Radioactive Waste Foams: Formation and Mitigation

Foaming has been observed during the evaporation of simulated radioactive wastes and is typically enhanced by finely divided solid particles. A maximum in foaminess as a function of the total solid concentration is observed. The increase in foaminess is due to the structural stabilization by the particles in the foam lamella and the decrease in foaminess is due to clustering of the particles in the bulk. In this paper, we study the effects of various parameters such as heating flux, low pressure, normal paraffin hydrocarbons (NPH), tributyl phosphate (TBP), surfactants, and commercially available antifoams on foaminess during the evaporation of the simulant. The increase in flux at atmospheric pressure increases foaminess while low pressure decreases foaminess. The addition of NPH increases the foaminess while TBP reduces foaminess (at the maximum in foaminess with respect to the baseline case containing neither, as both NPH and TBP modify particle wettability). The surfactant (when added in small amounts) reduces foaminess, while larger amounts increase foaminess by a factor of 4. The antifoam DOW 1520 US is inefficient in reducing foaminess (400% vol to 200% vol) while Q2-3183 A is able to reduce foaminess by a factor of 4 (400% vol to 120% vol) at the maximum in foaminess.