Abstract: The lower tie plate grid includes cylindrical bosses and webs interconnecting the bosses for supporting nuclear fuel rods and defining flow channels through the grid for flowing coolant upwardly about the fuel rods. The grid includes shaped body members having flow openings, the members being disposed in each of the flow channels. In one form, the members define with the side walls of the bosses and webs a debris retention zone. In another form, sets of generally parallel, laterally spaced bars are disposed at discrete elevations in the flow channels. The bars are orthogonally related to one another whereby the effective debris catching area is defined by the openings through the crossed bars in plan, while the coolant flow area comprises essentially the space between each set of bars.

Abstract: A system for determining depth profiles of concentrations of hazardous elements in soils comprises a neutron source for generating neutrons of a first energy level and irradiating a volume of soil with the neutrons. Nuclear reactions are effected within the soil and gamma radiation is emitted from the soil. The system also includes an array of gamma detectors for detecting gamma radiation emitted from the soil; source electronics for controlling the width of regularly repeated pulses of neutrons generated by the neutron source; detector electronics associated with the gamma detectors for amplifying and digitalizing signals generated by the gamma detectors and storing data representing the digitalized signals; spectral analysis software for analyzing the data and determining the concentrations of selected target elements in the soil; and an acquisition interface module (AIM).

Abstract: A pellet carrier disc is movably held between two cooling blocks. The disc is vertically moved, setting its through hole into axial alignment with a first hole of the block. Deuterium gas is supplied into the through hole through the hole, and cooled and solidified, forming a deuterium cylinder. Then, the disc is moved, axially aligning the hole with a second hole of the block. A shaft is thrust into a first end of the deuterium cylinder through the hole, thereby forming a hole in the end of the cylinder. Next, the disc is moved, axially aligning the hole with a third hole of the block. Tritium gas is introduced into the hole of the cylinder through the hole, and cooled and solidified, forming a tritium core. Further, the disc is moved, axially aligning the hole with a fourth hole of the block. A shaft is moved through the hole, causing the second end portion of the deuterium cylinder to project from the hole. The second end portion of the cylinder is cut off.

Abstract: The process for containing a deuterium gas plasma discharge includes providing a cylindrical zone having a cylinder axis; supplying D.sub.

Abstract: A natural circulation boiling water reactor system comprises a reactor vessel enclosing a reactor core, for generating steam to drive a turbine which can drive a generator to generate electricity. The vessel includes a chimney for guiding the recirculating water and steam vertically above the core and a dryer for helping to remove water from steam exiting the vessel toward the turbine. In contrast to prior reactor systems, the chimney is height-staggered so that its central sections are taller than its peripheral sections. Likewise, a dryer is elevation-staggered. This staggering minimizes carryover, water in the steam flow to the turbine, and carryunder, steam in the water recirculating through the core. In addition, the staggered chimney causes the fastest recirculation flow through the hottest portions of the core. The overall effect is a more efficient reactor system.

Abstract: A partitioning device is provided which can be used in a pressurized water nuclear reactor. It occupies the space between the prismatic shaped core of the reactor, and a cylindrical casing and comprises vertical partitioning plates surrounding the core and reinforcement elements placed between the partitioning plates and the casing. It comprises panels distributed into horizontal rows in vertical columns, all the panels of the same row being identical and having vertical partitioning plates welded together and fast with criss-crossed horizontal and vertical reinforcements bearing on the casing and with vertical tubes. The stacked tubes of a same column form a post resting on a core support plate. Solid vertical keys connect the panels in the different columns together and to the casing.

Abstract: A thermoelectric material can be obtained by co-pulverizing and mixing a material containing at least bismuth and a material containing at least tellurium, without being alloyed by melting, and then molding and sintering. This thermoelectric material has high performance and can be utilized in a variety of fields such as thermoelectric power generation and thermoelectric cooling, a temperature sensor, space development, marine development, and electric power generation in the remote areas. Since metal elements are used as a starting material, the starting material can be easily prepared. Moreover, in the production steps, the thermoelectric material can be produced in a high yield at a low energy consumption level by a simplified manner, without a complicated operation or special apparatus, and its production cost can be decreased.

Abstract: A spent fuel rack for storing fresh fuel assemblies, or spent fuel assemblies removed from a nuclear reactor, which includes a base plate having multiple cells of modular construction welded at their bottom ends to the plate. The cells are formed of L-shaped sections having walls which support neutron absorbing material, and the walls of one cell are common to the adjacent cells. The base plate includes openings primarily for receiving the bottom nozzle of a fuel assembly, but they further serve as access openings for apparatus used for leveling the base plate. There is also means for receiving and locking the engaging mechanism of lifting apparatus which means is wholly within the periphery of the base plate.

Abstract: A flux trap neutron absorber arrangement for use in a fuel storage body between a pair of fuel storage cans which receive and store nuclear fuel assemblies includes separate pockets spaced from one another and extending vertically along and attached to the exterior of each of the adjacent side walls of adjacent spaced storage cans, an elongated flat plate of a thermal neutron absorber material mounted in each pocket, the plates of thermal neutron absorber material being likewise spaced from one another and defining a fast neutron slow-down region therebetween, a slab of a metal hydride disposed in the fast neutron slow-down region between the plates of thermal neutron absorber material and the separate pockets on the adjacent side walls, a canister containing the slab of the metal hydride being disposed in the fast neutron slow-down region, the canister being connected to at least one of the adjacent side walls of the adjacent storage cans.

Abstract: A boiling water reactor has a control element disposed in a water pond. An apparatus for the neutron-radiography testing of the control element includes a film cassette having a recording area. A water-free hood is fitted over the control element. The hood has an open bottom and a wall facing the film cassette. The wall has an opening formed therein with a cross section corresponding to the recording area. A holding device fits over the opening for receiving the film cassette. The holding device has a downwardly open side extended below the opening through which the film cassette is to be introduced into the water-free space in the holding device. A neutron source, a collimator and the film cassette lie in one measurement plane.

Abstract: In a nuclear reactor wherein a plurality of neutron detectors are arranged vertically and at equal azimuth angles around a core of the nuclear reactor, thereby to measure a vertical power profile with a core of the reactor core, the improvement comprising dividing the core into sectors at respective azimuth angles confronting the neutron detectors, usingg the output signal of the partial detectors included in each of the neutron detectors for measuring a vertical reactor power profile of the azimuthal sector of the core confronting the corresponding neutron detector, and averaging the vertical profiles of the respective azimuthal parts with respect to the azimuth angles to measure the vertical reactor power profile of the reactor.

Abstract: For each of the demountable fuel rods (23), the end part of the protective tube (27), which end part is open towards the exterior, has a reduced diameter over a certain length and comprises at least one seating which does or does not pass through its wall. The end part of the fuel rod (23) is integral with a ferrule (34) which is coaxial with the fuel rod and which surrounds the assembly rod (31) of the fuel rod over part of its length. The ferrule (34) is engaged on the reduced-diameter part of the protective tube (27) when the rod (31) is screwed into the bore (28) of the protective tube. Locking against rotation of the fuel rod in the protective tube (27) is ensured by deformation of the ferrule (34) within the openings of the end part of the protective tube (27). The fuel rod is demounted by exerting a torque on it by way of an engagement surface (37), for example of prismatic form, located near the end of the fuel rod.

Abstract: The rotary dipole active magnetic regenerative refrigerator (10) of the present invention comprises a stationary first regenerative magnetic bed (12) positioned within a stationary first inner dipole magnet (14), a stationary second regenerative magnetic material bed (16) positioned within a stationary second inner dipole magnet (18), an outer dipole magnet (20) that rotates on a longitudinal axis and encloses the inner dipole magnets (14, 18), a cold heat exchanger (22), hot heat exchangers (24, 26), a fluid displacer (28), and connective plumbing through which a heat transfer fluid is conveyed.

Abstract: A natural circulation boiling water reactor system comprises a reactor vessel enclosing a reactor core, for generating steam to drive a turbine which can drive a generator to generate electricity. The vessel includes a chimney for guiding the recirculating water and steam vertically above the core and a dryer for helping to remove water from steam exiting the vessel toward the turbine. In contrast to prior reactor systems, the chimney is height-staggered so that its central sections are taller than its peripheral sections. Likewise, a dryer is elevation-staggered. This staggering minimizes carryover, water in the steam flow to the turbine, and carryunder, steam in the water recirculating through the core. In addition, the staggered chimney causes the fastest recirculation flow through the hottest portions of the core. The overall effect is a more efficient reactor system.

Abstract: A natural circulation boiling water reactor system using free-surface steam separation incorporates a series of tubes near the inner wall of its reaction vessel extending from a downcomer to well-above the downcomer. These tubes allow steam bubbles which would otherwise be trapped within the downcomer to escape from the recirculating water toward the steam exit of the vessel. This lowers the volume of steam in the downcomer, lowering the water velocity required to maintain a given volume of water recirculation. The reduced water velocity results in less carryunder which results in smaller voids in the reactor core. The smaller voids provide longer fuel burnups and enhance reactor stability.

Abstract: In the field of commercial nuclear reactors, there is an increasing demand for long-life control blades in order to meet the requirements of higher economy and reduction in the disposal of radioactive wastes. A control blade proposed by the invention stands a long use by virtue of the use of a long-life neutron absorber which is typically made of hafnium. Despite the use of hafnium which has a large specific weight (13.3 g/cm.sup.3), the size, shape and weight of the control blade are substantially the same as those of conventional control blades which employ boron carbides B.sub.4 C as the neutron absorber, so that the control blade can be back-fitted in existing boiling water reactors without difficulty.

Abstract: A solid state stripper for stripping H.sup.- to H.sup.O is provided that includes a very thin solid state material such as polyvinylidene chloride, mica, and cellophane that is moved at a predetermined speed in front of an accelerated beam of negative ions to cause the negative ions to be stripped to form neutral ions as they pass through the solid state stripper material.

Abstract: A reconstitutable control assembly has a spider structure which supports control rods by detachable attachment joints. Each attachment joint includes a hollow connecting finger on the spider structure and an elongated detachable split upper end plug on each control rod. The split upper end plug includes a pair of separate upper and lower plug portions. The upper plug portion has upper, middle and lower sections, whereas the lower plug portion has upper, middle and lower segments. The upper section of the upper plug portion is rigidly attached to the connecting finger on the spider structure, whereas the lower segment of the lower plug portion is rigidly connected to the control rod. Also, the lower section of the upper plug portion and the middle segment of the lower plug portion have complementary threads defined thereon for rigidly threadably attaching the upper and lower plug portions to one another.

Abstract: A method and apparatus for improving the performance of a thermal breeder reactor having regions of higher than average moderator concentration are disclosed. The fuel modules of the reactor core contain at least two different types of fuel elements, a high enrichment fuel element and a low enrichment fuel element. The two types of fuel elements are arranged in the fuel module with the low enrichment fuel elements located between the high moderator regions and the high enrichment fuel elements. Preferably, shim rods made of a fertile material are provided in selective regions for controlling the reactivity of the reactor by movement of the shim rods into and out of the reactor core. The moderation of neutrons adjacent the high enrichment fuel elements is preferably minimized as by reducing the spacing of the high enrichment fuel elements and/or using a moderator having a reduced moderating effect.

Abstract: The invention relates to a nuclear reactor with improved efficiency.The nuclear reactor comprises a massive partition (18) of material reflecting high energy neutrons at the circumference of the core (7) of the reactor, two layers (19 and 20) of material absorbing low energy neutrons and containing fertile material arranged one at the lower part and one at the upper part of the core (7) and an assembly of neutron energy spectrum variation rods (27). The rods (27) are associated with mechanisms permitting them to be either fully inserted into the core (7), or fully extracted. These rods (27) consist of a material absorbing low energy neutrons and permit a shift of the neutron spectrum towards the high energies.The invention is particularly applicable to pressurized water nuclear reactors.