Abstract: A fuel assembly of a boiling water reactor contains a fuel assembly base closed at the top by a filter plate, a fuel assembly head, and, disposed between them, a bundle of long and medium-length fuel rods extending away from the fuel assembly base. A water channel is disposed inside the fuel rod bundle. A plurality of the medium-length fuel rods are fixed axially on a separate holding part which is connected to the upper side of the fuel assembly base.

Abstract: A fuel assembly for a pressurized water nuclear reactor includes a multiplicity of fuel rods which extend in a longitudinal direction and are guided in a plurality of spacers that are spaced apart from one another axially. The spacers of an upper region have a lower flow resistance in a transverse direction perpendicular to the longitudinal direction, than the spacers of a lower region.

Abstract: An assembly of the type having a water channel extending along a longitudinal axis and having an upper section of larger cross-section area than a lower section and at least one fuel rod receiving groove extending longitudinally on the outer surface of the lower section, fuel rods extending longitudinally and disposed around the water channel and fixing members for fixing at least one fuel rod to the water channel in the at least one groove below the upper section. According to one aspect of the invention, the at least one groove extends along the upper section such that a fuel rod received in fixing members is longitudinally extractable or insertable from the upper end side of the fuel assembly.

Abstract: An assembly of the type having a water channel extending along a longitudinal axis and having an upper section of larger cross-section area than a lower section and at least one fuel rod receiving groove extending longitudinally on the outer surface of the lower section, fuel rods extending longitudinally and disposed around the water channel and fixing members for fixing at least one fuel rod to the water channel in the at least one groove below the upper section. According to one aspect of the invention, the at least one groove extends along the upper section such that a fuel rod received in fixing members is longitudinally extractable or insertable from the upper end side of the fuel assembly.

Abstract: In a method for heat treating a fuel assembly channel made of zircaloy, the channel is continuously moved relative to a heat-treatment device and, longitudinal sections of it are heated to the beta phase range in an inductive heating zone. The longitudinal section of the channel heated in this manner is than cooled in a cooling zone to a temperature within an alpha phase range. The heat treatment is effected by at least two heating devices, which are spaced apart from one another, operate independently of each other, and each contain at least one induction coil and together form a heating zone. The channel section is first heated using a first heating device and then heat-treated using a second heating device which has less power and in that cooling is effected using a stream of inert gas applied to the outer surface of the channel.

Abstract: A fuel assembly for a pressurized water nuclear reactor includes a multiplicity of fuel rods which extend in a longitudinal direction and are guided in a plurality of spacers that are spaced apart from one another axially. The spacers of an upper region have a lower flow resistance in a transverse direction perpendicular to the longitudinal direction, than the spacers of a lower region.

Abstract: A fuel assembly of a boiling water reactor contains a fuel assembly base closed at the top by a filter plate, a fuel assembly head, and, disposed between them, a bundle of long and medium-length fuel rods extending away from the fuel assembly base. A water channel is disposed inside the fuel rod bundle. A plurality of the medium-length fuel rods are fixed axially on a separate holding part which is connected to the upper side of the fuel assembly base.

Abstract: In a boiling water fuel assembly, some of the fuel rods are shortened. It is necessary to establish a sufficiently high maximum power for transition to boiling. To optimize this power, spacers are at a constant distance at a bottom and are at a shorter distance at a top. The spacers belonging to upper group have turbulence-generating vanes which, however, do not project above the shortened fuel rods.

Abstract: In a boiling water fuel assembly, some of the fuel rods are shortened. It is necessary to establish a sufficiently high maximum power for transition to boiling. To optimize this power, spacers are at a constant distance at a bottom and are at a shorter distance at a top. The spacers belonging to upper group have turbulence-generating vanes which, however, do not project above the shortened fuel rods.

Abstract: In a foot of a fuel assembly of a boiling water reactor, an upper edge of a transition member is tight against a lower edge of a fuel assembly casing to substantially prevent bypass flow between them. Rather, bypass apertures are provided therefor over all sides of the fuel assembly casing. In a first position of a base plate lying on the transition member, the bypass apertures on some sides are blocked by lateral surfaces of the base plate, while in a second position of the base plate, the bypass apertures of other sides are blocked. The direction of the bypass flow can thus be predetermined regardless of the position of the fuel assembly casing.

Abstract: A fuel assembly includes a cluster of mutually parallel fuel rods. A fuel assembly channel laterally surrounds the cluster of fuel rods and has a substantially rectangular cross section and flat channel walls. Grid-like spacers having meshes formed therein each receive a respective one of the fuel rods for guiding the fuel rods in a plurality of axial positions. At least one support spring laterally supports each respective one of the fuel rods in the mesh guiding the fuel rod. Each of the spacers have inner ribs being aligned parallel to the fuel rods and outer peripheral ribs opposite the channel walls. At least some of the inner ribs are fastened to the peripheral ribs, and the outer peripheral ribs are joined together only by the inner ribs.

Abstract: A fuel assembly for a boiling water reactor includes a cluster of mutually parallel fuel rods. A fuel assembly channel laterally surrounds the cluster of fuel rods and has open upper and lower ends. A top plate covers the upper open end of the fuel assembly channel and has coolant outlets formed therein. A foot part is assembled from a plurality of individual parts and includes a cast transitional piece having a lower end with an inlet opening formed therein and an upper edge inserted into the open lower end of the fuel assembly channel. The transitional piece defines and surrounds a flow channel widening upward in funnel-like fashion from the inlet opening. The foot part also includes a base plate being disposed at and welded to the upper edge of the transitional piece. The base plate covers the open lower end of the fuel assembly channel and has coolant inlets formed therein.

Abstract: In a fuel assembly, lower end pieces of fuel rods, guide tubes and coolant pipes, etc., are inserted and/or screwed into a base plate and secured against lifting by a bolt. In the case of fuel rods, in particular fuel rods which do not extend over the entire length of normal rods, the bolt is screwed onto connecting parts in such a way that a releasable bayonet closure is produced. In the case of coolant pipes of boiling water reactors, there is provided in particular a screw connection which is irreleasably secured against torsion by the bolt.

Abstract: A fuel assembly for a boiling water reactor includes approximately mutually parallel fuel rods in a bundle having upper and lower ends. A skeleton holding the bundle has a handle, an upper tie plate retained on the handle at the upper end of the bundle, a lower tie plate at the lower end of the bundle, and at least one support element joining together the lower tie plate and the upper tie plate. The skeleton and the bundle are inserted in a fuel assembly case. A redundant support device holds the lower tie plate, the fuel assembly case and the upper tie plate together, when the handle is lifted.

Abstract: In order to obviate the use of supporting rods, an upper end piece of a coolant tube penetrates a fuel assembly head of a nuclear reactor fuel assembly and is supported on the fuel assembly head. A lower end piece of the coolant tube is fastened to and supported by a fuel assembly foot, in particular with rods of partial lengths. A supporting skeleton therefore includes the foot and the coolant tube with spacers. The fuel assembly head and a handle are placed on the skeleton and screwed onto the coolant tube after fuel rods are pushed into meshes of the spacer.

Abstract: In a fuel assembly, lower end pieces of fuel rods, guide tubes and coolant pipes, etc., are inserted and/or screwed into a base plate and secured against lifting by a bolt. In the case of fuel rods, in particular fuel rods which do not extend over the entire length of normal rods, the bolt is screwed onto connecting parts in such a way that a releasable bayonet closure is produced. In the case of coolant pipes of boiling water reactors, there is provided in particular a screw connection which is irreleasably secured against torsion by the bolt.

Abstract: A gap between a foot part and a channel of a boiling water fuel assembly is sealed against a coolant flow by a spring being supported by a central part thereof against the channel and by sides thereof against the foot part and being clipped and/or clamped on at that location even when all of the fuel rods are removed. For this purpose, the upper edge can extend around the foot part edge or the spring may be constructed as a spring band running entirely around the foot part and being fitted into a lateral groove.

Abstract: A fuel assembly for a boiling water reactor includes an elongated box extending between a top part and a bottom part, having box walls with flat outer surfaces defining a polygonal outer cross section with rounded corners, an interior and a longitudinal axis. A bundle of fuel rods is disposed in the box and aligned parallel to one another and to the longitudinal axis of the box. The fuel rods are disposed beside one another in rows parallel to the box walls. The box walls have reinforcements protruding into the interior in the vicinity of the rounded corners defining a relatively increased wall thickness, and the box walls have a relatively reduced wall thickness between the reinforcements.

Abstract: A fuel assembly for a boiling water reactor includes an elongated case having an interior and inner surfaces. A base part has inlet openings discharging into the interior of the case for coolant flowing in a given flow direction and a head part has outlet openings leading out of the interior of the case for the coolant flowing in the given flow direction. Mutually parallel fuel rods containing nuclear fuel are disposed in the case between the base and head parts. The inner surfaces of the case have a profile with a rectilinear alignment as seen in the given flow direction and flow trippers extending transversely to the alignment in the form of bulges protruding inward in the given flow direction. Each of the bulges has a sloped surface facing toward the coolant with an impact surface substantially perpendicular to the given flow direction.

Abstract: A fuel assembly for a boiling water reactor includes an elongated fuel assembly case, mutually parallel fuel rods having longitudinal axes and being disposed in the case, and longitudinally extending inner walls having lateral surfaces facing toward the fuel rods. At least some of the lateral surfaces have grooves formed therein extending perpendicular to the longitudinal axes of the fuel rods. A boiling water reactor includes a boiling water circuit having a pressure vessel and a steam turbine. A plurality of the fuel assemblies are disposed mutually parallel in the pressure vessel. The fuel rods are bathed by boiling water flowing around them in the longitudinal direction of the fuel rods.