page_title: Louis Slotin
section_title: Radiation dosage
hierarchical_section_title: Louis Slotin / Work at Los Alamos / Radiation dosage
caption_attribution_description: English: A sketch of Louis Slotin’s criticality accident (1946-05-21) used by doctors to determine exposure of those in the room at the time. Français&#160;: Dessin représentant Louis Slotin et les personnes présentes dans la pièce au moment de l'accident du 21 mai 1946. Un croquis utilisé par les médecins pour déterminer la quantité de radiation à laquelle était exposé chaque personne dans la pièce pendant l'accident. Polski: Szkic sytuacyjny incydentu w Los Alamos.
context_page_description: Louis Alexander Slotin was a Canadian physicist and chemist who took part in the Manhattan Project. He was born and raised in the North End of Winnipeg, Manitoba. After earning both his Bachelor of Science and Master of Science degrees from the University of Manitoba, Slotin attended King's College London, where he obtained his doctorate in physical chemistry in 1936. Afterwards, he joined the University of Chicago as a research associate to help design a cyclotron. In 1942, he was invited to participate in the Manhattan Project.
  As part of the Manhattan Project, Slotin performed experiments with uranium and plutonium cores to determine their critical mass values. After World War II, Slotin continued his research at Los Alamos National Laboratory. On 21 May 1946, Slotin accidentally began a fission reaction, which released a burst of hard radiation. Slotin was rushed to the hospital, and died nine days later on 30 May, the victim of the second criticality accident in history, following the death of Harry Daghlian, who had been exposed to radiation by the same core that killed Slotin.
context_section_description: The radiation doses received in these two accidents are not known with any accuracy. A large part of the dose was due to neutron radiation, which could not be measured by dosimetry equipment of the day. The available film badges were not worn by personnel during the accident, and badges that were supposed to be planted under tables in case of disasters like these were not found. Disaster badges hung on the walls provided some useful data about gamma radiation.
  A "tentative" estimate of the doses involved was made in 1948, based on dozens of assumptions, some of which are now known to be incorrect. In the absence of personal dosimetry badges, the study authors relied on measurements of sodium activation in the victims' blood and urine samples as their primary source of data. This activation would have been caused by neutron radiation, but they converted all doses to equivalent doses of gamma or X-ray radiation. They concluded that Daghlian and Slotin had probably received doses equivalent to 290 and 880 rem, respectively, of gamma rays. Minimum and maximum estimates varied from about 50% to 200% of these values. The authors also calculated doses equivalent to a mix of soft 80 keV X-rays and gamma rays, which they believed gave a more realistic picture of the exposure than the gamma equivalent. In this model the equivalent X-ray doses were much higher, but would be concentrated in the tissues facing the source, whereas the gamma component penetrated the whole body. Slotin's equivalent dose was estimated to be 1930 R (roentgen) of X-ray with 114 R of gamma, while Daghlian's equivalent dose was estimated to be 480 R of X-ray with 110 R of gamma.  Five hundred rem is usually a fatal dose for humans.
  In modern times dosimetry is done very differently. Equivalent doses would not be reported in roentgen; they would be calculated with different weighting factors, and they are not considered as relevant to acute radiation syndrome as absorbed doses. Recent documents have made various interpretations of Slotin's dose, ranging from 287 rad to 21 sievert. Based on citations and supporting reasoning, the most reliable estimate may be a 1978 Los Alamos memo which suggested 10 Gy(n) + 1.14 Gy(γ) for Slotin and 2 Gy(n) + 1.1 Gy(γ) for Daghlian. These doses are consistent with the symptoms they experienced.
caption: A sketch used by doctors to determine the amount of radiation to which each person in the room had been exposed during the excursion
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