Theoretical simulation on evolution of suspended sodium combustion aerosols characteristics in a closed chamber

In the unlikely event of core disruptive accident in sodium cooled fast reactors, the reactor containment building would be bottled up with sodium and fission product aerosols. The behavior of these aerosols is crucial to estimate the in-containment source term as a part of nuclear reactor safety analysis. In this work, the evolution of sodium aerosol characteristics (mass concentration and size) is simulated using HAARM-S code. The code is based on the method of moments to solve the integro-differential equation. The code is updated to FORTRAN-77 and run in Microsoft FORTRAN PowerStation 4.0 (on Desktop). The sodium aerosol characteristics simulated by HAARM-S code are compared with the measured values at Aerosol Test Facility. The maximum deviation between measured and simulated mass concentrations is 30% at initial period (up to 60 min) and around 50% in the later period. In addition, the influence of humidity on aerosol size growth for two different aerosol mass concentrations is studied. The measured and simulated growth factors of aerosol size (ratio of saturated size to initial size) are found to be matched at reasonable extent. Since sodium is highly reactive with atmospheric constituents, the aerosol growth factor depends on the hygroscopic growth, chemical transformation and density variations besides coagulation. Further, there is a scope for the improvement of the code to estimate the aerosol dynamics in confined environment. (c) 2021 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

In the event of a core disruptive accident in sodium cooled fast reactors, understanding the behavior of sodium and fission product aerosols is crucial for nuclear reactor safety analysis. In this study, the evolution of sodium aerosol characteristics is simulated using the HAARM-S code, which is based on the method of moments. The code is updated to FORTRAN-77 and compared with measured values at an Aerosol Test Facility. The results show a maximum deviation of 30% between measured and simulated mass concentrations in the initial period, and around 50% in the later period. The influence of humidity on aerosol size growth is also studied.