In one embodiment, the fuel bundle for a liquid metal cooled reactor includes a channel, a nose assembly secured to a lower end of the channel, and a plurality of fuel rods disposed within the channel. At least one of the fuel rods has at least one guard ring surround the fuel rod and spacing the fuel rod from adjacent fuel rods.

Fuel spacers include a perimeter piece and alignment strips extending within the perimeter piece. Alignment strips may have directional variation while still extending in an overall straight line between two contact points on the perimeter piece. Two alignment strips, by their relative positioning and shape, create distinct openings for fuel rods, through which rods may pass and be supported by the spacer on all sides. Alignment strips can be parallel or skew but need not physically intersect or extend at overall right angles to form such surrounding and supporting openings. Shape may be variable, such as a waveform, zig-zag, or saw-tooth. Several layers of alignment strips at any desired angle are useable in spacers, and alignment strips may be varied in length, shape, and number to account for different fuel assembly sizes and features, such as water rods.

A nuclear fuel assembly grid that includes two zones, a protected zone and a crumbled zone. The crumbled zone occupies the periphery of the grid and is designed to experience plastic deformation under high impact loads and the protected zone occupies the interior of the grid where the control rod guide thimbles are located and protects all of the control rod guide thimble locations by experiencing only plastic deformation under such loads.

A nuclear fuel assembly grid that includes two zones, a protected zone and a crumbled zone. The crumbled zone occupies the periphery of the grid and is designed to experience plastic deformation under high impact loads and the protected zone occupies the interior of the grid where the control rod guide thimbles are located and protects all of the control rod guide thimble locations by experiencing only plastic deformation under such loads.

A nuclear fuel assembly grid having a torpedo-shaped mixing vane assembly supported at each intersection of the grid straps that surrounds a fuel rod support location. The torpedo-shaped stem supports mixing vanes that extend over each of the fuel rod support locations.

A segmented fuel assembly for use in a nuclear reactor is disclosed. The segmented fuel assembly comprises a lower nozzle, an upper nozzle, a plurality of guide tubes positioned intermediate the lower nozzle and the upper nozzle, and a plurality of fuel segments positioned intermediate the upper nozzle and the lower nozzle. The plurality of guide tubes are arranged in a first array. Each guide tube defines a longitudinal axis. Each fuel segment comprises a body defining a plurality of coolant flow channels and a plurality of guide tube openings. The guide tube openings are arranged in a second array corresponding to the first array. The guide tubes are positioned in the guide tube openings.

A nuclear reactor is designed to allow efficient packing of components within the reactor vessel, such as by offsetting the core, and/or vertically stacking components. The in-vessel storage system can be separate from the support cylinder and these components can be fabricated and shipped separately and coupled together at the construction site. Furthermore, the in-vessel storage system can be located adjacent to the core rather than being located circumferentially around it, and may also be located beneath the heat exchanger to further improve packing of components within the vessel. Through these, and other changes, the delicate components can be manufactured in a manufacturing facility, assembled, and shipped by commercial transportation options without exceeding the shipping envelope.

A nuclear fuel assembly is constructed with fuel assembly components that are wire wrapped and positioned in hexagonal rings within a fuel assembly duct. The fuel assembly components positioned in an outermost ring of the fuel assembly are wire wrapped with a pitch that is shorter than fuel assembly components positioned at an interior ring of the fuel assembly. The shorter pitch at the outer ring of the fuel assembly increases pressure drop of a coolant fluid at the edge and corner subchannels and thereby reduces the temperature gradient across the fuel assembly, which provides a higher output temperature of the nuclear reactor without substantially increasing peak temperature of the fuel cladding.