AHMED experiments on hygroscopic and inert aerosol behaviour in LWR containment conditions: experimental results |
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Authors: | J.M Mä kynen,J.K Jokiniemi,P.P Ahonen,E.I Kauppinen,R Zilliacus |
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Affiliation: | aVTT Energy Aerosol Technology Group, P.O. Box 1401, Biologinkuja 7, Espoo, FIN-02044, Finland;bVTT Chemical Technology, Aerosol Technology Group, P.O. Box 1401, FIN-02044 VTT, Finland;cVTT Chemical Technology, P.O.Box 1404, FIN-02044 VTT, Finland |
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Abstract: | Hygroscopic NaOH, CsI, CsOH and inert Ag aerosol behaviour at different temperatures and relative humidities (RH) has been studied in a well instrumented and controlled vessel of 1.81 m3 total free volume. Homogeneous thermal-hydraulic conditions for aerosol measurement in the vessel were achieved. The aerosol number and mass concentration were measured continuously during the experiments using a Condensation Nucleus Counter and a Tapered Element Oscillating Microbalance. The particle size distribution and chemical composition in the test conditions were measured by Berner low pressure impactors. In the case of NaOH the half life of the aerosol mass concentration was more than four times longer 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 compared to high RH. Thus at 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 decay of the NaOH aerosol is due to the smaller density decrease of NaOH during water condensation. CsOH particles grew rapidly to their equilibrium 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 by severe accident computer codes. These calculated results will be presented in a later paper. |
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Keywords: | Abbreviations: AMMD, aerodynamic mass median diameter APS, aerodynamic particle sizer BLPI, Berner low pressure impactor CNC, condensation nucleus counter DMA, differential electrical mobility analyzer GSD, geometrical standard deviation ICP-MS, inductively coupled plasma mass spectrometry MCA, multichannel accumulator RH, relative humidity RTD, resistance temperature detector TEOM, tapered element oscillating microbalance T-H, thermal hydraulic |
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