Patent Number: 
Section: claims

1. A nuclear island comprising:a nuclear reactor including a nuclear reactor core comprising fissile material disposed in a reactor pressure vessel;an emergency core cooling (ECC) system connected to the reactor pressure vessel through an ECC pressure vessel feedthrough;a reactor coolant inventory and purification system (RCIPS) connected to the reactor pressure vessel to inject coolant into the reactor pressure vessel through a make-up line connected to a make-up line pressure vessel feedthrough and to extract coolant from the reactor pressure vessel through a let-down line connected to a let-down line pressure vessel feedthrough; andan integral isolation valve (IIV) system including:a passive IIV comprising a check valve built into a forged flange that is connected directly to the ECC pressure vessel feedthrough and a corresponding ECC system line,a passive IIV comprising a check valve built into a forged flange that is connected directly to the make-up line pressure vessel feedthrough and the make-up line, andan active IIV comprising an active valve built into a forged flange that is connected directly to the let-down line pressure vessel feedthrough and the let-down line,wherein the passive and active IIVs each have an outer diameter along its entire length that is greater than an outer diameter of the corresponding ECC system line, make-up line, and let-down line to which it is connected. 2. The nuclear island of claim 1 further comprising:a residual heat removal (RHR) system having an RHR inlet line connected to the reactor pressure vessel through an RHR pressure vessel inlet feedthrough and an RHR outlet line connected to the reactor pressure vessel through an RHR pressure vessel outlet feedthrough;wherein the IIV system further includes:a passive IIV comprising a check valve built into a forged flange that is connected directly to the RHR pressure vessel outlet feedthrough and the RHR outline line, andan active IIV comprising an active valve built into a forged flange that is connected directly to the RHR pressure vessel inlet feedthrough and the RHR inlet line,wherein the passive and active IIVs each have an outer diameter along its entire length that is greater than an outer diameter of the corresponding RHR outlet line and RHR inlet line, respectively, to which it is connected. 3. The nuclear island of claim 2 wherein the RHR system comprises an air- or water-cooled RHR heat exchanger. 4. The nuclear island of claim 2 further comprising:a pressure sensor disposed in the reactor pressure vessel and configured to sense reactor coolant pressure; anda reactor control system configured to close the active IIV connected directly to the RHR pressure vessel inlet feedthrough in response to the reactor coolant pressure sensed by the pressure sensor exceeding a threshold pressure. 5. The nuclear island of claim 1 further comprising:a level sensor disposed in the reactor pressure vessel and configured to sense reactor coolant level;a reactor control system configured to close the active IIV connected directly to the letdown line pressure vessel feedthrough in response to the reactor coolant level sensed by the pressure sensor falling below a threshold reactor coolant level. 6. A nuclear island comprising:a nuclear reactor including a nuclear reactor core comprising fissile material disposed in a reactor pressure vessel that has a plurality of pressure vessel penetrations that exclusively carry flow into the reactor pressure vessel and at least one pressure vessel penetration that carries flow out of the reactor pressure vessel; andan integral isolation valve (IIV) system including:a plurality of passive IIVs each comprising a check valve built into a forged flange and not including an actuator, andone or more active IIVs each comprising an active valve built into a forged flange and including an actuator,wherein:each pressure vessel penetration that exclusively carries flow into the reactor pressure vessel is protected by a passive IIV whose forged flange is directly connected to the corresponding pressure vessel penetration and a corresponding line, andeach pressure vessel penetration that carries flow out of the reactor pressure vessel is protected by an active IIV whose forged flange is directly connected to the corresponding pressure vessel penetration and a corresponding line,wherein the passive and active IIVs each have an outer diameter along its entire length that is greater than an outer diameter of the corresponding line to which it is connected. 7. The nuclear island of claim 6 wherein each pressure vessel penetration that carries flow out of the reactor pressure vessel exclusively carries flow out of the reactor pressure vessel. 8. The nuclear island of claim 6 wherein each active IIV further includes a manual backup for the actuator. 9. The nuclear island of claim 6 further comprising:an emergency core cooling (ECC) system connected to the reactor pressure vessel through a pressure vessel penetration that exclusively carries flow into the reactor pressure vessel and is protected by a passive IIV whose forged flange is directly connected to the pressure vessel penetration and a corresponding ECC system line,wherein the passive IIV has an outer diameter that is greater along its entire length than an outer diameter of the corresponding ECC system line to which it is connected. 10. The nuclear island of claim 6 further comprising:a reactor coolant inventory and purification system (RCIPS) connected to the reactor pressure vessel to inject coolant into the reactor pressure vessel through a vessel penetration that exclusively carries flow into the reactor pressure vessel and is protected by a passive IIV whose forged flange is directly connected to the pressure vessel penetration and a corresponding RCIPS line,wherein the passive IIV has an outer diameter that is great along its entire length than an outer diameter of the corresponding RCIPS line to which it is connected. 11. The nuclear island of claim 10 wherein the RCIPS is further connected to the reactor pressure vessel to extract coolant from the reactor pressure vessel through a pressure vessel penetration that exclusively carries flow out of the reactor pressure vessel and is protected by an active IIV whose forged flange is directly connected to the pressure vessel penetration and a corresponding RCIPS line,wherein the active IIV has an outer diameter that is greater along its entire length than an outer diameter of the corresponding RCIPS line to which it is connected. 12. The nuclear island of claim 11 further comprising:a residual heat removal (RHR) system having:an inlet line connected to the reactor pressure vessel through a pressure vessel penetration that exclusively carries flow out of the reactor pressure vessel and is protected by an active IIV whose forged flange is directly connected to the pressure vessel penetration and the inlet line, andan outlet line connected to the reactor pressure vessel through a pressure vessel penetration that exclusively carries flow into the reactor pressure vessel and is protected by a passive IIV whose forged flange is directly connected to the pressure vessel penetration and the outlet line,wherein the passive and active IIVs each have an outer diameter that is greater along its entire length than an outer diameter of the corresponding outlet line and inlet line, respectively, to which it is connected. 13. The nuclear island of claim 6 further comprising:a residual heat removal (RHR) system having:an inlet line connected to the reactor pressure vessel through a pressure vessel penetration that exclusively carries flow out of the reactor pressure vessel and is protected by an active IIV whose forged flange is directly connected to the pressure vessel penetration the inlet line, andan outlet line connected to the reactor pressure vessel through a pressure vessel penetration that exclusively carries flow into the nuclear reactor pressure vessel and is protected by a passive IIV whose forged flange is directly connected to the pressure vessel penetration and the outlet line,wherein the active and passive IIVs each have an outer diameter that is greater along its entire length than an outer diameter of the corresponding inlet line and outlet line to which it is connected. 14. The nuclear island of claim 6 wherein the check valve of each passive IIV admits flow at above a threshold pressure into the reactor pressure vessel, while blocking flow otherwise. 15. The nuclear island of claim 6 wherein the active valve of each active IIV is a normally closed valve. 16. The nuclear island of claim 6 wherein the active valve of at least one active IIV is configured to be closed by reactor coolant pressure upon loss of actuator power. 17. A nuclear island comprising:a nuclear reactor including a nuclear reactor core comprising fissile material disposed in a reactor pressure vessel;a plurality of auxiliary systems in fluid communication with the reactor pressure vessel via pressure vessel penetrations wherein each said pressure vessel penetration is either a fluid inlet pressure vessel penetration carrying fluid into the reactor pressure vessel or a fluid outlet pressure vessel penetration carrying fluid out of the reactor pressure vessel; andan integral isolation valve (IIV) system including:at least one passive IIV comprising a check valve built into a forged flange and not including an actuator, andat least one active IIV comprising an active valve built into a forged flange and including an actuator,wherein:each fluid inlet pressure vessel penetration is protected by a passive IIV whose forged flange is directly connected to the pressure vessel penetration and a corresponding line, andeach fluid outlet pressure vessel penetration is protected by an active IIV whose forged flange is directly connected to the pressure vessel penetration and a corresponding line,wherein the passive and active IIVs each have an outer diameter that is greater along its entire length than an outer diameter of the corresponding line to which it is connected. 18. The nuclear island of claim 17 wherein the plurality of auxiliary systems includes an emergency core cooling (ECC) system and a reactor coolant inventory and purification system (RCIPS). 19. The nuclear island of claim 18 wherein the plurality of auxiliary systems further includes a residual heat removal (RHR) system.