Simulations of plasma disruptions in ITER due to ingress of Be

摘要

ITER plasma will be surrounded by the first wall, which is mostly blankets made of beryllium (Be) and divertor plates made of tungsten (W). When the plasma is subjected to vertical displacement events (VDEs), it could come in contact with these first wall materials-be it in the upper dome during upward-moving VDEs or radial plasma movements and W divertor in the downward-moving VDEs. We investigate in this paper specifically the first case of plasma moving upwards, hitting the top dome and ejecting a small piece of Be. The piece of Be falls freely through the plasma, ablating as it moves down causing the plasma temperature to crash, although in a rather slow process of few hundred milliseconds, finally creating plasma disruption and generating a runway current. This whole scenario is simulated using the tokamak simulation code. We have also carried out preliminary simulation studies of possible mitigation of the runaways generated following the Be ingress through injection of deuterium pellets.