Abstract: A cooling system for a reactor module includes a reactor pressure vessel that houses primary coolant and a steam generator that lowers a temperature of the reactor pressure vessel by transferring heat from the primary coolant to a secondary coolant that circulates through the steam generator. The steam generator releases at least a portion of the secondary coolant as steam. Additionally, the cooling system includes a containment vessel that at least partially surrounds the reactor vessel in a containment region. The containment region is dry during normal operation of the reactor module. A controller introduces a source of water into the containment region in response to a non-emergency shut down of the reactor module. The source of water is located external to the containment vessel, and the water is introduced into the containment region after the steam generator has initially lowered the temperature of the reactor pressure vessel in response to releasing the steam.

Abstract: A support structure for attenuating seismic forces in one or more reactor modules housed in a reactor building includes a mounting structure that may be configured to securely connect the support structure to a floor of the reactor building. A receiving area may be sized to receive a lower portion of a reactor module, and the support structure may be configured to at least partially surround the lower portion of the reactor module within the receiving area. The support structure may further include a retention system located near a top surface of the support structure. The retention system may be configured to contact the reactor module during a seismic event, and an upper portion of the reactor module may extend above the retention system without contacting the support structure.

Abstract: A steam generation system may include a plurality of heat transfer tubes configured to circulate a secondary coolant of the steam generation system. The steam generation system may be thermally coupled to a reactor vessel, and the reactor vessel may be configured to house a primary coolant. Heat generated from within the reactor vessel may be transferred from the primary coolant to the secondary coolant. The steam generation system may further include an inclined tube sheet fluidly coupled to the plurality of heat transfer tubes. The inclined tube sheet may be attached to a wall of the reactor vessel in a non-horizontal orientation.

Abstract: A system for attenuating seismic forces includes a reactor pressure vessel containing nuclear fuel and a containment vessel that houses the reactor pressure vessel. Both the reactor pressure vessel and the containment vessel may include a bottom head. Additionally, the system may include a base support that is configured to contact a support surface on which the containment vessel is positioned in a substantially vertical orientation. An attenuation device may be located between the bottom head of the reactor pressure vessel and the bottom head of the containment vessel. Seismic forces that travel from the base support to the reactor pressure vessel via the containment vessel may be attenuated by the attenuation device in a direction that is substantially lateral to the vertical orientation of the containment vessel.

Abstract: A nuclear reactor control rod drive assembly includes a control rod drive mechanism coupled to a drive shaft and operable to bi-directionally urge the drive shaft through a portion of an inner volume of a reactor vessel at a first force; a control rod manifold coupled to the drive shaft; a plurality of control rods coupled to the control rod manifold, the plurality of control rods adjustable among a plurality of positions within the inner volume of the reactor vessel based on operation of the control rod drive mechanism; and at least one variable strength joint positioned between the control rod drive mechanism and the plurality of control rods.

Abstract: A tube support assembly for a steam generator system is disclosed herein, including a sheet or support bar configured to support a plurality of heat transfer tubes of the steam generator system and a set of projections extending from a surface of the sheet or support bar. A distance that the set of projections extend from the surface of the sheet or support bar may be greater than, or equal to, an external diameter of a heat transfer tube. The adjacent tubes of the plurality of tubes may be separated from each other by one or more projections.

Abstract: A nuclear reactor seismic isolation assembly includes an enclosure that defines a volume; a plastically-deformable member mounted, at least in part, within the volume; and a stretching member moveable within the enclosure to plastically-deform the plastically-deformable member in response to a dynamic force exerted on the enclosure.