AHMED EXPERIMENTS ON HYGROSCOPIC AND INERT AEROSOL BEHAVIOR IN LWR CONTAINMENT CONDITIONS - EXPERIMENTAL RESULTS

Hygroscopic NaOH, CsI, CsOH and inert Ag aerosol behaviour at differen t temperatures and relative humidities (RH) has been studied in a well instrumented and controlled vessel of 1.81 m(3) total free volume. Ho mogeneous thermal-hydraulic conditions for aerosol measurement in the vessel were achieved. The aerosol number and mass concentration were m easured continuously during the experiments using a Condensation Nucle us Counter and a Tapered Element Oscillating Microbalance. The particl e size distribution and chemical composition in the test conditions we re measured by Berner low pressure impacters. In the case of NaOH the half life of the aerosol mass concentration was more than four times l onger at low RH (22%) as compared to high RH (96%). The half lives of the CsOH and CsI aerosols were only twice as long at low RH as compare d to high RH. Thus al high RH (96-97%) the half lives of CsOH and CsI were twice as long as the half life for the NaOH aerosol. The faster d ecay of the NaOH aerosol is due to the smaller density decrease of NaO H during water condensation. CsOH particles grew rapidly to their equi librium size at all humidities. The measured equilibrium size for CsOH aerosol agree well with the calculated particle size at different RHs . Experimental results were also compared with calculations obtained b y severe accident computer codes. These calculated results will be pre sented in a later paper. (C) 1997 Elsevier Science S.A.