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Green Run Radiation Release

When the Soviet Union's reprocessing operations and plutonium production began at the Mayak site in 1948, the AEC wanted to estimate just how much plutonium was being produced. To do so, they conducted experiments at Hanford that involved purposely releasing emissions from the T Plant. They would take an air sample and compare it to air samples from the Myak site to estimate how much levels of plutonium production.

The experimental release took place on December 2 and 3, 1949. Weather conditions were favorable. Approximately 7,000 to 12,000 curies of iodine-131 and xenon-133 were released into the air.

To be able to conduct this release, Hanford officials had to deliberately disable the T Plants emission control filters. Initially some of the Hanford personnel had resisted the idea, but gave in to the urging Air Force.

After the release, the weather conditions changed for the worse. Due to rain, snow, and wind there were concentrated deposits of radionuclides northwest and southwest of Hanford. The levels of radionuclides in the thyroids of waterfowl increased sharply to approximately eight times the government allowed levels. Vegetation samples were taken in the Tri-Cities and Benton City immediately after the Green Run and continued until Christmas. The levels were significantly higher than normal. In Kennewick, Iodine-131 levels were nearly one thousand times the tolerable limit. Communities up to seventy miles from Hanford were showing higher than normal readings.

The Green Run experiment was a classified government secret until the 1980s. The Hanford Education League and the Spokesman_review newspaper made a Freedom of Information Act request. Although some of the information has been released a significant amount of details are still being withheld by the Air Force. Theses include the names of the officials who ordered the experiment and the intelligence unit that participated in the monitoring.

Although the amount of radionuclides released during the Green Run was small compared to previous routine plant releases, when details of it were declassified it caused great controversy. The Green Run was a decision that put government desires ahead of safety practices and the concern for the health of an unsuspecting public.


Gephart, R. E. Hanford: a Conversation about Nuclear Waste and Cleanup. Columbus, OH: Battelle, 2003.

Gerber, Michele Stenehjem. On the Home Front: the Cold War Legacy of the Hanford Nuclear Site. Lincoln: University of Nebraska, 2002.

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