ALTERNATIVE REAGENT TO MERCURIC NITRATE CATALYST FOR DISSOLUTION OF ALUMINUM-CLAD NUCLEAR-FUELS IN NITRIC-ACID

A substitute additive, HBF4, has been discovered that will replace Hg( NO3)(2) catalyst for dissolving aluminium spent nuclear fuels in nitri c acid for recovery of usable materials. The catalyst or substitute is necessary to penetrate a protective oxide film that continuously form s on the,Al surface in the oxidizing acid, A penetration rate of alloy Al-6061 T6 of 40 mg/cm(2)-h can be achieved in a continuous dissoluti on process at 100 degrees C using a dissolvent of 0.15 M HBF4 in 7 M H NO3 that achieves a steady-state composition of 1.0 M Al3+ and 3.3 M H NO3, while maintaining a corrosion rate of a type 304L stainless steel dissolver vessel of 0.015 mm/mo, The penetration rate of aluminum is correlated with the equilibrium concentration of MF in the system. The postulated mechanism involves dissolution of the alumina film by appr oximately 0.006 M HF in equilibrium with the HBF4 and completed alumin um fluoride species in nitric acid, which provide a large semi-buffere d supply of HF. This allows. the HNO; to attack the aluminum metal. Th e small concentration of HF does not compete favorably with HNO3; for reaction with and consumption by Al.