SMR-300 is a 300 MWe pressurized light water reactor that utilizes borated water in its reactor water (primary) side operating in a closed loop. The assemblage of the reactor, the steam generator, and the pressurizer, collectively referred to as the Reactor Cooling System (RCS), is configured to produce a gravity-driven circulation of the reactor coolant. To maximize the recirculation rate, the reactor is located substantially below-grade, and the steam generator is of the once-through genre and is located above-grade. The nuclear commodities in the SMR-300 are located deep in the ground which ensures that the background radiation dose from the nuclear plant at the site boundary will be very small.