The Dayton Project was a research and development project to produce polonium during World War II, as part of the larger Manhattan Project to build the first atomic bombs. Work took place at several sites in and around Dayton, Ohio. Those working on the project were ultimately responsible for creating the polonium-based modulated neutron initiators that were used to begin the chain reactions in the atomic bombs.
The Dayton Project began in 1943 when Monsanto's Charles Allen Thomas was recruited by the Manhattan Project to coordinate the plutonium purification and production work being carried out at various sites. Scientists at the Los Alamos Laboratory calculated that a plutonium bomb would require a neutron initiator. The best-known neutron sources used radioactive polonium and beryllium, 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, and the work moved there.
The Dayton Project developed techniques for extracting polonium from the lead dioxide ore in which it occurs naturally, and from bismuth targets that had been bombarded by neutrons in a nuclear reactor. Ultimately, polonium-based neutron initiators were used in both the gun-type Little Boy and the implosion-type Fat Man used in the atomic bombings of Hiroshima and Nagasaki respectively. The fact that polonium was used as an initiator was classified until the 1960s, but George Koval, a technician with the Manhattan Project's Special Engineer Detachment, penetrated the Dayton Project as a spy for the Soviet Union.
Background In December 1942, during World War II, Charles Allen Thomas, a chemist and director of research at Monsanto in St. Louis, joined the National Defense Research Committee (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, a member of the NDRC, and James B. Conant, the president of Harvard University 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 responsible for building an atomic bomb. 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, the director of the Los Alamos Laboratory 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 purification and production work being carried out at Los Alamos, the Metallurgical Laboratory in Chicago, Radiation Laboratory in Berkeley, and Ames Laboratory in Iowa. Chemistry and metallurgy at Los Alamos would be led by the youthful Joseph W. Kennedy.
At Los Alamos, physicist Robert Serber proposed that instead of relying on spontaneous fission, the chain reaction inside the atomic bomb should be triggered by a neutron initiator. The best-known neutron sources were radium-beryllium and polonium-beryllium. The latter was chosen, as polonium has a 138-day 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, 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. 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 and ammonium picrate, 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 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. 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 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. 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. 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 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 residues from the refinery in Port Hope, Ontario, left over after the removal of uranium and radium, were estimated to contain of polonium per metric ton. A curie 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 had patented a process in which the lead oxide was dissolved in hydrochloric acid: + 4 HCl → + + 2 The polonium could then be deposited on copper or nickel 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. 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 and hydrogen peroxide: + 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 and aluminum. 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 slurry, and shipped to the Manhattan District's Madison Square area to be dried and returned to Canada.
Production