Chagan (nuclear test)

1965 Soviet underground nuclear test

Chagan

Information
Country| Soviet Union
Test site| Semipalatinsk Test Site
Date| January 15, 1965
Number of tests| 124
Test type| Underground test
Device type| Thermonuclear
Max. yield| Total yield 140 kilotons of TNT (590 TJ)
Test chronology

<- Test 219

None ->

Chagan (Чага́н) was a Soviet underground nuclear test conducted at the Semipalatinsk Test Site on January 15, 1965.

## Description

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Chagan was the first and largest of the 124 detonations in the Nuclear Explosions for the National Economy program, designed to produce peaceful nuclear explosions (PNEs) for earth-moving purposes. The concept of using PNEs to create artificial lakes, harbors and canals was modeled after a United States program, Project Plowshare, which conducted the first peaceful nuclear explosion (the 104 kt Sedan shallow cratering test) at the Nevada Test Site 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. The site was a dry bed of the Chagan River (tributary of Irtysh 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 m (1,339 ft) and is 100 m (330 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 device's fission products into the atmosphere. Although the vast majority of this fallout was deposited in the general area of the test, it also produced 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".[1]

The device itself was a low fission-fraction design,[2] meaning it produced only a small portion of its yield from fission and hence produced less fallout than a military device generally designed for low weight and/or size, and not fallout considerations.[3] The device had a primary (fission) stage of 5 to 7 kilotonnes of TNT (21 to 29 TJ) and a purely thermonuclear secondary stage.[2]

The photo of the Chagan shot is occasionally confused with that of the Soviet Joe 1 test. The correct image shows a squat, ground-level cloud similar to the Sedan shot rather than the tall mushroom cloud of the tower-detonated Joe-1.[4][5]

## Lake Chagan

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Main article: Lake Chagan

Lake Chagan or Lake Shagan,[6] also known as Balapan, is a lake created at the confluence of rivers Shagan and Ashchysu by the Chagan nuclear test roughly 10,000,000 m3 (8,100 acre⋅ft) in size, 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, the exposed rock and sand was melted into a glassy substance called trinitite.

## See also

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* Sedan (nuclear test) – an American cratering detonation

## References

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1. ^ "Library: Treaties: Partial Test Ban Treaty, October 10, 1963". Nuclear Files. 1963-10-10. Archived from the original on 2015-04-04. Retrieved 2014-06-01.
2. ^ a b M. D. Nordyke (26 July 2000). The Soviet Program for Peaceful Uses of Nuclear Explosions (Report). Lawrence Livermore National Lab. p. 14\. OSTI 793554. UCRL-ID-124410-Rev-2. "The nuclear explosive used for the Chagan test was reported to be a low-fission design, which had a pure thermonuclear secondary driven by a fission primary with a yield of about 5–7 kt."
3. ^ Sublette, Carey. "Thermonuclear Weapon Designs - 4.5.4 Minimum Residual Radiation (MRR or "Clean") Designs". Nuclear Weapon Archive. Retrieved 9 February 2022.
4. ^ Rhodes, Richard (1 August 1995). Dark Sun: The Making of the Hydrogen Bomb. Simon & Schuster. ISBN 978-0-68-480400-2. LCCN 95011070. OCLC 456652278. OL 7720934M. Wikidata Q105755363 - via Internet Archive.
5. ^ Holloway, David (1994). Stalin and the Bomb: The Soviet Union and Atomic Energy, 1939-1956 (1st ed.). Yale University Press. ISBN 978-0300060560. OCLC 470165274. OL 1084400M.
6. ^ "M-44 Topographic Chart (in Russian)". Retrieved 4 October 2022.

## External links

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* The Soviet program for peaceful uses of nuclear weapons
* On the Soviet nuclear program

49°56′7″N 79°0′30″E﻿ / ﻿49.93528°N 79.00833°E﻿ / 49.93528; 79.00833