Nuclear and Chemical Waste Management最新文献

The feasibility of RIM-NUT, a new physico-chemical process for removing and recovering phosphorus and ammonia from wastewater, has been demonstrated by treating the secondary effluent at West Bari (Italy) and South Lyon (Michigan/USA) municipal plants. High (69 mg NH₄/L; 12.5 mg PO,-P/L) and low (9.4 mg NHL; 1.3 mg PO₄ P/L) wastewater nutrients concentration characterized the first and the second demonstration, respectively. This paper summarizes the favorable results obtained during both demonstrations.

A set of statistical tests is proposed to evaluate the homogeneity of radioactive waste forms. These criteria were applied to cemented wastes forms by using natural thorium and uranium compounds as tracers simulating insoluble and soluble wastes, to evaluate the chemical homogeneity of the final product. The concentration of tracers in the samples were measured by using the delayed neutron counting technique which allows for the determination of uranium and thorium simultaneously. The same set of statistical tests can be applied to evaluate the homogeneity of all chemical and physical quantities necessary to characterize the waste forms (e.g., compressive strength, density, permeability, porosity, leaching rate, thermal conductivity, etc.). the possible influence of the water to cement ratio, (WIC), and salt contents in the waste stream was also investigated. The mixing technique used to produce the cemented waste forms proved to be good enough as a standard method to obtain a homogeneous product.

The overall goal of this research is to develop an understanding of the fundamental transport phenomena associated with the evolution of hazardous constituents from several types of solid materials, in particular, soils. At the present time, incineration is a relatively costly alternative for the cleanup of contaminated soils. An understanding of the mass transfer and heat transfer limitations might lead to a more economical option, where the contaminants and other constituents are desorbed from the soil at lower temperatures in a primary combustor and then a secondary,high temperature combustor (afterburner) decomposes the potentially hazardous off-gases. This work is aimed at providing fundamental rate information which will be used to model thermal desorption of chemical constituents from soils under a Variety of thermal conditions, soil properties, and contaminants.

The experimental approach is threefold. First, a bench-scale particle-characterization reactor (PCR) has been developed and is being used to characterize intraparticle transport under conditions where the bulk concentration and temperature at the particle surface are known. Following these studies, a packed-bed reactor will be used to examine interparticle transport within a well-characterized bed of particles. In the third portion of the work a 73 kW pilot-scale rotary kiln will be used to obtain time resolved measurements of trace species evolution. This paper reports recent PCR results which indicate that soil properties, type of contaminant, and temperature are important in the desorption of contaminants from soil particles.

In April 1985, the U.S. Environmental Protection Agency presented a new method for characterizing wastes, the Toxicity Characteristic Leaching Procedure (TCLP). This method will replace the Extraction Procedure Toxicity Test (EPTC) for determining the toxicity characterisitc of wastes under the Resource Conservation and Recovery Act (RCRA). This study examined 41 electric utility wastes produced by conventional and advanced sulfur dioxide control technologies to obtain information on the performance characteristics of coal combustion wastes tinder TCLP test conditions and to compare the performance of these wastes under both the EPTC and TCLP. The study addressed three aspects of the new test: (a) the effect of increasing the filter pore size from 0.45 microns in the EPTC to 0.7 microns in the TCIP: (h) the effect of changing the chemical nature of the leach medium on the measured values of the inorganic analytes in the leachates; and (c) the levels of organic compounds found in TCLP leachates of the coal combustion residues. The data suggest that filter pore size does not affect leachate composition. As a result, this change should not affect the analysis of conventional coal combustion wastes. An element-by-element comparison indicated that the TCLP is more aggressive than the EPTC towards leaching silver, arsenic, and chromium from the wastes tested, while the EPTC is more aggressive towards barium. The level of TCLP leachable organics associated with the coal combustion waste products was very low. mostly in the low parts-per-billion range.