Process For Dissolving Aluminum For Recovering Nuclear Fuel

Example 1

[0035]Single-impurity scoping experiments to determine the influence of individual contaminants on off-gas rate were initially performed using Al-1100 alloy coupons. A series of four Al-1100 coupons were cut to the approximate dimensions of 19×11×3 mm. A 1 / 16 inch hole was drilled into each coupon in order to fasten each coupon to the glass rods used to lower them into a dissolving nitric acid solution. The coupons were lightly sanded, washed with soap and water, and then weighed and measured. Each coupon weighed approximately 1.7 g and had a surface area of approximately 6 cm2. Each coupon was tied by Teflon™ string through the 1116 inch hole to a glass rod on the dissolver apparatus that was labeled with the coupon position number for coupon identification.

[0036]A dissolver apparatus and off-gas collection system were assembled in a chemical hood. The dissolver apparatus contained a boiling flask with multiple ports, a condenser, an in-line gas sample glass bulb, and a wat

[0037]Experiment 1 was conducted using a dissolving solution of 7 M HNO3, 0.1 M KF, and 0.002 M Hg, and no contaminants. Nominally 150 mL of dissolving solution was weighed, added to a flask containing a Teflon™ stir bar, and then sealed. The dissolution vessel and off-gas collection system (including 8 sample glass bulbs) were leak checked by filling the system with Ar to inflate the Tedlar™ bag and observing a constant water column height over several minutes. The stir bar rotation was set at 325 rpm. The dissolving solution was then heated to 100° C. The off-gas system was vented to relieve pressure (to zero the off-gas collection system), and a stopwatch was started as the first of four Al-1100 coupons was lowered into the solution.

[0038]To measure the gas generation rate, time versus water displacement was manually recorded until the coupon was visually observed to have dissolved completely. For each coupon dissolution, a gas sample was taken generally at 450 mL of off-gas volume

Example 2

[0041]Another series of experiments were performed to determine the impact of Fe on off-gas generation rates for uranium-aluminum dissolution at higher concentrations of Hg. A series of four 30 wt % U—Al alloy coupons, cut to 20×12×3 mm with a mass of 1.6-2.1 g, were prepared as described in Example 1.

[0042]Experiment 3 was conducted using a method analogous to that of Example 1 with a dissolving solution of 7 M HNO3, 0.1 M KF, 0.012 M Hg, and no Fe contamination. Hg was initially present in the solution, and the solution was heated to 100° C. before lowering the first coupon. The concentration of hydrogen in the off-gas was measured using gas chromatography.

[0043]Experiment 4 was conducted using a dissolving solution of 7 M HNO3, 0.1 M KF, 0.012 M Hg, and no Fe contamination. Approximately 130 mL of dissolving solution was weighed and added to the dissolver flask containing a Teflon™ stir bar. The solution containing all components except Hg was then heated to 100° C. A syrin