Aerosol Behavior in a Steam-Air Environment

The behavior of aerosols assumed to be characteristic of those generated during accident sequences and released into containment is being studied in the Nuclear Safety Pilot Plant (NSPP). Observation on the behavior of U/sub 3/O/sub 8/ aerosol, Fe/sub 2/O/sub 3/ aerosol, concrete aerosol, and various mixtures of these aerosols in a dry air environment and in a steam-air environment within the NSPP vessel are reported. Under dry conditions, the aerosols are agglomerated in the form of branched chains; the aerodynamic mass median diameter (AMMD) of the U/sub 3/O/sub 8/, Fe/sub 2/O/sub 3/ and mixed U/sub 3/O/sub 8/-Fe/sub 2/O/sub 3/ aerosols ranged between 1.5 and 3..mu..m while that of the concrete aerosol was about 1 ..mu..m. A steam-air environment, which would be present in LWR containment during and following an accident, causes the U/sub 3/O/sub 8/, the Fe/sub 2/O/sub 3/, and mixed U/sub 3/O/sub 8/-Fe/sub 2/O/sub 3/ aerosols to behave differently from that in a dry atmosphere; the primary effect is an enhanced rate of removal of the aerosol from the vessel atmosphere. Steam does not have a significant effect on the removal rate of a concrete aerosol. Electron microscopy showed the agglomerated U/sub 3/O/sub 8/, Fe/sub 2/O/sub 3/, and mixed U/sub 3/O/sub 8/-Fe/sub 2/O/sub 3/ aerosols to be in the form of spherical clumps of particles differing from the intermingled branched chains observed in the dry air tests; the AMMD was in the range of 1 to 2 ..mu..m. Steam had a lesser influence on the physical shape of the concrete aerosol with the shape being intermediate between branched chain and spherical clumps. 9 figures