who had proposed trying to persuade Bohr to mediate peace between Britain and Germany. In 1957, Heisenberg wrote to Robert Jungk , who was then working on the book Brighter than a Thousand Suns: A Personal History of the Atomic Scientists . Heisenberg explained that he had visited Copenhagen to communicate to Bohr the views of several German scientists, that production of

22184-475: The major opponent was Wigner, who argued forcefully in favor of a water-cooled reactor design. He realized that since water absorbed neutrons, k would be reduced by about 3 percent, but he had sufficient confidence in his calculations that the water-cooled reactor would still be able to achieve criticality . From an engineering perspective, a water-cooled design was straightforward to design and build, while helium posed technological problems. Wigner's team produced

22372-517: The mathematician Niels Erik Nørlund . Bohr resigned his membership in the Church of Denmark on 16 April 1912, and he and Margrethe were married in a civil ceremony at the town hall in Slagelse on 1 August. Years later, his brother Harald similarly left the church before getting married. Bohr and Margrethe had six sons. The oldest, Christian, died in a boating accident in 1934, and another, Harald,

22560-437: The most commonly used medical radioisotope. The BNL Graphite Research Reactor was shut down in 1969 and fully decommissioned in 2012. When Britain began planning to build nuclear reactors to produce plutonium for weapons in 1946, it was decided to build a pair of air-cooled graphite reactors similar to the X-10 Graphite Reactor at Windscale . Natural uranium was used as enriched uranium was not available, and similarly graphite

22748-600: The news to the United States where he opened the Fifth Washington Conference on Theoretical Physics with Fermi on 26 January 1939. When Bohr told George Placzek that this resolved all the mysteries of transuranic elements , Placzek told him that one remained: the neutron capture energies of uranium did not match those of its decay. Bohr thought about it for a few minutes and then announced to Placzek, Léon Rosenfeld and John Wheeler that "I have understood everything." Based on his liquid drop model of

22936-449: The normal nuclear chain reaction, would be too short to allow for intervention. This last stage, where delayed neutrons are no longer required to maintain criticality, is known as the prompt critical point. There is a scale for describing criticality in numerical form, in which bare criticality is known as zero dollars and the prompt critical point is one dollar , and other points in the process interpolated in cents. In some reactors,

23124-571: The novel aspects of quantum mechanics became widely celebrated subjects of discussion. Einstein and Bohr had good-natured arguments over such issues throughout their lives. In 1914 Carl Jacobsen , the heir to Carlsberg breweries , bequeathed his mansion (the Carlsberg Honorary Residence, currently known as Carlsberg Academy) to be used for life by the Dane who had made the most prominent contribution to science, literature or

23312-431: The nucleus, Bohr concluded that it was the uranium-235 isotope and not the more abundant uranium-238 that was primarily responsible for fission with thermal neutrons. In April 1940, John R. Dunning demonstrated that Bohr was correct. In the meantime, Bohr and Wheeler developed a theoretical treatment, which they published in a September 1939 paper on "The Mechanism of Nuclear Fission". Heisenberg said of Bohr that he

23500-478: The object was an important condition for attaining knowledge. This can only be done through the use of causal and spatial-temporal concepts to describe the subject's experience. Thus, according to Jan Faye, Bohr thought that it is because of "classical" concepts like "space", "position", "time", "causation", and "momentum" that one can talk about objects and their objective existence. Bohr held that basic concepts like "time" are built in to our ordinary language and that

23688-581: The opportunity for the nuclear chain reaction that Szilárd had envisioned six years previously. On 2 August 1939, Albert Einstein signed a letter to President Franklin D. Roosevelt (written by Szilárd) suggesting that the discovery of uranium's fission could lead to the development of "extremely powerful bombs of a new type", giving impetus to the study of reactors and fission. Szilárd and Einstein knew each other well and had worked together years previously, but Einstein had never thought about this possibility for nuclear energy until Szilard reported it to him, at

23876-406: The physics of radioactive decay and are simply accounted for during the reactor's operation, while others are mechanisms engineered into the reactor design for a distinct purpose. The fastest method for adjusting levels of fission-inducing neutrons in a reactor is via movement of the control rods . Control rods are made of so-called neutron poisons and therefore absorb neutrons. When a control rod

24064-550: The pilot facilities, while an 83,000-acre (34,000 ha) site for the production facilities was selected at Oak Ridge, Tennessee . By the S-1 Executive Committee meeting on September 13 and 14, it had become apparent that the pilot facilities would be too extensive for the Argonne site, so instead a research reactor would be built at Argonne, while the plutonium pilot facilities (a semiworks ) would be built at

24252-512: The pilot separation plant before a chemical process for separating plutonium from uranium had been selected. Not until May 1943 would DuPont managers decide to use the bismuth phosphate process in preference to one using lanthanum fluoride . The bismuth phosphate process was devised by Stanley G. Thompson at the University of California . Plutonium had two oxidation states; a tetravalent (+4) state, and hexavalent (+6) state, with different chemical properties. Bismuth phosphate ( BiPO 4 )

24440-642: The play has been criticised by historians as being a "grotesque oversimplification and perversion of the actual moral balance" due to adopting a pro-Heisenberg perspective. The same meeting had previously been dramatised by the BBC's Horizon science documentary series in 1992, with Anthony Bate as Bohr, and Philip Anthony as Heisenberg. The meeting is also dramatised in the Norwegian/Danish/British miniseries The Heavy Water War . In September 1943, word reached Bohr and his brother Harald that

24628-428: The plutonium from the uranium, and to design and build an atomic bomb. It fell to Compton to decide which of the different types of reactor designs the scientists should pursue, even though a successful reactor had not yet been built. He felt that having teams at Columbia, Princeton, the University of Chicago and the University of California was creating too much duplication and not enough collaboration, and he concentrated

24816-490: The plutonium produced in a reactor might be separated from uranium. The final draft of Compton's November 1941 report made no mention of using plutonium, but after discussing the latest research with Ernest Lawrence , Compton became convinced that a plutonium bomb was also feasible. In December, Compton was placed in charge of the plutonium project, which was codenamed X-10. Its objectives were to produce reactors to convert uranium to plutonium, to find ways to chemically separate

25004-541: The possibility of a controlled nuclear chain reaction with uranium . At Columbia University , Enrico Fermi and Leo Szilard began exploring how this might be done. Szilard drafted a confidential letter to the President of the United States , Franklin D. Roosevelt , explaining the possibility of atomic bombs , and warning of the danger of a German nuclear weapon project . He convinced his old friend and collaborator Albert Einstein to co-sign it, lending his fame to

25192-463: The power plant is limited by the life of components that cannot be replaced when aged by wear and neutron embrittlement , such as the reactor pressure vessel. At the end of their planned life span, plants may get an extension of the operating license for some 20 years and in the US even a "subsequent license renewal" (SLR) for an additional 20 years. Even when a license is extended, it does not guarantee

25380-576: The previous year. Bohr's thesis was groundbreaking, but attracted little interest outside Scandinavia because it was written in Danish, a Copenhagen University requirement at the time. In 1921, the Dutch physicist Hendrika Johanna van Leeuwen would independently derive a theorem in Bohr's thesis that is today known as the Bohr–Van Leeuwen theorem . In 1910, Bohr met Margrethe Nørlund , the sister of

25568-620: The principle of complementarity : that items could be separately analysed in terms of contradictory properties, like behaving as a wave or a stream of particles . The notion of complementarity dominated Bohr's thinking in both science and philosophy. Bohr founded the Institute of Theoretical Physics at the University of Copenhagen , now known as the Niels Bohr Institute , which opened in 1920. Bohr mentored and collaborated with physicists including Hans Kramers , Oskar Klein , George de Hevesy , and Werner Heisenberg . He predicted

25756-535: The production plants. The semiworks would also be used for training and for developing procedures. Although the design of the reactor was not yet complete, DuPont began construction of the plutonium semiworks on February 2, 1943, on an isolated 112-acre (45.3 ha) site in Bethel Valley about 10 miles (16 km) southwest of Oak Ridge, officially known as the X-10 area. The site included research laboratories,

25944-483: The properties of a new zirconium -like element, which was named hafnium , after the Latin name for Copenhagen, where it was discovered. Later, the synthetic element bohrium was named after him. During the 1930s, Bohr helped refugees from Nazism . After Denmark was occupied by the Germans , he met with Heisenberg, who had become the head of the German nuclear weapon project . In September 1943 word reached Bohr that he

26132-588: The proposal. This resulted in support by the U.S. government for research into nuclear fission, which became the Manhattan Project . In April 1941, the National Defense Research Committee asked Arthur Compton , a Nobel-Prize-winning physics professor at the University of Chicago , to report on the uranium program. His report, submitted in May 1941, foresaw the prospects of developing radiological weapons , nuclear propulsion for ships, and nuclear weapons using uranium-235 or

26320-439: The quantum mechanical formalism was true in the sense that it gave us a literal ('pictorial') rather than a symbolic representation of the quantum world." Therefore, Bohr's theory of complementarity "is first and foremost a semantic and epistemological reading of quantum mechanics that carries certain ontological implications". As Faye explains, Bohr's indefinability thesis is that [T]he truth conditions of sentences ascribing

26508-460: The radioactive particles. It was then vented through a 200-foot (61 m) chimney. The reactor was operated from a control room in the southeast corner on the second floor. In September 1942, Compton asked physicist Martin D. Whitaker to form a skeleton operating staff for X-10. Whitaker became the inaugural director of the Clinton Laboratories, as the semiworks became officially known in April 1943. The first permanent operating staff arrived from

26696-405: The reactor core. Water was circulated through the tube by means of an automatic feedwater system to generate steam. This steam was fed to a model steam engine , a Jensen Steam Engines #50, which drove a small generator that powered a single bulb. The engine and generator are on display at the reactor loading face, just below the staircase leading to the loading platform. The X-10 Graphite Reactor

26884-519: The reactor fleet grows older. The neutron was discovered in 1932 by British physicist James Chadwick . The concept of a nuclear chain reaction brought about by nuclear reactions mediated by neutrons was first realized shortly thereafter, by Hungarian scientist Leó Szilárd , in 1933. He filed a patent for his idea of a simple reactor the following year while working at the Admiralty in London, England. However, Szilárd's idea did not incorporate

27072-416: The reactor will continue to operate, particularly in the face of safety concerns or incident. Many reactors are closed long before their license or design life expired and are decommissioned . The costs for replacements or improvements required for continued safe operation may be so high that they are not cost-effective. Or they may be shut down due to technical failure. Other ones have been shut down because

27260-437: The reactor's output, while other systems automatically shut down the reactor in the event of unsafe conditions. The buildup of neutron-absorbing fission products like xenon-135 can influence reactor behavior, requiring careful management to prevent issues such as the iodine pit , which can complicate reactor restarts. There have been two reactor accidents classed as an International Nuclear Event Scale Level 7 "major accident":

27448-503: The reactor's power to 4,000 kW in July 1944. The effect of the neutron poison xenon-135 , one of many fission products produced from the uranium fuel, was not detected during the early operation of the X-10 Graphite Reactor. Xenon-135 subsequently caused problems with the startup of the Hanford B Reactor that nearly halted the plutonium project. The X-10 semiworks operated as a plutonium production plant until January 1945, when it

27636-402: The recently discovered plutonium . In October he wrote another report on the practicality of an atomic bomb. Niels Bohr and John Wheeler had theorized that heavy isotopes with even atomic numbers and odd number of neutrons were fissile . If so, then plutonium-239 was likely to be fissile. Emilio Segrè and Glenn Seaborg at the University of California produced 28 μg of plutonium in

27824-504: The required elliptical cross-sections. He went beyond the original task, incorporating improvements into both Rayleigh's theory and his method, by taking into account the viscosity of the water, and by working with finite amplitudes instead of just infinitesimal ones. His essay, which he submitted at the last minute, won the prize. He later submitted an improved version of the paper to the Royal Society in London for publication in

28012-599: The small number of officials in the government who were initially charged with moving the project forward. The following year, the U.S. Government received the Frisch–Peierls memorandum from the UK, which stated that the amount of uranium needed for a chain reaction was far lower than had previously been thought. The memorandum was a product of the MAUD Committee , which was working on the UK atomic bomb project, known as Tube Alloys , later to be subsumed within

28200-498: The staff at the Metallurgical Laboratory then reopened the question of building the plutonium semiworks at Argonne, but the engineers and management of DuPont , particularly Roger Williams (the head of its TNX Division, which was responsible for the company's role in the Manhattan Project), did not support this proposal. They felt that there would be insufficient space at Argonne and that there were disadvantages in having

28388-646: The structure of atoms and molecules was being done. He met J. J. Thomson of the Cavendish Laboratory and Trinity College, Cambridge . He attended lectures on electromagnetism given by James Jeans and Joseph Larmor , and did some research on cathode rays , but failed to impress Thomson. He had more success with younger physicists like the Australian William Lawrence Bragg , and New Zealand's Ernest Rutherford , whose 1911 small central nucleus Rutherford model of

28576-627: The subsequent 1932 discovery of the neutron provided another explanation. This prompted Bohr to create a new theory of the compound nucleus in 1936, which explained how neutrons could be captured by the nucleus. In this model, the nucleus could be deformed like a drop of liquid. He worked on this with a new collaborator, the Danish physicist Fritz Kalckar, who died suddenly in 1938. The discovery of nuclear fission by Otto Hahn in December 1938 (and its theoretical explanation by Lise Meitner ) generated intense interest among physicists. Bohr brought

28764-536: The support of the Danish government and the Carlsberg Foundation, and sizeable contributions were also made by industry and private donors, many of them Jewish. Legislation establishing the institute was passed in November 1918. Now known as the Niels Bohr Institute , it opened on 3 March 1921, with Bohr as its director. His family moved into an apartment on the first floor. Bohr's institute served as

28952-416: The total cost to $ 13,041,000 (equivalent to $ 155 million in 2023). Operational costs added another $ 22,250,000 (equivalent to $ 265 million in 2023). X-10 supplied the Los Alamos Laboratory with the first significant samples of plutonium. Studies of these by Emilio G. Segrè and his P-5 Group at Los Alamos revealed that it contained impurities in the form of the isotope plutonium-240 , which has

29140-414: The trilogy, but the younger generation, including Rutherford, David Hilbert , Albert Einstein , Enrico Fermi , Max Born and Arnold Sommerfeld saw it as a breakthrough. The trilogy's acceptance was entirely due to its ability to explain phenomena that stymied other models, and to predict results that were subsequently verified by experiments. Today, the Bohr model of the atom has been superseded, but

29328-413: The two men took a private moment outside, the content of which has caused much speculation, as both gave differing accounts. According to Heisenberg, he began to address nuclear energy, morality and the war, to which Bohr seems to have reacted by terminating the conversation abruptly while not giving Heisenberg hints about his own opinions. Ivan Supek , one of Heisenberg's students and friends, claimed that

29516-463: The venting of gaseous radioactive fission products that might be formed when they were irradiated. Aluminum was chosen because it transmitted heat well but did not absorb too many neutrons. Alcoa started canning on June 14, 1943. General Electric and the Metallurgical Laboratory developed a new welding technique to seal the cans airtight, and the equipment for this was installed in the production line at Alcoa in October 1943. Construction commenced on

29704-467: The visible spectral lines of a hydrogen atom: where λ is the wavelength of the absorbed or emitted light and R H is the Rydberg constant . Balmer's formula was corroborated by the discovery of additional spectral lines, but for thirty years, no one could explain why it worked. In the first paper of his trilogy, Bohr was able to derive it from his model: where m e is the electron's mass, e

29892-424: The water for the steam turbines is boiled directly by the reactor core ; for example the boiling water reactor . The rate of fission reactions within a reactor core can be adjusted by controlling the quantity of neutrons that are able to induce further fission events. Nuclear reactors typically employ several methods of neutron control to adjust the reactor's power output. Some of these methods arise naturally from

30080-523: The way back, he had become, in his own words, "a prophet of the electron magnet gospel". Heisenberg first came to Copenhagen in 1924, then returned to Göttingen in June 1925, shortly thereafter developing the mathematical foundations of quantum mechanics. When he showed his results to Max Born in Göttingen, Born realised that they could best be expressed using matrices . This work attracted the attention of

30268-455: The work at the Metallurgical Laboratory at the University of Chicago. By June 1942, the Manhattan Project had reached the stage where the construction of production facilities could be contemplated. On June 25, 1942, the Office of Scientific Research and Development S-1 Executive Committee deliberated on where they should be located. Moving directly to a megawatt production plant looked like

30456-489: The year was desirable. Terrain separated by ridges would reduce the impact of accidental explosions, but they could not be so steep as to complicate construction. The substratum needed to be firm enough to provide good foundations but not so rocky that it would hinder excavation work. It needed large amounts of electrical power (available from the Tennessee Valley Authority ) and cooling water. Finally,

30644-645: Was "primarily a philosopher, not a physicist". Bohr read the 19th-century Danish Christian existentialist philosopher Søren Kierkegaard . Richard Rhodes argued in The Making of the Atomic Bomb that Bohr was influenced by Kierkegaard through Høffding. In 1909, Bohr sent his brother Kierkegaard's Stages on Life's Way as a birthday gift. In the enclosed letter, Bohr wrote, "It is the only thing I have to send home; but I do not believe that it would be very easy to find anything better ... I even think it

30832-459: Was 10 percent more than in the purest graphite, heavy water would be unavailable in sufficient quantities for at least a year. This left the choice of coolant, over which there was much discussion. A limiting factor was that the fuel slugs would be clad in aluminum , so the operating temperature of the reactor could not exceed 200 °C (392 °F). The theoretical physicists in Wigner's group at

31020-481: Was a key step in the Chernobyl disaster . Reactors used in nuclear marine propulsion (especially nuclear submarines ) often cannot be run at continuous power around the clock in the same way that land-based power reactors are normally run, and in addition often need to have a very long core life without refueling . For this reason many designs use highly enriched uranium but incorporate burnable neutron poison in

31208-400: Was a metal channel into which uranium fuel slugs could be inserted. An elevator provided access to those higher up. Only 800 (~64%) of the channels were ever used. The reactor used cadmium -clad steel control rods . Made from neutron-absorbing cadmium, these could restrict or halt the reaction. Three 8-foot (2.4 m) rods penetrated the reactor vertically, held in place by a clutch to form

31396-680: Was about to be arrested by the Germans, so he fled to Sweden. From there, he was flown to Britain, where he joined the British Tube Alloys nuclear weapons project, and was part of the British mission to the Manhattan Project . After the war, Bohr called for international cooperation on nuclear energy. He was involved with the establishment of CERN and the Research Establishment Risø of the Danish Atomic Energy Commission and became

31584-473: Was aware of the possibility of using uranium-235 to construct an atomic bomb , referring to it in lectures in Britain and Denmark shortly before and after the war started, but he did not believe that it was technically feasible to extract a sufficient quantity of uranium-235. In September 1941, Heisenberg, who had become head of the German nuclear energy project , visited Bohr in Copenhagen. During this meeting

31772-402: Was chosen as a neutron moderator because beryllia was toxic and hard to manufacture, while heavy water was unavailable. Use of water as a coolant was considered, but there were concerns about the possibility of a catastrophic nuclear meltdown in the densely populated British Isles if the cooling system failed. Helium was again the preferred choice as a coolant gas, but the main source of it was

31960-470: Was composed of photons and that energy and momentum were conserved in collisions between electrons and photons. In 1924, Bohr, Kramers, and John C. Slater , an American physicist working at the Institute in Copenhagen, proposed the Bohr–Kramers–Slater theory (BKS). It was more of a program than a full physical theory, as the ideas it developed were not worked out quantitatively. The BKS theory became

32148-456: Was gone you doubled the size of my university". The fundamental design decisions in building a reactor are the choice of fuel, coolant and neutron moderator . The choice of fuel was straightforward; only natural uranium was available. The decision that the reactor would use graphite as a neutron moderator caused little debate. Although with heavy water as moderator the number of neutrons produced for every one absorbed (known as k factor )

32336-479: Was higher than anticipated. This removed most of the objections to air-cooled and water-cooled reactor designs, and it greatly simplified other aspects of the design. Wigner's team submitted blueprints of a water-cooled reactor to DuPont in January 1943. By this time, the concerns of DuPont's engineers about the corrosiveness of water had been overcome by the mounting difficulties of using helium, and all work on helium

32524-400: Was loaded with between 24 and 54 fuel slugs. In its later life the reactor was operated with as much as 54 short tons (49 t). To load a channel, the radiation-absorbing shield plug was removed, and the slugs inserted manually in the front (east) end with long rods. To unload them, they were pushed all the way through to the far (west) end, where they fell onto a neoprene slab and fell down

32712-788: Was officially started by the Generation ;IV International Forum (GIF) based on eight technology goals. The primary goals being to improve nuclear safety, improve proliferation resistance, minimize waste and natural resource utilization, and to decrease the cost to build and run such plants. Generation V reactors are designs which are theoretically possible, but which are not being actively considered or researched at present. Though some generation V reactors could potentially be built with current or near term technology, they trigger little interest for reasons of economics, practicality, or safety. Controlled nuclear fusion could in principle be used in fusion power plants to produce power without

32900-463: Was opened in 1956 with an initial capacity of 50 MW (later 200 MW). The first portable nuclear reactor "Alco PM-2A" was used to generate electrical power (2 MW) for Camp Century from 1960 to 1963. All commercial power reactors are based on nuclear fission . They generally use uranium and its product plutonium as nuclear fuel , though a thorium fuel cycle is also possible. Fission reactors can be divided roughly into two classes, depending on

33088-512: Was operated by the University of Chicago as part of the Metallurgical Project. Construction work on the reactor had to wait until DuPont had completed the design. Excavation commenced on April 27, 1943. A large pocket of soft clay was soon discovered, necessitating additional foundations. Further delays occurred due to wartime difficulties in procuring building materials. There was an acute shortage of both common and skilled labor;

33276-428: Was operated from the control room by remote control due to the radioactivity produced by fission products. Work was completed on November 26, 1943, but the plant could not operate until the reactor started producing irradiated uranium slugs. The X-10 Graphite Reactor was the world's second artificial nuclear reactor after Chicago Pile-1 and was the first reactor designed and built for continuous operation. It consisted of

33464-409: Was seven. In 1903, Bohr enrolled as an undergraduate at Copenhagen University . His major was physics, which he studied under Professor Christian Christiansen , the university's only professor of physics at that time. He also studied astronomy and mathematics under Professor Thorvald Thiele , and philosophy under Professor Harald Høffding , a friend of his father. In 1905 a gold medal competition

33652-538: Was severely mentally disabled. He was placed in an institution away from his family's home at the age of four and died from childhood meningitis six years later. Aage Bohr became a successful physicist, and in 1975 was awarded the Nobel Prize in physics, like his father. A son of Aage, Vilhelm A. Bohr, is a scientist affiliated with the University of Copenhagen and the National Institute on Aging in

33840-520: Was shocked; the Metallurgical Laboratory was part of the University of Chicago, and therefore the university would be operating an industrial facility 500 miles (800 km) from its main campus. James B. Conant told him that Harvard University "wouldn't touch it with a ten-foot pole", but the University of Chicago's Vice President, Emery T. Filbey, took a different view and instructed Compton to accept. When University President Robert Hutchins returned, he greeted Compton with "I see, Arthur, that while I

34028-560: Was shut down on November 4, 1963, after 20 years of use. It was designated a National Historic Landmark on December 21, 1965, and added to the National Register of Historic Places on October 15, 1966. In 1969 the American Society for Metals listed it as a landmark for its contributions to the advancement of materials science and technology, and in 2008 it was designated as a National Historic Chemical Landmark by

34216-426: Was similar in its crystalline structure to plutonium phosphate, and plutonium would be carried with bismuth phosphate in a solution while other elements, including uranium, would be precipitated. The plutonium could be switched from being in solution to being precipitated by toggling its oxidation state. The plant consisted of six cells, separated from each other and the control room by thick concrete walls. The equipment

34404-434: Was soon shown to be in conflict with experiments conducted by Walther Bothe and Hans Geiger . In light of these results, Bohr informed Darwin that "there is nothing else to do than to give our revolutionary efforts as honourable a funeral as possible". The introduction of spin by George Uhlenbeck and Samuel Goudsmit in November 1925 was a milestone. The next month, Bohr travelled to Leiden to attend celebrations of

34592-570: Was sponsored by the Royal Danish Academy of Sciences and Letters to investigate a method for measuring the surface tension of liquids that had been proposed by Lord Rayleigh in 1879. This involved measuring the frequency of oscillation of the radius of a water jet. Bohr conducted a series of experiments using his father's laboratory in the university; the university itself had no physics laboratory. To complete his experiments, he had to make his own glassware , creating test tubes with

34780-401: Was terminated in February. At the same time, air cooling was chosen for the reactor at the pilot plant. Since it would be of a quite different design from the production reactors, the X-10 Graphite Reactor lost its value as a prototype, but its value as a working pilot facility remained, providing plutonium needed for research. It was hoped that problems would be found in time to deal with them in

34968-649: Was the first to refer to "Gen II" types in Nucleonics Week . The first mention of "Gen III" was in 2000, in conjunction with the launch of the Generation IV International Forum (GIF) plans. "Gen IV" was named in 2000, by the United States Department of Energy (DOE), for developing new plant types. More than a dozen advanced reactor designs are in various stages of development. Some are evolutionary from

35156-424: Was turned over to research activities and the production of radioactive isotopes for scientific, medical, industrial and agricultural uses. It was shut down in 1963 and was designated a National Historic Landmark in 1965. The discovery of nuclear fission by German chemists Otto Hahn and Fritz Strassmann in 1938, followed by its theoretical explanation (and naming) by Lise Meitner and Otto Frisch , opened up

35344-422: Was turned over to research activities. By this time, 299 batches of irradiated slugs had been processed. A radioisotope building, a steam plant, and other structures were added in April 1946 to support the laboratory's peacetime educational and research missions. All work was completed by December 1946, adding another $ 1,009,000 (equivalent to $ 12 million in 2023) to the cost of construction at X-10, and bringing

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