Characterization of Transport and Solidification in the Metal Recycling Processes

Abstract

The characterization of the transport and solidification of metal in the melting and casting processes is significant for the optimization of the radioactively contaminated metal recycling and refining processes. . In this research project, the transport process in the melting and solidification of metal was numerically predicted, and the microstructure and radionuclide distribution have been characterized by scanning electron microscope/electron diffractive X-ray (SEWEDX) analysis using cesium chloride (CSC1) as the radionuclide surrogate. In the melting and solidification process, a resistance furnace whose heating and cooling rates are program- controlled in the helium atmosphere was used. The characterization procedures included weighing, melting and solidification, weighing after solidification, sample preparation, and SEM/EDX analysis. This analytical methodology can be used to characterize metal recycling and refining products in order to evaluate the performance of the recycling process. The data obtained provide much valuable information that is necessary for the enhancement of radioactive contaminated metal decontamination and recycling technologies. The numerical method for the prediction of the melting and solidification process can be implemented in the control and monitoring system-of the melting and casting process in radioactive contaminated metal recycling. The use of radionuclide surrogates instead of real radionuclides enables the research to be performed without causing harmfid effects on people or the community. This characterization process has been conducted at the Hemispheric Center for Environmental Technology (HCET) at Florida International University since October 1995. Tests have been conducted on aluminum (Al) and copper (Cu) using cesium chloride (CSCI) as a radionuclide surrogate, and information regarding the radionuclide transfer and distribution in melting and solidification process has been obtained. The numerical simulation of the solidification of molten metal has been very successful for aluminium; however, a stability problem in the simulation of iron/steel solidification poses a challenge. Thus, additional development is needed to simulate the radionuclide transfer and distribution behaviors in the melting and casting processes. This project was initially based on a two-year plan. However, due to technical and financial difficulties, the project ended in FY96. The work which has been accomplished in the first year includes the characterization of radionuclide transfer and distribution in the melting-solidification process and the numerical simulation of metal solidification. The Argon-arc melting method was tested for the melting of copper and steel materials. Five tests were performed to characterize the transfer and distribution of radionuclides in the aluminiurn and copper melting/solidification process using CSC1 as radionuclide surrogates. The numerical simulation of molten aluminium and steel solidification process was performed. Different boundary conditions were applied in the simulations.