Effects of steam upon LWR radionuclide release plumes

Analyses are presented for some implications of the large moisture contents of radionuclide plumes in LWR accident sequences involving containment failure due to steam overpressurization. Latent heat released by condensation can enhance plume buoyancy, especially when ambient humidity is high and temperature low. Another potentially-important effect, which has received little prior analysis, is turbulence-induced agglomeration in the containment blowdown jet, which can substantially increase particle size. For some sequences, calculations indicate that most of the released radionuclides can be swept up into droplets several tens of micrometers in diameter. Order-of-magnitude changes in aerosol deposition velocities and lung retention factors can result from this agglomeration