Abstract: An apparatus and method are provided for suppressing the formation of vortices in circulating coolant fluid of a nuclear reactor. A vortex-suppressing plate having a plurality of openings therein is suspended within the lower plenum of a reactor vessel below and generally parallel to the main core support of the reactor. The plate is positioned so as to intersect vortices which may form in the circulating reactor coolant fluid. The intersection of the plate with such vortices disrupts the rotational flow pattern of the vortices, thereby disrupting the formation thereof.

Abstract: Modular neutron reflector assemblies removably insertable into the irregular space in a nuclear reactor between a generally cylindrical array of square fuel assemblies comprising the core and the cylindrical core barrel surrounding the core, include an elongated enclosure having a strongback adjacent the core barrel and flat plates adjacent the fuel assemblies. The strongback is thicker than the steel plates by an amount which results in the strongback and plates reaching approximately the same temperature to minimize thermal stresses despite the 8 to 20 times greater nuclear heating at the core side of the enclosure as opposed to that at the core barrel side. The enclosure is suspended by a single point mounting on the core barrel which permits vertical, radial, and circumferential expansion but a pin depending from the lower end of the enclosure slides in a vertical bore in the reactor lower core support plate to limit lateral movement while allowing unrestrained vertical expansion and contraction.

Abstract: A vibration arrestor for use in combination with the support structure for the upper ends of rod guides disposed in parallel axial relationship in an inner barrel assembly of a pressurized water reactor vessel, the rod guides being supported between a first, lower plate and a second, upper plate with their respective top ends disposed adjacent the second plate. At least for a selected type of rod guides and associated top plates, apertures provided in the top plates receive therein corresponding extensions which depend from the second plate.

Abstract: Failure of the control-rod assemblies, particularly the control-rod guides and the WDRC's, by transverse flow of coolant through these members is prevented by directing the flow through a calandria above the guides. To avoid a high pressure drop in the coolant between the calandria and the outlet nozzles, the outlet nozzles are at the same level as the calandria. The calandria has hollow tubes between upper and lower supports. The length of the portion of the tubes between the supports is greater than the diameter of the outlet nozzles.

Abstract: The inner barrel assembly of a pressurized water reactor includes an array of interleaved first and second matrices of respective first and second pluralities of rod guides of corresponding first and second different types, disposed in parallel axial relationship, the bottom ends of the guides being affixed to the top core plate of a lower barrel assembly. A flexible support structure connects the top ends of the rod guides to a lower calandria plate and particularly includes corresponding first and second pluralities of top support plates respectively connected to the rod guides of the first and second different types and having outer peripheries generally corresponding to the respective first and second types of rod guides and inner openings for permitting axial passage therethrough of corresponding, first and second different types of rod clusters.

Abstract: Improvements in the design of internal components of J-shaped steam generators for liquid metal fast breeder reactors. Complex design improvements have been made to the internals of J-shaped steam generators which improvements are intended to reduce tube vibration, tube jamming, flow problems in the upper portion of the steam generator, manufacturing complexities in tube spacer attachments, thermal stripping potentials and difficulties in the weld fabrication of certain components.