Template:Did you know and Radioactive waste: Difference between pages
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'''Radioactive waste''' are [[waste types]] containing [[radioactive decay|radioactive]] [[chemical element]]s that do not have a practical purpose. It is sometimes the product of a nuclear process, such as [[nuclear fission]]. However, other industries not directly connected to the nuclear industry can produce large quantities of radioactive waste. For instance, over the past 20 years it is estimated that just the oil-producing endeavors of the US have accumulated 8 million tons of radioactive wastes.<ref>Krivtsov, A.I., 2006, Geoenvironmental Problems of Mineral Resources Development, in ''Geology and Ecosystems'', Zekster (Ru), Marker (UK), Ridgeway (UK), Rogachevskaya (Ru), & Vartanyan (Ru), 2006 Springer Inc.,</ref> The majority of radioactive waste is "[[low-level waste]]", meaning it has low levels of radioactivity per [[mass]] or [[volume]]. This type of waste often consists of used protective clothing, which is only slightly contaminated but still dangerous in case of [[radioactive contamination]] of a human body through [[ingestion]], [[inhalation]], [[absorption (skin)|absorption]], or [[injection (medicine)|injection]].
In the [[United States]] alone, the [[United States Department of Energy|Department of Energy]] states that 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] - "[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]." Retrieved on [[8 April]] [[2007]].</ref> Despite these copious quantities of waste, the DOE has a goal of cleaning all presently contaminated sites successfully by 2025.<ref name="usemdoefyp"/> The [[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 currently has at least 108 sites it currently designates as areas that are contaminated and unusable, sometimes many thousands of acres<ref>American Scientist Jan/Feb 2007</ref><ref name="usemdoefyp"/> The DOE wishes to try and clean or mitigate many or all by 2025, however the task can be difficult and it acknowledges that some will never be completely remediated, and just in one of these 108 larger designations, [[Oak Ridge National Laboratory]], there were for example at least "167 known contaminant release sites" in one of the three subdivisions of the {{convert|37000|acre|sqkm|0|sing=on|lk=on}} site.<ref name="usemdoefyp"/> Some of the U.S. sites were smaller in nature, however, and cleanup issues were simpler to address, and the DOE has successfully completed cleanup, or at least closure, of several sites.<ref name="usemdoefyp"/>
The issue of disposal methods for nuclear waste was one of the most pressing current problems the international nuclear industry faced when trying to establish a long term energy production plan, yet there was hope it could be safely solved. In the U.S., the DOE acknowledged much progress in addressing the waste problems of the industry, and successful remediation of some contaminated sites, yet also major uncertainties and sometimes complications and setbacks in handling the issue properly, cost effectively, and in the projected time frame.<ref name="usemdoefyp"/> In other countries with lower ability or will to maintain environmental integrity the issue would be more problematic.
==Sources of waste==
===NORM (naturally occurring radioactive material)===
Processing of substances containing natural radioactivity; this is often known as NORM. A lot of this waste is [[alpha particle]]s 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]]).
==== Coal ====
[[Coal]] contains a small amount of radioactive nuclides, such as uranium and thorium, but it is less than the average concentration of those elements in the [[Earth's crust]]{{Fact|date=February 2007}}. They become more concentrated in the [[fly ash]] because they do not burn well [http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html]. However, the radioactivity of fly ash is still very low. It 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.[http://geology.cr.usgs.gov/energy/factshts/163-97/FS-163-97.html].
==== Oil and gas ====
Residues from the [[petroleum|oil]] and [[natural gas|gas]] industry often contain [[radium]] and its daughters. The sulphate scale from an oil well can be very radium rich, while the water, oil and gas from a well often contains [[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 as propane.<ref>[http://www.enprotec-inc.com/Presentations/NORM.pdf Survey & Identification of NORM Contaminated Equipment]</ref>
==== Mineral processing ====
Wastes from mineral processing can contain natural radioactivity; the largest source of this are phosphate mining operations.
=== Medical ===
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 trash. Other isotopes used in medicine, with half-lives in parentheses:
*[[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, external radiotherapy (30 years)
=== Industrial ===
[[Industry|Industrial]] source waste can contain [[alpha decay|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.[http://www.logwell.com/tech/nuclear/index.html]
=== Nuclear fuel cycle ===
{{main|Nuclear fuel cycle|Spent nuclear fuel}}
====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 not very radioactive - only 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.
The main by-product of enrichment is [[depleted uranium]] (DU), principally the [[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 the keels of yachts, and [[anti-tank]] [[KE-penetrator|shell]]s. It is also used (with recycled plutonium) for making [[mixed oxide fuel]] (MOX) and to dilute highly enriched uranium from weapons stockpiles which is now being redirected to become reactor fuel. This dilution, also called [[enriched uranium#Downblending|downblending]], means that any nation or group that acquired the finished fuel would have to repeat the (very expensive and complex) enrichment process before assembling a weapon.
==== Back end====
{{Medium-lived fission products}}
{{Long-lived fission products}}
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]], [[neptunium-237]], [[plutonium-238]] and [[americium-241]], and even sometimes some neutron emitters such as [[californium]] (Cf). 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. 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. Currently, in the U.S., this used fuel is stored. In other countries, such as the United Kingdom, France, and Japan, the fuel is reprocessed to remove the fission products, and the fuel can then be re-used. This reprocessing involves handling highly radioactive materials, and the fission products removed from the fuel are a concentrated form of High Level Waste as are the chemicals used in the process.
==== Proliferation concerns ====
{{main|nuclear proliferation}}
When dealing with uranium and plutonium, the possibility that they may be used to build [[nuclear weapon]]s is often a concern. Active nuclear reactors and nuclear weapons stockpiles are very carefully safeguarded and controlled. However, high-level waste from nuclear reactors may contain plutonium. Ordinarily, this plutonium is [[Plutonium#Manufacture|reactor-grade plutonium]], containing a mixture of [[plutonium-239]] (highly suitable for building nuclear weapons), [[plutonium-240]] (an undesirable contaminant and highly radioactive), [[plutonium-241]], and [[plutonium-238]]; these isotopes are difficult to separate. Moreover, high-level waste is full of highly radioactive [[fission products]]. However, most fission products are relatively short-lived. This is a concern since if the waste is stored, perhaps in [[deep geological repository|deep geological storage]], over many years the fission products decay, decreasing the radioactivity of the waste and making the plutonium easier to access. Moreover, 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). 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 point out that the half-life of Pu-240 is 6,560 years and Pu-239 is 24,110 years, and thus the relative enrichment of one isotope to the other with time occurs with a half-life of 9,000 years (that is, it takes 9000 years for the ''fraction'' of Pu-240 in a sample of mixed plutonium isotopes, to spontaneously decrease by half-- a typical enrichment needed to turn reactor-grade into weapons-grade Pu). Thus "weapons grade plutonium mines" would be a problem for the very far future (>9,000 years from now), so that there remains a great deal of time for technology to advance to solve this problem, before it becomes acute.
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 to serve as 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. But the very existence of the [[nuclear fuel reprocessing plant]] needed to separate the plutonium from the other elements represents, in the minds of some, a proliferation concern. In [[Integral Fast Reactor|pyrometallurgical fast reactors]], the waste generated is an actinide compound that cannot be used for nuclear weapons.
=== Nuclear weapons reprocessing ===
Waste from [[nuclear weapon]]s reprocessing (as opposed to production, which requires primary processing from reactor fuel) 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 bombs, plus some material with much higher specific activities, such as Pu-238 or Po.
In the past the neutron trigger for a 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 bombs are normally not released to the open literature. It is likely however that a D-T [[Nuclear fusion|fusion]] reaction in either an electrically driven device or a D-T fusion reaction driven by the chemical explosives would be used to start up a modern device.
Some designs might well contain a [[radioisotope thermoelectric generator]] using Pu-238 to provide a longlasting source of electrical power for the electronics in the device.
It is likely that the fissile material of an old bomb which is due for refitting will contain decay products of the plutonium isotopes used in it, these are likely to include alpha-emitting [[Np-236]] from Pu-240 impurities, plus some U-235 from decay of the Pu-239; however, 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#Non_aqueous_methods|pyrochemical]] processes and aqueous/organic [[solvent extraction]]. A truncated [[PUREX]] type extraction process would be one possible method of making the separation.
==Basic overview==
=== Physics ===
The radioactivity of all nuclear waste diminishes with time. All [[radioisotope]]s contained in the waste have a [[half-life]] - the time it takes for any radionuclide to lose half of its radioactivity and eventually all radioactive waste decays into non-radioactive elements. Certain radioactive elements (such as plutonium-239) in “spent” fuel will remain hazardous to humans and other living beings for hundreds of thousands of years. Other radioisotopes will remain hazardous for millions of years. Thus, these wastes must be shielded for centuries and isolated from the living environment for hundreds of millennia [http://www.nirs.org/radwaste/radwaste.htm]. Some elements, such as [[Iodine-131]], have a short half-life (around 8 days in this case) and thus they will cease to be a problem much more quickly than other, longer-lived, decay products but their activity is much greater initially.
The faster a [[radioisotope]] decays, the more radioactive it will be. The energy and the type of the [[ionizing radiation]] emitted by a pure radioactive substance are important factors in deciding how dangerous it will be. The chemical properties of the radioactive [[chemical element|element]] will determine how mobile the substance is and how likely it is to spread into the environment and contaminate human bodies. This is further complicated by the fact that many radioisotopes do not decay immediately to a stable state but rather to a radioactive [[decay product]] leading to [[decay chain]]s.
=== Chemistry ===
The chemical properties of the radioactive substance and the other substances found within (and near) the waste store has a great effect upon the ability of the waste to cause harm to humans or other organisms. For instance [[pertechnate|TcO<sub>4</sub><sup>-</sup>]] tends to [[Adsorption|adsorb]] on the surfaces of steel objects<ref name="schwochau"/> which reduces its ability to move out of the waste store in water.
=== Pharmacokinetics ===
Depending on the decay mode and the [[pharmacokinetics]] of an element (how the body processes it and how quickly), the threat due to exposure to a given activity of a [[radioisotope]] will differ. For instance I-131 is a short-lived [[beta decay|beta]] and [[gamma decay|gamma]] emitter but because it concentrates in the [[thyroid]] gland, it is more able to cause injury than [[cesium]]-137 which, being water soluble, is rapidly excreted in urine. In a similar way, the [[alpha decay|alpha]] emitting actinides and [[radium]] are considered very harmful as they tend to have long [[Biological half-life|biological half-lives]] and their radiation has a high linear energy transfer value. Because of such differences, the rules determining biological injury differ widely according to the radioisotope, and sometimes also the nature of the chemical compound which contains the radioisotope.
=== Philosophy ===
The main objective in managing and disposing of radioactive (or other) waste is to protect people and the environment. This means isolating or diluting the waste so that the rate or concentration of any radionuclides returned to the [[biosphere]] is harmless. To achieve this the preferred technology to date has been deep and secure burial for the more dangerous wastes; [[nuclear transmutation|transmutation]], long-term retrievable storage, and removal to space have also been suggested.
The phrase which sums up the area is ' ''Isolate from man and his environment'' ' until the waste has decayed such that it no longer poses a threat.
=== Fiction ===
In [[fiction]], radioactive waste is often cited as the reason for gaining [[super-human]] powers and abilities. An example of this fictional scenario is the 1981 movie "[[Modern Problems]]" in which actor [[Chevy Chase]] portrays a jealous, harried air traffic controller Max Fiedler; Max Fiedler, recently dumped by his girlfriend, comes into contact with nuclear waste and is granted the power of telekinesis, which he uses to not only win her back, but to gain a little revenge. Another more widely known character affected by a bite from a radioactive spider is [[Spider-man]]. The Spider-man character was developed by [[Marvel Comics]] (see also [[Stan Lee]]) and was portrayed on the big screen by actor [[Tobey Macguire]] in three films: the first in 2002, the second in 2004 and the third in 2007. In the film franchise, however, it is a bioengineered spider that bites him and changes his genetic makeup.
In most movies and cartoons, radioactive waste in any form is portrayed as [[steel]] [[barrels]] labeled with the classic radiation [[hazard symbol]], and full of thick, glowing, [[neon]]-green liquid. People, animals or objects that have come in contact with radiation or are radioactive themselves are usually shown with a bright green glow around them as well, and sometimes undergo hideous mutations such as the sudden growth of extra body parts, disfigurements, or turning into half-animal hybrids (if a person is bitten by a radioactive animal, much like in [[werewolf]] lore). This is often used for comical effect. Most radioactive material in real life however, is neither green nor luminescent (though some have been known to [[glow in the dark]]).
In [[reality]], exposure to high levels of radioactive waste may cause serious harm or [[death]]. It is interesting to note that the treatment of an [[adult]] animal with [[radiation]] or some other [[mutation]] causing effect, such as a cytotoxic anti-[[cancer]] [[drug]], cannot cause that adult animal to become a mutant. It is more likely that a cancer will be induced in the animal. In humans it has been calculated that a 1 [[sievert]] dose has a 5% chance of causing cancer and a 1% chance of causing a mutation in a [[gamete]] (e.g. [[egg (biology)|egg]]) or a gamete forming cell such as those in the [[testis]] which can be passed to the next generation. If a developing organism such as an [[unborn child]] is irradiated, then it is possible to induce a [[birth defect]] but it is unlikely that this defect will be in a gamete or a gamete forming [[cell (biology)|cell]].
== Types of radioactive waste ==
[[Image:Fort-greely-low-level-waste.jpg|thumb|right|Removal of very low-level waste]]
Although not significantly radioactive, '''uranium mill tailings''' are waste. They are byproduct material from the rough processing of uranium-bearing ore. They are sometimes referred to as 11(e)2 wastes, from the section of the U.S. Atomic Energy Act that defines them. Uranium mill tailings typically also contain chemically-hazardous heavy metals such as [[lead]] and [[arsenic]]. Vast mounds of uranium mill tailings are left at many old mining sites, especially in [[Colorado]], [[New Mexico]], and [[Utah]].
'''[[Low level waste]] (LLW)''' is generated from hospitals and industry, as well as the [[nuclear fuel cycle]]. It comprises paper, rags, tools, clothing, filters, etc., which contain small amounts of mostly short-lived radioactivity. Commonly, LLW is designated as such as a precautionary measure if it originated from any region of an 'Active Area', which frequently includes offices with only a remote possibility of being contaminated with radioactive materials. Such LLW typically exhibits no higher radioactivity than one would expect from the same material disposed of in a non-active area, such as a normal office block. Some high activity LLW requires shielding during handling and transport but most LLW is suitable for shallow land burial. To reduce its volume, it is often compacted or incinerated before disposal. Low level waste is divided into four classes, class A, B, C and GTCC, which means "Greater Than Class C".
'''Intermediate level waste (ILW)''' contains higher amounts of radioactivity and in some cases requires shielding. ILW includes [[resin]]s, chemical [[sludge]] and metal reactor [[nuclear fuel|fuel]] cladding, as well as contaminated materials from reactor decommissioning. It may be solidified in concrete or bitumen for disposal. As a general rule, short-lived waste (mainly non-fuel materials from reactors) is buried in shallow repositories, while long-lived waste (from fuel and fuel-reprocessing) is deposited in [[geological repository|deep underground facilities]]. U.S. regulations do not define this category of waste; the term is used in Europe and elsewhere.
[[Image:Nuclear waste flask train at Bristol Temple Meads 02.jpg|thumb|right|High Level Waste flasks are transported by train in the United Kingdom. Each flask is constructed of 3ft thick solid steel and weighs in excess of 50 tons]]
'''[[High level waste|High Level Waste]] (HLW)''' is produced by [[nuclear reactor]]s. It contains [[fission products]] and [[transuranic]] elements generated in the [[reactor core]]. It is highly radioactive and often thermally hot. HLW accounts for over 95% of the total radioactivity produced in the process of nuclear [[electricity generation]].
'''Transuranic waste (TRUW)''' as defined by U.S. regulations is, without regard to form or origin, waste that is contaminated with alpha-emitting transuranic radionuclides with half-lives greater than 20 years, and concentrations greater than 100 [[curie|nCi]]/g (3.7 [[becquerel|MBq]]/kg), excluding High Level Waste. Elements that have an [[atomic number]] greater than uranium are called transuranic ("beyond uranium"). Because of their long half-lives, TRUW is disposed more cautiously than either low level or intermediate level waste. In the U.S. it arises mainly from weapons production, and consists of clothing, tools, rags, residues, debris and other items contaminated with small amounts of radioactive elements (mainly plutonium).
Under U.S. law, TRUW is further categorized into "contact-handled" (CH) and "remote-handled" (RH) on the basis of radiation dose measured at the surface of the waste container. CH TRUW has a surface dose rate not greater than 200 [[Röntgen equivalent man|mrem]] per hour (2 [[millisievert|mSv]]/h), whereas RH TRUW has a surface dose rate of 200 [[Röntgen equivalent man|mrem]] per hour (2 mSv/h) or greater. CH TRUW does not have the very high radioactivity of high level waste, nor its high heat generation, but RH TRUW can be highly radioactive, with surface dose rates up to 1000000 [[Röntgen equivalent man|mrem]] per hour (10000 mSv/h). The United States currently permanently disposes of TRUW generated from nuclear power plants and military facilities at the [[Waste Isolation Pilot Plant]].<ref>[http://www.wipp.energy.gov/fctshts/whywipp.pdf Why WIPP?]</ref>
=== Management of medium level waste ===
It is common for medium active wastes in the nuclear industry to be treated with [[ion exchange]] or other means to concentrate the radioactivity into a small volume. The much less radioactive bulk (after treatment) is often then discharged. For instance, it is possible to use a [[ferric]] [[hydroxide]] [[floc]] to remove radioactive metals from aqueous mixtures [http://www.euronuclear.org/info/encyclopedia/w/waste-processing.htm]. After the radioisotopes are absorbed onto the ferric hydroxide, the resulting sludge can be placed in a metal drum before being mixed with cement to form a solid waste form.<!-- Dead links: [http://www.shef.ac.uk/isl/papers/NCCLeeds2003ExAbs.pdf][http://www.shef.ac.uk/isl/papers/NCCCSS2004ExAbs.pdf] --><ref>[http://sti.srs.gov/fulltext/ms2003759/ms2003759.pdf Removal of Silicon from High Level Waste Streams via Ferric Flocculation]</ref> In order to get better long-term performance (mechanical stability) from such forms, they may be made from a mixture of [[fly ash]], or [[blast furnace]] [[slag]], and [[portland cement]], instead of normal [[concrete]] (made with [[portland cement]], gravel and sand).
=== Management of high level waste ===
==== Storage ====
High-level radioactive waste is stored temporarily in [[spent fuel pool]]s and in [[dry cask storage]] facilities. This allows the shorter-lived isotopes to decay before further handling.
Long-term storage of radioactive waste requires the stabilization of the waste into a form which will not react, nor degrade, for extended periods of time. One way to do this is through [[vitrification]]. Currently at [[Sellafield]], England the high-level waste ([[PUREX]] first cycle [[raffinate]]) is mixed with [[sugar]] and then calcined. [[Calcination]] involves passing the waste through a heated, rotating tube. The purposes of calcination are to evaporate the water from the waste, and de-nitrate the fission products to assist the stability of the glass produced.
The 'calcine' generated is fed continuously into an induction heated furnace with fragmented [[glass]][http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=6510132]. The resulting glass is a new substance in which the waste products are bonded into the glass matrix when it solidifies. This product, as a molten fluid, is poured into [[stainless steel]] cylindrical containers ("cylinders") in a batch process. When cooled, the fluid solidifies ("vitrifies") into the glass. Such glass, after being formed, is very highly resistant to water. [http://www.shef.ac.uk/isl/papers/MIOCorrosionICG2004paper.pdf] According to the ITU, it will require about 1 million years for 10% of such glass to dissolve in water.
After filling a cylinder, a seal is [[weld]]ed onto the cylinder. The cylinder is then washed. After being inspected for external contamination, the steel cylinder is stored, usually in an underground repository. In this form, the waste products are expected to be immobilized for a very long period of time (many thousands of years).
The glass inside a cylinder is usually a black glossy substance. All this work (in the [[United Kingdom]]) is done using [[hot cell]] systems. The sugar is added to control the [[ruthenium]] chemistry and to stop the formation of the volatile RuO<sub>4</sub> containing [[Ru-106|radioruthenium]]. In the west, the glass is normally a [[borosilicate glass]] (similar to [[Pyrex]] {''NB'' Pyrex is a trade name}), while in the former [[Soviet]] bloc it is normal to use a [[phosphate]] glass. The amount of fission products in the glass must be limited because some ([[palladium]], the other Pt group metals, and [[tellurium]]) tend to form metallic phases which separate from the glass. In Germany a vitrification plant is in use; this is treating the waste from a small demonstration reprocessing plant which has since been closed down.
In 1997, in the 20 countries which account for most of the world's nuclear power generation, spent fuel storage capacity at the reactors was 148,000 tonnes, with 59% of this utilized. However, a number of nuclear power plants in countries that do not reprocess had nearly filled their spent fuel pools, and resorted to Away-from-reactor storage (AFRS). AFRS capacity in 1997 was 78,000 tonnes, with 44% utilized, and annual additions of about 12,000 tonnes. AFRS cannot be expanded forever, and the lead times for final disposal sites have proven to be unpredictable (see below).
In 1989 and 1992, France commissioned commercial plants to [[vitrification|vitrify]] HLW left over from reprocessing oxide fuel, although there are adequate facilities elsewhere, notably in the United Kingdom and [[Belgium]]. The capacity of these western European plants is 2,500 canisters (1000 t) a year, and some have been operating for 18 years.
==== Synroc ====
The Australian [[Synroc]] (synthetic rock)[http://oliver.geology.adelaide.edu.au/staff/jbrugger/Research/radioactive_waste.html] is a more sophisticated way to immobilize such waste, and this process may eventually come into commercial use for civil wastes (it is currently being developed for U.S. military wastes). The Synroc contains [[pyrochlore]] and [[cryptomelane]] type minerals. The original form of Synroc (Synroc C) was designed for the liquid high level waste (PUREX raffinate) from a [[light water reactor]]. The main minerals in this Synroc are [[hollandite]] (BaAl<sub>2</sub>Ti<sub>6</sub>O<sub>16</sub>), [[zirconolite]] (CaZrTi<sub>2</sub>O<sub>7</sub>) and [[perovskite]] (CaTiO<sub>3</sub>). The zirconolite and perovskite are hosts for the [[actinides]]. The [[strontium]] and [[barium]] will be fixed in the perovskite. The [[caesium]] will be fixed in the hollandite.
Synroc was invented by the late Prof Ted Ringwood (a [[geochemist]]) at the [[Australian National University]].
[[Image:Nuclear waste locations USA.jpg|right|350px|thumb|Nuclear waste locations in USA]]
==== Geological disposal ====
The process of selecting appropriate [[Deep geological repository|deep final repositories]] is now under way in several countries with the first expected to be commissioned some time after 2010. However, many people remain uncomfortable with the immediate [[stewardship cessation]] of this management system. In Switzerland, the Grimsel Test Site is an international research facility investigating the open questions in radioactive waste disposal ([http://www.grimsel.com]). [[Sweden]] is well advanced with plans for direct disposal of spent fuel, since its Parliament decided that this is acceptably safe, using the [[KBS-3]] technology. In [[Germany]], there is a political discussion about the search for an ''Endlager'' (final repository) for radioactive waste, accompanied by loud protests especially in the [[Gorleben]] village in the [[Lüchow-Dannenberg|Wendland]] area, which was seen ideal for the final repository until 1990 because of its ___location next to the border to the former [[German Democratic Republic]]. Gorleben is presently being used to store radioactive waste non-permanently, with a decision on final disposal to be made at some future time. The U.S. has opted for a final repository at [[Yucca Mountain]] in Nevada, but this project is widely opposed and is a hotly debated topic, and one of the main concerns is with the long distance transportation of the waste from across the United States to this area, and the possible several accidents over time that would occur. There is also a proposal for an international HLW repository in optimum geology, with Australia or Russia as possible locations, although the proposal for a global repository for Australia has raised fierce domestic political objections.
The Canadian government, for example, is seriously considering this method of disposal, known as the ''Deep Geological Disposal'' concept. Under the current plan, a vault is to be dug 500 to 1000 meters below ground, under the [[Canadian Shield]], one of the most stable landforms on the planet. The vaults are to be dug inside geological formations known as ''[[batholith]]s'', formed about a billion years ago. The used fuel bundles will be encased in a corrosion-resistant container, and further surrounded by a layer of ''buffer material'', possibly of a special kind of clay ([[bentonite|bentonite clay]]). The case itself is designed to last for thousands of years, while the clay would further slow the corrosion rates of the container. The batholiths themselves are chosen for their low ground-water movement rates, geological stability, and low economic value.<ref name="NuclearFAQ">{{cite web|title=How is high-level nuclear waste managed in Canada?|work=The Canadian Nuclear FAQ|url=http://www.nuclearfaq.ca/cnf_sectionE.htm#v|accessdate=June 28|accessyear=2006}}</ref>
The Finnish government has already started building a vault to store nuclear waste 500 to 1000 meters below ground, not far from the nuclear plant at [[Olkiluoto]].
Storing high level nuclear waste above ground for a century or so is considered appropriate by many scientists. This allows for the material to be more easily observed and any problems detected and managed, while the decay over this time period significantly reduces the level of radioactivity and the associated harmful effects to the container material. It is also considered likely that over the next century newer materials will be developed which will not break down as quickly when exposed to a high neutron flux thus increasing the longevity of the container once it is permanently buried.
Sea-based options for disposal of radioactive waste [http://www.scientiapress.com/findings/sea-based.htm] include burial beneath a stable [[abyssal plain]], burial in a [[subduction]] zone that would slowly carry the waste downward into the [[mantle (geology)|Earth's mantle]], and burial beneath a remote natural or human-made island. While these approaches all have merit and would facilitate an international solution to the vexing problem of disposal of radioactive waste, they are currently not being seriously considered because of the legal barrier of the [[United Nations Convention on the Law of the Sea|Law of the Sea]] and because in [[North America]] and [[Europe]] sea-based burial has become taboo from fear that such a repository could leak and cause widespread damage. Dumping of radioactive waste from ships has reinforced this concern, as has contamination of islands in the Pacific. However, sea-based approaches might come under consideration in the future by individual countries or groups of countries that cannot find other acceptable solutions.
A more feasible approach termed Remix & Return [http://www.scientiapress.com/findings/r&r.htm] would blend high-level waste with [[uranium mining|uranium mine]] and mill tailings down to the level of the original radioactivity of the [[uraninite|uranium ore]], then replace it in empty uranium mines. This approach has the merits of totally eliminating the problem of high-level waste, of placing the material back where it belongs in the natural order of things, of providing jobs for miners who would double as disposal staff, and of facilitating a cradle-to-grave cycle for all radioactive materials.
==== Transmutation ====
There have been proposals for reactors that consume nuclear waste and transmute it to other, less-harmful nuclear waste. In particular, the [[Integral Fast Reactor]] was a proposed nuclear reactor with a [[nuclear fuel cycle]] that produced no transuranic waste and in fact, could consume transuranic waste. It proceeded as far as large-scale tests but was then canceled by the U.S. Government. Another approach, considered safer but requiring more development, is to dedicate [[subcritical reactor]]s to the [[transmutation]] of the left-over transuranic elements.
There have also been theoretical studies involving the use of [[fusion reactor]]s as so called "actinide burners" where a fusion reactor [[plasma (physics)|plasma]] such as in a [[tokamak]], could be "doped" with a small amount of the "minor" transuranic atoms which would be transmuted (meaning fissioned in the actinide case) to lighter elements upon their successive bombardment by the very high energy neutrons produced by the fusion of [[deuterium]] and [[tritium]] in the reactor. It was recently found by a study done at [[MIT]], that only 2 or 3 fusion reactors with parameters similar to that of the [[International Thermonuclear Experimental Reactor]] (ITER) could transmute the entire annual [[minor actinide]] production from all of the [[light water reactor]]s presently operating in the [[List_of_nuclear_reactors#Power_station_reactors_18|United States fleet]] while simultaneously generating approximately 1 [[gigawatt]] of power from each reactor[http://web.mit.edu/annualreports/pres01/13.07.html].
==== Reuse of waste ====
Another option is to find applications of the isotopes in nuclear waste so as to [[reuse]] them. [http://www.heritage.org/Research/EnergyandEnvironment/upload/86845_1.pdf] <!-- (archived PDF document, with a few errors in it) -->. Already, [[cesium-137]], [[strontium-90]] and a few other isotopes are extracted for certain industrial applications such as [[food irradiation]] and [[radioisotope thermoelectric generators]].
==== Space disposal====
Space disposal is an attractive notion because it permanently removes nuclear waste from the environment. However, it has significant disadvantages, not least of which is the potential for catastrophic failure of a [[launch vehicle]]. Furthermore, the high number of launches that would be required makes the proposal impractical. To further complicate matters, international agreements on the regulation of a such a program would need to be established.[http://www.ocrwm.doe.gov/factsheets/doeymp0017.shtml]
== Accidents involving radioactive waste ==
A number of incidents have occurred when radioactive material was disposed of improperly, shielding during transport was defective, or when it was simply abandoned or even stolen from a waste store.<ref>http://www.iaea.org/Publications/Magazines/Bulletin/Bull413/article1.pdf</ref> In the former Soviet Union, a nation having a high level of technical expertise and experience with nuclear issues, waste stored in [[Lake Karachay]] was accidentally blown all over the area during a dust storm after the lake had dried out. One still must not stop their car when driving through for any reason. In other cases lakes or ponds with radioactive waste accidentally overflowed into the rivers during exceptional storms.{{Fact|date=February 2007}}
Scavenging of abandoned radioactive material has been the cause of several other cases of [[radiation exposure]], mostly in [[developing nation]]s, which usually have less regulation of dangerous substances (and sometimes less general education about radioactivity and its hazards) and a market for scavenged goods and scrap metal. The scavengers and those who buy the material are almost always unaware that the material is radioactive and it is selected for its [[aesthetics]] or scrap value.{{Fact|date=February 2007}} A few are aware of the radioactivity, but are either ignorant of the risk or believe that the material's value outweighs the danger.{{Fact|date=February 2007}} Irresponsibility on the part of the radioactive material's owners, usually a hospital, university or military, and the absence of regulation concerning radioactive waste, or a lack of enforcement of such regulations, have been significant factors in radiation exposures. For details of radioactive scrap see the [[Goiânia accident]].
Transportation accidents involving spent nuclear fuel from power plants are unlikely to have serious consequences due to the strength of the [[spent nuclear fuel shipping cask]]s (see that article).
==See also==
{{EnergyPortal}}
*[[Global Nuclear Energy Partnership]]
*[[Hot cell]]
*[[Geomelting]]
*[[Radioactive scrap metal]]
*[[Yucca Mountain]] proposed nuclear-waste storage facility
*[[List of nuclear accidents]]
*[[List of Superfund sites in the United States]]
*[[List of topics dealing with environmental issues]]
*[[List of waste management companies]]
*[[List of waste management topics]]
*[[List of solid waste treatment technologies]]
*[[Nuclear power]]
*[[Pollution]]
*[[Toxic waste]]
*[[Remediation]]
*[[Recycling]]
*[[Superfund]]
*[[Stored Waste Examination Pilot Plant]]
*[[Waste types]]
*[[Waste management]]
==References==
{{reflist}}
Fentiman, Audeen W. and James H. Saling. ''Radioactive Waste Management''. New York: Taylor & Francis, 2002. Second ed.
An overview of waste from the nuclear fuel cycle was written by B.V. Babu and S. Karthik, ''Energy Education Science and Technology'', 2005, '''14''', 93-102.
==External links==
* [http://web.em.doe.gov/lowlevel/llw_apxc.html Key Radionuclides and Generation Processes] ([[United States Department of Energy|DOE]])
* [http://alsos.wlu.edu/qsearch.aspx?browse=science/Nuclear+Waste Alsos Digital Library - Radioactive Waste] (bibliography)
* [http://www.sckcen.be/sckcen_en/activities/index.shtml Belgian Nuclear Research Centre - Activities] (documents and links)
* [http://www.sckcen.be/sckcen_en/publications/scientrep/ Belgian Nuclear Research Centre - Scientific Reports] (documents)
* [http://www.earthhealing.info/CH.pdf Critical Hour: Three Mile Island, The Nuclear Legacy, And National Security] (PDF)
* [http://www.epa.gov/radiation/yucca/index.html Environmental Protection Agency - Yucca Mountain] (documents)
* [http://www.grist.org/news/maindish/2006/08/08/stang/ Grist.org - How to tell future generations about nuclear waste] (article)
* [http://www.thefirstpost.co.uk/index.php?menuID=1&subID=848 A discussion on the secrecy surrounding plans for radioactive waste in the UK ] (article)
*[http://www.iaea.org/worldatom/Programmes/Nuclear_Energy/NEFW/index.html International Atomic Energy Agency - Nuclear Fuel Cycle and Waste Technology Program] (program objectives)
*[http://www.iaea.org/inis/ws/subjects/nuclear_facilities.html International Atomic Energy Agency - Internet Directory of Nuclear Resources] (links)
* [http://www.nuclearfiles.org/menu/key-issues/nuclear-energy/issues/yucca-mountain/index.htm Nuclear Files.org - Yucca Mountain] (documents)
*[http://www.nrc.gov/waste.html Nuclear Regulatory Commission - Radioactive Waste] (documents)
* [http://www.nrc.gov/reading-rm/doc-collections/reg-guides/fuels-materials/active/03-054/ Nuclear Regulatory Commission - Spent Fuel Heat Generation Calculation] (guide)
* [http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html Oak Ridge National Laboratory - Coal Combustion: Nuclear Resource or Danger] (document)
* [http://radwaste.org Radwaste.org] (links)
* [http://radwaste.blogspot.com Radwaste Blog] (weblog)
* [http://samvak.tripod.com/brief-nuclearwaste01.html Surviving on Nuclear Waste] (book)
*[http://www.phyast.pitt.edu/~blc/book/chapter11.html The Nuclear Energy Option - Hazards of High-Level Radioactive Waste] (book)
* [http://earthwatch.unep.net/radioactivewaste/index.php UNEP Earthwatch - Radioactive Waste] (documents and links)
* [http://www.uic.com.au/nip.htm#Radioactive%20Wastes Uranium Information Center - Radioactive Waste] (briefing papers)
* [http://greenwood.cr.usgs.gov/energy/factshts/163-97/FS-163-97.html United States Geological Survey - Radioactive Elements in Coal and Fly Ash] (document)
* [http://world-nuclear.org/info/info.htm#radioactivewastes World Nuclear Association - Radioactive Waste] (briefing papers)
* [http://www.uic.com.au/wast.htm Radioactive Waste Management, by UIC]
{{waste}}
{{Nuclear Technology}}
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