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SOURCES OF WASTE NORM (naturally occurring radioactive material) Processing of substances containing natural radioactivity, this is often known as NORM . Much of this waste is Alpha Particles emitting matter from the decay chains of Uranium and Thorium . Coal 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. {Link without Title} . Oil and gas Residues from the Oil and 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. {Link without Title} Mineral processing Wastes from mineral processing can contain natural radioactivity. Medical Radioactive Medical waste tends to contain Beta Ray 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 99mTc 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:
Industrial Indusheytrial source waste can contain Alpha , Beta , 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. {Link without Title} Nuclear fuel cycle 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. 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 (UO2) 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 Yellow Cake (U3O8), then converted to Uranium Hexafluoride gas (UF6). As a gas, it undergoes Enrichment to increase the 235U content from 0.7% to about 3.5% (LEU). It is then turned into a hard ceramic oxide (UO2) for assembly as reactor fuel elements. The main by-product of enrichment is Depleted Uranium (DU), principally the 238U isotope, with a 235U content of ~0.3%. It is stored, either as UF6 or as U3O8. Some is used in applications where its extremely high density makes it valuable, such as the keels of yachts, and Anti-tank 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 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 The back end of the of the nuclear fuel cycle, mostly spent Fuel Rod s, often contains Fission Product s that emit beta and gamma radiation, and may contain Actinide s that emit Alpha Particle s, such as 234U, 237Np, 238Pu and 241Am, and even sometimes some neutron emitters such as Cf. These isotopes are formed in Nuclear Reactor s. It's important to distinguish the processing of uranium to make fuel from the 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 Poisons 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 235U and Plutonium present. Currently, in the USA, this used fuel is stored. In other countries (the UK, France, and Japan in particular) the fuel is reprocessed to remove the fission products, and the fuel can then be re-used. The reprocessing process 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 When dealing with uranium and plutonium, the possibility that they may be used to build Nuclear Weapon s ( Nuclear Proliferation ) is often a consideration. 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 Reactor-grade Plutonium , containing a mixture of 239Pu (highly suitable for building nuclear weapons) and 240Pu (an undesirable contaminant and highly radioactive); the two 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 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 240Pu decays faster than the 239Pu, 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 since the half-life of 240Pu is 6,560 years and 239Pu is 24,110 years, 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 quantity of 240Pu in a sample of plutonium to spontaneously decrease by half), so that "weapons grade plutonium mines" would be a problem for the very far future, and there yet remains a great deal of time for technology to advance to solve the problem, before it becomes acute. 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 pyrometallurgical Fast Reactor s, the waste generated is an actinide compound that cannot be used for nuclear weapons. Nuclear weapons production Waste from Nuclear Weapon s production is unlikely to contain much beta or gamma activity other than Tritium . It is more likely to contain alpha emitting actinides such as 239Pu which is a fissile material used in bombs, some material with much higher specific activities, such as 238Pu or Po, have been used in neutron triggers or thermoelectric power sources used in weapon systems. 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. Eventually all radioactive waste decays into non-radioactive elements; for example, after 40 years 99.9% of radiation in spent nuclear fuel disappears {Link without Title} . The faster a Radioisotope is decaying, 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 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 Chains . Biochemistry Depending on the decay mode and the Biochemistry of an element, the threat due to exposure to a given activity of a Radioisotope will differ. For instance 131I is a short-lived Beta and Gamma emitter but because it concentrates in the Thyroid gland, it is more able to cause injury than 99mTcO4- which is spread throughout the body and is rapidly excreted. In a similar way, the Alpha emitting Actinide s and Radium are considered very harmful as they tend to have long Biological Half-lives and their radiation has a high linear energy transfer value. Because of these differences the rules often differ according to the radioisotope and the nature that the activity is in. 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; 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. For instance if a vial containing 1 Ci of 32P or 99mTc were left in a shielded place to decay, then after a year it would contain only a trace of activity. But 1 Ci of used nuclear fuel (1 year after irradiation in a reactor) or 137Cs would have a longer lifetime, and as a result this waste would need to be isolated from humans for longer. Fiction In Fiction , radioactive waste is often cited as the reason for gaining Super-human powers and abilities. In Reality , contact with radioactive waste is not good, and would be vastly more likely to cause serious harm or Death rather than an improvement. 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 , that it is impossible to cause that adult animal to become a mutant. It has 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 ) 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 a Unborn Child is irradiated then it is possible to induce a deformity or Birth Defect but it is unlikely that this defect will be in a gamete or a gamete forming Cell . TYPES OF RADIOACTIVE 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 waste 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 waste 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. No LLW waste requires shielding during handling and transport and 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 resins, chemical Sludge and metal Fuel cladding, as well as contaminated materials from reactor decommissioning. It may be solidified in concrete or bitumen for disposal. Generally short lived waste (mainly from reactors) is buried in shallow repositories, while long lived waste (from fuel reprocessing) is deposited in deep underground facilities. U.S. regulations do not define this category of waste; the term is used in Europe and elsewhere. High Level Waste (HLW) arises from the use of Uranium fuel in a Nuclear Reactor and nuclear weapons processing. It contains fission products and Transuranic elements generated in the reactor core. It is highly radioactive and 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 NCi/g , excluding High 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). 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. 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 Mrem per hour, whereas RH TRUW has a surface dose rate of 200 Mrem per hour 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 1000 Rem per hour. The United States currently permanently disposes of TRUW generated from nuclear power plants and military facilities at the Waste Isolation Pilot Plant . {Link without Title} Management of medium level waste It is common for medium active wastes in the nuclear industry to be treated with ( Portland Cement ) a mixture of Fly Ash or Blast Furnace Slag and Portland Cement can be used. Management of high level waste Storage High-level radioactive waste is stored temporarily in Spent Fuel Pool s and in Dry Cask Storage facilities. Vitrification , Russia]] 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 containers in a batch process. Thus, when cooled the waste products are immobilised for a very long period of time (many thousands of years). After filling, a seal is Weld ed onto the cylinder. The cylinder is then washed.After being inspected for external contamination, the steel cylinder is placed in a store. The glass inside is a black glossy substance. All this work (in the U.K. ) is done using Hot Cell systems. The sugar is added to control the Ruthenium chemistry and to stop the formation of the volatile RuO4. 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. The glass formed when placed in water will dissolve very slowly, {Link without Title} according to the ITU it will require about 1 million years for 10% of the glass to dissolve in water. 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. Away-from-reactor storage capacity was 78,000 tonnes, with 44% utilized. With annual additions of about 12,000 tonnes, issues for final disposal are not urgent. In 1989 and 1992, France commissioned commercial plants to Vitrify HLW left over from reprocessing oxide fuel, although there are adequate facilities elsewhere, notably in the UK 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 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 (BaAl2Ti6O16), Zirconolite (CaZrTi2O7) and Perovskite (CaTiO3). The zirconolite and perovskite are hosts for the Actinides . The Strontium and Barium will be fixed in the perovskite. The Cesium will be fixed in the hollandite. Synroc was invented by the late Prof Ted Ringwood (a Geochemist ) at the Australian National University . Geological disposal The process of selecting appropriate 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 Wendland area, which was seen ideal for the final repository until 1990 because of its location next to the border to the former GDR . 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 US has opted for a final repository at Yucca Mountain in Nevada, but this project is widely opposed and is a hotly debated topic. There is also a proposal for an international HLW repository in optimum geology, with Australia or Russia as possible locations; however, the proposal for a global repository for Australia has raised fierce domestic political objections, making such a dump unlikely. Sea-based options for disposal of radioactive waste {Link without Title} include burial beneath a stable abyssal plain, burial in a subduction zone that would slowly carry the waste downward into the 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 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, though the evidence that this would happen is lacking. Dumping of radioactive waste from ships has reinforced this taboo. 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 {Link without Title} would blend high-level waste with mine and mill tailings down to the level of the original radioactivity of the 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; in fact, it could consume transuranic waste. It proceeded as far as large-scale tests but was then canceled by the US Government. Another approach, considered safer but requiring more development, is to dedicate Subcritical Reactor s to the Transmutation of the left-over transuranic elements. Reuse of waste Another option is to find applications of the isotopes in nuclear waste so as to and RTG s. ACCIDENTS INVOLVING RADIOACTIVE WASTE While radioactive waste is not as sensitive to disruption as an active Nuclear Reactor , it is often treated as regular waste and forgotten. A number of incidents have occurred when radioactive material was disposed of improperly, simply abandoned or even stolen from a waste store. 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 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. A few are aware of the radioactivity, but are either ignorant of the risk or believe that the material's value outweighs the danger. 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 ALSO
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