Chicago Pile-1 ( CP-1 ) is the world's first nuclear reactor. On December 2, 1942, the first human-made nuclear chain reaction started in CP-1, during an experiment led by Enrico Fermi. The construction of the reactor is part of the Manhattan Project, an allied effort to make atomic bombs during World War II. Built by the Metallurgical Laboratory at the University of Chicago, under the original Stagg Field western standpoint. Fermi described the apparatus as "a pile of black bricks and wood."
The reactor was assembled in November 1942, by a team that included Fermi, Leo Szilard (who previously formulated the idea for a non-fission chain reaction), Leona Woods, Herbert L. Anderson, Walter Zinn, Martin D. Whitaker, and George. Weil. It contains 45,000 graphite blocks weighing 400 short tons (360 Â °) used as a neutron moderator, and triggered by 6 short tons (5.4 Â °) uranium metal and 50 short tons (45 Â °) of uranium oxide. In the pile, some of the free neutrons produced by the natural decay of uranium are absorbed by other uranium atoms, causing nuclear division of the atoms, and the release of additional free neutrons. Unlike most subsequent nuclear reactors, it does not have a radiation or cooling system because it operates at very low power - about half a watt. The shape of the pile is meant to be approximately spherical, but when the work is running, Fermi calculates that a critical mass can be achieved without completing the entire pile as planned.
In 1943, CP-1 was transferred to Red Gate Woods, and configured to Chicago Pile-2 (CP-2). There, it was operated until 1954, when it was dismantled and buried. Stan at Stagg Field was destroyed in August 1957; the site is now a National Historic Landmark and Chicago Landmark.
Video Chicago Pile-1
Origins
The idea of ​​chemical chain reaction was first proposed in 1913 by the German chemist Max Bodenstein for a situation in which two molecules react to form not only the final reaction product, but also some unstable molecules which can subsequently react with the original substance to cause more reactions. The concept of nuclear chain reaction was first hypothesized by Hungarian scientist Leo Szilard on September 12, 1933. Szilard realizes that if a nuclear reaction produces a neutron or dineutron, which then causes further nuclear reactions, the process may occur by itself. Szilard proposed using a mixture of lighter isotopes that produce excessive amounts of neutrons, and also entertained the possibility of using uranium as a fuel. He filed a patent for his idea of ​​a simple nuclear reactor the following year. The discovery of nuclear fission by German chemists Otto Hahn and Fritz Strassmann in 1938, and his theoretical explanations (and naming) by their collaborators Lise Meitner and Otto Frisch, opened the possibility of creating nuclear chain reactions with uranium or indium, but the initial experiment was unsuccessful.
In order for a chain reaction to occur, the uranium atom emitting oxygen must emit additional neutrons to keep the reaction going. At Columbia University in New York, the Italian physicist Enrico Fermi, with American John Dunning, Herbert L. Anderson, Eugene T. Booth, G. Norris Glasoe, and Francis G. Slack conducted the first nuclear fission experiment in the United States on January 25 1939. Subsequent work ensures that rapid neutrons are indeed produced by fission. Szilard obtained permission from the head of the Physics Department at Columbia, George B. Pegram, to use the laboratory for three months, and persuaded Walter Zinn to become his collaborator. They conducted a simple experiment on the seventh floor of Pupin Hall in Columbia, using a radium-berillium source to bombard uranium with neutrons. They found significant multiplication of neutrons in natural uranium, proving that chain reactions are possible.
Fermi and Szilard still believe that large amounts of uranium will be required for an atomic bomb, and therefore concentrate on producing a controlled chain reaction. Fermi urged Alfred OC Nier to separate uranium isotopes for the determination of the fissile component, and, on February 29, 1940, Nier separated the first uranium-235 sample, which, after being sent to Dunning at Columbia, was confirmed as an isolated fissile material.. While he worked in Rome, Fermi has found that collisions between neutrons and neutron moderators can slow down neutrons, and thus make them more likely to be captured by uranium nuclei, causing uranium to become fission. Szilard suggested to Fermi that they use carbon in graphite as a moderator. As a backup plan, he considered heavy water. It contains deuterium, which will not absorb neutrons like normal hydrogen, and is a better neutron moderator than carbon; but heavy water is expensive and difficult to produce, and several tons may be needed. Fermi estimates that the fission uranium nucleus produces 1.73 neutrons on average. That's enough, but careful design is required to minimize losses. (Today the average number of neutrons emitted each uranium-235 fissioning core is known to be around 2.4).
Szilard estimates he will need about 50 short tons (45 t) of graphite and 5 short tons (4.5 t) of uranium. In December 1940, Fermi and Szilard met Herbert G. MacPherson and Victor C. Hamister at the National Carbon to discuss the possible presence of impurities in graphite, and the procurement of pure-grain graphite that has never been commercially produced. National Carbon, a chemical company, has taken an unusual step in hiring MacPherson, a physicist, to examine the carbon-arc lamp, the main commercial use for graphite at the time. Because of his study of carbon arc spectroscopy, MacPherson knows that the main relevant contaminant is boron, both because of its concentration and affinity for absorbing neutrons, justifying Szilard's suspicions. More importantly, MacPherson and Hamister believe that the technique for producing graphite of sufficient purity can be developed. Had Fermi and Szilard not consulted with MacPherson and Hamister, they might have concluded, as did Germany, that the graphite was not suitable for use as a neutron moderator.
Over the next two years, MacPherson, Hamister and Lauchlin M. Currie developed a thermal purification technique for the production of large-scale low-grade boron content. The resulting product is designated AGOT graphite ("Acheson Graphite Ordinary Temperature") by National Carbon. With a 4.97 mbarns neutron absorption cross section, AGOT graphite is considered the first true nuclear grade graphite. In November 1942, National Carbon shipped 255 tons of AGOT graphite to the University of Chicago, where it became the main source of graphite for use in the construction of Chicago Pile-1.
Maps Chicago Pile-1
Government support
Szilard composed a secret letter to the President, Franklin D. Roosevelt, warned the German nuclear weapons project, explaining the possibility of nuclear weapons, and encouraging the development of programs that could produce their creations. With the help of Eugene Wigner and Edward Teller, he approached his old friend and collaborator Albert Einstein in August 1939, and convinced him to sign the letter, lending a prestige to the proposal. Einstein-Szilard's letter resulted in the formation of research on nuclear splits by the US government. A Uranium Advisory Committee was formed under Lyman J. Briggs, a scientist and director of the National Bureau of Standards. The first meeting on 21 October 1939 was attended by Szilard, Teller and Wigner. Scientists persuaded the Army and Navy to provide Szilard $ 6,000 to buy inventory for experiments - in particular, more graphite.
In April 1941, the National Defense Research Committee (NDRC) created a special project led by Arthur Compton, a Nobel Prize-winning physics professor at the University of Chicago, to report on uranium programs. The Compton report, submitted in May 1941, foresees the prospect of developing radiological weapons, nuclear propulsion for ships, and nuclear weapons using uranium-235 or newly discovered plutonium. In October he wrote another report on the practicality of the atomic bomb. For this report, he worked with Fermi on the calculation of critical mass of uranium-235. He also discussed the prospect of uranium enrichment with Harold Urey.
Niels Bohr and John Wheeler have theorized that heavy isotopes with weird atomic mass numbers are fissile. If so, then plutonium-239 will most likely occur. In May 1941, Emilio SegrÃÆ'¨ and Glenn Seaborg at the University of California produced 28? G plutonium in a 60-inch cyclotron there, and found that it has a 1.7 times thermal neutron capture catch from uranium-235. At that time only a small amount of plutonium-239 is produced, in the cyclotron, and is unlikely to produce such a large enough amount. Compton discusses with Wigner how plutonium can be produced in a nuclear reactor, and with Robert Serber on how that plutonium might be separated from uranium. His report, presented in November, states that a bomb is worth doing.
The final draft of Compton's November 1941 report did not mention plutonium, but after discussing recent research with Ernest Lawrence, Compton became convinced that plutonium bombs were also feasible. In December, Compton was placed in charge of the plutonium project. The goal is to produce reactors to convert uranium into plutonium, to find a way to chemically separate plutonium from uranium, and to design and build atomic bombs. It falls to Compton to decide which of the various types of reactor designs should be pursued by scientists, although successful reactors have not yet been built. He proposed a timetable for achieving a nuclear chain reaction controlled in January 1943, and had an atomic bomb in January 1945.
Development
In nuclear reactors, criticality is achieved when the rate of neutron production equals the level of neutron losses, including neutron absorption and neutron leakage. When the uranium-235 atom undergoes fission, it releases an average of 2.4 neutrons. In the simplest case of a round, homogeneous, spherical, critical radius is calculated approximately:
,
where M is the average distance of neutron travel before being absorbed, and k is the average neutron multiplication factor. The neutrons in a successful reaction will be amplified by the k factor, the second generation of fission events will produce k 2 , the third k 3 and so on. In order for an independent nuclear chain reaction to occur, k must be at least 3 or 4 percent greater than 1. In other words, k must be greater than 1 without crossing the critical critical threshold will result in a rapid and exponential increase in the number of fission events.
Fermi baptized his apparatus as a "pile". Emilio SegrÃÆ'¨ then remember that:
I think for a moment that this term is used to refer to a nuclear energy source in analogy with the use of the Italian term Volta pila to denote its own remarkable discovery of the source of electrical energy. I was disappointed by Fermi himself, who told me that he only used the common English word stack as a synonym with heap . To my surprise, Fermi never seems to think about the relationship between stack and Volta.
Another grant, currently totaling $ 40,000, was obtained from the S-1 Uranium Committee to purchase more materials, and in August 1941 Fermi began planning the construction of sub-critical assemblies to test with smaller structures whether the larger ones would work. The proposed exponential pile is 8 feet (2.4 m) long, 8 feet (2.4 m) wide and 11 feet (3.4 m) tall. It's too big to get into Pupin Physics Laboratories. Fermi remembers that:
We went to Dean Pegram, who was then a magician around the University, and we explained to him that we needed a big room. He lurked around the campus and we went with him to dark corridors and under various heating pipes and so on, to visit possible places for this experiment and finally a large room found at Schermerhorn Hall.
The pile was built in September 1941 of 4-by-12-inch graphite blocks (10 times 10 by 30 cm) and tinplate iron cans of uranium oxide. The can is 8 by 8 inches x 8 inches (20 x 20 x 20 cm). When filled with uranium oxide, each weighed about 60 pounds (27 kg). There are 288 cans in all, and each is surrounded by blocks of graphite so the whole will form a cubic lattice structure. The source of the radium-beryllium neutron is positioned near the bottom. The uranium oxide is heated to remove moisture, and packed into a can while it is hot on a vibrating table. The cans are then soldered closed. For manpower, Pegram secures the services of the Columbia football team. It was a habit at that time for soccer players to do odd jobs around the university. They are able to manipulate heavy cans easily. The end result is a disappointing k of 0.87.
Compton felt that having a team at Columbia University, Princeton University, the University of Chicago and the University of California created too much duplication and insufficient collaboration, and he decided to focus the work in one location. No one wants to move, and everyone argues in favor of their own location. In January 1942, as soon as the United States entered World War II, Compton decided at his own location, the University of Chicago, where he knew he had tremendous support from the university administration. Chicago also has a central location, and scientists, technicians and facilities are more available in the Midwest, where war work has not taken them away. In contrast, Columbia University is involved in uranium enrichment efforts under Harold Urey and John Dunning, and is hesitant to add a third secret project.
Before leaving for Chicago, the Fermi team made one last attempt to build a pile of work at Columbia. Because the cans absorb neutrons, they are released. In contrast, uranium oxide, heated to 250 Â ° C (480 Â ° F) to dry it, is pressed into a 3-inch (7.6 cm) long and 3 inch (7.6 cm) cylindrical hole with diameter drilled to graphite. The entire pile is then canned with soldering sheet metal around it, and the contents are heated above the boiling point of water to remove moisture. The result is k 0.918.
Site selection
In Chicago, Samuel K. Allison has found a suitable location with a length of 60 feet (18 m), 30 feet (9.1 m) wide and 26 feet (7.9 m) tall, sinking slightly below the soil surface, in space under the stand at Stagg Field was originally built as a racket court. Stagg Field was largely unused since the University of Chicago gave up playing American football in 1939, but the courts under the West Stands were still used to play squash and handball. Leona Woods and Anthony L. Turkevich played squash there in 1940. Because it was meant for heavy sports, the area was not heated, and very cold in winter. The nearby North Stands have a pair of ice skating rinks on the ground floor, which although not cooled, rarely melt in the winter. Allison used the racket field area to build a 7 foot (2.1 m) experimental pile before the Fermi group arrived in 1942.
The United States Army Corps of Engineers took over the control of the nuclear weapons program in June 1942, and the Compton Metallurgy Laboratory became part of what was then called the Manhattan Project. Brigadier General Leslie R. Groves, Jr. became director of the Manhattan Project on September 23, 1942. He visited the Metallurgical Laboratory for the first time on 5 October. Between September 15 and November 15, 1942, groups under Herbert Anderson and Walter Zinn built 16 experimental piles under the Stagg Field stands.
Fermi designed a new stack, which would be rounded to maximize k , which is estimated to be around 1.04, thus reaching criticality. Leona Woods was detailed to build a trifluoride neutron detector as soon as he completed his doctoral thesis. He also helped Anderson find the large amount of 4-by-6-inch (10 times 15 cm) wood needed in the woody yard on Chicago's southern side. High-purity graphite shipment arrived, mainly from National Carbon, and high purity uranium dioxide from Mallinckrodt in St. Louis, which now produces 30 short tons (27 tons) per month. Metal uranium also began to arrive in larger quantities, newly developed engineering products.
On June 25, the Army and the Office of Scientific Research and Development (OSRD) have selected a site in the Argonne Forest near Chicago for a plutonium pilot plant. It became known as Site A. 1,025 hectares (415 ha) was rented from Cook County in August, but in September it was clear that the proposed facility would be too wide for the site, and it was decided to build a pilot plant elsewhere. Subcritical stacks pose little danger, but Groves feels that it would be wise to find a critical pile - a fully functioning nuclear reactor - in more remote locations. A building in Argonne to house the Fermi pilot pile begins, with completion scheduled for October 20th. Due to industrial disputes, construction falls behind schedule, and it becomes clear the material for the new pile of Fermi will be in hand before the new structure is completed. In early November, Fermi came to Compton with a proposal to build an experimental pile under the stands at Stagg Field.
The risk of building an operational reactor running in criticality in populated areas is a significant problem, as there is a danger of a nuclear disaster crisis enveloping one of the major urban areas of the United States in radioactive fission products. But system physics suggests that the pile can be safely closed even in the event of an escape reaction. When a fuel atom undergoes fission, it releases a neutron that attacks other fuel atoms in a chain reaction. The time between absorbing neutrons and undergoing fission is measured in nanoseconds. Szilard has noted that this reaction leaves a fission product that can also release neutrons, but does so much longer, from microseconds to minutes. In slow reactions such as those in the pile where fission products are formed, these neutrons account for about three percent of the total neutron flux.
Fermi argues that by using delayed neutrons, and by carefully controlling the rate of reaction when power is thickened, the stack can reach the level of criticality at the fission level slightly below the chain reaction that rely solely on the direct neutrons of the fission reaction. Since the rate of discharge of this neutron depends on the fission events occurring some time before, there is a delay between power spikes and later critical events. This time gives the operator leeway; if the spikes of neutron flux are quickly visible, they have a few minutes before this causes an escape reaction. If a neutron absorber, or a neutron toxin, is injected at any time during this period, the reactor will die. As a result, the reaction can be controlled by an electromechanical control system such as a control rod. Compton feels this delay is enough to provide a critical safety margin, and allows Fermi to build Chicago Pile-1 at Stagg Field.
Compton then explains that:
As a responsible officer at the University of Chicago, in accordance with every organizational protocol rule, I should bring this issue to my boss. But this is not fair. President Hutchins was not in a position to make an independent assessment of the dangers involved. Based on the university's welfare considerations, the only answer he can give is - no. And this answer must be wrong.
Compton told Groves about his decision at the November 14 S-1 Executive Committee meeting. Although Groves "has serious doubts about Compton's advice wisdom", he does not interfere. James B. Conant, chairman of the NDRC, is reported to have turned white. But because of their urgency and confidence in Fermi calculations, no one objected.
Construction
Chicago Pile 1 is wrapped in balloons so the air inside can be replaced with carbon dioxide. Anderson has a dark gray balloon produced by Goodyear Tire and Rubber Company. A 25 feet (7.6 m) cube balloon is a bit unusual, but the AAA priority ranking of the Manhattan Project ensures fast delivery without question. A block and a tackle is used to lift it into place, with the top secured to the ceiling and three sides to the wall. The remaining side, facing the balcony where Fermi directs the operation, is rolled up like a tent. A circle was drawn on the floor, and the stack of graphite blocks began on the morning of 16 November 1942. The first layer was placed entirely made of graphite blocks, without uranium. Layers without uranium alternate with two layers containing uranium, so the uranium is covered in graphite. Unlike subsequent reactors, it does not have a radiation or cooling protection system, as it is only intended to operate at very low power.
The work was done in twelve-hour shifts, with the afternoon shift under Zinn and the night shift under Anderson. For the workforce, they employ three high school dropouts who want to earn a little money before being recruited into the Army. They produce 45,000 blocks of graphite covering 19,000 pieces of uranium metal and uranium oxide. Graphite arrives from the manufacturer at 4.25-by-4.25-inch (10.8 by 10.8 cm) bars with varying lengths. They were cut to a standard length of 16.5 inches (42 cm), each weighing 19 pounds (8.6 kg). A lathe is used to drill a 3.25 inch (8.3 cm) hole in the block for control rods and uranium. Hydraulic presses are used to form uranium oxide into "pseudospheres", cylinders with rounded edges. The drill bit should be sharpened after every 60 holes, which work about an hour. Graphite dust soon filled the air and made the floor slippery.
Another group, under Volney C. Wilson, is responsible for instrumentation. They also fabricate control rods, which are cadmium sheets nailed to flat wood strips, cadmium into powerful neutron absorber, and scram lines, manila ropes that when cut will drop the control rod into the pile and stop the reaction. Richard Fox, who created a control rod mechanism for the stack, said that the manual speed control the operator has over the rod is just a variable resistor, controlling the electric motor that will roll up the clothesline above the pulley which also has two lead weights installed to ensure it will fail- safe and back to zero position when released.
About two layers are placed per shift. Woods neutron neutron trifluoride counters are inserted in the 15th layer. After that, the reading is taken at each end of the shift. Fermi divides the square of the radius of the pile by the intensity of the radioactivity to get the metric counted down as the pile approaches criticality. In the 15th layer, it is 390; at 19 it was 320; on the 25th it is 270 and on the 36th it is only 149. The original design is for the pile of balls, but when the work goes, it becomes clear that this is not necessary. The new graphite is purer, and 6 ton short (5.4 Â °) of highly purified metal uranium is beginning to arrive from the Ames Project at Iowa State University, where the team under Frank Spedding has developed a new process for producing uranium metal. The Westinghouse Lights Factory supplies 3 short tons (2.7 tt), which are produced in a hurry with a transient process.
The 2.25 inch (5.7 cm) uranium metal cylinder, known as "Spedding's eggs", is dropped in holes in graphite instead of uranium oxide pseudospheres. The process of filling the balloon with carbon dioxide is not necessary, and twenty layers can be removed. According to Fermi's new calculations, the countdown will reach 1 between the 56th and 57th layers. Therefore the resulting pile is flatter at the top than at the bottom. Anderson stopped after the 57th layer was placed. When completed, the wooden frame supports elliptical structures, 20 feet (6.1 m) tall, 6 feet (1.8 m) wide at the tip and 25 feet (7.6 m) in the middle. It contains 6 short tons (5.4 t) of uranium metal, 50 short tons (45 t) of uranium oxide and 400 short tons (360 t) of graphite, at an estimated cost of $ 2.7 million.
First nuclear chain reaction
The next day, December 2, 1942, everyone gathered for an experiment. There are 49 scientists present. Although most of the S-1 Executive Committees are in Chicago, only Crawford Greenewalt is present, at the invitation of Compton. Other officials present included Szilard, Wigner and Spedding. Fermi, Compton, Anderson, and Zinn gathered around the controls on the balcony, which was originally intended as a viewing platform. Samuel Allison stands ready with a concentrated cadmium nitride bucket, which he must place on a pile in an emergency. Startup starts at 09:54. Walter Zinn took off his zipper, emergency control rod, and secured it. Norman Hilberry is ready with an ax to cut the scram line, which will allow the zipper to fall under the influence of gravity. While Leona Woods summoned the count of the loud boron trifluoride detector, George Weil, the only one on the floor, pulled all but one control rod. At 10.37 the Fermi ordered Weil to get rid of all but the 13 feet (4.0 m) last control rod. Weil pulls it 6 inches (15 cm) at a time, with measurements taken at each step.
The process was suddenly stopped by the automatic control rod that reentered, because the travel rate was too low. At 11:25, Fermi ordered the control rod to be re-entered. He then announced that it was lunch time.
The experiment continued at 14:00. Weil works on the last control rod while Fermi carefully monitors neutron activity. Fermi announces that the pile has become critical (achieving self-reactions) at 15:25. Fermi alters the scale on the recorder to accommodate the rapidly rising electric current from the boron trifluoride detector. He wanted to test the control circuitry, but after 28 minutes, the alarm bell rang to tell everyone that the neutron flux had passed the prescribed security level, and he ordered Zinn to release the zipper. Quick reaction stopped. The stack has been running for about 4.5 minutes around 0.5 watts. Wigner opened a bottle of Chianti, which they drank from a paper cup.
Compton told Conant over the phone. The conversation was in an impromptu code:
Compton: The Italian navigator has landed in the New World Conant: What about the natives? Compton: Very friendly.
Operation later
On December 12, 1942, the CP-1 power output was increased to 200 W, enough to light a bulb. Lack of any shield, it is a radiation hazard for everyone around it, and further testing is continued at 0.5 W. The operation was discontinued on February 28, 1943, and the stack was unloaded and moved to Site A in the Argonne Forest, now known as the Red Gate Woods. There original material used to build Chicago Pile-2 (CP-2). Instead of being rounded, the new reactor was built in a cubic-shaped, about 25 feet (7.6 m) tall with a base of about 30 feet (9.1 m) square. It is surrounded by a 5-foot (1.5 m) high concrete wall acting as radiation shield, with top protection of 6 inches (15 cm) tin and 50 inches (130 cm) of wood. More uranium is used, thus containing 52 tons of short (47 t) uranium and 472 tons of short (428 t) of graphite. No cooling system is provided as it only runs at several kilowatts. CP-2 commenced operations in March 1943, with k 1.055. During the Zinn war allowed CP-2 to run all the time, and the design was perfect for experimenting. CP-2 joined the Chicago Pile-3, the first heavy water reactor, which became critical on May 15, 1944.
Reactors are used to conduct weapons-related research, such as investigating tritium properties. Wartime experiments included measurements of neutron-absorbing cross section of elements and compounds. Albert Wattenberg recalls that about 10 elements were studied monthly, and 75 for one year. Accidents involving radium and beryllium powder cause a dangerous decrease in the number of white blood cells lasting for three years. As the dangers of things like inhaling uranium oxide become more pronounced, experiments are carried out on the effects of radioactive substances on laboratory test animals.
The Red Gate Woods later became the original site of Argonne National Laboratory, which replaced the Metallurgical Laboratory on July 1, 1946, with Zinn as its first director. CP-2 and CP-3 operated for ten years before they outlived their usefulness, and Zinn ordered them to close on May 15, 1954. The usable fuel was moved to the Chicago Pile-5 at Argonne National Laboratory's new site at DuPage County and CP-2 and CP-3 reactors were dismantled in 1955 and 1956. Several graphite blocks from CP-1/CP-2 were reused in the Reactor Reactor TREAT. High-level nuclear waste such as fuel and heavy water are delivered to Oak Ridge, Tennessee, to be disposed of. The rest is wrapped in concrete and buried in a 40 foot (12 m) trench in what is now known as the Site Disposal Site A/Plot M. This is marked by a memorial stone.
In the 1970s there was an increasing public interest about the level of radioactivity at the site, used by locals for recreational purposes. Surveys conducted in the 1980s found strontium-90 on the ground in Plot M, tracing tritium at a nearby well, and plutonium, technetium, cesium, and uranium in the area. In 1994, the US Department of Energy and Argonne National Laboratory produced public pressure and allocated $ 24.7 million and $ 3.4 million to rehabilitate the site. As part of the cleaning, 500 cubic meters (380 m 3 ) of radioactive waste has been removed and sent to the Hanford Site for disposal. In 2002, the Illinois Department of Public Health has determined that the remaining ingredients do not pose a hazard to public health.
Significance and warning
The CP-1 success test not only proves that the nuclear reactor is feasible, it shows that the k factor is greater than originally anticipated. This removes objections to the use of air or water as a coolant rather than expensive helium. This also means that there is greater latitude in the selection of materials for cooling pipes and control mechanisms. Wigner is now pressing ahead with its design for a water-cooled production plant. There are still concerns about the ability of a moderate-moderated graphite reactor capable of producing plutonium on an industrial scale, and for this reason the Manhattan Project continues the development of heavy water production facilities. An air-cooled reactor, X-10 Graphite Reactor, was built at Clinton Engineer Works in Oak Ridge as part of semi-semi plutonium, followed by larger water-cooled water reactors at Hanford Site in Washington state. Enough plutonium was produced for atomic bombs in July 1945, and for two more in August.
A memorial plaque was inaugurated at Stagg Field on December 2, 1952, as the 10th anniversary of CP-1 became critical. It reads:
On December 2, 1942, man succeeded in reaching the first independent supply chain reaction and thus initiating the release of controlled nuclear energy.
The plaque was saved when the West Stands were destroyed in August 1957. The CP-1 site was designated a National Historic Landmark on February 18, 1965. When the National Register of Historic Places was created in 1966, it was immediately added to the same. The site was also named the Chicago Landmark on October 27, 1971.
Today the old Stagg Field site is housed by the University's Regenstein Library, which opened in 1970, and the Joe and Rika Mansueto Libraries, which opened in 2011. The statue of Henry Moore, Nuclear Energy , stands in a small rectangle outside the Regenstein Library. It was dedicated on December 2, 1967, to commemorate the 25 years CP-1 that will be critical. The memorial plaque from 1952, 1965 and 1967 was nearby. Graphite blocks from CP-1 can be seen at the Bradbury Science Museum in Los Alamos, New Mexico; others are on display at the Museum of Science and Industry in Chicago. On December 2, 2017, the 75th anniversary of the Massachusetts Institute of Technology in restoring a graphite-research stack, similar in design to Chicago Pile-1, was ceremonially inserted a final uranium snail.
Note
References
External links
- Photo CP-1 Library Archives University of Chicago. Includes photos and sketches of CP-1.
- Stagg Field western tribune, Institute of Metal Studies (Metallurgical Laboratory), Enrico Fermi, and active experiments using CP-1
- The First Pile 11 page story about CP-1
- "First Hand Introduction of the First Sustained Chain Reaction". Department of Energy . Retrieved September 23 2015 . Ã, Video of two surviving CP-1 pioneers, Harold Agnew and Warren Nyer.
- The Fermi audio file recounts the reactor's success on its 10th anniversary in 1952
Source of the article : Wikipedia
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