Simulation of sodium aerosol behaviour with CONTAIN-LMR code

摘要

The prediction of nuclear aerosols behavior associated with postulated accidents in Sodium-cooled Fast Reactors (SFRs) is necessary for the assessment of the radiological consequences of these events and to optimize filter systems and as well as design safety adapted reactor components. As a consequence of the high chemical reactivity of sodium with air and steam, it would undergo sodium oxidation within the containment atmosphere. The exothermic nature of the chemical reactions determines to a large extentextent both particle size distribution and population. As a result the radiological source term to the environment will then depend on in-containment Na-aerosol behavior. This paper is a continuation of investigating the ability of the CONTAIN-LMR code to reproduce physical and chemical processes during sodium fires in case of a severe accident in a SFR. CONTAIN-LMR is a computer code to analyze physical and chemical phenomena, including modeling of the sodium fire and aerosol behavior, in the reactor containment after a severe accident. The study focuses on a sensitivity analysis of CONTAIN-LMR calculations to various parameters used for the prediction of thermal and aerodynamic behavior of sodium aerosols generated during large scale sodium fires. For the validation experiments with pool-sodium fire performed in the FAUNA facility at the former FZK have been used. Calculation results show that particles shape and turbulence affect substantially aerosol evolution. Atmospheric parameter and aerosol mass concentrations predicted by CONTAIN-LMR agree reasonably well with experimental data. Deviations of predictions from measurements are discussed.