Parametric explorative study of DEMO galleries pressurization in case of ex-vessel LOCA

Radioactive toxins confinement is a main safety function for fusion power plants, hence the importance of confinement design parameters optimization. Moving from this perspective, two Loss of Coolant Accidents (LOCAs) were analyzed: loss of water from Vacuum Vessel (VV) cooling loop and loss of cryogenic helium from Toroidal Field (TF) cooling loop. In fact these two LOCAs may result into galleries pressurization possibly jeopardizing this second confinement boundary for radioactive toxins. Publicly available ITER data (2000 baseline design) have been scaled to DEMO. A set of sensitivity simulation analyses are performed on main variables (coolant inventories, enthalpy, rooms volume, etc.) in order to derive resulting galleries pressure and temperature conditions. As first design feedback to keep gallery pressure below an assumed design pressure of 120 kPa, the VV H2O LOCA requires pressure reduction (e.g. increase expansion volume, inventory partitioning, sprinkler), while TF He LOCA requires releasable inventory to be limited at about 4.4 tons and Cryo-systems designed against Common Mode Failure (e.g. seismic and fire, quench valve failure). (C) 2017 The Authors. Published by Elsevier B.V.