A variable diameter fuel rod of a nuclear reactor assembly is disclosed. The variable diameter fuel rod includes an elongated cladding tube configured to house a plurality of fuel pellets including a fissile material arranged in a fuel stack orientation. The elongated cladding tube includes first and second axial reflector regions and a middle axial region therebetween. The middle axial region comprises an outer diameter defined as d.sub.1. The first and second axial reflector regions include an outer cladding diameter defined as d.sub.2 and d.sub.3, respectively. The variable diameter fuel rod further includes a transitional region between the diameter d.sub.1 of the middle axial region and the diameter d.sub.2 of the axial reflector region. The diameter d.sub.2 of the axial reflector region is greater than the diameter d.sub.1 of the middle axial region.

A getter element includes a getter material reactive with a fission product contained within a stream of liquid and/or gas exiting a fuel assembly of a nuclear reactor. At least one transmission pathway passes through the getter element that is sufficiently sized to maintain a flow of the input stream through the getter element at above a selected flow level. At least one transmission pathway includes a reaction surface area sufficient to uptake a pre-identified quantity of the fission product.

A getter element includes a getter material reactive with a fission product contained within a stream of liquid and/or gas exiting a fuel assembly of a nuclear reactor. At least one transmission pathway passes through the getter element that is sufficiently sized to maintain a flow of the input stream through the getter element at above a selected flow level. At least one transmission pathway includes a reaction surface area sufficient to uptake a pre-identified quantity of the fission product.

To provide is a fuel assembly capable of easily adjusting average MA enrichment in an inner blanket region. An inner core fuel assembly 7 loaded in an inner core region 2 of a core of a fast reactor includes a plurality of fuel rods 10 and a plurality of fuel rods 19. Each of the fuel rods 10 includes a lower core fuel region 12, an inner blanket region 11, and an upper core fuel region 13. A U—Pu—Zr metal fuel is disposed in the lower core fuel region 12 and the upper core fuel region 13, and a U—Zr metal fuel is disposed in the inner blanket region 11. Each of the fuel rods 19 includes a lower core fuel region 12, an inner blanket region 20, and an upper core fuel region 13. A U—Pu—Zr metal fuel is disposed in the lower core fuel region 12 and the upper core fuel region 13 of the fuel rod 19, and a MA-Zr metal fuel is disposed in the inner blanket region 20. By adjusting the number of the fuel rods 10 and the number of the fuel rods 19, MA enrichment in the inner blanket region 9 of the fuel assembly 7 can be easily adjusted.

A getter element includes a getter material reactive with a fission product contained within a stream of liquid and/or gas exiting a fuel assembly of a nuclear reactor. At least one transmission pathway passes through the getter element that is sufficiently sized to maintain a flow of the input stream through the getter element at above a selected flow level. At least one transmission pathway includes a reaction surface area sufficient to uptake a pre-identified quantity of the fission product.

A getter element includes a getter material reactive with a fission product contained within a stream of liquid and/or gas exiting a fuel assembly of a nuclear reactor. At least one transmission pathway passes through the getter element that is sufficiently sized to maintain a flow of the input stream through the getter element at above a selected flow level. At least one transmission pathway includes a reaction surface area sufficient to uptake a pre-identified quantity of the fission product.

A getter element includes a getter material reactive with a fission product contained within a stream of liquid and/or gas exiting a fuel assembly of a nuclear reactor. At least one transmission pathway passes through the getter element that is sufficiently sized to maintain a flow of the input stream through the getter element at above a selected flow level. At least one transmission pathway includes a reaction surface area sufficient to uptake a pre-identified quantity of the fission product.

A getter element includes a getter material reactive with a fission product contained within a stream of liquid and/or gas exiting a fuel assembly of a nuclear reactor. At least one transmission pathway passes through the getter element that is sufficiently sized to maintain a flow of the input stream through the getter element at above a selected flow level. At least one transmission pathway includes a reaction surface area sufficient to uptake a pre-identified quantity of the fission product.

The fuel element of the present invention includes a cladding tube and a metal fuel contained in the cladding tube, in which a gas plenum region is formed above the metal fuel and inside the cladding tube and has a small-diameter portion in the gas plenum region. Further, the fuel assembly of the present invention includes the fuel element of the present invention and a wrapper tube surrounding the fuel element, in which a coolant material passage is formed between the fuel element and the fuel element. Further, the core of the present invention includes an inner core fuel region loaded with the fuel assembly according to the present invention, and an outer core fuel region loaded with the fuel assembly of the present invention.

The fuel element of the present invention includes a cladding tube and a metal fuel contained in the cladding tube, in which a gas plenum region is formed above the metal fuel and inside the cladding tube and has a small-diameter portion in the gas plenum region. Further, the fuel assembly of the present invention includes the fuel element of the present invention and a wrapper tube surrounding the fuel element, in which a coolant material passage is formed between the fuel element and the fuel element. Further, the core of the present invention includes an inner core fuel region loaded with the fuel assembly according to the present invention, and an outer core fuel region loaded with the fuel assembly of the present invention.