What is Radioactive contamination?
[[Image:Hanford N Reactor adjusted.jpg|thumb|300px|right|The [[Hanford site]] represents two-thirds of the United States' [[high-level radioactive waste]] by volume. [[Nuclear reactor]]s line the riverbank at the Hanford Site along the [[Columbia River]] in January 1960.]] [[File:Fukushima I by Digital Globe.jpg|thumb|As of 2013, the [[Fukushima nuclear disaster]] site remains [[Radiation effects from Fukushima Daiichi nuclear disaster|highly radioactive]]. About 160,000 people still live in temporary housing. Some land will be unfarmable for centuries. The [[Fukushima disaster cleanup|difficult cleanup job]] will take 40 or more years, and cost tens of billions of dollars.<ref>{{cite web |url=http://www.guardian.co.uk/commentisfree/2013/mar/12/fukushima-nuclear-accident-lessons-for-us |title=Two years on, America hasn't learned lessons of Fukushima nuclear disaster |author=Richard Schiffman |date=12 March 2013 |work=The Guardian }}</ref><ref>{{cite web |url=https://www.nytimes.com/2011/06/02/world/asia/02japan.html?_r=1&ref=world |title=Report Finds Japan Underestimated Tsunami Danger |author=Martin Fackler |date=June 1, 2011 |work=New York Times }}</ref>]] [[File:Wfm sts overview.png|thumb|The 18,000 km<sup>2</sup> expanse of the [[Semipalatinsk Test Site]] (indicated in red), which covers an area [[the size of Wales]]. The Soviet Union conducted 456 nuclear tests at Semipalatinsk from 1949 until 1989 with little regard for their effect on the local people or environment. The full impact of radiation exposure was hidden for many years by Soviet authorities and has only come to light since the test site closed in 1991.<ref>{{cite web |url=http://thebulletin.org/lasting-toll-semipalatinsks-nuclear-testing |title=The lasting toll of Semipalatinsk's nuclear testing |author=Togzhan Kassenova |date=28 September 2009 |work=Bulletin of the Atomic Scientists }}</ref>]] [[File:Logo iso radiation.svg|thumb|right|2007 ISO [[radioactivity]] danger symbol. The red background is intended to convey urgent danger, and the sig