Abstract: A modular, nuclear waste conversion reactor that continuously produces usable energy while converting U-238 and/or other fertile waste materials to fissionable nuclides. The reactor has a highly uniform, self-controlled, core (2) with a decades-long life and does not require reactivity control mechanisms within the boundary of the active core during operation to retain adequate safety. The exemplary embodiment employs high-temperature helium coolant, a dual-segment (22) initial annular critical core, carbide fuel, a fission product gas collection system, ceramic cladding and structural internals to create a modular reactor design that economically produces energy over multiple generations of reactor cores with only minimum addition of fertile material from one generation to the next.

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: An apparatus for controlling the flow of coolant through a nuclear fuel assembly, in which a coolant flow restrictor 26 having longitudinal ducts 30 is provided with plug members 48, 49, 50 of different lengths. The plug members 48, 49, 50 are moved longitudinally by the effect of neutron induced growth on an actuating member 60. A connecting member 53 converts the growth of the actuating member 60 into a longitudinal movement of the plug members 48, 49, 50 so that they are progressively withdrawn from the flow restrictor 26 to increase the flow of coolant through the flow restrictor 26.

Abstract: A device which controls coolant flow through a nuclear reactor assembly comprises a baffle means at the exit end of said assembly having a plurality of orifices, and a bimetallic member in operative relation to the baffle means such that at increased temperatures said bimetallic member deforms to unblock some of said orifices and allow increased coolant flow therethrough.

Abstract: A nuclear radiation actuated valve for a nuclear reactor. The valve has a valve first part (such as a valve rod with piston) and a valve second part (such as a valve tube surrounding the valve rod, with the valve tube having side slots surrounding the piston). Both valve parts have known nuclear radiation swelling characteristics. The valve's first part is positioned to receive nuclear radiation from the nuclear reactor's fuel region. The valve's second part is positioned so that its nuclear radiation induced swelling is different from that of the valve's first part. The valve's second part also is positioned so that the valve's first and second parts create a valve orifice which changes in size due to the different nuclear radiation caused swelling of the valve's first part compared to the valve's second part. The valve may be used in a nuclear reactor's core coolant system.

Abstract: A nuclear reactor including an inner core containing both fuel and blanket assemblies and means for cooling the assemblies by passing liquid coolant, specifically sodium, across and in contact with the latter is disclosed herein. The nuclear reactor also includes a particular technique for distributing the liquid coolant into first and second separate plenums, each of which includes an inlet adapted to receive the coolant. These first and second plenums are maintained in fluid communication with the fuel and blanket assemblies, respectively, whereby to pass received coolant across and in contact with all of the assemblies. In addition, the distribution of the coolant is automatically changed, at least to a limited extent, between these first and second plenum in response to predetermined thermal changes in said assemblies.

Abstract: A perforated depressor plate extending across the bottom of the instrument ree of a fast breeder reactor cooperates with a circular cylindrical metal bellows forming a part of the upper adapter of each core assembly and bearing on the bottom of the depressor plate to restrict flow of coolant between core assemblies, thereby reducing significantly the pressure differential between the coolant inside the core assemblies and the coolant outside of the core assemblies. Openings in the depressor plate are slightly smaller than the top of the upper adapter so the depressor plate will serve as a backup mechanical holddown for the core. In addition coolant mixing devices and locating devices are provided attached to the depressor plate.

Abstract: A nuclear reactor core assembly is described in which a plurality of fuel elements and a plurality of blanket elements are arranged in a core assembly. Conduit means direct fluid coolant through the fuel elements and through the blanket elements. The conduit means which direct the coolant through the blanket elements have flow restrictor means therein comprising a plurality of surface roughened elements for limiting the flow of coolant through the blanket elements. The flow restrictor means have a static configuration such that at shutdown, the percentage of coolant flow through the blanket elements compared with the total coolant flow is substantially greater than the percentage of coolant flow through the blanket elements during full power operation.