Patent Number: 
Section: claims

1. An in-core instrumentation system for a reactor module, comprising:a reactor pressure vessel including a top end and a bottom end, an upper reactor head connected to the top end of the reactor pressure vessel, and a lower reactor head removably attached to the bottom end of the reactor pressure vessel;a containment vessel surrounding the entire reactor pressure vessel including a top end and a bottom end, a upper containment head connected to the top end of the containment vessel and a lower containment head removably connected to the bottom end of the containment vessel;a reactor core housed within the lower reactor head, wherein a plurality of control rods are inserted into the reactor core;a plurality of in-core instruments including a sensor and a measuring device, wherein the in-core instruments are located in guide tubes in the reactor core; andelectrical instrumentation cabling routed through the upper containment head of the containment vessel and the upper reactor head of the reactor pressure vessel to the in-core instruments located in the guide tubes in the reactor core, wherein disconnection and separation of the lower containment head from the bottom end of the containment vessel and disconnection and separation of the lower reactor head from the bottom end of the reactor pressure vessel retain the reactor core and the control rods within the reactor core within the lower reactor head while the guide tubes in the reactor core, lower reactor head, and lower containment head move down and out away from lower ends of the in-core instruments. 2. The in-core instrumentation system of claim 1, wherein the containment vessel is at least partially submerged in a surrounding pool of water, and wherein upon removing the lower reactor head from the bottom end of the reactor pressure vessel, the lower ends of the in-core instruments are exposed to the pool of water. 3. The in-core instrumentation system of claim 2, wherein the lower reactor head is removably attached to the bottom end of the reactor pressure vessel at a vessel flange, and wherein the exposed lower ends of the in-core instruments extend multiple meters below the vessel flange in the pool of water. 4. The in-core instrumentation system of claim 1, further comprising:instrumentation sheathing including a threaded portion extending from the containment vessel through the upper reactor head of the reactor pressure vessel, the electrical instrumentation cabling routed through the instrumentation sheathing to the in-core instruments; andone or more threaded gears configured to raise or lower the in-core instruments via a threaded engagement with the threaded portion of the instrumentation sheathing. 5. The in-core instrumentation system of claim 1, including a lower riser section integrally connected to the reactor core so both the lower riser section and the reactor core remain in the lower reactor head when the lower reactor head is removed from the bottom end of the reactor pressure vessel. 6. The in-core instrumentation system of claim 1, wherein the in-core instruments pass into the reactor pressure vessel through a sealed penetration located at the upper reactor head of the reactor pressure vessel. 7. The in-core instrumentation system of claim 6, wherein:the upper containment head remains environmentally sealed to the top end of the containment vessel while the lower containment head is disconnected and separated from the bottom end of the containment vessel and the lower reactor head is disconnected and separated from the bottom end of the reactor pressure vessel. 8. The in-core instrumentation system of claim 1, further comprising instrumentation sheathing configured to guide the in-core instruments into the reactor core. 9. An in-core instrumentation system for a reactor module, comprising:a reactor pressure vessel including a top end and a bottom end, an upper reactor head connected to the top end of the reactor pressure vessel, and a lower reactor head removably attached to the bottom end of the reactor pressure vessel;a reactor core housed within the lower reactor head, wherein control rods are insertable into the reactor core;a plurality of in-core instruments including one or more of a monitor, sensor, measuring device and detector extending down into the reactor core;instrumentation sheathing including a threaded portion extending through the upper reactor head of the reactor pressure vessel; andelectrical instrumentation cabling routed through the instrumentation sheathing connecting to the in-core instruments, wherein disconnection and separation of the lower reactor head from the bottom end of the reactor pressure vessel retain the reactor core and the control rods within the lower reactor head causing the reactor core and the lower reactor head to move down and out away from the in-core instruments. 10. The in-core instrumentation system of claim 9, including a containment vessel surrounding the entire reactor pressure vessel including a top end and a bottom end, a upper containment head connected to the top end of the containment vessel and a lower containment head removably connected to the bottom end of the containment vessel, wherein disconnection and separation of the lower containment head from the bottom end of the containment vessel and disconnection and separation of the lower reactor head from the bottom end of the reactor pressure vessel retain the reactor core within the lower reactor head causing the reactor core, lower reactor head, and lower containment head to move down and away from lower ends of the in-core instruments. 11. The in-core instrumentation system of claim 10, wherein:the lower reactor head is removably attached to the bottom end of the reactor pressure vessel at a first vessel flange; andthe lower containment head is removably attached to the bottom end of the containment vessel at a second vessel flange. 12. The in-core instrumentation system of claim 10, wherein lower ends of the in-core instruments extend out of the bottoms of upper portions of the containment vessel and the reactor pressure vessel when the lower containment head is disconnected and separated from the bottom end of the containment vessel and the lower reactor head is disconnected and separated from the bottom end of the reactor pressure vessel. 13. The in-core instrumentation system of claim 10, wherein an upper portion of the in-core instruments extends down from the upper containment head and through the upper reactor head. 14. The in-core instrumentation system of claim 9, including a lower riser section integrally connected to the reactor core so both the lower riser section and the reactor core remain in the lower reactor head when the lower reactor head is removed from the bottom end of the reactor pressure vessel. 15. The in-core instrumentation system of claim 9, wherein the instrumentation sheathing is configured to guide the in-core instruments into the reactor core.