Nitric Acid Dissolution of Uranium-Aluminum Alloy

Abstract

Operated for the Atomic Energy Commission by the General Electric Company under Contract # W-31-109-Eng-52 REST: .ED DATA This document contains RestricteMMtta as defined in the Atonaic Energy Act of 1946, Its transmitta|fflj8|he disclosure of its contents in any naanner to an unauthorizqmBferson is prohibited.

Effects of increasing the initial nitric acid concentration from a maximum of 7.5 to 8.5 M during the dissolution of aluminum spent nuclear fuel

“…Burns and Holm performed a series of experiments in which a U-Al alloy containing 92.5 wt % Al and 7.5 wt % U was dissolved in 0 to 9 M HNO3 using 0.002 M Hg at the boiling points of the solutions. 4 Results obtained from these experiments confirmed expectations that during dissolution, the U-Al alloy behaved much like Al alone.…”

“…This conclusion is based on the observation by Burns and Holm that during the dissolution of U-Al alloys with low concentrations of U, the alloys behaved much like Al alone. 4 Less rapid dissolution rates are consistent with lower offgas generation rates; 6 therefore, as the HNO3 concentration increases beyond the value where the maximum rate is observed during the dissolution of an Al-1100 alloy coupon (or HFIR and MTR fuel), the offgas generation rate will decrease. The flowsheet development work for the dissolution of HFIR and MTR fuels shows that a decrease in the offgas generation rate generally results in a decrease in the H2 generation rate.…”

“…The declining dissolution rates continue as the HNO3 concentration increases and the solution becomes more highly oxidizing leading to the passivation of the surface by the acid. 4,5 The maximum dissolution rate of Al (and U-Al alloys) occurs at a HNO3 concentration which is a function of the Hg and Al(NO3)3 concentrations in the dissolving solution. Other factors such as the metallurgical treatment of the alloys can also influence the concentration where the maximum rate occurs.…”

“…Other factors such as the metallurgical treatment of the alloys can also influence the concentration where the maximum rate occurs. 4,5 In the experiments performed by Burns and Holm (Figure 1), a Hg concentration of 0.002 M was used during the dissolutions of U-Al alloy wafers cut from fuel elements. In the absence of Al(NO3)3, the maximum dissolution rate occurred at nominally 4 M HNO3 and began to decrease with increasing acid concentrations.…”