Benchmark of the GETTHEM Vacuum Vessel Pressure Suppression System (VVPSS) model for a helium-cooled EU DEMO blanket

In the nuclear field, the correct evaluation of the effects of design-basis accidents is fundamental to correctly design the countermeasures needed to preserve the integrity of the containment barriers and to confine the ra-dioactive material. Therefore, both in fission and in fusion, notwithstanding the different amounts of radioac-tive materials, the availability of models that can predict the accidental transients is crucial. Here we describe the model recently developed to analyse an in-vessel Loss-Of-Coolant-Accident in the EU DEMO fusion reactor, and implemented in the GETTHEM code. In particular, we focus on the release of coolant inside the Vacuum Vessel (VV) following a break in the breeding blanket cooling loop, considering a helium-cooled blanket solution. The model of the VV pressure suppression system is calibrated and bench-marked exploiting results from the validated CONSEN code by ENEA.