The Dayton Project was a research and development project to produce
polonium
Polonium is a chemical element; it has symbol Po and atomic number 84. A rare and highly radioactive metal (although sometimes classified as a metalloid) with no stable isotopes, polonium is a chalcogen and chemically similar to selenium and tel ...
during
World War II
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
, as part of the larger
Manhattan Project
The Manhattan Project was a research and development program undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and Canada.
From 1942 to 1946, the ...
to build the first
atomic bombs
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission or atomic bomb) or a combination of fission and fusion reactions (thermonuclear weapon), producing a nuclear explos ...
. Work took place at several sites in and around
Dayton, Ohio
Dayton () is a city in Montgomery County, Ohio, United States, and its county seat. It is the List of cities in Ohio, sixth-most populous city in Ohio, with a population of 137,644 at the 2020 United States census, 2020 census. The Dayton metro ...
. Those working on the project were ultimately responsible for creating the polonium-based
modulated neutron initiator
A modulated neutron initiator is a neutron source capable of producing a burst of neutrons on activation. It is a crucial part of some nuclear weapons, as its role is to "kick-start" the chain reaction at the optimal moment when the configuration i ...
s that were used to begin the chain reactions in the atomic bombs.
The Dayton Project began in 1943 when
Monsanto
The Monsanto Company () was an American agrochemical and agricultural biotechnology corporation founded in 1901 and headquartered in Creve Coeur, Missouri. Monsanto's best-known product is Roundup, a glyphosate-based herbicide, developed ...
's
Charles Allen Thomas was recruited by the Manhattan Project to coordinate the
plutonium
Plutonium is a chemical element; it has symbol Pu and atomic number 94. It is a silvery-gray actinide metal that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four ...
purification and production work being carried out at various sites. Scientists at the
Los Alamos Laboratory
The Los Alamos Laboratory, also known as Project Y, was a secret scientific laboratory established by the Manhattan Project and overseen by the University of California during World War II. It was operated in partnership with the United State ...
calculated that a plutonium bomb would require a neutron initiator. The best-known neutron sources used radioactive polonium and
beryllium
Beryllium is a chemical element; it has Symbol (chemistry), symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with ...
, so Thomas undertook to produce polonium at Monsanto's laboratories in Dayton. While most Manhattan Project activity took place at remote locations, the Dayton Project was located in a populated, urban area. It ran from 1943 to 1949, when the
Mound Laboratories were completed in nearby
Miamisburg, Ohio
Miamisburg ( ) is a city in southern Montgomery County, Ohio, United States. The population was 19,923 at the 2020 census. A suburb of Dayton, it is part of the Dayton metropolitan area. Named after the Miami people, Miamisburg is known for its ...
, and the work moved there.
The Dayton Project developed techniques for extracting polonium from the
lead dioxide
Lead(IV) oxide, commonly known as lead dioxide, is an inorganic compound with the chemical formula . It is an oxide where lead is in an oxidation state of +4. It is a dark-brown solid which is insoluble in water. It exists in two crystalline forms ...
ore in which it occurs naturally, and from
bismuth
Bismuth is a chemical element; it has symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs nat ...
targets that had been bombarded by neutrons in a
nuclear reactor
A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons ...
. Ultimately, polonium-based neutron initiators were used in both the
gun-type Little Boy
Little Boy was a type of atomic bomb created by the Manhattan Project during World War II. The name is also often used to describe the specific bomb (L-11) used in the bombing of the Japanese city of Hiroshima by the Boeing B-29 Superfortress ...
and the
implosion-type Fat Man
"Fat Man" (also known as Mark III) was the design of the nuclear weapon the United States used for seven of the first eight nuclear weapons ever detonated in history. It is also the most powerful design to ever be used in warfare.
A Fat Man ...
used in the
atomic bombings of Hiroshima and Nagasaki
On 6 and 9 August 1945, the United States detonated two atomic bombs over the Japanese cities of Hiroshima and Nagasaki, respectively, during World War II. The aerial bombings killed between 150,000 and 246,000 people, most of whom were civili ...
respectively. The fact that polonium was used as an initiator was classified until the 1960s, but
George Koval
George Abramovich Koval ( rus, Жорж (Георгий) Абрамович Коваль, p=ˈʐorʐ (ɡʲɪˈorɡʲɪj) ɐˈbraməvʲɪtɕ kɐˈvalʲ, a=Ru-George Abramovich Koval.flac, Zhorzh Abramovich Koval; December 25, 1913 – January 31 ...
, a technician with the Manhattan Project's
Special Engineer Detachment, penetrated the Dayton Project as a spy for the
Soviet Union
The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
.
Background
In December 1942, during
World War II
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
,
Charles Allen Thomas, a chemist and director of research at
Monsanto
The Monsanto Company () was an American agrochemical and agricultural biotechnology corporation founded in 1901 and headquartered in Creve Coeur, Missouri. Monsanto's best-known product is Roundup, a glyphosate-based herbicide, developed ...
in
St. Louis
St. Louis ( , sometimes referred to as St. Louis City, Saint Louis or STL) is an independent city in the U.S. state of Missouri. It lies near the confluence of the Mississippi and the Missouri rivers. In 2020, the city proper had a populatio ...
, joined the
National Defense Research Committee
The National Defense Research Committee (NDRC) was an organization created "to coordinate, supervise, and conduct scientific research on the problems underlying the development, production, and use of mechanisms and devices of warfare" in the U ...
(NDRC) as the deputy chief of its Division 8, which was responsible for propellants, explosives and the like. Early in 1943, he traveled to the east with
Richard C. Tolman
Richard Chace Tolman (March 4, 1881 – September 5, 1948) was an American mathematical physicist and physical chemist who made many contributions to statistical mechanics and theoretical cosmology. He was a professor at the California Ins ...
, a member of the NDRC, and
James B. Conant
James Bryant Conant (March 26, 1893 – February 11, 1978) was an American chemist, a transformative President of Harvard University, and the first United States Ambassador to West Germany, U.S. Ambassador to West Germany. Conant obtained a ...
, the president of
Harvard University
Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...
and the chairman of the NDRC, to witness a demonstration of a new underwater explosive. Conant and Tolman took the opportunity to quietly investigate Thomas' background. He was then invited to a meeting in Washington D.C., with
Brigadier General Leslie R. Groves, Jr., the director of the wartime
Manhattan Project
The Manhattan Project was a research and development program undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and Canada.
From 1942 to 1946, the ...
responsible for building an
atomic bomb
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission or atomic bomb) or a combination of fission and fusion reactions (thermonuclear weapon), producing a nuclear expl ...
. When he got there, Thomas found Conant was also present.
Groves and Conant were hoping to harness Thomas's industrial expertise. They offered him a post as a deputy to
Robert Oppenheimer
J. Robert Oppenheimer (born Julius Robert Oppenheimer ; April 22, 1904 – February 18, 1967) was an American theoretical physicist who served as the director of the Manhattan Project's Los Alamos Laboratory during World War II. He is often ...
, the director of the
Los Alamos Laboratory
The Los Alamos Laboratory, also known as Project Y, was a secret scientific laboratory established by the Manhattan Project and overseen by the University of California during World War II. It was operated in partnership with the United State ...
in New Mexico, but he did not wish to move his family or give up his responsibilities at Monsanto. Instead, he accepted the role of coordinating the
plutonium
Plutonium is a chemical element; it has symbol Pu and atomic number 94. It is a silvery-gray actinide metal that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four ...
purification and production work being carried out at Los Alamos, the
Metallurgical Laboratory in Chicago,
Radiation Laboratory
The Radiation Laboratory, commonly called the Rad Lab, was a microwave and radar research laboratory located at the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts. It was first created in October 1940 and operated until 3 ...
in Berkeley, and
Ames Laboratory
Ames National Laboratory, formerly Ames Laboratory, is a United States Department of Energy national laboratory located in Ames, Iowa, and affiliated with Iowa State University. It is a top-level national laboratory for research on national sec ...
in Iowa. Chemistry and metallurgy at Los Alamos would be led by the youthful
Joseph W. Kennedy.
At Los Alamos, physicist
Robert Serber
Robert Serber (March 14, 1909 – June 1, 1997) was an American physicist who participated in the Manhattan Project. Serber's lectures explaining the basic principles and goals of the project were printed and supplied to all incoming scientific st ...
proposed that instead of relying on spontaneous fission, the chain reaction inside the atomic bomb should be triggered by a
neutron initiator
A modulated neutron initiator is a neutron source capable of producing a burst of neutrons on activation. It is a crucial part of some nuclear weapons, as its role is to "kick-start" the chain reaction at the optimal moment when the configuration i ...
. The best-known neutron sources were
radium
Radium is a chemical element; it has chemical symbol, symbol Ra and atomic number 88. It is the sixth element in alkaline earth metal, group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, ...
-
beryllium
Beryllium is a chemical element; it has Symbol (chemistry), symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with ...
and
polonium
Polonium is a chemical element; it has symbol Po and atomic number 84. A rare and highly radioactive metal (although sometimes classified as a metalloid) with no stable isotopes, polonium is a chalcogen and chemically similar to selenium and tel ...
-beryllium. The latter was chosen, as polonium has a 138-day
half-life Half-life is a mathematical and scientific description of exponential or gradual decay.
Half-life, half life or halflife may also refer to:
Film
* Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang
* ''Half Life: ...
, which made it intense enough to be useful but not long-lived enough to be stockpiled. Thomas took charge of the development of techniques to industrially refine polonium for use with beryllium in the
"urchin" internal neutron initiators. This effort became the Dayton Project.
Organization

Thomas brought in key personnel from Monsanto's Thomas and Hochwalt Laboratories in
Dayton, Ohio
Dayton () is a city in Montgomery County, Ohio, United States, and its county seat. It is the List of cities in Ohio, sixth-most populous city in Ohio, with a population of 137,644 at the 2020 United States census, 2020 census. The Dayton metro ...
, including Caroll Hochwalt, James Lum and Nicholas Samaras. Thomas became Director of the Dayton Project, with Hochwalt as Assistant Project Director and Lum as Laboratory Director. They decided that about twelve chemists would be required, and Lum set about recruiting professors, graduate students and industrial chemists from universities and laboratories in the area. The first of these recruits commenced in August 1943, but few had any experience with
radiochemistry
Radiochemistry is the chemistry of radioactive materials, where radioactive isotopes of elements are used to study the properties and chemical reactions of non-radioactive isotopes (often within radiochemistry the absence of radioactivity leads t ...
. Numbers increased from 46 full-time employees at the end of 1943 to 101 at the end of 1944, 201 at the end of 1945, and 334 at the end of 1946, including 34 members of the Army's
Special Engineer Detachment.
Locations
Office space was initially found in the Monsanto offices at 1515 Nicholas Rd, which became known as Unit I.
Unit II was the Monsanto Rocket Propellant works off Betty Lane near
Ohio State Route 741. While it was administered by Monsanto, it was not used by the Dayton Project. The site handled explosives including
ammonium nitrate
Ammonium nitrate is a chemical compound with the formula . It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, but does not form hydrates. It is predominantly us ...
and
ammonium picrate
Dunnite, also known as Explosive D or systematically as ammonium picrate, is an explosive developed in 1906 by US Army Major Beverly W. Dunn, who later served as chief inspector of the Bureau of Transportation Explosives. Ammonium picrate is a sa ...
, but no radioactive materials were handled there. Work at Unit II ceased in the fall of 1945. Consideration was given to using it in December 1946, but this proposal was rejected in favor of erecting a
Quonset hut
A Quonset hut is a lightweight prefabricated structure of corrugated galvanized steel with a semi-circular cross-section. The design was developed in the United States based on the Nissen hut introduced by the British during World War I. Hund ...
at Unit III.
A laboratory site was found at 1601 W. First Street that had originally been constructed to house the
Bonebrake Seminary. It was a three-story brick building built in 1879, and owned by the Dayton Board of Education, which used it as a warehouse. Monsanto leased the site on 15 October 1943, and began converting it into a laboratory known as Unit III. The building was in poor shape when the Dayton Project took it over, with many broken windows, and the staircase between the second and third floors was missing. New heating and lighting were installed, windows were replaced, new flooring was laid, and some rooms were re-plastered. A pair of guard houses known as buildings J and K were added, as was a chemical storage shed known as building F, and a wire fence. Laboratory activities were transferred there from Unit I on 25 September. Initially only the bottom two floors were occupied, providing of laboratory space. Later, the third floor was taken over as well, providing another .
In May 1945, five additional temporary buildings were constructed on land leased from the Board of Education that housed offices, a cafeteria, locker rooms, a physics laboratory and a laundry. A new guardhouse was also built. To this was added two portable buildings in 1946.

By 1944, space was running short, and Monsanto began negotiations to acquire the Runnymede Playhouse in the wealthy residential Dayton suburb of
Oakwood. Built in 1927, the Playhouse was a leisure facility that included an outdoor swimming pool, a ballroom, a squash court, a tennis court with a cork floor and a stage for community theater. It had showers with Italian marble and a -story garage.
The estate was owned by the Talbott Realty Company, which was controlled by Thomas's
wife's family. The Talbotts were among the heirs of the
Delco company, which was by then a part of
General Motors
General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. The company is most known for owning and manufacturing f ...
.
The Oakwood City Council wanted the Playhouse as a community center. Thomas appeared before the council and assured them that it would not be damaged, although he could not disclose what he was intending to use it for.
When Talbott Realty proved reluctant to sell, the
United States Army Corps of Engineers
The United States Army Corps of Engineers (USACE) is the military engineering branch of the United States Army. A direct reporting unit (DRU), it has three primary mission areas: Engineer Regiment, military construction, and civil wo ...
condemned the property, which became Unit IV on 15 February 1944. A lease was signed on 10 March 1944, under which the Talbott Realty was paid $4,266.72 per annum for the property. The lease was initially up to 30 June 1944, but was then extended annually until 30 June 1949. The lease specified that the property would be returned in its original condition. Talbott Realty were told that the property would be used to produce training films.

Remodeling began on 17 March 1944. The tennis courts were subdivided into multiple rooms. The ceiling was lowered, and heating, air conditioning and air filtration systems were added. One of the greenhouses was converted into a
loading dock
A loading dock or loading bay is an area of a building where goods vehicles (usually road or rail) are loaded and unloaded. They are commonly found on commercial and industrial buildings, and warehouses in particular. Loading docks may be exteri ...
. The property was enclosed in a barbed wire fence that was floodlit by night, and patrolled around the clock by armed guards; there were 43 guards at Units III and IV. The Production Group began moving in on 1 June. Three guard houses were added, along with a wire fence. Changes to the site were minimized in order to make it easier to restore later. Because it was located in a residential area, efforts were also made to minimize noise and other disruptions.
In May 1945, Monsanto rented three floors of a warehouse at 601 East Third Street from
General Electric
General Electric Company (GE) was an American Multinational corporation, multinational Conglomerate (company), conglomerate founded in 1892, incorporated in the New York (state), state of New York and headquartered in Boston.
Over the year ...
. Initially it was used to receive and store equipment used by the Project. Later the fourth floor was used as office space, and a laboratory was established on the fifth floor where studies were carried out on the effects of polonium on laboratory animals. Analysis of
bioassay
A bioassay is an analytical method to determine the potency or effect of a substance by its effect on animal testing, living animals or plants (''in vivo''), or on living cells or tissues (''in vitro''). A bioassay can be either quantal or quantit ...
samples was carried out there to minimize the danger of polonium contamination of the samples.
Research
Few people had seen polonium before. It was a silvery metal. In a dark room, it gave off an eerie, purple glow. Polonium occurs naturally in various ores, and the
lead dioxide
Lead(IV) oxide, commonly known as lead dioxide, is an inorganic compound with the chemical formula . It is an oxide where lead is in an oxidation state of +4. It is a dark-brown solid which is insoluble in water. It exists in two crystalline forms ...
residues from the refinery in
Port Hope, Ontario
Port Hope is a municipality in Southern Ontario, Canada, about east of Toronto and west of Kingston, Ontario, Kingston. It is at the mouth of the Ganaraska River on the north shore of Lake Ontario, in the west end of Northumberland County, Onta ...
, left over after the removal of
uranium
Uranium is a chemical element; it has chemical symbol, symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Ura ...
and radium, were estimated to contain of polonium per metric ton. A
curie Curie may refer to:
*Curie family, a family of distinguished scientists:
:* Jacques Curie (1856–1941), French physicist, Pierre's brother
:* Pierre Curie (1859–1906), French physicist and Nobel Prize winner, Marie's husband
:* Marie Curi ...
of polonium weighs about . Port Hope was already under contract from the Manhattan Project for the supply and refining of uranium ore. The first of radioactive lead dioxide was delivered to the Dayton Project on 10 November 1943. The first batch was processed by 8 December, which made of polonium available for experiments a week later.
Three processes were investigated for extracting the polonium from the ore. J. H. Dillon of the
Firestone Tire and Rubber Company
Firestone Tire and Rubber Company is an American tire company founded by Harvey S. Firestone (18681938) in 1900 initially to supply solid rubber side-wire tires for fire apparatus, and later, pneumatic tires for wagons, carriages, and other form ...
had patented a process in which the lead oxide was dissolved in
hydrochloric acid
Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...
:
: + 4 HCl → + + 2
The polonium could then be deposited on
copper
Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...
or
nickel
Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...
sheets. This required large-scale glass-lined equipment not available in Dayton, but available at the Monsanto B plant in
Monsanto, Illinois. After small-scale tests at Unit III revealed that the process was practical, some three tons of lead dioxide were sent to the B plant, and were recovered. Getting the polonium off the copper and nickel sheets proved more problematic.
A second method attempted was a kiln process. The idea was to simply roast the lead dioxide and vaporize the polonium. The problem was that lead dioxide slagged at , which was too low for the process to work. So
lead orthophosphate was tried, which slagged at . This was made by mixing the lead dioxide with
phosphoric acid
Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, ...
. Experiments showed that the polonium vaporized well when the lead orthophosphate was heated to for four hours. Unfortunately, the process then ran into problems with dust and other foreign matter, and with contamination of the personnel and equipment involved.
The third method involved dissolving the lead dioxide in a mixture of concentrated
nitric acid
Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...
and
hydrogen peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...
:
: + 2 + → + + 2
This proved to be the best way to separate the polonium from the lead dioxide, although there were problems with the precipitation of various contaminants, including
iron
Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
and
aluminum
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
. Although about of lead dioxide were treated with nitric acid, and about of polonium were produced, the process did not proceed beyond the pilot stage because a better source of polonium became available. The lead dioxide was not purchased by the Manhattan Project, and early in the war had been acquired by the Canadian government. In June 1945, the lead was precipitated as a
lead carbonate
Lead(II) carbonate is the chemical compound with the chemical formula . It is a white, toxic solid. It occurs naturally as the mineral cerussite.
Structure
Like all metal carbonates, lead(II) carbonate adopts a dense, highly crosslinked structure ...
slurry, and shipped to the Manhattan District's Madison Square area to be dried and returned to Canada.
Production
Polonium could also be produced by neutron irradiation of
bismuth
Bismuth is a chemical element; it has symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs nat ...
. In 1943 the only polonium produced in this manner was in
cyclotron
A cyclotron is a type of particle accelerator invented by Ernest Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Januar ...
s, but the Manhattan Project's development of
nuclear reactor
A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons ...
s offered the prospect of producing large amounts of polonium in this manner:
: + → → +
A metric ton of bismuth irradiated in the Manhattan Project's
X-10 Graphite Reactor at the
Clinton Engineer Works
The Clinton Engineer Works (CEW) was the production installation of the Manhattan Project that during World War II produced the enriched uranium used in the 1945 bombing of Hiroshima, as well as the first examples of reactor-produced pluton ...
in
Oak Ridge, Tennessee
Oak Ridge is a city in Anderson County, Tennessee, Anderson and Roane County, Tennessee, Roane counties in the East Tennessee, eastern part of the U.S. state of Tennessee, about west of downtown Knoxville, Tennessee, Knoxville. Oak Ridge's po ...
, contained of polonium, a vast improvement over the yields from Port Hope's lead dioxide. Irradiated bismuth came from Clinton in the form of bricks that weighed about . They were shipped to Dayton by rail in wooden boxes, which were stored in a tile-lined cavity in the floor at Unit IV.
These procedures were adequate because the quantity of polonium in the bismuth was still fairly low, but starting in June 1945, the Dayton Project began receiving bismuth irradiated in the more powerful reactors at the
Hanford Site
The Hanford Site is a decommissioned nuclear production complex operated by the United States federal government on the Columbia River in Benton County in the U.S. state of Washington. It has also been known as SiteW and the Hanford Nuclear R ...
in Washington, which now became the major source of supply. Even at Clinton, unprotected bismuth proved problematic when a brick broke apart and chips fell into containers of uranium slugs, and had to be hazardously separated by hand by project personnel. Bismuth slugs irradiated in the reactors at Hanford were therefore canned in aluminium. The canned slugs were in diameter, and long. The problem was that the aluminium contained impurities such as
iron
Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
,
manganese
Manganese is a chemical element; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...
,
copper
Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...
, lead,
tin
Tin is a chemical element; it has symbol Sn () and atomic number 50. A silvery-colored metal, tin is soft enough to be cut with little force, and a bar of tin can be bent by hand with little effort. When bent, a bar of tin makes a sound, the ...
,
zinc
Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...
,
silicon
Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...
,
titanium
Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
,
nickel
Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...
,
magnesium
Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...
,
chromium
Chromium is a chemical element; it has Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal.
Chromium ...
,
vanadium
Vanadium is a chemical element; it has Symbol (chemistry), symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an ...
, bismuth and
gallium
Gallium is a chemical element; it has Chemical symbol, symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875,
elemental gallium is a soft, silvery metal at standard temperature and pressure. ...
, and when irradiated, these could form radioactive isotopes. Most were of little concern for the Dayton Project, as they had short half-lives, and would become harmless during the slugs' cooling off period in water at Hanford; but iron could form iron-59, which had a half-life of 45 days, and produced gamma radiation. The slugs were therefore shipped in casks, each of which contained several tubes which held the slugs. The spaces between the tubes was filled with lead. At Dayton, the slugs were stored in a lead-lined safe with doors on both sides containing tubes. They were also stored underwater on racks, and could be removed with tongs. A periscope allowed the identification markings on the slugs to be checked without removing them from the pool.
By the end of 1946 Hanford was shipping material that contained up to per metric ton of bismuth. Bismuth was purchased from the
American Smelting and Refining Company
ASARCO (American Smelting and Refining Company) is a mining, smelting, and refining company based in Tucson, Arizona, which mines and processes primarily copper. The company has been a subsidiary of Grupo México since 1999.
Its three largest o ...
of the highest purity that it could produce. It was sent to Hanford, where it was canned, and placed inside a reactor for 100 days. The irradiated slugs were then shipped by road to Unit IV, where they were bathed in hydrochloric acid, which dissolved the aluminum. This formed an aluminum chloride solution that was disposed of, as it was highly radioactive due to the iron impurities in the aluminum. The bismuth slugs were then dissolved in
aqua regia
Aqua regia (; from Latin, "regal water" or "royal water") is a mixture of nitric acid and hydrochloric acid, optimally in a molar concentration, molar ratio of 1:3. Aqua regia is a fuming liquid. Freshly prepared aqua regia is colorless, but i ...
. This was too weak for electroplating the polonium, so the nitric acid was removed, and then the polonium deposited on bismuth by adding powdered bismuth. This resulted in a 100–1 concentration. This could then be repeated by dissolving in aqua regia again to achieve a 1000–1 concentration. This was again dissolved, and the polonium electroplated on
platinum
Platinum is a chemical element; it has Symbol (chemistry), symbol Pt and atomic number 78. It is a density, dense, malleable, ductility, ductile, highly unreactive, precious metal, precious, silverish-white transition metal. Its name origina ...
foils. The main problem with the process was that it required glass-lined containers due to the aqua regia, and mechanisms for safe handling of the radioactive material. The Dayton Project explored alternative purification methods that were found to be workable, but less efficient or safe.
The first consignment of polonium left for Los Alamos on 15 March 1944 in a lead-lined suitcase carried by a military courier. Regular shipments were made thereafter.
Initiator testing at Los Alamos required more polonium than anticipated, and in December 1944, Oppenheimer was forced to ask Thomas if he could ship per month. The Dayton Project was able to do so. In February 1945, Thomas agreed to increase shipments to per month by June, and 500 per month by December.
The total cost of the Dayton Project up to the end of 1946 was $3,666,507 ($ in today's dollars).
Health and safety
Dayton Project employees were not allowed to eat or smoke in processing areas, and had to scrub their hands before leaving these areas. The chemists wore protective gear, with surgical, cloth and rubber gloves worn in three layers. When leaving for lunch or at the end of the shift, they had to wash their hands with dilute hydrochloric acid, dilute
Clorox
The Clorox Company (formerly Clorox Chemical Company) is an American multinational manufacturer and marketer of consumer and professional products. As of 2024, the Oakland, California-based company had approximately 8,000 employees worldwide. N ...
, and soap. The radioactive residue on their hands was measured with a special
Geiger counter
A Geiger counter (, ; also known as a Geiger–Müller counter or G-M counter) is an electronic instrument for detecting and measuring ionizing radiation with the use of a Geiger–Müller tube. It is widely used in applications such as radiat ...
designed for the purpose by physicist John J. Sopka.
No more than one thousand counts per minute per hand was permissible. They had to shower at the end of each day's work, and were subjected to weekly urine tests. Employees with elevated levels of polonium were not allowed in the processing areas. Working with polonium without spreading contamination proved to be almost impossible. Fortunately, it is not a
bone seeker
A bone seeker is an element, often a radioisotope, that tends to accumulate in the bones of humans and other animals when introduced into the body.
For example, strontium and radium are chemically similar to calcium and can replace the calcium i ...
like radium or plutonium, and is thus readily excreted in urine. Detection methods had already been developed, making it easy to track. The employee at Unit IV with the highest levels of polonium in her urine had contaminated her hair, and often held
bobby pin
A bobby pin (US English, known as a kirby grip or hair grip in the United Kingdom) is a type of hairpin, usually of metal or plastic, used in hairstyle, coiffure to hold hair in place. It is a small double-pronged hair pin or clip that slides int ...
s in her mouth.
Espionage
George Koval
George Abramovich Koval ( rus, Жорж (Георгий) Абрамович Коваль, p=ˈʐorʐ (ɡʲɪˈorɡʲɪj) ɐˈbraməvʲɪtɕ kɐˈvalʲ, a=Ru-George Abramovich Koval.flac, Zhorzh Abramovich Koval; December 25, 1913 – January 31 ...
was drafted into the United States Army in 1943, and was inducted into the Manhattan Project's Special Engineer Detachment. He was initially assigned to the Clinton Engineer Works, where his job as a
health physics
Health physics, also referred to as the science of radiation protection, is the profession devoted to protecting people and their environment from potential radiation hazards, while making it possible to enjoy the beneficial uses of radiation. H ...
officer gave him access to much of the site. He began passing secrets relating to the production of polonium at Oak Ridge to the
Soviet Union
The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
through his
GRU
Gru is a fictional character and the main protagonist of the ''Despicable Me'' film series.
Gru or GRU may also refer to:
Arts and entertainment
* Gru (rapper), Serbian rapper
* Gru, an antagonist in '' The Kine Saga''
Organizations Georgia (c ...
(Soviet military intelligence) handler code-named "Clyde". In 1945 Koval was transferred to Dayton. Again, his job as a health physics officer gave him wide access to the secret installation.
In 2007 Russian President
Vladimir Putin
Vladimir Vladimirovich Putin (born 7 October 1952) is a Russian politician and former intelligence officer who has served as President of Russia since 2012, having previously served from 2000 to 2008. Putin also served as Prime Minister of Ru ...
posthumously awarded Koval a gold star, making him a
hero of the Russian Federation
Hero of the Russian Federation ( rus, Герой Российской Федерации, p=ɡʲɪˈroj rɐˈsʲijskəj fʲɪdʲɪˈratsɨɪ), also unofficially called Hero of Russia ( rus, Герой России, p=ɡʲɪˈroj rɐˈsʲiɪ), is ...
for his work as the GRU spy "Delmar". Russian officials stated that the initiator for their
Joe-1 bomb had been "prepared to the recipe provided by Delmar".
The fact that polonium was used as an initiator remained classified until the 1960s.
Initiators
After
Leonard I. Schiff calculated that an initiator might improve the efficiency of a
gun-type fission weapon
Gun-type fission weapons are fission-based nuclear weapons whose design assembles their fissile material into a supercritical mass by the use of the "gun" method: shooting one piece of sub-critical material into another. Although this is someti ...
, Oppenheimer gave approval on 15 March 1945 for initiators to be included in the
Little Boy
Little Boy was a type of atomic bomb created by the Manhattan Project during World War II. The name is also often used to describe the specific bomb (L-11) used in the bombing of the Japanese city of Hiroshima by the Boeing B-29 Superfortress ...
design. The initiators were tested to ensure they were rugged enough to handle being transported in an airplane and being accidentally dropped. Eventually, about forty initiators were dispatched to
Tinian
Tinian () is one of the three principal islands of the Commonwealth of the Northern Mariana Islands (CNMI). Together with uninhabited neighboring Aguiguan, it forms Tinian Municipality, one of the four constituent municipalities of the Northern ...
, where four were inserted into the bomb that was used in the bombing of Hiroshima.
The initiator used in the
implosion design of the
Fat Man
"Fat Man" (also known as Mark III) was the design of the nuclear weapon the United States used for seven of the first eight nuclear weapons ever detonated in history. It is also the most powerful design to ever be used in warfare.
A Fat Man ...
bomb that was dropped on
Nagasaki
, officially , is the capital and the largest Cities of Japan, city of Nagasaki Prefecture on the island of Kyushu in Japan.
Founded by the Portuguese, the port of Portuguese_Nagasaki, Nagasaki became the sole Nanban trade, port used for tr ...
was code-named "urchin". In order to increase the efficiency of the explosion, the initiator had to emit a large number of neutrons in a few microseconds while the plutonium
core
Core or cores may refer to:
Science and technology
* Core (anatomy), everything except the appendages
* Core (laboratory), a highly specialized shared research resource
* Core (manufacturing), used in casting and molding
* Core (optical fiber ...
was fully compressed. At the heart of the urchin was a solid beryllium sphere in diameter. This was
gold
Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...
-plated and coated with of polonium. The gold kept the polonium's
alpha particle
Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay but may also be produce ...
s from striking the beryllium. This fitted inside two beryllium hemispheres with 15 parallel grooves cut into the inner surface. These grooves converted the shock wave of the implosion into
jets that shattered the spheres and caused the beryllium and polonium to mix and emit neutrons. The hemispheres were nickel-plated and the outer surface was coated in gold and of polonium. The initiator, which was hot to the touch, fitted neatly inside the hole in the center of the plutonium pit.
Mound Laboratories

By 1945, the Dayton Project had assumed such importance that the Manhattan Project decided to make it into a permanent facility. The original intention was to move operations to Oak Ridge, but it was decided that a site near Dayton was preferable. Few of the scientific and technical staff wanted to move to Tennessee, and there were concerns about the dangers of polonium contamination at a plutonium processing site. A search for a suitable site began in early 1946, and one was found in Miamisburg, about from Dayton. The site was next to a state park containing a large prehistoric Indian
burial mound
Burial, also known as interment or inhumation, is a method of final disposition whereby a dead body is placed into the ground, sometimes with objects. This is usually accomplished by excavating a pit or trench, placing the deceased and objec ...
, which ultimately gave the
Mound Laboratories its name. It was initially known as Unit V. Monsanto began construction in May 1946, using the Detroit firm of Giffels and Vallet as architects, while the plant was built by the Maxon Construction of Dayton. The design called for an underground complex that could withstand a direct hit from a bomb, with protection against
biological
Biology is the scientific study of life and living organisms. It is a broad natural science that encompasses a wide range of fields and unifying principles that explain the structure, function, growth, origin, evolution, and distribution of ...
and
chemical weapon
A chemical weapon (CW) is a specialized munition that uses chemicals formulated to inflict death or harm on humans. According to the Organisation for the Prohibition of Chemical Weapons (OPCW), this can be any chemical compound intended as ...
s, at a cost of $17,900,000.
Responsibility for nuclear weapons production was transferred from the Manhattan Project to the
Atomic Energy Commission in 1947, but work continued on the Mound Laboratories. The first building was completed in May 1948, and polonium processing commenced at the Mound Laboratories in February 1949. Altogether, 14 major buildings were constructed with a total floor space of at a cost of $25.5 million. Due to fear of attack or sabotage, the former Scioto Laboratory Complex in
Marion, Ohio
Marion is a city in Marion County, Ohio, United States, and its county seat. It is located in north-central Ohio, approximately north of Columbus, Ohio, Columbus. The population was 35,999 at the 2020 United States census, 2020 census, down slig ...
, was acquired by the Atomic Energy Commission in 1948. It was maintained as a cold standby site until it was no longer needed in 1953.
Site cleanup
Unit I continued to be used by Monsanto as an administrative facility until 1988, when it was demolished. The land was sold to Quality Chemicals in 1992, and then to DuPont in 2002. Unit III, the former Bonebrake Theological Seminary, was decontaminated in 1950 and returned to the Dayton Board of Education. The original seminary building was subsequently demolished, but several structures remain from the Dayton Project. The site was listed on the
National Register of Historic Places
The National Register of Historic Places (NRHP) is the Federal government of the United States, United States federal government's official United States National Register of Historic Places listings, list of sites, buildings, structures, Hist ...
on 10 May 2006. Although the lease on Unit IV, the former Runnymede Playhouse, specified that it was to be returned, it was deemed to be too contaminated. The building was demolished in February 1950. The cobblestones in the driveway were removed and taken away, along with of earth from under the house. The excavation was filled in, and the site was returned to the Talbott family, who were paid $138,750 in compensation. , all that remains of the original playhouse is a brass doorknob and part of the greenhouse roof, which are part of the collection of the Mound Science and Energy Museum. Private residences now occupy the site.
The Dayton Warehouse was decontaminated in 1950 and returned to its owners. The Mound Laboratories continued to produce polonium initiators until 1969. Polonium continued to be produced there for commercial sales and use in satellites until 1972. The laboratories were decommissioned in 1993, and the area was decontaminated. , it houses the Mound Advanced Technology Center.
In 1996, the
Department of Energy, which had succeeded the Atomic Energy Commission, decided that since the Dayton sites already had been decontaminated, they did not warrant inclusion in the Army Corps of Engineers'
Formerly Utilized Sites Remedial Action Program
The Formerly Utilized Sites Remedial Action Program (FUSRAP) is a United States Army Corps of Engineers (USACE) project to manage and cleanup environmental contamination that resulted from early United States Atomic Energy Commission activities. C ...
(FUSRAP). The local community in Dayton was concerned that the cleanup did not meet 21st-century environmental standards. Therefore, the state of Ohio asked the
United States Congress
The United States Congress is the legislature, legislative branch of the federal government of the United States. It is a Bicameralism, bicameral legislature, including a Lower house, lower body, the United States House of Representatives, ...
to have the Army Corps of Engineers conduct a review. This was carried out in 2004 and 2005. The review concluded that no radioactive contaminants were found that would warrant inclusion in FUSRAP.
Notes
References
*
*
*
*
*
*
*
*
*
*
{{Portal bar, History of Science, National Register of Historic Places, Nuclear technology, Ohio, Chemistry
History of the Manhattan Project
History of Dayton, Ohio