Abstract: The present invention, in one aspect, is a method for identifying an optimum core loading arrangement. The method generally has an initialization phase and a running, or search, phase. In the initialization phase, an initial core loading arrangement is identified based on the relative reactivity levels of the bundles to be loaded and the reactor core locations. Once the initial core loading arrangement is identified, such arrangement is then optimized, within the defined constraints, in the running phase. More specifically, in the running phase, each core location is analyzed to determine whether such core location reactivity level can be changed from the initial reactivity level to either satisfy a constraint or optimize cycle energy, or both.

Abstract: A nuclear reactor fuel assembly includes a fuel assembly base, a fuel assembly head and mutually parallel fuel rods containing nuclear fuel and extending between the fuel assembly head and the fuel assembly base. A water tube having first and second open ends extends parallel to the fuel rods. The first end of the water tube grips and is held at the fuel assembly base. An elongated extension body has first and second ends. The second end of the extension body grips and is held at the fuel assembly head. The second end of the water tube is screwed into the first end of the elongated extension body, or the first end of the elongated extension body is screwed into the second end of the water tube. The elongated extension body has two mutually coaxially disposed partial bodies. One of the partial bodies has the second end of the extension body and the other of the partial bodies has the first end of the extension body. One of the partial bodies is screwed into the other of the partial bodies.

Abstract: A source for boron neutron capture therapy (BNCT) comprises a body of photoneutron emitter that includes heavy water and is closely surrounded in heat-imparting relationship by target material; one or more electron linear accelerators for supplying electron radiation having energy of substantially 2 to 10 MeV and for impinging such radiation on the target material, whereby photoneutrons are produced and heat is absorbed from the target material by the body of photoneutron emitter. The heavy water is circulated through a cooling arrangement to remove heat. A tank, desirably cylindrical or spherical, contains the heavy water, and a desired number of the electron accelerators circumferentially surround the tank and the target material as preferably made up of thin plates of metallic tungsten.

Abstract: The control cluster has a spider constituted by a hub connectable to a drive shaft. Fins radiate from a bottom portion of the hub and provided with vertical fingers distributed in a regular array. It also includes rods provided with plugs that are releasably fixed to the fingers. The fins, their fingers, and at least the bottom portion of the hub constituting a single-piece part obtained by molding or by electro-machining.

Abstract: A process for the production of radiostrontium consists in that a target of metallic rubidium is bombarded by a flow of accelerating charged particles. The target of irradiated rubidium is melted, whereas the extraction of radiostrontium is carried out by sorption on the surface of a sorbing material immersed into the irradiated molten metallic rubidium. As the sorbing material, use is made of materials selected from the group consisting of heat-resistant metals or metallic oxides or silicon which are inert with respect to rubidium. The resultant radiostrontium is extracted from the irradiated rubidium. The temperature of the sorbing material is selected to be close to the optimum one for the sorption of radiostrontium which is within the range of from the melting point of metallic rubidium to 220.degree. C. And the temperature of molten rubidium is selected to be close to the optimum one for the desorption of radiostrontium within the range of from 220.degree. C. to 270.degree. C.

Abstract: A heavy ion generator is used with a plasma desorption mass spectrometer to provide an appropriate neutron flux in the direction of a fissionable material in order to desorb and ionize large molecules from the material for mass analysis.The heavy ion generator comprises a fissionable material having a high n,f reaction cross section. The heavy ion generator also comprises a pulsed neutron generator that is used to bombard the fissionable material with pulses of neutrons, thereby causing heavy ions to be emitted from the fissionable material. These heavy ions impinge on a material, thereby causing ions to desorb off that material. The ions desorbed off the material pass through a time-of-flight mass analyzer, wherein ions can be measured with masses greater than 25,000 amu.

Abstract: Iodine-125 is produced by neutron irradiation of .sup.124 Xe gas to form .sup.125 Xe and permitting decay of .sup.125 Xe to form .sup.125 I. Irradiation of the xenon-124 is effected in a first chamber within an enclosure and decay is effected in a second chamber within the enclosure and free from neutron flux. The apparatus is submersible in a nuclear reactor pool so as to absorb any radiation escaping the apparatus during the process. Xenon can be caused to move between the chambers remotely, underwater. The second chamber is removable from said enclosure and is transported to a suitable location to recover the .sup.125 I from its interior. Such recovery is effected by admitting an aqueous wash solution into the second chamber, whereupon it is heated, causing water from the wash solution to reflux and cleanse the interior surfaces of the second chamber, thus creating an aqueous solution of .sup.125 I, which then is caused to drain into a suitable container.

Abstract: A chimney which can be reconfigured or removed during refueling to allow vertical removal of the fuel assemblies. The chimney is designed to be collapsed or dismantled. Collapse or dismantlement of the chimney reduces the volume required for chimney storage during the refueling operation. Alternatively, the chimney has movable parts which allow reconfiguration of its structure. In a first configuration suitable for normal reactor operation, the chimney is radially constricted such that the chimney obstructs vertical removal of the fuel assemblies. In a second configuration suitable for refueling or maintenance of the fuel core, the parts of the chimney which obstruct access to the fuel assemblies are moved radially outward to positions whereat access to the fuel assemblies is not obstructed.

Abstract: A reactor core for a boiling water nuclear reactor includes a plurality of fuel assemblies (40) with a plurality of vertical fuel rods (10) and possibly occasional vertical water-filled rods or channels (32, 48, 49, 50, 51) which are surrounded by a fuel channel (1). Between the fuel assemblies (40) there are arranged water gaps (37a, 37b). At least one fuel assembly (40) has at least one outer, reduced corner portion (41) facing a gap (37a, 37bb), and the number of fuel rods (10) in each such fuel assembly (40) is reduced by a number corresponding to the number of reduced corner portions (41) therein.

Abstract: A sealing device comprising a supporting assembly (9) containing sealing members (16) supporting the instrument column (5), and an assembly (17, 18) for lifting the instrument column (5) in sealing engagement with the supporting members (16). The sealing members (16) supporting the instrument column (5) include a clamping ring (28) and at least one O-ring seal (29, 30). Axial movement of the instrument column (5) enables clamping of the inner seal (30) via the clamping ring (28). When axial movement of the instrument column (5) is restricted, the seals may be clamped by means of a suitably sized clamping ring (28).

Abstract: A reactor cavity flooding system, which is used to immerse the hemispherical lower head of a nuclear reactor vessel by flooding the reactor cavity, is connected to both coolant injection nozzles located at the annulus gap between the lower head and the thermal insulator of a reactor and the discharge loops which are used to drain the hot water of the annulus gap into either the cavity floor or a liquid eductor. The subcooled water at a fire protection system can be directly injected into the annulus gap through twenty-five (25) nozzles at the lowest, middle, and top injection headers by a pump. The hot water heated at the lower head will be drained into either the cavity floor and/or the liquid eductor via two discharge loops that consist of both a suction header in the annulus gap at the equator level of the lower head and four (4) leakage collectors at the outside of four (4) shear keys of a reactor vessel. Drainage and recirculation of the hot water can be achieved in two ways.

Abstract: An electrostatic containment fusion generator is comprised of a generally spherical capacitor having an outer plate at ground and a negatively charged inner plate. A reaction chamber, comprised of two pairs of spaced apart permanent magnets, is disposed within the inner plate. An ion source means provides a deuteron beam to enter into a figure-8 orbit between the two pairs of magnets. A Faraday cage exists between the two pairs which neutralizes space charge in the center region of the beam. An arced cut portion on each magnet assists in the beam's entry into the Faraday cage, while a path correction means corrects the effects of the inverse field created by the cut portion. Dual beam establishment means are also provided.

Abstract: Proportional counters for thermal neutron counting are described. In one embodiment, a proportional counter includes a lead wire, a coil spring and an anode wire. The coil spring includes two opposite ends and a substantially cylindrical opening extending between the two ends. The lead wire at least partially extends into the spring opening so that one end of the lead wire is within the spring opening. One end of the spring is secured to the lead wire, and the other end of the spring is secured to the anode wire.

Abstract: Each of the square top nozzles (26) of the fuel assemblies of the core includes four locating openings (40) in the vicinity of the vertices of the nozzle. The set of locating pins (35) of the upper core plate (32) includes four pins at each of the positions of fuel assemblies which are intended to be engaged in the four openings (40) of the top nozzle (26). The locating openings (40) of the nozzle may consist of the internal bores of sleeves (36) which are fixed on the nozzle in an axial arrangement and holds the spring leaves (38) of the nozzle. The locating openings may also be machined inside four bosses, projecting at the upper part of the assembly, and each arranged in one corner of the assembly.

Abstract: A control rod assembly for a nuclear reactor, wherein a plurality of absorber tubes are arranged and welded in a side-by-side array, the improvement wherein each absorber tube is formed with an elongated slot extending substantially the entire length of the absorber tube on one side of the tube, and with an elongated tab extending substantially the entire length of the absorber tube on a diametrically opposed side of the tube such that, for adjacent absorber tubes, a joint is formed wherein the tab of one tube is located within the slot of the other.

Abstract: A nuclear reactor fuel assembly has an elongate fuel assembly casing. A fuel assembly head which is located within an open end of this fuel assembly casing is connected through the use of a rigid connecting body to a fuel assembly foot located in the fuel assembly casing and can be lifted off out of the fuel assembly casing. An angled part bears on the outside against two sides of the fuel assembly casing which meet one another and is retained on the fuel assembly head through the use of a bolt. A rigid peg can be disposed on the angled part and can engage into a port in one of the two sides which meet one another. Such a rigid peg can also be disposed on one of the two sides of the fuel assembly casing and can engage into a pocket in the angled part.

Abstract: A heavy ion generator is used with a plasma desorption mass spectrometer to provide an appropriate neutron flux in the direction of a fissionable material in order to desorb and ionize large molecules from the material for mass analysis.The heavy ion generator comprises a fissionable material having a high n,f reaction cross section. The heavy ion generator also comprises a pulsed neutron generator that is used to bombard the fissionable material with pulses of neutrons, thereby causing heavy ions to be emitted from the fissionable material. These heavy ions impinge on a material, thereby causing ions to desorb off that material. The ions desorbed off the material pass through a time-of-flight mass analyzer, wherein ions can be measured with masses greater than 25,000 amu.

Abstract: The control cluster is usable for power regulation and for load following. It comprises a spider from which are suspended rods containing a column of neutron-absorbing material. The neutron-absorbing material in at least some rods is stainless steel in lower part of the rod and, in an upper part of the rod having a length equal to 20 and 40% of the height of the column of absorbing material, another material exhibiting an interference neutron absorption which is much higher than that of stainless steel, for instance Ag-In-Cd.

Abstract: End plugs for nuclear fuel rods are provided with a spot weld along the interior end face of the end plugs to seal any streamer openings or passages along the axis of the end plugs, thereby maintaining the fuel rods sealed at its opposite ends. The spot welds are applied by an automated laser welding system in which pallets of end plugs are supported on X-Y positioning tables below a laser movable in a vertical direction. By successively locating the end plugs in the pallet below the laser, the spot welds are formed along the axis of the end plugs and along the interior faces thereof sealing the end plugs.

Abstract: A fuel bundle for a nuclear reactor includes a plurality of fuel rods extending between upper and lower tie plates, and a filter plate seated on the lower tie plate. The filter plate includes a substantially planar plate having a plurality of fuel rod holes in a predetermined array, the plate having web areas between the fuel rod holes which are formed with a plurality of smaller debris filter holes. At least one of the web areas is formed to include a spring tab pivotable out of the plane of the plate so that in the event of debris overload, coolant can bypass the smaller debris filter holes.