Editing Nuclear technology (section)

== Nuclear weapons ==
{{main|Nuclear weapon}}
A nuclear weapon is an explosive device that derives its destructive force from [[nuclear reaction]]s, either [[nuclear fission|fission]] or a combination of fission and [[nuclear fusion|fusion]]. Both reactions release vast quantities of energy from relatively small amounts of matter. Even small nuclear devices can devastate a city by blast, fire and radiation. Nuclear weapons are considered [[weapons of mass destruction]], and their use and control has been a major aspect of international policy since their debut.

The [[nuclear weapon design|design of a nuclear weapon]] is more complicated than it might seem. Such a weapon must hold one or more subcritical fissile masses stable for deployment, then induce criticality (create a critical mass) for detonation. It also is quite difficult to ensure that such a chain reaction consumes a significant fraction of the fuel before the device flies apart. The procurement of a [[nuclear fuel]] is also more difficult than it might seem, since sufficiently unstable substances for this process do not currently occur naturally on Earth in suitable amounts.

One [[isotope]] of [[uranium]], namely uranium-235, is naturally occurring and sufficiently unstable, but it is always found mixed with the more stable isotope uranium-238. The latter accounts for more than 99% of the weight of natural uranium. Therefore, some method of [[isotope separation]] based on the weight of three [[neutrons]] must be performed to [[Enriched uranium|enrich]] (isolate) uranium-235.

Alternatively, the element [[plutonium]] possesses an isotope that is sufficiently unstable for this process to be usable. Terrestrial plutonium does not currently occur naturally in sufficient quantities for such use,<ref>"Oklo Fossil Reactors". {{cite web |url=http://www.oklo.curtin.edu.au/index.cfm |title=Oklo Fossil Reactors |access-date=2008-01-15 |url-status=dead |archive-url=https://web.archive.org/web/20071218194159/http://www.oklo.curtin.edu.au/index.cfm |archive-date=2007-12-18 }} Curtin University of Technology. Archived from the original on 18 December 2007. Retrieved 15 January 2008.</ref> so it must be manufactured in a [[nuclear reactor]].

Ultimately, the [[Manhattan Project]] manufactured nuclear weapons based on each of these elements. They detonated the first nuclear weapon in a [[Nuclear weapons testing|test]] code-named "[[Trinity test|Trinity]]", near [[Alamogordo]], [[New Mexico]], on July 16, 1945. The test was conducted to ensure that the [[Nuclear weapon design#Implosion-type weapon|implosion method]] of detonation would work, which it did. A uranium bomb, [[Little Boy]], was dropped on the [[Japan]]ese city [[Hiroshima]] on August 6, 1945, followed three days later by the plutonium-based [[Fat Man]] on [[Nagasaki, Nagasaki|Nagasaki]]. In the wake of unprecedented devastation and casualties from a single weapon, the Japanese government soon surrendered, ending [[World War II]].

Since [[Atomic bombings of Hiroshima and Nagasaki|these bombings]], no nuclear weapons have been deployed offensively. Nevertheless, they prompted an [[arms race]] to develop increasingly destructive bombs to provide a [[nuclear deterrent]]. Just over four years later, on August 29, 1949, the [[Russia and weapons of mass destruction|Soviet Union]] detonated its [[RDS-1|first fission weapon]]. The [[Nuclear weapons and the United Kingdom|United Kingdom]] followed on October 2, 1952; [[France and weapons of mass destruction|France]], on February 13, 1960; and [[People's Republic of China and weapons of mass destruction|China]] component to a nuclear weapon. Approximately half of the deaths from [[Atomic bombings of Hiroshima and Nagasaki|Hiroshima and Nagasaki]] died two to five years afterward from radiation exposure.<ref name="rerf-deaths">{{cite web|url = http://www.rerf.or.jp/general/qa_e/qa1.html|title = Frequently Asked Questions #1|publisher = [[Radiation Effects Research Foundation]]|access-date = 2007-09-18|url-status = dead|archive-url = https://web.archive.org/web/20070919143939/http://www.rerf.or.jp/general/qa_e/qa1.html|archive-date = 2007-09-19}}</ref><ref name="pubmedcentral.nih.gov">{{cite journal|pmc=33859|title=The somatic effects of exposure to atomic radiation: The Japanese experience, 1947–1997|first=William J.|last=Schull|date=12 May 1998|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=95|issue=10|pages=5437–5441|pmid=9576900|doi=10.1073/pnas.95.10.5437|bibcode=1998PNAS...95.5437S|doi-access=free}}</ref> A [[radiological weapon]] is a type of nuclear weapon designed to distribute hazardous nuclear material in enemy areas. Such a weapon would not have the explosive capability of a fission or fusion bomb, but would kill many people and contaminate a large area. A radiological weapon has never been deployed. While considered useless by a conventional military, such a weapon raises concerns over [[nuclear terrorism]].

There have been [[List of nuclear tests|over 2,000 nuclear tests]] conducted since 1945. In 1963, all nuclear and many non-nuclear states signed the [[Limited Test Ban Treaty]], pledging to refrain from [[Nuclear weapons testing|testing nuclear weapons]] in the atmosphere, underwater, or in [[outer space]]. The treaty permitted [[underground nuclear testing]]. France continued atmospheric testing until 1974, while China continued up until 1980. The last underground test by the United States was in 1992, the Soviet Union in 1990, the United Kingdom in 1991, and both France and China continued testing until 1996. After signing the [[Comprehensive Test Ban Treaty]] in 1996 (which had as of 2011 not entered into force), all of these states have pledged to discontinue all nuclear testing. Non-signatories [[India and weapons of mass destruction|India]] and [[Pakistan and weapons of mass destruction|Pakistan]] last tested nuclear weapons in 1998.

Nuclear weapons are the most destructive weapons known - the archetypal [[weapons of mass destruction]]. Throughout the [[Cold War]], the opposing powers had huge nuclear arsenals, sufficient to kill hundreds of millions of people. Generations of people grew up under the shadow of nuclear devastation, portrayed in films such as ''[[Dr. Strangelove]]'' and ''[[The Atomic Cafe]]''.

However, the tremendous energy release in the detonation of a nuclear weapon also suggested the possibility of a new energy source.