Reaction rates and prediction of thermal instability during aluminum alloy 6061 dissolution

ABSTRACT

Chemical kinetics of dissolution of aluminum alloy 6061 was investigated for the processing of Pu-238 for deep space missions. The rate of dissolution was measured by the heat release and appeared to be controlled by the rate of release of Al(OH)₄⁻ from the metal surface. Rates of reaction were measured from 273 to 365 K, giving an activation energy of 72 ± 13 kJ⋅(mol Al)⁻¹ and a pre-exponential factor of 5 ± 3 × 10⁹ dm³mol⁻¹min⁻¹. Minor alloying elements did not appear to affect the reaction kinetics. The average heat of dissolution was −360 ± 70 kJ⋅(mol NaAlO₂)⁻¹. When extrapolated to an infinitely dilute solution of aluminum, kJ⋅(mol NaAlO₂)⁻¹.

KEYWORDS:

• Aluminum alloy 6061 dissolution
• kinetics of aluminum dissolution
• neptunium target cladding dissolution
• plutonium-238 production

Funding

This work was supported by the Pu-238 Production Project and UT-Battelle, under Contract DEAC05-00OR22725 with the US Department of Energy.

Notes

1. The MatLab code can be obtained from the corresponding author.

2. Higher uncertainties were observed at lower reaction temperatures.

3. Aluminum pieces were added one by one into the same reaction vessel. The number in brackets refers to the number of the piece added to the vessel. Uncertainty reflects variability in added mass.

4. NaOH (10 M) was metered into the reaction vessel.

5. The sample heated to greater than 373K and so heat losses could not be calculated.

6. measured by grab sample.

Additional information

Funding

This work was supported by the Pu-238 Production Project and UT-Battelle, under Contract DEAC05-00OR22725 with the US Department of Energy.