Scrap and Contaminated Metals Recycling

Methods Development: Nickel Purification and Recovery Project

Background

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 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 National Laboratory (1969) and Los Alamos National Laboratory (1983), but are no longer available.  A University of Kentucky 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.  

Research Outcomes:

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.

Goals

  1. Finalize design and build specially adapted MS for metal vapor study.
  2. Obtain vapor-liquid-solid phase equilibria data
  3. Provide written summary of equilibria data collection findings
  4. Apply equilibria findings for prototype design
  5. Build and test bench-scale pilot reactor
  6. Provide summary report for prototype design and bench scale study

Project 9: Purification and Recovery of Radiologically Contaminated Metals

Document TitleDescriptionYear
Separation of Nickel from TechnetiumProject Report2004
Nickel-Technetium Separation by Metal Distillation and Vapor Deposition PACRO PresentationPresentation to Paducah Area Community Reuse Organization (PACRO)2004
Separation of Nickel from Technetium-Contaminated ScrapPresentation to the Paducah Area Community Reuse Organization (PACRO)2007
Metal Separation Technologies Expression of InterestResponse to Expression of Interest Request2007

Investigators

Project Manager
Steve Hampson, Associate Director/Co-Principal Investigator, University of Kentucky, Kentucky Research Consortium for Energy & Environment
Principal Investigators
Dr. Tony Zhai, Ph.D., Professor University of Kentucky, College of Engineering
Eric Grulke, Ph.D., Professor University of Kentucky, College of Engineering
Team Members
Louie El-Asami
Dr. John Volpe
Bert Lynn, University of Kentucky