Chagan (nuclear test)
Encyclopedia
Chagan was a Soviet
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 underground nuclear test conducted at the Semipalatinsk Test Site
Semipalatinsk Test Site
The Semipalatinsk Test Site was the primary testing venue for the Soviet Union's nuclear weapons. It is located on the steppe in northeast Kazakhstan , south of the valley of the Irtysh River...

 on January 15, 1965.

Chagan was the first and largest of the 124 detonations in the Nuclear Explosions for the National Economy
Nuclear Explosions for the National Economy
Nuclear Explosions for the National Economy , was a Soviet program to investigate peaceful nuclear explosions . It was analogous to the US program Operation Plowshare....

 program, designed to produce peaceful nuclear explosions
Peaceful nuclear explosions
Peaceful nuclear explosions are nuclear explosions conducted for non-military purposes, such as activities related to economic development including the creation of canals...

 (PNEs) for earth-moving purposes. The concept of using PNEs to create artificial lakes, harbors and canals was modeled after the US's Operation Plowshare
Operation Plowshare
Project Plowshare was the overall United States term for the development of techniques to use nuclear explosives for peaceful construction purposes...

, which conducted the first peaceful nuclear explosion (the 104 kt Sedan
Sedan (nuclear test)
Storax Sedan was a shallow underground nuclear test conducted in Area 10 of Yucca Flat at the Nevada National Security Site on 6 July 1962 as part of Operation Plowshare, a program to investigate the use of nuclear weapons for mining, cratering, and other civilian purposes...

 shallow cratering test) at the Nevada Test Site
Nevada Test Site
The Nevada National Security Site , previously the Nevada Test Site , is a United States Department of Energy reservation located in southeastern Nye County, Nevada, about northwest of the city of Las Vegas...

 in July 1962.

Described as a "near clone" of the Sedan shot, Chagan's yield was the equivalent of 140 kilotons of TNT and sought to produce a large conical crater suitable for a lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

. The site was a dry bed of the Chagan River at the edge of the Semipalatinsk Test Site, and was chosen such that the lip of the crater would dam the river during its high spring flow. The resultant lake has a diameter of 408 meters (1,338 ft) and is 100 meters (328 ft) deep.

Shallow subsurface (open) cratering explosions such as Sedan or Chagan release a great deal of steam and pulverized rock along with approximately 20% of the bomb's normal fission products into the atmosphere. Although the vast majority of this fallout is deposited in the general area of the test, it also produces a small but measurable radioactive plume, which in Chagan's case was detected over Japan and initially prompted complaints from the US that the Soviets were violating the provisions of the October 1963 Limited Test Ban Treaty, which banned atmospheric tests and any vented (or "open") subsurface detonation which caused "radioactive debris to be present outside the territorial limits of the State under whose jurisdiction or control such explosion is conducted." The matter was eventually abandoned, and in any case all subsequent Soviet shots were smaller.

The photo of the Chagan shot is occasionally confused with that of the Soviet Joe 1
Joe 1
The RDS-1 , also known as First Lightning , was the Soviet Union's first nuclear weapon test. In the west, it was code-named Joe-1, in reference to Joseph Stalin. It was test-exploded on 29 August 1949, at Semipalatinsk, Kazakh SSR, after a top-secret R&D project...

test. The correct image shows a squat, ground-level cloud similar to the Sedan shot rather than the tall mushroom cloud
Mushroom cloud
A mushroom cloud is a distinctive pyrocumulus mushroom-shaped cloud of condensed water vapor or debris resulting from a very large explosion. They are most commonly associated with nuclear explosions, but any sufficiently large blast will produce the same sort of effect. They can be caused by...

 of the tower-detonated Joe-1. (Richard Rhodes's 1995 Dark Sun: The Making of the Hydrogen Bomb and David Holloway's 1994 Stalin and the Bomb).

Lake Chagan

Lake Chagan or Lake Balapan, Kazakhstan
Kazakhstan
Kazakhstan , officially the Republic of Kazakhstan, is a transcontinental country in Central Asia and Eastern Europe. Ranked as the ninth largest country in the world, it is also the world's largest landlocked country; its territory of is greater than Western Europe...

, is a lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 created by the Chagan nuclear test. It is roughly 10000000 cubic metre.

The area is still radioactive, and has been called the "Atomic Lake." As at the Trinity site of the first United States nuclear weapon test in Alamogordo, New Mexico
Alamogordo, New Mexico
Alamogordo is the county seat of Otero County and a city in south-central New Mexico, United States. A desert community lying in the Tularosa Basin, it is bordered on the east by the Sacramento Mountains. It is the nearest city to Holloman Air Force Base. The population was 35,582 as of the 2000...

, the exposed rock was melted into a glassy substance.

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