Abstract: A sealoff device and method are disclosed for controlling the level of a fluid within first and second confined regions which are arranged in fluid communication with one another. In the preferred embodiment, the invention permits shielding of the tube bundle contained within the wrapper of a nuclear steam generator while controlling the level of the working fluid within the surrounding annular downcomer passage. A sealoff device constructed of a flexible hollow tube is provided in sealing engagement between the wrapper and outer shell forming the downcomer passage to provide a substantially fluid-tight seal thereat. The sealoff device permits the maintaining of a high water level inside the wrapper to shield the tube bundle which is emitting nuclear radiation while maintaining a low water level within the downcomer passage to permit greater accessibility for repair and maintenance of the steam generator in a dry environment and to permit greatly increased working time in a greatly reduced radiation field.

Abstract: A filter for removing debris of a predetermined size from a fluid path has a first face disposed transversely in the fluid path and a second face disposed substantially parallel to the first face and displaced therefrom in the direction of fluid flow. The displacement of the second face from the first face substantially defines the strength of the filter with respect to deformation by the fluid flow. The first and second faces cooperate to define a plurality of apertures extending through the filter. The apertures are of a size to preclude passage of the debris while presenting a predetermined resistance to the fluid flow. That predetermined resistance is substantially independent of the filter's strength.

Abstract: A structural support system for the core of a nuclear reactor which achieves relatively restricted clearances at operating conditions and yet allows sufficient clearance between fuel assemblies at refueling temperatures. Axially displaced spacer pads having variable between pad spacing and a temperature compensated radial restraint system are utilized to maintain clearances between the fuel elements. The core support plates are constructed of metals specially chosen such that differential thermal expansion produces positive restraint at operating temperatures.

Abstract: A nuclear reactor, particularly a liquid-metal breeder reactor, whose upper internals include outlet modules for channeling the liquid-metal coolant from selected areas of the outlet of the core vertically to the outlet plenum. The modules are composed of a highly-refractory, high corrosion-resistant alloy, for example, INCONEL-718. Each module is disposed to confine and channel generally vertically the coolant emitted from a subplurality of core-component assemblies. Each module has a grid with openings, each opening disposed to receive the coolant from an assembly of the subplurality. The grid in addition serves as a holdown for the assemblies of the corresponding subplurality preventing their excessive ejection upwardly from the core. In the region directly over the core the outlet modules are of such peripheral form that they nest forming a continuum over the core-component assemblies whose outlet coolant they confine.

Abstract: A control system for a nuclear reactor comprising hollow mechanically operated control rods and a liquid neutron absorber which may be circulated through the hollow control rods. The liquid neutron absorber provides the nuclear reactor with a redundant safety system to deactivate the reactor.