Abstract: A boiling water reactor fuel assembly is provided with an elongated, vertical stiffening device having four stiffening wings which are each attached to a wall of the fuel box. Each stiffening wing has at least one vertically directed passageway for water.

Abstract: A fuel assembly which comprises a plurality of subassemblies of fuel rods (12), which are each enclosed in a corresponding wall system (1), is provided at its upper end with a horizontal distribution channel (22, 32), extending along the periphery, which upon emergency cooling receives sprinkling water and distributes this among the different subassemblies.

Abstract: A fuel assembly for a boiling reactor is constructed according to the accompanying drawing (FIG. 1). Preferably, only partial spacers (6) are used in the fuel assembly. Each partial spacer positions only a minor portion of the total number of fuel rods in the assembly. Groups of partial spacers are arranged axially one after the other, the partial spacers in each group being positioned at at least two different levels and together positioning all fuel rods in the fuel assembly.

Abstract: An elongated absorber plate, which is stationarily mounted in a gap between two fuel assemblies in a reactor core, comprises a plurality of absorber channels which are filled with a burnable absorber material. The channels (5b) are formed by welding to each other two confronting sheet elements (2b, 3b), of which at least one is corrugated.

Abstract: In the process of applying a layer of copper and a layer of zirconium dioxide to the internal surface of a tube of a zirconium-based alloy, with the layer of zirconium dioxide being located between the copper layer and the internal surface of the tube, the tube surface is first treated with an activating solution in the form of an aqueous solution containing from about 1 to about 3 grams/liter of hydrogen fluoride, from about 2 to about 8 grams/liter of ammonium fluoride and from about 0.1 to about 0.5 gram/liter of sulfuric acid, the amounts of hydrogen fluoride and ammonium fluoride being chosen so that the amount of ammonium fluoride, calculated in moles, exceeds the amount of hydrogen fluoride, calculated in moles, by at least 5 percent.

Abstract: Boiling reactor comprising a reactor core (1) and a pressure vessel (2) enclosing said reactor core and being provided with at least one conduit for discharged steam and at least one conduit for feed water and during normal operation being filled with water up to a certain normal level (11), the steam pressure in the pressure vessel having a substantially constant value of at least 5 MPa. The pressure vessel (2) is surrounded by a water-filled pool (3) with a water volume above the reactor core (1) which is considerably greater than the water volume within the pressure vessel (2). The pressure vessel (2) is a concrete vessel having an internal thermal insulation (9). The reactor comprises emergency cooling pipes (19, 20) with valves (19', 20') connecting the reactor vessel (2) to the pool (3). The valves (19', 20') are normally closed. The pipes (19, 20) are positioned at different levels.

Abstract: A coupling assembly for joining an inlet nozzle with a conduit assembly extending concentrically therein, to provide a fluid-tight and thermally insulated flow passageway for introducing cold water into a nuclear reactor pressure vessel and the like.The coupling assembly comprises a protective sleeve surrounding the conduit assembly and wedged into abutting contact with an end portion of the conduit assembly and an inner surface of the inlet nozzle to form a fluid-tight seal therebetween. A fluid insulating medium having a decreasing temperature gradient is positioned between a portion of the protective sleeve and the surrounding inlet nozzle to create a similar decreasing temperature gradient within the inlet nozzle, in order to protect the nozzle against thermal shocks resulting from the difference in temperature between the relatively warm reactor pressure vessel surrounding the inlet nozzle and the relatively cold water flowing through the inlet nozzle.

Abstract: A fuel assembly for the core of a boiling water nuclear reactor has a plurality of boxes each surrounding a respective bundle of fuel rods. These boxes, are connected at one end to a common bottom unit, intended to be connected to an opening in a supporting plate in the core, and are also connected at their other end to a common top unit. The boxes may be detachably connected to the bottom portion and the top unit and be relocatable within the fuel assembly. Alternatively, the bundles of rods may be arranged for easy withdrawal from the boxes to enable transfer of the rod bundles between the boxes.

Abstract: The present invention relates to an improved attachment assembly for clamping a nuclear reactor foot ring into engagement with a surrounding support wall while allowing for thermal expansion of the foot ring.

Abstract: A method of refueling a nuclear reactor having a core containing a plurality of fuel rod bundles which are built up from a plurality of fuel rods includes replacing at least one burnt up fuel rod bundle with a fuel rod bundle which is at least partly composed of fuel rods from other fuel rod bundles burnt up in the reactor, the mean content of fissile material in the fuel rod bundle thus composed being higher than the mean content of fissile material in the fuel rod bundle which is replaced by the composed fuel rod bundle.

Abstract: A nuclear reactor assembly including a substantially cylindrically-shaped and vertically extending pressure vessel. A uniquely constructed bracket assembly is arranged for mounting a water distributor against an inner wall of the cylindrically-shaped pressure vessel, with the bracket assembly including a spring assembly capable of biasing an inlet conduit of the water distributor into abutting contact with an inlet nozzle extending through a wall of the pressure vessel.

Abstract: A fuel assembly is disclosed in which the nuclear fuel rods are supported by a grid-shaped bottom plate and a similar top plate, each of which is welded together from thin vertical metal strips, for example of a thickness of 0.6 mm, to define a grid of vertical channels (13, 14) intended for the fuel rods, each vertical channel being surrounded by eight adjacent channels only intended for coolant. (FIG. 2.

Abstract: A hollow, biological shield assembly capable of surrounding and insulating a nuclear reactor pressure vessel positioned therein. The shield assembly includes a metallic lining attached to a radially inner wall portion of a hollow concrete body, with a layer of thermally insulating material attached to the metallic lining and a plurality of vertical cooling channels also attached to the lining and mounted in recesses formed in the concrete body.

Abstract: A cartridge-type filter has easily exchangeable and safe distance handling filter cartridges contaminated with radiation-emitting contaminants. The filter includes a filter housing having an inner annular shoulder forming a valve seat, and a filter cartridge has an outer ring in sealing engagement with the shoulder for both supporting the cartridge and dividing the filter housing into two separate chambers respectively in communication with the supply and return conduits provided on the housing. A portion of the reactor cooling water is conducted continuously through the filter circuit which is parallel to the main water flow.

Abstract: A pressure seal for a rotating shaft (3) is disclosed in which a rubber sealing ring (9) is arranged in a trapezoidal slot (4), the sealing ring being made so thin at the slot opening as to prevent the rubber from creeping beyond the edges of the slot opening during prolonged periods when pressure is applied to engage the sealing ring with the shaft.

Abstract: A yoke-like attachment assembly for connecting a lifting hook with a lid portion of a nuclear reactor pressure vessel or the like, comprising a plurality of separate coupling assemblies extending parallel to each other between the lifting hook and lid, wherein each coupling assembly is capable of supporting the entire weight of the lid in the event of the failure of the remaining coupling assembly. Each coupling assembly includes a pair of spaced sheet-metal lugs, each mounted on a support plate assembly, with at least one bolt interconnecting the spaced lugs with the lifting hook positioned therebetween. Each support plate assembly is attached to a separate beam which, in turn, is attached to the lid.

Abstract: An apparatus is disclosed for heat treating metal sheet, comprising water-cooled cooling rolls (VII', VII"), a transportation channel (17) filled with protective gas, and a heating coil chamber (19) for a high-frequency coil (20,21).

Abstract: A method for providing a barrier against copper diffusion into a zirconium alloy tube which is lined with copper for the purpose of increasing the resistance of the tube to stress corrosion induced by fission products when the tube is used to fuel a nuclear reactor. The method involves the deposition of a copper lining on the zirconium alloy tube and the subsequent exposure of the lined tube to a substance such as steam, water, nickel oxide or carbon dioxide or another material which has the ability to oxidize the zirconium without oxidizing the copper. Thus, a zirconium oxide layer is developed between the zirconium alloy tube and the copper lining thereon.

Abstract: An arrangement for centering a tube includes guides on which are mounted blocks slidable towards and away from each other by a hydraulic cylinder arrangement. Each of the blocks has a frame pivoted on it to rock about an axis perpendicular to the direction of movement of the blocks, the turning movement of the frames on the blocks being limited by an adjustable set screw and a spring on opposite sides of the frame pivot. Each frame carries either two rollers turnable on spaced axes which are parallel to the length of the tube or a single roller mounted to turn on an axis perpendicular to the direction of movement of the blocks, this roller having a central portion of small diameter and end portions of greater diameter.