Authors:N. Ben Ezzine, M. Barhoumi, K. Mejbri, and A. Bellagi
Summary This paper deals with the modeling, thermodynamic analysis and comparison of irreversibility in two configurations of the double generator absorption chiller. First a computer simulation model is developed for each configuration on the basis of mass and energy balances. Simulation results were then used to analyse the entropy generation and irreversibility (or exergy destruction) of each component. It is found that the parallel flow configuration is more powerful than the serie flow configuration. Exergy losses in the parallel flow configuration are lower than that of the serie flow. The results indicate that the absorber and the solution heat exchangers have the most potential to improve the chiller energy efficiency. Also they indicate that focusing on irreversibility is more direct way of analysing the potential for improving the efficiency of ammonia-water absorption chiller.
Procedures and results of CH3131I absorption in water and ethanol solutions have been studied. These are: 1%, 5%, 15%, 30%, 50% or saturated solutions Na2S2O3, C6H5–OH, Hg2(NO3)2, AgNO3, K4(Fe(CN)6), KI, NaOH, KOH and (COOH)2. Methyl iodide was carried with the laboratory air stream through five bubblers filled with a selected solution. The CH3131I released from the last bubbler was absorbed in 2 cartridges in series filled with 5% TEDA impregnated charcoal. Efficiency of CH3131I absorption was studied in dependences of the kind of solutions, their concentrations, order of bubblers and CH3131I concentration in the carrier air. Results of these experiments are discussed.
A method previously developed in this group for the determination of elemental profile distributions by measuring with a Pb
collimator and again with a non-collimating Pb absorber of the same thickness present has been examined with the aim of describing
the dependence of the resulting relative error on the thickness of the absorber. The results of calculations based on a detailed
analysis of γ-absorption in Pb reproduce the experimental data satisfactorily and provide a guide for confining the relative
error of measurement to within reasonable limits.
Authors:X. He, Z. Zhang, L. Feng, Z. Li, J. Yang, Y. Zhao, and Z. Chai
After an acute exposure to lanthanum chloride, the pharmacokinetics of calcium uptake in rats was studied by radioactive 47Ca tracer. The accumulated doses of calcium in the left femurs during 24 hours were determined. The results showed that the
area under the curves (AUC), specific activity of maximal blood 47Ca concentration (Cmax), distribution rate constant (Ka) and the accumulated dose of calcium in the left femur decreased while time to Cmax (Tpeak) increased with the rising dosage of lanthanum exposure. It indicated that lanthanum expose had a negative effect on calcium
Authors:M. Cantone, D. De Bartolo, G. Gambarini, A. Giussani, N. Molho, L. Pirola, Ch. Hansen, E. Werner, and P. Roth
An investigation on tellurium metabolism by administration of stable tellurium isotopes124Te and126Te has been performed. Fractional intestinal absorption was determined in rabbits by the double tracer technique. The investigated subjects were given an enriched solution of one tellurium isotope orally and a few minutes later an enriched solution of the other isotope intravenously. The124Te and126Te contents in plasma samples were determined by proton nuclear activation. The methodology described offers a means to study tellurium metabolism in humans without radiation risk.
Authors:Paula Bachelor, David Jordan, Warren Harper, Bret Cannon, and Erin Finn
Nitrogen fluorescence induced by radiation can be used to detect the presence of radioactive contamination in the environment.
Contamination quantification from the fluorescence signal requires: the source’s effective alpha spectrum; the specific radiation
quantum fluorescence efficiency; optical attenuation length in air of the fluorescence signal; the absolute throughput and
quantum efficiency of the optical instrumentation; calibration of the instrumentation; and radiation transport modeling of
the “effective” array exposure rate given the alpha particle spectrum. Field testing conducted on optical instrumentation
measured the nitrogen fluorescence yield generated by 241Am alpha emissions. Laboratory studies of 241Am via alpha spectrometry determined whether the presence of solids on source surfaces produced sufficient self-absorption
to decrease fluorescence. Results from the laboratory studies provided correction to the effective alpha-source activity values
in a model of the earlier optical-sensor field measurements, and determined the air fluorescence efficiency of alpha particles
generated by the 241Am sources used in the field experiments.
Authors:Frederic Poineau, Charles Yeamans, G. Silva, Gary Cerefice, Alfred Sattelberger, and Kenneth Czerwinski
Uranium mononitride (UN), sesquinitride (U2N3) and dinitride (UN2) were characterized by extended X-Ray absorption fine structure spectroscopy. Analysis on UN indicate the presence of three
uranium shells at distances of 3.46(3), 4.89(5) and 6.01(6) Å and a nitrogen shell at a distance of 2.46(2) Å. For U2N3, two absorbing uranium atoms at different crystallographic positions are present in the structure. One of the uranium atoms
is surrounded by nitrogen atoms at 2.28(2) Å and by uranium atoms at 3.66(4) and 3.95(4) Å. The second type of uranium atom
is surrounded by nitrogen atoms at 2.33(2) and 2.64(3) Å and by uranium atoms at 3.66(4), 3.95(4) and 5.31(5) Å. Results on
UN2 indicate two uranium shells at 3.71(4) and 5.32(5) Å and two nitrogen shells at 2.28(2) and 4.34(4) Å. The lattice parameters
of UN, U2N3 and UN2 unit cells were respectively determined to be 4.89(5), 10.62(10) and 5.32(5) Å. Those results are well in agreement with
those obtained by X-Ray diffraction analysis.
Authors:C. C. Dantas, R. Narain, V. A. dos Santos, and A. C. B. A. Melo
The axial and radial distribution of the catalyst concentration, in the riser of an EMC - experimental cold model of a fluid
catalytic cracking type unit, was measured by gamma-absorption. The solid concentration in the circulating fluidized bed was
determined by measurements with a 241Am gamma-source and a NaI(Tl) detector. The operation, instrumental measurements and data acquisition system of the cold unit
were automated. The catalyst concentration measurements were carried out in static experiments and in the circulating fluidized
bed. A calibration of the distribution concentration was made with experimental data from gas velocity and pressure drop along
the riser that gave the best multi-regression model. A spatial resolution of 5.0 . 10-3 m by scanning the riser and a catalyst density resolution of 5.0±0.8 kg/m3 were obtained. The axial catalyst concentration distribution, in the 5-13 kg/m 3 interval, showed a predicted pattern according to the literature. The radial distribution was in an annular configuration
for this diluted catalyst concentration.
Authors:A. Rzama, M. Misdaq, H. Erramli, G. Blondiaux, D. Isabelle, and J. Bajard
Gamma-ray self-absorption in stainless steel samples has been studied with an experimental method based on fast neutron activation and a Monte Carlo calculation technique adapted to the experimental conditions. A relation between self-absorption and absorption of -photons inside stainless steel samples was found. The influence of the -ray energy and sample depth have been investigated. Agreement between the two methods has been found.