Aerosol transport behavior in Fusion Demo reactor at hydrogen and dust explosion event depending on its safety system activation

Abstract

Safety and security for nuclear reactors including fusion reactors cannot be devalued especially for severe conditions such as the Fukushima-Daiichi nuclear accident, where lack of sufficient safety systems may cause irreversible breakage to the surrounding components. Safety analysis is also important in fusion DEMO reactor since its purpose requires higher fusion thermal energy and higher deuterium and tritium fuels inside the device. In recent research, it was notified that the DEMO fusion reactor requires precise caution with the choice of physical confinement of the device. Severe accident safety analysis using K-DEMO, the Korean fusion demonstration reactor design, at hydrogen and dust explosion in vacuum vessel event is presented. MELCOR code was chosen for the safety analysis as a fully integrated engineering-level code capable of modeling transient thermal hydraulic phenomena and radionuclide transport. Hydrogen explosion was selected for the analysis since the tritium and radioactive dust mobilized during the accident situations may lead to a hydrogen explosion. Also, lack of diesel AC power condition was assumed in purpose of comparison of aerosol release quantity into the environment depending on activation of safety systems in DEMO device. As a result, rapid pressurization caused rupture to the vacuum vessel confinement leading to higher quantity of aerosol release compared to ITER. Lack of diesel AC power condition resulted in higher peak pressure for port cell forming a direct penetration line into the gallery, where higher aerosol quantity was shown. Further analysis will be performed with consideration of different accident scenarios.