Geometrical shape in which nuclear fuel, coated with hull material, is brought into a reactor. Mostly several fuel rods are combined to form a fuel element (Brennelement, BE). In the case of the Krümmel nuclear power plant with a boiling water reactor 72 fuel rods form a fuel element, in the case of the pressurised water reactor of the Emsland nuclear power plant 300 fuel rods have been combined to form one fuel element.