Scrap and Contaminated Metals

There is an estimated 9,000 tons of radioactively contaminated nickel in the form of ingots stored at the current and former uranium enrichment plants in Paducah, KY, Portsmouth, OH, and Oak Ridge, TN. Nickel has a particularly high scrap value, but a moratorium by the DOE on commercial reuse of any radioactively contaminated metals prevents its sale. Disposal costs would be quite high, and result in the loss of the material as a valuable resource. This project would lead to the establishment and validation of a process whereby the nickel can be made as clean as or cleaner than conventional commercial nickel relative to radioactive contaminants. There are two portions of this proposal.

Goals

1. Develop a technology to remove radionuclide contaminants from existing U.S. Department of Energy stockpiles of nickel ingots.
2. Apply the developed technology to purify the contaminated nickel inventory in Paducah.

Objectives

1. Provide a summary (and timeline) of the history of the issues with regard to the release of the nickel. Information in this summary and timeline should include:
   • Amount of nickel
   • Use
   • Types of Contamination
   • Release Standards
   • Moratorium
   • Efforts by PACRO
   • Claims and Efforts by CVDR
   • Other
2. The principal investigator (PI) will report on the possible economic paths forward for the nickel at Paducah (what is the potential economic benefit to Paducah with each of these scenarios)? This analysis will be incorporated into a course in engineering economics (CME455 Process Design 1) where the students will develop tools to perform this analysis based on variable assumptions. The result of incorporating this analysis into this course and its contribution to meeting educational objectives for the course will be reported at the ASEE Annual Meeting in 2006.Expected Scenarios:
   • No release
   • DOD comes in and takes the nickel and uses it in their complex
   • DOD comes in and cleans it up some (e.g. CVDR) and uses it with DOD
   • DOD allows the nickel to be cleaned by a third party and released to the public
   • other
3. Perform an analysis of the following issues and constraints surrounding the nickel release.
   • Technical (How clean does it have to be? What are the technical challenges with that level? What type of verification process would be required to “prove” the nickel could be cleaned to that level? How many samples would be necessary to demonstrate the feasibility of the process, etc.)
   • Regulatory (What current regulations are relevant to the cleanup of the nickel and the facilities required to clean the nickel, e.g. facility permitting, etc.)
   • Political (Why was the moratorium imposed, what would be required for it to be lifted, what is the position of the nickel industry, the nickel industry unions, the general public? What specific barriers exist with each group? What would be necessary to eliminate those barriers?)
4. Provide recommendations for dealing with the above barriers. A report will be delivered at the end of the project, approximately June 30, 2006. Interim progress reports will be delivered as requested.

Batteries have become an important aspect of energy storage in the United States. The battery industry has become a $10 Billion a year business. Battery construction materials include zinc, manganese, lithium, and many more. One metal that has received sparse attention as a candidate for battery construction material is uranium. Based on the electrochemical literature, uranium is likely to have a significantly higher power density than lead which is commonly used in secondary power batteries.  In fact, uranium may have similar electrochemical properties to lithium.

The Paducah Gaseous Diffusion Plant (PGDP) located in the western part of the Commonwealth of Kentucky contains cylinders with over 5 billion pounds of uranium hexafluoride (UF6). UF6 will be recycled into uranium and fluoride compounds. This will provide a large supply of depleted uranium.

Goals

1. Characterize uranium dioxide’s electrochemical properties in various organic solvents/lithium salts commonly used in the commercial battery industry. These experiments will be performed in a glove box where the moisture and oxygen concentration will be controlled. These tests will mainly consist of cyclic voltammetry and impedance spectroscopy experiments. This information will be used to construct a battery with uranium dioxide as the cathode.
2. Manufacturing of uranium-lithium compounds in a muffle furnace to mirror the construction of manganese-lithium compounds commonly used in commercial batteries. Once these compounds are manufactured, their electrochemical behavior in common organic solvent/lithium salts will also be characterized. This information will also be used to construct a battery consisting of lithium-uranium dioxide.

Objectives

The objectives are to electrochemical data suitable for properly designing two batteries:

• Uranium dioxide as a cathode in a lithium battery and test its performance
• Make a uranium dioxide-lithium compound similar to manganese dioxide-lithium compound and provide electrochemical data suitable for a similar battery.

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