The behaviour of radioactive aerosols in the LWR containment during a hypothetical core melt accident is an important factor determining the possible releases of radioactive materials into the environment (Source Term). During leakage or containment failure the Source Term is directly related to the concentration of radioactive aerosols in the containment atmosphere.The aim of aerosol experiments in the VICTORIA facility is to validate the containment aerosol models used in the nuclear reactor accident codes. As a final goal we need to confirm that containment aerosol codes are able to calculate correctly the radioactive hygroscopic and non-hygroscopic aerosol behaviour in non-homogeneous multicompartment containments. It is possible to reach this goal by making experiments in the well controlled and instrumented model containment (VICTORIA multicompartment test facility, Loviisa Nuclear power station model containment with linear scaling 1:15). Earlier a research programme has been carried out in this facility to study the TH behaviour and hydrogen distribution in severe accident conditions.The results of these aerosol tests will extend our knowledge from single compartment test facilities to multicompartment non-homogeneous TH conditions. Large scale experiments have indicated that in the containment there are large local differences in the temperatures, flow fields and relative humidities. These differences affect significantly the containment aerosol behaviour.In the quantitative containment aerosol behavior tests at the VICTORIA facility state-of-the-art aerosol measurement systems are used. Aerosol number and mass concentration is measured continuously using Condensation Nucleus Counter (CNC) and Tapered Element Oscillating Microbalance (TEOM) mass monitor. Particle mass and chemical composition size distributions are determined by Berner Low Pressure Impactors (BLPI). Measurements have also been made with Electrical Low Pressure Impactor (ELPI), filter samplers and deposition coupons.At the moment 8 experiments have been performed (4 TH-tests and 4 aerosol tests). Experimental results will also be compared with different severe accident codes.The TH-data sampling system measures and records flow rates, pressures, temperatures and RH-values in the system. Temperatures are measured with T-type detectors. RH-values and temperatures are measured with several normal VAISALA humicap detectors and with two (upper and lower compartment) new heated type VAISALA dewpoint detectors. In these new detectors RH-sampling head is temperature controlled which prevents water condensation into the detector head even when RH is over 100%.In this presentation results obtained with NaOH and CsOH aerosols will be presented. During the first period hygroscopic aerosol was fed into the system. During the second period steam was fed into the lower compartment. The aerosol mass and number concentrations and the size distribution were measured as a function of time.