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Abstract  

Information about the sorption of radionuclides on natural materials used for cementation of liquid radioactive wastes (RAW) is important for predictions of migration rates of radionuclides in the products of fixation. Cementation process for conditioning liquid RAW uses, besides cement, materials which improve quality of products. In Czechoslovakia technology among these materials are clinoptilolite tuffit, mordenite tuff, tobermorite and fly ash. Liquid RAW issued from nuclear power plants contains the principal radionuclides60Co,134Cs and137Cs, therefore, a sorption study of these radionuclides was carried out. pH of liquid RAW was 12.5–13.7 and salt content ca. 200 g·dm–3. Results of sorption are given by distribution coefficients. The best results for cesium in those pH region and salt content had mordenite tuff DCs=100 dm3·kg–1 and the worst results had fly ash DCs=4.1 dm3·kg–1. The best results for cobalt in those solutions had tobermorite DCo=38 dm3·kg–1 and the worst results had fly ash DCo=6.9 dm3·kg–1.

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cement with different fine-grained additives such as waste materials (e.g. silica fume [ 1 , 2 ], fly ash [ 1 – 3 ], slag [ 4 ], spent aluminosilicate [ 5 ]) as well as other types of cements (e.g. Portland cement [ 6 , 7 ]) have been undertaken. In

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Abstract  

Fired-clay products such as bricks, tiles and pavers, are made in large volumes for use in a variety of construction applications throughout the world. A significant proportion of them ends up being a waste product either during their production process or the demolition of buildings. High pressure steam curing or autoclaving has proven extremely versatile for the manufacture of cement-based building products incorporating waste materials such as fly-ash and blast furnace slag. The nature of hydration products in an autoclaved cement based system incorporating different amounts of finely ground brick waste was investigated by means of thermal analysis and XRD, and is the subject of this paper.

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Abstract  

The effect of neutron irradiation on the leachability of elements in solid wastes comprising of coal fly ash, hospital and municipal incinerator ashes was studied. There was a marked increase in leachability in the neutron irradiated wastes compared to non-irradiated wastes especially for elements such as As, Cd, Co, Cr, Sm and Zn. For elements such as Fe and Sm there was no significant difference in the leachabilities in the irradiated and non-irradiated wastes. The possible causes of this scenario and implications are discussed.

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Summary  

Modelingand experimental approaches to study reactive transport across chemical gradients in porous media are presented. Particular emphasis is placed on apurposeful experimental setup to obtain information necessary for model calibration and verification. As example, diffusion tube experiments on the layered acidic jarosite/alkaline coal fly ash system have been carried out using radiotracers 3H+, 22Na+, and 59Fe3+. Such radiotracer diffusion tube experiments provide modelers with reliable information incorporatingsome of the complexities observed in the environment such as local heterogeneities.

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Abstract  

Instrumental neutron activation analysis (INAA) was applied to assess element concentrations in eleven samples of mineral supplements/multivitamins acquired in drugstores and pharmacies in São Paulo city, SP, Brazil. Concentrations of Ca, Co, Cr, Cu, Fe, K, Na, Se and Zn were determined. A comparison was made between the results obtained with the labels of the mineral supplents. Certified reference materials, NIST SRM1400 Bone Ash and NIST SRM 1633b Coal Fly Ash were analyzed for quality control of the analytical results.

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Abstract  

A radiochemical procedure for simultaneous determination of lead (203Pb), thallium (202TI) and cadmium (115Cd 115mIn) after fast neutron activation, based on ion-exchange separation from bromide medium and additional purification steps for Pb and Tl is described. Radioactive tracers210Pb and109Cd were used for determination of the chemical yields of Pb and Cd; for Tl it was determined gravimetrically. Two standard reference materials, BCR CRM No. 146 Sewage Sludge and NIST SRM 1633a Coal Fly Ash were analyzed and satisfactory agreement with certified values was obtained.

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Abstract  

The Lawrence Livermore Laboratory program to evalute the trace elements in stack emissions from coal-fired power plants is described. Stack sampling and analysis of fly ash at modern, western U. S. power plants is discussed. Scanning-electron-microscope techniques are shown to be essential for accurate sizing of stack particles sampled with cascade impactors. Particle-size distributions for volatile and nonvolatile trace elements are reported. Comparisons show that the trace elemet enrichment factors of western and eastern U. S. coal-fired power plants are significantly different.

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Abstract  

The intense 14-MeV neutron facility at Lawrence Livermore National Laboratory was used for fast-neutron activation analysis (FNAA) of standard fly ash, orchard leaves, and bovine liver supplied by the U.S. National Bureau of Standards. The high flux of 14-MeV neutrons allowed concentration determinations of up to 20 elements from the set of Na, Mg, Al, Si, P, K, Sc, Ti, Fe, Co, Ni, Zn, As, Se, Rb, Sr, Y, Zr, Mo, Sb, Ba, Ce, Tl, and Pb. Interferences and steep flux-gradients were problems, but the elemental profile we obtained is the most complete analysis using FNAA to date.

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Abstract  

On irradiation with neutrons, some of the interesting trace elements in coal, coal ash and fly ash produce short-lived nuclides which may be determined—together with some of the matrix elements—by activation analysis. This enables the characterization of samples. To find out the distribution of elements in the gaseous or aerosol exhaust of fossil-fired power plants, we simulated the combustion in a quartz apparatus containing a cold trap, using the combustion temperature (780 °C) employed for the standard ash determination. High Se values were found in the cold trap deposits from black coal from Poland. Halogens were also found in the deposits.

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