Louis Slotin
Louis Alexander Slotin was a Canadian physicist and chemist who took part in the Manhattan Project. Born and raised in the North End of Winnipeg, Manitoba, Slotin earned both his Bachelor of Science and Master of Science degrees from the University of Manitoba, before obtaining his doctorate in physical chemistry at King's College London in 1936. Afterwards, he joined the University of Chicago as a research associate to help design a cyclotron.
In 1942, Slotin was invited to participate in the Manhattan Project, and subsequently performed experiments with uranium and plutonium cores to determine their critical mass values. After World War II, he continued his research at Los Alamos National Laboratory in New Mexico. On 21 May 1946, he accidentally triggered a supercritical nuclear chain reaction, which released a burst of hard radiation. He was rushed to the hospital and died nine days later on 30 May. Slotin had become the second fatal victim of a criticality accident in history, following Harry Daghlian, who had died of a related accident with the same plutonium "demon core" the previous year.
Slotin was hailed as a hero by the United States government for reacting quickly enough to prevent the deaths of his colleagues. However, Slotin had ignored safety protocols for the experiment causing the accident. Therefore some physicists stated that Slotin's behavior preceding the accident was reckless and that his death was preventable. The accident and its aftermath have been dramatized in several fictional and non-fictional accounts.
Early life
Louis Slotin was the first of three children born to Israel and Sonia Slotin, Yiddish-speaking Jewish refugees who had fled the pogroms of Russia to Winnipeg, Manitoba. He grew up in the North End neighborhood of Winnipeg, an area with a large concentration of Eastern European immigrants. From his early days at Machray Elementary School through his teenage years at St. John's High School, Slotin was academically exceptional. His younger brother, Sam, later remarked that his brother "had an extreme intensity that enabled him to study long hours."At age 16, Slotin entered the University of Manitoba to pursue a degree in science. During his undergraduate years, he received a University Gold Medal in both physics and chemistry. Slotin received a B.Sc. degree in geology from the university in 1932 and a M.Sc. degree in 1933. With the assistance of one of his mentors, he obtained a fellowship to study at King's College London under the supervision of Arthur John Allmand, the chair of the chemistry department, who specialized in the field of applied electrochemistry and photochemistry.
King's College London
While at King's College London, Slotin distinguished himself as an amateur boxer by winning the college's amateur bantamweight boxing championship. Later, he gave the impression that he had fought for the Spanish Republic and trained to fly a fighter with the Royal Air Force. Author Robert Jungk recounted in his book Brighter than a Thousand Suns: A Personal History of the Atomic Scientists, an early history of the Manhattan Project, that Slotin "had volunteered for service in the Spanish Civil War, more for the sake of the thrill of it than on political grounds. He had often been in extreme danger as an anti-aircraft gunner." During an interview years later, Sam stated that his brother had gone "on a walking tour in Spain" and he "did not take part in the war" as previously thought.Slotin earned a Ph.D. in physical chemistry from King's College London in 1936. He won a prize for his thesis entitled "An Investigation into the Intermediate Formation of Unstable Molecules During some Chemical Reactions." Afterwards, he spent six months working as a special investigator for Dublin's Great Southern Railways, testing the Drumm nickel-zinc rechargeable batteries used on the Dublin–Bray line.
Career
University of Chicago
In 1937, after he unsuccessfully applied for a job with Canada's National Research Council, the University of Chicago accepted Slotin as a research associate. There, he gained his first experience with nuclear chemistry, helping to build the first cyclotron in the midwestern United States. The job paid poorly and Slotin's father had to support him for two years. From 1939 to 1940, Slotin collaborated with Earl Evans, the head of the university's biochemistry department, to produce radiocarbon from the cyclotron. While working together, the two men also used carbon11 to demonstrate that plant cells had the capacity to use carbon dioxide for carbohydrate synthesis, through carbon fixation.Slotin might have been present at the start-up of Enrico Fermi's "Chicago Pile-1", the first nuclear reactor, on 2 December 1942; the accounts of the event do not agree on this point. During this time, he also contributed to several papers in the field of radiobiology. His expertise on the subject garnered the attention of the United States government, and as a result he was invited to join the Manhattan Project, an effort to develop an atomic bomb. Slotin worked on the production of plutonium under future Nobel laureate Eugene Wigner at the university and later at the Oak Ridge National Laboratory in Oak Ridge, Tennessee. He moved to the Los Alamos National Laboratory in New Mexico in December 1944 to work in the bomb physics group of Robert Bacher.
Work at Los Alamos
At Los Alamos, Slotin's duties consisted of dangerous criticality testing, first with uranium in Otto Robert Frisch's experiments, and later with plutonium cores. Criticality testing involved bringing masses of fissile materials to near-critical levels to establish their critical mass values. Scientists referred to this flirting with the possibility of a nuclear chain reaction as "tickling the dragon's tail", based on a remark by physicist Richard Feynman comparing the experiments to "tickling the tail of a sleeping dragon". On 16 July 1945, Slotin assembled the core for Trinity, the first detonated atomic device, and became known as the "chief armorer of the United States" for his expertise in assembling nuclear weapons. Slotin received two small circular lead and silver commemorative pins for his work on the project.In the winter of 1945–1946, Slotin shocked some of his colleagues with a bold action by repairing an instrument under water inside the Clinton Pile while it was operating, rather than wait an extra day for the reactor to be shut down. He did not wear his dosimetry badge, but his dose was estimated to be at least 100 roentgen. A dose of 1 Gy can cause nausea and vomiting in 10% of cases, but is generally survivable.
Harry Daghlian's death
On 21 August 1945, laboratory assistant Harry Daghlian, one of Slotin's close colleagues, was performing a criticality experiment when he accidentally dropped a heavy tungsten carbide brick onto a plutonium–gallium alloy bomb core, later nicknamed demon core, which would later also kill Slotin. The 24-year-old Daghlian was irradiated with a large dose of neutron radiation. Later estimates suggested that this dose might not have been fatal on its own, but he then received additional delayed gamma radiation and beta burns while disassembling his experiment. He quickly collapsed with acute radiation poisoning and died 25 days later in the Los Alamos base hospital.Planned return to teaching
After World War II, Slotin expressed growing disdain for his personal involvement in the project. He remarked, "I have become involved in the Navy tests, much to my disgust." Unfortunately for Slotin, his participation at Los Alamos was still required because, as he said, "I am one of the few people left here who are experienced bomb putter-togetherers." He looked forward to resuming teaching and research into biophysics and radiobiology at the University of Chicago. He began training a replacement, Alvin C. Graves, to take over his role at Los Alamos.Criticality accident
On 21 May 1946, with seven colleagues watching, Slotin performed an experiment that involved the creation of one of the first steps of a fission reaction by placing two half-spheres of beryllium around a plutonium core. The experiment used the same plutonium core that had irradiated Daghlian, later called the "demon core" for its role in the two accidents. Slotin grasped the upper 228.6 mm beryllium hemisphere with his left hand through a thumb hole at the top while he maintained the separation of the half-spheres using the blade of a screwdriver. The standard protocol was to use shims between the halves, as allowing them to close completely could result in the instantaneous formation of a critical mass and a lethal power excursion.By Slotin's own unapproved protocol, the shims were not used. The top half of the reflector was resting directly on the bottom half at one point, while 180 degrees from this point a gap was maintained by the blade of a flat-tipped screwdriver in Slotin's hand. The size of the gap between the reflectors was changed by twisting the screwdriver. Slotin, who was given to bravado, became the local expert, performing the test on almost a dozen occasions, often in his trademark blue jeans and cowboy boots in front of a roomful of observers. Enrico Fermi reportedly told Slotin and others they would be "dead within a year" if they continued performing the test in that manner. Scientists referred to this flirtation with a nuclear chain reaction as "tickling the dragon's tail", based on a remark by physicist Richard Feynman.
At 3:20 p.m., the screwdriver slipped and the upper beryllium hemisphere fell, causing a "prompt critical" reaction and a burst of hard radiation. Those present saw the blue glow of ionized air and felt a wave of heat. Slotin experienced a sour taste in his mouth and an intense burning sensation in his left hand. He jerked his left hand upward, lifting the upper beryllium hemisphere, ending the reaction, and dropped it to the floor. He had already been exposed to a lethal dose of neutron radiation, however.
At the time of the accident, dosimetry badges were in a locked box about from where the reaction occurred. Realizing that no one in the room had their film badges on, "immediately after the accident Dr. Slotin asked Dr. Raemer E. Schreiber to have the badges taken from the lead box and placed on the critical assembly". This peculiar suggestion was of no value for determining the actual doses received by the men in the room and put Schreiber at "great personal risk" of additional exposure. A report later concluded that a heavy dose of radiation may produce vertigo and can leave a person "in no condition for rational behavior." As soon as Slotin left the building he vomited, a common reaction from exposure to extremely intense ionizing radiation. Slotin's colleagues rushed him to the hospital, but the radiation damage was irreversible.
The six other men present at the accident were Alvin Cushman Graves, Samuel Allan Kline, Marion Edward Cieslicki, Dwight Smith Young, Theodore P. Perlman, and Pvt. Patrick J. Cleary. By 25 May 1946, four of these seven men had been discharged from the hospital. The United States Army physician responsible for the Los Alamos base hospital, Captain Paul Hageman, said that Slotin's, Graves', Kline's and Young's "immediate condition is satisfactory."