The CAREM nuclear power plant design is based on a light water integrated reactor. The whole high — energy primary system, core, steam generators, primary coolant and steam dome, is contained inside a single pressure vessel (Fig. XIV-1).

For low power modules (below 150 MW(e)), the flow rate in the reactor primary systems is achieved by natural circulation. Figure XIV-1 shows a diagram of the natural circulation of the coolant in the primary system. Water enters the core from the lower plenum. After it’s heated the coolant exits the core and flows up through the riser to the upper dome. In the upper part, water leaves the riser through lateral windows to the external region. Then it flows down through modular steam generators, decreasing its enthalpy. Finally, the coolant exits the steam generators and flows down through the down-comer to the lower plenum, closing the circuit. The driving forces obtained by the differences in the density along the circuit are balanced by the friction and form losses, producing the adequate flow rate in the core in order to have the sufficient thermal margin to critical phenomena. Reactor coolant natural circulation is produced by the location of the steam generators above the core.