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An optical emission spectroscopy (OES) method has been used to measure the concentration above the melt of some radioelements,
137Cs, 60Co and 106Ru during the vitrification of radioactive wastes by thermal plasma. This method allows the study of non homogeneous optically
thin plasmas exhibiting a symmetry plane without sophisticated tomographic systems. Local plasma temperatures above the melt
have been evaluated using measured relative intensities of spectral lines of the plasma-forming gas. Radioelement concentrations
in the plasma are deduced from the intensity ratio of the radioelement–gas spectral lines. A computer model is used to simulate
the volatility of 137Cs, 60Co and 106Ru, during the treatment of radioactive wastes by thermal plasma. This model is based on the calculation of system composition
using the free enthalpy minimization method, coupled with the equation of mass transfer at the reactional interface. In this
study, the OES measurements and the computer model allowed the determination of this radioelement volatility depending on
the parameters like plasma current, and the nature of atmosphere furnace. The results of the model are compared to those obtained
by OES measurements. 相似文献
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Frugier P. Girold C. Megy S. Vandensteendam C. Ershov-Pavlov E. A. Baronnet J.-M. 《Plasma Chemistry and Plasma Processing》2000,20(1):65-86
Results are presented of optical emission spectroscopy (OES) application asa control tool to improve fly-ash plasma vitrification. A twin-torch plasmasystem has been used for the fly-ash processing, and a new OES method hasexamined metallic vapors above the melt. The method allows the study ofnonhomogeneous optically thin plasmas exhibiting a symmetry plane withoutsophisticated tomographic systems. The dc arc torches are mounted above acold crucible filled with a synthetic glass. The arc intensity is from200 to 400 . Argon is introduced into the torches along the cathodeand the anode, while argon, oxygen or hydrogen are injected through thelance between the torches. Local plasma temperatures above the melt havebeen evaluated using measured relative intensities of spectral lines ofthe plasma-forming gas. Metallic vapor concentration in the plasma isdeduced from the intensity ratio of the metal–gas spectral lines. Leadoxide has been used to study heavy-metal behavior at the fly-ash plasmavitrification. Distribution of the lead along the crucible surface,depending on the plasma-forming gas composition as well as the concentrationevolution with time, have been examined. The elemental analysis of theresultant glass has been measured by scanning electron microscopy (SEM)with energy-dispersive spectrometry (EDS). A predictive model has beenadapted to simulate the noncongruent vaporization of heavy metals from themelt. According to the data obtained, steep variations of the volatility ofthe elements depend strongly on reducing properties of gases controllingthe plasma composition near the melted surface. In addition, the melttemperature and the redox potential of the gas phase are found to be themost critical parameters. 相似文献
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