Study of thermo-stimulated luminescence of an α irradiated natural glass has revealed the formation of a structural defect that cannot be annealed thermally and is therefore cumulative. This phenomenon was again encountered and analysed in synthetic borosilicate glass to be used as radionuclear waste glass. To detect this structural modification, the thermoluminescence signal of an α irradiated sample is traced under certain conditions. Two peak characteristics of a previous α irradiation appear at 230 °C and 320 °C. Their intensity increases at each new experiment, although the α irradiation dose administered remains constant. In other words, despite the successive thermal emptyings, the glass keeps the trace of previous irradiations and consequently gives an increasing signal for constant doses.
Fatigue-crack propagation tests were conducted on a candidate container material (ASTM A27 steel) tested in Hanford groundwater at 150°C for application in a potential basalt repository. Tests were run at a single value of stress intensity factor on groups of identical specimens undergoing gamma irradiation and control specimens not exposed to irradiation. The gamma flux levels (approx. 123 rad/hour) were prototypic of the maximum levels expected at the outer surface of the waste container. A statistical evaluation suggested that there were no significant differences between crack growth rates in the unirradiated and irradiated specimens.
Field chemical analyses were applied to an investigation of the Rockaway Borough well field, located in northwestern New Jersey, USA, and the designated sole-source glacial aquifer supplying the well field. The aquifer and the Borough water supply were found to be contaminated with up to 680 μg/L of tetrachlorethylene (PCE) and 172 μ/L of trichlorethylene (TCE) in 1980. The sources of the contaminants had not been identified in 1982 when the well field was placed on the United States Environmental Protection Agency National Priorities List of uncontrolled hazardous waste sites. A limited site investigation was conducted using on-site chemical analyses of groundwater samples and soil sample headspace gases. The investigation identified optimal monitoring well locations, provided cost-effective time series sampling data, and identified the locations of three potential contaminant sources.
The volatility of cesium from a calcined mixture of oxides containing 1% cesium as the chloride and 1 μCi of cesium-137 tracer follows a logarithmic relationship with temperature from 0.067 ± 0.002% volatilized per hour at 400°C to 22.67 ± 0.09% per hour at 900°C of that present. At the same rate, complete volatilization would occur in 1 hour at 1030°C, but only 0.0020% will be volatilized per hour at 100°C. After fusion has occurred, the volatility of cesium decreases markedly, probably because of the limited rate of diffusion through the viscous melt to the surface without stirring. The rate varied from about 0.059 ± 0.001% per hour at 1300 °C to 0.316 ± 0.002% per hour at 1500°C.
The natural distribution of water in the Avery Island domal salt has been investigated by performing trace water content analysis on 64 samples collected systematically at the 210 and 270 meter levels of the International Salt Compan mine. Specific attention was given to salt near an internal shear zone which is the apparent source of several mine leaks. No discernible migration of brine into the adjacent salt was observed from the meteoric leak at the 210 m level. Extensive water enrichment (>1000 mg/kg) was limited to 30 meters from the formation water leak at the 270 m level. The water contents of coexisting samples near the formation water leak are highly variable. If water is moving from; this leak into the adjacent normal salt it is not doing so by way of a uniform diffusion process. Petrographic examination of polished salt samples reveals that fluid inclusions occur mainly in healed fractures. The water content of a sample depends on the density of such fractures. Natural movement of water in the salt appears to occur mainly through microfractures and possibly along crystal boundaries rather than by the diffusion of brine through crystals. One possible zone of enhanced water content may occur along a possible bedding plane which intersects a mine leak. This suggests that any natural movement of fluid not associated with fractured salt may occur preferentially along bedding planes. The method of brine migration under natural conditions, the occurrence of fluid inclusions (i.e., fracture vs. nonfracture-fill inclusions), and the water content of salt will be helpful in evaluating the migration of brine in response to the thermal and/or pressure gradient which will be created by the emplacement of radioactive waste.
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.
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.
Nutrients can be removed from wastewater by either destruction or recovery. Ion exchange methods have been utilized by others for recovery of ammonia, nitrates, and phosphates. Urea hydrolysis requires elevated temperature and pressure along with energy inputs. However, these experiment data have shown that urea can be removed by hydrolysis utilizing the urease enzyme. The reported study covers results on hydrolysis and removal of urea wastewaters from a nitrogen fertilizer plant after concentrating the ammonia to about 11% on a weakly acidic cation exchanger then recovering the ammonium nitrate for reuse.
A coupled geochemical/geohydraulic model is used to discuss and interpret possible mechanisms for contaminant transport and accumulation in inorganic environments. The geochemical part of the code, the triple layer model for adsorption, allows one to estimate the variation of the contaminant distribution coefficient with solution composition. The hydraulic part of the model establishes a deterministic correlation of the spatial variation of the distribution coefficient. Scenarios are constructed incorporating computed system behavior. A comparison of potential contaminant concentrations with acceptable ones allows one to quantify the degree of geochemical isolation of the contaminant which a chosen environment provides. Long lived waste, activated in the thermal neutron flux of a light water reactor, is classified using the proposed methodology and a very conservative scenario: beryllium, lead, molybdenum, selenium, tin and zirconium activated in the bulk of the reactor decommissioning waste (the bioshield) might be sufficiently isolated by the chemistry in common soils. The concentration of nickel in oxidizing inorganic noncomplexing drinking water has an upper limit given by the precipitation of nickel minerals. Above pH = 7 is an effective geochemical barrier for nickel activated anywhere in the reactor, except the high neutron flux region.
The cation exchange properties of a Hungarian clinoptilolite containing rock from the Tokaj mountains have been studied. The aim of the work has been to prepare suitable cation containing forms for NH4+-removal and regeneration of the NH4+-form. The process has been followed from the start with static laboratory experiments through laboratory dynamic measurements up to pilot plant. The static CEC of the clinoptilolite containing rock proved to be 1.2 meq/g. However, under dynamic conditions this value is only 0.2–0.3 depending on the circumstances, thus this material is capable of the elimination of 3–5 mg NH, per g rock. The exhausted clinoptilolite can be regenerated more efficiently by potassium ions than by the usually applied sodium ions.
Complexation of metal ions with water-soluble polymeric ligands and retention of the macromolecular complex by ultrafiltration afford a method of preconcentration of metal ions in homogeneous phase. This technique has been evaluated from literature data in view of its application to the treatment of metal containing wastes. Two procedures are applicable, namely diafiltration and concentration method. Both methods yield excellent metal retention with such readily available polymers as polyacrylic acid and polyethylenimine. Synergic effects on the metal retention were reported in some cases by addition of low molecular weight ligands. Furthermore, better selectivity can be obtained using watersoluble solymers bearing specific chelating functions. However, the chelating group capacity has to be limited in order to ensure the water solubility of the resulting complex. Efficiency of the process has been discussed in terms of retention of macromolecular solutes and of membrane fouling. Both ultrafiltration procedures have been compared considering perspectives of application. Besides, coupling of complexation-ultrafiltration with electrolysis offers an elegant method of metal recovering in a pure metallic form. This promising technique is in development for waste treatment from electroplating and appears as a relevant process for treatment of wastes from nuclear plants.
Eight hazardous waste land disposal units at the Oak Ridge Y-12 Plant are being closed in accordance with the Resource Conservation and Recovery Act (RCRA) under an integrated multi-year program. The units, some of which date back to the early 1950s and include five surface impoundments, two landfills and a land treatment unit, have been used for the management of a variety of types of hazardous wastes. Closure plans for the units have been submitted and are in various stages of revision and regulatory review. The units will be closed by various combinations of methods, including liquid removal and treatment, sludge stabilization, contaminated sludge and/or soil removal, and capping. Closure of all eight units must be initiated by November 8, 1988.
An extensive well installation program of approximately 600 wells in the ORNL area was initiated in December, 1985. At that time it was recognized that subcontractor personnel involved in the Laboratory's characterization effort might encounter radioactive or other hazardous materials that could result in significant levels of exposure. A program was established to provide for categorization of health hazard protection for those individuals involved in the characterization effort. This paper will address the steps that were taken to evaluate proposed sites for subcontractor activity, assumptions used to categorize the level of health risk, and the procedures established for assignment of appropriate protective equipment.
Enzymes offer inherent advantages and limitations as active components of formulations used to decontaminate soil and equipment contaminated with toxic materials such as pesticides. Because of the catalytic nature of enzymes, each molecule of enzyme has the potential to destroy countless molecules of a contaminating toxic compound. This degradation takes place under mild environmental conditions of pH, temperature, pressure, and solvent. The basic limitation of enzymes is their degree of stability during storage and application conditions. Stabilizing methods such as the use of additives, covalent crosslinking, covalent attachment, gel entrapment, and microencapsulation have been directed toward developing an enzyme preparation that is stable under extremes of pH, temperature, and exposure to organic solvents. Initial studies were conducted using the model enzymes subtilisin and horseradish peroxidase.
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.
Engineered barriers can slow the movement of pollutants out of land disposal facilities in several ways. If the advective velocity is low, release will be primarily by molecular diffusion. Attenuation processes also work to slow the transport of many contaminants. Barriers that cause pollutants to be released almost entirely by molecular diffusion represent the best barriers achievable. Use of thick barrier materials will maximize the breakthrough time of contaminants that diffuse through the barrier. Thin barriers with exceedingly low permeabilities will not necessarily outperform thicker, more permeable liners. In fact, if diffusion is the dominant mechanism of release, the thicker, more permeable barrier may actually outperform the thinner barrier with lower permeability.
Leaching of chromium in solidified cement indicates that the release of chromium(III) corresponds to the solubility of the hydrolized compounds Cr(OH)3 which presents a low constant value (10−6 Moles L−1 over a wide pH range. On the other hand, high soluble Cr(VI) presents in the first period of leaching a kinetic release similar to that previously observed for calcium. In addition, physical tests have been carried out on cement blending variable amounts of chromium compounds. The results concerning the compressive strength, densities, and porosity of cement containing CrCl3, Cr2O3 and Cr03 are reported and discussed.
This study was conducted to evaluate the utility of short-term microbial bioassays to assess the mutagenic hazard of an uncontrolled hazardous waste site, and to compare the results from chemical and biological analysis of split soil and water samples. The results from chemical analysis indicated that the greatest concentration of contaminants was present in samples from an oil-stained area, and from the vicinity of a PCB disposal area. The results from the analyses of mutagenicity of these samples indicates that these samples also had the greatest specific activity, inducing 155 and 140 net revertants when the methylene chloride and methanol fractions were assayed, respectively. However, when the samples are compared on the basis of weighted activity, the sample from the vicinity of the PCB disposal area had the maximum activity (2410 revertants per gram of soil). While a second sample from the vicinity of the PCB disposal area had a weighted activity of 757 revertants per gram of soil, it contained no organic constituents which could be identified using standard analytical procedures. These results indicate that a combined testing protocol using both chemical and biological analysis will provide a more accurate data base from which to make a risk assessment than the use of either method alone.
