Louis Slotin (1910–1946) was a Canadian physicist and chemist who took part in the Manhattan Project, the secret U.S. program during World War II that developed the atomic bomb. As part of the Manhattan Project, Slotin performed experiments with uranium and plutonium cores to determine their critical mass values. During 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. He was rushed to a hospital, and died of radiation sickness nine days later on 30 May, the second victim of a criticality accident in history. Slotin was hailed as a hero by the United States government for reacting quickly enough to prevent the deaths of his colleagues due to the accident he caused. The accident and its aftermath have been dramatized in fictional accounts.