Abstract: The present invention relates to a fuel assembly in or for a boiling water reactor, comprising a plurality of vertical fuel rods extending between a top and a bottom tie plate and surrounded by a sleeve-formed casing where the fuel rods are positioned with the aid of a plurality of axially separated spacers. The invention is characterized in that only one fuel rod is detachably arranged in the top tie plate and in the bottom tie plate and in that at least one of the other fuel rods is fixed to the bottom tie plate and adapted to extend above the top tie plate to obtain a tensile-force-transmitting connection with the bottom tie plate.

Abstract: A fuel assembly (16) for a boiling-water nuclear reactor arranged in groups with four fuel assemblies in each group and with a centrally placed control rod (17) forming a supercell. Each fuel assembly (16) includes a plurality of vertical fuel rods (12) with enriched nuclear fuel material (24), said rods being arranged between a bottom tie plate (13) and a top tie plate (14) in a surrounding vertical fuel channel (1) which is connected to a transition section (2). The transition section is provided with holes (20a-d) for by-pass flow outside the fuel assembly. The fuel assembly is characterized in that the by-pass holes are arranged in such a way that when turning the fuel assembly (16), including the transition section (2), 90.degree., 180.degree. or 270.degree. around the longitudinal axis of the fuel assembly, said holes are adapted to direct the by-pass flow away from the control rod (17).