David Greenglass (March 2, 1922 – July 1, 2014) was an atomic spy for the Soviet Union who worked on the Manhattan Project. He was briefly stationed at the Clinton Engineer Works uranium enrichment facility at Oak Ridge, Tennessee, and then worked at the Los Alamos laboratory in New Mexico from August 1944 until February 1946. He provided testimony that helped convict his sister and brother-in-law Ethel and Julius Rosenberg, who were executed for their spying activity. Greenglass served nine and a half years in prison. Wikipedia
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