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By 1963, the citizens of the United States as well as others in the international community were becoming increasingly aware of the health implications, environmental risks, and national security risks of nuclear testing. The United States, United Kingdom, and the Soviet Union signed the Partial Test Ban Treaty in August 1963. This treaty established a mandate that banned nuclear testing in the atmosphere, outer space, or under water. It served to reduce the risks associated with testing as well as to quell the international arms race. However, testing of nuclear devices at underground sites experienced a rapid growth in the years ahead, not without its risks.
Baneberry was a 10-kiloton device test conducted at the Yucca Flats area of the Nevada Test Site as part of Operation Emery on December 18, 1970. The goal was to conduct an underground test of a device from a depth of 270 meters for weapons development. The blast that resulted caused an eruption from underground that caused a radioactive vapor cloud that climbed as high as three kilometers into the sky. The fallout that rained down affected 86 workers at the site, killing two of the workers within four years as the result of Leukemia.
An initial report by the U.S. Atomic Energy Agency Commission concluded that the primary cause of the venting was “an unexpected and unrecognized abnormally high water content in the medium surrounding the detonation point.” A later report by the Office of Technology Assessment in 1988 cited three combined causes for the incident: “water-saturated clay, a buried scarp of hard rock, and a nearby fault. It is thought that the weak, water-saturated clay was unable to support the containment structure: the hard scarp strongly reflected back the energy of the explosion increasing its force; and the nearby fault provided a pathway that gases could travel along. All three of these features seem to have contributed to the venting.” The incident was called one of the worst nuclear venting disasters in history by TIME Magazine, and the vapor cloud was reportedly spotted as far away as Las Vegas, 75 miles away.