An economic analysis of microbial reduction of sulfur dioxide as a means of byproduct recovery from regenerable processes for flue gas desulfurization

Applied Biochemistry and Biotechnology - In summary, it appears that the microbial reduction process is clearly not competitive with conventional SO2-reduction techniques when glucose (DE95 corn...     

High-Flux Irradiation of Open Samples

The irradiation of large samples of biological material in a high neutron flux enables the extention of trace element analysis into the ng to pg range, but raises several problems as gamma heating and radiolysis degrade the samples. Gamma heating increases the pressure to a point where either a very large irradiation container is necessary or a container which can endure the high pressure. Several methods to overcome these problems have been published. The irradiation of open samples was performed as an alternative to these methods. Temperature effects on biological material during irradiation in a high and in a low neutron flux were compared. As an example, wheat was irradiated in open containers allowing simultaneous temperature measurement in the sample during irradiation.     

Activation Analysis of Large Samples

The usual mass of samples for activation analysis is in the range of several milligrams to several hundred milligrams. An improvement of the detection limit by three orders of magnitude is attainable by use of a larger sample size. Limitations of the method due to thermal effects, neutron self-shielding and gamma-ray attenuation during activation and measuring of large organic samples are discussed.     

Fluorine analysis of standard materials by short-time activation analysis using20F

Phosphorus at trace levels alters the properties of metals and alloys. Its determination was investigated by radiochemical neutron activation analysis. Separation by solvent extraction or by evolution as P⁰ showed to be neither selective nor quantitative in presence of a metallic matrix. Therefore, a new method of separation by reduction to phosphorus hydride followed by liquid scintillation counting was investigated. This method is quantitative in the case of non-radioactive iron doped with radioactive phosphorus. At present, the separation is not quantitative for irradiated iron samples, owing probably to hot atom or radiation effects. A detection limit of 0.002 g is expected.Presented at the MTAA-8 Conference, September 16–20, 1991, Vienna, Austria.     

Instrumental neutron activation analysis of samples with volumes from 2 to 350 ml

Usually neutron activation analyses are performed in point-source geometry. However, specially designed irradiation positions and carefully planned measuring conditions enabled the activation and analysis of samples with weights up to several tens of kilograms. A dedicated character of irradiation and of measuring conditions was the main reason for a very limited application of such activation analysis. The use of routine irradiation facilities and standard conditions for analytical gamma-spectrometric measurements is described. Starting with samples of some hundred milligrams usually used in activation, through multi-gram samples to several hundred gram samples, irradiation and measuring conditions were studied and tested for development of the method. This work began in 1991 in Denmark, using the Danish DR-3 reactor. Since then different aspects of the method have been investigated on 6 reactors; in Denmark on DR-3, in Austria on Triga-MkII (in Vienna), and Astra (in Seibersdorf), in the German Federal Republic on FRG-1 in Geesthacht, in Norway on Jeep II (in Kjeller), and in Kazakhstan on VVR-K (in Alatau). Altogether more than 1000 samples have been irradiated and measured. In total, the roughly 30 kg of irradiated materials included almost 300 large samples of more than 30 gram weight. The following theoretical and practical aspects were investigated during the work: theoretical problems concerning neutron self-absorption in common organic and inorganic materials, as well as gamma-attenuation during the measurement. From a more practical point of view: health physics and radiation hazards during irradiation, measurement, transportation and storage of samples with several hundred grams weight. Special requirements to irradiation containers were formulated and various containers were tested. Main advantages and drawbacks of the method are discussed.     

Contamination by human fingers: The Midas touch

Anthropogenic activity is one of the causes of contamination in the human environment: contamination of air, water, top soils, plants and food products has complex effects on human health problems. Wear and abrasion of various surfaces are constant processes in daily life, and commonly include interaction between human fingers and surfaces of every conceivable material. New methods for investigation of trace transfer processes by human fingers are described. Results of transfer for commonly used metals such as gold, silver, zinc, cadmium, tin, cobalt, nickel, chromium and iron are presented. Relationship between transfer of metals by touch and the general problem of purity in analytical activities is briefly discussed.     

Standardization problems in INAA of large organic samples

For the practical application of large sample activation analysis, an extensive characterization of the irradiation facility and of the measurement system — of sample size, flux-gradient, maximum count rate, size of irradiation and counting containers, estimation of created activity after irradiation and dose rate — is required. The term, “large samples” is not unequivocal. Here the consideration is restricted to samples from several grams to 100 or 200 grams, which can be irradiated in existing irradiation facilities. Calculations were performed for about 1200 organic samples divided into 18 groups. The results are in about 400 tables. The effective Z number, Z/A ratio, mass attenuation for several gamma lines, the relative contribution of the main absorbing elements in the sample for effective cross sections and for gamma transmission are calculated for each sample. All these data have been calculated for various sizes of irradiation and measuring containers. Macroscopic thermal, epithermal, scattering and transport cross sections were used for calculation of self-shielding by five different methods. Owing to the limited space only a selection of the most pertinent values characterizing each group of samples is presented and discussed. The main differences of Large Sample NAA to other nuclear analytical methods are self-shielding and gamma attenuation in the sample. The main object of this paper is to show up problems that may arise in LS-NAA through self-shielding and gamma attenuation.     

Progress in Activation Analysis at the Atomic Institute Vienna

Fields in which progress has been achieved at the Atomic Institute Vienna are discussed briefly. The use of short and medium lived nuclides for activation analysis (AA). Construction of out-core parts of a fast transfer system. Combined sample catcher sample-changer for AA allowing cyclic and pseudocyclic AA. A system for discontinuous or continuous irradiation of liquid samples. Counting with an anticompton shield and quantitative correction of random coincidences. Screening analyses with the fast irradiation and measurement system. Improved peak-evaluation of gamma-spectra. Epithermal AA by a neutron converter. Following short-lived nuclide measurement, automatic sample transfer into a well-type detector enabling sensitive counting of nuclides with short half-lives. Use of large samples to increase the detection limits of ng to pg at activation with moderate neutron flux. Flux determination by liquid scintillation counting.     

Determination of some elements in Ageratum conyziodes,a tropical medicinal plant, using instrumental neutron activation analysis

1-Hydroxy-2-ethylthioethane, CH₃CH₂SCH₂CH₂OH, (HETE) gave relatively stable intermediate sulfonium cations, with water solutions of mineral acids, which could be extracted into chloroform as ionic associates in the presence of bis(1,2-dicarbollyl)cobaltate anions labeled with ⁶⁰Co independently of the nature of the inorganic anion but depending on the activity of hydrogen ions. The water phase contained buffers and acids HCl, H₂SO₄, H₃PO₄ and HClO₄. The kinetics and mechanism of the reactions have been studied. This revised version was published online in August 2006 with corrections to the Cover Date.     

Instrumental neutron activation analysis of samples with masses from micrograms to hectograms

The rotating rig at the Danish DR-3 reactor was used for irradiation of samples with masses from a hundred micrograms to several hundred grams. The pneumatic post for uranium delayed neutron counting was used for automatic sequential irradiation of samples subdivided into up to 24 aliquots, each with a volume of 7 cm³. The cumulative samples were measured in polyethylene irradiation containers in a specially designed radial holder.