Effect of Tortuosity on Retention of Aerosol Particles Through Small Curved Concrete Cracks

In the case of incomplete failure of concrete containment, penetration of aerosol through concrete cracks is an important influence factor for the radiological assessment released from concrete containment. The small concrete cracks with curved flow channel have good retention effect on the aerosol penetration. However, a conservative method, aerosol assumed as pure gas leakage without any retention, is used for source term evaluation for nuclear power plant, due to the lack of the knowledge of the aerosol retention with concrete cracks. In this paper, one artificial straight crack and three curved cracks with tortuosity of 1.09, 1.13 and 1.36 formed by tensile shear, are studied in the airflow characterization tests and aerosol penetration tests. The flow characteristic height of concrete crack is obtained by the Suzuki flow formula to solve the problem that the tiny height of concrete crack cannot be measured directly. Compared with the straight crack, increasing the tortuosity is of great significance to the penetration of submicron particles. Larger particle diameter and higher pressure-difference will reduce the penetration of particles due to the increase of particle inertia. Based on the mechanism of inertial deposition, an empirical correlation expressed with the leakage flow rate and tortuosity has been proposed to evaluate the particle penetration, which is validated with the results of aerosol retention inside concrete crack with a tortuosity of 1.27.