Editing Chagan (nuclear test) (section)

== Description ==
Chagan was the first and largest of the 124 detonations in the [[Nuclear Explosions for the National Economy]] program, designed to produce [[peaceful nuclear explosion]]s (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 (nuclear test)|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 [[kiloton]]s of [[Trinitrotoluene|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 {{cvt|408|m}} and is {{cvt|100|m}} 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".<ref>{{cite web |url=http://www.nuclearfiles.org/menu/library/treaties/partial-test-ban/trty_partial-test-ban_1963-10-10.htm |title=Library: Treaties: Partial Test Ban Treaty, October 10, 1963 |publisher=Nuclear Files |date=1963-10-10 |accessdate=2014-06-01 |archive-url=https://web.archive.org/web/20150404001527/http://www.nuclearfiles.org/menu/library/treaties/partial-test-ban/trty_partial-test-ban_1963-10-10.htm# |archive-date=2015-04-04 |url-status=dead }}</ref>

The device itself was a [[Nuclear weapon design#Clean bombs|low fission-fraction design]],<ref name=SovPlow>{{cite report |author=M. D. Nordyke |date=26 July 2000 |title=The Soviet Program for Peaceful Uses of Nuclear Explosions |url=https://www.osti.gov/biblio/793554-soviet-program-peaceful-uses-nuclear-explosions |publisher=Lawrence Livermore National Lab |page=14 |osti= 793554|docket=UCRL-ID-124410-Rev-2 |access-date= |quote="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."}}</ref> 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.<ref>{{cite web |url=https://nuclearweaponarchive.org/Nwfaq/Nfaq4-5.html#Nfaq4.5.4 |title=Thermonuclear Weapon Designs - 4.5.4 Minimum Residual Radiation (MRR or "Clean") Designs  |last=Sublette |first=Carey |date= |website=Nuclear Weapon Archive |publisher= |access-date=9 February 2022 |quote=}}</ref> The device had a primary (fission) stage of {{convert|5|to|7|ktTNT}} and a purely thermonuclear secondary stage.<ref name=SovPlow/>

The photo of the Chagan shot is occasionally confused with that of the Soviet ''[[Joe 1]]'' test. The [[:ru:Файл:Chagan.jpg|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.<ref name="Rhodes 1995">{{Cite Q | Q105755363 | last1 = Rhodes | first1 = Richard | author-link1 = Richard Rhodes | df = dmy-all | via = [[Internet Archive]] }}</ref><ref name="Holloway">{{cite book| last1 = Holloway | first1 = David | title = Stalin and the Bomb: The Soviet Union and Atomic Energy, 1939-1956 | language = en | edition = 1st | publisher = [[Yale University Press]]| date = 1994 | isbn = 978-0300060560 | oclc = 470165274 |ol = OL1084400M | df = dmy-all }}</ref>