(514a) Innovative Separations Technologies for Nuclear Fuel Cycles

Technologies for separating used nuclear fuel have been researched, developed, or used for over 60 years.  These separations processes are based on either (a) selective solubility of different species in different aqueous, organic liquid, or molten salt solvents, or (b) selective volatility of different species at different temperatures.  To date, only limited examples of separations processes have been tested or used at scales beyond demonstration scales.  Dissolution and separation using aqueous and organic solvents has been used at full scale in several different countries.  Electrochemical separations using molten salts as the solvent has been performed on a small-scale, non-commercial basis.  Separations based on volatility has been researched and demonstrated for the past 50 years, but not yet used at a commercial scale. 

Five innovative separations projects have been funded by the U.S. Department of Energy through the Separations Campaign to research and develop potentially transformational separations concepts and technologies.  These are:

• Nitrogen Trifluoride for UNF Processing
• Reactive Fluoride Gas (SF₆) for UNF Processing
• Dry Head-end Nitration Processing
• Chlorination Processing of UNF
• Enhanced Oxidation/Chlorination Processing of UNF.

While these projects are still in their early stages, a combined Separations Campaign and Systems Analysis Campaign review of these projects has been performed to assess their potential fuel cycle impacts.  This review, summarized in this paper:

• Describes the features of each innovative process
• Describes where each process might fit within the currently-defined fuel cycle option space
• Indicates how the innovative processes are unique compared to the existing separations processes
• Identifies data gaps, and recommends future research and development.

Studies of these innovative processes have only recently been initiated.  Data gaps exist that prevent a more complete evaluation.  Research and development needed to fill those data gaps include:

• More complete determination of separation factors
• Modeling using the Fuel Cycle Integration and Trade-off (FIT) model to estimate usability of recycle product materials for multiple recycles; levels of contamination compared to known fuel limits; compositions, heat, and radiotoxicity of the waste streams; and separations efficiencies needed to enable viable fuel with acceptable levels of contaminants.
• Mass balances to assess process flowrates, equipment size requirements, amounts of reagents, etc.
• More complete process definition such as halide recycling, operating temperatures, corrosion and equipment degradation, handling of solids materials, and process performance
• Development and demonstration of waste form concepts.