Numerical simulations of radioactive dust particle releases during a Loss Of Vacuum Accident in a nuclear fusion reactor

Abstract

A loss of vacuum accident is one of the possible phenomena that may be triggered by off-normal events in nuclear fusion reactors, such as disruptions. After a break of the isolation system and the formation of a penetration line, the air flows inside the Tokamak due to the large pressure gradient, resuspending toxic and radioactive dust. At the end of the event, an over pressurisation of the vacuum vessel may occur due to inertia effects and the heating of the air through the first wall, that may have still high temperatures. Thus, air will flow from the inside to the outside, dragging the dust particles and involving a radiological and toxic release. This work aims to provide, by numerical simulations, an analysis of particle release as a function of main parameters that characterise the release: diameter of the penetration line, wall temperature and particle sizes. The numerical simulation is based in a one-way coupling. Starting from the simulation of the velocity, pressure and density fields of the continuous phase(air) by a monophasic compressible CFD model, the motion of the particles inside the vessel is simulated.