Editing Nuclear power (section)

==== High-level waste ====
{{main|High-level waste|Spent nuclear fuel}}
[[File:Spent nuclear fuel decay sievert.jpg|thumb|upright=1.5|Activity of spent UOx fuel in comparison to the activity of natural [[uranium ore]] over time<ref name="m.phys.org">{{Cite web | url=https://m.phys.org/news/2017-11-fast-reactor-shorten-lifetime-long-lived.html |title = A fast reactor system to shorten the lifetime of long-lived fission products}}</ref><ref name="jaif"/>]]
[[File:Nuclear dry storage.jpg|thumb|[[Dry cask storage]] vessels storing spent nuclear fuel assemblies]]

The most important waste stream from nuclear power reactors is [[spent nuclear fuel]], which is considered [[high-level waste]]. For Light Water Reactors (LWRs), spent fuel is typically composed of 95% uranium, 4% [[fission product]]s, and about 1% [[transuranic]] [[actinides]] (mostly [[plutonium]], [[neptunium]] and [[americium]]).<ref>{{cite web |title=Radioactivity: Minor Actinides |url=http://www.radioactivity.eu.com/site/pages/Minor_Actinides.htm |website=www.radioactivity.eu.com |access-date=2018-12-23 |archive-date=2018-12-11 |archive-url=https://web.archive.org/web/20181211042617/http://www.radioactivity.eu.com/site/pages/Minor_Actinides.htm |url-status=dead }}</ref> The fission products are responsible for the bulk of the short-term radioactivity, whereas the plutonium and other transuranics are responsible for the bulk of the long-term radioactivity.<ref>{{cite book |last1=Ojovan |first1=Michael I. |title=An introduction to nuclear waste immobilisation, second edition |date=2014 |publisher=Elsevier |location=Kidlington, Oxford, U.K. |isbn=978-0-08-099392-8 |edition=2nd}}</ref>

High-level waste (HLW) must be stored isolated from the [[biosphere]] with sufficient shielding so as to limit radiation exposure. After being removed from the reactors, used fuel bundles are stored for six to ten years in [[spent fuel pool]]s, which provide cooling and shielding against radiation. After that, the fuel is cool enough that it can be safely transferred to [[dry cask storage]].<ref>{{Cite web|url=http://nuclearsafety.gc.ca/eng/waste/high-level-waste/index.cfm|title=High-level radioactive waste|publisher=Canadian Nuclear Safety Commission|date=February 3, 2014|website=nuclearsafety.gc.ca|access-date=April 19, 2022|archive-date=April 14, 2022|archive-url=https://web.archive.org/web/20220414190417/http://nuclearsafety.gc.ca/eng/waste/high-level-waste/index.cfm|url-status=dead}}</ref> The radioactivity decreases exponentially with time, such that it will have decreased by 99.5% after 100 years.<ref>{{cite tech report |last1=Hedin |first1=A. |title=Spent nuclear fuel - how dangerous is it? A report from the project 'Description of risk' |date=1997 |url=https://www.osti.gov/etdeweb/biblio/587853 |publisher=Energy Technology Data Exchange}}</ref> The more intensely radioactive short-lived [[fission products]] (SLFPs) decay into stable elements in approximately 300 years, and after about 100,000 years, the spent fuel becomes less radioactive than natural uranium ore.<ref name="jaif"/><ref>{{cite book |last1=Bruno |first1=Jordi |last2=Duro |first2=Laura |last3=Diaz-Maurin |first3=François |date=2020 |title=Advances in Nuclear Fuel Chemistry |chapter=Chapter 13 – Spent nuclear fuel and disposal |series=Woodhead Publishing Series in Energy |pages=527–553 |chapter-url=https://www.sciencedirect.com/science/article/pii/B9780081025710000148 |publisher=Woodhead Publishing |doi=10.1016/B978-0-08-102571-0.00014-8 |isbn=978-0-08-102571-0 |s2cid=216544356 |access-date=2021-09-20 |archive-date=2021-09-20 |archive-url=https://web.archive.org/web/20210920212807/https://www.sciencedirect.com/science/article/pii/B9780081025710000148 |url-status=live }}</ref>

Commonly suggested methods to isolate LLFP waste from the biosphere include separation and [[Nuclear transmutation|transmutation]],<ref name="jaif"/> [[synroc]] treatments, or deep geological storage.<ref>{{cite book |last1=Ojovan |first1=M. I. |title=An Introduction to Nuclear Waste Immobilisation |last2=Lee |first2=W. E. |publisher=Elsevier Science Publishers |year=2005 |isbn=978-0-08-044462-8 |location=Amsterdam, Netherlands |page=315}}</ref><ref>{{cite book |title=Technical Bases for Yucca Mountain Standards |author=National Research Council |year=1995 |publisher=National Academy Press |location=Washington, DC |isbn=978-0-309-05289-4|url=https://books.google.com/books?id=1DLyAtgVPy0C&pg=PA91|page=91}}</ref><ref>{{cite web |url=http://www.aps.org/units/fps/newsletters/2006/january/article1.html |title=The Status of Nuclear Waste Disposal |date=January 2006 |publisher=The American Physical Society |access-date=2008-06-06 |archive-date=2008-05-16 |archive-url=https://web.archive.org/web/20080516010935/http://www.aps.org/units/fps/newsletters/2006/january/article1.html |url-status=live }}</ref><ref>{{cite web |url=http://www.epa.gov/radiation/docs/yucca/70fr49013.pdf |title=Public Health and Environmental Radiation Protection Standards for Yucca Mountain, Nevada; Proposed Rule |date=2005-08-22 |publisher=United States Environmental Protection Agency |access-date=2008-06-06 |archive-date=2008-06-26 |archive-url=https://web.archive.org/web/20080626191551/http://www.epa.gov/radiation/docs/yucca/70fr49013.pdf |url-status=live }}</ref>

[[Thermal-neutron reactor]]s, which presently constitute the majority of the world fleet, cannot burn up the [[reactor grade plutonium]] that is generated during the reactor operation. This limits the life of nuclear fuel to a few years. In some countries, such as the United States, spent fuel is classified in its entirety as a nuclear waste.<ref>{{cite web |url=https://fas.org/sgp/crs/misc/RL32163.pdf |title=CRS Report for Congress. Radioactive Waste Streams: Waste Classification for Disposal |quote=The Nuclear Waste Policy Act of 1982 (NWPA) defined irradiated fuel as spent nuclear fuel, and the byproducts as high-level waste. |access-date=2018-12-22 |archive-date=2017-08-29 |archive-url=https://web.archive.org/web/20170829231541/https://fas.org/sgp/crs/misc/RL32163.pdf |url-status=live }}</ref> In other countries, such as France, it is largely reprocessed to produce a partially recycled fuel, known as mixed oxide fuel or [[MOX]]. For spent fuel that does not undergo reprocessing, the most concerning isotopes are the medium-lived [[transuranic element]]s, which are led by reactor-grade plutonium (half-life 24,000 years).<ref>{{harvnb|Vandenbosch|2007|p=21.|Ref=none}}</ref> Some proposed reactor designs, such as the [[integral fast reactor]] and [[molten salt reactor]]s, can use as fuel the plutonium and other actinides in spent fuel from light water reactors, thanks to their [[fast fission]] spectrum. This offers a potentially more attractive alternative to deep geological disposal.<ref>{{cite news |author=Clark |first=Duncan |date=2012-07-09 |title=Nuclear waste-burning reactor moves a step closer to reality |url=https://www.theguardian.com/environment/2012/jul/09/nuclear-waste-burning-reactor |url-status=live |archive-url=https://web.archive.org/web/20221008223126/https://www.theguardian.com/environment/2012/jul/09/nuclear-waste-burning-reactor |archive-date=2022-10-08 |access-date=2013-06-14 |newspaper=Guardian |location=London, England}}</ref><ref>{{cite web |author=Monbiot |first=George |date=5 December 2011 |title=A Waste of Waste |url=http://www.monbiot.com/2011/12/05/a-waste-of-waste/ |url-status=live |archive-url=https://web.archive.org/web/20130601052759/http://www.monbiot.com/2011/12/05/a-waste-of-waste/ |archive-date=2013-06-01 |access-date=2013-06-14 |publisher=Monbiot.com}}</ref><ref>{{cite web|url=https://www.youtube.com/watch?v=AZR0UKxNPh8  |archive-url=https://ghostarchive.org/varchive/youtube/20211211/AZR0UKxNPh8| archive-date=2021-12-11 |url-status=live|title=Energy From Thorium: A Nuclear Waste Burning Liquid Salt Thorium Reactor |publisher=YouTube |date=2009-07-23 |access-date=2013-06-14}}{{cbignore}}</ref>

The [[thorium fuel cycle]] results in similar fission products, though creates a much smaller proportion of transuranic elements from [[neutron capture]] events within a reactor. Spent thorium fuel, although more difficult to handle than spent uranium fuel, may present somewhat lower proliferation risks.<ref>{{cite web |title=Role of Thorium to Supplement Fuel Cycles of Future Nuclear Energy Systems |url=https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1540_web.pdf |publisher=IAEA |access-date=7 April 2021 |date=2012 |quote=Once irradiated in a reactor, the fuel of a thorium–uranium cycle contains an admixture of 232U (half-life 68.9 years) whose radioactive decay chain includes emitters (particularly 208Tl) of high energy gamma radiation (2.6{{nbsp}}MeV). This makes spent thorium fuel treatment more difficult, requires remote handling/control during reprocessing and during further fuel fabrication, but on the other hand, may be considered as an additional non-proliferation barrier. |archive-date=6 May 2021 |archive-url=https://web.archive.org/web/20210506123715/https://www-pub.iaea.org/MTCD/publications/PDF/Pub1540_web.pdf |url-status=live }}</ref>