Abstract: A nuclear fuel assembly has mechanical elements which constrain the flux thimble tube within the instrumentation tube to maintain physical contact with the interior surface of the instrumentation tube at a plurality of points staggered on a single-diametral plane and spaced substantially throughout the length of the instrumentation tube. The staggered mechanical elements induce a controlled elastic sinuous deflection of the inner thimble tube. The mechanical elements can take several different forms, for example, dimples or cantilevered spring fingers formed in the wall of the instrumentation tube and projecting radially inwardly therefrom.

Abstract: A fuel assembly has a top nozzle with improved clamps for retaining hold-down spring assemblies. Each clamp includes a clamp block formed integral with a flange of the top nozzle at each of a pair of diagonal corners thereof. Each clamp block has a pair of interconnected clamp slots formed therein. Each clamp slot is formed in the clamp block with interconnected openings at the front and outer side thereof. The front and outer side openings permit sideways insertion of the hold-down spring assembly at a base end thereof to position the spring assembly for attachment to the top nozzle. The clamp slot also provides a flat bottom surface in the clamp block for clamping the hold-down spring assembly.

Abstract: A device for searching and retrieving objects on a tube sheet of a steam generator which includes a sled having a probe and a gripper thereon and connected to a flexible tube having control means therein for operating the probe and the gripper whereby the sled and flexible tube may be inserted through a handhole of the generator to an operating position on the tube sheet. Both the probe and the gripper may be angularly rotated to manipulate them between the tubes of the steam generator.

Abstract: A retaining assembly holds a nozzle seal in the nozzle of a nuclear steam generator vessel. The assembly includes two arcuate beams generally following the curvature of the vessel wall, one beam lying generally alongside the divider plate and the other extending diametrically across the nozzle seal and being coupled thereto. The outer ends of the beams are anchored to the outer edge of the tube sheet and have brace members which bear against the vessel wall. The inner walls of the beams are interconnected by a thrust assembly which bears against the divider plate and includes an adjustable jacking screw means for urging the beams against the tube sheet. The effective length of the beam coupled to the nozzle seal can be varied by selectively replaceable spacers.

Abstract: A debris trap is mounted within a bottom nozzle of a fuel assembly so as to capture and retain debris carried by coolant flowing from the lower core plate openings of the nuclear reactor to the fuel assembly. The trap includes a hollow enclosure disposed below the bottom nozzle adapter plate and between the corner legs thereof. The enclosure is composed of upper and lower walls and inwardly inclined side walls which space apart the upper and lower walls and interconnect their peripheries so as to form a debris capturing and retaining chamber within the hollow enclosure. The walls are composed of a material, such as wire mesh screen and/or perforated plate, which is permeable to liquid coolant but impermeable to debris. Openings are defined in the bottom wall of the enclosure aligned with the flow openings of the core plate. Two embodiments of features are provided for capturing debris and diffusing coolant flow within and through the trap.

Abstract: A grid cell spring force measuring apparatus includes a pair of elongated bars being pivotally connected together at their respective mid-sections and having a set screw for presetting the displacement between the lower end portions of the bars and a rotatable shaft with a knob for applying a separation force to the upper end portions of the bars. When the displacement of the bars and thereby their cross sectional dimension is preset and the bars have been inserted into a grid cell, the shaft is rotated using the knob and the upper end portions of the bars are gradually forced apart. Once the force being applied at the upper end portions and transmitted to the lower end portions of the bars overcomes the spring force, the spring deflects and the bars separate enough to open electrical contacts mounted on the bars. At the instance the contacts are opened, a readout connected to a strain gauge fixed on one of the bars records the level of force being imposed by the bar on the cell spring.

Abstract: A fuel rod support grid includes interleaved straps arranged to form a matrix of hollow cells. Each cell receives one fuel rod and is defined by pairs of opposing elongated walls which are shared with adjacent cells. Each wall of the pairs thereof forming a single cell has one side which is a part of the perimeter of the single cell and has an opposite side which is part of the perimeter of one of several cells disposed about and adjacent to the single cell. The improvements incorporated by the support grid comprise a first set of dimples formed at an upper end of each wall of the pairs thereof defining each cell of the grid and a second set of dimples formed at a lower end of each grid cell wall.

Abstract: An inlet flow distributor comprising multiple chambers and a flow splitter which can be freely inserted through the feedwater inlet nozzle and assembled and attached to the nozzle in such a manner that each chamber receives a portion of the influent feedwater and distributes it at controlled peak velocities and in a predetermined pattern to the shell through a pair of perforated plates having offset perforations in order to reduce vibration of tubes adjacent thereto.

Abstract: A horizontal baffle disposed in the annulus defined between the core barrel and the thermal liner of a nuclear reactor thereby physically separating the outlet region of the core from the annular area below the horizontal baffle. The horizontal baffle prevents hot coolant that has passed through the reactor core from thermally damaging apparatus located in the annulus below the horizontal baffle by utilizing the thermally induced bowing of the horizontal baffle to enhance sealing while accommodating lateral motion of the baffle base plate.

Abstract: A removable radial shielding assembly for use in the periphery of the core of a liquid-metal-cooled fast-breeder reactor, for closing interassembly gaps in the reactor core assembly load plane prior to reactor criticality and power operation to prevent positive reactivity insertion. The assembly has a lower nozzle portion for inserting into the core support and a flexible heat-sensitive bimetallic central spine surrounded by blocks of shielding material. At refueling temperature and below the spine is relaxed and in a vertical position so that the tolerances permitted by the interassembly gaps allow removal and replacement of the various reactor core assemblies.

Abstract: A liquid-metal-cooled fast-breeder reactor includes a bridge structure for separating hot outlet coolant from relatively cool inlet coolant consisting of an annular stainless steel baffle plate extending between the core barrel surrounding the core and the thermal liner associated with the reactor vessel and resting on ledges thereon, there being inner and outer circumferential webs on the lower surface of the baffle plate and radial webs extending between the circumferential webs, a stainless steel insulating plate completely covering the upper surface of the baffle plate and flex seals between the baffle plate and the ledges on which the baffle plate rests to prevent coolant from washing through the gaps therebetween. The baffle plate is keyed to the core barrel for movement therewith and floating with respect to the thermal liner and reactor vessel.