In the present talk, we show the ongoing studies carried out to develop a concept for a future DEMOnstration fusion power plant (DEMO). In collaboration with the DEMO team and inside the EUROfusion program, a possible relevant DEMO scenario has been selected and is currently used to perform numerical simulations. With the nonlinear magnetohydrodynamic (MHD) code JOREK, we aim to address different questions that are important for the design of the machine. In particular, we want to estimate (through 3D simulations) the maximum global mechanical forces that would be applied to the first wall in the event of a loss of control, that is, in presence of an unmitigated vertical displacement event (UVDE). Parallelly (in 2D simulation) we want to develop an efficient mitigation disruption scheme and estimate the vertical wall force reduction by injecting shattered pellet (SPI). This, in turn, leads to the generation of runaway-electron (RE) carriers of relativistic energy. It is then important to study the RE beam termination to assess the efficiency of the sacrificial limiters in protecting the conducting structures from excessive REs loads.