#ThisDayInHistory The First Underground Nuclear Test Took Place
On this day in 1957, the United States detonates a 1.7-kiloton nuclear weapon in an underground tunnel at the Nevada Test Site (NTS), a 1,375-square-mile research center located 65 miles north of Las Vegas.
The 1.7 kt explosion was the first to be entirely contained underground, producing no fallout.
The test took place in a 1,600 – 2,000 ft (488 – 610 m) horizontal tunnel in the shape of a hook. 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".
This test would become the prototype for larger, more powerful tests. Rainier was announced in advance so that seismic stations could attempt to record a signal. Analysis of samples collected after the test enabled scientists to develop an understanding of underground explosions that "persists essentially unaltered today".
The effects of an underground nuclear test may vary according to factors including the depth and yield of the explosion, as well as the nature of the surrounding rock.
If the test is conducted at sufficient depth, the test is said to be contained, with no venting of gases or other contaminants to the environment. In contrast, if the device is buried at insufficient depth ("underburied"), then rock may be expelled by the explosion, forming a subsidence crater surrounded by ejecta, and releasing high-pressure gases into the atmosphere (the resulting crater is usually conical in profile, circular, and may range between tens to hundreds of meters in diameter and depth).
The energy of the nuclear explosion is released in one microsecond. In the following few microseconds, the test hardware and surrounding rock are vaporized, with temperatures of several million degrees and pressures of several million atmospheres.
Although there were early concerns about earthquakes arising as a result of underground tests, there is no evidence that this has occurred.[25] However, fault movements and ground fractures have been reported, and explosions often precede a series of aftershocks, thought to be a result of cavity collapse and chimney formation.
Signed in Moscow on August 5, 1963, by representatives of the United States, the Soviet Union, and the United Kingdom, the Limited Test Ban Treaty agreed to ban nuclear testing in the atmosphere, in space, and underwater. Due to the Soviet government's concern about the need for on-site inspections, underground tests were excluded from the ban.
108 countries would eventually sign the treaty, with the significant exception of China.
In 1974, the United States and the Soviet Union signed the Threshold Test Ban Treaty (TTBT) which banned underground tests with yields greater than 150 kilotons.
By the 1990s, technologies to monitor and detect underground tests had matured to the point that tests of one kiloton or over could be detected with high probability, and in 1996 negotiations began under the auspices of the United Nations to develop a comprehensive test ban.
The resulting Comprehensive Nuclear-Test-Ban Treaty was signed in 1996 by the United States, Russia, United Kingdom, France, and China.
#ThisDayInHistory
September 19, 1957