Global Technologies, Inc. (GTI) and Commodore Applied Technologies have been contracted by DOE’s Idaho Operations Office to conduct the Proof of Principle Experiments with Anhydrous Ammonia to Demonstrate the Removal of Sodium from Liquid Metal Reactors. This bench-scale research project is confirming the feasibility of using anhydrous liquid ammonia to dissolve sodium residues from components in liquid metal-cooled reactors without generating hazardous byproducts. At present, sodium typically is decontaminated by water vapor carried in an inert gas, but this generates dangerous hydrogen gas plus RCRA-regulated sodium compounds.

Bench-scale experiments were conducted in 2000 in GTI’s laboratory at the Bonneville County Technology Center on non-radioactive, surrogate components representing Fermi Reactor blanket fuel. Each specimen was fabricated from stainless steel, and a small amount of metallic sodium was melted in each mockup. Specimens were immersed in liquid ammonia at -6° C (pressure of 4 atmospheres) to dissolve the sodium, which required only minutes in narrow annular spaces. Non-hazardous copper iodide was added by titration to form non-hazardous sodium iodide and copper. After ammonia evaporation, reaction products were analyzed by x-ray diffraction.

Chemical Basis: Like water, some liquid ammonia disassociates into ions according to:

2NH₃ Û NH₄⁺ + NH₂^-

These free ions and the polar nature of the NH₃ molecule free an electron from an alkali metal (such as sodium) when it is introduced to liquid ammonia.

Na (metal) Þ Na⁺ (ammoniated) + e^- (solvated)

Sodium is soluble in liquid ammonia up to approximately 8 weight percent, so macroscopic amounts of sodium metal rapidly dissolve, even as solid lumps. Solvated electrons are highly conductive and display a characteristic deep blue color in liquid ammonia. When copper iodide is added to a solution of ammonia and sodium, the sodium reduces the copper iodide to form sodium iodide and metallic copper:

CuI + Na⁺ + e^- Þ Cu + NaI

The solvated electrons combine with the copper ions to form metallic copper. Consequently, the blue color of a solvated electron solution disappears, and the liquid ammonia returns to its original transparent color. Conductivity also decreases markedly.

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