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 fatal radiation doses, if they occur in an unprotected environment. Under normal circumstances, a critical or supercritical fission reaction 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 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. In some cases, the heat released by the chain reaction will cause the fissile materials to expand.
In such cases, the chain reaction can either settle into a low power steady state or may become either temporarily or permanently shut down. 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, 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. Criticality occurs when sufficient fissile material accumulates in a small volume such that each fission, on average, produces a neutron that in turn strikes another fissile atom causing another fission. Criticality can be achieved by using metallic uranium or plutonium, liquid solutions or powder slurries.
The chain reaction is influenced by range of parameters noted by the acronyms MAGIC MERV and MERMAIDS. Temperature can be a key factor. Calculations can be performed to determine the conditions needed for a critical state, geometry, concentration etc. Where fissile materials are handled in civil and military installations, specially trained personnel are employed to carry out such calculations, to ensure that all reasonably practicable measures are used to prevent criticality accidents, during both planned normal operations and any potential process upset conditions that cannot be dismissed on the basis of negligible likelihoods; the assembly of a critical mass establishes a nuclear chain reaction, resulting in an exponential rate of change in the neutron population over space and time leading to an increase in neutron flux. This increased flux and attendent fission rate produces radiation that contains both a neutron and gamma ray component and is dangerous to any unprotected nearby life-form.
The rate of change of neutron population depends on the neutron generation time, characteristic of the neutron population, the state of "criticality", the fissile medium. A nuclear fission creates 2.5 neutrons per fission event on average. Hence, to maintain a stable critical chain reaction, 1.5 neutrons per fission event must either leak from the system or be absorbed without causing further fissions. For every 1000 neutrons released by fission, a small number no more than about 7, are delayed neutrons which are emitted from the fission product precursors, called delayed neutron emitters; this delayed neutron fraction, on the order of 0.007 for uranium, is crucial for the control of the neutron chain reaction in reactors. It is called one dollar of reactivity; the lifetime of delayed neutrons ranges from fractions of seconds to 100 seconds after fission. The neutrons are classified in 6 delayed neutron groups; the average neutron lifetime considering delayed neutrons is 0.1 sec, which makes the chain reaction easy to control over time.
The remaining 993 prompt neutrons are released quickly 1 μs after the fission event. In steady state operation, nuclear reactors operate at exact criticality; when at least one dollar of reactivity is added above the exact critical point the chain reaction does not rely on delayed neutrons. In such cases, the neutron population can increase exponentially, with a small time constant, known as the prompt neutron lifetime, thus there is a large increase in neutron population over a short time frame. Since each fission event contributes 200 MeV per fission, this results in a large energy burst as a "prompt critical spike"; this spike can be detected by radiation dosimetry instrumentation and "criticality accident alarm system" detectors that are properly deployed. Criticality accidents are divided into one of two categories: Process accidents, where controls in place to prevent any criticality are breached
National Film Registry
The National Film Registry is the United States National Film Preservation Board's selection of films deserving of preservation. The NFPB, established by the National Film Preservation Act of 1988, was reauthorized by acts of Congress in 1992, 1996, 2005, again in October 2008; the NFPB's mission, to which the NFR contributes, is to ensure the survival and increased public availability of America's film heritage. The 1996 law created the non-profit National Film Preservation Foundation which, although affiliated with the NFPB, raises money from the private sector; the NFPB adds to the NFR up to 25 "culturally or aesthetically significant films" each year, showcasing the range and diversity of American film heritage to increase awareness for its preservation. A film becomes eligible for inclusion ten years after its original release. For the first selection in 1989, the public nominated 1,000 films for consideration. Members of the NFPB developed individual ballots of possible films for inclusion.
The ballots were tabulated into a list of 25 films, modified by Librarian of Congress James H. Billington and his staff at the Library for the final selection. Since 1997, members of the public have been able to nominate up to 50 films a year for the NFPB and Librarian to consider; the NFR includes films ranging from Hollywood classics to orphan films. A film is not required to be feature-length, nor is it required to have been theatrically released in the traditional sense. In addition, television programs and foreign films are not excluded from consideration, although American films are given preference; the Registry contains newsreels, silent films, student films, experimental films, short films, music videos, films out of copyright protection or in the public domain, film serials, home movies, documentaries and independent films. As of the 2018 listing, there are 750 films in the Registry; the earliest listed film is Newark Athlete, the most recent is Brokeback Mountain. Counting the 11 multi-year serials in the NFR once each by year of completion, the year with the most films selected is 1939, with 19 films from that year chosen.
The time between a film's debut and its selection varies greatly. The longest span is 121 years; the shortest span is the minimum 10 years. This table is through the 2018 induction list. For purposes of this list, multi-year serials are counted only once by year of completion. Category:United States National Film Registry films National Recording Registry These Amazing Shadows, a 2011 documentary film that tells the history and importance of the registry National Film Registry homepage Classic Movie Hub: National Film Registry List These Amazing Shadows site for Independent Lens on PBS
Victor Saville was an English film director and screenwriter. He directed 39 films between 1927 and 1954, he produced 36 films between 1923 and 1962. He produced his first film, Woman to Woman, with Michael Balcon in 1923, on the back of its success produced pictures for the veteran director Maurice Elvey, including the classic British silent Hindle Wakes, his first picture as director was The Arcadians. In 1929 he and Balcon worked together again on a talkie remake of Woman to Woman for Balcon's company, Gainsborough Pictures; this time Saville directed it. From 1931, as Gainsborough Pictures and the Gaumont British Picture Corporation joined forces, Saville produced a string of comedies and dramas for Gainsborough and Gaumont-British, including the popular Jessie Matthews pictures. In 1937, he left to set up his own production company, Victor Saville Productions, made three pictures for Alexander Korda's London Films at Denham studios; as an independent producer he had purchased the film rights to A. J. Cronin's novel The Citadel.
He was persuaded to sell them to Metro-Goldwyn-Mayer in return for the chance to produce the film and another big-budget adaptation, Goodbye Mr Chips. Both films starred Robert Donat and were a great success in the USA as well as in Britain, providing Saville with a passport to Hollywood; when the war broke out in 1939, Saville was advised to remain there. He produced pictures in support of the war effort, such as The Mortal Storm and Forever and a Day, in 1945 Tonight and Every Night, based on the history of the Windmill Theatre in London. After the war Saville continued directing films for MGM but returned to Britain. Saville acquired production rights for Mickey Spillane's Mike Hammer mysteries and produced a few features, though Spillane thought he was interested in doing so only to acquire the money to produce The Silver Chalice, he produced two final films in the 1960s, The Greengage Summer, adapted from the novel of the same name, Mix Me a Person. BFI screenonline biography "Saville, Victor" Retrieved on 2 February 2009 Robinson.
Movies of the Thirties. Orbis Publishing, London. ISBN 0-85613-523-2. Victor Saville on IMDb Victor Saville at AllMovie
Ralph Meeker was an American film and television actor. He first rose to prominence for his roles in the Broadway productions of Mister Roberts and Picnic, the former of which earned him a Theatre World Award for his performance. In film, Meeker is best known for his portrayal of Mike Hammer in Robert Aldrich's 1955 film noir cult classic Kiss Me Deadly. Meeker went on to play a series of roles that used his husky and macho screen presence, including a lead role in Stanley Kubrick's military courtroom drama Paths of Glory, as a troubled mechanic opposite Carroll Baker in Something Wild, as a World War II captain in The Dirty Dozen, in the gangster film The St. Valentine's Day Massacre. Other credits include supporting roles in Sidney Lumet's The Anderson Tapes, he had a prolific career in television, appearing as Sergeant Steve Dekker on the series Not for Hire, in the television horror film The Night Stalker. After suffering a stroke in 1980, Meeker was forced to retire from acting, died eight years of a heart attack in Los Angeles, California.
Meeker was born Ralph Rathgeber in Minneapolis, Minnesota, on November 21, 1920, the son of Ralph and Magnhild Senovia Haavig Meeker Rathgeber. He spent his early life in Chicago, Illinois. Meeker attended the Leelanau School in Glen Arbor Township and was made a member of its hall of fame, he graduated from Northwestern University in 1942. Meeker served in the United States Navy during World War II, but was discharged after a few months with a neck injury. Meeker began his career on stage, appearing in minor roles in the Broadway production of Strange Fruit directed by Jose Ferrer, which ran for 60 performances, he followed it with a minor part in Cyrano de Bergerac, starring Ferrer and directed by Mel Ferrer which went for 163 performances. Meeker starred on Broadway in Mister Roberts, directed by Joshua Logan and produced by Leland Hayward. Theatre World said, he was understudy for Henry Fonda. Meeker's big breakthrough came when he took over the role of Stanley Kowalski from Marlon Brando in the second year of the original Broadway production of A Streetcar Named Desire, directed by Elia Kazan.
Logan and Hayward agreed to release him from Mister Roberts. He started appearing in June 1949, he played the role until the Broadway run ended in December and toured on the road with it. Meeker made his film debut in the Swiss-made Four in a Jeep, directed by Leopold Lindtberg, he played a starring role alongside Viveca Lindfors. Meeker was signed to a term contract by MGM who put him in Teresa, directed by Fred Zinnemann. Meeker played a support role, a sergeant, the film was popular. MGM cast him in the leading role in Shadow in the Sky, alongside Nancy Davis Nancy Reagan; the studio tried him in Glory Alley, billed above Leslie Caron and directed by Raoul Walsh. Both films flopped. Paramount borrowed him to play Betty Hutton's leading man in Somebody Loves Me, a musical, it was a minor hit. Meeker's next two MGM films were popular, he had a supporting role as a misfit ex-cavalryman in the classic Western The Naked Spur directed by Anthony Mann starring James Stewart. He was ten was in a well received thriller with Barry Sullivan, Jeopardy.
His final film for MGM was Code Two, which made a small loss. Meeker appeared on TV shows like The Revlon Mirror Theater and Lux Video Theatre. In 1954 Meeker was cast in a Broadway production of William Inge's Picnic, directed by Logan and starring Paul Newman and Janice Rule; the play was a commercial success, running for 477 performances. Meeker was awarded the New York Critic's Circle Award in 1954. Picnic became a classic film in 1955, with William Holden and Kim Novak starring in the roles originated by Meeker and Janice Rule. According to Turner Classic Movies, Meeker turned down the lead role because he did not wish to sign a long-term contract with the production company, he never was offered a role of similar stature again. Meeker returned to films playing a cold-blooded convict in Big House, U. S. A.. In his most-remembered role, Meeker starred as private detective Mike Hammer in the 1955 Robert Aldrich film of Mickey Spillane's Kiss Me Deadly. Many years this film acquired cult status and was seen as an influence on French New Wave directors such as Jean-Luc Godard.
He played a member of the French Foreign Legion in Desert Sands. He was discussed to star in a Spillane sequel My Gun is Quick, he was in A Woman's Devotion co-starring Rule. On television, Meeker starred in the 1955 premiere episode, "Revenge", of CBS's Alfred Hitchcock Presents, along with Vera Miles, he guest starred on shows like Studio One in Hollywood, Star Stage, The Alcoa Hour, Goodyear Playhouse, Jane Wyman Presents The Fireside Theatre, Studio 57, Zane Grey Theater, Playhouse 90, The 20th Century-Fox Hour. In 1957, he portrayed an ex-convict who kidnaps and falls for Jane Russell in the romantic comedy, The Fuzzy Pink Nightgown, which failed at the box office. More popular was a Sam Fuller Western, Run of the Arrow, with Meeker in a support role, he produced a film in Kindergarten. That same year, he appeared in Stanley Kubrick's Paths of Glory, playing a soldier, Corporal Paris, accused of cowardice during battle in World War I. Meeker
Bunker Hill, Los Angeles
Bunker Hill is a historic prominence that traditionally separated Downtown Los Angeles from the rest of the city to the west before the hill was tunneled through at Second Street in 1924. In the late 20th century, the hill was lowered in elevation, the entire area was redeveloped to supplant old frame and concrete buildings with modern high-rises and other structures for residences, commerce and education. In 1867, two wealthy developers, Prudent Beaudry, a French-Canadian Immigrant, Stephen Mott purchased a majority of the hill's land. Beaudry's land purchase ranged from present time Hill St. to Olive St. and 4th St. and 2nd St. Mott's land purchase ranged between 4th St. to Temple and Figueroa and Grand. Because of the hill's excellent views of the Los Angeles Basin and the Los Angeles River, he knew that it would make for an opulent subdivision. Beaudry employed surveyor George Hansom to help divide up the land into 80 plots to sell to individual buyers. Beaudry's started to build his house on the top of a modest two-story structure.
He needed the infrastructure set up to reach the top such as the water pipes. He asked the Los Angeles Water Company. Due to the nature of the hill and their initial concerns about the plan they denied his plea; as result, he built his own pipes and formed the Canal and Reservoir Company He developed the peak of Bunker Hill with lavish two-story Victorian houses that became famous as homes for the upper-class residents of Los Angeles. The dominant architecture of the community of the houses of Bunker Hill was Queen Anne and Eastlake style; the geography of the Hill allowed these residents to escape the hustle and bustle of the city as it grew around at the flatland at the bottom of the hill. Some notable residents during these times are: Prudent Beaudry - 13th Mayor of Los Angeles, developer of Bunker Hill L. J. Rose: Arrived from Iowa, due to the death of his son to serious bronchial trouble during a harsh winter. Wine maker and entrepreneur Dr. Edmund Hildreth: Retired Clergyman from Chicago D.
F. Donigan: Self-made man. Owned his own contracting business, the contractor for the construction of the first railroad which led from Los Angeles to Pasadena, he became an indispensable adviser to Beaudry when it came to beginning the development of Bunker Hill in its early stages. Colonel Louis W. Bradbury and his wife - Made their fortune from a silver mine in Southern California. Original owner of the Bradbury Building in Downtown LA Judge Robert M. Widney - Founder of University of Southern California. Helped create the first transportation for the residents up a horse-drawn carriage. After the introduction of the horse carriage to the Bunker Hill neighborhood, the iconic Angel's Flight was proposed. Angel's Flight, now dubbed "The World's Shortest Railway", took residents homeward from the bottom of the 33% grade and down again. Colonel J. W. Eddy petitioned the Los Angeles City Council to establish an electric cable railway, approved ten days signed by the mayor at the time, Meredith P. Snyder.
The first railways, established and operational was on Third St, from Hill st. to Olive st. A residential suburb, Bunker Hill retained its exclusive character through the end of World War I. Around the 1920s and the 1930s, with the advent of the Pacific Electric Railway and the construction of the freeway, the increased urban growth fed by an extensive streetcar system, its wealthy residents began leaving for enclaves Westward in Beverly Hills and Pasadena. Bunker Hill's houses were subdivided to accommodate renters. Still, Bunker Hill was at this time "Los Angeles's most crowded and urban neighborhood". By World War II, the Pasadena Freeway, built to bring shoppers downtown, was taking more residents out. Additional postwar freeway construction left downtown comparatively empty of both people and services; the once-grand Victorian mansions of Bunker Hill became the home of impoverished pensioners. These tenements became more prominent, apartment buildings started being built on alongside these houses.
As more and more people crowded into these cheap housing units, the population of the hill increased 19%. The increase was due to these new residents that landed on the lower income spectrum, which had moved into the existing living accommodations; as the once extravagant and elaborate Victorian buildings began to fade and deteriorate, the community had an uptake of crime which led to the community being called blighted and the slums of downtown Los Angeles. This led the district to gain its notoriety in the genre of Film Noir. In 1955, Los Angeles city planners decided that Bunker Hill required a massive slum clearance project. There were a couple of major political events which led to the "removal of the blight" and redevelopment of Bunker hill; the California Community Redevelopment Law of 1945, the Federal Housing Act of 1946 and 1949, the creation of the Community Redevelopment Agency in 1948, the Bunker Hill Urban Renewal Project in 1959. The California Community Redevelopment law of 1945 allowed counties and cities to create and implement these agencies to help deal with the redevelopment of local cities.
Until 2011, these Agencies held much power and were still around, until Governor Jerry Brown signed into law two bills to dissolve them. Along with those political factors, other things which led to the conclusion of the blighted neighborhood came from some of the government offices; the LAPD called the area a "high frequency crime area", due to the fact that the area's apartments catered to known offenders. The Health department of Los Angeles called the area a health hazard for its city, it wasn't until the CRA had won an ongoing court case agai
Hitchhiking is a means of transportation, gained by asking people strangers, for a ride in their automobile or other vehicle. A ride is but not always, free. Itinerants have used hitchhiking as a primary mode of travel for the better part of the last century, continue to do so today. Signals used by hitchhikersHitchhikers use a variety of signals to indicate they need a ride. Indicators can be physical displays including written signs; the physical gestures, e.g. hand signals, hitchhikers use differ around the world: In some African countries, the hitchhiker's hand is held with the palm facing upwards. In most of Europe, North America, the United Kingdom, most hitchhikers stand with their back facing the direction of travel facing oncoming vehicles; the hitchhiker extends their arm towards the road with the thumb of the closed hand pointing upward or in the direction of vehicle travel. In other parts of the world, such as Australia, it is more common to use the index finger to point at the road.
Signals used by driversIn 1971, during the Vietnam War, drivers invented methods to communicate various messages to hitchhikers. To indicate to a hitchhiking soldier that their vehicle has no additional space to accommodate them, a driver could tap on the vehicle roof. Another common message that drivers could signal to hitchhikers—who sought to travel long distances, distances too far to walk in a reasonable amount of time—was that the driver's destinations were located nearby—and of little use to the hitchhiker—by pointing at the ground for a few seconds. Hitchhiking is a common practice worldwide and hence there are few places in the world where laws exist to restrict it. However, a minority of countries have laws. In the United States, for example, some local governments have laws outlawing hitchhiking, on the basis of drivers' and hitchhikers' safety. In 1946, New Jersey arrested and imprisoned a hitchhiker, leading to intervention by the American Civil Liberties Union. In Canada, several highways have restrictions on hitchhiking in British Columbia and the 400-series highways in Ontario.
In all countries in Europe, it is legal to hitchhike and in some places encouraged. However, worldwide where hitchhiking is permitted, laws forbid hitchhiking where pedestrians are banned, such as the Autobahn, motorways or interstate highways, although hitchhikers obtain rides at entrances and truck stops where it is legal at least throughout Europe with the exception of Italy. In 2011, Freakonomics Radio reviewed sparse data about hitchhiking, identified a decline in hitchhiking in the US since the 1970s, which it attributed to a number of factors, including lower air travel costs due to deregulation, the presence of more money in the economy to pay for travel, more numerous and more reliable cars, a lack of trust of strangers. Fear of hitchhiking is thought to have been spurred by movies such as The Texas Chain Saw Massacre and a few real stories of imperiled passengers, notably the kidnapping of Colleen Stan in California. See § Safety, below. Julian Portis points out that the rise of faster highways, such as freeways and expressways, has made hitchhiking more difficult.
He adds: The real danger of hitchhiking has most remained constant, but the general perception of this danger has increased.... Ur national tolerance for danger has gone down: things that we saw as reasonably safe appeared imminently threatening; this trend is not just isolated to the world of hitchhiking. Some British researchers discuss reasons for hitchhiking's decline in the UK, possible means of reviving it in safer and more-organized forms. In recent years, hitchhikers have started efforts to strengthen their community. Examples include the annual Hitchgathering, an event organized by hitchhikers, for hitchhikers, websites such as hitchwiki and hitchbase, which are platforms for hitchhikers to share tips and provide a way of looking up good hitchhiking spots around the world. Limited data is available regarding the safety of hitchhiking. Compiling good safety data requires counting hitchhikers, counting rides, counting problems: a difficult task. Two studies on the topic include a 1974 California Highway Patrol study and a 1989 German federal police study.
The California study found that hitchhikers were not disproportionately to be victims of crime. The German study concluded, they found that in some cases there were verbal disputes or inappropriate comments, but physical attacks were rare. Recommended safety practices include: Asking for rides at gas stations instead of signaling at the roadside Refusing rides from impaired drivers Hitchhiking during daylight hours Trusting one's instincts Traveling with another hitchhiker. Hitchhiking is encouraged, as Cuba has few cars, hitch hikers use designated spots. Drivers pick up waiting riders on a first come, first served basis. In Israel, hitchhiking is commonplace at designated locations called trempiyadas. Travelers soliciting rides, called trempists, wait at trempiyadas junctions of highw
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 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. Along the way, the project absorbed Tube Alloys; the Manhattan Project began modestly in 1939, but grew to employ more than 130,000 people and cost nearly US$2 billion. 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, Canada. Two types of atomic bombs were developed concurrently during the war: a 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, 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, with the same mass, it proved difficult to separate the two. Three methods were employed for uranium enrichment: electromagnetic and thermal. Most of this work was performed at the Clinton Engineer Works at 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 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 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, rounded up German scientists. Despite the Manhattan Project's tight security, Soviet atomic spies penetrated the program; the first nuclear device 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 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.
The discovery of nuclear fission by German chemists Otto Hahn and Fritz Strassmann in 1938, its theoretical explanation by Lise Meitner and Otto Frisch, made the development of an atomic bomb a theoretical possibility. There were fears that a German atomic bomb project would develop one first among scientists who were refugees from Nazi Germany and other fascist countries. In August 1939, Hungarian-born physicists Leó Szilárd and Eugene Wigner drafted the Einstein–Szilárd letter, which warned of the potential development of "extremely powerful bombs of a new type", it urged the United States to take steps to acquire stockpiles of uranium ore and accelerate the research of Enrico Fermi and others into nuclear chain reactions. They had it delivered to President Franklin D. Roosevelt. Roosevelt called on Lyman Briggs of the National Bureau of Standards to head the Advisory Committee on Uranium to investigate the issues raised by the letter. Briggs held a meeting on 21 October 1939, attended by Szilárd, Wigner and Edward Teller.
The committee reported back to Roosevelt in November that uranium "would provide a possible source of bombs with a destructiveness vastly greater than anything now known."The Advisory Committee on Uranium became the National Defense Research Committee Committee on Uranium when that organization was formed on 27 June 1940. Briggs proposed spending $167,000 on research into uranium the uranium-235 isotope, the discovered plutonium. On 28 June 1941, Roosevelt signed Executive Order 8807, which created the Office of Scientific Research and Development, with Vannevar Bush as its director; the office was empowered to engage in large engineering projects in addition to research. The NDRC Committee on Uranium became the S-1 Section of the OSRD. In Britain and Rudolf Peierls at the University of Birmingham had made a breakthrough investigating the critical mass of uranium-235 in June 1939, their calculations indicated that it was within an order of magnitude of 10 kilograms, small enough to be carried by a bomber of the day.
Their March 1940 Frisch–Peierls memorandum initiated the British atomic bomb project and its Maud Committee, which unanimously recommended pursuing the development of an atomic bomb