Underground nuclear testingrefers to test detonations of nuclear weapons that are performed underground. When the device being tested is buried at sufficient depth, the explosion may be contained, with no release of radioactive materials to the atmosphere.
Plumbbob Rainier was detonated at 899ft underground on 19 September 1957.[17]The 1.7 kt explosion was the first to be entirely contained underground, producing no fallout.[20]The test took place in a 1,600[21] 2,000ft[22]horizontal tunnel in the shape of a hook.[22]The hook "was designed so explosive force will seal off the non-curved portion of tunnel nearest the detonation before gases and fission fragments can be vented around the curve of the tunnel's hook."[22]This test would become the prototype for larger, more powerful tests.[20]Rainier was announced in advance, so that seismic stations could attempt to record a signal.[23]Analysis of samples collected after the test enabled scientists to develop an understanding of underground explosions that "persists essentially unaltered today."[23]The information would later provide a basis for subsequent decisions to agree to the Limited Test Ban Treaty.[23]