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, located in Eastern Washington. 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 suggests that filters to remove the iodine were disabled during the Green Run.
The project gets its name from the processing of uranium at Hanford, WA in an open loop/water cooled nuclear reactor for the sole purpose of irradiating the Uranium-238 producing the fissile Plutonium-239. Due to other unwanted highly radioactive decay products being formed, normal batch processing would take place 83 to 101 days after reactor extraction to allow the radioactive isotopes to decay before extracting the fissile Plutonium-239 in a safe manner for the 30,000 nuclear weapons amassed and now MOX fuel during the cold war by the United States. For the Green Run test, a batch was fresh from the reactor with only a scheduled 16-day decay period and then was vented into the atmosphere premature. The unfiltered exhaust from the production facility was therefore much more radioactive than during a normal batch.
Oral history
Leland Fox says that his father was in the military and was bivouacked on the banks of the Wenatchee River during the Green Run:
…and people with radiation suits walked around and moved the little colored flags as the radiation was detected. The cooking was done outdoors and they slept near the beach. The Officers did not stay long except to give orders and drive away. Almost everyone that my father knew was there has died of cancer. My father had chronic lymphocytic leukemia and died from the complications of lung cancer. The Feds said that the leukemia can not be caused by iodine-131 but his doctor said that it most probably was.
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."