Abstract: A lightweight flat plate heat exchanger comprised of two or more essentially parallel flat plates which are formed and arranged to provide fluid flow passages between the plates. New combinations of plastic plates include the usage of transparent plastic foam and honeycomb structures. Improved shapes of flow passages include the usage of flow nozzles, flow diffusers, and jet pumps to increase fluid flow and heat transfer. The invention includes the usage of transparent plastic foam plates which are shaped to concentrate solar energy onto plastic tubes. Clear plastic tubes containing black heat transfer fluid are included. The invention includes the usage of spiral flow channels within plastic foam plates. Six different embodiments of the invention are included. Five of the embodiments could be used as efficient lightweight solar collectors.

Abstract: Nuclear reactor upper internal guide tube having a flow diffuser integral with its bottom end. The guide tube provides guidance for control rods during their ascent or descent from the reactor core. The flow diffuser serves to divert the upward flow of reactor coolant around the outside of the guide tube thereby limiting the amount of coolant flow and turbulence within the guide tube, thus enhancing the ease of movement of the control rods.

Abstract: A liquid-cooled nuclear reactor including fuel assemblies mounted within a reactor vessel having linearly movable control rods passing through control rod guide tubes into respective aligned fuel assemblies. Reactor coolant circulates through the assemblies, guide tubes and other vessel internals structures located above the assemblies and is discharged through an outlet nozzle positioned above the elevation of primary flow openings in the guide tube walls. The guide tube includes internal horizontal supports and a length limited continuous control rod guide which, in conjunction with the flow openings, alleviate detrimental coolant cross flows and frictional restraints imposed upon the control rods.

Abstract: Apparatus for baffling the flow of reactor coolant fluid into and about the core of a nuclear reactor. The apparatus includes a plurality of longitudinally aligned baffle plates with mating surfaces that allow longitudinal growth with temperature increases while alleviating both leakage through the aligned plates and stresses on the components supporting the plates.

Abstract: A flow baffling arrangement for the core of a nuclear reactor. A plurality of core formers are aligned with the grids of the core fuel assemblies such that the high pressure drop areas in the core are at the same elevations as the high pressure drop areas about the core periphery. The arrangement minimizes core bypass flow, maintains cooling of the structure surrounding the core, and allows the utilization of alternative beneficial components such as neutron reflectors positioned near the core.

Abstract: A baffle-former arrangement for the reactor vessel internals of a nuclear reactor. The arrangement includes positioning of formers at the same elevations as the fuel assembly grids, and positioning flow holes in the baffle plates directly beneath selected former grid elevations. The arrangement reduces detrimental cross flows, maintains proper core barrel and baffle temperatures, and alleviates the potential of overpressurization within the baffle-former assembly under assumed major accident conditions.

Abstract: An arrangement for cooling the fasteners affixing a core barrel to a core former and a core baffle to a core former in the reactor vessel internals of a nuclear reactor. The arrangement allows the flowing reactor coolant to contact the fasteners, preferably bolts with an elliptical neck, and maintain lower bolt operating temperatures than previously experienced.