Properties of brines formed by deliquescence of sea-salt aerosols

For long-term dry storage, most spent nuclear fuel in the United States is placed in welded 304 SS or 316 SS canisters that are stored within passively ventilated overpacks. As the canisters cool, sea-salt aerosols deposited on the canister surfaces will deliquesce to form potentially corrosive brines. We have used thermodynamic modeling to predict the chemical composition of the brines that form by deliquescence of sea-salt aerosols, and to estimate brine volumes and salt/brine volume ratios as a function of temperature and atmospheric relative humidity. We have also mixed representative brines and measured the physical and chemical properties of those brines over a range of temperatures. These data provide a matrix that can be used to predict the evolution of deliquescent brine properties over time on storage canister surfaces, as the canisters cool and surface relative humidity increases. Brine volumes and properties affect corrosion kinetics and damage distributions on the metal surface, and may offer important constraints on the expected rate and extent of corrosion and the timing of SCC crack initiation. The predicted brines do not consider reactions with atmospheric gases that are known to affect sea-salt particle and deliquescent brine compositions under field conditions. The potential effects of such reactions are discussed, and preliminary modeling and experimental data are presented.