Safety is one of the most important aspect in the design of the EU DEMO fusion reactor, therefore it is fundamental to study the Design-Basis Accidents (DBA) already in its pre-conceptual design phase. The in-vessel Loss Of Coolant Accident (LOCA) is one of the most relevant DBA, since it has the potential to seriously damage the components inside the vacuum vessel. Usually this kind of transients are modeled with system-level codes, which are typically employed to analyze the behavior of the entire system and for this reason are based on a lumped approach. However they are unable to evaluate localized quantities such as pressure peaks, which cannot be neglected during this kind of accidents since they can directly lead to a failure.