Waste, radioactive disposal

The off-gas treatment involves primarily iodine, krypton, and xenon. There are a variety of processes for capturing the iodine and disposing of it. Kr and Xe are captured by either cryogenic techniques or selective absorption, such as absorption in chlorofluoromethane. Most of the off-gas volume is due to Xe ( 800 L/Mg fuel) with the activity being mostly 10.7-y 85Kr ( 11,000 Ci/Mg fuel). 

The dissolver solution is treated with chemicals to adjust the acidity, valence, and concentrations of the species involved. The HNO3 concentrations are 2-3 M, the U02(N03)2 concentrations are 1 -2 M, and the Pu is stabilized as Pu(IV) using N2O4 or hydroxylamine. In these and subsequent manipulations of these solutions, attention must be given to criticality control. This is done by regulating the solution geometry, the concentrations of fissile materials, and by the addition of neutron absorbers such as Gd. 

The primary separation of plutonium and uranium from the fission products involves a solvent extraction with 30 vol % TBP at room temperature. The activity levels in this separation are quite high ( 1700 Ci/L for the fission products) and the aqueous waste, which contains 99+% of the fission products, is a high-level waste. Am and Cm are not extracted and Np is partially extracted. Because of the high radiation levels, there are radiolysis problems with TPB, leading to solvent degradation. Primary products of the radiolysis of TBP are the dibutyl- and monobutylphosphoric acids along with phosphoric acid. These degradation products are removed in the solvent purification steps. 

Following decontamination of the uranium/plutonium from the fission products, the plutonium is separated from the uranium. This is done by reducing the Pu(IV) to nonextractable Pu(III), leaving uranium in the hexavalent state. In the older Purex plants, this was done using Fe2+ while the newer plants add U4+. The plutonium thus ends up in an aqueous phase while the uranium remains in the organic phase. 

Uranium is back-extracted (and thus removed from the organic phase) with 0.01 M HNO3. It is purified by a series of solvent extraction cycles until the Pu/U ratio is 10-8 and the total (3y activity is less than twice that of aged natural uranium. 

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K. B. Krauskopf, Radioactive Waste Disposal and Geology, Chapman and Had, London and New York, 1988. 

Directions in Eow-Eevel Radioactive Waste Management A Brief History of Commercial Eow-Eevel Radioactive Waste Disposal, DOE/LLW-103, Rev. 1, The National Low-Level Waste Management Program, INEL, Idaho Eads, Idaho, Aug. 1994. 

M. R. English, Siting Eow-Eevel Radioactive Waste Disposal Facilities The Public Poliy Dilemma, Quomm Books, New York, 1992. 

Technology Descriptions The use of thermoplastic solidification systems in radioactive waste disposal has led to the development of waste containment systems that can be adapted to industrial waste. In processing radioactive waste with bitumen or other thermoplastic material (such as paraffin or polyethylene), the waste is dried, heated and dispersed through a heated, plastic matrix. The mixture is then cooled to solidify the mass. 

Arthur WJ, Janke DH. 1986. Radionuclide concentrations in wildlife occurring at a solid radioactive waste disposal area. Northwest Sci 60(3) 154-165. 

Arthur WJ, Markham OD, Groves CR, et al. 1987. Radionuclide export by deer mice at a solid radioactive waste disposal area in southeastern Idaho. Health Phys 52(l) 45-53. 

EPA. 2001d. Radioactive waste disposal An environmental perspective. Low-level radioactive waste. U.S. Environmental Protection Agency, http //www.epa.gov/radiation/radwaste/llw.htm. March 13, 2001. 

Janke DH, Arthur WJ. 1985. Radionuclide transport by cottontail rabbits at a radioactive waste disposal area. Northwest Sci 59(3) 221-229. 

Organophosphate ester hydraulic fluid components have also been detected in groundwater near a hazardous waste site (1.7 pg/L tributyl phosphate) (Sawhney 1989) and in surface water from a radioactive waste disposal site (triphenyl phosphate and tributyl phosphate) (Francis et al. 1980). Organophosphate... 

Francis AJ, Iden CR, Nine BJ, et al. 1980. Characterization of organics in leachates from low-level radioactive waste disposal sites. Nuclear Technol 50 158-163. 

Highway Maintenance Activities Storage areas and direct application Radioactive Waste Disposal... 

Table 1. Sedimentation Rates and Curve Fitting of 210Pb Measurements in Cores Collected at the U. S. Radioactive Waste Disposal Sites Near the Farallon Islands 60 km off San Francisco and at the Hudson Canyon, 350 km off New York City.

By combining the findings of Cacchione, Drake and the results reported here, a coherent model can be proposed to explain the deposition inventory of the radionuclides. The down-canyon current transports large quantities of sediment toward the radioactive waste disposal site at 4000 m. Within the upper canyon, fine material is transported the furthest. Near the mouth of the canyon, sediment erosion of the walls occurs due to the down-canyon currents meeting a proposed opposing on-shore bottom current. The eroded material from the walls is transported and the finer material is deposited in eddies formed where the two currents meet. 

Schell, W. R., and Sugai, S., Radionuclides at the U. S. Radioactive waste disposal site near the Farallon Islands, Health Physics, 39 475-496 (1980). 

Halford, D.K., O.D. Markham, and G.C. White. 1983. Biological elimination rates of radioisotopes by mallards contaminated at a liquid radioactive waste disposal area. Health Phys. 45 745-756. 

Hydrohalogenation, 10 597 Hydroiodic acid (HI), 14 360, 374. See also Hydrogen iodide Hydroisoquinolines, 21 205, 206 Hydrolases, 3 675-676 Hydrologic cycle, 26 2-3. See also Hydrogeochemical cycle(s) carbon circulation in, 26 27—30 chlorine circulation in, 26 31 nitrogen circulation in, 26 32 sulfur circulation in, 26 30-31 Hydrology, in radioactive waste disposal, 25 856, 857... 

Low-level radioactive waste (LLW), 25 851. See also Low level wastes (LLW) disposal of, 25 857-859 medical/biological, 25 865-866 storage of, 25 855 treatment of, 25 853 Low-level radioactive waste disposal facility, operation of, 25 858 Low-Level Radioactive Waste Policy Act of 1980, 25 852... 

The discrepancy in numbers between natural and synthetic varieties is an expression of the usefulness of zeolitic materials in industry, a reflection of their unique physicochemical properties. The crystal chemistry of these aluminosilicates provides selective absorbtion and exchange of a remarkably wide range of molecules. Some zeolites have been called molecular sieves. This property is exploited in the purification and separation of various chemicals, such as in obtaining gasoline from crude petroleum, pollution control, or radioactive waste disposal (Mumpton, 1978). The synthesis of zeolites with a particular crystal structure, and thus specific absorbtion characteristics, has become very competitive (Fox, 1985). Small, often barely detectable, changes in composition and structure are now covered by patents. A brief review of the crystal chemistry of this mineral group illustrates their potential and introduces those that occur as fibers. 

Radioactive Waste Disposal. There are two principal types of radioactive materials produced in the operation of nuclear generating stations. Over 99% of the radioactivity produced is... 

A detailed discussion of the chemical aspects of this radioactive waste disposal program is given by Tomlinson at this S3nn-posium (20). 

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