High level waste

The previous section mainly considered the considerable impacts of dual regulation of mixed waste on management and disposal of mixed low-level waste. High-level waste, transuranic waste, and uranium or thorium mill tailings also may be subject to dual regulation under AEA (1954) and RCRA (1976). This Section briefly considers the impacts of dual regulation on these wastes. 

Aqueous wastes. High-level aqueous wastes HAW (stream 5) and lAW (stream 59) are concentrated by evaporation. The condensate, containing recovered nitric acid, is recycled. Processes for converting the concentrated, unneutralized liquid wastes to solid suitable for long-term storage have not been finalized. 

Racemization amino acids metal complexes, 467 Radioactive waste high level disposal, 895 Radiochemical purity technetium-99 in medicine, 976 Radionuclides... 

Highly Active Liquor high-efficiency particulate air filter high(ly) enriched uranium High Enriched Waste Concentrates High-level liquid waste high-level waste heavy metals... 

Waste Disposal Transuranic Waste, High-Level Waste and Spent Nuclear Fuel, and Low-Level Radioactive Waste... 

All wastes Low level waste High level waste... 

Radioactive Waste "high-level radioactive waste" 4... 

By-Products. The PUREX process is efficient at separating uranium and plutonium from everything else in the spent fuel. Within the high level waste stream are a number of components which have, from time to time, been sufficiendy interesting to warrant their recovery. The decision to recover a particular isotope is usually based on a combination of market incentives and desired waste reduction. 

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. 

The disposal of radioactive waste is governed by rules of the NRC and the EPA (19). NRC regulations differ for low level waste and for high level waste, including spent fuel (20). 

The geologic aspects of waste disposal (24—26), proceedings of an annual conference on high level waste management (27), and one from an annual conference on all types of radioactive waste (28) are available. An alternative to burial is to store the spent fuel against a long-term future energy demand. Uranium and plutonium contained in the fuel would be readily extracted as needed. 

Fig. 6. The nuclear fuel cycle. HLW = high level waste.

The primary issue is to prevent groundwater from becoming radioactively contaminated. Thus, the property of concern of the long-lived radioactive species is their solubility in water. The long-lived actinides such as plutonium are metallic and insoluble even if water were to penetrate into the repository. Certain fission-product isotopes such as iodine-129 and technicium-99 are soluble, however, and therefore represent the principal although very low level hazard. Studies of Yucca Mountain, Nevada, tentatively chosen as the site for the spent fuel and high level waste repository, are underway (44). 

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. 

New areas in adsorption technology include carbonaceous and polymeric resins (3). Based on synthetic organic polymer materials, these resins may find special uses where compound selectivity is important, low effluent concentrations are required, carbon regeneration is impractical, or the waste to be treated contains high levels of inorganic dissolved soHds. 

Another technique for organics measurement that overcomes the long period required for the BOD test is the use of continuous respirometry. Here the waste (full-strength rather than diluted as in the standard BOD test) is contacted with biomass in an apparatus that continuously measures the dissolved oxygen consumption. This test determines the ultimate BOD in a few hours if a high level of biomass is used. The test can also yield information on toxicity, the need to... 

While many industrial wastes are so low in nitrogen and phosphorus that these must be added if biologically based treatment is to be used, others contain very high levels ofthese nutrients. For example, paint-production wastes are high in nitrogen, and detergent production wastes are high in phosphorus. Treatment for removal of these nutrients is required in areas where eutrophication is a problem. 

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