Patent Number: 
Section: claims

1. An apparatus comprising:a pressure vessel comprising an upper vessel section and a lower vessel section;a nuclear reactor core comprising fissile material contained in a containing structure and disposed in the lower vessel section; andupper internals disposed in the lower vessel section above the nuclear reactor core, the upper internals including at least guide frames and internal control rod drive mechanisms (CRDMs) with CRDM motors mounted on a suspended support assembly that is suspended both in and from the pressure vessel and includes a plurality of hanger plates connected by tie rods, the plurality of hanger plates including an upper hanger plate, a mid-hanger plate, and a lowermost hanger plate having alignment features configured to align the upper internals with the containing structure that contains the nuclear reactor core,wherein the internal CRDMs are disposed between the mid-hanger plate and the upper hanger plate. 2. The apparatus of claim 1, wherein the containing structure includes at least one of a core former and a core basket. 3. The apparatus of claim 1, wherein the guide frames are mounted by the lowermost hanger plate and the mid-hanger plate. 4. The apparatus of claim 3, wherein the guide frames hang from the mid-hanger plate and the lowermost hanger plate provides lateral support for the guide frames. 5. The apparatus of claim 3, wherein the guide frames are bottom-supported by the lowermost hanger plate. 6. The apparatus of claim 3, wherein the lowermost hanger plate includes openings in which the bottoms of the guide frames are secured. 7. The apparatus of claim 1, wherein the pressure vessel further includes a mid-flange interposed between the upper and lower vessel sections, and the suspended support assembly of the upper internals is suspended from the mid-flange. 8. A method performed in conjunction with a nuclear reactor including a pressure vessel with upper and lower vessel sections, a nuclear reactor core comprising fissile material contained in a containing structure and disposed in the lower vessel section, and upper internals disposed in the lower vessel section that include at least guide frames and internal control rod drive mechanisms (CRDMs) with CRDM motors mounted on a suspended support assembly that is suspended both in and from the pressure vessel and includes a plurality of hanger plates, the plurality of hanger plates including an upper hanger plate, a mid-hanger plate, and a lower hanger plate connected by tie rods, the method comprising:inserting the upper internals into the lower vessel section;disposing the internal CRDMs between the upper hanger plate and the mid-hanger plate; andduring the inserting, aligning the upper internals with the nuclear reactor core by engaging alignment features of a lowermost hanger plate of the suspended support assembly with the containing structure that contains the nuclear reactor core. 9. The method of claim 8 further comprising:suspending the guide frames from the mid-hanger plate above the lower hanger plate; andlaterally supporting bottoms of the guide frames by the lower hanger plate. 10. The method of claim 8 further comprising:bottom supporting the guide frames by the lower hanger plate. 11. An apparatus comprising:a pressure vessel comprising an upper vessel section and a lower vessel section;a nuclear reactor core comprising fissile material contained in a containing structure and disposed in the lower vessel section; andupper internals disposed in the lower vessel section, the upper internals including at least guide frames and internal control rod drive mechanisms (CRDMs) with CRDM motors mounted on a suspended support assembly that is suspended both in and from the pressure vessel and includes a plurality of hanger plates connected by tie rods, the plurality of hanger plates including an upper hanger plate, a mid-hanger plate and a lowermost hanger plate engaging bottoms of the guide frames,wherein the internal CRDMs are disposed between the mid-hanger plate and the upper hanger plate. 12. The apparatus of claim 11, wherein the guide frames are mounted between the lowermost hanger plate and the mid-hanger plate. 13. The apparatus of claim 12, wherein the guide frames hang from the mid-hanger plate and the lowermost hanger plate provides lateral support for the guide frames. 14. The apparatus of claim 11, wherein the guide frames are bottom-supported by the lowermost hanger plate. 15. The apparatus of claim 11, wherein the lowermost hanger plate includes openings in which the bottoms of the guide frames are secured.