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National Technical University of Athens
School of Mechanical Engineering
Nuclear Engineering Department

Nuclear Engineering and Design 238 (2008) 3370-3378

A simple mechanistic model for particle penetration and plugging in tubes and cracks

D. Mitrakos, S.Chatzidakis
Demokritos National Centre for Scientific Research, Institute of Nuclear Technology and Radiation Protection
Faculty of Mechanical Engineering, National Technical University of Athens
E.P. Hinis
Faculty of Mechanical Engineering, National Technical University of Athens
L.E. Herranz
CIEMAT, Nuclear Safety Unit
F.Parozzi
Department of Generation Systems, CESI RICERCA
C. Housiadas
Demokritos National Centre for Scientific Research, Institute of Nuclear Technology and Radiation Protection

In the course of a severe accident, some nuclear aerosols may be released to the environment through penetrating the containment concrete cracks, even if a catastrophic failure of the containment does not occur. There is experimental and theoretical evidence of strong retention of aerosol particles in the cracks that act as a filter. In this work a Eulerian model is developed based on the numerical solution of the one- dimensional aerosol transport equation. Plug formation is accommodated by allowing the crack diameter to change with time, based on the volume of the deposited mass. Brownian diffusion, gravitational settling and turbulence-driven deposition are considered as the removal mechanisms of the particles along the leak path. The model is verified against analytical solutions and validated by comparing with early as well as recent experimental data. It is concluded that a one-dimensional model of aerosol flow through a hydraulically equivalent leaking duct can simulate with enough accuracy aerosol transport in cracks, so that it may be an appropriate option for a large system code like ASTEC.

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