MARS - A competitive PWR based completely on passive safety systems

The MARS nuclear power plant is a cheap, simple, extremely safe PWR plant incorporating all main well-proven features of a “traditional” PWR plant. A production plant is made of medium-power modules: each reactor module may produce up to some 1000 MWth; the design here presented refers to a size of 600 MWth. The whole design is strongly simplified, thanks to safety characteristics based on simple, almost completely static and exclusively passive-type emergency systems. The probability of core integrity failure is a vanishing event (according to rigorous PRA evaluations, core damage probability in the range of 1E-7 event/year). The core cooling system includes one loop only, with recirculation-type steam generator; during normal operation, the primary coolant is pumped in the reactor vessel and in the primary loop, while, in emergency conditions, the coolant flow in the core is completely guaranteed through an independent cooling system, transferring heat to the external atmosphere with natural circulation and relying on only static components and one non-static, passive component (check valves, 400% redundant on two independent cooling trains). In the paper the peculiar design features and the experimental activities performed to support the design of Mars Reactor are presented.