A low pressure water reactor (LPWR) and a method for controlling a LPWR are proposed. The LPWR comprises a reactor vessel with an internal cavity comprising a primary coolant, a riser tube, and a core located below ground level with 6-15 bars atmosphere pressure; a steam drum connected to the riser tube and located at ground level at a pressure of 1 -10 bars absolute; a water storage tank to store borated water; a passive injection system to inject the borated water from the water storage tank into the vessel; and low pressure steam turbines to generate power at a pressure of 1-10 bars atmosphere. The vessel heats water up to a certain temperature and the riser tube converts the heated water to steam, which is further delivered to the turbine(s). The conversion creates a difference in a primary coolant density that initiates a density-driven natural circulation of the primary coolant in the riser tube, downcomer, steam drum and core.