Green Run

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.^[1] Sources cite 5,500 to 12,000 curies (200 to 440 TBq) of iodine-131 released,^[1][2][3] 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, Washington until 1962, when more experiments commenced.^[3]

The project gets its name from the processing of uranium at the Hanford B Reactor in an open-loop water-cooled nuclear reactor used to irradiate uranium-238 to make fissile plutonium-239.^[4] 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.^[1] 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 prematurely.^[1] The unfiltered exhaust from the production facility was therefore much more radioactive than during a normal batch.^[1]

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.^[3][5]