The "Green Run" was a secret U.S. Government release of radioactive fission products on December 2–3, 1949, at the Hanford Site plutonium production facility. Radioisotopes released at that time were supposed to be detected by U.S. Air Force reconnaissance. Freedom of Information Act (FOIA) requests to the U.S. Government have revealed some of the details of the experiment. Sources cite 5,500 to 12,000 curies (200 to 440 TBq) of iodine-131 released, and an even greater amount of Xenon-133. The radiation was distributed over populated areas, and caused the cessation of intentional radioactive releases at Hanford until 1962 when more experiments commenced.
There are some indications contained in the documents released by the FOIA requests that many other tests were conducted in the 1940s prior to the Green Run, although the Green Run was a particularly large test. Evidence suggest that filters to remove the iodine were disabled during the Green Run.
The project gets its name from the processing of uranium at Hanford. Due to the higher radioactivity involved, batch processing waited 83 to 101 days to allow the radioactive isotopes to decay. For the Green Run test, a batch was run with only a 16 day cooling period. The unfiltered exhaust from the production facility was therefore much more radioactive than during a normal batch.
Oral history 
Health Physicist Carl C. Gamertsfelder, Ph.D. described his recollections as to the reasons for the Green Run by attributing it to the intentions of the Air Force to be able to track Soviet releases. "Herb Parker called me to request that I, and the groups that I supervised, cooperate with the Air Force in the conduct of an experiment which became known as the Green Run... And we didn't recommend, we wouldn't have recommended, that they operate it. We told them that. They wanted to run anyway, and they did run."
Modern Culture 
In the 2012 video game Call of Duty: Black Ops II, there is a 'Zombies' mode map called Green Run, which is set at Hanford; the layout of the map is nearly identical to that of Hanford.It has a Bus Depot, a Diner, a Farm, a Power Station and a Town.
See also 
- The Release of Radioactive Materials from Hanford: 1944-1972
- Miller, Richard L (1991). Under the Cloud: The Decades of Nuclear Testing. The Woodlands, Texas: Two Sixty Press. p. 71. ISBN 0-02-921620-6. (See Google Books)
- Goliszek, Andrew (2003). In The Name of Science. New York: St. Martin's Press. ISBN 978-0-312-30356-3. pp. 130-131.
- "New documents reveal story behind green run". WISE News Communique. October 30, 1992.
- Oral History of Health Physicist Carl C. Gamertsfelder, Ph.D., DOE/EH-0467, HUMAN RADIATION STUDIES: REMEMBERING THE EARLY YEARS. Conducted January 19, 1995, United States Department of Energy, Office of Human Radiation Experiments, September 1995.