Abstract: A spacer for supporting a plurality of fuel rods forming a nuclear fuel assembly. The spacer comprises a peripheral band surrounding a bundle of the fuel rods and a plurality of spacer framework units, each holding therein one fuel rod. The spacer framework units are welded or brazed to the peripheral band so as to be arranged inside the peripheral band. Spring members are integrally formed on each of the spacer framework units. The spacer framework units, the spring members and the peripheral band are made of a zirconium alloy containing 5-25% by weight niobium and 0.1-1% by weight chromium and/or iron.

Abstract: A nuclear fuel element is provided which comprises a cladding tube having end plugs for sealing ends of the cladding tube and a multiplicity of fuel pellets stacked within the cladding tube. Each of the fuel pellets has a substantially cylindrical external lateral surface and a plurality of longitudinal recesses having rounded root portions on the external lateral surface, and has a height within the range from 1/2 to 1/3 of the outer diameter thereof. These fuel pellets with the floral petal shape are stacked in such a manner that the recesses of one pellet are not aligned with the recesses of adjacent upper and/or lower pellets.

Abstract: A nuclear fuel rod is made up of a stack of pellets of fuel material and a cladding or sheathing tube is provided. A metallic supporting structure is interposed between the pellet stack and an end plug of said cladding tube. The supporting structure can maintain the original shape under the normal operating reactor conditions, but when an excess stress is applied to the supporting structure, a mechanical break is produced in the supporting structure to reduce its supporting length, otherwise the excess stress would be exerted on said cladding tube in the vicinity of the end plug joints and might cause failure of the fuel rod.

Abstract: A fuel assembly spacer for a nuclear reactor, the spacer having a plurality of spring with a uniform spring strength and arranged symmetrically around the outer periphery of the spacer so that the fuel assembly can be coaxially disposed with respect to a coolant duct. This spacer serves to maintain as uniform a gap as possible between the inner wall of the coolant duct and each outermost fuel rod in the fuel assembly so that the flow of the coolant keeps it symmetry in the section of the coolant duct, thereby improving the thermal performance of the fuel assembly.