Alternative Electrochemical Salt Waste Forms, Summary of FY11-FY12 Results

Abstract

The Fuel Cycle Research and Development Program, sponsored by the U.S. Department of Energy Office of Nuclear Energy, is currently investigating alternative waste forms for wastes generated from nuclear fuel processing. One such waste results from an electrochemical separations process, called the "Echem" process. The Echem process utilizes a molten KCl-LiCl salt to dissolve the fuel. This process results in a spent salt containing alkali, alkaline earth, lanthanide halides and small quantities of actinide halides, where the primary halide is chloride with a minor iodide fraction. Pacific Northwest National Laboratory (PNNL) is concurrently investigating two candidate waste forms for the Echem spent-salt: high-halide minerals (i.e., sodalite and cancrinite) and tellurite (TeO 2 )-based glasses. Both of these candidates showed promise in fiscal year (FY) 2009 and FY2010 with a simplified nonradioactive simulant of the Echem waste. Further testing was performed on these waste forms in FY2011 and FY2012 to assess the possibility of their use in a sustainable fuel cycle. This report summarizes the combined results from FY2011 and FY2012 efforts.The chemical durability results for the tellurite glasses in FY2010 revealed a wide variation of waste form performance in these materials. The most promising glass studied was a lead-tellurite glass formulation with the Echem salt simulant. This glass showed very good chemical durability with a normalized release for sodium of 0.478 g/m 2 following a seven-day product consistency test. With this in mind, the following studies were undertaken in FY2011 and FY2012 to further investigate and optimize this type of glass as a potential waste form:Alternative Electrochemical Salt Waste Forms, Summary of FY11-FY12 Results January 17, 2014 v CRADA-PROTECTED INFORMATIONfor Al:Cl (3:1) and Si:Cl (3:1), on a molar basis, where the alkali fraction (R 1+ ) was intentionally below the target of 4:1 (R 1+ :Cl) to help influence the incorporation of alkaline earth (R 2+ ) and Ln (R 3+ ) components from the XCl 20 into the sodalite structure. The results from this study showed that each formulation had advantages and disadvantages where SM-3 pellets had high density and low sodalite production and SM-2 pellets had very high sodalite production with modestly high densities. A mixture of these methods will likely be considered in FY2013.

Structural dependence of crystallization in phosphorus‐containing sodium aluminoborosilicate glasses

“…Under the Materials Recovery and Waste Form Development (MRWFD) Campaign, the US Department of Energy-Office of Nuclear Energy (DOE-NE) is investigating waste forms for immobilizing chloride-rich salt waste generated during the reprocessing of used nuclear fuel (UNF) by the electrochemical separations (Echem) process. 41 The waste stream is primarily composed of KCl-LiCl eutectic salt with minor amounts of Na, Cs, Rb, Ba, Sr, lanthanides, and trace transuranic (TRU) chlorides. The US DOE scientists have recently developed a method to dehalogenate the chloride-rich salt waste using ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ).…”

Evaluation of the Vapor Hydrolysis of Lithium Aluminum Hydride for Mobile Fuel Cell Applications

“…The PXRD pattern of the mixture of LiOH/Al(OH) 3 matched that of LiOH (ICDD 25-0486). 22 Aluminum hydroxide cannot be identified in the pattern as it is amorphous and hence no sharp reflections are observed.…”

Solution-derived sodalite made with Si- and Ge-ethoxide precursors for immobilizing electrorefiner salt

“…The NBS-1 and NaAlP binders were provided by collaborators as powders and not made new for this study. The TePbO glass was selected because it has a high loading for the same mixed salt waste that was used in this study [14][15][16][17].…”