Aerosol deposition on the PHEBUS containment vessel wall
Congress title :CFA 2006 - 22ème Congrès Français sur les Aérosols
Congress town :Paris
Congress date :29/11/2006
In the FPT0 and FPT1 tests of the experimental programme PHEBUS FP, dedicated to the release, transport and deposition of fission products in a 1/5000 scale PWR facility under severe accident conditions, an unexpected amount of aerosol deposition on the containment vessel wall, according to the current modelling had been observed. This phenomenon was more recently observed in the FPT2 test. The present paper presents an interpretation of the diffusive deposition of aerosol particles, and a description of the turbulence near the wall. The so-called Landau and Levich hypothesis is used, stipulating that eddy viscosity and diffusivity are not killed inside the viscous sublayer but are progressively damped when nearing the wall. The model contains no additional parameter, other than the viscous sublayer thickness. The deposition velocity versus particle size follows a r2/3 or r3/4 law, to be compared to the current r1 law, allowing larger particle deposition. This model has been implemented in the severe accident code ASTEC V1. A simulation of the FPT1 and FPT2 tests has been performed and results are presented. This simple model, allowing to explain the deposition on the vessel walls observed in the PHEBUS tests, is general since it is only linked to the internal structure of the boundary layer.