Patent Number: 
Section: abstract

A pressurized water nuclear reactor (PWR) includes a once through steam generator (OTSG) disposed in a generally cylindrical pressure vessel and a divider plate spaced apart from the open end of a central riser. A sealing portion of the pressure vessel and the divider plate define an integral pressurizer volume that is separated by the divider plate from the remaining interior volume of the pressure vessel. An internal control rod drive mechanism (CRDM) has all mechanical and electromagnetomotive components including at least a motor and a lead screw disposed inside the pressure vessel. Optionally CRDM units are staggered at two or more different levels such that no two neighboring CRDM units are at the same level. Internal primary coolant pumps have all mechanical and electromagnetomotive components including at least a motor and at least one impeller disposed inside the pressure vessel. Optionally, the pumps and/or CRDM are arranged below the OTSG.