Loss of Coolant Accident (LOCA) analysis has been performed for the ARIES-RS Fusion Power Plant. LOCA occurs when one or more supply tubes outside the reactor are damaged or ruptured preventing the coolant from reaching the first wall or plasma facing components. For ARIES-RS, it is assumed that the plasma is immediately quenched and the chamber components begin to increase in temperature due to the generating afterheat. This analysis examines the thermal behavior of the in-vessel components to determine the maximum temperature reached and addresses various schemes of afterheat removal.

The thermal behavior of the reactor following a LOCA is simulated using a transient two-dimensional finite element model. Several cases have been considered to investigate the effect of using different shielding materials (Tenelon steel and vanadium) which have different afterheat characteristics, on the thermal response of ARIES-RS in-vessel components, in particular, the first wall.

Several boundary conditions were assumed in this study. For instance, the toroidal field (TF) magnets are perfectly thermally insulated from the rest of the reactor components and are not used as a heat sink. The only heat sink exists outside the vacuum vessel to provide heat conduction through tortuous path to the reactor base, support structure and access ports between coils. Thermal radiation is the only mode of heat transport across the assembly gaps between various in-vessel component. Thermal radiation and heat conduction are assumed to occur between the internal surfaces of the components. Based on these assumptions, the analysis shows that the outboard first wall will reach a maximum temperature of 1174 C for a vanadium first wall and will remain at a temperature higher than 1100 C for about 10 hours. This means that a passive afterheat removal system should be incorporated in the design to protect the ARIES-RS plant in-vessel components from being damaged case of a loss of coolant accident. Such a passive afterheat removal system can be provided by means of a closed Li loop which convicts heat from the front of the chamber components to the back, but can only do this if the TF magnets are de-energized.