Waste radioactivity from solid

Nuclear Waste. NRC defines high level radioactive waste to include (/) irradiated (spent) reactor fuel (2) liquid waste resulting from the operation of the first cycle solvent extraction system, and the concentrated wastes from subsequent extraction cycles, in a facility for reprocessing irradiated reactor fuel and (3) solids into which such liquid 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. 

One of the more important factors affecting the isolation of radioactive waste is the rate of release of the radioactivity from the solid waste form to the environment. The most probable mechanism for release and transport of radioactivity from a solid waste form is by leaching of radioactive isotopes with groundwater. The objective of leach-testing various waste forms is to evaluate the rate at which specific hazardous radionuclides migrate from waste if and when the waste form comes in contact with groundwater. In this paper, measurement of leach rates of radioactive waste by a method which incorporates neutron activation is described. 

The simplest way to classify radioactive waste is by its physical state, that is, whether it is a gas, liquid, or solid. Gaseous waste arises from gas evolution,... 

The waste resulting from the above activities comes in various forms (i.e., gaseous, liquid, or solid). These wastes have different characteristics. For safety and technical reasons, the various forms of wastes are usually categorized by their levels of radioactivity, heat content, and potential hazard. 

Strontium is ubiquitous in the environment and is present in nearly all rocks and soils. It is released to land in solid waste and from the use of phosphate fertilizers. 90Sr is found in nearly all soils in the United States. 90Sr that is deposited at a specific site varies widely, depending primarily on rainfall. Intentional and unintentional releases of radioactive strontium have occurred at DOE sites across the country. 

Treatment of Caseous Waste. Gaseous wastes arise from the ventilation of process vessels and the concrete cells that house the plant and equipment used for reprocessing spent nuclear fuel. This gaseous waste is largely air contaminated with small entrained liquid or solid particles containing radioactive components. Some ventilation streams also are contaminated with oxides of nitrogen. 

Crossflow filtration separates the decontaminated waste solution from the MST solids containing the sorbed radioactive components. Stainless steel filter elements planned for use feature nominal 0.1 or 0.5-micron pore sizes. This filtration also captures any entrained undissolved solids associated with the salt solution retrieved from the high-level waste storage tanks. 

Solid waste products from the milling operation are tailings. They comprise most of the original ore and contain most of the radioactivity in it. In particular, they contain all the radium present in the original ore. At an underground mine they may be first cycloned to separate the coarse fraction which is used for undergroimd fill. The balance is pumped as a slurry to a tailings dam, which may be a worked-out pit. 

Chemical waste collected from the laboratory and other relatively small volume sources. This could be a mixture of hazardous and radioactive wastes, or other radioactive wastes with high dissolved solids content. 

Radioactive wastes. These are also very low. (1) solid waste, essentially parts of fuel subassembly frames after dismantling, (2) liquid waste coming from subassembly pump and IHX cleaning (these are not released directly from the plant but are transported to and treated at the COGEMA MARCOULE Center nearby), and (3) gaseous waste which follows the activity released from cladding failures, and so is very low. Most of the time, the activity is at background level. 

The PFR fuel reprocessing plant proved the technical feasibility of oxide fuel reprocessing via a Purex-cycle, with recovery of over 99.5% of the plutonium. This high recovery was also reflected in the low amounts of plutonium in the liquid and solid waste streams from the plant. The amount of radioactivity discharged to the environment was always about an order of magnitude less than the licensed limits. The plant is subject to IAEA and Euratom safeguards. 

Solid radioactive waste results from the operation and maintenance of the nuclear power plant and its associated processing systems for gaseous and liquid radioactive waste. The nature of such waste varies considerably from plant to plant, as do the associated levels of activity. Sohd radioactive waste may consist of spent ion exchange resins (both bead and powder) cartridge filters and pre-coat filter cake particulate filters from ventilation systems charcoal beds tools contaminated metal scrap core components debris from fuel assemblies or in-reactor components and contaminated rags, clothing, paper and plastic. 

This section should provide relevant information on the radioactive waste treatment systems as described in paras 3.65-3.70. It should include the design features of the plant that safely control, collect, handle, process, store and dispose of solid, liquid and gaseous forms of radioactive waste arising from all activities on the site throughout the lifetime of the plant. This should include the structures, systems and components provided for these purposes and also the instrumentation incorporated to monitor for possible leaks or escapes of radioactive waste. The potential for radioactive waste to be adsorbed and/or absorbed should be considered in deciding on the measures necessary to deal with this hazard. Further discussion on matters to be covered in this section of the SAR is provided in Ref. [32]. 

A new class of solvents called ionic liquids has been developed to meet this need. A typical ionic liquid has a relatively small anion, such as BF4, and a relatively large, organic cation, such as l-butyl-3-methylimidazolium (16). Because the cation has a large nonpolar region and is often asymmetrical, the compound does not crystallize easily and so is liquid at room temperature. However, the attractions between the ions reduces the vapor pressure to about the same as that of an ionic solid, thereby reducing air pollution. Because different cations and anions can be used, solvents can be designed for specific uses. For example, one formulation can dissolve the rubber in old tires so that it can be recycled. Other solvents can be used to extract radioactive waste from groundwater. 

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