Project 9: Purification and Recovery of Radiologically Contaminated Metals
Eric Grulke, Ph.D., Professor University of Kentucky College of Engineering
Dr. Tony Zhai, Ph.D., Professor University of Kentucky College of Engineering
There is interest in recovering and recycling the nickel, although there are many regulatory issues associated with any use of such material outside of the nuclear industry. The current separation technologies for the Ni/Tc pair; ion exchange, solvent extraction, melt refining, inductoslag refining, and electrolysis, do not meet the release criteria for radioactive materials. The best available electrolysis process still leaves about 1 Bequerel of technetium activity per gram for materials starting at 320 Bequerels. Other radioactive materials can be separated from nickel via electrolysis processes. This project will obtain the data necessary to evaluate a new alternative separation method that is based on the differences between the vapor pressures of nickel and technetium over solid and liquid solutions of the pair.
This project seeks to develop and demonstrate a technically effective and cost-efficient process using physical vapor deposition to recover pure nickel with no detectable traces of technetium. The slag left behind will be composed of technetium with small levels of nickel. Several separation systems can be envisioned: batch separation in which nickel is preferentially evaporated from solid or liquid solutions of Ni/Tc and condensed on cold surfaces for recovery and continuous distillation in which a specially designed, insulated and instrumented column is used for the separation (similar in concept to the separation of organic liquids by boiling point). Dr. Eric Grulke has experience in industrial process design and separations.
A physical vapor-deposition process can be designed only after the project obtains fundamental data on the vapor-liquid-solid-solid phase equilibria of the metal mixtures in question. A unique MS (mass spectrometer) system designed for metal vapor service will be constructed to obtain the needed data. Similar systems were constructed at Lawrence Livermore Lab (1969) and Los Alamos (1983), but are no longer available. A UK expert on MS, Bert Lynn has designed other specialized MS instruments and will collaborate on design, construction, validation, and commissioning of the new MS.
The data obtained with the GC/MS will redefine the phase diagrams for metallic mixtures, and will permit thermodynamic phase equilibria models to be developed and applied to the process design. The data necessary to proceed with process design includes vapor pressures, heat of vaporizations, heats of sublimation, activity coefficients, and separation factors for the nickel-technetium pair at different temperatures. The data will be incorporated into phase diagrams that include the vapor phases. Dr. Tony Zhai will apply metallurgy principles to process applications of the problem.
The proposed research will investigate the physiochemical system of nickel-technetium. There are no phase diagrams that relate metal vapor compositions to their liquid-solid phase compositions. This approach is relatively unexplored, and has applications for many non-radioactive systems as well, such as scrap metal recycling and alloy purification. The nickel-rhenium system has been chosen to be a model system to validate the performance of the new MS because its liquid phase diagram behaves similarly to that of Ni/Tc and rhenium is not radioactive.
1. Quarterly progress reports.
2. Project progress presentation at quarterly meetings.
3. Operational MS metal vapor unit
4. Written report summarizing equilibria data collection findings
5. Operational bench-scale pilot reactor
6. Written report summarizing results of bench scale operations
Dr Eric Grulke
Dr. Tony Zhai
Dr. John Volpe
KRCEE is a collaborative effort of Kentucky universities and is administered by the University of Kentucky.