Suspended upper internals for compact nuclear reactor including a lower hanger plate

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;
• and
• during 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.

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;
• and
• upper 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.