Editing Radioactive waste (section)

== Sources ==
{{Actinides vs fission products}}
Radioactive waste comes from a number of sources. In countries with nuclear power plants, nuclear armament, or nuclear fuel treatment plants, the majority of waste originates from the nuclear fuel cycle and nuclear weapons reprocessing. Other sources include medical and industrial wastes, as well as naturally occurring radioactive materials (NORM) that can be concentrated as a result of the processing or consumption of coal, oil, and gas, and some minerals, as discussed below.

=== Nuclear fuel cycle ===
{{Main|Nuclear fuel cycle|Spent nuclear fuel}}
{{see also|Nuclear power}}

==== Front end ====
Waste from the front end of the [[nuclear fuel cycle]] is usually alpha-emitting waste from the extraction of uranium. It often contains radium and its decay products.

[[Uranium dioxide]] (UO<sub>2</sub>) concentrate from mining is a thousand or so times as radioactive as the [[granite]] used in buildings. It is refined from [[yellowcake]] (U<sub>3</sub>O<sub>8</sub>), then converted to [[uranium hexafluoride]] gas (UF<sub>6</sub>). As a gas, it undergoes [[enriched uranium|enrichment]] to increase the [[U-235]] content from 0.7% to about 4.4% (LEU). It is then turned into a hard [[ceramic]] oxide (UO<sub>2</sub>) for assembly as reactor fuel elements.<ref>{{cite book |last=Cochran |first=Robert |url=http://www.new.ans.org/store/i_350015 |title=The Nuclear Fuel Cycle: Analysis and Management |publisher=American Nuclear Society |year=1999 |isbn=0-89448-451-6 |location=La Grange Park, Illinois |pages=52–57 |language=en-us |access-date=2011-09-04 |archive-url=https://web.archive.org/web/20111016144333/http://www.new.ans.org/store/i_350015 |archive-date=2011-10-16 |url-status=dead}}</ref>

The main by-product of enrichment is [[depleted uranium]] (DU), principally the [[Uranium-238|U-238]] isotope, with a U-235 content of ~0.3%. It is stored, either as UF<sub>6</sub> or as U<sub>3</sub>O<sub>8</sub>. Some is used in applications where its extremely high density makes it valuable such as [[anti-tank]] [[KE-penetrator|shells]], and on at least [[Pen Duick|one occasion]] even a sailboat [[keel]].<ref>{{cite web |url=http://www.janes.com/defence/news/jdw/jdw010108_1_n.shtml |title=Global Defence News and Defence Headlines – IHS Jane's 360 |url-status=live |archive-url=https://web.archive.org/web/20080725032900/http://www.janes.com/defence/news/jdw/jdw010108_1_n.shtml |archive-date=2008-07-25}}</ref> It is also used with plutonium for making [[mixed oxide fuel]] (MOX) and to dilute, or [[enriched uranium#Downblending|downblend]], highly enriched uranium from weapons stockpiles which is now being redirected to become reactor fuel.

==== Back end ====
{{See also|Nuclear reprocessing}}
The back-end of the nuclear fuel cycle, mostly spent [[fuel rod]]s, contains [[fission product]]s that emit beta and gamma radiation, and [[actinide]]s that emit [[alpha particle]]s, such as [[uranium-234]] (half-life 245&nbsp;thousand years), [[neptunium-237]] (2.144&nbsp;million years), [[plutonium-238]] (87.7&nbsp;years) and [[americium-241]] (432 years), and even sometimes some neutron emitters such as [[californium]] (half-life of 898 years for californium-251). These isotopes are formed in [[nuclear reactor]]s.

It is important to distinguish the processing of uranium to make fuel from the [[nuclear reprocessing|reprocessing]] of used fuel. Used fuel contains the highly radioactive products of fission (see high-level waste below). Many of these are neutron absorbers, called [[neutron poison]]s in this context. These eventually build up to a level where they absorb so many neutrons that the chain reaction stops, even with the control rods completely removed from a reactor. At that point, the fuel has to be replaced in the reactor with fresh fuel, even though there is still a substantial quantity of [[uranium-235]] and [[plutonium]] present. In the United States, this used fuel is usually "stored", while in other countries such as Russia, the United Kingdom, France, Japan, and India, the fuel is reprocessed to remove the fission products, and the fuel can then be re-used.<ref>{{cite web |title=Recycling spent nuclear fuel: the ultimate solution for the US? |url=http://analysis.nuclearenergyinsider.com/operations-maintenance/recycling-spent-nuclear-fuel-ultimate-solution-us |url-status=bot: unknown |archive-url=https://web.archive.org/web/20121128101318/http://analysis.nuclearenergyinsider.com/operations-maintenance/recycling-spent-nuclear-fuel-ultimate-solution-us |archive-date=28 November 2012 |access-date=2015-07-29 |website=Nuclear Energy Insider}}</ref> The fission products removed from the fuel are a concentrated form of high-level waste as are the chemicals used in the process. While most countries reprocess the fuel carrying out single plutonium cycles, India is planning multiple plutonium recycling schemes <ref name="reprocess">{{cite web |title=Continuous Plutonium Recycling In India: Improvements in Reprocessing Technology |url=http://www.dailykos.com/story/2009/6/13/742039/-Continuous-Plutonium-Recycling-In-India:Improvements-in-Reprocessing-Technology. |url-status=dead |archive-url=https://web.archive.org/web/20110606130212/http://www.dailykos.com/story/2009/6/13/742039/-Continuous-Plutonium-Recycling-In-India:Improvements-in-Reprocessing-Technology. |archive-date=2011-06-06 |website=dailykos.com}}</ref> and Russia pursues closed cycle.<ref>{{Cite web |url=https://world-nuclear.org/information-library/country-profiles/countries-o-s/russia-nuclear-fuel-cycle.aspx |title=Russia's Nuclear Fuel Cycle &#124; Russian Nuclear Fuel Cycle - World Nuclear Association}}</ref>

==== Fuel composition and long term radioactivity ====
[[File:Activityofuranium233.jpg|thumb|upright=1.4|Activity of [[Uranium-233|U-233]] for three fuel types. In the case of MOX, the U-233 increases for the first 650 thousand years as it is produced by the decay of [[Np-237]] which was created in the reactor by absorption of neutrons by U-235.]]
{{See also|Spent nuclear fuel|High-level waste}}
{{Main|Long-lived fission product}}
[[File:Activitytotal1.svg|thumb|upright=1.4|Total activity for three fuel types. In region 1, there is radiation from short-lived nuclides, in region 2, from [[Sr-90]] and [[Cs-137]], and on the far right, the decay of Np-237 and U-233.]]
The use of different fuels in nuclear reactors results in different [[spent nuclear fuel]] (SNF) composition, with varying activity curves. The most abundant material being U-238 with other uranium isotopes, other actinides, fission products and activation products.<ref name=":1">{{Cite web |title=Radioactivity : Spent fuel composition |url=https://www.radioactivity.eu.com/site/pages/Spent_Fuel_Composition.htm |url-status=dead |archive-url=https://web.archive.org/web/20200923005202/https://www.radioactivity.eu.com/site/pages/Spent_Fuel_Composition.htm |archive-date=2020-09-23 |access-date=2021-08-10 |website=www.radioactivity.eu.com}}</ref>

Long-lived radioactive waste from the back end of the fuel cycle is especially relevant when designing a complete waste management plan for SNF. When looking at long-term radioactive decay, the actinides in the SNF have a significant influence due to their characteristically long half-lives. Depending on what a [[nuclear reactor]] is fueled with, the actinide composition in the SNF will be different.

An example of this effect is the use of [[nuclear fuel]]s with [[thorium]]. Th-232 is a fertile material that can undergo a neutron capture reaction and two beta minus decays, resulting in the production of fissile [[uranium-233|U-233]]. The SNF of a cycle with thorium will contain U-233. Its radioactive decay will strongly influence the long-term [[radioactive decay|activity]] curve of the SNF for around a million years. A comparison of the activity associated to U-233 for three different SNF types can be seen in the figure on the top right. The burnt fuels are thorium with reactor-grade plutonium (RGPu), thorium with weapons-grade plutonium (WGPu), and [[Mixed oxide fuel]] (MOX, no thorium). For RGPu and WGPu, the initial amount of U-233 and its decay for around a million years can be seen. This has an effect on the total activity curve of the three fuel types. The initial absence of U-233 and its daughter products in the MOX fuel results in a lower activity in region 3 of the figure at the bottom right, whereas for RGPu and WGPu the curve is maintained higher due to the presence of U-233 that has not fully decayed. Nuclear reprocessing can remove the actinides from the spent fuel so they can be used or destroyed (see {{section link|Long-lived fission product|Actinides}}).

==== Proliferation concerns ====
{{See also|Nuclear proliferation|Reactor-grade plutonium}}

Since uranium and plutonium are [[nuclear weapons]] materials, there are proliferation concerns. Ordinarily (in spent nuclear fuel), plutonium is [[reactor-grade plutonium]]. In addition to [[plutonium-239]], which is highly suitable for building nuclear weapons, it contains large amounts of undesirable contaminants: [[plutonium-240]], [[plutonium-241]], and [[plutonium-238]]. These isotopes are extremely difficult to separate, and more cost-effective ways of obtaining fissile material exist (e.g., uranium enrichment or dedicated plutonium production reactors).<ref>{{cite web |url=http://www.world-nuclear.org/info/inf15.html |title=Plutonium |author=World Nuclear Association |date=March 2009 |access-date=2010-03-18 |url-status=dead |archive-url=https://web.archive.org/web/20100330221426/http://www.world-nuclear.org/info/inf15.html |archive-date=2010-03-30}}</ref>

High-level waste is full of highly radioactive [[fission products]], most of which are relatively short-lived. This is a concern since if the waste is stored, perhaps in deep geological storage, over many years the fission products decay, decreasing the radioactivity of the waste and making the plutonium easier to access. The undesirable contaminant Pu-240 decays faster than the Pu-239, and thus the quality of the bomb material increases with time (although its quantity decreases during that time as well). Thus, some have argued, as time passes, these deep storage areas have the potential to become "plutonium mines", from which material for nuclear weapons can be acquired with relatively little difficulty. Critics of the latter idea have pointed out the difficulty of recovering useful material from sealed deep storage areas makes other methods preferable. Specifically, high radioactivity and heat (80&nbsp;°C in surrounding rock) greatly increase the difficulty of mining a storage area, and the enrichment methods required have high capital costs.<ref>{{cite web |url=http://nci.org/s/sp121495.htm |title=A Perspective on the Proliferation Risks of Plutonium Mines |author=Lyman, Edwin S. |publisher=[[Nuclear Control Institute]] |date=December 1994 |access-date=2015-11-25 |url-status=dead |archive-url=https://web.archive.org/web/20151125225922/http://nci.org/s/sp121495.htm |archive-date=2015-11-25}}</ref>

Pu-239 decays to U-235 which is suitable for weapons and which has a very long half-life (roughly 10<sup>9</sup> years). Thus plutonium may decay and leave uranium-235. However, modern reactors are only moderately enriched with U-235 relative to U-238, so the U-238 continues to serve as a [[Denaturation (fissile materials)|denaturation]] agent for any U-235 produced by plutonium decay.

One solution to this problem is to recycle the plutonium and use it as a fuel e.g. in [[fast reactor]]s. In [[integral fast reactor|pyrometallurgical fast reactors]], the separated plutonium and uranium are contaminated by actinides and cannot be used for nuclear weapons.

=== Nuclear weapons decommissioning ===
Waste from nuclear weapons decommissioning is unlikely to contain much beta or gamma activity other than [[tritium]] and [[americium]]. It is more likely to contain alpha-emitting actinides such as Pu-239 which is a fissile material used in nuclear bombs, plus some material with much higher specific activities, such as Pu-238 or Po.

In the past the neutron trigger for an [[atomic bomb]] tended to be [[beryllium]] and a high activity alpha emitter such as [[polonium]]; an alternative to polonium is [[Pu-238]]. For reasons of national security, details of the design of modern nuclear bombs are normally not released to the open literature.

Some designs might contain a [[radioisotope thermoelectric generator]] using Pu-238 to provide a long-lasting source of electrical power for the electronics in the device.

It is likely that the fissile material of an old nuclear bomb, which is due for refitting, will contain decay products of the plutonium isotopes used in it. These are likely to include [[U-236]] from Pu-240 impurities plus some U-235 from decay of the Pu-239; due to the relatively long half-life of these Pu isotopes, these wastes from radioactive decay of bomb core material would be very small, and in any case, far less dangerous (even in terms of simple radioactivity) than the Pu-239 itself.

The beta decay of [[Pu-241]] forms [[Am-241]]; the in-growth of americium is likely to be a greater problem than the decay of Pu-239 and Pu-240 as the americium is a gamma emitter (increasing external-exposure to workers) and is an alpha emitter which can cause the generation of [[heat]]. The plutonium could be separated from the americium by several different processes; these would include [[Nuclear reprocessing#Pyroprocessing|pyrochemical]] processes and aqueous/organic [[solvent extraction]]. A truncated [[PUREX]] type extraction process would be one possible method of making the separation. Naturally occurring uranium is not fissile because it contains 99.3% of U-238 and only 0.7% of U-235.

=== Legacy waste ===
Due to historic activities typically related to the radium industry, uranium mining, and military programs, numerous sites contain or are contaminated with radioactivity. In the United States alone, the [[United States Department of Energy|Department of Energy]] (DOE) states there are "millions of gallons of radioactive waste" as well as "thousands of tons of spent nuclear fuel and material" and also "huge quantities of contaminated soil and water."<ref name="usemdoefyp">[http://www.em.doe.gov/ U.S. Department of Energy Environmental Management] {{webarchive|url=https://web.archive.org/web/20070319214054/http://www.em.doe.gov/ |date=2007-03-19 }} – "[http://www.em.doe.gov/PDFs/170016EM_FYP_Final_3-6-06.pdf Department of Energy Five Year Plan FY 2007-FY 2011 Volume II] {{webarchive|url=https://web.archive.org/web/20070705081614/http://www.em.doe.gov/PDFs/170016EM_FYP_Final_3-6-06.pdf |date=2007-07-05 }}." Retrieved 8 April 2007.</ref> Despite copious quantities of waste, in 2007, the DOE stated a goal of cleaning all presently contaminated sites successfully by 2025.<ref name="usemdoefyp" /> The [[Fernald, Ohio|Fernald]], [[Ohio]] site for example had "31 million pounds of uranium product", "2.5 billion pounds of waste", "2.75 million cubic yards of contaminated soil and debris", and a "223 acre portion of the underlying Great Miami Aquifer had uranium levels above drinking standards."<ref name="usemdoefyp" /> The United States has at least 108 sites designated as areas that are contaminated and unusable, sometimes many thousands of acres.<ref name="usemdoefyp" /><ref>American Scientist, January/February 2007.</ref> The DOE wishes to clean or mitigate many or all by 2025, using the recently developed method of [[geomelting]],{{citation needed|date=November 2013}} however the task can be difficult and it acknowledges that some may never be completely remediated. In just one of these 108 larger designations, [[Oak Ridge National Laboratory]] (ORNL), there were for example at least "167 known contaminant release sites" in one of the three subdivisions of the {{convert|37000|acre|km2|0|adj=on}} site.<ref name="usemdoefyp" /> Some of the U.S. sites were smaller in nature, however, cleanup issues were simpler to address, and the DOE has successfully completed cleanup, or at least closure, of several sites.<ref name="usemdoefyp" />

=== Medicine ===
Radioactive [[medical waste]] tends to contain [[beta particle]] and [[gamma ray]] emitters. It can be divided into two main classes. In diagnostic [[nuclear medicine]] a number of short-lived gamma emitters such as [[technetium-99m]] are used. Many of these can be disposed of by leaving it to decay for a short time before disposal as normal waste. Other isotopes used in medicine, with half-lives in parentheses, include:
* [[yttrium|Y-90]], used for treating [[lymphoma]] (2.7 days)
* [[radioiodine|I-131]], used for [[thyroid]] function tests and for treating [[thyroid cancer]] (8.0 days)
* [[strontium|Sr-89]], used for treating [[bone cancer]], [[intravenous injection]] (52 days)
* [[iridium|Ir-192]], used for [[brachytherapy]] (74 days)
* [[cobalt|Co-60]], used for brachytherapy and external radiotherapy (5.3 years)
* [[Cs-137]], used for brachytherapy and external radiotherapy (30 years)
* [[Tc-99]], product of the decay of Technetium-99m (221,000 years)

=== Industry ===
Industrial source waste can contain alpha, [[beta decay|beta]], [[neutron emission|neutron]] or gamma emitters. Gamma emitters are used in [[radiography]] while neutron emitting sources are used in a range of applications, such as [[oil well]] logging.<ref>{{cite web |title=Nuclear Logging |url=http://www.logwell.com/tech/nuclear/index.html |url-status=live |archive-url=https://web.archive.org/web/20090627070724/http://www.logwell.com/tech/nuclear/index.html |archive-date=2009-06-27 |access-date=2009-07-07 |website=logwell.com}}</ref>

=== Naturally occurring radioactive material ===
[[File:Uranium and thorium release from coal combustion.gif|thumb|upright=2.2|Annual release of [[uranium]] and [[thorium]] [[radioisotopes]] from coal combustion, predicted by [[ORNL]] in 1993 to cumulatively amount to 2.9 Mt over the 1937–2040 period, from the combustion of an estimated 637 Gt of coal worldwide.<ref name="ornl">{{cite journal |author=Gabbard |first=Alex |year=1993 |title=Coal Combustion |url=http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html |url-status=dead |journal=ORNL Review |language=en-us |location=Oak Ridge, Tennessee |publisher=Oak Ridge National Laboratory |volume=26 |issue=3–4 |archive-url=https://web.archive.org/web/20070205103749/http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html |archive-date=February 5, 2007}}</ref>]]

Substances containing natural radioactivity are known as [[NORM]] (naturally occurring radioactive material). After human processing that exposes or concentrates this natural radioactivity (such as mining bringing coal to the surface or burning it to produce concentrated ash), it becomes technologically enhanced naturally occurring radioactive material (TENORM).<ref>{{cite web |url=http://www.epa.gov/radiation/tenorm/sources.html |title=TENORM Sources &#124; Radiation Protection &#124; US EPA |publisher=Epa.gov |date=2006-06-28 |access-date=2013-08-01 |url-status=live |archive-url=https://web.archive.org/web/20130520064746/http://www.epa.gov/radiation/tenorm/sources.html |archive-date=2013-05-20}}</ref> Much of this waste is [[alpha particle]]-emitting matter from the decay chains of [[uranium]] and thorium. The main source of radiation in the human body is [[potassium]]-40 ([[potassium-40|<sup>40</sup>K]]), typically 17 milligrams in the body at a time and 0.4 milligrams/day intake.<ref>Idaho State University. [http://www.physics.isu.edu/radinf/natural.htm Radioactivity in Nature] {{webarchive|url=https://web.archive.org/web/20150205001244/http://www.physics.isu.edu/radinf/natural.htm |date=2015-02-05 }}</ref> Most rocks, especially [[granite]], have a low level of radioactivity due to the potassium-40, thorium and uranium contained.

Usually ranging from 1 [[millisievert]] (mSv) to 13&nbsp;mSv annually depending on location, average radiation exposure from natural radioisotopes is 2.0&nbsp;mSv per person a year worldwide.<ref name="UNSCEAR">United Nations Scientific Committee on the Effects of Atomic Radiation. [http://www.unscear.org/docs/reports/2008/09-86753_Report_2008_GA_Report_corr2.pdf Sources and Effects of Ionizing Radiation, UNSCEAR 2008] {{webarchive|url=https://web.archive.org/web/20120503203201/http://www.unscear.org/docs/reports/2008/09-86753_Report_2008_GA_Report_corr2.pdf |date=2012-05-03 }}</ref> This makes up the majority of typical total dosage (with mean annual exposure from other sources amounting to 0.6&nbsp;mSv from medical tests averaged over the whole populace, 0.4&nbsp;mSv from [[cosmic ray]]s, 0.005&nbsp;mSv from the legacy of past atmospheric nuclear testing, 0.005&nbsp;mSv occupational exposure, 0.002&nbsp;mSv from the [[Chernobyl disaster]], and 0.0002&nbsp;mSv from the nuclear fuel cycle).<ref name="UNSCEAR" />

TENORM is not regulated as restrictively as nuclear reactor waste, though there are no significant differences in the radiological risks of these materials.<ref>{{cite web |url=http://www.tenorm.com/regs2.htm |title=Regulation of TENORM |publisher=Tenorm.com |access-date=2013-08-01 |url-status=dead |archive-url=https://web.archive.org/web/20130723203944/http://www.tenorm.com/regs2.htm |archive-date=2013-07-23}}</ref>

==== Coal ====
[[Coal]] contains a small amount of radioactive uranium, barium, thorium, and potassium, but, in the case of pure coal, this is significantly less than the average concentration of those elements in the [[Earth's crust]]. The surrounding strata, if shale or mudstone, often contain slightly more than average and this may also be reflected in the ash content of 'dirty' coals.<ref name="ornl" /><ref>[https://web.archive.org/web/20081202150006/http://www.uic.com.au/nip78.htm Cosmic origins of Uranium]. uic.com.au (November 2006)</ref> The more active ash minerals become concentrated in the [[fly ash]] precisely because they do not burn well.<ref name="ornl" /> The radioactivity of fly ash is about the same as black [[shale]] and is less than [[phosphate]] rocks, but is more of a concern because a small amount of the fly ash ends up in the atmosphere where it can be inhaled.<ref>U.S. Geological Survey, [http://geology.cr.usgs.gov/energy/factshts/163-97/FS-163-97.html Radioactive Elements in Coal and Fly Ash: Abundance, Forms, and Environmental Significance] {{webarchive|url=https://web.archive.org/web/20051124173511/http://geology.cr.usgs.gov/energy/factshts/163-97/FS-163-97.html |date=2005-11-24 }}, ''Fact Sheet'' FS-163-1997, October 1997. Retrieved September 2007.</ref> According to U.S. [[National Council on Radiation Protection and Measurements]] (NCRP) reports, population exposure from 1000-MWe power plants amounts to 490 [[person-rem/year]] for coal power plants, 100 times as great as nuclear power plants (4.8 person-rem/year). The exposure from the complete nuclear fuel cycle from mining to waste disposal is 136 person-rem/year; the corresponding value for coal use from mining to waste disposal is "probably unknown".<ref name="ornl" />

==== Oil and gas ====
Residues from the [[oil and gas industry]] often contain radium and its decay products. The sulfate scale from an oil well can be radium rich, while the water, oil, and gas from a well often contain [[radon]]. The radon decays to form solid radioisotopes which form coatings on the inside of pipework. In an oil processing plant, the area of the plant where [[propane]] is processed is often one of the more contaminated areas of the plant as radon has a similar boiling point to propane.<ref>[http://www.enprotec-inc.com/Presentations/NORM.pdf Survey & Identification of NORM Contaminated Equipment] {{webarchive|url=https://web.archive.org/web/20060220195742/http://www.enprotec-inc.com/Presentations/NORM.pdf |date=2006-02-20 }}. enprotec-inc.com.</ref>

Radioactive elements are an industrial problem in some oil wells where workers operating in direct contact with the crude oil and [[brine]] can be exposed to doses having negative health effects. Due to the relatively high concentration of these elements in the brine, its disposal is also a technological challenge. Since the 1980s, in the United States, the brine is however exempt from the dangerous waste regulations and can be disposed of regardless of radioactive or toxic substances content.<ref>{{Cite web |title=The Syrian Job: Uncovering the Oil Industry's Radioactive Secret |url=https://desmog.co.uk/2020/04/29/syrian-job-oil-industry-radioactive-secret |last=Nobel |first=Justin |date=29 April 2020 |publisher=DeSmog UK |language=en |access-date=10 August 2020}}</ref>

==== Rare-earth mining ====
Due to natural occurrence of radioactive elements such as thorium and [[radium]] in [[Rare-earth element|rare-earth ore]], mining operations also result in production of waste and mineral deposits that are slightly radioactive.<ref>{{Cite web |url=https://www.theatlantic.com/magazine/archive/2009/05/clean-energys-dirty-little-secret/307377/ |title=Clean Energy's Dirty Little Secret |last=Margonelli |first=Lisa |date=2009-05-01 |website=The Atlantic |language=en-US |access-date=2020-04-23}}</ref> 
{{See also|Rare-earth element#Environmental considerations}}