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Nuclear fallout
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==Types of fallout== Fallout comes in two varieties. The first is a small amount of carcinogenic material with a long [[half-life]]. The second, depending on the height of detonation, is a large quantity of radioactive dust and sand with a short half-life. All nuclear explosions produce [[Nuclear fission|fission]] products, un-fissioned nuclear material, and weapon residues vaporized by the heat of the fireball. These materials are limited to the original mass of the device, but include [[radionuclide|radioisotopes]] with long lives.<ref name="effects2005">{{cite book |last1=National Research Council |title=Effects of Nuclear Earth-Penetrator and Other Weapons |date=2005 |publisher=National Academies Press |isbn=9780309096737 |url=https://www.nap.edu/read/11282/chapter/7 |access-date=4 December 2018 |archive-date=15 May 2021 |archive-url=https://web.archive.org/web/20210515172331/https://www.nap.edu/read/11282/chapter/7 |url-status=live }}</ref> When the nuclear fireball does not reach the ground, this is the only fallout produced. Its amount can be estimated from the [[Neutron bomb#Basic concept|fission-fusion]] design and [[Nuclear weapon yield|yield]] of the weapon. ===Global fallout=== After the detonation of a weapon at or above the fallout-free altitude (an ''[[air burst]]''), [[Nuclear fission|fission]] products, un-fissioned nuclear material, and weapon residues vaporized by the heat of the fireball condense into a suspension of particles 10 [[nanometre|nm]] to 20 [[micrometre|μm]] in diameter. This size of [[particulates|particulate matter]], lifted to the [[stratosphere]], may take months or years to settle, and may do so anywhere in the world.<ref name="usnrdl-tr-933">{{cite journal |last1=Freiling |first1=E.C. |title=Radionuclide Fractionation in Air-Burst Debris |journal=Nature |date=20 September 1965 |volume=209 |issue=5020 |pages=236–8 |publisher=U.S. Naval Radiological Defense Laboratory |doi=10.1038/209236a0 |url=https://apps.dtic.mil/dtic/tr/fulltext/u2/626608.pdf |access-date=4 December 2018 |pmid=5915953 |s2cid=4149383 |archive-date=2 February 2020 |archive-url=https://web.archive.org/web/20200202165627/https://apps.dtic.mil/dtic/tr/fulltext/u2/626608.pdf |url-status=dead }}</ref> Its radioactive characteristics increase the statistical cancer risk, with up to 2.4 million people having died by 2020 from the measurable elevated atmospheric radioactivity after the widespread [[nuclear weapons testing]] of the 1950s, peaking in 1963 (the [[Bomb pulse]]).<ref name="s257">{{cite web | last=Adams | first=Lilly | title=Resuming Nuclear Testing a Slap in the Face to Survivors | website=The Equation | date=May 26, 2020 | url=https://blog.ucsusa.org/lilly-adams/resuming-nuclear-testing-a-slap-in-the-face-to-survivors/ | access-date=July 16, 2024}}</ref><ref>{{Cite web|url=https://www.cdc.gov/nceh/radiation/fallout/rf-gwt_home.htm|title=Radioactive Fallout from Global Weapons Testing: Home {{!}} CDC RSB|date=2019-02-11|website=www.cdc.gov|access-date=2019-04-19|archive-date=2019-04-19|archive-url=https://web.archive.org/web/20190419013250/https://www.cdc.gov/nceh/radiation/fallout/rf-gwt_home.htm|url-status=live}}</ref>{{Unreliable source?|date=February 2025}} Levels reached about 0.15 [[mSv]] per year worldwide, or about 7% of average [[background radiation]] dose from all sources, and has slowly decreased since,<ref name="t904">{{cite journal | last1=Bouville | first1=André | last2=Simon | first2=Steven L. | last3=Miller | first3=Charles W. | last4=Beck | first4=Harold L. | last5=Anspaugh | first5=Lynn R. | last6=Bennett | first6=Burton G. | title=Estimates of Doses from Global Fallout | journal=Health Physics | volume=82 | issue=5 | date=2002 | issn=0017-9078 | doi=10.1097/00004032-200205000-00015 | pages=690–705| pmid=12003019 | bibcode=2002HeaPh..82..690B }}</ref> with natural background radiation levels being around 1 [[mSv]]. Radioactive fallout has occurred around the world; for example, people have been exposed to [[iodine-131]] from atmospheric nuclear testing. Fallout accumulates on vegetation, including fruits and vegetables. Starting from 1951 people may have gotten exposure, depending on whether they were outside, the weather, and whether they consumed contaminated milk, vegetables or fruit. Exposure can be on an intermediate time scale or long term.<ref>{{Cite book|url=https://www.ncbi.nlm.nih.gov/books/NBK219147/|title=Radioactive Fallout|last1=Marston|first1=Robert Q.|last2=Solomon|first2=Fred|last3=War|first3=Institute of Medicine (US) Steering Committee for the Symposium on the Medical Implications of Nuclear|date=1986|publisher=National Academies Press (US)|access-date=2019-04-19|archive-date=2020-11-12|archive-url=https://web.archive.org/web/20201112043049/https://www.ncbi.nlm.nih.gov/books/NBK219147/|url-status=live}}</ref> The intermediate time scale results from fallout that has been put into the troposphere and ejected by precipitation during the first month. Long-term fallout can sometimes occur from deposition of tiny particles carried in the stratosphere.<ref>{{Cite web |last1=Lallanilla |first1=Marc |date=September 25, 2013 |title=Chernobyl: Facts About the Nuclear Disaster |url=https://www.livescience.com/39961-chernobyl.html |url-status=live |archive-url=https://web.archive.org/web/20190419013251/https://www.livescience.com/39961-chernobyl.html |archive-date=2019-04-19 |access-date=2019-04-19 |website=Live Science}}</ref> By the time that stratospheric fallout has begun to reach the earth, the radioactivity is very much decreased. Also, after a year it is estimated that a sizable quantity of fission products move from the northern to the southern stratosphere. The intermediate time scale is between 1 and 30 days, with long term fallout occurring after that. Examples of both intermediate and long term fallout occurred after the 1986 [[Chernobyl disaster|Chernobyl accident]], which contaminated over {{cvt|20000|km2|sqmi}} of land in [[Ukraine]] and [[Belarus]]. The main fuel of the reactor was [[uranium]], and surrounding this was graphite, both of which were vaporized by the hydrogen explosion that destroyed the reactor and breached its containment. An estimated 31 people died within a few weeks after this happened, including two plant workers killed at the scene. Although residents were evacuated within 36 hours, people started to complain of vomiting, migraines and other major signs of [[Acute radiation syndrome|radiation sickness]]. The officials of Ukraine had to close off an area with an {{convert|18|mile|km|adj=on|-1}} radius. Long term effects included at least 6,000 cases of [[thyroid cancer]], mainly among children. Fallout spread throughout Europe, with Northern Scandinavia receiving a heavy dose, contaminating reindeer herds in Lapland, and salad greens becoming almost unavailable in France. Some sheep farms in North Wales and the North Of England were required to monitor radioactivity levels in their flocks until the control was lifted in 2012.<ref>{{cite news |title=Chernobyl sheep controls lifted in Wales and Cumbria |url=https://www.bbc.co.uk/news/uk-wales-17472698 |access-date=13 April 2024 |agency=BBC |date=22 March 2012}}</ref> ===Local fallout=== [[Image:Bravo fallout2.png|right|300px|thumb|The {{convert|280|mi|km|order=flip|abbr=on}} fallout plume from 15 [[TNT equivalent|megaton]] surface burst [[Castle Bravo]], 1954.<br/>"Estimated total (accumulated) dose contours in [[Rad (unit)|rad]]s at 96 hours after the BRAVO test explosion"<ref>{{cite book|first1=Samuel|last1=Glasstone|first2=Philip J.|last2=Dolan|title=The Effects of Nuclear Weapons (3rd ed.)|year=1977|publisher=U.S. Department of Defense, U.S. Atomic Energy Commission|url=https://books.google.com/books?id=65tBAAAAIAAJ|pages=436–437|isbn=9780318203690 |quote=(page 436.) 9.107 A radiation dose of 700 rads over a period of 96 hours would probably prove fatal in the great majority of cases.}}</ref>]] During detonations of devices at ground level (''[[ground burst|surface burst]]''), below the fallout-free altitude, or in shallow water, heat [[vapor]]izes large amounts of earth or water, which is drawn up into the [[mushroom cloud|radioactive cloud]]. This material becomes radioactive when it combines with [[fission products]] or other radio-contaminants, or when it is [[neutron activation|neutron-activated]]. The table below summarizes the abilities of common isotopes to form fallout. Some radiation taints large amounts of land and [[drinking water]] causing formal [[mutation]]s throughout animal and human life. {| class="wikitable collapsible" |+ Table (according to T. Imanaka ''et al.'') of the relative abilities of isotopes to form solids ! Isotope !! <sup>91</sup>Sr!! <sup>92</sup>Sr!! <sup>95</sup>Zr!! <sup>99</sup>Mo!! <sup>106</sup>Ru!! <sup>131</sup>Sb !! <sup>132</sup>Te !!<sup>134</sup>Te!! <sup>137</sup>Cs!! <sup>140</sup>Ba!! <sup>141</sup>La!! <sup>144</sup>Ce |- | Refractive index || 0.2|| 1.0|| 1.0|| 1.0|| 0.0|| 0.1|| 0.0|| 0.0|| 0.0|| 0.3|| 0.7|| 1.0 |} [[Image:US fallout exposure.png|right|thumb|Per capita [[thyroid]] doses in the continental United States resulting from all exposure routes from all atmospheric [[nuclear testing|nuclear tests]] conducted at the [[Nevada Test Site]] from 1951 to 1962 and from emissions from plutonium production at the [[Hanford Site]] in Washington state]] A surface burst generates large amounts of particulate matter, composed of particles from less than 100 [[nanometre|nm]] to several millimeters in diameter—in addition to very fine particles that contribute to worldwide fallout.<ref name="effects2005"/> The larger particles spill out of the stem and cascade down the outside of the fireball in a downdraft even as the cloud rises, so fallout begins to arrive near [[ground zero]] within an hour. More than half the total bomb debris lands on the ground within about 24 hours as local fallout.<ref name="KDFOC3">{{cite book |last1=Harvey |first1=T. |title=KDFOC3: A Nuclear Fallout Assessment Capability |date=1992 |publisher=Lawrence Livermore National Laboratories |url=https://narac.llnl.gov/content/mods/publications/op-model-description-evaluation/UCRL-TM-222788.pdf |access-date=4 December 2018 |archive-date=27 September 2020 |archive-url=https://web.archive.org/web/20200927002905/https://narac.llnl.gov/content/mods/publications/op-model-description-evaluation/UCRL-TM-222788.pdf |url-status=live }}</ref> Chemical properties of the elements in the fallout control the rate at which they are deposited on the ground. Less volatile elements deposit first. Severe local fallout contamination can extend far beyond the blast and thermal effects, particularly in the case of high yield surface detonations. The ground track of fallout from an explosion depends on the weather from the time of detonation onward. In stronger winds, fallout travels faster but takes the same time to descend, so although it covers a larger path, it is more spread out or diluted. Thus, the width of the fallout pattern for any given dose rate is reduced where the downwind distance is increased by higher winds. The total amount of activity deposited up to any given time is the same irrespective of the wind pattern, so overall casualty figures from fallout are generally independent of winds. But [[thunderstorm]]s can bring down activity as [[rain]] allows fallout to drop more rapidly, particularly if the [[mushroom cloud]] is low enough to be below ("washout"), or mixed with ("rainout"), the thunderstorm. Whenever individuals remain in a [[radioactive contamination|radiologically contaminated]] area, such contamination leads to an immediate external radiation exposure as well as a possible later internal hazard from inhalation and ingestion of radiocontaminants, such as the rather short-lived [[iodine-131]], which is accumulated in the [[thyroid]].
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