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  • 1
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. An investigation into the fate of elements during residential composting was conducted by studying an Envirocycle residential-type aerobic composter unit that was set up and operated at the University of Toronto's greenhouse facility. Source materials consisting of various fruits and vegetables were combined with Metropolitan Toronto Works Department's finished leaf compost (MWFLC), and composted over a 2-month period. Instrumental neutron activation analysis (INAA) was used to determine the concentrations of Al, As, Ba, Ca, Co, Cr, Fe, K, Mg, Mn, Na, Sb, Sr, Ti, V, and Zn in the source materials and the 2-month greenhouse finished compost (GHFC). Results indicate that the ratio of final element mass to input element mass was approximately 1, suggesting that elements are conserved during the composting process. One tailed t tests (0.05 level of significance) on element concentrations between the MWFLC and GHFC revealed that supplementing MWFLC with fruits and vegetables does not significantly change concentrations 〉25%. One-way analyses of variances conducted on Toronto residential compost samples revealed good homogeneity within an individual composter, although significant elemental variances occurred between separate composters. Incidentally, it was noticed that several of the Toronto residential compost samples had Cr levels that exceeded Ontario Ministry of Environment and Energy guideline values for municipal compost.
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  • 2
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Radiochemical methods are quite suitable for studying the behaviour of radioiodine under the dilute conditions relevant to nuclear reactor accidents. Species selective adsorbents are able to distinguish between various inorganic and organic gas-phase iodine species. A solvent extraction procedure for determining aqueous phase organic iodide, free iodine, I− and IO 3 − fractions has been investigated and found to be valuable, although large inaccuracies in the separation of I− and IO 3 − can occur for solutions of pH above 10. The extraction of potentially-volatile species in the aqueous phase gives a measure of iodine species volatility consistent with observed values of the partition coefficient. Indirect measurement suggest that the partition coefficient of HOI at room temperature exceeds 30,000.
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  • 3
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract An understanding of radioiodine volatility is important in relation to nuclear reactor safety. In this paper, findings of an ongoing experimental assessment of radioiodine partitioning are described. Radiochemical methods of determining liquid and gas phase speciation are presented along with experimental results demonstrating the validity of these methods. These results also indicate that the majority of the gaseous organic iodides detected at TMI-2 following the accident were in a low molecular weight form such as methyl iodide. It is concluded that, for 10−4 M CsI solutions, the partition coefficient increases by an order of magnitude with increasing pH and, the aqueous and gaseous concentrations of both molecular iodine and organic iodide decrease with increasing pH over the pH range of 4 to 12.
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  • 4
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The behaviour of iodine in the environment is of interest both in relation to radioecology and human nutrition. Radiochemical techniques were used to evaluate various aspects of the behaviour of iodine in the environment. The natural iodine content of plant, water and soil samples collected from three sites was determined using preconcentration neutron activation analysis (PNAA). The effect of initial chemical speciation on the distribution of iodine between various soils, sediments and waters was evaluated using I-131 tracer. Iodide was found to adsorb more extensively than iodate, although for most of the solid/water systems examined, a substantial portion of the iodate was slowly reduced to iodide. Experiments involving gamma irradiation suggest that much of the sorption of iodide and reduction of iodate involved microbial processes. Distribution coefficients measured using I-131 were comparable with values based on the natural I-127 content.
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  • 5
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The effect of organic compounds on the production of volatile species of iodine was examined. The first step has been to identify candidates for detailed study through a series of scoping experiments, in which the chemical environment existing in CANDU reactor containment is simulated. These experiments have involved the irradiation of 10−5M CsI solutions labelled with131I containing a dilute concentration of a particular organic compound (8.5·10−3 to 1.4·10−1M). A total of 20 compounds and polymers have been tested to date. Results have shown that many of these compounds do enhance iodine volatility, and that the degree of volatility is related to system pH. Using the iodine partition coefficient (H=iodine concentration in the liquid phase/iodine concentration in the gas phase) as a basis, values as low as 300 have been observed for chloroform solutions. Conversely some compounds, such as phenol, have produced low volatility, with values of 1·105. As a reference, a partition coefficient of 104 has often been used in safety analysis.
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  • 6
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The environmental impact of many postulated CANDU (Canada Deuterium Uranium) reactor accidents depends on the behaviour of iodine isotopes. In recent years a substantial portion of Canadian iodine research has focused on experiments conducted in the intermediatescale Radioiodine Test Facility (RFT) at Whiteshell Laboratories. Because of the very low concentrations relevant to reactor accidents, much of the analysis of iodine behaviour has required the high sensitivity of a radiochemical methodology. Very low gas-phase iodine concentrations (〈10−10 mol/dm3) are routinely determined, up to several times an hour, using an automated airborne iodine sampler whereas various chemical forms are distinguished using selective adsorbents. Useful information regarding the chemical speciation of iodine in the aqueous phase is obtained using solvent extraction. This paper describes the radiochemical techniques used in RTF experiments, with examples of the results thereby obtained.
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  • 7
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract In the light of the remarkable strides in radioactivation analysis methods and techniques that haved been achieved progressively in the 34 years since Modem Trends conferences began, some speculations on the future directions that the field might take in the foresceable future seem appropriate at MTAA-9. Together with improvements that will likely occur in instrumentation, in prompt and ion-beam methods, there would seem to be yet a further potential for extending the range of information that radioanalytical techniques can provide by complementing RAA measurements on samples with an increased use of manipulative chemistry. Among complementary chemical methods are not only pre-activation chemistry for speciation studies and matrix removal but also, radiotracer/INAA combinations, isotopic exchange/INAA (as illustrated in this paper through recent studies on the behavior in the environment of solid waste residues), substoichiometric-RAA and classical radiochemical, post-activation separations for specific element(s). Results are presented on the toxic element content of solid waste ashes by INAA and on their uptake of65Zn and109Cd in which there is evidence of two interaction processes between waste particles and simulated groundwater: a rapid exchange (within a few minutes) and slow exchange extending over days. This tends to confirm results on leachability of toxic elements from solid wastes but serves to distinguish adsorption processes from isotopic exchange.
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  • 8
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract As part of a larger occupational exposure study in which the concentrations of 18 elements were measured in head hair and toenail collected from steel plant workers, a number of factors associated with interpreting the data obtained were examined. In this paper, some of the limitations and complications associated with hair and nail analysis that were thereby recognised are discussed. Data obtained from the occupational study demonstrated the potential for misinterpreting hair or nail analysis data either through describing results averaged over a group by arithmetic instead of geometric means or through not accounting for the age range of subjects in groups to be compared. Examples that arose from the study indicated that differences between hair from the same subjects grown at different times can both complicate and assist in interpreting hair analysis results. In an investigation into the addition and removal of metallic powders, it was found that both hair and nail can directly incorporate elements through contact with dust.
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  • 9
    ISSN: 0392-6737
    Keywords: Infra-red and Raman spectra and scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si mostra come l'inerente non linearità delle equazioni di moto di dipoli accoppiati spiega qualitativamente un numero di comportamenti dello spettro osservato nel lontano infrarosso di fluidi polari. Questi includono il decremento quasi lineare della posizione del picco del coefficiente di assorbimento di potenza FIR con l'aumento della temperatura e l'indipendenza della temperatura dell'ampiezza di banda.
    Notes: Summary It is shown how the inherent nonlinearity of the equations of motion of coupled dipoles qualitatively explains a number of features of the observed far-infra-red spectrum of polar fluids. These include the almost linear increasing temperature and the temperature independence of the band width.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 88 (1996), S. 83-92 
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Uranium tailings are generated as solid and liquid wastes in uranium mining/milling operations. Since most of the uranium deposits in the world have low grades, millions of tonnes of such wastes are produced annually. Often, the uranium tailings are locally disposed of, using sites with suitable conditions to construct tailings basins. The main concern during the operation of a disposal site is the presence of radium in the liquid phase which overflows from dewatered tailings. This barium is precipitated by adding proper chemical reagent. The potential environmental hazards of uranium tailings arise when the disposal site is abandoned after the decommissioning of the uranium mill. Huge amounts of solid waste as small particles of depleted ore remain in place. Top soils are usually for soil stabilization and for controlling radon emissions. Hence water infiltration through uranium tailings presents a potential hazard to underground aquifers. Water plays a dual role by triggering a sequence of reactions and by carrying contaminants away from the wastes sites. The situation is more serious in a country like Canada, where the precipitation rate is higher than the evaporation rate and the water table is about one metre beneath the ground surface. For permanent disposal of uranium tailings, either the hazardous constituents of these wastes have to be isolated from the percolating water, or the subsoils must have acceptable sealing and sorptive characteristics. The first approach is effected by blending proper solidifying reagents with the tailings in order to totally block them from the leaching effects of aggressive pore water. Solid waste treatment may prove costly in additive usage and the blending operation. The leaching of toxic constituents, however, becomes effective so long as the tailings are in a loose form. This is because of the acid-generating properties of the pyrite, a substantial constituent (up to 8% wt) of the tailings. Two types of contaminants tend to leave the solid and migrate to the pore water. These are the heavy metals and the radioactive elements, both of which are hazardous for their toxicity and persistence. The sorptive and neutralizing capacities of the underlying soils have to be carefully examined and measures have to be taken to stop the progression of acidic interstitial water. This paper focuses on three aspects of crucial importance to the permanent disposal of uranium tailings. These are: leaching in uranium tailings, sorption on natural geological barriers, and radium immobilization.
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