Patent Number: 
Section: claims

1. An apparatus comprising:a pressurized water reactor (PWR) including a nuclear reactor core comprising fissile material disposed in a reactor pressure vessel also containing primary coolant water;a pressurizer integral with or operatively connected with the reactor pressure vessel and configured to control pressure in the reactor pressure vessel; anda decay heat removal system including a pressurized passive condenser and a pump driven by a turbine in which steam from the pressurizer drives the turbine and exhausts into the pressurized passive condenser and the pump is connected to suction water from the pressurized passive condenser into the reactor pressure vessel. 2. The apparatus of claim 1 further comprising:a pressurizer power operated relief valve configured to control discharge of steam bypassing the turbine into the pressurized passive condenser to control pressure in the pressurizer. 3. The apparatus of claim 1 further comprising:a pressurizer block valve configured to activate the decay heat removal system by opening to admit steam from the pressurizer to the turbine. 4. The apparatus of claim 1 further comprising:a pressurizer block valve configured to activate the decay heat removal system by opening to admit steam from the pressurizer to the turbine;a pressurizer power operated relief valve downstream of the pressurizer block valve and configured to control discharge of steam into the pressurized passive condenser to control pressure in the pressurizer; anda steam turbine control valve downstream of the pressurizer block valve and configured to throttle steam into the turbine. 5. The apparatus of claim 1 further comprising:a common shaft, the pump and the turbine being mounted on the common shaft so that the shaft provides direct mechanical coupling via which the turbine drives the pump. 6. The apparatus of claim 1 wherein the pressurizer comprises an integral pressurizer. 7. The apparatus of claim 1 further comprising:a steam generator configured to heat sink the PWR by flow of secondary coolant water in thermal communication with the primary coolant water; anda pressurizer block valve configured to activate the decay heat removal system in response to a loss of heat sinking by the steam generator by opening to admit steam from the pressurizer to the turbine. 8. The apparatus of claim 7 wherein the steam generator comprises an internal steam generator disposed inside the reactor pressure vessel.