A compact Reactor Coolant System (RCS). With a “self-pressurization” concept there is no pressurizer, the reactor core exit flow is saturated water with minimal steam quality (less than 1%), RCS design pressure is reduced to ∼125 bar, and RCS hot leg is at 110 bar, saturation temperature 318 °C. Variable speed Reactor Coolant Pumps (RCP) are mounted at the Reactor Pressure Vessel (RPV) bottom circumference. Trip of the RCP, together with negative moderator void coefficient, ensures rapid negative reactivity insertion due to voiding at core exit, assisted by a safety boration to hot and/or cold shutdown condition. There is no need for mechanical control rods. The items indicated in the figure are: RPV, reactor pressure vessel; SG, steam generator; RC, reactor core; VS, RPV support; RCP, reactor coolant pumps; SGS, SG support.