Aerosol resuspension by highly transient containment flow

Within the course of a hypothetical core melt accident in a light water reactor, several physical processes lead to the formation of active and non active aerosols. During the accident sequence, a considerable part of the aerosols is deposed within the containment. Transient flow situations during the late phase of an accident (blow-by, H2-explosions, etc.) can resuspend primarily deposed aerosols to a considerable extent - an effect, which is not yet well understood and not yet taken into account within any containment simulation code. Therefore, the aerosol resuspension in transient flows by means of highly resolving, laser-optical techniques is to be investigated in experimental studies.

To investigate the resuspension of deposed particles by transient flow phenomena, a windtunnel has been employed in order to generate flow waves on a high level of reproducibility (cf. fig. 1). An expansion wave is transmitted to the optically accessible test section with the particle deposition plate, in order to identify the key-parameters of particle resuspension. The different geometric configurations of the aerosol deposition plate which are tested are shown in fig. 2. Three optical methods are to be employed:

• laser diffraction method for the time resolved detection of the particle density and particle size distribution within the flow,
• scattering method for the time resolved measurement of the total mass of deposit and hence the resuspension rate and
• high speed particle tracking for the visualisation of particle motion and velocity by the evaluation with the crosscorrelation.

Simultaneous application of these complementary methods, together with balancing techniques delivers comprehensive information on the whole process.

Accompanying the experimental results a theoretical model for a numerical code is developed that applies to a quantitative and time dependent aerosol resuspension.