Wastes nuclear

The problems with unwanted nuclear material, irrespective of its origin, are the same. Although 

Decommissioning and immediate dismantlement of nuclear power reactors at the end of their useful life (about 30-40 years) is both a challenge and expensive process because of the need to dispose large volumes of low-level wastes (LLW) in many countries today. For example, the volumes and activities estimated for immediate dismantlement of reference nuclear power reactors PWR 

Radionuclide Mode of decay Half-life (years) Activity (curies/kg U) At discharge After 1 year After 10 years 

Some alternate proposals for waste disposal include the following (a) the space option, (b) Antarctic ice shelf, (c) ocean dumping, (d) ocean burial, and (e) nuclear transformation. 

Canada is very fortunate in having the Canadian Shield of Precambrian rock formation in Central Canada around Hudson s Bay. Some hard rock formations, called pluton, within the shield are ideal sites for the location of an underground nuclear waste storage facility. 

Studies now in progress in an underground laboratory will establish the permeabdity and water movement in such formations. 

The fission products that accumulate as a reactor operates decrease the efficiency of the reactor by capturing neutrons. For this reason, commercial reactors must be stopped periodically to either replace or reprocess the nuclear fuel. When the fuel elements are removed from the reactor, they are initially very radioactive. It was originally intended that they be stored for several months in pools at the reactor site to allow decay of short-lived radioactive nuclei. They were then to be transported in shielded containers to reprocessing plants where the fuel would be separated from the fission products. Reprocessing plants have been plagued with operational difficulties, however, and there is intense opposition in the United States to the transport of nuclear wastes on the nation s roads. 

Even if the transportation difficulties could be overcome, the high level of radioactivity of the spent fuel makes reprocessing a hazardous operation. At present in the United States spent fuel elements are kept in storage at reactor sites. Spent fuel is reprocessed, however, in France, Russia, the United Kingdom, India, and Japan. 

Storage of spent nuclear fuel poses a major problem because the fission products are extremely radioactive. It is estimated that 20 half-lives are required for their radioactivity to reach levels acceptable for biological exposure. Based on the 28.8-yr half-life of strontium-90, one of the longer-lived and most dangerous of the products, the wastes must be stored for 600 years. Plutonium-239 is one of the by-products present in spent fuel elements. It is formed by absorption of a neutron by uranium-238, followed by two successive beta emissions. (Remember that most of the uranium in the fuel elements is uranium-238.) If the elements are reprocessed, the plutonium-239 is largely recovered because it can be used as a nuclear fiieL However, if the plutonium is not removed, spent elements must be stored for a very long time because plutonium-239 has a half-life of24,000 yr. 

One approach to getting more power out of existing uranium sources and potentially reducing radioactive waste is a fast breeder reactor. This type of reactor is so named because it creates ( breeds ) more fissionable material than it consumes. The reactor operates without a moderator, which means the neutrons used are not slowed down. In order to capture the fast neutrons, the fuel must be highly enriched with both ura-nium-235 and plutonium-239. Water cannot be used as a primary coolant because it 

Would moderate the neutrons, and so a liquid metal, usually sodium, is used. The core is surroimded by a blanket of uranium-238 that captures neutrons that escape the core, producing plutonium-239 in the process. The plutonium can later be separated by reprocessing and used as fuel in a future cy cle. 

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The advent of a portable source of very high energy x-rays has opened up x-ray inspection possibilities in a wide range of environments. Applications include such fields as nuclear waste containers, bridges, nuclear and fossil power plants, surface and airborne transportation systems, space launch systems and other thick section NDT and other inspection problems that cannot be solved imaged using other NDT methods. 

Ch. Lierse, H. Gobel, E. Kaciniel, R. Link, W. Nuding, Ch. Sauerwein, H. Wiacker Tomographic Inspection of nuclear Waste Containers... 

Use of Mobile Real-Time Radioscopic Systems for Inspection of Nuclear Waste Samples. 

Plutonium (Pu) is an artificial element of atomic number 94 that has its main radioactive isotopes at 2 °Pu and Pu. The major sources of this element arise from the manufacture and detonation of nuclear weapons and from nuclear reactors. The fallout from detonations and discharges of nuclear waste are the major sources of plutonium contamination of the environment, where it is trapped in soils and plant or animal life. Since the contamination levels are generally very low, a sensitive technique is needed to estimate its concentration. However, not only the total amount can be estimated. Measurement of the isotope ratio provides information about its likely... 

UCLEARREACTORS - WASTE MANAGETffiNT] (Vol 17) Nuclear waste management... 

Thorium, uranium, and plutonium are well known for their role as the basic fuels (or sources of fuel) for the release of nuclear energy (5). The importance of the remainder of the actinide group Hes at present, for the most part, in the realm of pure research, but a number of practical appHcations are also known (6). The actinides present a storage-life problem in nuclear waste disposal and consideration is being given to separation methods for their recovery prior to disposal (see Waste treati nt, hazardous waste Nuclear reactors, waste managet nt). 

Nuclear Waste Management. Separation of radioactive wastes provides a number of relatively small scale but vitally important uses of gas-phase purification appHcations of adsorption. Such appHcations often require extremely high degrees of purification because of the high toxicity of... 

Dioxygea difluoride has fouad some appHcatioa ia the coaversioa of uranium oxides to UF (66), ia fluoriaatioa of actinide fluorides and oxyfluorides to AcF (67), and in the recovery of actinides from nuclear wastes (68) (see Actinides and transactinides Nuclear reaction, waste managel nt). 

Pkctro-Keforming The concept of using electricity to provide the endothermic heat of reforming has been proposed. Nuclear waste heat can be contained in high temperature helium gas which is brought into heat exchange with a natural gas feedstock (142). 

F/uidi ed-BedIncinerator. Fluidized-bed incinerators are employed in the paper and petroleum (qv) industries, in the processing of nuclear wastes, and the disposal of sewage sludge. These are quite versatile and can be used for disposal of soflds, Hquids, and gaseous combustible wastes. 

Nuclear Waste News Occupational Health Safety Letter Occupational Safety Health Reporter 02one Depletion Network Online TODAY PressNet Environmental Reports Texas Industry Environmental Alert... 

Lead-loaded plastics containing up to 90 wt % lead are used in x-ray protection as aprons and temporary shields in medical and industrial appHcations. Leaded glass is used to attenuate radiation where viewing the ongoing process is requited. Steel-jacketed containers fihed with lead or special lead containers are used to transfer, ship, and store fuel rods, radioactive sources, and nuclear waste. Lead is generahy used where space is limited. 

Nuclear wastes are classified according to the level of radioactivity. Low level wastes (LLW) from reactors arise primarily from the cooling water, either because of leakage from fuel or activation of impurities by neutron absorption. Most LLW will be disposed of in near-surface faciHties at various locations around the United States. Mixed wastes are those having both a ha2ardous and a radioactive component. Transuranic (TRU) waste containing plutonium comes from chemical processes related to nuclear weapons production. These are to be placed in underground salt deposits in New Mexico (see... 

Mill tailings are another form of nuclear waste. The residue from uranium ore extraction contains radium, the precursor of short-Hved radon and its daughters. Piles of tailings must be properly covered. 

Classification of wastes may be according to purpose, distinguishing between defense waste related to military appHcations, and commercial waste related to civiUan appHcations. Classification may also be by the type of waste, ie, mill tailings, high level radioactive waste (HLW), spent fuel, low level radioactive waste (LLW), or transuranic waste (TRU). Alternatively, the radionucHdes and the degree of radioactivity can define the waste. Surveys of nuclear waste management (1,2) and more technical information (3—5) are available. 

Funding for developing commercial waste disposal faciUties is to come from the waste generators. In the case of spent fuel disposal, a Nuclear Waste Fund is accumulating based on an assessment of one mill per kilowatt-hour of electricity. For low level wastes, surcharges on waste disposal and direct assessments of utiUties have been imposed. 

N. A. Chapman and I. G. McKinley, The Geological Disposal of Nuclear Waste, John Wiley Sons, Ltd., Chichester, U.K., 1987. 

The League of Women Voters Education Eund, The Nuclear Waste Primer A Handbook for Citicyens, Lyons Burford, Pubhshers, New York, 1993. 

The sum total of risks of the nuclear fuel cycle, most of which are associated with conventional industrial safety, are greater than those associated with nuclear power plant operation (30,35—39). However, only 1% of the radiological risk is associated with the nuclear fuel cycle so that nuclear power plant operations are the dominant risk (40). Pubhc perception, however, is that the disposition of nuclear waste poses the dominant risk. 

Miscellaneous. Iridium dioxide, like RUO2, is useful as an electrode material for dimensionally stable anodes (DSA) (189). SoHd-state pH sensors employing Ir02 electrode material are considered promising for measuring pH of geochemical fluids in nuclear waste repository sites (190). Thin films (qv) ofIr02 ate stable electrochromic materials (191). 

Nuclear Waste Reprocessing. Liquid waste remaining from processing of spent reactor fuel for military plutonium production is typically acidic and contains substantial transuranic residues. The cleanup of such waste in 1996 is a higher priority than military plutonium processing. Cleanup requires removal of long-Hved actinides from nitric or hydrochloric acid solutions. The transuranium extraction (Tmex) process has been developed for... 

S. Fded and co-workers, in G. J. M. McCarthy, ed.. The Scientific Basis of Nuclear Waste Management, Matedals Research Society, Plenum Press, New York, 1979, pp. 655-664. 

R. C. Weisner, J. E. Lemons, Jr., and L. V. Coppa, Valuation oJPotash Occurrence Within the Nuclear Waste Isolation Pilot Plant Site in Southeastern Neir Mexico, U.S. Department of the Interior, Bureau of Mines, Washington, D.C., 1980, p. 6. 

Nuclear Waste. NRC defines high level radioactive waste to include (/) irradiated (spent) reactor fuel (2) Hquid waste resulting from the operation of the first cycle solvent extraction system, and the concentrated wastes from subsequent extraction cycles, in a faciHty for reprocessing irradiated reactor fuel and (3) soHds into which such Hquid wastes have been converted. Approximately 23,000 metric tons of spent nuclear fuel has been stored at commercial nuclear reactors as of 1991. This amount is expected to double by the year 2001. 

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