Properties of Shock‐Compressed Carbogal. Equations of State for Carbogal and Plexiglas

This paper presents results from experimental studies of the properties of Carbogal (C₈F₁₆ or perfluoro1,3dimethylcyclohexane), at high pressures and temperatures, in particular, data on single compression and recompression, temperatures, and velocity of sound. Data are given on shockwave compressibility of porous Plexiglas with an initial density 10–60 times lower than the density of the solid sample. Thermodynamically complete equations of state for Carbogal and Plexiglas are developed on the basis of a model published previously and wellknown experimental data. It is shown that calculations using the developed equations of state are in agreement with available experimental data for Carbogal up to pressures of 70 GPa and for Plexiglas over the entire examined range of pressures.     

X-ray spectral determination of gold in geological samples after its concentration by low-temperature fire assay

The technology of gold extraction to lead from its mixture with the sample powder during lowtemperature alkaline fusion is developed. The optimal ratios of masses for the sample, lead, and alkali, as well as heating conditions, temperature, and fusion duration, are determined for satisfactory gold recovery. A low temperature of fusion makes it possible to lighten the structure of furnaces, to decrease energy consumption, and to shorten the duration of the entire cycle from the beginning of fusion until the next set of crucibles is loaded. Using the modular approach, a furnace can be assembled in a small area for the simultaneous fusion of a great number of samples. The results of determining gold by the X-ray fluorescence method obtained by using the proposed concentration technology satisfy the regulatory requirements with respect to accuracy.     

A Device for the Remote Detection of Alpha Emitters under Field Conditions

The portable ДOP device was designed for the ecological monitoring of the radiation of alpha radioactive nuclides, such as plutonium, uranium, radium, etc. Under field conditions, it can detect alpha emitters at distances of up to 0.5 m. The device’s performance data are as follows: the lower threshold of the particle energy is 0.2 MeV, single measurement time is no more than 10 s, and the minimum detectable activity is 1000 Bq.__________Translated from Pribory i Tekhnika Eksperimenta, No. 3, 2005, pp. 122–126.Original Russian Text Copyright © 2005 by Simakov.     

Dinitrogen formation over low-exchanged Cu-ZSM-5 in the selective reduction of NO by propane

The role of gaseous NO and C₃H₈ has been studied over low-exchanged Cu-ZSM-5 zeolite employing TPD, FTIR and pulse technique with the alternate introduction of NO or C₃H₈ onto the catalyst surface. The rate of the N₂ formation is directly proportional to the content of gaseous NO and the surface coverage with 2-nitrosopropane. There was no formation of N₂ during interaction of gaseous C₃H₈ with NO adsorbates. However, 2-nitrosopropane and its isomer acetone oxime were also formed in this reaction. This revised version was published online in November 2006 with corrections to the Cover Date.     

Shock compression and isentropic expansion of porous samples of tungsten, nickel, and tin

The isentropic expansion is investigated of shock-compressed porous samples of tungsten, nickel, and tin from the states on shock adiabats at a pressure of 60–150 GPa to states realized under conditions of release into air. The obtained data are compared with the results of calculations by two wide-range model equations of state.     

Three-dimensional shielding calculations for the IFMIF neutron source using a coupled Monte Carlo/Deterministic computational scheme

Shielding calculations for the International Fusion Materials Irradiation Facility (IFMIF) are complicated due to the geometrical complexity of the target system and the large-scale bulk shields around the source target. Three-dimensional shielding calculations were performed by using a newly developed Monte Carlo/Deterministic computational scheme. The neutron-photon fluxes and dose rate distributions in the back wall of the Test Cell and the access/maintenance room are presented and compared with previous shielding calculations. The results demonstrate that this coupled scheme is an useful computational tool for three-dimensional shielding analyses of complex and large nuclear facilities.     

Shock Compression of Porous Aluminum and Nickel at Megabar Pressures

Data are given on shock compression of porous samples of aluminum with the initial density ₀₀= 0.34 g/cm³and nickel with ₀= 0.44 and 0.32 g/cm³. In the case of aluminum, all results are obtained for the first time ever. The range of pressure being investigated is from 0.25 to 76 GPa. For nickel, a shock adiabat is found with the porosity m= ₀/₀₀= 28 (which is the highest porosity for metals) and an adiabat with m= 20 at a pressure of 92 GPa, which is approximately twice the respective values obtained previously. Comparison is made with the results of other researchers.     

Model‐based optimization of hydrogen generation by methane steam reforming in autothermal packed‐bed membrane reformer

An autothermal membrane reformer comprising two separated compartments, a methane oxidation catalytic bed and a methane steam reforming bed, which hosts hydrogen separation membranes, is optimized for hydrogen production by steam reforming of methane to power a polymer electrolyte membrane fuel cell (PEMFC) stack. Capitalizing on recent experimental demonstrations of hydrogen production in such a reactor, we develop here an appropriate model, validate it with experimental data and then use it for the hydrogen generation optimization in terms of the reformer efficiency and power output. The optimized reformer, with adequate hydrogen separation area, optimized exothermic‐to‐endothermic feed ratio and reduced heat losses, is shown to be capable to fuel kW‐range PEMFC stacks, with a methane‐to‐hydrogen conversion efficiency of up to 0.8. This is expected to provide an overall methane‐to‐electric power efficiency of a combined reformer‐fuel cell unit of ～0.5. Recycling of steam reforming effluent to the oxidation bed for combustion of unreacted and unseparated compounds is expected to provide an additional efficiency gain. © 2010 American Institute of Chemical Engineers AIChE J, 2011