A modular nuclear reactor comprises a plurality of sections arranged in a pattern and a side reflector material surrounding the plurality of sections. Each section includes a tank comprising a front plate, a back plate, side plates, a top plate, and a bottom plate. A plurality of grid plates are located within the tank. Each grid plate comprises a plurality of apertures and is vertically separated from an adjacent grid plate. The tank further includes a plurality of fuel elements extending through each grid plate. A plurality of heat pipes extend through each grid plate, the top plate, and an upper reflector. Methods of forming the modular nuclear reactor are also disclosed.

A detection apparatus includes a resonant electrical circuit supported within an interior of a nuclear fuel rod generates a response pulse in response to an excitation pulse and transmits the response pulse through a cladding of the fuel rod to another location within a reactor in which the fuel rod is housed and without any breach in the cladding. A characteristic of the response pulse is indicative of a condition of the fuel rod. The detection apparatus also includes a transmitter positioned outside the cladding, in the reactor, in the vicinity of the fuel rod and configured to generate the excitation pulse and transmit the excitation pulse through the cladding to the resonant electrical circuit. A receiver is supported within the reactor outside of the cladding and, in response to the response pulse, communicates a signal to an electronic processing apparatus outside of the reactor.

A detection apparatus includes a resonant electrical circuit supported within an interior of a nuclear fuel rod generates a response pulse in response to an excitation pulse and transmits the response pulse through a cladding of the fuel rod to another location within a reactor in which the fuel rod is housed and without any breach in the cladding. A characteristic of the response pulse is indicative of a condition of the fuel rod. The detection apparatus also includes a transmitter positioned outside the cladding, in the reactor, in the vicinity of the fuel rod and configured to generate the excitation pulse and transmit the excitation pulse through the cladding to the resonant electrical circuit. A receiver is supported within the reactor outside of the cladding and, in response to the response pulse, communicates a signal to an electronic processing apparatus outside of the reactor.

A fuel element has a ratio of area of fissionable nuclear fuel in a cross-section of the tubular fuel element perpendicular to the longitudinal axis to total area of the interior volume in the cross-section of the tubular fuel element that varies with position along the longitudinal axis. The ratio can vary with position along the longitudinal axis between a minimum of 0.30 and a maximum of 1.0. Increasing the ratio above and below the peak burn-up location associated with conventional systems reduces the peak burn-up and flattens and shifts the burn-up distribution, which is preferably Gaussian. The longitudinal variation can be implemented in fuel assemblies using fuel bodies, such as pellets, rods or annuli, or fuel in the form of metal sponge and meaningfully increases efficiency of fuel utilization.

A fuel element has a ratio of area of fissionable nuclear fuel in a cross-section of the tubular fuel element perpendicular to the longitudinal axis to total area of the interior volume in the cross-section of the tubular fuel element that varies with position along the longitudinal axis. The ratio can vary with position along the longitudinal axis between a minimum of 0.30 and a maximum of 1.0. Increasing the ratio above and below the peak burn-up location associated with conventional systems reduces the peak burn-up and flattens and shifts the burn-up distribution, which is preferably Gaussian. The longitudinal variation can be implemented in fuel assemblies using fuel bodies, such as pellets, rods or annuli, or fuel in the form of metal sponge and meaningfully increases efficiency of fuel utilization.

There is provided a core of a fast reactor including: a core fuel region in which core fuel assemblies loading a metal fuel are arranged on a central region in a radial direction of the core; an inner blanket fuel region in which blanket fuel assemblies loading another metal fuel are circumferentially arranged on an inner portion of the core fuel region; and an outer peripheral blanket fuel region in which the blanket fuel assemblies are circumferentially arranged on an outer periphery of the core fuel region, wherein the metal fuel is formed of a UPuZr alloy or an alloy of U, Pu, TRU other than Pu, and Zr, the other metal fuel is formed of an alloy of U and Zr, and the Zr content of the other metal fuel is lower than the Zr content of the metal fuel.

Fission reactor has a cladding encasing a heat generating source including a fissionable nuclear fuel composition. The heat generating source is offset from the surface of the cladding and molten metal is located within the void space formed by the offset. As a liquid, the molten metal will flow and occupy any contiguous network of void space within the fuel cavity and provides thermal transfer contact between the heat generating source and the cladding. The cladding separates the heat generating source and the molten metal from the primary coolant volume.

Fission reactor has a cladding encasing a heat generating source including a fissionable nuclear fuel composition. The heat generating source is offset from the surface of the cladding and molten metal is located within the void space formed by the offset. As a liquid, the molten metal will flow and occupy any contiguous network of void space within the fuel cavity and provides thermal transfer contact between the heat generating source and the cladding. The cladding separates the heat generating source and the molten metal from the primary coolant volume.

An elongate fuel element is described that has a silicon carbide cladding enclosing a fuel, such as UO.sub.2, wherein the fuel is dimensioned relative to the cladding to define gaps at each lateral end of the enclosure sufficiently large such that upon swelling in use, the fuel does not increase the strain on the cladding beyond the limits of the claddings strain tolerance. The lateral gaps at the ends of the fuel allow lateral expansion during swelling that reduces the strain on the cladding.

An elongate fuel element is described that has a silicon carbide cladding enclosing a fuel, such as UO.sub.2, wherein the fuel is dimensioned relative to the cladding to define gaps at each lateral end of the enclosure sufficiently large such that upon swelling in use, the fuel does not increase the strain on the cladding beyond the limits of the claddings strain tolerance. The lateral gaps at the ends of the fuel allow lateral expansion during swelling that reduces the strain on the cladding.