Demon core

The demon core was a 6.2-kilogram (14 lb) subcritical mass of plutonium measuring 89 millimetres (3.5 in) in diameter, which was involved in two criticality accidents, on August 21, 1945 and May 21, 1946. The core was intended for use in a third World War II nuclear bomb, but remained in use for testing after Japan's surrender. It was designed with a small safety margin to ensure a successful explosion of the bomb. The device briefly went supercritical when it was accidentally placed in supercritical configurations during two separate experiments intended to guarantee the core was indeed close to the critical point. The incidents happened at the Los Alamos laboratory in 1945 and 1946, and resulted in the acute radiation poisoning and subsequent deaths of scientists Harry Daghlian and Louis Slotin. After these incidents the spherical plutonium core was referred to as the "demon core".

A re-creation of the experiment involved in the 1945 incident. The sphere of plutonium is surrounded by neutron-reflecting tungsten carbide blocks.

Manufacturing and early history

The demon core (like the second core used in the bombing of Nagasaki) was a solid 6.2-kilogram (14 lb) sphere measuring 89 millimetres (3.5 in) in diameter. It consisted of three parts: two plutonium-gallium hemispheres and a ring, designed to keep neutron flux from "jetting" out of the joined surface between the hemispheres during implosion. The core of the device used in the Trinity nuclear test at the Alamogordo Bombing and Gunnery Range in July did not have such a ring.[1][2]

Louis Slotin & Harry K. Daghlian Jr
The two physicists Harry Daghlian (center left) and Louis Slotin (center right) during the Trinity Test

The refined plutonium was shipped from the Hanford Site in Washington state to the Los Alamos Laboratory; an inventory document dated August 30 shows Los Alamos had expended "HS-1, 2, 3, 4; R-1" (the components of the Trinity and Nagasaki bombs) and had in its possession "HS-5, 6; R-2", finished and in the hands of quality control. Material for "HS-7, R-3" was in the Los Alamos metallurgy section, and would also be ready by September 5 (it is not certain whether this date allowed for the unmentioned "HS-8"'s fabrication to complete the fourth core).[3] The metallurgists used a plutonium-gallium alloy, which stabilized the δ phase allotrope of plutonium so it could be hot pressed into the desired spherical shape. As plutonium was found to corrode readily, the sphere was then coated with nickel.[4]

On August 10, Major General Leslie R. Groves, Jr., wrote to General of the Army George C. Marshall, the Chief of Staff of the United States Army, to inform him that:

The next bomb of the implosion type had been scheduled to be ready for delivery on the target on the first good weather after August 24th, 1945. We have gained 4 days in manufacture and expect to ship the final components from New Mexico on August 12th or 13th. Providing there are no unforeseen difficulties in manufacture, in transportation to the theatre or after arrival in the theatre, the bomb should be ready for delivery on the first suitable weather after August 17th or 18th.[3]

Marshall added an annotation, "It is not to be released on Japan without express authority from the President", as President Harry S. Truman was waiting to see the effects of the first two attacks.[3] On August 13, the third bomb was scheduled. It was anticipated that it would be ready by August 16 to be dropped on August 19.[3] This was pre-empted by Japan's surrender on August 15, 1945, while preparations were still being made for it to be couriered to Kirtland Field. The third core remained at Los Alamos.[5]

First incident

The core, assembled, was designed to be at "−5 cents", or 5 percent below critical mass.[6] In this state there is only a small safety margin against extraneous factors that might increase criticality, causing the core to become supercritical, and then prompt critical, a brief state of rapid energy increase.[7] These factors are not common in the environment; they are circumstances like the compression of the solid metallic core – which would eventually be the method used to explode the bomb – the addition of more nuclear material, or provision of an external reflector which would reflect outbound neutrons back into the core. The experiments conducted at Los Alamos leading to the two fatal accidents were designed to guarantee that the core was indeed close to the critical point by arranging such reflectors and seeing how much neutron reflection was required to approach supercriticality.[6]

On August 21, 1945, the plutonium core produced a burst of neutron radiation that led to physicist Harry Daghlian's death. Daghlian made a mistake while performing neutron reflector experiments on the core. He was working alone; a security guard, Private Robert J. Hemmerly, was seated at a desk 10 to 12 feet (3 to 4 m) away.[8] The core was placed within a stack of neutron-reflective tungsten carbide bricks and the addition of each brick moved the assembly closer to criticality. While attempting to stack another brick around the assembly, Daghlian accidentally dropped it onto the core and thereby caused the core to go well into supercriticality, a self-sustaining critical chain reaction. He quickly moved the brick off the assembly, but received a fatal dose of radiation. He died 25 days later from acute radiation poisoning.[9]

Name Origin Age at accident Profession Dose[8] Aftermath Reference
Haroutune "Harry" Krikor Daghlian, Jr. New London, Connecticut 24 Physicist 200 rad (2.0 Gy) neutron
110 rad (1.1 Gy) gamma
Died 25 days after the accident of acute radiation syndrome, haematopoietic focus [10]
Private Robert J. Hemmerly Whitehall, Ohio 29 Special Engineering Detachment (SED) guard 8 rad (0.080 Gy) neutron
0.1 rad (0.0010 Gy) gamma
Died in 1978 (33 years after accident) of acute myelogenous leukemia at the age of 62 [10]

Second incident

Tickling the Dragons Tail
A re-creation of the 1946 experiment. The half-sphere is seen, but the core inside is not. The beryllium hemisphere is held up with a screwdriver.
The demon core

On May 21, 1946,[11] physicist Louis Slotin and seven other Los Alamos personnel were in a Los Alamos laboratory conducting another experiment to verify the closeness of the core to criticality by the positioning of neutron reflectors. Slotin, who was leaving Los Alamos, was showing the technique to Alvin C. Graves, who would use it in a final test before the Operation Crossroads nuclear tests scheduled a month later at Bikini Atoll. It required the operator to place two half-spheres of beryllium (a neutron reflector) around the core to be tested and manually lower the top reflector over the core using a thumb hole on the top. As the reflectors were manually moved closer and farther away from each other, scintillation counters measured the relative activity from the core. The experimenter needed to maintain a slight separation between the reflector halves in order to stay below criticality. The standard protocol was to use shims between the halves, as allowing them to close completely could result in the instantaneous formation of a critical mass and a lethal power excursion. Under Slotin's own unapproved protocol, the shims were not used and the only thing preventing the closure was the blade of a standard straight screwdriver manipulated in Slotin's other hand. Slotin, who was given to bravado, became the local expert, performing the test on almost a dozen occasions, often in his trademark blue jeans and cowboy boots, in front of a roomful of observers. Enrico Fermi reportedly told Slotin and others they would be "dead within a year" if they continued performing the test in that manner.[12] Scientists referred to this flirting with the possibility of a nuclear chain reaction as "tickling the dragon's tail", based on a remark by physicist Richard Feynman, who compared the experiments to "tickling the tail of a sleeping dragon".[13][14]

On the day of the accident, Slotin's screwdriver slipped outward a fraction of an inch while he was lowering the top reflector, allowing the reflector to fall into place around the core. Instantly there was a flash of blue light and a wave of heat across Slotin's skin; the core had become supercritical, releasing an intense burst of neutron radiation estimated to have lasted about a half second.[6] Slotin quickly twisted his wrist, flipping the top shell to the floor. The heating of the core and shells stopped the criticality within seconds of its initiation,[15] while Slotin's reaction prevented a recurrence and ended the accident. The position of Slotin's body over the apparatus also shielded the others from much of the neutron radiation, but he received a lethal dose of 1,000 rad (10 Gy) neutron and 114 rad (1.14 Gy) gamma radiation in under a second and died nine days later from acute radiation poisoning. The nearest person to Slotin, Graves, who was watching over Slotin's shoulder and was thus partially shielded by him, received a high but non-lethal radiation dose. Graves was hospitalized for several weeks with severe radiation poisoning and developed chronic neurological and vision problems as a result of the exposure.[8] He died 20 years later, at age 55, of a heart attack. It may have been caused by hidden complications from radiation exposure, but could also have been genetic in nature, as his father had died from the same cause.[16][17][18]

The second accident was reported by the Associated Press on 26 May 1946: "Four men injured through accidental exposure to radiation in the government's atomic laboratory here [Los Alamos] have been discharged from the hospital and 'immediate condition' of four others is satisfactory, the Army reported today. Dr. Norris E. Bradbury, project director, said the men were injured last Tuesday in what he described as an experiment with fissionable material."[19]

Results of subsequent studies

There have been five studies performed regarding the amount of radiation each person involved received in the accident; these are the latest, dated 1978, from a table in this reference:

Name Origin Age at accident Profession Dose[8] Aftermath
Louis Alexander Slotin Winnipeg, Manitoba, Canada 35 physicist 1,000 rad (10 Gy) neutron
114 rad (1.14 Gy) gamma
died 9 days after the accident of acute radiation syndrome, gastrointestinal focus [11]
Alvin C. Graves Austin, Texas 34 physicist 166 rad (1.66 Gy) neutron
26 rad (0.26 Gy) gamma
died in 1965 (19 years after the accident) of myocardial infarction, with aggravating "compensated myxedema and cataracts", while skiing [8]
Samuel Allan Kline Chicago, Illinois physics student, later patent attorney died in 2001 (55 years after the accident); refused to take part in studies [8]
Marion Edward Cieslicki Mt. Lebanon, Pennsylvania 23 physicist 12 rad (0.12 Gy) neutron
4 rad (0.040 Gy) gamma
died of acute myelocytic leukemia in 1965 (19 years after the accident) [8]
Dwight Smith Young Chicago, Illinois 54 photographer 51 rad (0.51 Gy) neutron
11 rad (0.11 Gy) gamma
died of aplastic anemia and bacterial endocarditis in 1975 (29 years after the accident) [8]
Raemer Edgar Schreiber McMinnville, Oregon 36 physicist 9 rad (0.090 Gy) neutron
3 rad (0.030 Gy) gamma
died of natural causes in 1998 (52 years after the accident), at the age of 88 [8][15]
Theodore Perlman Louisiana 23 engineer 7 rad (0.070 Gy) neutron
2 rad (0.020 Gy) gamma
"alive and in good health and spirits" as of 1978; probably died in June 1988 (42 years after the accident), in Livermore, California[20] [8]
Private Patrick Joseph Cleary New York City 21 security guard 33 rad (0.33 Gy) neutron
9 rad (0.090 Gy) gamma
Sergeant 1st Class Cleary was KIA on 3 Sep 1950 while fighting with the 8th Cavalry Regiment, US Army in the Korean War.[21] [8]

Two machinists, Paul Long and another, unidentified, in another part of the building, 20 to 25 feet away, were not treated.[22]

After these incidents the core, originally known as "Rufus", was referred to as the "demon core".[3][23] Hands-on criticality experiments were stopped, and remote-control machines and TV cameras were designed by Schreiber, one of the survivors, to perform such experiments with all personnel at a quarter-mile distance.[15]

Operation Crossroads

The demon core was intended to be used in the Operation Crossroads nuclear tests, but after the criticality accident, time was needed for its radioactivity to decline and for it to be re-evaluated for the effects of the fission products it held, some of which could be very poisonous to the desired level of fission. The next two cores were shipped for use in Able and Baker, and the demon core was scheduled to be shipped later for the third test of the series, provisionally named Charlie, but that test was cancelled due to the unexpected level of radioactivity resulting from the underwater Baker test and the inability to decontaminate the target warships. The core was later melted down and the material recycled for use in other cores.[23][24]


  1. ^ Wellerstein, Alex. "You don't know Fat Man". Restricted data blog. Archived from the original on April 7, 2014. Retrieved April 4, 2014.
  2. ^ Coster-Mullen, John (2010). Core Differences, from "Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man". Archived from the original on April 27, 2014. Retrieved April 4, 2014. An error: the illustration caption states the Fat Man core was plated in silver; it was plated in nickel, as the silver plating on the gadget core blistered. The disk in the drawings is a gold foil gasket.
  3. ^ a b c d e Wellerstein, Alex. "The Third Core's Revenge". Restricted data blog. Archived from the original on April 7, 2014. Retrieved April 4, 2014.
  4. ^ Baker, Richard D.; Hecker, Siegfried S.; Harbur, Delbert R. (1983). Plutonium: A Wartime Nightmare but a Metallurgist's Dream (PDF). Los Alamos Science. Los Alamos National Laboratory. pp. 142–151. Archived (PDF) from the original on 17 October 2011. Retrieved 22 November 2010.
  5. ^ Shreiber, Raemer; Rhodes, Richard (1993). "Raemer Schreiber's Interview". Archived from the original on April 29, 2015. Retrieved May 28, 2015. Raemer Schreiber being interviewed by Richard Rhodes
  6. ^ a b c McLaughlin, Thomas P.; Monahan, Shean P.; Pruvost, Norman L.; Frolov, Vladimir V.; Ryazanov, Boris G.; Sviridov, Victor I. (May 2000). "A review of criticality incidents, 2000 Revision (LA-13638)" (PDF): 70–78. Archived (PDF) from the original on July 22, 2014. Retrieved May 18, 2014.
  7. ^ Stater, Robert G. (December 13, 2012). "Prompt Criticality: A Concept with False Credentials". Nuke Facts. Archived from the original on March 4, 2016. Retrieved September 27, 2015.
  8. ^ a b c d e f g h i j k Hempelman, Louis Henry; Lushbaugh, Clarence C.; Voelz, George L. (October 19, 1979). What Has Happened to the Survivors of the Early Los Alamos Nuclear Accidents? (PDF). Conference for Radiation Accident Preparedness. Oak Ridge: Los Alamos Scientific Laboratory. LA-UR-79-2802. Archived (PDF) from the original on September 12, 2014. Retrieved January 5, 2013. Patient numbers in this document have been identified as: 1 - Daghlian, 2 - Hemmerly, 3 - Slotin, 4 - Graves, 5 - Kline, 6 - Young, 7 - Cleary, 8 - Cieleski, 9 - Schreiber, 10 - Perlman
  9. ^ Miller, Richard L. (1991). Under the Cloud: The Decades of Nuclear Testing. The Woodlands, Texas: Two Sixty Press. pp. 68, 77. ISBN 0-02-921620-6.
  10. ^ a b Dion, Arnold. "Acute Radiation Sickness". Tripod. Retrieved August 12, 2015.
  11. ^ a b "A Review of Criticality Accidents" (PDF). Los Alamos Scientific Laboratory. September 26, 1967. Archived (PDF) from the original on September 10, 2012. Retrieved August 12, 2015.
  12. ^ Welsome, Eileen (1999). The Plutonium Files (PDF). New York: Dial Press. p. 184. ISBN 978-0-385-31402-2. Archived (PDF) from the original on September 27, 2013. Retrieved November 18, 2012.
  13. ^ Weber, Bruce (10 April 2001). "Theater Review; A Scientist's Tragic Hubris Attains Critical Mass Onstage". New York Times. Retrieved 12 November 2007.
  14. ^ Shepherd-Barr, Kirsten; Lustig, Harry (November–December 2002). "Science as Theater: The Slip of the Screwdriver". American Scientist. Sigma Xi. 90 (6): 550–555. Bibcode:2002AmSci..90..550S. doi:10.1511/2002.6.550.
  15. ^ a b c Calloway, Larry (July 1995). "Nuclear Naiveté" (PDF). Albuquerque Journal. Archived (PDF) from the original on August 16, 2015. Retrieved August 12, 2015.
  16. ^ Clifford T. Honicker (November 19, 1989). "America's Radiation Victims: The Hidden Files". New York Times. p. 11. Archived from the original on August 31, 2016.
  17. ^ Alsop, Stewart; Robert E. Lapp (March 6, 1954). "The Strange Death of Louis Slotin" (PDF). Saturday Evening Post. 226 (36). pp. 25ff. Archived from the original (PDF) on October 17, 2014. Retrieved April 3, 2014.
  18. ^ Clifford T. Honicker (November 19, 1989). "America's Radiation Victims: The Hidden Files". The New York Times. Archived from the original on February 17, 2012. Retrieved April 23, 2011.
  19. ^ Associated Press, "Several at Atomic Bomb Laboratory Injured", The San Bernardino Daily Sun, San Bernardino, California, Monday 27 May 1946, Volume 52, page 1.
  20. ^ State of California. California Death Index, 1940-1997. Sacramento, CA, USA: State of California Department of Health Services, Center for Health Statistics.
  21. ^ American Battle Monuments Commission. Korean War Listing.
  22. ^ "Louis Slotin". Archived from the original on April 7, 2014. Retrieved April 4, 2014.
  23. ^ a b Wellerstein, Alex (May 21, 2016). "The Demon Core and the Strange Death of Louis Slotin". The New Yorker. Archived from the original on May 24, 2016. Retrieved May 22, 2016.
  24. ^ Wellerstein, Alex (May 23, 2016). "The blue flash". Restricted Data. Archived from the original on 24 May 2016. Retrieved 23 May 2016.
1000 Ways to Die

1000 Ways to Die was an anthology television series that premiered on Spike (now Paramount Network) on May 14, 2008, and ended on July 15, 2012. The program recreates unusual supposed deaths, debunked urban legends, and includes interviews with experts who describe the science behind each death. Up until the end of season one, the final story of each episode showed actual footage of dangerous situations that almost ended in death, along with interviews of those involved in the situations. A portion of these deaths have been nominated for or have received a Darwin Award. Ron Perlman served as the narrator on every episode since the third episode (with Thom Beers narrating the first two episodes); beginning with the episode "Tweets from the Dead" Joe Irwin was featured as the replacement narrator.Spike burned off the final four episodes, ending the series with the airing of "Death, The Final Frontier". The show was cancelled after the producers and stars of the show ran a strike against the network.

August 21

August 21 is the 233rd day of the year (234th in leap years) in the Gregorian calendar. There are 132 days remaining until the end of the year.

Cedar Grove Cemetery (New London, Connecticut)

The Cedar Grove Cemetery is a non-sectarian cemetery in New London, Connecticut. It was established in the mid-19th century and is located at the intersection of Broad Street and Jefferson Avenue.

Critical mass

A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties (specifically, the nuclear fission cross-section), its density, its shape, its enrichment, its purity, its temperature, and its surroundings. The concept is important in nuclear weapon design.

Criticality accident

A criticality accident is an uncontrolled nuclear fission chain reaction. It is sometimes referred to as a critical excursion, a critical power excursion or a divergent chain reaction.

Any such event involves the unintended accumulation or arrangement of a critical mass of fissile material, for example enriched uranium or plutonium. Criticality accidents can release potentially fatal radiation doses, if they occur in an unprotected environment.

Under normal circumstances, a critical or supercritical fission reaction (one that is self-sustaining in power or increasing in power) should only occur inside a safely shielded location, such as a reactor core or a suitable test environment. A criticality accident occurs if the same reaction is achieved unintentionally, for example in an unsafe environment or during reactor maintenance.

Though dangerous and frequently lethal to humans within the immediate area, the critical mass formed would not be capable of producing a massive nuclear detonation of the type that fission bombs are designed to produce. This is because all the design features needed to make a nuclear warhead cannot arise by chance.

In some cases, the heat released by the chain reaction will cause the fissile (and other nearby) materials to expand. In such cases, the chain reaction can either settle into a low power steady state or may even become either temporarily or permanently shut down (subcritical).

In the history of atomic power development, at least 60 criticality accidents have occurred, including 22 in process environments, outside nuclear reactor cores or experimental assemblies, and 38 in small experimental reactors and other test assemblies.

Although process accidents occurring outside reactors are characterized by large releases of radiation, the releases are localized. Nonetheless, fatal radiation exposures have occurred to persons close to these events, resulting in 14 fatalities. In a few reactor and critical experiment assembly accidents, the energy released has caused significant mechanical damage or steam explosions.

Fat Man and Little Boy

Fat Man and Little Boy (a.k.a. Shadow Makers in the UK) is a 1989 film that reenacts the Manhattan Project, the secret Allied endeavor to develop the first nuclear weapons during World War II. The film is named after the weapons "Little Boy" and "Fat Man" that were detonated over Hiroshima and Nagasaki, respectively.

The film was directed by Roland Joffé and written by Joffe and Bruce Robinson.

Harry Daghlian

Haroutune Krikor "Harry" Daghlian Jr. (May 4, 1921 – September 15, 1945) was a physicist with the Manhattan Project which designed and produced the atomic bombs that were used in World War II. He accidentally irradiated himself on August 21, 1945, during a critical mass experiment at the remote Omega Site of the Los Alamos Laboratory in New Mexico, resulting in his death 25 days later.

Daghlian was irradiated as a result of a criticality accident that occurred when he accidentally dropped a tungsten carbide brick onto a 6.2 kg plutonium–gallium alloy bomb core. This core, subsequently nicknamed the "demon core", was later involved in the death of another physicist, Louis Slotin.

History of the anti-nuclear movement

The application of nuclear technology, both as a source of energy and as an instrument of war, has been controversial.Scientists and diplomats have debated nuclear weapons policy since before the atomic bombing of Hiroshima in 1945. The public became concerned about nuclear weapons testing from about 1954, following extensive nuclear testing in the Pacific. In 1961, at the height of the Cold War, about 50,000 women brought together by Women Strike for Peace marched in 60 cities in the United States to demonstrate against nuclear weapons. In 1963, many countries ratified the Partial Test Ban Treaty which prohibited atmospheric nuclear testing.Some local opposition to nuclear power emerged in the early 1960s, and in the late 1960s some members of the scientific community began to express their concerns. In the early 1970s, there were large protests about a proposed nuclear power plant in Wyhl, Germany. The project was cancelled in 1975 and anti-nuclear success at Wyhl inspired opposition to nuclear power in other parts of Europe and North America. Nuclear power became an issue of major public protest in the 1970s.

Infest (band)

Infest is an American hardcore punk band, formed in September 1986 by Joe Denunzio, Matt Domino, Dave Ring and Chris Clift. The band is considered to be pioneers of the dissonant hardcore style known as powerviolence. The term was coined by their guitarist Matt Domino, who first used it to describe his other band, Neanderthal with Eric Wood of Man is the Bastard. The Los Angeles quartet blended the ethos, speed and song structure of straight edge hardcore, along with the aggression and anger of bands like Negative Approach and Negative FX. Joe Denunzio’s vocals exhibited raw anger, with lyrical content about conformity, war, scene politics and socio-political issues. Infest did however differ from their peers in their fervent political stance and imagery, often depicting the tragedies of war and poverty, countering the obligatory "band in action" album covers common to the era. The group broke up in 1996, having played only a handful of shows within California.On July 1, 1991, Infest recorded a live set for the Los Angeles radio station KXLU. This session was later released by Deep Six Records who also released the No Man's Slave LP in 2002. Instrumentals for the record were recorded during the summer of 1995, and vocals were recorded post-breakup in 2000.

On January 13, 2013, Infest played their first show since 1991 at The Echo, in Echo Park, California with bands such as ACxDC (Anti-Christ Demon Core), Barking Backwards, Fissure and Sordo. They were among the headliners at the 2013 editions of Maryland Deathfest and Chaos in Tejas respectively. In July 2013 Infest headlined the Destroy L.A. Hardcore Festival with California youth crew legends Chain of Strength. In July 2014, they headlined a one-off in Dallas, Texas at Vice Palace, along with Chicago-based outfit Weekend Nachos. The band has been performing frequently ever since, making their European debut at Netherlands Deathfest 2016.

Louis Slotin

Louis Alexander Slotin (1 December 1910 – 30 May 1946) was a Canadian physicist and chemist who took part in the Manhattan Project. He was born and raised in the North End of Winnipeg, Manitoba. After earning both his Bachelor of Science and Master of Science degrees from the University of Manitoba, Slotin attended King's College London, where he obtained his doctorate in physical chemistry in 1936. Afterwards, he joined the University of Chicago as a research associate to help design a cyclotron. In 1942, he was invited to participate in the Manhattan Project.

As part of the Manhattan Project, Slotin performed experiments with uranium and plutonium cores to determine their critical mass values. After World War II, Slotin continued his research at Los Alamos National Laboratory. On May 21, 1946, Slotin accidentally began a fission reaction, which released a burst of hard radiation. Slotin was rushed to the hospital, and died nine days later on May 30, the victim of the second criticality accident in history, following the death of Harry Daghlian, who had been exposed to radiation by the same core that killed Slotin.

Slotin was hailed as a hero by the United States government for reacting quickly enough to prevent the deaths of his colleagues. However, some physicists argue that this was a preventable accident. The accident and its aftermath have been dramatized in several fictional and non-fiction accounts.

Manhattan Project

The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the U.S. Army Corps of Engineers. Nuclear physicist Robert Oppenheimer was the director of the Los Alamos Laboratory that designed the actual bombs. The Army component of the project was designated the Manhattan District; Manhattan gradually superseded the official codename, Development of Substitute Materials, for the entire project. Along the way, the project absorbed its earlier British counterpart, Tube Alloys. The Manhattan Project began modestly in 1939, but grew to employ more than 130,000 people and cost nearly US$2 billion (about $22 billion in 2016 dollars). Over 90% of the cost was for building factories and to produce fissile material, with less than 10% for development and production of the weapons. Research and production took place at more than 30 sites across the United States, the United Kingdom, and Canada.

Two types of atomic bombs were developed concurrently during the war: a relatively simple gun-type fission weapon and a more complex implosion-type nuclear weapon. The Thin Man gun-type design proved impractical to use with plutonium, and therefore a simpler gun-type called Little Boy was developed that used uranium-235, an isotope that makes up only 0.7 percent of natural uranium. Chemically identical to the most common isotope, uranium-238, and with almost the same mass, it proved difficult to separate the two. Three methods were employed for uranium enrichment: electromagnetic, gaseous and thermal. Most of this work was performed at the Clinton Engineer Works at Oak Ridge, Tennessee.

In parallel with the work on uranium was an effort to produce plutonium. After the feasibility of the world's first artificial nuclear reactor was demonstrated in Chicago at the Metallurgical Laboratory, it designed the X-10 Graphite Reactor at Oak Ridge and the production reactors in Hanford, Washington, in which uranium was irradiated and transmuted into plutonium. The plutonium was then chemically separated from the uranium, using the bismuth phosphate process. The Fat Man plutonium implosion-type weapon was developed in a concerted design and development effort by the Los Alamos Laboratory.

The project was also charged with gathering intelligence on the German nuclear weapon project. Through Operation Alsos, Manhattan Project personnel served in Europe, sometimes behind enemy lines, where they gathered nuclear materials and documents, and rounded up German scientists. Despite the Manhattan Project's tight security, Soviet atomic spies successfully penetrated the program.

The first nuclear device ever detonated was an implosion-type bomb at the Trinity test, conducted at New Mexico's Alamogordo Bombing and Gunnery Range on 16 July 1945. Little Boy and Fat Man bombs were used a month later in the atomic bombings of Hiroshima and Nagasaki, respectively. In the immediate postwar years, the Manhattan Project conducted weapons testing at Bikini Atoll as part of Operation Crossroads, developed new weapons, promoted the development of the network of national laboratories, supported medical research into radiology and laid the foundations for the nuclear navy. It maintained control over American atomic weapons research and production until the formation of the United States Atomic Energy Commission in January 1947.

May 21

May 21 is the 141st day of the year (142nd in leap years) in the Gregorian calendar. There are 224 days remaining until the end of the year.

Neutron reflector

A neutron reflector is any material that reflects neutrons. This refers to elastic scattering rather than to a specular reflection. The material may be graphite, beryllium, steel, tungsten carbide, or other materials. A neutron reflector can make an otherwise subcritical mass of fissile material critical, or increase the amount of nuclear fission that a critical or supercritical mass will undergo. Such an effect was exhibited twice in accidents involving the Demon Core, a subcritical plutonium pit that went critical in two separate fatal incidents when the pit's surface was momentarily surrounded by too much neutron reflective material.

Nuclear history of the United States

Nuclear history of the United States describes the history of nuclear affairs in the United States whether civilian or military.

Nuclear weapon

A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or from a combination of fission and fusion reactions (thermonuclear bomb). Both bomb types release large quantities of energy from relatively small amounts of matter. The first test of a fission ("atomic") bomb released an amount of energy approximately equal to 20,000 tons of TNT (84 TJ). The first thermonuclear ("hydrogen") bomb test released energy approximately equal to 10 million tons of TNT (42 PJ). A thermonuclear weapon weighing little more than 2,400 pounds (1,100 kg) can release energy equal to more than 1.2 million tons of TNT (5.0 PJ). A nuclear device no larger than traditional bombs can devastate an entire city by blast, fire, and radiation. Since they are weapons of mass destruction, the proliferation of nuclear weapons is a focus of international relations policy.

Nuclear weapons have been used twice in war, both times by the United States against Japan near the end of World War II. On August 6, 1945, the U.S. Army Air Forces detonated a uranium gun-type fission bomb nicknamed "Little Boy" over the Japanese city of Hiroshima; three days later, on August 9, the U.S. Army Air Forces detonated a plutonium implosion-type fission bomb nicknamed "Fat Man" over the Japanese city of Nagasaki. These bombings caused injuries that resulted in the deaths of approximately 200,000 civilians and military personnel. The ethics of these bombings and their role in Japan's surrender are subjects of debate.

Since the atomic bombings of Hiroshima and Nagasaki, nuclear weapons have been detonated over two thousand times for testing and demonstration. Only a few nations possess such weapons or are suspected of seeking them. The only countries known to have detonated nuclear weapons—and acknowledge possessing them—are (chronologically by date of first test) the United States, the Soviet Union (succeeded as a nuclear power by Russia), the United Kingdom, France, China, India, Pakistan, and North Korea. Israel is believed to possess nuclear weapons, though, in a policy of deliberate ambiguity, it does not acknowledge having them. Germany, Italy, Turkey, Belgium and the Netherlands are nuclear weapons sharing states. South Africa is the only country to have independently developed and then renounced and dismantled its nuclear weapons.The Treaty on the Non-Proliferation of Nuclear Weapons aims to reduce the spread of nuclear weapons, but its effectiveness has been questioned, and political tensions remained high in the 1970s and 1980s. Modernisation of weapons continues to this day.

Operation Ranger

Operation Ranger was the fourth American nuclear test series. It was conducted in 1951 and was the first series to be carried out at the Nevada Test Site.

All the bombs were dropped by B-50D bombers and exploded in the open air over Frenchman Flat (Area 5).

These tests centered on the practicality of developing a second generation of nuclear weapons using smaller amounts of valuable nuclear materials. They were planned under the name Operation Faust.

The exact locations of the tests are unknown, as they were all air drops. However, the planned ground zero was set at 36°49′32″N 115°57′54″W for all except the Fox shot, which was "500 feet west and 300 feet south" in order to minimize damage to the control point.

Raemer Schreiber

Raemer Edgar Schreiber (November 11, 1910 – December 24, 1998) was an American physicist from McMinnville, Oregon who served Los Alamos National Laboratory during World War II, participating in the development of the atomic bomb. He saw the first one detonated in the Trinity nuclear test in July 1945, and prepared the Fat Man bomb that was used in the bombing of Nagasaki. After the war, he served at Los Alamos as a group leader, and was involved in the design of the hydrogen bomb. In 1955, he became the head of its Nuclear Rocket Propulsion (N) Division, which developed the first nuclear-powered rockets. He served as deputy director of the laboratory from 1972 until his retirement in 1974.

The Laws of Inferno Dynamics

"The Laws of Inferno Dynamics" is the eighth episode and mid-season finale of the fourth season of the American television series Agents of S.H.I.E.L.D., based on the Marvel Comics organization S.H.I.E.L.D. (Strategic Homeland Intervention, Enforcement, and Logistics Division), revolving around the character of Phil Coulson and his team of S.H.I.E.L.D. agents as they work with the Ghost Rider to defeat Eli Morrow. It is set in the Marvel Cinematic Universe (MCU), sharing continuity with the films of the franchise. The episode was written by Paul Zbyszewski, and directed by Kevin Tancharoen.

Clark Gregg reprises his role as Coulson from the film series, and is joined by series regulars Ming-Na Wen, Chloe Bennet, Iain De Caestecker, Elizabeth Henstridge, Henry Simmons, and John Hannah. Recurring guest stars Gabriel Luna and José Zúñiga portray the Ghost Rider, Robbie Reyes, and his uncle Morrow, respectively. The episode serves as the last in the first "pod" of episodes for the season, subtitled Ghost Rider.

"The Laws of Inferno Dynamics" originally aired on ABC on December 6, 2016, and according to Nielsen Media Research, was watched by 4.49 million viewers within a week of its release.

Tungsten carbide

Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into shapes through a process called sintering for use in industrial machinery, cutting tools, abrasives, armor-piercing rounds, other tools and instruments, and jewelry.

Tungsten carbide is approximately twice as stiff as steel, with a Young's modulus of approximately 530–700 GPa (77,000 to 102,000 ksi), and is double the density of steel—nearly midway between that of lead and gold. It is comparable with corundum (α-Al2O3) in hardness and can only be polished and finished with abrasives of superior hardness such as cubic boron nitride and diamond powder, wheels, and compounds.

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