Patent Number: 
Section: claims

1. A decay heat removal system operating in conjunction with a pressurized water reactor (PWR) including a nuclear reactor core comprising fissile material disposed in a reactor pressure vessel also containing primary coolant water and a pressurizer integral with or operatively connected with the reactor pressure vessel and configured to control pressure in the reactor pressure vessel, the decay heat removal system comprising:a pressurized passive condenser;a turbine;a pump driven by the turbine and connected to suction water from at least one water source into the reactor pressure vessel; andsteam piping configured to deliver steam from the pressurizer to the turbine to operate the pump and to discharge the delivered steam into the pressurized passive condenser. 2. The decay heat removal system 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. 3. The decay heat removal system of claim 1 wherein the at least one water source includes a refueling water storage tank (RWST) disposed with the PWR in a radiological containment structure. 4. The decay heat removal system of claim 1 wherein the at least one water source includes the pressurized passive condenser. 5. The decay heat removal system of claim 1 wherein the at least one water source includes (1) a refueling water storage tank (RWST) disposed with the PWR in a radiological containment structure and (2) the pressurized passive condenser. 6. The decay heat removal system of claim 1 wherein the steam piping includes a pressurizer power operated relief valve configured to control discharge of a portion of the delivered steam bypassing the turbine into the pressurized passive condenser to control pressure in the pressurizer. 7. The decay heat removal system of claim 1 wherein the steam piping includes: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. 8. The decay heat removal system of claim 1, wherein the pressurizer comprises an integral pressurizer. 9. The decay heat removal system 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. 10. The decay heat removal system of claim 9 wherein the steam generator comprises an internal steam generator disposed inside the reactor pressure vessel.