High-level radioactive wastes

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

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

Intermediary-level waste is, as the name suggests, waste that contains more radioactivity than low-level waste and less radioactivity than high-level waste. It is often obtained from nuclear processes in which both low- and high-level wastes are mixed before collection and disposal. 

Leach behavior of borosilicate glass containing actual radioactive SRP high-level waste is similar to glass containing nonradio<-active simulated waste. 

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

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. 

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. 

Applicability Most hazardous waste slurried in water can be mixed directly with cement, and the suspended solids will be incorporated into the rigid matrices of the hardened concrete. This process is especially effective for waste with high levels of toxic metals since at the pH of the cement mixture, most multivalent cations are converted into insoluble hydroxides or carbonates. Metal ions also may be incorporated into the crystalline structure of the cement minerals that form. Materials in the waste (such as sulfides, asbestos, latex and solid plastic wastes) may actually increase the strength and stability of the waste concrete. It is also effective for high-volume, low-toxic, radioactive wastes. 

Nuclear reactors, however, do generate highly radioactive waste. This waste, which consists primarily of the fission fragments and their radioactive-decay products, must be stored for many years before its radioactivity decays to a reasonable level, and the safe long-term storage of this waste is a matter of great concern and debate. Fortunately, the volume of waste that is created is only about 20 cubic meters annually from a reactor, compared with 200,000 cubic meters of waste ash from a coal-fired plant. When nuclear weapions were tested in the atmosphere, the radioactive products from the nuclear explosions were released into the air and fell to Earth as radioactive fallout. 

The main drawback to nuclear power is the production of radioactive waste. Spent fuel from a nuclear reactor is considered a high-level radioactive waste, and remains radioactive for a veiy long time. Spent fuel consists of fission products from the U-235 and Pu-239 fission process, and also from unspent U-238, Pu-240, and other heavy metals produced during the fuel cycle. That is why special programs exist for the handling and disposal of nuclear waste. 

American Nuclear Society, (annual). High Level Radioactive Waste Management Proceedings for the International Topical Meeting of the American Nuclear Society and the American Society of Cavil Engineers. Chicago American Nuclear Society. 

DOE. 1999. Inventory and characteristics of spent nuclear fuel high level radioactive waste and other... 

The Clinton Administration believes that the overriding goal of the Federal Government s high-level radioactive waste management policy should be the establishment of a permanent geologic repository - essential not only for the disposal of commercial spent fuel, but also for... 

EPA, 1985, 40 CFR Part 191, Environmental Standards for the Management and Disposal of Spent Nuclear Fuel, High-Level and Transuranic Radioactive Wastes Final Rule, Federal Register 50, no. 182 38066. 

Fig. 1. Decay of high level nuclear wastes from spent fuel as a function of storage time. Radioactivity in curies per ton of spent fuel (PWR, 3.3% enriched 2 5U, burnup 33,000 MWD/MTU at 30 MW/MTU, 5 year cooling, 99.5% U, Pu recovered)...

Radioactive wastes are usually stored in underground tanks or in temporary storage at reactor sites for recycling or disposal (Whicker and Schultz 1982a). For low-level wastes, containment and isolation are the preferred disposal options, including burial, hydraulic injection into deep geological strata, and ocean disposal (Table 32.10). Options for the disposal of high-level wastes include... 

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